Improving the control of two-mode flexible systems with input shaping
Manning, Raymond Charles
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Machine vibration leads to lower precision, efficiency, and safety. As a result, large sums of money and innumerable man-hours are spent in efforts to reduce vibration in machinery. A subclass of machinery that is widely used in industry is two-mode flexible systems. Cranes with double-pendulum dynamics and two-link flexible robotic arms are representative examples of two-mode flexible systems. In order to thoroughly understand these types of systems, a detailed study of double-pendulum cranes is preformed. The crane payload is considered to be a distributed mass. The parameters of the payload and the crane has important effects on the dynamic response. the effects are studied as a function of the parameters so that effective control methods can be developed. This thesis develops a technique for improving the control of two-mode flexible systems called input shaping. Input shaping is a control strategy that uses a series of impulses to modify the reference command to suppress unwanted vibration in a system. This thesis reviews several types of input shapers and presents a method for optimizing a robust input shaper called Specified Insensitivity input shapers using knowledge of amplitude contributions of each mode to the overall response. Simulations and experiments are presented to verify the new algorithm. Two human operator studies are presented to demonstrate the effectiveness of input shaping when used in conjunction with distributed crane payloads, such as cargo containers. One study investigates the improvement in efficiency when using input shaping and the differences in efficiency between input shapers. The other study investigates operator learning when moving a payload with unshaped and shaped commands.