Abstract: A novel intelligent predictive algorithm is proposed for unknown enviroments,and is applied to robotic force tracking control.According to the contact trajectory between the end-effector of the robot manipulator and the unknown constraint environment,the reference trajectory of the impedance controller is predicted intelligently by fuzzy reasoning.Meanwhile,it is tuned by reference scale factor depending upon the change of force error to accommodate change of the unknown stiffness.Moreover,impedance model parameters are adjusted fuzzily to reduce the force errors in the constrained motion and improve the global force control performance.Simulation results show the effectiveness of the scheme.