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An integrated opto-mechatronic system for self-calibration of accelerometer in large dynamic range
Sensors and Actuators A 300 (2019) 111612
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Sensors and Actuators A: Physical journal homepage: www.elsevier.com/locate/sna
An integrated opto-mechatronic system for self-calibration of accelerometer in large dynamic range Yu Chen a,b , Xiangyu Sun a,b,∗ , Long Zhang a,b , Yicheng Wang a,b,∗ , Xiaoshi Li a,b , Dongdong Gong a,b , Tianyu Yang a,b , Feng Qin a,b a b
Microsystem & Terahertz Research Center, ChinaAcademy of Engineering Physics, Chengdu, China Institute of Electronic Engineering, China Academy of Engineering Physics, Mianyang, China
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Article history: Received 26 April 2019 Received in revised form 10 September 2019 Accepted 10 September 2019 Available online 14 September 2019 Keywords: Integrated opto-mechatronic system Accelerometer self-calibration Piezoelectric microvibrator Optical sensing system
a b s t r a c t Long-term instability and scale factor drift are inherent problems in micro inertial measurement units (MIMU) such as accelerometers. This research achieves a novel integrated opto-mechatronic system of less than 1.6 cm3 , containing an advanced six degree-of-freedom (DOF) piezoelectric microvibrator, a commercial micro-accelerometer and an optical displacement sensing system. In the integrated opto-mechatronic system, the piezoelectric microvibrator is the source of standard acceleration for selfcalibration. It is capable of providing an acceleration of up to 30 g and an angular velocity of 1100◦ /s. The optical sensing system is applied to detect the real-time acceleration of the microvibrator to provide detection data for self-calibration. Moreover, the optical sensing system also self-detects and self-adjusts the output acceleration of the microvibrator. The external control and processing unit calculates the error coefficient of the accelerometer to obtain the compensation model to achieve self-calibration, according to the acceleration detected from the optical sensing system and the acceleration output from the accelerometer. The experimental results show that the output accuracy of the micro accelerometer is significantly improved after a complete self-calibration process from 0 to 24 g acceleration range. © 2019 Published by Elsevier B.V.
1. Introduction The micro inertial measurement unit (MIMU) has a wide range of applications in inertial navigation, attitude estimation and position recognition by providing inertial information with multiple degrees of freedom [1,2]. Therefore, it is widely used in aerospace, biomedical and functional electronic devices. Currently, the operational accuracy of the micro inertial sensor is close to that of the macro inertial sensors. However, inherent problems such as drift of scale factor and long-term instability limit the output accuracy and the potential of MIMU in high-precision strategy and navigation applications [3,4]. In order to compensate for drift, the calibration of the MIMU becomes critical. Usually, the calibration is conducted using macro calibration system with a macro shaker and laser Doppler vibrometer. However, the calibration validity period based on the traditional calibration method is short. In addition, it requires the
∗ Corresponding author: Microsystem & Terahertz Research Center, China Academy of Engineering Physics, Chengdu, China. E-mail addresses: [email protected] (X. Sun), [email protected] (Y. Wang). https://doi.org/10.1016/j.sna.2019.111612 0924-4247/© 2019 Published by Elsevier B.V.
support of external equipment [5–7]. Most critically, traditional calibration methods cannot achieve independent self-calibration for the MIMU in any scene. With the development of MEMS processes, the application of embedded internal or integrated microstructures to self-calibrate microsensors before operation to compensate for long-term drift errors can fundamentally reduce long-term dependence. Moreover, the MIMU integrated self-calibration system has higher stability and greatly expands the application of MEMS inertial sensors [8–11]. The MEMS micro actuator acts as an integrated microstructure to provide standard acceleration for the MIMU. The independent self-calibration of MIMU places high demands of high precision, adjustable range and wide range output to the micro actuator [12–15]. Piezoelectric micro actuators are widely used in the field of micromechanical operation due to their low driving voltage, fast response and precise control capability [16–19]. Therefore, applying the piezoelectric micro actuator as a source of acceleration and angular velocity makes it possible to the self-calibration of the MIMU to be integrated into a whole system [20–22]. In order to simplify the calibration process and realize the selfcalibration of accelerometer, this paper proposes an integrated opto-mechatronic system consisting of a piezoelectric microvibra-
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Fig. 1. Graphical overview of the integrated opto-mechatronic system for selfcalibration.
tor, an optical displacement sensing system and an accelerometer. The high dynamic piezoelectric microvibrator provides an acceleration within 30 g and an angular velocity within 1100◦ /s. An optical sensing system consisting of a vertical cavity surface emitting laser (VCSEL) and 8 photodiodes (PDs) are used to detect the vibration information of microvibrator. Through micro mechanical structure stacking technology and optical cavity integration technology, the piezoelectric microvibrator, the commercial micro accelerometer and the optical displacement sensing system are integrated into chip-level integrated opto-mechanical systems. The closed loop control process is performed based on optical sensing system so that the microvibrator operates at a steady standard acceleration. The error compensation model is built to achieve self-calibration for the accelerometer based on the standard acceleration and the actual output acceleration. 2. Design and methods The integrated opto-mechatronic system consists of a 6 DOF microvibrator, a large dynamic range accelerometer, and an optical displacement sensing system, forming a chip-level packaging by a three-dimensional heterogeneous integration method, as shown in Fig. 1. Among them, the microvibrator acts as source of acceleration and angular velocity, providing the required acceleration and angular velocity in different directions for self-calibration. The accelerometer is the unit to be detected and calibrated, which is electrically connected to the microvibrator. The optical sensing system is composed of a VCSEL and 8 PDs which detects the output acceleration of the microvibrator and implements self-calibration of the accelerometer through feedback control. The 6 DOF microvibrator based on PZT thin film is the most important component in the self-calibration system. The operation principle of the microvibrator is actually built on a forced vibration system with damping [23]. As shown in Fig. 2(a), a 3 mm * 3 mm suspended center table is supported by four well-designed folded beams at the corners. The structural design of the folded beams is based on the vibration of a typical single-ended fixed-support cantilever beam in the d31 mode. It makes the microvibrator keep a large elasticity coefficient and a suitable system stiffness to complete the motion at various degrees of freedom. Eight separate electrodes are deposited on each beam to achieve independent control of eight beams. By independently driving the corresponding beams of the microvibrator, a 6 DOF vibration mode of the center table can be achieved. Fig. 2(b) exhibits the motions of 6 DOF achieved by the four vibration modes of the microvibrator, which are translation and rotation along the x/y/z axis, respectively. The microvibrator is designed to achieve an acceleration of 30 g in the
z-axis direction, and an out-of-plane angular speed above 1000◦ /s [24]. The microvibrator is fabricated using wafer-level micromachining technology. The fabricated process is shown in Fig. 3(a). A standard 25 m top silicon SOI wafer is used to grow 5 m PZT and 200 nm Pt as the upper and lower electrodes. The PZT upper electrode is then patterned as the driving electrodes of the folding beams. After the PZT is wet etched and the top silicon is dry etched, the structure of beams has appeared. Subsequently, a layer of silicon dioxide is deposited as an isolation layer to isolate the driving electrodes for folded beam. The second layer of metal Pt is then grown on the silicon dioxide layer as for the control routes for the folding beams and signal routes for the accelerometer. Finally, the SOI bottom silicon is etched by DRIE to form the microvibrator suspended structure. The finished microvibrator and the details are shown in Fig. 3(b). The accelerometer of MPU-6500 from Invensense with a small 3 × 3 x 0.9 mm Quad Flat No-lead (QFN) package and acceleration up to ±16 g is accurately placed on the center table of the microvibrator. Due to the challenge to the packaging technology from the weak structure of the microvibrator, a positioning limit fixture is placed under the cavity structure of the microvibrator to prevent the center table from being broken due to excessive deformation. In addition, the positioning limit fixture also acts as a height limiter for the microvibrator during operation, achieving protection against large vibrations of the microvibrator. The pads of the accelerometer are electrical connected with the metal pads on the microvibrator by the micro mechanical structure lamination technique, as shown in Fig. 4. The technology takes laser alignment and microlevel mechanical operation to achieve accurate stacking of multiple mechanical structures. In order to ensure the accuracy of the stacking, the position data of the microvibrator and the accelerometer are obtained according to calculation, experiment and compensation. Subsequently, the tools for the alignment is designed to meet the requirements of precise alignment. This technology solves the problem of sensitive structure protection and alignment at the integration between micro mechanical structures of microvibrator and accelerometer chip. In addition, the low temperature bonding method is used in the stacking, so that the microvibrator and the accelerometer are bonded at a low temperature of less than 160 ◦ C, which reduces the residual stress introduced into the integrated package. The optical displacement sensing method has the advantages of simple architecture and implementation, high sensitivity, and low dependency on wavelength stability of the light source [25]. As shown in Fig. 5, the non-contact optical displacement sensing system consists of a VCSEL and 8 PDs for the detection of the motion state of the microvibrator [26–28]. As the vibration displacement of the microvibrator changes, the intensity of the light received by the PD changes. Through the signal processing circuit, the change of the received light intensity of the PD is converted into a change of the voltage signal. The magnitude of the PD output voltage represents the displacement of the microvibrator. In order to reduce the error from single PD, eight PDs in the inner ring and the outer ring are designed to obtain the change in the displacement of the microvibrator. In the same way, by obtaining the strength of the two PD output voltages on the same coordinate axis of the inner ring or the outer ring, the angular displacement information of the microvibrator can be obtained by using the different sum ratio. The optical sensing system is located at an appropriate distance above the accelerometer with an air gap of approximately 1 mm as an optical cavity. The schematic of the optical sensing system and the fabricated device are also shown in Fig. 5. Due to the detecting accuracy of micron-level vibration, concentric circle high precision patches for the 8 PD chips are required with the relative accuracy
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Fig. 2. The piezoelectric microvibrator. (a) The structure of microvibrator with suspended center. (b) The vibration mode of six-degree-of-freedom.
Fig. 3. (a) The fabricated process of the microvibrator. (b)The microvibrator with details after fabrication.
requirement between PDs less than +/- 1 m. A high-precision optical patch device is conducted to patch the optical displacement sensing system. Multiple alignment marks are set on the patch substrate and the dummy patch is used for the analog patch. The position data is compensated according to the calculation result
until the demand is required. The optical sensing system provides a detection resolution higher than 150 nm. A reflector is fixed on the top surface of the accelerometer. The relative motion between the reflector and the optical detector affects the intensity distribution of the reflected lights. Different PDs simultaneously extract
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Fig. 4. Micro mechanical structure stacking technology for the integration of microvibrator subsystem.
Fig. 5. Schematic and real graph of the optical displacement sensing system.
the reflected lights to obtain micro-displacement and micro-angle changes. The optical cavity integration technology provides a feasible technical approach to integrate optoelectronic functions in MEMS, which can be used for high-precision dynamic detection of micro mechanical structures. Aiming at the problem of reflected light interference in non-contact detection in optical displacement sensing system, the innovative two-piece package carrier structure design. The selective optical path in different vibration is realized by the well-designed sunshade sheet and reflective sheet on the glass cover. After molding of the peripheral closed cavity structure, a stable optical cavity structure is formed in the package structure to eliminate the interference of VCSEL emission light and reflected light. In the three-dimensional integration for the device, the fabricated bottom substrate and the cavity support structure are designed and processed to integrally assemble the positioning limit fixture, microvibrator with accelerometer, and the optical sensing system into a whole module. In the packaging process, first, the fabrication of the electrode pad has been completed on the bottom substrate of the chip. Then, the positioning limit fixture is fixed on the fabricated bottom substrate, while the MEMS microvibrator is high-accurately stacked on the positioning fixture. The accelerometer with an aluminum-plated silicon reflective mirror is integrated onto the microvibrator. Subsequently, the optical displacement sensing system is integrated with the microvibrator and accelerometer by the means of an inverted package. In placing the
patch, the image recognition technology is applied to identify the pattern of the bottom pad of the accelerometer and the metal pattern. With the help of the visual recognition data and real-time positioning, the accelerometer is accurately placed on the microvibrator. The alignment tolerance is within ±20 m. The upper substrate of optical sensing system is optically electrical connected with the package by adding a three-dimensional interconnected metal pins to the sidewall of the package. This method is combined with the microvibrator double-layer metal wiring design method to realize the accelerometer multi-port and ¨ ¨ microvibrator multi-port flip-chip electrical signal interconnection. When the three-dimensional stacking of the respective components is completed, the top substrate on which the peripheral circuits have been integrated is covered on the cavity supporting structure. An external metal lead is then applied to electrically interconnect the top optical system to the bottom substrate. Finally, the designed wall casing combined with the sealing process of design development and processing is assembled into a threedimensional closed mechanical structure. Micro mechanical structure stacking technology and optical cavity integration technology together constitute optical and electromechanical three-dimensional integrated interconnection technology. This technology can be applied to multi-chip integrated multi-function module internal interconnection. The completed chip-level fully packaged integrated opto-mechatronic system is shown in Fig. 6. The size of the chip is 15 mm * 15 mm * 6.8 mm, including a complete six-degree-of-freedom microvibrator, an
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Fig. 6. The completely fabricated chip-level, fully packaged integrated opto-mechanical system.
Fig. 7. The self-calibration workflow of the integrated opto-mechatronics system.
integrated large dynamic range accelerometer and the optical displacement sensing system. The integrated opto-mechatronics system has enabled in-situ self-calibration of the accelerometer in any occasions without the need for external equipment.
3. Experimental results The self-calibration workflow of the integrated optomechatronics system is shown in Fig. 7. When self-calibration begins, the control and processing unit provides the required excitation for the vibration mode to driving the microvibrator. And based on the real-time data provided by optical detection, the vibration table can be stably and accurately operated at the required acceleration point through closed-loop control. Since the microvibrator and the accelerometer are bonded together, the output acceleration of the microvibrator is exactly the actual acceleration of the accelerometer. After the microvibrator stabi-
lizes the vibration, the control unit reads the acceleration value (read value) obtained by the accelerometer. The control unit establishes the error model through the calibration algorithm and then iterates. After calibration of the complete dynamic range, the system completes the self-calibration for the accelerometer. The microvibrator works at resonance conditions. The AC driving signals are provided separately for each of the top excitation electrodes with different input modes to drive the desired multidegree of freedom motion. In order to independently evaluate the performances of the microvibrator, the tests are performed by an external laser Doppler vibrometer (LDV). The output acceleration and angular velocity of the micro\vibrator are shown in Fig. 8. It can be seen that the microvibrator can provide an acceleration of up to 30 g and an angular velocity of 1100◦ /s, covering the entire measurement range of the accelerometer. In addition, both the acceleration and angular velocity of the microvibrator can be operated in regions with good linearity. Thus, the dynamic output of
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Fig. 8. The acceleration and angular velocity of the microvibrator output with the excitation voltage.
the microvibrator can be adjusted by simply regulating the magnitude of the excitation voltage. This enables reliable operation and fast response of the output acceleration adjustment. Since the realtime vibration state of the vibrating table can be obtained by optical inspection, the control unit can precisely adjust the acceleration and angular velocity of the microvibrator to any desired value by the linear relationship of voltage-acceleration of the microvibrator. The custom optical displacement sensing system is used to detect the precise motion of the microvibrator, including displacement (acceleration) and rotation angle (angular velocity). The actual motion state obtained is used as an input for the error model and closed loop control. In order to evaluate the performance of the optical sensing system, the microvibrator with the accelerometer plays as the vibration source, and the LDV is taken again as an external standard. The test shows that the optical detection range can reach 50 m for the mode in which the micro-vibrator moves along Z-axis. In the mode of tilting motion, the detection angle can reach 0.6◦ . In order to verify the measurement performance and resolution of the optical sensing system, the microvibrator is controlled to generate dynamic vibration with an amplitude of 150 nm for the detection by the optical sensing system. Fig. 9(a) shows the raw measurements from the optical sensing system which shows a good difference between each step. It exhibits that the integrated optical sensing system is capable of accurately detecting the real-time vibration state of the microvibrator. To evaluate the dynamic response of the optical sensing system, the control and processing unit simultaneously receives dynamic acceleration from the accelerometer (read value) and the optical sensing system (measured value). The dynamic test results are calibrated by the quasi-static test results. The measurement
Fig. 9. (a) The measurement of the optical sensing systems to different external accelerations. (b) Real-time comparison of the measurement results of the optical sensing system with the reading results of the accelerometer.
results obtained by LDVs, which reveals that the OBDM detector could reflect the full cycle of vibration, as shown in Fig. 9(b). From Fig. 9(b), on the one hand, it can be seen that the frequency and amplitude responses in the acceleration dynamic curve are high stable in the time domain, indicating the stable output capability of the microvibrator. On the other hand, the dynamic acceleration curves from accelerometers (read values) and optical sensing systems (measured values) are highly overlapping in frequency and phase. This reveals a good consistency between the optical sensing system detection and the accelerometer output. While the difference in amplitude of the acceleration just reflects the error between the accelerometer output and the actual acceleration. The preliminary results indicate that a resolution of 150 nm is obtained. In the present experiment results, the resolution is limited by the circuit noise and the error sources introduced by the testing system. The above two problems can be solved through the optimization of testing system and low-noise circuit, such as smoothing filtering algorithm or low noise amplifier (LNA), and better resolution of 6 nm is expected. The integrated opto-mechatronic system is verified to be capable of performing self-calibration for the accelerometer by the independent testing of the dynamic performance of the microvibrator and the detection capabilities of the optical sensing system. After withdrawing the external test equipment, the self-calibrated of the integrated system is conducted according to the expected self-calibration mode in Fig. 7. The self-calibration of the accelerometer through the integrated opto-mechatronic sys-
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4. Conclusions
Fig. 10. Self-calibration for the accelerometer by the integrated opto-mechanical system.
Table 1 The total current noise of the signal processing circuit. Type of noise
Noise Amplitude
Thermal noise of amplifying circuit Current noise of Amplifier circuit Current noise of Photodiodes Current noise of first stage filter circuit Current noise of second stage filter circuit
9 pA 1.62 pA (LTC1050C) 1.8 pA 20.425 pA (AD8620BRZ) 20.425 pA (AD8620BRZ)
*The total current noise at the input port of the signal processing circuit is the root mean square of the sum of the squares of all noises.
tem is shown in Fig. 10. The acceleration is tested at 200 Hz, which exceeds the normal operating range of the accelerometer. Thus the error of the accelerometer increases significantly. It is clear that before self-calibration, the error of the acceleration increases as the acceleration increases. The read value of the accelerometer has a deviation of nearly 35% at 15 g compared to the standard acceleration. After self-calibration by the integrated opto-mechatronic system, the output read value of the accelerometer has been evidently calibrated. The maximum error of acceleration is no more than 1.5%. The system noise mainly comes from two aspects. The first aspect is the sensing noise, including the internal resistance thermal noise of the PD, the dark current shot current noise, and the mirror current shot current noise. With the help of the optical sensor structure design, the PD noise is effectively reduced to 1.8 pA, where the noise of PD dark current is 0.1 nA at the signal bandwidth of 5 kHz. The second aspect is the noise generated by the signal processing circuit in the control and processing unit, mainly including the thermal noise of the amplifying circuit, the current noise of the circuit, and the voltage noise. Based on the theoretical calculation method of noise signal, the total current noise at the input port of the signal processing circuit is calculated to be about 30.33 pA. The detailed overall noise signals in this system are listed in Table 1. The power consumption of the integrated opto-mechatronic system is mainly from the signal processing circuit. The accelerometer consumes 990 W in standard operating mode. The maximum power consumption of the VCSEL is 12.6 mW. The PDs absorbs and reflects the energy from external laser. Thus, PDs have no power consumption in principle. If calculating the power consumption of PDs from output signal current, the maximum power consumption of 10 PDs is 30 W. The power consumption of the detection and signal processing circuit is mainly from the chopper-stabilized operational amplifier which maximum power consumption is 2500 mW.
This article presents an integrated opto-mechatronic system that includes a piezoelectric microvibrator, a commercial micro-accelerometer and an optical displacement sensing system. The system is designed to independently self-calibrate its internal accelerometer. PZT-based piezoelectric microvibrator manufactured by full micro-machining technology can achieve 6-degree-of-freedom vibration and provide a reliable vibration source for self-calibration. Through the micro mechanical structure lamination technology, the accelerometer and the microvibrator are low-temperature bonded under the microvibrator double-layer wiring design, with the achievement of the accelerometer signal electrical connection. The optical displacement sensing system with VCSEL and PDs realizes chip-level packaging of each component through optical and electromechanical three-dimensional integrated interconnection technology. Experimental results show that the microvibrator is capable of providing an acceleration of up to 30 g and an angular velocity of 1100◦ / s. The optical sensing system can measure a vertical displacement of 50 m and a tilting angle of 0.6◦ . In the self-calibration operation, the optical sensing system detects the real-time acceleration from the microvibrator, and control unit reads the output acceleration from the accelerometer. After self-calibration by the integrated optomechatronic system, the accelerometer error is less than 1.5%. References [1] J. Wendel, O. Meister, C. Schlaile, et al., An integrated GPS/MEMS-IMU navigation system for an autonomous helicopter, Aerosp. Sci. Technol. 10 (6) (2006) 527–533. [2] Y.W. Huang, K.W. Chiang, An intelligent and autonomous MEMS IMU/GPS integration scheme for low cost land navigation applications, GPS solut. 12 (2) (2008) 135–146. [3] Y. Chen, E.E. Aktakka, J.K. Woo, et al., On-chip capacitive sensing and tilting motion estimation of a micro-stage for, in situ, MEMS gyroscope calibration, Mechatronics 56 (2018) 242–253. [4] D. Lee, S. Lee, S. Park, et al., Test and error parameter estimation for MEMS — based low cost IMU calibration, Int. J. Precis. Eng. Manuf. Technol. 12 (4) (2011) 597–603. [5] P. Aggarwal, Z. Syed, X. Niu, et al., A standard testing and calibration procedure for low cost MEMS inertial sensors and units, J. Navigation 61 (2) (2008) 323–336. [6] G. Casinovi, W.K. Sung, M. Dalal, et al., Electrostatic self-calibration of vibratory gyroscopes, Proc. Int. Conf. on Micro Electro Mechanic. S. (MEMS) (2012) 559–562. [7] T. Dar, K. Suryanarayanan, A. Geisberger, No physical stimulus testing and calibration for MEMS accelerometer, J. Microelectromech. Syst. 23 (4) (2014) 811–818. [8] R. Puers, S. Reyntjens, RASTA—real-acceleration-for-self-test accelerometer: a new concept for self-testing accelerometers, Sensor. Actuat. A-Phys. 97 (2002) 359–368. [9] B. Edamana, K. Oldham, An iterative learning controller for high precision calibration of an inertial measurement unit using a piezoelectric platform, ASME 2013 Dyna. S. Contr. Conf. (2013), DSCC2013-3974. [10] B. Edamana, D. Slavin, E.E. Aktakka, et al., Control and estimation with threshold sensing for Inertial Measurement Unit calibration using a piezoelectric microstage, Ame. Contr. Conf. IEEE (2014) 3674–3679. [11] B. Edamana, Y. Chen, D. Slavin, et al., Estimation with threshold sensing for gyroscope calibration using a piezoelectric microstage, IEEE Trans. Control Syst. Technol. 23 (2015) 1943–1951. [12] Y. Bai, J.T.W. Yeow, P. Constantinou, et al., A 2-D micromachined SOI MEMS mirror with sidewall electrodes for biomedical imaging, IEEE. ASME 15 (4) (2010) 501–510. [13] X. Liu, K. Kim, Y. Sun, A MEMS stage for 3-Axis nanopositioning, IEEE conf, Auto. Sci. Engin. (2007), E04.1. [14] J. Dong, P.M. Ferreira, Electrostatically actuated cantilever with SOI-MEMS parallel kinematic XY stage, J. Microelectromech. Syst. 18 (3) (2009) 641–651. [15] X. Zhang, L. Zhou, H. Xie, A large range micro-XZ-stage with monolithic integration of electrothermal bimorph actuators and electrostatic comb drives, Int. Conf. on Micro Electro Mechanic. S. (MEMS) (2016) 71–74. [16] J. Choi, T. Wang, K. Oldham, Dynamics of thin-film piezoelectric microactuators with large vertical stroke subject to multi-axis coupling and fabrication asymmetries, J. Micromech, Microeng. 28 (1) (2016), 015014. [17] K. Kanda, S. Moriue, T. Fujita, et al., Three-dimensional piezoelectric MEMS actuator by using sputtering deposition of Pb(Zr,Ti)O3 , on microstructure sidewalls, Smart Mater. Struct. 26 (4) (2017), 045019.
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Biographies
Yu Chen received the B.E. degree and M.S degree in mechatronics engineering from the University of Electronic Science and Technology of China, in 2012 and 2015, respectively. He is currently working in China Academy of Engineering Physics. He’s currently research field is MEMS Packaging and MEMS integration technology.
Xiangyu Sun received his B.E. degree (2011) in Microelectronic Technology, Ph.D. degree (2017) in Microelectronics and Solid Electronics from the University of Electronic Science and Technology of China. He is currently working in China Academy of Engineering Physics as an assistant research fellow. He’s currently research field is novel MEMS actuators and MEMS integration technology.
Long Zhang received the B.E. degree in Physics major of Electronic Materials Engineering from the LanZhou University of China. And, he received M.S degree in Integrated Circuit Engineering major of System in Package from the Tsinghua University of China. He’s currently research field is 3D Advanced Packaging Technology and System in Package (SiP) in 2012 and 2019.He is currently working in China Academy of Engineering Physics.
Yicheng Wang received his B.E. degree (2011) in Microelectronic Technology, Ph.D. degree (2016) in Microelectronics and Solid Electronics from the University of Electronic Science and Technology of China. He is currently working in Microsystem \& Terahertz Research Center as an assistant research fellow. He’s currently research field is MEMS technology.
Xiaoshi Li received the B.E. degree in electronic science and technology, and the M.E. degree in instrumentation engineering from Chongqing University, Chongqing, China, in 2014 and 2017, respectively. He is currently with the Microsystem and Terahertz Research Center, China Academy of Engineering Physics. His research interests include signal processing circuit, sensors and actuators, and instrumentation.
Dongdong Gong was born in 1990. He received the bachelor’s degree from University of Electronic Science and Technology of China (UESTC) in 2013 and the master’s degree in Materials Science and Engineering in 2017. He is a employee in Microsystems and THz Research Center now. His current research interests are focused on piezoelectric actuator.
Tianyu Yang received the B.S. and M.S. degrees in automatic control (of electrical engineering) from Dalian University of Technology, Dalian, China, in 2015 and in 2018 respectively. Currently, he is the assistant engineer at the Chinese Academy of Engineering Physics, Chengdu, China. His present research interests include system identification, signal processing, and intelligent control for MEMS and their engineering applications.
Feng Qin received the B.E. degree in electronic science from Chengdu University of Technology, Chengdu, China in 2015.He is currently pursuing the Ph.D. degree in the Department of Integrated Circuits and Systems, School of Electronic Engineering, University of Electronic Science and Technology of China, Chengdu, China. His research interests are focused piezoelectric behavior mechanism and application research on microelectromechanical system, including research on high dynamic characteristics of piezoelectric actuators, in-situ health prognostic and self-calibration of inertial sensors, as well as fabrication process, packaging technology and control circuit design for MEMS.
Contents lists available at ScienceDirect
Sensors and Actuators A: Physical journal homepage: www.elsevier.com/locate/sna
An integrated opto-mechatronic system for self-calibration of accelerometer in large dynamic range Yu Chen a,b , Xiangyu Sun a,b,∗ , Long Zhang a,b , Yicheng Wang a,b,∗ , Xiaoshi Li a,b , Dongdong Gong a,b , Tianyu Yang a,b , Feng Qin a,b a b
Microsystem & Terahertz Research Center, ChinaAcademy of Engineering Physics, Chengdu, China Institute of Electronic Engineering, China Academy of Engineering Physics, Mianyang, China
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Article history: Received 26 April 2019 Received in revised form 10 September 2019 Accepted 10 September 2019 Available online 14 September 2019 Keywords: Integrated opto-mechatronic system Accelerometer self-calibration Piezoelectric microvibrator Optical sensing system
a b s t r a c t Long-term instability and scale factor drift are inherent problems in micro inertial measurement units (MIMU) such as accelerometers. This research achieves a novel integrated opto-mechatronic system of less than 1.6 cm3 , containing an advanced six degree-of-freedom (DOF) piezoelectric microvibrator, a commercial micro-accelerometer and an optical displacement sensing system. In the integrated opto-mechatronic system, the piezoelectric microvibrator is the source of standard acceleration for selfcalibration. It is capable of providing an acceleration of up to 30 g and an angular velocity of 1100◦ /s. The optical sensing system is applied to detect the real-time acceleration of the microvibrator to provide detection data for self-calibration. Moreover, the optical sensing system also self-detects and self-adjusts the output acceleration of the microvibrator. The external control and processing unit calculates the error coefficient of the accelerometer to obtain the compensation model to achieve self-calibration, according to the acceleration detected from the optical sensing system and the acceleration output from the accelerometer. The experimental results show that the output accuracy of the micro accelerometer is significantly improved after a complete self-calibration process from 0 to 24 g acceleration range. © 2019 Published by Elsevier B.V.
1. Introduction The micro inertial measurement unit (MIMU) has a wide range of applications in inertial navigation, attitude estimation and position recognition by providing inertial information with multiple degrees of freedom [1,2]. Therefore, it is widely used in aerospace, biomedical and functional electronic devices. Currently, the operational accuracy of the micro inertial sensor is close to that of the macro inertial sensors. However, inherent problems such as drift of scale factor and long-term instability limit the output accuracy and the potential of MIMU in high-precision strategy and navigation applications [3,4]. In order to compensate for drift, the calibration of the MIMU becomes critical. Usually, the calibration is conducted using macro calibration system with a macro shaker and laser Doppler vibrometer. However, the calibration validity period based on the traditional calibration method is short. In addition, it requires the
∗ Corresponding author: Microsystem & Terahertz Research Center, China Academy of Engineering Physics, Chengdu, China. E-mail addresses: [email protected] (X. Sun), [email protected] (Y. Wang). https://doi.org/10.1016/j.sna.2019.111612 0924-4247/© 2019 Published by Elsevier B.V.
support of external equipment [5–7]. Most critically, traditional calibration methods cannot achieve independent self-calibration for the MIMU in any scene. With the development of MEMS processes, the application of embedded internal or integrated microstructures to self-calibrate microsensors before operation to compensate for long-term drift errors can fundamentally reduce long-term dependence. Moreover, the MIMU integrated self-calibration system has higher stability and greatly expands the application of MEMS inertial sensors [8–11]. The MEMS micro actuator acts as an integrated microstructure to provide standard acceleration for the MIMU. The independent self-calibration of MIMU places high demands of high precision, adjustable range and wide range output to the micro actuator [12–15]. Piezoelectric micro actuators are widely used in the field of micromechanical operation due to their low driving voltage, fast response and precise control capability [16–19]. Therefore, applying the piezoelectric micro actuator as a source of acceleration and angular velocity makes it possible to the self-calibration of the MIMU to be integrated into a whole system [20–22]. In order to simplify the calibration process and realize the selfcalibration of accelerometer, this paper proposes an integrated opto-mechatronic system consisting of a piezoelectric microvibra-
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Fig. 1. Graphical overview of the integrated opto-mechatronic system for selfcalibration.
tor, an optical displacement sensing system and an accelerometer. The high dynamic piezoelectric microvibrator provides an acceleration within 30 g and an angular velocity within 1100◦ /s. An optical sensing system consisting of a vertical cavity surface emitting laser (VCSEL) and 8 photodiodes (PDs) are used to detect the vibration information of microvibrator. Through micro mechanical structure stacking technology and optical cavity integration technology, the piezoelectric microvibrator, the commercial micro accelerometer and the optical displacement sensing system are integrated into chip-level integrated opto-mechanical systems. The closed loop control process is performed based on optical sensing system so that the microvibrator operates at a steady standard acceleration. The error compensation model is built to achieve self-calibration for the accelerometer based on the standard acceleration and the actual output acceleration. 2. Design and methods The integrated opto-mechatronic system consists of a 6 DOF microvibrator, a large dynamic range accelerometer, and an optical displacement sensing system, forming a chip-level packaging by a three-dimensional heterogeneous integration method, as shown in Fig. 1. Among them, the microvibrator acts as source of acceleration and angular velocity, providing the required acceleration and angular velocity in different directions for self-calibration. The accelerometer is the unit to be detected and calibrated, which is electrically connected to the microvibrator. The optical sensing system is composed of a VCSEL and 8 PDs which detects the output acceleration of the microvibrator and implements self-calibration of the accelerometer through feedback control. The 6 DOF microvibrator based on PZT thin film is the most important component in the self-calibration system. The operation principle of the microvibrator is actually built on a forced vibration system with damping [23]. As shown in Fig. 2(a), a 3 mm * 3 mm suspended center table is supported by four well-designed folded beams at the corners. The structural design of the folded beams is based on the vibration of a typical single-ended fixed-support cantilever beam in the d31 mode. It makes the microvibrator keep a large elasticity coefficient and a suitable system stiffness to complete the motion at various degrees of freedom. Eight separate electrodes are deposited on each beam to achieve independent control of eight beams. By independently driving the corresponding beams of the microvibrator, a 6 DOF vibration mode of the center table can be achieved. Fig. 2(b) exhibits the motions of 6 DOF achieved by the four vibration modes of the microvibrator, which are translation and rotation along the x/y/z axis, respectively. The microvibrator is designed to achieve an acceleration of 30 g in the
z-axis direction, and an out-of-plane angular speed above 1000◦ /s [24]. The microvibrator is fabricated using wafer-level micromachining technology. The fabricated process is shown in Fig. 3(a). A standard 25 m top silicon SOI wafer is used to grow 5 m PZT and 200 nm Pt as the upper and lower electrodes. The PZT upper electrode is then patterned as the driving electrodes of the folding beams. After the PZT is wet etched and the top silicon is dry etched, the structure of beams has appeared. Subsequently, a layer of silicon dioxide is deposited as an isolation layer to isolate the driving electrodes for folded beam. The second layer of metal Pt is then grown on the silicon dioxide layer as for the control routes for the folding beams and signal routes for the accelerometer. Finally, the SOI bottom silicon is etched by DRIE to form the microvibrator suspended structure. The finished microvibrator and the details are shown in Fig. 3(b). The accelerometer of MPU-6500 from Invensense with a small 3 × 3 x 0.9 mm Quad Flat No-lead (QFN) package and acceleration up to ±16 g is accurately placed on the center table of the microvibrator. Due to the challenge to the packaging technology from the weak structure of the microvibrator, a positioning limit fixture is placed under the cavity structure of the microvibrator to prevent the center table from being broken due to excessive deformation. In addition, the positioning limit fixture also acts as a height limiter for the microvibrator during operation, achieving protection against large vibrations of the microvibrator. The pads of the accelerometer are electrical connected with the metal pads on the microvibrator by the micro mechanical structure lamination technique, as shown in Fig. 4. The technology takes laser alignment and microlevel mechanical operation to achieve accurate stacking of multiple mechanical structures. In order to ensure the accuracy of the stacking, the position data of the microvibrator and the accelerometer are obtained according to calculation, experiment and compensation. Subsequently, the tools for the alignment is designed to meet the requirements of precise alignment. This technology solves the problem of sensitive structure protection and alignment at the integration between micro mechanical structures of microvibrator and accelerometer chip. In addition, the low temperature bonding method is used in the stacking, so that the microvibrator and the accelerometer are bonded at a low temperature of less than 160 ◦ C, which reduces the residual stress introduced into the integrated package. The optical displacement sensing method has the advantages of simple architecture and implementation, high sensitivity, and low dependency on wavelength stability of the light source [25]. As shown in Fig. 5, the non-contact optical displacement sensing system consists of a VCSEL and 8 PDs for the detection of the motion state of the microvibrator [26–28]. As the vibration displacement of the microvibrator changes, the intensity of the light received by the PD changes. Through the signal processing circuit, the change of the received light intensity of the PD is converted into a change of the voltage signal. The magnitude of the PD output voltage represents the displacement of the microvibrator. In order to reduce the error from single PD, eight PDs in the inner ring and the outer ring are designed to obtain the change in the displacement of the microvibrator. In the same way, by obtaining the strength of the two PD output voltages on the same coordinate axis of the inner ring or the outer ring, the angular displacement information of the microvibrator can be obtained by using the different sum ratio. The optical sensing system is located at an appropriate distance above the accelerometer with an air gap of approximately 1 mm as an optical cavity. The schematic of the optical sensing system and the fabricated device are also shown in Fig. 5. Due to the detecting accuracy of micron-level vibration, concentric circle high precision patches for the 8 PD chips are required with the relative accuracy
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Fig. 2. The piezoelectric microvibrator. (a) The structure of microvibrator with suspended center. (b) The vibration mode of six-degree-of-freedom.
Fig. 3. (a) The fabricated process of the microvibrator. (b)The microvibrator with details after fabrication.
requirement between PDs less than +/- 1 m. A high-precision optical patch device is conducted to patch the optical displacement sensing system. Multiple alignment marks are set on the patch substrate and the dummy patch is used for the analog patch. The position data is compensated according to the calculation result
until the demand is required. The optical sensing system provides a detection resolution higher than 150 nm. A reflector is fixed on the top surface of the accelerometer. The relative motion between the reflector and the optical detector affects the intensity distribution of the reflected lights. Different PDs simultaneously extract
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Fig. 4. Micro mechanical structure stacking technology for the integration of microvibrator subsystem.
Fig. 5. Schematic and real graph of the optical displacement sensing system.
the reflected lights to obtain micro-displacement and micro-angle changes. The optical cavity integration technology provides a feasible technical approach to integrate optoelectronic functions in MEMS, which can be used for high-precision dynamic detection of micro mechanical structures. Aiming at the problem of reflected light interference in non-contact detection in optical displacement sensing system, the innovative two-piece package carrier structure design. The selective optical path in different vibration is realized by the well-designed sunshade sheet and reflective sheet on the glass cover. After molding of the peripheral closed cavity structure, a stable optical cavity structure is formed in the package structure to eliminate the interference of VCSEL emission light and reflected light. In the three-dimensional integration for the device, the fabricated bottom substrate and the cavity support structure are designed and processed to integrally assemble the positioning limit fixture, microvibrator with accelerometer, and the optical sensing system into a whole module. In the packaging process, first, the fabrication of the electrode pad has been completed on the bottom substrate of the chip. Then, the positioning limit fixture is fixed on the fabricated bottom substrate, while the MEMS microvibrator is high-accurately stacked on the positioning fixture. The accelerometer with an aluminum-plated silicon reflective mirror is integrated onto the microvibrator. Subsequently, the optical displacement sensing system is integrated with the microvibrator and accelerometer by the means of an inverted package. In placing the
patch, the image recognition technology is applied to identify the pattern of the bottom pad of the accelerometer and the metal pattern. With the help of the visual recognition data and real-time positioning, the accelerometer is accurately placed on the microvibrator. The alignment tolerance is within ±20 m. The upper substrate of optical sensing system is optically electrical connected with the package by adding a three-dimensional interconnected metal pins to the sidewall of the package. This method is combined with the microvibrator double-layer metal wiring design method to realize the accelerometer multi-port and ¨ ¨ microvibrator multi-port flip-chip electrical signal interconnection. When the three-dimensional stacking of the respective components is completed, the top substrate on which the peripheral circuits have been integrated is covered on the cavity supporting structure. An external metal lead is then applied to electrically interconnect the top optical system to the bottom substrate. Finally, the designed wall casing combined with the sealing process of design development and processing is assembled into a threedimensional closed mechanical structure. Micro mechanical structure stacking technology and optical cavity integration technology together constitute optical and electromechanical three-dimensional integrated interconnection technology. This technology can be applied to multi-chip integrated multi-function module internal interconnection. The completed chip-level fully packaged integrated opto-mechatronic system is shown in Fig. 6. The size of the chip is 15 mm * 15 mm * 6.8 mm, including a complete six-degree-of-freedom microvibrator, an
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Fig. 6. The completely fabricated chip-level, fully packaged integrated opto-mechanical system.
Fig. 7. The self-calibration workflow of the integrated opto-mechatronics system.
integrated large dynamic range accelerometer and the optical displacement sensing system. The integrated opto-mechatronics system has enabled in-situ self-calibration of the accelerometer in any occasions without the need for external equipment.
3. Experimental results The self-calibration workflow of the integrated optomechatronics system is shown in Fig. 7. When self-calibration begins, the control and processing unit provides the required excitation for the vibration mode to driving the microvibrator. And based on the real-time data provided by optical detection, the vibration table can be stably and accurately operated at the required acceleration point through closed-loop control. Since the microvibrator and the accelerometer are bonded together, the output acceleration of the microvibrator is exactly the actual acceleration of the accelerometer. After the microvibrator stabi-
lizes the vibration, the control unit reads the acceleration value (read value) obtained by the accelerometer. The control unit establishes the error model through the calibration algorithm and then iterates. After calibration of the complete dynamic range, the system completes the self-calibration for the accelerometer. The microvibrator works at resonance conditions. The AC driving signals are provided separately for each of the top excitation electrodes with different input modes to drive the desired multidegree of freedom motion. In order to independently evaluate the performances of the microvibrator, the tests are performed by an external laser Doppler vibrometer (LDV). The output acceleration and angular velocity of the micro\vibrator are shown in Fig. 8. It can be seen that the microvibrator can provide an acceleration of up to 30 g and an angular velocity of 1100◦ /s, covering the entire measurement range of the accelerometer. In addition, both the acceleration and angular velocity of the microvibrator can be operated in regions with good linearity. Thus, the dynamic output of
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Fig. 8. The acceleration and angular velocity of the microvibrator output with the excitation voltage.
the microvibrator can be adjusted by simply regulating the magnitude of the excitation voltage. This enables reliable operation and fast response of the output acceleration adjustment. Since the realtime vibration state of the vibrating table can be obtained by optical inspection, the control unit can precisely adjust the acceleration and angular velocity of the microvibrator to any desired value by the linear relationship of voltage-acceleration of the microvibrator. The custom optical displacement sensing system is used to detect the precise motion of the microvibrator, including displacement (acceleration) and rotation angle (angular velocity). The actual motion state obtained is used as an input for the error model and closed loop control. In order to evaluate the performance of the optical sensing system, the microvibrator with the accelerometer plays as the vibration source, and the LDV is taken again as an external standard. The test shows that the optical detection range can reach 50 m for the mode in which the micro-vibrator moves along Z-axis. In the mode of tilting motion, the detection angle can reach 0.6◦ . In order to verify the measurement performance and resolution of the optical sensing system, the microvibrator is controlled to generate dynamic vibration with an amplitude of 150 nm for the detection by the optical sensing system. Fig. 9(a) shows the raw measurements from the optical sensing system which shows a good difference between each step. It exhibits that the integrated optical sensing system is capable of accurately detecting the real-time vibration state of the microvibrator. To evaluate the dynamic response of the optical sensing system, the control and processing unit simultaneously receives dynamic acceleration from the accelerometer (read value) and the optical sensing system (measured value). The dynamic test results are calibrated by the quasi-static test results. The measurement
Fig. 9. (a) The measurement of the optical sensing systems to different external accelerations. (b) Real-time comparison of the measurement results of the optical sensing system with the reading results of the accelerometer.
results obtained by LDVs, which reveals that the OBDM detector could reflect the full cycle of vibration, as shown in Fig. 9(b). From Fig. 9(b), on the one hand, it can be seen that the frequency and amplitude responses in the acceleration dynamic curve are high stable in the time domain, indicating the stable output capability of the microvibrator. On the other hand, the dynamic acceleration curves from accelerometers (read values) and optical sensing systems (measured values) are highly overlapping in frequency and phase. This reveals a good consistency between the optical sensing system detection and the accelerometer output. While the difference in amplitude of the acceleration just reflects the error between the accelerometer output and the actual acceleration. The preliminary results indicate that a resolution of 150 nm is obtained. In the present experiment results, the resolution is limited by the circuit noise and the error sources introduced by the testing system. The above two problems can be solved through the optimization of testing system and low-noise circuit, such as smoothing filtering algorithm or low noise amplifier (LNA), and better resolution of 6 nm is expected. The integrated opto-mechatronic system is verified to be capable of performing self-calibration for the accelerometer by the independent testing of the dynamic performance of the microvibrator and the detection capabilities of the optical sensing system. After withdrawing the external test equipment, the self-calibrated of the integrated system is conducted according to the expected self-calibration mode in Fig. 7. The self-calibration of the accelerometer through the integrated opto-mechatronic sys-
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4. Conclusions
Fig. 10. Self-calibration for the accelerometer by the integrated opto-mechanical system.
Table 1 The total current noise of the signal processing circuit. Type of noise
Noise Amplitude
Thermal noise of amplifying circuit Current noise of Amplifier circuit Current noise of Photodiodes Current noise of first stage filter circuit Current noise of second stage filter circuit
9 pA 1.62 pA (LTC1050C) 1.8 pA 20.425 pA (AD8620BRZ) 20.425 pA (AD8620BRZ)
*The total current noise at the input port of the signal processing circuit is the root mean square of the sum of the squares of all noises.
tem is shown in Fig. 10. The acceleration is tested at 200 Hz, which exceeds the normal operating range of the accelerometer. Thus the error of the accelerometer increases significantly. It is clear that before self-calibration, the error of the acceleration increases as the acceleration increases. The read value of the accelerometer has a deviation of nearly 35% at 15 g compared to the standard acceleration. After self-calibration by the integrated opto-mechatronic system, the output read value of the accelerometer has been evidently calibrated. The maximum error of acceleration is no more than 1.5%. The system noise mainly comes from two aspects. The first aspect is the sensing noise, including the internal resistance thermal noise of the PD, the dark current shot current noise, and the mirror current shot current noise. With the help of the optical sensor structure design, the PD noise is effectively reduced to 1.8 pA, where the noise of PD dark current is 0.1 nA at the signal bandwidth of 5 kHz. The second aspect is the noise generated by the signal processing circuit in the control and processing unit, mainly including the thermal noise of the amplifying circuit, the current noise of the circuit, and the voltage noise. Based on the theoretical calculation method of noise signal, the total current noise at the input port of the signal processing circuit is calculated to be about 30.33 pA. The detailed overall noise signals in this system are listed in Table 1. The power consumption of the integrated opto-mechatronic system is mainly from the signal processing circuit. The accelerometer consumes 990 W in standard operating mode. The maximum power consumption of the VCSEL is 12.6 mW. The PDs absorbs and reflects the energy from external laser. Thus, PDs have no power consumption in principle. If calculating the power consumption of PDs from output signal current, the maximum power consumption of 10 PDs is 30 W. The power consumption of the detection and signal processing circuit is mainly from the chopper-stabilized operational amplifier which maximum power consumption is 2500 mW.
This article presents an integrated opto-mechatronic system that includes a piezoelectric microvibrator, a commercial micro-accelerometer and an optical displacement sensing system. The system is designed to independently self-calibrate its internal accelerometer. PZT-based piezoelectric microvibrator manufactured by full micro-machining technology can achieve 6-degree-of-freedom vibration and provide a reliable vibration source for self-calibration. Through the micro mechanical structure lamination technology, the accelerometer and the microvibrator are low-temperature bonded under the microvibrator double-layer wiring design, with the achievement of the accelerometer signal electrical connection. The optical displacement sensing system with VCSEL and PDs realizes chip-level packaging of each component through optical and electromechanical three-dimensional integrated interconnection technology. Experimental results show that the microvibrator is capable of providing an acceleration of up to 30 g and an angular velocity of 1100◦ / s. The optical sensing system can measure a vertical displacement of 50 m and a tilting angle of 0.6◦ . In the self-calibration operation, the optical sensing system detects the real-time acceleration from the microvibrator, and control unit reads the output acceleration from the accelerometer. After self-calibration by the integrated optomechatronic system, the accelerometer error is less than 1.5%. References [1] J. Wendel, O. Meister, C. Schlaile, et al., An integrated GPS/MEMS-IMU navigation system for an autonomous helicopter, Aerosp. Sci. Technol. 10 (6) (2006) 527–533. [2] Y.W. Huang, K.W. Chiang, An intelligent and autonomous MEMS IMU/GPS integration scheme for low cost land navigation applications, GPS solut. 12 (2) (2008) 135–146. [3] Y. Chen, E.E. Aktakka, J.K. Woo, et al., On-chip capacitive sensing and tilting motion estimation of a micro-stage for, in situ, MEMS gyroscope calibration, Mechatronics 56 (2018) 242–253. [4] D. Lee, S. Lee, S. Park, et al., Test and error parameter estimation for MEMS — based low cost IMU calibration, Int. J. Precis. Eng. Manuf. Technol. 12 (4) (2011) 597–603. [5] P. Aggarwal, Z. Syed, X. Niu, et al., A standard testing and calibration procedure for low cost MEMS inertial sensors and units, J. Navigation 61 (2) (2008) 323–336. [6] G. Casinovi, W.K. Sung, M. Dalal, et al., Electrostatic self-calibration of vibratory gyroscopes, Proc. Int. Conf. on Micro Electro Mechanic. S. (MEMS) (2012) 559–562. [7] T. Dar, K. Suryanarayanan, A. Geisberger, No physical stimulus testing and calibration for MEMS accelerometer, J. Microelectromech. Syst. 23 (4) (2014) 811–818. [8] R. Puers, S. Reyntjens, RASTA—real-acceleration-for-self-test accelerometer: a new concept for self-testing accelerometers, Sensor. Actuat. A-Phys. 97 (2002) 359–368. [9] B. Edamana, K. Oldham, An iterative learning controller for high precision calibration of an inertial measurement unit using a piezoelectric platform, ASME 2013 Dyna. S. Contr. Conf. (2013), DSCC2013-3974. [10] B. Edamana, D. Slavin, E.E. Aktakka, et al., Control and estimation with threshold sensing for Inertial Measurement Unit calibration using a piezoelectric microstage, Ame. Contr. Conf. IEEE (2014) 3674–3679. [11] B. Edamana, Y. Chen, D. Slavin, et al., Estimation with threshold sensing for gyroscope calibration using a piezoelectric microstage, IEEE Trans. Control Syst. Technol. 23 (2015) 1943–1951. [12] Y. Bai, J.T.W. Yeow, P. Constantinou, et al., A 2-D micromachined SOI MEMS mirror with sidewall electrodes for biomedical imaging, IEEE. ASME 15 (4) (2010) 501–510. [13] X. Liu, K. Kim, Y. Sun, A MEMS stage for 3-Axis nanopositioning, IEEE conf, Auto. Sci. Engin. (2007), E04.1. [14] J. Dong, P.M. Ferreira, Electrostatically actuated cantilever with SOI-MEMS parallel kinematic XY stage, J. Microelectromech. Syst. 18 (3) (2009) 641–651. [15] X. Zhang, L. Zhou, H. Xie, A large range micro-XZ-stage with monolithic integration of electrothermal bimorph actuators and electrostatic comb drives, Int. Conf. on Micro Electro Mechanic. S. (MEMS) (2016) 71–74. [16] J. Choi, T. Wang, K. Oldham, Dynamics of thin-film piezoelectric microactuators with large vertical stroke subject to multi-axis coupling and fabrication asymmetries, J. Micromech, Microeng. 28 (1) (2016), 015014. [17] K. Kanda, S. Moriue, T. Fujita, et al., Three-dimensional piezoelectric MEMS actuator by using sputtering deposition of Pb(Zr,Ti)O3 , on microstructure sidewalls, Smart Mater. Struct. 26 (4) (2017), 045019.
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Biographies
Yu Chen received the B.E. degree and M.S degree in mechatronics engineering from the University of Electronic Science and Technology of China, in 2012 and 2015, respectively. He is currently working in China Academy of Engineering Physics. He’s currently research field is MEMS Packaging and MEMS integration technology.
Xiangyu Sun received his B.E. degree (2011) in Microelectronic Technology, Ph.D. degree (2017) in Microelectronics and Solid Electronics from the University of Electronic Science and Technology of China. He is currently working in China Academy of Engineering Physics as an assistant research fellow. He’s currently research field is novel MEMS actuators and MEMS integration technology.
Long Zhang received the B.E. degree in Physics major of Electronic Materials Engineering from the LanZhou University of China. And, he received M.S degree in Integrated Circuit Engineering major of System in Package from the Tsinghua University of China. He’s currently research field is 3D Advanced Packaging Technology and System in Package (SiP) in 2012 and 2019.He is currently working in China Academy of Engineering Physics.
Yicheng Wang received his B.E. degree (2011) in Microelectronic Technology, Ph.D. degree (2016) in Microelectronics and Solid Electronics from the University of Electronic Science and Technology of China. He is currently working in Microsystem \& Terahertz Research Center as an assistant research fellow. He’s currently research field is MEMS technology.
Xiaoshi Li received the B.E. degree in electronic science and technology, and the M.E. degree in instrumentation engineering from Chongqing University, Chongqing, China, in 2014 and 2017, respectively. He is currently with the Microsystem and Terahertz Research Center, China Academy of Engineering Physics. His research interests include signal processing circuit, sensors and actuators, and instrumentation.
Dongdong Gong was born in 1990. He received the bachelor’s degree from University of Electronic Science and Technology of China (UESTC) in 2013 and the master’s degree in Materials Science and Engineering in 2017. He is a employee in Microsystems and THz Research Center now. His current research interests are focused on piezoelectric actuator.
Tianyu Yang received the B.S. and M.S. degrees in automatic control (of electrical engineering) from Dalian University of Technology, Dalian, China, in 2015 and in 2018 respectively. Currently, he is the assistant engineer at the Chinese Academy of Engineering Physics, Chengdu, China. His present research interests include system identification, signal processing, and intelligent control for MEMS and their engineering applications.
Feng Qin received the B.E. degree in electronic science from Chengdu University of Technology, Chengdu, China in 2015.He is currently pursuing the Ph.D. degree in the Department of Integrated Circuits and Systems, School of Electronic Engineering, University of Electronic Science and Technology of China, Chengdu, China. His research interests are focused piezoelectric behavior mechanism and application research on microelectromechanical system, including research on high dynamic characteristics of piezoelectric actuators, in-situ health prognostic and self-calibration of inertial sensors, as well as fabrication process, packaging technology and control circuit design for MEMS.