Comments on "Force/motion control of constrained robots using sliding mode"

In Su, Leung, and Zhou (1992), the authors attempt to use sliding mode control for the simultaneous position and force control of a constrained robot manipulator. They assert that their control law, along with inclusion of the constraint force error in the definition of the sliding surface, produces asymptotically stable force tracking error. However, a separate force control law must be defined and a separate stability analysis performed to determine the behavior of the force tracking error. The authors address errors in the force control stability analysis presented in the above paper.<>