Experimental Verification of Vibration Reduction in Flexible Spacecraft Using Input Shaping

The performance of many spacecraft can be improved by using closed-loop control and command-shaping techniques. However, because little information exists about the operation of controlled structures in zero gravity, it is dife cult for designers to anticipate and place cone dence in the on-orbit performance of their ground-based control designs. To address this issue, the middeck active control experiment was conducted aboard the Space Shuttle Endeavor in March of 1995. The results of the command shaping experiments implemented during the mission are presented, and guidelines forusing command shaping to suppress unwanted vibration in e exible space structures are proposed. HE combination of stringent performance specie cations and lightly damped structural modes makes the effective operation of many space systems vulnerable to vibration. To attack this problem, closed-loop control and open-loop command-shaping techniques are often enlisted. However, with only ground-based testing available prior to on-orbit implementation, uncertainty about zerogravity(0-g) behavior can hamper the success of these 0- g control designs. The Massachusetts Institute of Technology (MIT) middeck activecontrolexperiment (MACE)isaSpaceShuttlee ightexperiment designed to expose critical issues associated with the design of controllers and shaped commands for 0 g. As part of this experiment, data were collected from a e exible structure on-orbit, and results illustrated that both the control and command-shaping strategies employed on the test article could effectively reduce problematic vibration. Additionally, as a result of careful ground-based modeling efforts, predictions of 0- g behavior were accurate enough to achieve high-performance control and command shaping without on-orbit redesign. After introducing the MIT MACE project and the MACEcommand-shaping efforts, this paper presents the results from a specie c subset of the mission experiments: the MACE input shaping tests. Based on these results, key points are summarized and conclusions are drawn.

[1]  Warren P. Seering,et al.  An extension of command shaping methods for controlling residual vibration using frequency sampling , 1992, Proceedings 1992 IEEE International Conference on Robotics and Automation.

[2]  Warren P. Seering,et al.  A zero-placement technique for designing shaped inputs to suppress multiple-mode vibration , 1994, Proceedings of 1994 American Control Conference - ACC '94.

[3]  Warren P. Seering,et al.  Preshaping Command Inputs to Reduce System Vibration , 1990 .

[4]  Warren P. Seering,et al.  Residual Vibration Reduction Using Vector Diagrams to Generate Shaped Inputs , 1994 .

[5]  Qiang Liu,et al.  Robust Time-Optimal Control of Uncertain Flexible Spacecraft , 1992 .

[6]  Jonathan P. How,et al.  Overview of Closed Loop Results for MACE , 1996 .

[7]  R. L. Farrenkopf.  Optimal Open-Loop Maneuver Profiles for Flexible Spacecraft , 1979 .

[8]  J. Junkins,et al.  Optimal Large-Angle Single-Axis Rotational Maneuvers of Flexible Spacecraft , 1980 .

[9]  Wayne J. Book,et al.  Eliminating multiple modes of vibration in a flexible manipulator , 1993, [1993] Proceedings IEEE International Conference on Robotics and Automation.

[10]  Tarunraj Singh,et al.  Robust time-optimal control - Frequency domain approach , 1994 .

[11]  Jonathan P. How,et al.  Finite element model based robust controllers for the MIT Middeck Active Control Experiment (MACE) , 1994, Proceedings of 1994 American Control Conference - ACC '94.

[12]  Jonathan P. How,et al.  A comparison of robust control techniques for uncertain structural systems , 1994 .

[13]  Anthony Tzes,et al.  Input preshaping with frequency domain information for flexible-link manipulator control , 1989 .

[14]  Kenneth W. Chang.  Shaping Inputs to Reduce Vibration in Flexible Space Structures , 1992 .

[15]  C. Swigert.  Shaped Torque Techniques , 1980 .

[16]  Jonathan P. How,et al.  Experimental Comparison of Robust H Control Techniques for Uncertain Structural Systems , 1997 .

[17]  Roger M. Glaese,et al.  Derivation of 0-g structural control models from analysis and 1-G experimentation , 1995 .