Control of space robots with unactuated joints (Q2725382)

A planar four-link space robotic system (a three-link robot mounted on a space vehicle) with one passive joint (the last one) is considered. Because of the existence of two nonholonomic constraints of two different orders, it is difficult to implement the point-to-point control directly. Therefore the control strategy is divided into three phases: the actuated joints control phase, the unactuated joint control phase (shape phase), and the orientation phase. The first phase can be implemented easily by a linear feedback. A velocity-based averaging method is designed to control the unactuated joint at the shape phase. At the third phase, the system is similar to a well-investigated model, which leads to the required control law.