In order to improve the trajectory tracking precision and the vibration suppression capability of flexible joint robots, a passivity theory based flexible joint controller is proposed. The controller is verified and simplified in Simulink environment in order to make it more suitable for the robot with multiple degrees of freedom (DoF). Experiments are conducted on a 7-DoF robot with DSP+FPGAs structure, and the nonlinear and linear parts are calculatd in digital signal processor (DSP) and field programmable gate array (FPGA) separately, which avoids the performance change of the joint controller due to the increasing DoF. The experiment results show that comparing with the PD (proportional-derivative) controller, the proposed controller has the advantages of lower torque fluctuation, faster vibration suppression and higher static accuracy.
[1] Ott C. Cartesian impedance control of flexible joint manipulators[D]. Saarbrücken, Germany: Saarland University, 2005.[2] Albu-Schaffer A, Ott C, Hirzinger G. A passivity based Cartesian impedance controller for flexible joint robots——Part II: Full state feedback, impedance design and experiments[C]//IEEE International Conference on Robotics and Automation. Piscataway, NJ, USA: IEEE, 2004: 2666-2672.[3] Albu-Schaffer A, Ott C, Hirzinger G. A unified passivity-based control framework for position, torque and impedance control of flexible joint robots[J]. International Journal of Robotics Research, 2007, 26(1): 23-39. [4] Ott C, Albu-Schaffer A, Kugi A, et al. A passivity based Cartesian impedance controller for flexible joint robots——Part I: Torque feedback and gravity compensation[C]//IEEE International Conference on Robotics and Automation. Piscataway, NJ, USA: IEEE, 2004: 2659-2665.[5] Ott C, Albu-Schaffer A, Kugi A, et al. On the passivity-based impedance control of flexible joint robots[J]. IEEE Transactions on Robotics, 2008, 24(2): 416-429. [6] Monmasson E, Cirstea M N. FPGA design methodology for industrial control systems——A review[J]. IEEE Transactions on Industrial Electronics, 2007, 54(4): 1824-1842. [7] Naouar M W, Naassani A A, Monmasson E, et al. FPGA-based predictive current controller for synchronous machine speed drive[J]. IEEE Transactions on Power Electronics, 2008, 23(4): 2115-2126. [8] Naouar M W, Monmasson E, Naassani A A, et al. FPGA-based current controllers for AC machine drives——A review[J]. IEEE Transactions on Industrial Electronics, 2007, 54(4): 1907-1925. [9] Zhou Z Y, Li T C, Takahashi T, et al. FPGA realization of a high-performance servo controller for PMSM[C]//19th Annual IEEE Applied Power Electronics Conference and Exposition. Piscataway, NJ, USA: IEEE, 2004: 1604-1609.[10] Shao X Y, Sun D. Development of a new robot controller architecture with FPGA-based IC design for improved high-speed performance[J]. IEEE Transactions on Industrial Informatics, 2007, 3(4): 312-321. [11] 倪风雷,刘宏,金明河,等.基于FPGA的高性能轻型臂机器人关节位置伺服系统[J].伺服控制,2005(6): 32-35. Ni F L, Liu H, Jin M H, et al. An FPGA based position servo system for high-performance light-weight manipulators[J]. Servo Control, 2005(6): 32-35.[12] Huang J B, Xie Z W, Liu H, et al. DSP/FPGA-based controller architecture for flexible joint robot with enhanced impedance performance[J]. Journal of Intelligent and Robotic Systems: Theory and Applications, 2008, 53(3): 247-261. [13] Spong M W. Modeling and control of elastic joint robots[J]. ASME Journal of Dynamic Systems, Measurement and Control, 1987, 109(4): 310-319. [14] Kelly R, Ortega R, Ailon A, et al. Global regulation of flexible joint robots using approximate differentiation[J]. IEEE Transactions on Automatic Control, 1994, 39(6): 1222-1224. [15] 周兆勇,李铁才,高桥敏男. 基于矢量控制的高性能交流电机速度伺服控制器的FPGA实现[J].中国电机工程学报,2004,24(5): 168-173. Zhou Z Y, Li T C, Takahashi T. FPGA implementation of the high-performance vector-controlled speed servo controller for AC drivers[J]. Proceedings of the Chinese Society for Electrical Engineering, 2004, 24(5): 168-173.[16] 胡寿松.自动控制原理[M].4版.北京:科学出版社,2001: 325-326. Hu S S. The principle of automatic control[M]. 4th ed. Beijing: Science Press, 2001: 325-326.