Independent Joint Sliding Mode Control of a Humanoid Robot Arm

The dynamic model of a humanoid robot arm with seven degrees of freedom (DOF) is highly nonlinear and complicated. A traditional controller is difficult to control it. In this paper, an independent joint sliding mode control (IJSMC) with gravity compensation is proposed to control a 7 DOF humanoid robot arm subject to parameter variations and external disturbances. The proposed controller possesses not only the sliding mode control like robustness but also the independent joint control like simplicity. In addition, it can be easily implemented. The global asymptotic stability is guaranteed by Lyaunov approach, and the input chattering phenomenon is handled by using boundary layer technology. To evaluate the tracking performance, the proposed controller is first applied to a two-link robot arm through simulations. The simulation results indicated that the proposed controller is better than those of both computed torque model-based and convectional independent joint PID controllers. Finally, the proposed controller is successfully applied to a 7 DOF humanoid robot arm through dynamic simulations using the ADAMS and Matlab/Simulink softwares.