The Research On Sliding Mode Variable Structure Control Applied To Hybird-Driven Five-Bar Mechanism

The main feature of hybrid-driven five-bar linkage is to combine the motion of a large constant velocity motor with a small servomotor via a two degree of freedom mechanism, where the constant speed motor provides main torque and motion requirements, while the servomotor contributes to modulations on this motion. It is well known that the hybrid-driven five-bar linkage is a very complicated MIMO nonlinear system with time-varying strong-coupling and nonlinear dynamic characteristics, so the control for such a system is quite difficult;we have to face many existed uncertainties of hybrid-driven five-bar linkage. The sliding mode variable structure control (VSC) has distinct, ideal robustness and holds the invariance for the change of system parameters, outside disturbance and uncertainty of the system. Its algorithm is very simple. So VSC is fiting for the hybrid-driven five-bar linkage.But VSC has flaw, which is that after the system state getting to the sliding mode phase, it will produce high frequency chattering around the sliding plane. In the meantime, the control torque of the system will also produce high frequency chattering.The chattering phenomenon of VSC is studied in this dissertation. We applied the main methods in existence to eliminate the chattering to the VSC of the hybrid-driven five-bar linkage. Simulation results show that the relation between chattering phenomenon and control precision is conflict. .When the chattering phenomenon is restrained, the position error of the input angle is rather large. It is necessary to research new methods that the control precision is improved ulteriorly when the chattering phenomenon is restrained. The dissertation developed an improved method, which is known as improved boundary layer solution, the better demand for chattering reduced and control precision can be achieved. In addition, for the case when system state is getting to the sliding mode the control plane is non robustness, a fuzzy sliding modevariable structure control is proposed, which introduces fuzyy logic and whole sliding mode variable structure control theory into the controller design.The simulations of these methods are performed with computer language MATLAB respectively. The results show that the new methods are feasible and effective.