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Development of a shared remote control robot for aerial work in nuclear power plants
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Nuclear Engineering and Technology xxx (2018) 1e6
Contents lists available at ScienceDirect
Nuclear Engineering and Technology journal homepage: www.elsevier.com/locate/net
Original Article
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Development of a shared remote control robot for aerial work in Nuclear power plants Hocheol Shin*, Seung Ho Jung, You Rack Choi, ChangHoi Kim Nuclear Robot and Diagnosis Team, Korea Atomic Energy Institute, 989-111 Daedeok-daero, Yuseong-gu, Daejeon, 305-353, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history: Received 31 January 2018 Received in revised form 10 March 2018 Accepted 11 March 2018 Available online xxx
We are developing a shared remote control mobile robot for aerial work in nuclear power plants (NPPs); a robot consists of a mobile platform, a telescopic mast, and a dual-arm slave with a working tool. It is used at a high location operating the manual operation mechanism of a fuel changer of a heavy water NPP. The robot system can cut/weld a pipe remotely in the case of an emergency or during the dismantling of the NPP. Owing to the challenging control mission considering limited human operator cognitive capability, some remote tasks require a shared control scheme, which demands systematic software design and integration. Therefore, we designed the architecture of the software systematically. © 2018 Korean Nuclear Society, Published by Elsevier Korea LLC. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Keywords: Aerial Work Nuclear Power Plant Shared Remote Control Robot
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1. Introduction The environment for maintaining tasks in nuclear facilities can be hazardous. Therefore, many automation devices are being used to inspect and repair such facilities. However, it is difficult to use fixed automation devices for nonperiodic and infrequent maintenance tasks. Therefore, remotely controlled robot systems have been proposed. If a fuel-handling machine, one of the major components of a PHWR nuclear power plant (NPP), ages, the machine may be stuck on the pressure tube in front of the PHWR calandria. Although the machine has a troubleshooting measure of a manual drive mechanism, it is still a difficult problem to access the manual drive mechanism. When the machine is stuck, the NPP is operated such that the radiation level is extremely high and the machine can be located at a high position of up to 9 m. Therefore, a human worker cannot approach the mechanism, and the mechanism must be handled remotely. Shin et al. developed an aerial working mobile robot for monitoring a high radiation area and operating a manual drive mechanism of a fuel exchange machine (MADMOFEM) [1]. Mitigation robots used during the Fukushima NPP accident and dismantling robots for NPPs should find the exact status of the area while moving around [2e4].
* Corresponding author. E-mail addresses: [email protected] (H. Shin), [email protected] (S.H. Jung), [email protected] (Y.R. Choi), [email protected] (C. Kim).
Because the area of a severe accident of an NPP may be complex with various obstacles, the dismantling robot should deal with dismantled parts and may carry out cutting work. Therefore, an articulated multi-arm robot system is desirable to use rather than a robot with one task-specific device. Using an aerial working mobile robot, we therefore designed a remote control system for maintaining and repairing tasks in an NPP. A dual-arm manipulator is going to be installed instead of a single taskespecific device. We named the remote control system to be developed MARTiN (remote control system for Maintaining And Repairing Tasks in NPP). MARTiN can operate the manual drive mechanism of a fuel exchange machine and cut/weld a pipe during an emergency situation. We developed tools for MARTiN to operate the MADMOFEM and cut a pipe. We tested the feasibility of the prototypes. The dual-arm manipulator as a slave robot is controlled by a master device. It is important to reduce the working time and operator fatigue and to increase the stability and accuracy in the remote work by using a haptic device. In the case of complex tasks, visual and haptic virtual guide technology is useful for reducing the work time and operator fatigue. We tested the efficiency of constraining some degree of freedom (DoF) as a haptic virtual guide [5]. The target tasks and working environment vary from case to case. Therefore, it is difficult to make the virtual guide in advance. We used human intuition to generate the virtual guidance. The operator sketches the path on the visual feedback image of the remote environment. Then, the virtual guide is generated based on the sketches [6].
https://doi.org/10.1016/j.net.2018.03.006 1738-5733/© 2018 Korean Nuclear Society, Published by Elsevier Korea LLC. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).
Please cite this article in press as: H. Shin, et al., Development of a shared remote control robot for aerial work in Nuclear power plants, Nuclear Engineering and Technology (2018), https://doi.org/10.1016/j.net.2018.03.006
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Because the user operates the master device with a limited view of the cameras, he may not understand the situation of the slave robot. Therefore, he may proceed with the work even though the slave robot is approaching a poor kinematic condition such as a singularity position. We designed a master control program to provide helpful information to the operator to intuit the singularity information of the slave robot [7]. The aerial working mobile robot, with a telescopic mast, can raise its dual-arm manipulator to a height of 9 m. If the dual-arm manipulator is operated at that height, vibration at the manipulator base can be caused by the flexibility of the telescopic mast. It is very difficult for a human operator to control the slave robot while suppressing the vibration at the same time. Therefore, we propose a shared control scheme that allows the human operator to control the slave robot only and assign the vibration-suppressing task to the robot system. In addition, we tested the controller using a mockup test bed [8]. 2. Target tasks There can be many tasks in a high radiation area such as the operation of valves and switches. First, we are going to have MARTiN remotely operate the MADMOFEM when the machine is
stuck. In addition, we are going to develop remote control technology with which MARTiN can cut/weld a pipe under an emergency situation or in the dismantling process. Fig. 1 shows an example of the target tasks. Fig. 2 shows the concept of an aerial task in a PHWR NPP. A dualarm manipulator on a telescopic mast on a mobile platform manipulates the MADMOFEM. A human worker in a safe area remotely operates the dual-arm manipulator as a slave robot through the master device.
3. Hardware The mobile platform has four wheels and four flippers. Each flipper has an active small wheel at the end. The platform is able to pass through a gate of 0.9 m in width, to move with loads of 250 kg, and to cross a ditch with a width of 0.75 m and a depth of 0.25 m by using the flippers. The mobile platform changes direction using a skid-steering method, which is easy for the platform with two omni wheels at the rear side. The initial height of the robot should be less than 2 m such that the robot can pass through the gate of the shielding aisle. Therefore, the telescopic mast is composed of identical-shaped frames sliding
Fig. 1. Target tasks.
Fig. 2. Concept of maintenance tasks in nuclear facilities.
Please cite this article in press as: H. Shin, et al., Development of a shared remote control robot for aerial work in Nuclear power plants, Nuclear Engineering and Technology (2018), https://doi.org/10.1016/j.net.2018.03.006
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Cutting oil pump
Saw
Linear guide
Feed motor Steel pipe
SAW motor & reducer
Fig. 5. Cutting tool test bed.
Fig. 3. Mobile platform, slave, and master.
Fig. 6. Concept of the slave robot with the cutting tool.
Fig. 4. MADMOFEM mockup and tools. MADMOFEM, manual drive mechanism of a fuel exchange machine.
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synchronously with a cable-driven mechanism; mast can reach up to 9 m including the mobile platform. The dual arm to be installed on the linear guide on the top of the mast should be light with a high payload capacity and respond to small external forces; as a result, LBR iiwa 14 R820 is chosen as the dual-arm robot. This is a lightweight 7DoF-articulated manipulator that weighs 29.5 kg and has a payload capacity of 14 kg; it is able to move precisely with ±0.1 mm repeatability. It assembles parts delicately and detects external forces with integrated torque sensors. The master device is an Omega 7 of Force Dimension. Omega 7 detects the translational motion of the X/Y/Z directions and the rotational motion of the rx/ry/rz directions. In addition, it supplies the reflection forces, which are 12 N for the translational motion and 8 N for grasping. Its linear accuracy is 0.01 mm. It supplies sufficient stability with an 8 kHz refresh rate.
Fig. 7. Virtual guide for a peg-in-hole task.
Fig. 8. Applying a manipulability ellipsoid from the slave robot to the master device.
Please cite this article in press as: H. Shin, et al., Development of a shared remote control robot for aerial work in Nuclear power plants, Nuclear Engineering and Technology (2018), https://doi.org/10.1016/j.net.2018.03.006
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Fig. 9. Singularity information program GUI.
3DoF manipulator
1DoF linear stage
Flexible beam
Fig. 11. A shared control test bed of the manipulator on a flexible base. DoF, degree of freedom.
Fig. 10. Shared control concept for the MARTiN System.
Fig. 3 shows the mobile platform, slave robots, and master devices. The object to be operated and the work environment are recognized with a depth camera such as a TOF camera and stereo camera. A Kinect v2 (TOF camera) and a ZED camera (stereo camera) were considered as remote field depth formationegathering device. Embedded boards such as ODROID XU4 for the Kinect v2 and Jetson TX1 for the ZED are used in sending the remote field information to the operating room. There are three parts to be operated at MADMOFEM: a clutch axis, an engaging helical gear axis, and a RAM driving axis. We made a MADMOFEM mockup to be tested and an operating tool for the slave robot. The operating tool has three functions: operating the clutch, engaging the helical gear, and driving the RAM. The operating tool is installed at the end of the slave robot. The slave robot can change the position of the operating tool from the helical geareengaging part to the clutch and the RAM driving tool part so that the slave robot can operate three parts of the MADMOFEM.
We previously developed a tele-RAMeoperating device to drive MADMOFEM as a one taskespecific device. The operating tool, at 3 kg, is very light compared with the tele-RAMeoperating device (50 kg). Fig. 4 shows the MADMOFEM mockup, the operating tool, and the previously developed tele-RAMeoperating device. We developed a pipe-cutting tool for the slave robot arm. Because the target is a 2-inch pipe with a 5-mm thickness, a 9-inch circular saw was selected. The circular saw of 2-mm thickness can cut the steel and stainless steel pipe with a 5-mm pitch tooth. We cut the target steel pipe with the cutting tool test bed. It took 21 minutes to cut the target pipe. Fig. 5 shows the cutting tool test bed (see Fig. 6). Q9
Fig. 12. Vibration suppression control response.
Please cite this article in press as: H. Shin, et al., Development of a shared remote control robot for aerial work in Nuclear power plants, Nuclear Engineering and Technology (2018), https://doi.org/10.1016/j.net.2018.03.006
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66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 Fig. 13. Software integration diagram. 97 98 99 100 4.2. Egocentric remote control 4. Shared control 101 102 We will provide helpful information for the operator to feel the Owing to the challenging control mission considering limited 103 poor kinematic conditions of the slave robot, such as a singularity human operator cognitive capability, some remote tasks require a 104 position. To find the singularity direction, the manipulability shared control scheme, which demands systematic software design 105 ellipsoid is computed from the Jacobian matrix of the slave robot. and integration. 106 We can apply the ellipsoid of the slave robot to the master deWe developed software modules separately for the mobile 107 vice. We provide force feedback to the master device based on the platform, the telescopic mast, the linear guide, the slave robots, the 108 size and direction of the ellipsoid, resulting in preventing access to master devices, and the depth camera. 109 the singularity. Fig. 8 shows the slaveemaster system, which is Q11 110 It would be very difficult to integrate the individual software modules if the each module is developed without considering other composed using PHANTOM Omni as the master device and KINOVA 111 modules. Therefore, we designed the architecture of the software to Jaco as the slave robot. 112 successfully integrate the software modules. Fig. 9 shows a program in which the GUI gives visual feedback Q12 113 information of a normalized manipulability measure, singularity 114 direction, and visual feedback of the slaveemaster system of Fig. 8. 115 4.1. Real-time virtual guidance It should be noted that when the manipulator is far from the sin116 gularity posture, the color of the graph is blue. On the other hand, 117 To reduce the working time and operator fatigue, we adopted when the robot approaches the singularity, the color of the graph 118 virtual guide technology. However, because the environment is turns red. In addition, a red arrow in the circle of the GUI indicates 119 unstructured, it is difficult to build the virtual guidance in advance. the direction of the singularity. 120 Therefore, a virtual guide needs to be generated on the spot. 121 One of the target tasks of this research is to operate the MAD122 MOFEM, in which the slave robot arm should insert the operating 123 tool into the driving axes. This task is a peg-in-hole task. 4.3. Shared control of the slave robot 124 First, we select the representative features of the operating tool 125 as a peg on the computer monitor displaying a 2D/3D image of the It is very difficult for the tele-operator to control the slave robot 126 spot: the center of the contour of the peg and its axis. Second, we while suppressing the vibration discussed previously. For the 127 select the driving axis as a hole and normal to its plane. The normal operator to concentrate on carrying out the target task, we applied 128 should be aligned with the center of the hole. Then, a guidance a shared control strategy, in which the system suppresses the vi129 fixture is created that will attract the peg to the axis of the hole. bration of the flexible base automatically. Fig. 10 shows the concept 130 Fig. 7 shows the virtual guide for a peg-in-hole task. of the shared control strategy for the MARTiN system. Please cite this article in press as: H. Shin, et al., Development of a shared remote control robot for aerial work in Nuclear power plants, Nuclear Engineering and Technology (2018), https://doi.org/10.1016/j.net.2018.03.006
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We built a test bed to test the shared control scheme, as shown in Fig. 11. Before we decompose the system dynamics, we obtain the modeling of the system based on the EulereBernoulli theory. We split the flexible base dynamics and the manipulator dynamics to which the original dynamics converges as the vibration is suppressed. We can then build an end-effector tracking controller and a vibration suppression controller separately. Fig. 12 shows the vibration suppression control response when the 3DoF manipulator moves from a folding position to an erect position. 4.4. Integration of the control system The different software types, developed separately, are connected using TCP, USB, and CAN communications and eventually have to be integrated into a single control system. To facilitate the integration of such software types, we set the development environment uniformly: Windows 7 (64bit) OS and VC 2010 for Windows and Ubuntu 14.0.4 (64bit) OS and QT4/Cþþ/Python for Linux. The control frequency or communication frequency is very important in robot control. In addition, when integrating multiple software types, it is especially important to set the priorities of these frequencies. Because the shared control capability of a slave robot and the haptic stability of a master device require a high frequency, the communication frequencies of these components are set at 500 Hz in the development of the MARTiN system. The updating rate for rendering the point, cloud data of the virtual guide and the location information of the object are set to 10 Hz. In addition, the communication frequency of each joint state and the joint control data are set to 100 Hz. Fig. 13 shows the communication connection and communication periods for integration of the software described previously. It should be noted that the user directly commands the control system with the master device, a mouse, and a keyboard. The control system orders the slave robot to the user-commanded position while suppressing the external disturbance, displays an egocentric view directly from the camera, and creates an exocentric view, virtual guidance, and the shared path on the spot; it then feeds back the shared control information to the user through the monitor and the master device. 5. Conclusions We designed a remote control system, called MARTiN, for aerial tasks in an NPP using an aerial working mobile robot, developed
control algorithms, and carried out a feasibility test. An LBR iiwa 14 R820 was chosen as the dual-arm slave robot, and an Omega 7 of Force Dimension was chosen as the master device. We made a MADMOFEM-operating tool, and a pipe-cutting tool for the slave robot was created and tested. To reduce the working time and operator fatigue and to increase the stability and accuracy in the remote work, we adopted virtual guidance technology and a manipulability ellipsoid to prevent the slave robot from accessing a singularity. The shared controller was developed to automatically suppress the vibration of the flexible base. To integrate individual control algorithms and software, we designed the control architecture, communication flow, and update rate. Evaluation indexes and experiments for the MARTiN system will be designed to evaluate and improve the performance of the technologies. The performance of the MARTiN system will be evaluated through the target tasks. Q14
Acknowledgments This work was supported by the Industrial Strategic Technology Development Program (10060070) funded by MOTIE, Korea.
References [1] H. Shin, C. Kim, Y. Seo, K. Jeong, Y. Choi, B. Choi, J. Moon, Aerial work robot for a nuclear power plant with a pressurized heavy water reactor, Ann. Nucl. Energy 92 (2016) 284e288. [2] J.W. Cho, K.M. Jeong, Remote-controlled robots used for the management of severe accident of the Fukushima nuclear power plant, in: Trans. of the Korean Nuclear Society Autumn Meeting, 2011, pp. 983e987. [3] Mohamed J. Bakari, Khaled M. Zied, Derick W. Seward, Development of a multiarm mobile robot for nuclear decommissioning tasks, Int. J. Adv. Rob. Syst. 4 (4) (2007) 387e406. [4] H. Shin, C. Kim, Y. Seo, M. Kim, B. Choi, Development of a dismantling manipulator for a nuclear reactor, in: Proc. of American Nuclear Society 2016 Topical Meeting D&RS, 2016, pp. 21e23. [5] K.S. Choi, S.W. Ryu, G.H. Yang, Study on measure to shorten work time, through the haptic device in teleoperation system, in: Proc. of URAI 2017, Jeju, Korea, June 27eJuly 1, 2017, pp. 473e476. [6] K.H. Lee, V. Pruks, J.H. Ryu, Development of shared autonomy and virtual guidance generation system for human interactive teleoperation, in: Proc. of URAI 2017, Jeju, Korea, June 27eJuly 1, 2017, pp. 458e461. [7] J.W. Han, G.H. Yang, Singularity avoidance in teleoperation system through force feedback of master device, in: Proc. of URAI 2017, Jeju, Korea, June 27eJuly 1, 2017, pp. 470e472. [8] C. Ha, H. Kim, D. Lee, Experimental evaluation of passivity-based control of manipulator-stage system on flexible beam, in: Proc. of URAI 2017, Jeju, Korea, June 27eJuly 1, 2017, pp. 465e466.
Please cite this article in press as: H. Shin, et al., Development of a shared remote control robot for aerial work in Nuclear power plants, Nuclear Engineering and Technology (2018), https://doi.org/10.1016/j.net.2018.03.006
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Nuclear Engineering and Technology xxx (2018) 1e6
Contents lists available at ScienceDirect
Nuclear Engineering and Technology journal homepage: www.elsevier.com/locate/net
Original Article
Q1 Q15
Development of a shared remote control robot for aerial work in Nuclear power plants Hocheol Shin*, Seung Ho Jung, You Rack Choi, ChangHoi Kim Nuclear Robot and Diagnosis Team, Korea Atomic Energy Institute, 989-111 Daedeok-daero, Yuseong-gu, Daejeon, 305-353, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history: Received 31 January 2018 Received in revised form 10 March 2018 Accepted 11 March 2018 Available online xxx
We are developing a shared remote control mobile robot for aerial work in nuclear power plants (NPPs); a robot consists of a mobile platform, a telescopic mast, and a dual-arm slave with a working tool. It is used at a high location operating the manual operation mechanism of a fuel changer of a heavy water NPP. The robot system can cut/weld a pipe remotely in the case of an emergency or during the dismantling of the NPP. Owing to the challenging control mission considering limited human operator cognitive capability, some remote tasks require a shared control scheme, which demands systematic software design and integration. Therefore, we designed the architecture of the software systematically. © 2018 Korean Nuclear Society, Published by Elsevier Korea LLC. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Keywords: Aerial Work Nuclear Power Plant Shared Remote Control Robot
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1. Introduction The environment for maintaining tasks in nuclear facilities can be hazardous. Therefore, many automation devices are being used to inspect and repair such facilities. However, it is difficult to use fixed automation devices for nonperiodic and infrequent maintenance tasks. Therefore, remotely controlled robot systems have been proposed. If a fuel-handling machine, one of the major components of a PHWR nuclear power plant (NPP), ages, the machine may be stuck on the pressure tube in front of the PHWR calandria. Although the machine has a troubleshooting measure of a manual drive mechanism, it is still a difficult problem to access the manual drive mechanism. When the machine is stuck, the NPP is operated such that the radiation level is extremely high and the machine can be located at a high position of up to 9 m. Therefore, a human worker cannot approach the mechanism, and the mechanism must be handled remotely. Shin et al. developed an aerial working mobile robot for monitoring a high radiation area and operating a manual drive mechanism of a fuel exchange machine (MADMOFEM) [1]. Mitigation robots used during the Fukushima NPP accident and dismantling robots for NPPs should find the exact status of the area while moving around [2e4].
* Corresponding author. E-mail addresses: [email protected] (H. Shin), [email protected] (S.H. Jung), [email protected] (Y.R. Choi), [email protected] (C. Kim).
Because the area of a severe accident of an NPP may be complex with various obstacles, the dismantling robot should deal with dismantled parts and may carry out cutting work. Therefore, an articulated multi-arm robot system is desirable to use rather than a robot with one task-specific device. Using an aerial working mobile robot, we therefore designed a remote control system for maintaining and repairing tasks in an NPP. A dual-arm manipulator is going to be installed instead of a single taskespecific device. We named the remote control system to be developed MARTiN (remote control system for Maintaining And Repairing Tasks in NPP). MARTiN can operate the manual drive mechanism of a fuel exchange machine and cut/weld a pipe during an emergency situation. We developed tools for MARTiN to operate the MADMOFEM and cut a pipe. We tested the feasibility of the prototypes. The dual-arm manipulator as a slave robot is controlled by a master device. It is important to reduce the working time and operator fatigue and to increase the stability and accuracy in the remote work by using a haptic device. In the case of complex tasks, visual and haptic virtual guide technology is useful for reducing the work time and operator fatigue. We tested the efficiency of constraining some degree of freedom (DoF) as a haptic virtual guide [5]. The target tasks and working environment vary from case to case. Therefore, it is difficult to make the virtual guide in advance. We used human intuition to generate the virtual guidance. The operator sketches the path on the visual feedback image of the remote environment. Then, the virtual guide is generated based on the sketches [6].
https://doi.org/10.1016/j.net.2018.03.006 1738-5733/© 2018 Korean Nuclear Society, Published by Elsevier Korea LLC. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).
Please cite this article in press as: H. Shin, et al., Development of a shared remote control robot for aerial work in Nuclear power plants, Nuclear Engineering and Technology (2018), https://doi.org/10.1016/j.net.2018.03.006
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Because the user operates the master device with a limited view of the cameras, he may not understand the situation of the slave robot. Therefore, he may proceed with the work even though the slave robot is approaching a poor kinematic condition such as a singularity position. We designed a master control program to provide helpful information to the operator to intuit the singularity information of the slave robot [7]. The aerial working mobile robot, with a telescopic mast, can raise its dual-arm manipulator to a height of 9 m. If the dual-arm manipulator is operated at that height, vibration at the manipulator base can be caused by the flexibility of the telescopic mast. It is very difficult for a human operator to control the slave robot while suppressing the vibration at the same time. Therefore, we propose a shared control scheme that allows the human operator to control the slave robot only and assign the vibration-suppressing task to the robot system. In addition, we tested the controller using a mockup test bed [8]. 2. Target tasks There can be many tasks in a high radiation area such as the operation of valves and switches. First, we are going to have MARTiN remotely operate the MADMOFEM when the machine is
stuck. In addition, we are going to develop remote control technology with which MARTiN can cut/weld a pipe under an emergency situation or in the dismantling process. Fig. 1 shows an example of the target tasks. Fig. 2 shows the concept of an aerial task in a PHWR NPP. A dualarm manipulator on a telescopic mast on a mobile platform manipulates the MADMOFEM. A human worker in a safe area remotely operates the dual-arm manipulator as a slave robot through the master device.
3. Hardware The mobile platform has four wheels and four flippers. Each flipper has an active small wheel at the end. The platform is able to pass through a gate of 0.9 m in width, to move with loads of 250 kg, and to cross a ditch with a width of 0.75 m and a depth of 0.25 m by using the flippers. The mobile platform changes direction using a skid-steering method, which is easy for the platform with two omni wheels at the rear side. The initial height of the robot should be less than 2 m such that the robot can pass through the gate of the shielding aisle. Therefore, the telescopic mast is composed of identical-shaped frames sliding
Fig. 1. Target tasks.
Fig. 2. Concept of maintenance tasks in nuclear facilities.
Please cite this article in press as: H. Shin, et al., Development of a shared remote control robot for aerial work in Nuclear power plants, Nuclear Engineering and Technology (2018), https://doi.org/10.1016/j.net.2018.03.006
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Cutting oil pump
Saw
Linear guide
Feed motor Steel pipe
SAW motor & reducer
Fig. 5. Cutting tool test bed.
Fig. 3. Mobile platform, slave, and master.
Fig. 6. Concept of the slave robot with the cutting tool.
Fig. 4. MADMOFEM mockup and tools. MADMOFEM, manual drive mechanism of a fuel exchange machine.
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synchronously with a cable-driven mechanism; mast can reach up to 9 m including the mobile platform. The dual arm to be installed on the linear guide on the top of the mast should be light with a high payload capacity and respond to small external forces; as a result, LBR iiwa 14 R820 is chosen as the dual-arm robot. This is a lightweight 7DoF-articulated manipulator that weighs 29.5 kg and has a payload capacity of 14 kg; it is able to move precisely with ±0.1 mm repeatability. It assembles parts delicately and detects external forces with integrated torque sensors. The master device is an Omega 7 of Force Dimension. Omega 7 detects the translational motion of the X/Y/Z directions and the rotational motion of the rx/ry/rz directions. In addition, it supplies the reflection forces, which are 12 N for the translational motion and 8 N for grasping. Its linear accuracy is 0.01 mm. It supplies sufficient stability with an 8 kHz refresh rate.
Fig. 7. Virtual guide for a peg-in-hole task.
Fig. 8. Applying a manipulability ellipsoid from the slave robot to the master device.
Please cite this article in press as: H. Shin, et al., Development of a shared remote control robot for aerial work in Nuclear power plants, Nuclear Engineering and Technology (2018), https://doi.org/10.1016/j.net.2018.03.006
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Fig. 9. Singularity information program GUI.
3DoF manipulator
1DoF linear stage
Flexible beam
Fig. 11. A shared control test bed of the manipulator on a flexible base. DoF, degree of freedom.
Fig. 10. Shared control concept for the MARTiN System.
Fig. 3 shows the mobile platform, slave robots, and master devices. The object to be operated and the work environment are recognized with a depth camera such as a TOF camera and stereo camera. A Kinect v2 (TOF camera) and a ZED camera (stereo camera) were considered as remote field depth formationegathering device. Embedded boards such as ODROID XU4 for the Kinect v2 and Jetson TX1 for the ZED are used in sending the remote field information to the operating room. There are three parts to be operated at MADMOFEM: a clutch axis, an engaging helical gear axis, and a RAM driving axis. We made a MADMOFEM mockup to be tested and an operating tool for the slave robot. The operating tool has three functions: operating the clutch, engaging the helical gear, and driving the RAM. The operating tool is installed at the end of the slave robot. The slave robot can change the position of the operating tool from the helical geareengaging part to the clutch and the RAM driving tool part so that the slave robot can operate three parts of the MADMOFEM.
We previously developed a tele-RAMeoperating device to drive MADMOFEM as a one taskespecific device. The operating tool, at 3 kg, is very light compared with the tele-RAMeoperating device (50 kg). Fig. 4 shows the MADMOFEM mockup, the operating tool, and the previously developed tele-RAMeoperating device. We developed a pipe-cutting tool for the slave robot arm. Because the target is a 2-inch pipe with a 5-mm thickness, a 9-inch circular saw was selected. The circular saw of 2-mm thickness can cut the steel and stainless steel pipe with a 5-mm pitch tooth. We cut the target steel pipe with the cutting tool test bed. It took 21 minutes to cut the target pipe. Fig. 5 shows the cutting tool test bed (see Fig. 6). Q9
Fig. 12. Vibration suppression control response.
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66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 Fig. 13. Software integration diagram. 97 98 99 100 4.2. Egocentric remote control 4. Shared control 101 102 We will provide helpful information for the operator to feel the Owing to the challenging control mission considering limited 103 poor kinematic conditions of the slave robot, such as a singularity human operator cognitive capability, some remote tasks require a 104 position. To find the singularity direction, the manipulability shared control scheme, which demands systematic software design 105 ellipsoid is computed from the Jacobian matrix of the slave robot. and integration. 106 We can apply the ellipsoid of the slave robot to the master deWe developed software modules separately for the mobile 107 vice. We provide force feedback to the master device based on the platform, the telescopic mast, the linear guide, the slave robots, the 108 size and direction of the ellipsoid, resulting in preventing access to master devices, and the depth camera. 109 the singularity. Fig. 8 shows the slaveemaster system, which is Q11 110 It would be very difficult to integrate the individual software modules if the each module is developed without considering other composed using PHANTOM Omni as the master device and KINOVA 111 modules. Therefore, we designed the architecture of the software to Jaco as the slave robot. 112 successfully integrate the software modules. Fig. 9 shows a program in which the GUI gives visual feedback Q12 113 information of a normalized manipulability measure, singularity 114 direction, and visual feedback of the slaveemaster system of Fig. 8. 115 4.1. Real-time virtual guidance It should be noted that when the manipulator is far from the sin116 gularity posture, the color of the graph is blue. On the other hand, 117 To reduce the working time and operator fatigue, we adopted when the robot approaches the singularity, the color of the graph 118 virtual guide technology. However, because the environment is turns red. In addition, a red arrow in the circle of the GUI indicates 119 unstructured, it is difficult to build the virtual guidance in advance. the direction of the singularity. 120 Therefore, a virtual guide needs to be generated on the spot. 121 One of the target tasks of this research is to operate the MAD122 MOFEM, in which the slave robot arm should insert the operating 123 tool into the driving axes. This task is a peg-in-hole task. 4.3. Shared control of the slave robot 124 First, we select the representative features of the operating tool 125 as a peg on the computer monitor displaying a 2D/3D image of the It is very difficult for the tele-operator to control the slave robot 126 spot: the center of the contour of the peg and its axis. Second, we while suppressing the vibration discussed previously. For the 127 select the driving axis as a hole and normal to its plane. The normal operator to concentrate on carrying out the target task, we applied 128 should be aligned with the center of the hole. Then, a guidance a shared control strategy, in which the system suppresses the vi129 fixture is created that will attract the peg to the axis of the hole. bration of the flexible base automatically. Fig. 10 shows the concept 130 Fig. 7 shows the virtual guide for a peg-in-hole task. of the shared control strategy for the MARTiN system. Please cite this article in press as: H. Shin, et al., Development of a shared remote control robot for aerial work in Nuclear power plants, Nuclear Engineering and Technology (2018), https://doi.org/10.1016/j.net.2018.03.006
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We built a test bed to test the shared control scheme, as shown in Fig. 11. Before we decompose the system dynamics, we obtain the modeling of the system based on the EulereBernoulli theory. We split the flexible base dynamics and the manipulator dynamics to which the original dynamics converges as the vibration is suppressed. We can then build an end-effector tracking controller and a vibration suppression controller separately. Fig. 12 shows the vibration suppression control response when the 3DoF manipulator moves from a folding position to an erect position. 4.4. Integration of the control system The different software types, developed separately, are connected using TCP, USB, and CAN communications and eventually have to be integrated into a single control system. To facilitate the integration of such software types, we set the development environment uniformly: Windows 7 (64bit) OS and VC 2010 for Windows and Ubuntu 14.0.4 (64bit) OS and QT4/Cþþ/Python for Linux. The control frequency or communication frequency is very important in robot control. In addition, when integrating multiple software types, it is especially important to set the priorities of these frequencies. Because the shared control capability of a slave robot and the haptic stability of a master device require a high frequency, the communication frequencies of these components are set at 500 Hz in the development of the MARTiN system. The updating rate for rendering the point, cloud data of the virtual guide and the location information of the object are set to 10 Hz. In addition, the communication frequency of each joint state and the joint control data are set to 100 Hz. Fig. 13 shows the communication connection and communication periods for integration of the software described previously. It should be noted that the user directly commands the control system with the master device, a mouse, and a keyboard. The control system orders the slave robot to the user-commanded position while suppressing the external disturbance, displays an egocentric view directly from the camera, and creates an exocentric view, virtual guidance, and the shared path on the spot; it then feeds back the shared control information to the user through the monitor and the master device. 5. Conclusions We designed a remote control system, called MARTiN, for aerial tasks in an NPP using an aerial working mobile robot, developed
control algorithms, and carried out a feasibility test. An LBR iiwa 14 R820 was chosen as the dual-arm slave robot, and an Omega 7 of Force Dimension was chosen as the master device. We made a MADMOFEM-operating tool, and a pipe-cutting tool for the slave robot was created and tested. To reduce the working time and operator fatigue and to increase the stability and accuracy in the remote work, we adopted virtual guidance technology and a manipulability ellipsoid to prevent the slave robot from accessing a singularity. The shared controller was developed to automatically suppress the vibration of the flexible base. To integrate individual control algorithms and software, we designed the control architecture, communication flow, and update rate. Evaluation indexes and experiments for the MARTiN system will be designed to evaluate and improve the performance of the technologies. The performance of the MARTiN system will be evaluated through the target tasks. Q14
Acknowledgments This work was supported by the Industrial Strategic Technology Development Program (10060070) funded by MOTIE, Korea.
References [1] H. Shin, C. Kim, Y. Seo, K. Jeong, Y. Choi, B. Choi, J. Moon, Aerial work robot for a nuclear power plant with a pressurized heavy water reactor, Ann. Nucl. Energy 92 (2016) 284e288. [2] J.W. Cho, K.M. Jeong, Remote-controlled robots used for the management of severe accident of the Fukushima nuclear power plant, in: Trans. of the Korean Nuclear Society Autumn Meeting, 2011, pp. 983e987. [3] Mohamed J. Bakari, Khaled M. Zied, Derick W. Seward, Development of a multiarm mobile robot for nuclear decommissioning tasks, Int. J. Adv. Rob. Syst. 4 (4) (2007) 387e406. [4] H. Shin, C. Kim, Y. Seo, M. Kim, B. Choi, Development of a dismantling manipulator for a nuclear reactor, in: Proc. of American Nuclear Society 2016 Topical Meeting D&RS, 2016, pp. 21e23. [5] K.S. Choi, S.W. Ryu, G.H. Yang, Study on measure to shorten work time, through the haptic device in teleoperation system, in: Proc. of URAI 2017, Jeju, Korea, June 27eJuly 1, 2017, pp. 473e476. [6] K.H. Lee, V. Pruks, J.H. Ryu, Development of shared autonomy and virtual guidance generation system for human interactive teleoperation, in: Proc. of URAI 2017, Jeju, Korea, June 27eJuly 1, 2017, pp. 458e461. [7] J.W. Han, G.H. Yang, Singularity avoidance in teleoperation system through force feedback of master device, in: Proc. of URAI 2017, Jeju, Korea, June 27eJuly 1, 2017, pp. 470e472. [8] C. Ha, H. Kim, D. Lee, Experimental evaluation of passivity-based control of manipulator-stage system on flexible beam, in: Proc. of URAI 2017, Jeju, Korea, June 27eJuly 1, 2017, pp. 465e466.
Please cite this article in press as: H. Shin, et al., Development of a shared remote control robot for aerial work in Nuclear power plants, Nuclear Engineering and Technology (2018), https://doi.org/10.1016/j.net.2018.03.006
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