General IS

Input Shaping

Input Shaping is a feedforward control technique for reducing vibrations in computer controlled machine. The method works by creating a command signal that cancels its own vibration. That is, vibration caused by the first part of the command signal is canceled by vibration caused by the second part of the command.

Input shaping is implemented by convolving a sequence of impulses, an input shaper, with any desired command. The shaped command that results from the convolution is then used to drive the system. If the impulses in the shaper are chosen correctly, then the system will respond without vibration to any unshaped command. The amplitudes and time locations of the impulses are obtained from the system's natural frequencies and damping ratios. Shaping can be made very robust to errors in the system parameters. The key to the success of input shaping is the input shaper. The shaper can have wide ranging properties depending on the amplitudes and time locations of the impulses which compose the shaper. My research focuses on developing shapers with desired properties. Design parameters can include: robustness to modeling errors, rise-time, actuator limits, and mode ratios for multi-mode systems.

Input shaping has been used on the following types of hardware: Coordinate Measuring Machines, Wafer Steppers, Wafer Handling Robots, Drilling Machines, disk head testers, the training system for the Space Shuttle’s robotic arm, and the MACE experiment with flew on Endeavour in 1995.