Robust Sliding Mode Based on Partial Feedback Linearization Control for Underactuated Robot Manipulator

In several sectors, manipulator robots are extensively employed to perform various repetitive or dangerous tasks. On the other side of the coin, those robot arms are embedded with controlled actuators which one or more of them may fail and cause accidents in the workspace environment. In consequence, the system becomes underactuated having active and passive joints. In this case, the controller is no longer working adequately and it must be changed to be suitable for underactuated robots. As a result, there are two different cases; The first one consists of engaging the brakes of the passive joint when the fault appears in order to maintain its position at a fixed one. And the second one is when the brakes aren’t engaged and the passive joint rotates freely. For this purpose, a robust fault-tolerant method is designed by merging the Sliding Mode Control and the Partial Feedback Linearization Control to track a desired trajectory using an underactuated manipulator with a free or fixed defective joint actuator. Afterwards, a robot with a fourth passive joint was subjected to a co-simulation study conducted in Gazebo applying the proposed control method which was programmed using Matlab&Simulink.