Experimental investigation of a 5-DOF robot arm with sliding mode control

Hyper-redundant manipulators offer the ability to move within physically constrained spaces, which can be of particular benefit; e.g. inspection and maintenance in hazardous or otherwise hard-to-access environments. However, being comprised of several links joined end-to-end, they can exhibit rather complex kinematics, low values of flexural stiffness and fundamental natural frequency, high internal forces, friction and backlash. For these reasons, it can be difficult to obtain rapid, accurate and robust control of their movement. This paper describes the implementation of firstly PID and then sliding mode control on a five-link robot. Sliding mode control is shown to be superior, particularly in response to gravitational loads. Chattering and control signal switching effort were successfully suppressed via incorporation of a modified error-dependent switching gain.