TIME-OPTIMAL NEGATIVE INPUT SHAPERS

Input shaping reduces residual vibration in computer controlled machin es by convolving a sequence of impulses with a desired system command. The resulting shaped input is then used to drive the system. The impu lse sequence has traditionally contained only positively valued impuls es. However, when the impulses are allowed to have negative amplitudes , the rise time cart be improved. Unfortunately, excitation of unmodel ed high modes and overcurrenting of the actuators may accompany the im proved 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 sys tems; one driven by a piezo actuator and the other equipped with DC mo tors.