Study of robotic manipulators subjected to base disturbances

Abstract

Manipulators mounted on moving platforms have many practical applications. Unlike industrial manipulators, which operate in highly structured environments, the mobile manipulator is subject to arbitrary base motion disturbances which create control problems and degrade performance. Previous research demonstrated that conventional controllers were unable to compensate for the base motion disturbances. This thesis demonstrates a control strategy to compensate for base motion. A planar, three degree of freedom manipulator is used to perform a typical application. Both an uncoupled and a coupled PD controller are designed which result in satisfactory performance when the manipulator's base is stationary, but which fail to acceptably control the manipulator with the base moving. A compensator is designed which utilizes base motion disturbance measurements. The manipulator with either PD controller, using the sensory base information, can successfully perform the task. The compensator is demonstrated experimentally using a PUMA 250 robot mounted on a mobile platform. Keywords: equations of motion; robot design.