A method is presented for generating shaped command inputs which significantly reduce or eliminate endpoint vibration. Desired system inputs are altered so that the system completes the requested move without residual vibration. A short move time penalty is incurred (on the order of one period of the first mode of vibration). The preshaping technique is robust under system parameter uncertainty and may be applied to both open and closed loop systems. The Draper Laboratory’s Space Shuttle Remote Manipulator System simulator (DRS) is used to evaluate the method. Results show a factor of 25 reduction in endpoint residual vibration for typical moves of the DRS.

1S. KEY WORDS (Continue on reverse side If necessary and identify by block number) vibrations oscillations teleoperators flexible manipulators 20. ABSTRACT (Continue n reverse side It necosesw and Identity by block number) See back. DD , Al M 1473 EDITION OF I NOV SISOBSOLETE UNCLASSIFIED S/N 0.02-014-6601 SECURITY CLASSIFICATION OF TNIS PAGE

This paper describes a method for limiting vibration in flexible systems by shaping the input to the system. Unlike most previous input shaping strategies, this method does not require a precise system model or lengthy numerical computation; only estimates of the system natural frequency and damping ratio are required. The effectiveness of this method when there are errors in the system model is explored and quantified. Next, an algorithm is presented, which, given an upper bound on acceptable residual vibration amplitude, determines a shaping strategy that is insensitive to errors in the estimate of the natural frequency. Finally, performance predictions are compared to hardware experiments.

Input shaping reduces residual vibration in computer controlled machines by convolving a sequence of impulses with a desired system command. The resulting shaped input is then used to drive the system. The impulse sequence has traditionally contained only positively valued impulses. However, when the impulses are allowed to have negative amplitudes, the rise time can be improved. Unfortunately, excitation of unmodeled high modes and overcurrenting of the actuators may accompany the improved rise time. Solutions to the problem of high-mode excitation and overcurrenting are presented. Furthermore, a simple look-up method is presented that facilitates the design of negative input shapers. The performance of negative shapers is evaluated experimentally on two systems; one driven by a piezo actuator and the other equipped with DC motors.

No abstract

This paper evduates a new signal generation technique for commanding high-performance machines to move without exciting residual vibration.Because the technique behaves like a filter, it is compared to a variety of filtering techniques. The new input-shaping method is shown to perform more effectively than any of these filters.

Input shaping is a method for reducing residual vibrations in computer-controlled machines. Vibration is eliminated by convolving an input shaper, which is a sequence of impulses, with a desired system command to produce a shaped input. The shaped input then becomes the command to the system. Requiring the vibration reduction to be robust to modeling errors and system nonlinearities is critical to the success of the shaping process on any real system, Input shapers can be made very insensitive to parameter uncertainty; however, increasing robustness usually increases system delays. A design process is presented that generates input shapers with insensitivity-to-time-delay ratios that are much larger than traditionally designed input shapers. The advantages of the new shapers are demonstrated with computer simulations and their performance is verified with experimental results from the MIT Middeck Active Control Experiment, which was performed on board the Space Shuttle Endeavor.

No abstract