Authors
Abstract
In present study, dynamic modeling and control of a tethered space robot system in trajectory tracking of its end effector is investigated. Considering variation of the tether length in the model, dynamics of the system is modeled using Lagrange’s method. Librational motion of the tether is controlled by adjusting the tether length similar to conventional manipulators,control of the robot is performed by its motors. It is clear that, in the trajectory tracking of the end effector, the tether length should be kept more or less constant, keeping them in a stable position. Limiting the tether length variation while using it as a tool for controlling the tether librational motion, is the main challenging part of the control system. To deal with this problem, a hybrid control system is proposed to control the system. A nonlinear model predictive control approach (NMPC) is utilized to control the tether librational motion and a modified computed torque method (CTM) is used to control the manipulator motion. Initially the NMPC controller is developed for a simple tethered satellite system. Then it is combined with the CTM controller. The proposed controller is employed to control motion of a space robot’s end effector on a predefined trajectory. Performance of the controller is then evaluated by numerical simulations.
Keywords
2. Nohomi, M., Nenchev, D. N., and Uchiyama, M., “Control of Atethered Robot System using a Spacecraft Mounted Manipulator”, AIAA Guidance Navigation- and-Control Conference, San-Diego, CA, 1996.
3. Zhao, Y., and Bai, Z. F., “Dynamics Analysis of Space Robot Manipulator with Joint Clearance”, Acta Astronautica Journal, Vol. 68, pp. 1147-1155, 2011.
4. Sasaki, S., Tanaka, K., Higuchi, K., Okuizumi, N., Kawasaki, S., Shinohara, N., Senda, K., and Ishimura, K., “A New Concept of Solar Power Satellite: Tethered-SPS”, Acta Astronautica Journal, Vol. 60, pp. 153-165, 2006.
5. Takeichi, N., “Geostationary Station Keeping Control of a Space Elevator During Initial Cable Deployment”, Acta Astronautica Journal, Vol. 70, pp. 85-94, 2012.
6. Woo, M. Y. P., “Planar Dynamics of Tethered Space Manipulators”, Master of Engineering Thesis, Department of Mechanical Engineering, McGill University, Montréal, Canada, 2003.
7. Nohomi, M., “Development of Space Tethered Autonomousrobotic Satellite”, Proceeding of 3rd International Conference on Recent Advances in Space Technologies, Istanbul: IEEE, pp. 462-467, 2007.
8. Zhai, G., Qiu, Y., Liang, B., Li, C., “Research of Capture Error and Error Compensate for Spacenet Capture Robot”, International Journal of Advanced Robotic Systems, Vol. 6, No. 2, pp. 467-472, 2009.
9. Woo, M. Y. P., and Misra, A. K., “Dynamics of a Tethered Space Manipulator”, AAS/AIAA Astrodynamics Specialist Conference, Big Sky, Montana, U.S.A., pp. AAS-03-534, 2003.
10. Nohomi, M., Nenchev, D. N., and Uchiyama, M., “Path Planning for a Tethered Space Robot”, International Conference on Robotics and Automation Albuquerque, New Mexico: IEEE, pp. 3062-3067, 1997.
11. Woo, M. Y. P., and Misra, A. K., “Kinematics and Dynamicsof Tethered Space Manipulators”, Proceedings of 11th National Conference on Machines and Mechanics, Dehli, pp. 101, 2003.
12. Schechter, H. B., “Dumbbell Librations in Elliptic Orbits”, AIAA Journal, Vol. 2, No. 6, pp. 1000-1003, 1964.
13. Williams, P., “Libration Control of Tethered Satellites in Elliptical Orbits”, Journal of Spacecraft and Rockets, Vol. 43, No. 2, pp. 476-479, 2006.
14. Misra, A. K., “Dynamics and Control of Tethered Satellite Systems”, Acta Astronautica, Vol. 63, pp. 1169-1177, 2008.
15. Misra, A. K., and Modi. V. J., “A Survey on the Dynamics and Control of Tethered Satellite Systems”, Advances in the Astronautical Sciences, Vol. 62, pp. 667-719, 1987.
16. Qin, S. J., and Badgwell, T. A.,“An Overview of Industrial Model Predictive Control Technology”, Chemical Process Control, AIChE Symposium Series, No. 316, pp. 232-256, 1996.
17. Lee, E. B., and Markus, L., Foundations of Optimal Control Theory, Wiley, New York, 1967.
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