Non-Singular Terminal Sliding Mode Control for a Three-Link Manipulator with Variable Mass

Robotic manipulators represent one of the most useful tools to address repetitive tasks in the industrial environment. In the primary aluminum industry, for example, manipulators mounted on vehicles and directly controlled by human operators are routinely used to feed the potcells with fluoride and improve the metal generation process. In order to automatize these operations and limit human presence in hazardous environments, manipulators can be equipped with automatic motion control algorithms to perform the requested tasks. In this work, a solution to this problem is proposed, based on a non-singular terminal sliding mode control approach and compared with a classical sliding mode control algorithm. The devised solution turns out to be efficient and robust, and in the specific case, able to take into account a non-measurable mass variation in the manipulator links itself. Numerical simulations with a multibody tool are employed as a first assessment and validation of the designed controller.