The sliding mode variable structure control for spherical 2-DOF robots was proposed on the basis of kinematical and dynamical models. The mechanism and dynamic model for spherical 2-DOF robot were described. The exponential reaching law for determining additional compensation torque was introduced, and then the control algorithm of spherical 2-DOF robots was established. The influence of applied force, mass, moment of inertia and control parameters on the control accuracy and stability of spherical 2-DOF robots was studied. The example of simulation control for spherical 2-DOF robots was undertaken and the result showed that the method is effective. The oscillation of system can be avoided, and then stability and good robustness of system can be kept and the high accuracy of system can be obtained by choosing appropriate parameters.
