How to compensate stick-slip friction in neural velocity force control (NVFC) for industrial manipulators

We present a new design of hybrid force/position control NVFC capable of friction-compensation, which is a mandatory requirement in industrial applications for precise tracking of hard surfaces with desired contact force. The control architecture consists of an outer-loop velocity controller and an inner-loop adaptive hybrid force/position controller, which compensates the friction of the manipulators joints, significantly improving the force tracking performance during slow movements. The cascaded velocity controller ensures the precise approach during neural force/position control with a reduced bounce into the unknown surface, which is a demanding requirement for tasks like deburring or chamfering. The resulting performance of the force control system is illustrated in simulations, and is consistent with velocity/force control experiments on a 6-DOF industrial manipulator controlled with a PC-based real-time control system