- Email: [email protected]
Prototyping Small Robots for Junior Competitions: MicroFactory Case study
11th 11th IFAC IFAC Symposium Symposium on on Advances Advances in in Control Control Education Education 11th IFAC Symposium on Advances in Control Education June 1-3, Bratislava, Slovakia JuneIFAC 1-3, 2016. 2016. Bratislava, Slovakia in Control Education 11th Symposium on Advances June 1-3, 2016. Bratislava, Slovakia Available online at www.sciencedirect.com June 1-3, 2016. Bratislava, Slovakia
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Prototyping Small Robots for Junior Prototyping Small Robots for Junior Prototyping Small Robots for Junior Prototyping Small Robots for Junior Competitions: MicroFactory MicroFactory Case Case study Competitions: study Competitions: MicroFactory Case Competitions: MicroFactory Case study study
∗∗ ∗∗∗ ∗∗∗∗ ∗∗ J. Gon¸ ∗∗∗ P. Costa ∗∗∗∗ M. Silva c alves M. Silva c alves ∗∗ J. Gon¸ ∗∗∗ P. Costa ∗∗∗∗ M. Silva c alves ∗∗ J. Gon¸ ∗∗∗ P. Costa ∗∗∗∗ M. Silva J. Gon¸ calves P. Costa ∗ ∗ University of Porto, Portugal. University of Porto, Portugal. ∗ University of ∗ Email: [email protected] University of Porto, Porto, Portugal. Portugal. Email: [email protected] ∗∗ Email: [email protected] ∗∗ Polytechnic Institute Email: [email protected] Institute of of Porto, Porto, Portugal. Portugal. ∗∗ Polytechnic Institute of Porto, Portugal. ∗∗ Polytechnic Email: [email protected] Polytechnic Institute of Porto, Portugal. Email: [email protected] ∗∗∗ Email: [email protected] ∗∗∗ Polytechnic Institute of Bragan¸ c a and INESC-TEC, Portugal. Email: [email protected] Polytechnic Institute of Bragan¸ c a and INESC-TEC, Portugal. ∗∗∗ of Bragan¸ c a and INESC-TEC, Portugal. ∗∗∗ Polytechnic Institute Email: [email protected] Polytechnic Institute of Bragan¸ c a and INESC-TEC, Portugal. Email: [email protected] ∗∗∗∗ [email protected] ∗∗∗∗ UniversityEmail: of Porto and INESC-TEC, Portugal. [email protected] of Porto and INESC-TEC, Portugal. ∗∗∗∗ UniversityEmail: Porto and ∗∗∗∗ University of Email: University of [email protected] and INESC-TEC, INESC-TEC, Portugal. Portugal. Email: [email protected] Email: [email protected] Email: [email protected]
D. D. D. D.
∗ ∗ Neves Neves ∗ Neves Neves ∗
Abstract: Abstract: Abstract: In this paper it is discussed the proposal of aa small robot prototype to be applied in Abstract: In this paper it is discussed the proposal of small robot prototype to be applied in In this paper it is discussed the proposal of a small robot prototype to be applied in the MicroFactory competition, a downsized version of the Robot@Factory competition. The In this paper it is discussed the proposal version of a small robot prototype to be appliedThe in the MicroFactory competition, a downsized of the Robot@Factory competition. the MicroFactory competition, a downsized version of the Robot@Factory competition. The MicroFactory is to junior make the from the MicroFactory competition, a downsized version ofto Robot@Factory The MicroFactory is intended intended to help help junior competitors competitors tothe make the transition transitioncompetition. from the the Junior Junior MicroFactory is intended to junior to make from the Leagues to competition The Robot@Factory competition place MicroFactory intended to help help Robot@Factory. junior competitors competitors make the the transition transition from takes the Junior Junior Leagues to the theissenior senior competition Robot@Factory. Theto Robot@Factory competition takes place Leagues to the senior competition Robot@Factory. The Robot@Factory competition takes in an emulated factory plant, where Automatic Guided Vehicles (AGVs) must cooperate to Leagues to the senior competition Robot@Factory. The Robot@Factory competition takes place place in an emulated factory plant, where Automatic Guided Vehicles (AGVs) must cooperate to in an emulated factory plant, where Automatic Guided Vehicles (AGVs) must cooperate to perform tasks. To accomplish their goals the AGVs must deal with localization, navigation, in an emulated factory plant, their wheregoals Automatic Guided Vehicles (AGVs) must cooperate to perform tasks. To accomplish the AGVs must deal with localization, navigation, perform tasks. To accomplish their goals the AGVs must deal with localization, navigation, scheduling and problems, that must be perform tasks. To accomplish their goals AGVs mustautonomously. deal with localization, navigation, scheduling and cooperation cooperation problems, that the must be solved solved autonomously. scheduling and cooperation problems, that be autonomously. scheduling and cooperation problems, that must mustControl) be solved solved autonomously. © 2016, IFAC (International Federation of Automatic Hosting by Elsevier Ltd. All rights reserved. Keywords: Keywords: Keywords: Mobile robot competitions, competitions, AGVs, AGVs, Prototyping Prototyping Keywords: Mobile robot Mobile Mobile robot robot competitions, competitions, AGVs, AGVs, Prototyping Prototyping 1. INTRODUCTION 1. INTRODUCTION 1. 1. INTRODUCTION INTRODUCTION Robotic competitions are an excellent way to foster reRobotic competitions are an excellent way to foster reRobotic competitions are an excellent way to foster research and to attract students to technological areas (1). Roboticand competitions are an excellent way to areas foster (1). research to attract students to technological search and to attract students to technological areas (1). The robotic present problems search and tocompetitions attract students to standard technological areas that (1). The robotic competitions present standard problems that The robotic competitions present standard problems that can used as in order evaluate and The be robotic present can be usedcompetitions as a a benchmark, benchmark, in standard order to to problems evaluate that and can be used as a benchmark, in order to evaluate and to compare the performance of different approaches. Alcancompare be usedthe as performance a benchmark,of in order to evaluate and to different approaches. Alto compare the performance of different approaches. Although there are many robotic competitions (2) (3) (4) to compare of different approaches. though therethe areperformance many robotic competitions (2) (3) Al(4) though there are many robotic competitions (2) (3) (4) (5), there is the need to create new ones, in order to though there are many robotic competitions (2) (3) (5), there is the need to create new ones, in order (4) to (5), is to create new order to solve new aa prime (5), there there is the the need needThe to factory create environment new ones, ones, in inis to solve new challenges. challenges. The factory environment isorder prime solve challenges. The factory environment is candidate use in variety of solve new new to challenges. is aa prime prime candidate to use robots robotsThe in a afactory variety environment of tasks. tasks. A A competition competition candidate to robots in aa variety of where mobile robots are problems candidate to use use robots varietytransportation of tasks. tasks. A A competition competition where mobile robots areintackling tackling transportation problems where mobile robots are tackling transportation problems in the shop floor is a challenge that can foster where mobile robots are tackling transportation problems in the shop floor is a challenge that can foster new new adadin shop floor is that new advances service and manufacturing (6)(7)(8). in the the in shop floorrobots is aa challenge challenge that can can foster foster new The advances in service robots and manufacturing (6)(7)(8). The vances in service robots and manufacturing (6)(7)(8). The Robot@Factory an competition the vances in serviceis and manufacturing The Robot@Factory isrobots an official official competition of of(6)(7)(8). the Robotics Robotics Robot@Factory is official of Robotics Portuguese Open, presenting problems occur when Robot@Factory is an an official competition competition of the the Robotics Portuguese Open, presenting problems that that occur when Portuguese Open, presenting problems that occur using mobileOpen, robotspresenting to perform performproblems transportation tasks.when The Portuguese that occur when using mobile robots to transportation tasks. The using robots to perform transportation tasks. The robots must be able navigate, cooperate and to selfusing mobile mobile robots toto perform transportation tasks. The Fig. 1. Robotics Portuguese Open robots must be able to navigate, cooperate and to selfrobots be able cooperate and 1. Robotics Portuguese Open localize in factory to and robots must must able to to navigate, navigate, cooperate and to to selfselflocalize in an anbeemulated emulated factory plant, plant, to transport transport and Fig. Fig. Fig. 1. 1. Robotics Robotics Portuguese Portuguese Open Open localize in an emulated factory plant, to transport and handle materials in an efficient way. The introduction of localize in an emulated factory plant, to transport and handle materials in an efficient way. The introduction of competition. Then it is detailed a proposal of a Microhandle materials in an efficient way. The introduction of competition. Then it is detailed a proposal of a Microahandle downsized version of the the Robot@Factory is intended intended to to materials in an efficient way. The introduction of Factory a downsized version of Robot@Factory is competition. Then it is detailed aa some proposal of robot prototype and finally conclusions and competition. Then it is detailed proposal of aa MicroMicroahelp downsized version of the Robot@Factory is intended to Factory robot prototype and finally some conclusions and junior competitors to make the transition from the a downsized version of the Robot@Factory is intended to future help junior competitors to make the transition from the Factory robot prototype and finally some conclusions and work are pointed out. help junior competitors to make the transition from the Factory robot prototype and finally some conclusions and future work are pointed out. Junior Leagues to the senior competition Robot@Factory. help junior competitors to make the transition from the future work are pointed out. Junior Leagues to the senior competition Robot@Factory. future work are pointed out. Junior Leagues to the senior competition Robot@Factory. The downsized version of the Robot@Factory competition, Junior Leagues to the senior competition Robot@Factory. The downsized version of the Robot@Factory competition, The downsized of Robot@Factory the MicroFactory, reduces significantly costs competition, for competicompetiTheMicroFactory, downsized version version of the the Robot@Factory competition, the reduces significantly costs for 2. 2. ROBOT@FACTORY ROBOT@FACTORY COMPETITION COMPETITION the MicroFactory, reduces significantly costs for tors and also for the organization, when compared with 2. ROBOT@FACTORY COMPETITION the MicroFactory, reduces significantly costs for competicompetitors and also for the organization, when compared with 2. ROBOT@FACTORY COMPETITION tors and also for the organization, when compared with the A of 2006 of torsstandard and alsocompetition. for the organization, with the standard competition. A picture picture when of the the compared 2006 edition edition of In this section it is presented the Robot@Factory compethe standard competition. A picture of the 2006 edition of In this section it is presented the Robot@Factory compeRobotics Portuguese open can be in 1. the standard competition. picture of the 2006 edition of tition Robotics Portuguese open A can be seen seen in Figure Figure 1. In this section it is presented the Robot@Factory compedescription and the rules that teams must follow in In this section it is presented the Robot@Factory compeRobotics Portuguese open can be seen in Figure 1. tition description and the rules that teams must follow in Robotics Portuguese open can be seen in aFigure 1. tition description and the rules that teams must follow in The paper is organized as follows: After brief introducorder to qualify for participation. This competition is an tition to description and the rules that teams must follow in The paper is organized as follows: After a brief introduc- order qualify for participation. This competition is an The paper is organized as follows: After a brief introducorder to qualify for participation. This competition is an tion the is then Robotica, Main Robotics The paper is organized ascompetition follows: After a brief introducorder tocompetition qualify for of participation. This competition an tion the Robot@Factory Robot@Factory competition is described, described, then aa official official competition of Robotica, the the Main Robotics isPorPortion competition is then a official of Robotica, the Main Robotics Porproposal of version where it Competition, 2011. The official competition tion the the Robot@Factory Robot@Factory is described, described, official competition competition of since Robotica, Robotics Porproposal of its its downsized downsized competition version is is described, described, wherethen it are area tuguese tuguese Competition, since 2011. the TheMain official competition proposal of its downsized version is described, where it are tuguese Competition, since 2011. The official competition discussed its benefits, when compared with the standard arena is shown in Figure 2. proposal ofitsitsbenefits, downsized version is described, where it are arena tuguese since discussed when compared with the standard is Competition, shown in Figure 2. 2011. The official competition discussed discussed its its benefits, benefits, when when compared compared with with the the standard standard arena arena is is shown shown in in Figure Figure 2. 2. Copyright © 2016 121 2405-8963 © IFAC (International Federation of Automatic Control) Copyright © 2016, 2016 IFAC IFAC 121 Hosting by Elsevier Ltd. All rights reserved. Copyright ©under 2016 responsibility IFAC 121Control. Peer review of International Federation of Automatic Copyright © 2016 IFAC 121 10.1016/j.ifacol.2016.07.164
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2.6 Competition starting The robots must be placed in the closed park one hour before the start of each competition. Teams should not to have access to the robot until about 10 minutes before the start of their competition. There, the referees indicate the teams that should prepare the robot to start their competition. 2.7 Competition rounds Since this is a competition that can accept participants with different background, it must be differentiated in three rounds. Event organization can provide, for some rounds, an external localization system for robots. This system will identify the robots using a pattern that must be placed on top of each robot and can provide the position and orientation of the robot. Fig. 2. Competition arena. 2.1 Robot dimensions Each robot must fit within a cuboid of 45 x 40 x 35 cm. The robot must be completely autonomous and cannot establish any kind of communication with external systems that are not explicitly provided by the organization. 2.2 Competition arena The competition arena, shown in Figure 2, emulates a factory shop floor where there are warehouses and machinery. The dimensions of this area is 3.5 x 2.5 m. There are eight machines available and two warehouses. One of them is used as a raw material storage and the other one is used as a destination. 2.3 Machinery and warehouses description Each machine provides an area where the pieces should be placed in order to be processed by the machine. The robot must pick and place the part materials from the machine. While the part is placed in the machine it is processed and should not be removed. An RGB LED indicates that the machine is able to accept parts (light green), the machine is processing a part (yellow light), the part in this machine is already processed (white light) or that the machine is broken (blink red light). 2.4 The part materials The materials to be transported by the robots should respect standard dimensions, width and length corresponding to an Europallete 80 x 120 mm (1:10 scale), the height should have a value between 30 mm and 50 mm. Each piece has an LED showing an RGB color that identifies the type of material. When a part arrives to a machine, it can be processed and its color is changed in order to illustrate a different type of part. 2.5 Solving problems in the competition Team responsible can access the robot up to four times, if one of the robots is not expected to be able to recover. While robot comes out from the arena the time scheduling continues unchangeable. 122
First round The main purpose of the first round is to collect the pieces of the raw material warehouse and transport them to the end warehouse. The robot should transport the most parts it can from the warehouses. Second round The main purpose of the second round is to process some parts of the raw material. The raw material should be transported from the initial warehouse to the machinery, in order to be processed. When the processing task is ended, the parts should be transported to the final warehouse. Third round The main purpose of the third round is to sequentially distribute the parts through several machinery. Some parts collected from the raw material warehouse should be placed sequentially in more than one machine to process. Only after the completion of this operation the parts should be transported to the final warehouse. There will be three types of parts in operation. During this round some tracks may be partially or totally blocked. In this round teams are authorized to use two robot at the same time, the used robots must cooperate to perform its tasks. 3. MICROFACTORY COMPETITION The introduction of a downsized version of the standard Robot@Factory competition is intended to help junior competitors to make the transition from the Junior Leagues to the senior competition Robot@Factory. The downsized version of the Robot@Factory competition, the MicroFactory, reduces significantly costs for the competitors and also for the organization, when compared with the standard competition. The main differences from the Robot@Factory competition, when compared to its downsize proposal, are essentially the following items: • The dimensions reduce (both in the Arena as well as in robot). • In order to reduce complexity, for the organizers and competitors, the machines and part materials do not have leds to provide the robots information about their status. • Passive elements are used to indicate the status of the part materials, as described in subsection 3.2.
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Fig. 4. LegoTM part material
Fig. 3. Downsized robot arena with dimensions in mm 3.1 Competition Arena The arena dimensions are shown in Figure 3, the lines on the floor can be used by the robot to navigate in the arena. 3.2 The part material The part materials and the machines do not have information provided by leds, being the state of the part material identified by the number of marbles in the part material. Examples of part materials are shown in Figures 5 and 6, where two alternatives are shown, being possible the use of 3D print technology as well as the use of LegoTM . 3.3 Machinery and warehouses description
Fig. 5. 3D printed part material
The two, previously presented, prototyping alternatives (LegoTM and 3D print) are also possible to be used in the development of machines, raw material and final destination warehouses. An example of the LegoTM usage in a Machine prototyping is shown in Figure 6. The competition machine will be prototyped using 3D print technology, being provided with a system that drops marbles into the material parts when their status has to be changed. 4. MICROFACTORY ROBOT PROTOTYPE In the MicroFactory competition each team is free to prototype their own robot, as long as its fits within a cuboid of 20 x 20 x 20 cm, as alternative they can use an official robot provided by the organization. The official robot prototype was developed using an open source hardware and software arquitecture, being all its details provided to the teams by the organization. The prototyped mobile robot consists in small prototype, being presented in Figure 7, that uses inexpensive hardware, such as servo motors, an Arduino Uno platform, an infra-red detector array and For the sensor and actuator interface it was used an Arduino Servo and Sensor Shield. The robot was prototyped using 3D print technology, as an example the robot chassis 3D printer models is presented in Figure 8.
Fig. 6. Machine
In the next subsections the prototype sensors and actuators are described.
Encoders The used incremental encoders are an inexpensive piece of hardware that would not increase considerably
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4.1 Sensors Zumo reflectance sensor The robot is equipped with the Zumo (9) reflectance sensor, providing an easy way to add line sensing or edge detection. It features six separate reflectance sensors, each consisting of an IR emitter coupled with a phototransistor that responds based on how much emitter light is reflected back to it. The purpose of using the referred sensor is to sense and follow a line. A Zumo reflectance sensor array is shown in Figure 9. More information about this sensor can be found in (9).
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the cost of the robot prototype. It is based on IR emitters coupled with phototransistors, applied to obtain two signals in quadrature. The robot with encoders is shown in Figure 10.
Fig. 7. Robot prototype. Fig. 10. Robot with encoders. The use of incremental encoders it is only necessary to obtain the actuator model, prototypes with and without encoders are available. A compact wheel for the robot without encoders is shown in Figure 11 and a wheel prepared for the robot with encoders is shown in Figure 12.
Fig. 8. Robot prototype 3D Chassis printer model.
Fig. 11. Robot compact wheel.
4.2 Actuators The proposed robot actuators are servos, both for the fork as well as for the its locomotion. A servo motor is a complete assembly made of a small high RPM motor, gear reduction, H-Bridge and position control circuitry. If the servo is not modified it is used to produce a rotational position based on a Pulse Width Modulated (PWM) signal.
Fig. 9. Zumo reflectance sensor (9).
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of a2 ..a0 , b2 ..b0 . The total error, being the sum of the absolute differences, was used as the target function (11). The estimated parameters can be seen in Table 1. ω(d) =
a2 .d2 + a1 .d + a0 b2 .d2 + b1 .d + b0
Parameters a0 a1 a2 b0 b1 b2
(1)
Value -34.760E-6 -69.581E-3 488.777E-3 -29.663E-6 2.278E-3 -1.964
Table 1. Estimated parameters.
Fig. 12. Robot wheel prepared for encoders use. Locomotion actuator The robot locomotion actuator is the Futaba S3003 Servo. The Futaba S3003 servo motor has three inputs: PWM (white), power (red), and ground (black). Based on the PWM signal the servo will turn its shaft to a position within a range of approximately 200◦ . When a PWM command is given to the circuitry an error signal is produced. This error signal turns the motor in the appropriate direction. The motor gearing turns a position potentiometer, which gives a feedback signal to the position control circuitry. When the correct position is indicated by the potentiometer, the error signal becomes small enough, so the motor stops turning. For the proposed robot, continuous rotation is necessary, so the locomotions servo motors must be modified. This modification consists in disconnecting the position potentiometer from the gear train, setting the potentiometer for a known PWM signal and removing the angle stops from the motor shaft. Some offset developed by software is necessary to get the two motors to turn at the same speed. More detailed information of the Futaba S3003 servo motor and its modification can be found in (10). In order to obtain the actuator model it was necessary to know for each control signal the output velocity of each modified servomotor, incremental encoders were used for that purpose, the actuator was powered with 6 Volt. The control signal is the same as for a standard servo, only this time the length of the on time pulse will affect the speed and directions. For a certain pulse width the servo will stop. Values above or below will make the servo rotate faster in either direction. The signal (d), depicted in Figure 13, is the difference for the stopping pulse width. This value must be divided by 40000, in order to obtain the time in seconds. As there is a gearbox with an high ratio, the dynamic response is very fast. The most important aspect of the model is the non linearity introduced by the modified controller. This non linearity can be seen in Figure 13 where the steady state speed for a certain pulse width has a small dead zone and a non linear behavior as it approaches the maximum speed. In order to model these non linearities, equation 1, saturated for values inferior to zero, was estimated. Using the experimental speed measures the best fit was found by optimizing the values 125
Fig. 13. Futaba S3003 Model. In order to invert equation 1, equation 2 can be obtained. The solution for equation 2, corresponds to equation 3, resulting in a function with its domain from 0 to 5.955 Rad/s, that has as input a velocity and as output the servo control signal. (ωb2 − a2 )d2 + (ωb1 − a1 )d + ωb0 − a0 = 0 d=
−b ±
√
b2 − 4ac 2a
(2)
(3)
where: • a = ωb2 − a2
• b = ωb1 − a1
• c = ωb0 − a0
For an input inside the referred function’s domain, equation 3 returns two values, the chosen value must be equal or greater than 7 and less or equal than 293. Values from 0 to 6 are inside the dead zone and values superior to 293 correspond to the saturation zone. Fork actuator For the Fork it was used the T-Pro Mini Servo SG-90 9G without any modification, being shown in Figure 14 (12).
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ACKNOWLEDGEMENTS This work is financed by the ERDF European Regional Development Fund through the Operational Programme for Competitiveness and Internationalisation - COMPETE 2020 Programme, and by National Funds through the FCT Funda¸c˜ao para a Ciˆencia e a Tecnologia (Portuguese Foundation for Science and Technology) within project POCI-01-0145-FEDER-006961. REFERENCES [1]
Fig. 14. T-Pro Mini Servo SG-90 9G.
5. CONCLUSIONS AND FUTURE WORK The introduction of a downsized version of the Robot@Factory is intended to help junior competitors to make the transition from the Junior Leagues to the senior competition Robot@Factory. The Robot@Factory competition takes place in an emulated factory plant, where Automatic Guided Vehicles (AGVs) must cooperate to perform tasks. To accomplish their goals the AGVs must deal with localization, navigation, scheduling and cooperation problems, that must be solved autonomously. The downsized version of the Robot@Factory competition, the MicroFactory, reduces significantly costs for competitors and also for the organization, when compared with the standard competition. The introduction of passive elements in the Robot competition arena reduces complexity in competition setup implementation. The fact that the teams that do not implement hardware have access to a robot prototype provided by the organization is very important to promote the competition to a wider audience. The robot locomotion actuator is the Futaba S3003 Servo. For the proposed robot, continuous rotation is necessary, so the locomotion servo motors must be modified. This modification consists in disconnecting the position potentiometer from the gear train, setting the potentiometer for a known PWM signal and removing the angle stops from the motor shaft. Some offset developed by software is necessary to get the two motors to turn at the same speed. The presented sensor and actuator prototype description and accurate models provides the participating teams valuable knowledge, that can be very helpful in order to develop higher performance robot control software. As future work the authors intend to provide the official competition robot prototype with a sensor that gives the robot information concerning the part status, identifying the number marbles in each part and also to evaluate the effectiveness of the introduction of the new robot competition. 126
Almeida, L., Azevedo, J., Cardeira, C., Costa, P., Fonseca,P., Lima, P., Ribeiro, F., and Santos, V., Fostering advances in research, development and education in robotics. Proceedings of the 4th Portuguese conference in Automatic Control, 2000 [2] Browning, B., Bruce, J., Bowling, M., and Veloso, M., Ustp: Skills, tactics and plays for multi-robot control in adversarial environments. IEEE Journal of Control and Systems Engineering, 2005 [3] Lund, H. and Pagliarinis, L., Robocup jr. with lego mindstorms, International Conference on Robotics and Automation, San Francisco, CA, IEEE, 2000 [4] Nakanishi, R., Bruce, J., Murakami, K., Naruse, T., and Veloso, M., Cooperative 3-robot passing and shooting in the robocup small size league. Proceedings of the RoboCup Symposium, Bremen, Germany, 2006 [5] Ribeiro, F., Moutinho, I., Silva, P., Fraga, C., and Pereira, N., Controlling omni-directional wheels of a robocup msl autonomous mobile robot. In Scientific Meeting of the Portuguese Robotics Open, 2004 [6] Yuta, S., Asama, H., Thrun, S., Prassler, E., and Tsubouchi, T., Field and Service Robotics, Recent Advances in research and Applications. volume 24 of Springer Tracts in Advanced Robotics, Lake Yamanaka, Japan, 14-16 July 2003 [7] Arun N. Nambiar, Challenges in Sustainable Manufacturing. Proceedings of the 2010 International Conference on Industrial Engineering and Operations Management, Dhaka, Bangladesh, January 9-10, 2010 [8] Gon¸calves, J., Lima, J.,Costa, P.,Moreira, A (June 2012). Manufacturing Education and Training resorting to a new mobile robot competition. Flexible Automation Intelligent Manufacturing 2012 (Faim 12) Ferry Cruise Conference Helsinki-Stockholm-Helsinki doi:10.1109/ICNN.1993.298623 [9] Pololu http://www.pololu.com/product/1419 2014 [10] Montana State University, Futaba S3003 modification for continuous running, http://www.coe.montana.edu/ee/ecerover/servomod.html 2004 [11] Concei¸c˜ao, A., Moreira, A., Costa, P., Dynamic Parameters Identification of an Omni-directional Mobile Robot, Proceedings of the International Conference on Informatics in Control Automation and Robotics, 2006. [12] TowerPro SG90 Servo description and reviews http://www.servodatabase.com/servo/towerpro/sg90, 20015.
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Prototyping Small Robots for Junior Prototyping Small Robots for Junior Prototyping Small Robots for Junior Prototyping Small Robots for Junior Competitions: MicroFactory MicroFactory Case Case study Competitions: study Competitions: MicroFactory Case Competitions: MicroFactory Case study study
∗∗ ∗∗∗ ∗∗∗∗ ∗∗ J. Gon¸ ∗∗∗ P. Costa ∗∗∗∗ M. Silva c alves M. Silva c alves ∗∗ J. Gon¸ ∗∗∗ P. Costa ∗∗∗∗ M. Silva c alves ∗∗ J. Gon¸ ∗∗∗ P. Costa ∗∗∗∗ M. Silva J. Gon¸ calves P. Costa ∗ ∗ University of Porto, Portugal. University of Porto, Portugal. ∗ University of ∗ Email: [email protected] University of Porto, Porto, Portugal. Portugal. Email: [email protected] ∗∗ Email: [email protected] ∗∗ Polytechnic Institute Email: [email protected] Institute of of Porto, Porto, Portugal. Portugal. ∗∗ Polytechnic Institute of Porto, Portugal. ∗∗ Polytechnic Email: [email protected] Polytechnic Institute of Porto, Portugal. Email: [email protected] ∗∗∗ Email: [email protected] ∗∗∗ Polytechnic Institute of Bragan¸ c a and INESC-TEC, Portugal. Email: [email protected] Polytechnic Institute of Bragan¸ c a and INESC-TEC, Portugal. ∗∗∗ of Bragan¸ c a and INESC-TEC, Portugal. ∗∗∗ Polytechnic Institute Email: [email protected] Polytechnic Institute of Bragan¸ c a and INESC-TEC, Portugal. Email: [email protected] ∗∗∗∗ [email protected] ∗∗∗∗ UniversityEmail: of Porto and INESC-TEC, Portugal. [email protected] of Porto and INESC-TEC, Portugal. ∗∗∗∗ UniversityEmail: Porto and ∗∗∗∗ University of Email: University of [email protected] and INESC-TEC, INESC-TEC, Portugal. Portugal. Email: [email protected] Email: [email protected] Email: [email protected]
D. D. D. D.
∗ ∗ Neves Neves ∗ Neves Neves ∗
Abstract: Abstract: Abstract: In this paper it is discussed the proposal of aa small robot prototype to be applied in Abstract: In this paper it is discussed the proposal of small robot prototype to be applied in In this paper it is discussed the proposal of a small robot prototype to be applied in the MicroFactory competition, a downsized version of the Robot@Factory competition. The In this paper it is discussed the proposal version of a small robot prototype to be appliedThe in the MicroFactory competition, a downsized of the Robot@Factory competition. the MicroFactory competition, a downsized version of the Robot@Factory competition. The MicroFactory is to junior make the from the MicroFactory competition, a downsized version ofto Robot@Factory The MicroFactory is intended intended to help help junior competitors competitors tothe make the transition transitioncompetition. from the the Junior Junior MicroFactory is intended to junior to make from the Leagues to competition The Robot@Factory competition place MicroFactory intended to help help Robot@Factory. junior competitors competitors make the the transition transition from takes the Junior Junior Leagues to the theissenior senior competition Robot@Factory. Theto Robot@Factory competition takes place Leagues to the senior competition Robot@Factory. The Robot@Factory competition takes in an emulated factory plant, where Automatic Guided Vehicles (AGVs) must cooperate to Leagues to the senior competition Robot@Factory. The Robot@Factory competition takes place place in an emulated factory plant, where Automatic Guided Vehicles (AGVs) must cooperate to in an emulated factory plant, where Automatic Guided Vehicles (AGVs) must cooperate to perform tasks. To accomplish their goals the AGVs must deal with localization, navigation, in an emulated factory plant, their wheregoals Automatic Guided Vehicles (AGVs) must cooperate to perform tasks. To accomplish the AGVs must deal with localization, navigation, perform tasks. To accomplish their goals the AGVs must deal with localization, navigation, scheduling and problems, that must be perform tasks. To accomplish their goals AGVs mustautonomously. deal with localization, navigation, scheduling and cooperation cooperation problems, that the must be solved solved autonomously. scheduling and cooperation problems, that be autonomously. scheduling and cooperation problems, that must mustControl) be solved solved autonomously. © 2016, IFAC (International Federation of Automatic Hosting by Elsevier Ltd. All rights reserved. Keywords: Keywords: Keywords: Mobile robot competitions, competitions, AGVs, AGVs, Prototyping Prototyping Keywords: Mobile robot Mobile Mobile robot robot competitions, competitions, AGVs, AGVs, Prototyping Prototyping 1. INTRODUCTION 1. INTRODUCTION 1. 1. INTRODUCTION INTRODUCTION Robotic competitions are an excellent way to foster reRobotic competitions are an excellent way to foster reRobotic competitions are an excellent way to foster research and to attract students to technological areas (1). Roboticand competitions are an excellent way to areas foster (1). research to attract students to technological search and to attract students to technological areas (1). The robotic present problems search and tocompetitions attract students to standard technological areas that (1). The robotic competitions present standard problems that The robotic competitions present standard problems that can used as in order evaluate and The be robotic present can be usedcompetitions as a a benchmark, benchmark, in standard order to to problems evaluate that and can be used as a benchmark, in order to evaluate and to compare the performance of different approaches. Alcancompare be usedthe as performance a benchmark,of in order to evaluate and to different approaches. Alto compare the performance of different approaches. Although there are many robotic competitions (2) (3) (4) to compare of different approaches. though therethe areperformance many robotic competitions (2) (3) Al(4) though there are many robotic competitions (2) (3) (4) (5), there is the need to create new ones, in order to though there are many robotic competitions (2) (3) (5), there is the need to create new ones, in order (4) to (5), is to create new order to solve new aa prime (5), there there is the the need needThe to factory create environment new ones, ones, in inis to solve new challenges. challenges. The factory environment isorder prime solve challenges. The factory environment is candidate use in variety of solve new new to challenges. is aa prime prime candidate to use robots robotsThe in a afactory variety environment of tasks. tasks. A A competition competition candidate to robots in aa variety of where mobile robots are problems candidate to use use robots varietytransportation of tasks. tasks. A A competition competition where mobile robots areintackling tackling transportation problems where mobile robots are tackling transportation problems in the shop floor is a challenge that can foster where mobile robots are tackling transportation problems in the shop floor is a challenge that can foster new new adadin shop floor is that new advances service and manufacturing (6)(7)(8). in the the in shop floorrobots is aa challenge challenge that can can foster foster new The advances in service robots and manufacturing (6)(7)(8). The vances in service robots and manufacturing (6)(7)(8). The Robot@Factory an competition the vances in serviceis and manufacturing The Robot@Factory isrobots an official official competition of of(6)(7)(8). the Robotics Robotics Robot@Factory is official of Robotics Portuguese Open, presenting problems occur when Robot@Factory is an an official competition competition of the the Robotics Portuguese Open, presenting problems that that occur when Portuguese Open, presenting problems that occur using mobileOpen, robotspresenting to perform performproblems transportation tasks.when The Portuguese that occur when using mobile robots to transportation tasks. The using robots to perform transportation tasks. The robots must be able navigate, cooperate and to selfusing mobile mobile robots toto perform transportation tasks. The Fig. 1. Robotics Portuguese Open robots must be able to navigate, cooperate and to selfrobots be able cooperate and 1. Robotics Portuguese Open localize in factory to and robots must must able to to navigate, navigate, cooperate and to to selfselflocalize in an anbeemulated emulated factory plant, plant, to transport transport and Fig. Fig. Fig. 1. 1. Robotics Robotics Portuguese Portuguese Open Open localize in an emulated factory plant, to transport and handle materials in an efficient way. The introduction of localize in an emulated factory plant, to transport and handle materials in an efficient way. The introduction of competition. Then it is detailed a proposal of a Microhandle materials in an efficient way. The introduction of competition. Then it is detailed a proposal of a Microahandle downsized version of the the Robot@Factory is intended intended to to materials in an efficient way. The introduction of Factory a downsized version of Robot@Factory is competition. Then it is detailed aa some proposal of robot prototype and finally conclusions and competition. Then it is detailed proposal of aa MicroMicroahelp downsized version of the Robot@Factory is intended to Factory robot prototype and finally some conclusions and junior competitors to make the transition from the a downsized version of the Robot@Factory is intended to future help junior competitors to make the transition from the Factory robot prototype and finally some conclusions and work are pointed out. help junior competitors to make the transition from the Factory robot prototype and finally some conclusions and future work are pointed out. Junior Leagues to the senior competition Robot@Factory. help junior competitors to make the transition from the future work are pointed out. Junior Leagues to the senior competition Robot@Factory. future work are pointed out. Junior Leagues to the senior competition Robot@Factory. The downsized version of the Robot@Factory competition, Junior Leagues to the senior competition Robot@Factory. The downsized version of the Robot@Factory competition, The downsized of Robot@Factory the MicroFactory, reduces significantly costs competition, for competicompetiTheMicroFactory, downsized version version of the the Robot@Factory competition, the reduces significantly costs for 2. 2. ROBOT@FACTORY ROBOT@FACTORY COMPETITION COMPETITION the MicroFactory, reduces significantly costs for tors and also for the organization, when compared with 2. ROBOT@FACTORY COMPETITION the MicroFactory, reduces significantly costs for competicompetitors and also for the organization, when compared with 2. ROBOT@FACTORY COMPETITION tors and also for the organization, when compared with the A of 2006 of torsstandard and alsocompetition. for the organization, with the standard competition. A picture picture when of the the compared 2006 edition edition of In this section it is presented the Robot@Factory compethe standard competition. A picture of the 2006 edition of In this section it is presented the Robot@Factory compeRobotics Portuguese open can be in 1. the standard competition. picture of the 2006 edition of tition Robotics Portuguese open A can be seen seen in Figure Figure 1. In this section it is presented the Robot@Factory compedescription and the rules that teams must follow in In this section it is presented the Robot@Factory compeRobotics Portuguese open can be seen in Figure 1. tition description and the rules that teams must follow in Robotics Portuguese open can be seen in aFigure 1. tition description and the rules that teams must follow in The paper is organized as follows: After brief introducorder to qualify for participation. This competition is an tition to description and the rules that teams must follow in The paper is organized as follows: After a brief introduc- order qualify for participation. This competition is an The paper is organized as follows: After a brief introducorder to qualify for participation. This competition is an tion the is then Robotica, Main Robotics The paper is organized ascompetition follows: After a brief introducorder tocompetition qualify for of participation. This competition an tion the Robot@Factory Robot@Factory competition is described, described, then aa official official competition of Robotica, the the Main Robotics isPorPortion competition is then a official of Robotica, the Main Robotics Porproposal of version where it Competition, 2011. The official competition tion the the Robot@Factory Robot@Factory is described, described, official competition competition of since Robotica, Robotics Porproposal of its its downsized downsized competition version is is described, described, wherethen it are area tuguese tuguese Competition, since 2011. the TheMain official competition proposal of its downsized version is described, where it are tuguese Competition, since 2011. The official competition discussed its benefits, when compared with the standard arena is shown in Figure 2. proposal ofitsitsbenefits, downsized version is described, where it are arena tuguese since discussed when compared with the standard is Competition, shown in Figure 2. 2011. The official competition discussed discussed its its benefits, benefits, when when compared compared with with the the standard standard arena arena is is shown shown in in Figure Figure 2. 2. Copyright © 2016 121 2405-8963 © IFAC (International Federation of Automatic Control) Copyright © 2016, 2016 IFAC IFAC 121 Hosting by Elsevier Ltd. All rights reserved. Copyright ©under 2016 responsibility IFAC 121Control. Peer review of International Federation of Automatic Copyright © 2016 IFAC 121 10.1016/j.ifacol.2016.07.164
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2.6 Competition starting The robots must be placed in the closed park one hour before the start of each competition. Teams should not to have access to the robot until about 10 minutes before the start of their competition. There, the referees indicate the teams that should prepare the robot to start their competition. 2.7 Competition rounds Since this is a competition that can accept participants with different background, it must be differentiated in three rounds. Event organization can provide, for some rounds, an external localization system for robots. This system will identify the robots using a pattern that must be placed on top of each robot and can provide the position and orientation of the robot. Fig. 2. Competition arena. 2.1 Robot dimensions Each robot must fit within a cuboid of 45 x 40 x 35 cm. The robot must be completely autonomous and cannot establish any kind of communication with external systems that are not explicitly provided by the organization. 2.2 Competition arena The competition arena, shown in Figure 2, emulates a factory shop floor where there are warehouses and machinery. The dimensions of this area is 3.5 x 2.5 m. There are eight machines available and two warehouses. One of them is used as a raw material storage and the other one is used as a destination. 2.3 Machinery and warehouses description Each machine provides an area where the pieces should be placed in order to be processed by the machine. The robot must pick and place the part materials from the machine. While the part is placed in the machine it is processed and should not be removed. An RGB LED indicates that the machine is able to accept parts (light green), the machine is processing a part (yellow light), the part in this machine is already processed (white light) or that the machine is broken (blink red light). 2.4 The part materials The materials to be transported by the robots should respect standard dimensions, width and length corresponding to an Europallete 80 x 120 mm (1:10 scale), the height should have a value between 30 mm and 50 mm. Each piece has an LED showing an RGB color that identifies the type of material. When a part arrives to a machine, it can be processed and its color is changed in order to illustrate a different type of part. 2.5 Solving problems in the competition Team responsible can access the robot up to four times, if one of the robots is not expected to be able to recover. While robot comes out from the arena the time scheduling continues unchangeable. 122
First round The main purpose of the first round is to collect the pieces of the raw material warehouse and transport them to the end warehouse. The robot should transport the most parts it can from the warehouses. Second round The main purpose of the second round is to process some parts of the raw material. The raw material should be transported from the initial warehouse to the machinery, in order to be processed. When the processing task is ended, the parts should be transported to the final warehouse. Third round The main purpose of the third round is to sequentially distribute the parts through several machinery. Some parts collected from the raw material warehouse should be placed sequentially in more than one machine to process. Only after the completion of this operation the parts should be transported to the final warehouse. There will be three types of parts in operation. During this round some tracks may be partially or totally blocked. In this round teams are authorized to use two robot at the same time, the used robots must cooperate to perform its tasks. 3. MICROFACTORY COMPETITION The introduction of a downsized version of the standard Robot@Factory competition is intended to help junior competitors to make the transition from the Junior Leagues to the senior competition Robot@Factory. The downsized version of the Robot@Factory competition, the MicroFactory, reduces significantly costs for the competitors and also for the organization, when compared with the standard competition. The main differences from the Robot@Factory competition, when compared to its downsize proposal, are essentially the following items: • The dimensions reduce (both in the Arena as well as in robot). • In order to reduce complexity, for the organizers and competitors, the machines and part materials do not have leds to provide the robots information about their status. • Passive elements are used to indicate the status of the part materials, as described in subsection 3.2.
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Fig. 4. LegoTM part material
Fig. 3. Downsized robot arena with dimensions in mm 3.1 Competition Arena The arena dimensions are shown in Figure 3, the lines on the floor can be used by the robot to navigate in the arena. 3.2 The part material The part materials and the machines do not have information provided by leds, being the state of the part material identified by the number of marbles in the part material. Examples of part materials are shown in Figures 5 and 6, where two alternatives are shown, being possible the use of 3D print technology as well as the use of LegoTM . 3.3 Machinery and warehouses description
Fig. 5. 3D printed part material
The two, previously presented, prototyping alternatives (LegoTM and 3D print) are also possible to be used in the development of machines, raw material and final destination warehouses. An example of the LegoTM usage in a Machine prototyping is shown in Figure 6. The competition machine will be prototyped using 3D print technology, being provided with a system that drops marbles into the material parts when their status has to be changed. 4. MICROFACTORY ROBOT PROTOTYPE In the MicroFactory competition each team is free to prototype their own robot, as long as its fits within a cuboid of 20 x 20 x 20 cm, as alternative they can use an official robot provided by the organization. The official robot prototype was developed using an open source hardware and software arquitecture, being all its details provided to the teams by the organization. The prototyped mobile robot consists in small prototype, being presented in Figure 7, that uses inexpensive hardware, such as servo motors, an Arduino Uno platform, an infra-red detector array and For the sensor and actuator interface it was used an Arduino Servo and Sensor Shield. The robot was prototyped using 3D print technology, as an example the robot chassis 3D printer models is presented in Figure 8.
Fig. 6. Machine
In the next subsections the prototype sensors and actuators are described.
Encoders The used incremental encoders are an inexpensive piece of hardware that would not increase considerably
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4.1 Sensors Zumo reflectance sensor The robot is equipped with the Zumo (9) reflectance sensor, providing an easy way to add line sensing or edge detection. It features six separate reflectance sensors, each consisting of an IR emitter coupled with a phototransistor that responds based on how much emitter light is reflected back to it. The purpose of using the referred sensor is to sense and follow a line. A Zumo reflectance sensor array is shown in Figure 9. More information about this sensor can be found in (9).
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the cost of the robot prototype. It is based on IR emitters coupled with phototransistors, applied to obtain two signals in quadrature. The robot with encoders is shown in Figure 10.
Fig. 7. Robot prototype. Fig. 10. Robot with encoders. The use of incremental encoders it is only necessary to obtain the actuator model, prototypes with and without encoders are available. A compact wheel for the robot without encoders is shown in Figure 11 and a wheel prepared for the robot with encoders is shown in Figure 12.
Fig. 8. Robot prototype 3D Chassis printer model.
Fig. 11. Robot compact wheel.
4.2 Actuators The proposed robot actuators are servos, both for the fork as well as for the its locomotion. A servo motor is a complete assembly made of a small high RPM motor, gear reduction, H-Bridge and position control circuitry. If the servo is not modified it is used to produce a rotational position based on a Pulse Width Modulated (PWM) signal.
Fig. 9. Zumo reflectance sensor (9).
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of a2 ..a0 , b2 ..b0 . The total error, being the sum of the absolute differences, was used as the target function (11). The estimated parameters can be seen in Table 1. ω(d) =
a2 .d2 + a1 .d + a0 b2 .d2 + b1 .d + b0
Parameters a0 a1 a2 b0 b1 b2
(1)
Value -34.760E-6 -69.581E-3 488.777E-3 -29.663E-6 2.278E-3 -1.964
Table 1. Estimated parameters.
Fig. 12. Robot wheel prepared for encoders use. Locomotion actuator The robot locomotion actuator is the Futaba S3003 Servo. The Futaba S3003 servo motor has three inputs: PWM (white), power (red), and ground (black). Based on the PWM signal the servo will turn its shaft to a position within a range of approximately 200◦ . When a PWM command is given to the circuitry an error signal is produced. This error signal turns the motor in the appropriate direction. The motor gearing turns a position potentiometer, which gives a feedback signal to the position control circuitry. When the correct position is indicated by the potentiometer, the error signal becomes small enough, so the motor stops turning. For the proposed robot, continuous rotation is necessary, so the locomotions servo motors must be modified. This modification consists in disconnecting the position potentiometer from the gear train, setting the potentiometer for a known PWM signal and removing the angle stops from the motor shaft. Some offset developed by software is necessary to get the two motors to turn at the same speed. More detailed information of the Futaba S3003 servo motor and its modification can be found in (10). In order to obtain the actuator model it was necessary to know for each control signal the output velocity of each modified servomotor, incremental encoders were used for that purpose, the actuator was powered with 6 Volt. The control signal is the same as for a standard servo, only this time the length of the on time pulse will affect the speed and directions. For a certain pulse width the servo will stop. Values above or below will make the servo rotate faster in either direction. The signal (d), depicted in Figure 13, is the difference for the stopping pulse width. This value must be divided by 40000, in order to obtain the time in seconds. As there is a gearbox with an high ratio, the dynamic response is very fast. The most important aspect of the model is the non linearity introduced by the modified controller. This non linearity can be seen in Figure 13 where the steady state speed for a certain pulse width has a small dead zone and a non linear behavior as it approaches the maximum speed. In order to model these non linearities, equation 1, saturated for values inferior to zero, was estimated. Using the experimental speed measures the best fit was found by optimizing the values 125
Fig. 13. Futaba S3003 Model. In order to invert equation 1, equation 2 can be obtained. The solution for equation 2, corresponds to equation 3, resulting in a function with its domain from 0 to 5.955 Rad/s, that has as input a velocity and as output the servo control signal. (ωb2 − a2 )d2 + (ωb1 − a1 )d + ωb0 − a0 = 0 d=
−b ±
√
b2 − 4ac 2a
(2)
(3)
where: • a = ωb2 − a2
• b = ωb1 − a1
• c = ωb0 − a0
For an input inside the referred function’s domain, equation 3 returns two values, the chosen value must be equal or greater than 7 and less or equal than 293. Values from 0 to 6 are inside the dead zone and values superior to 293 correspond to the saturation zone. Fork actuator For the Fork it was used the T-Pro Mini Servo SG-90 9G without any modification, being shown in Figure 14 (12).
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ACKNOWLEDGEMENTS This work is financed by the ERDF European Regional Development Fund through the Operational Programme for Competitiveness and Internationalisation - COMPETE 2020 Programme, and by National Funds through the FCT Funda¸c˜ao para a Ciˆencia e a Tecnologia (Portuguese Foundation for Science and Technology) within project POCI-01-0145-FEDER-006961. REFERENCES [1]
Fig. 14. T-Pro Mini Servo SG-90 9G.
5. CONCLUSIONS AND FUTURE WORK The introduction of a downsized version of the Robot@Factory is intended to help junior competitors to make the transition from the Junior Leagues to the senior competition Robot@Factory. The Robot@Factory competition takes place in an emulated factory plant, where Automatic Guided Vehicles (AGVs) must cooperate to perform tasks. To accomplish their goals the AGVs must deal with localization, navigation, scheduling and cooperation problems, that must be solved autonomously. The downsized version of the Robot@Factory competition, the MicroFactory, reduces significantly costs for competitors and also for the organization, when compared with the standard competition. The introduction of passive elements in the Robot competition arena reduces complexity in competition setup implementation. The fact that the teams that do not implement hardware have access to a robot prototype provided by the organization is very important to promote the competition to a wider audience. The robot locomotion actuator is the Futaba S3003 Servo. For the proposed robot, continuous rotation is necessary, so the locomotion servo motors must be modified. This modification consists in disconnecting the position potentiometer from the gear train, setting the potentiometer for a known PWM signal and removing the angle stops from the motor shaft. Some offset developed by software is necessary to get the two motors to turn at the same speed. The presented sensor and actuator prototype description and accurate models provides the participating teams valuable knowledge, that can be very helpful in order to develop higher performance robot control software. As future work the authors intend to provide the official competition robot prototype with a sensor that gives the robot information concerning the part status, identifying the number marbles in each part and also to evaluate the effectiveness of the introduction of the new robot competition. 126
Almeida, L., Azevedo, J., Cardeira, C., Costa, P., Fonseca,P., Lima, P., Ribeiro, F., and Santos, V., Fostering advances in research, development and education in robotics. Proceedings of the 4th Portuguese conference in Automatic Control, 2000 [2] Browning, B., Bruce, J., Bowling, M., and Veloso, M., Ustp: Skills, tactics and plays for multi-robot control in adversarial environments. IEEE Journal of Control and Systems Engineering, 2005 [3] Lund, H. and Pagliarinis, L., Robocup jr. with lego mindstorms, International Conference on Robotics and Automation, San Francisco, CA, IEEE, 2000 [4] Nakanishi, R., Bruce, J., Murakami, K., Naruse, T., and Veloso, M., Cooperative 3-robot passing and shooting in the robocup small size league. Proceedings of the RoboCup Symposium, Bremen, Germany, 2006 [5] Ribeiro, F., Moutinho, I., Silva, P., Fraga, C., and Pereira, N., Controlling omni-directional wheels of a robocup msl autonomous mobile robot. In Scientific Meeting of the Portuguese Robotics Open, 2004 [6] Yuta, S., Asama, H., Thrun, S., Prassler, E., and Tsubouchi, T., Field and Service Robotics, Recent Advances in research and Applications. volume 24 of Springer Tracts in Advanced Robotics, Lake Yamanaka, Japan, 14-16 July 2003 [7] Arun N. Nambiar, Challenges in Sustainable Manufacturing. Proceedings of the 2010 International Conference on Industrial Engineering and Operations Management, Dhaka, Bangladesh, January 9-10, 2010 [8] Gon¸calves, J., Lima, J.,Costa, P.,Moreira, A (June 2012). Manufacturing Education and Training resorting to a new mobile robot competition. Flexible Automation Intelligent Manufacturing 2012 (Faim 12) Ferry Cruise Conference Helsinki-Stockholm-Helsinki doi:10.1109/ICNN.1993.298623 [9] Pololu http://www.pololu.com/product/1419 2014 [10] Montana State University, Futaba S3003 modification for continuous running, http://www.coe.montana.edu/ee/ecerover/servomod.html 2004 [11] Concei¸c˜ao, A., Moreira, A., Costa, P., Dynamic Parameters Identification of an Omni-directional Mobile Robot, Proceedings of the International Conference on Informatics in Control Automation and Robotics, 2006. [12] TowerPro SG90 Servo description and reviews http://www.servodatabase.com/servo/towerpro/sg90, 20015.