(Dr. William Singhose, advisor)

"Input Shaping for Telerobotic Manipulators"

Abstract

When a flexible system is moved it has a natural tendency to vibrate, which can cause problems for the operator of a telerobotic system. The vibration can cause the system to damage itself, other objects, or people. It can also make tasks, such as accurate positioning of the endpoint, difficult. To avoid these problems, the system must be moved slowly, lowering productivity. Therefore it is advantageous to reduce the level of vibration caused when flexible structures are moved, while maintaining a desirable speed, so that productivity and safety can be increased.

One way to reduce vibration is to modify the system’s reference command. This thesis demonstrates the effectiveness of input shaping, a type of command modifier, for reducing residual vibration in telerobotic manipulators. Two concerns with telerobotic manipulators are addressed as they relate to input shaping: reducing both high and low frequency vibration and making the rise time of the system as fast as possible. These concerns relate to two of the tradeoffs associated with input shaping: the tradeoff between system rise time and high mode vibration and the tradeoff between rise time and settling time. Input shaping decreases the settling time of the system by limiting the residual vibration, but increases the rise time of the system and thus causes a lag in the system. Certain input shapers can be created that decrease the rise time, but they may also amplify high mode vibration. Two new methods of input shaping are presented that help to control these tradeoffs. The High Mode Limiting (HML) shaper allows a fast rise time to be obtained while high mode vibration is limited. The Reduced-Perceived-Lag (RPL) shaper is able to reduce the system rise time by increasing settling time. Experimental results confirm the expected performance of these shapers.