Researches On Complex Systems By Sliding Mode Control Strategy And Application To Robot

Complex system,as the very important one of the control systems and the hot researching issue,draws the close attentions of scholars in this area.Sliding mode control technique,which shows its more and more significant value in control engineering,shall be endeavored to be further broadened and applied to the complex system.Based on the sliding mode method,the coupled disturbance reconstruction,trajectory tracking,protection and fault tolerant control problems on complex systems,including nonlinear system,singular system and robot system,are studied in this dissertation.Different with conventional application areas of sliding mode observer approach,in this dissertation,it is firstly broadened to a class of nonlinear system.Via technical transformation,the nonlinear system with time-varying coupled disturbances and unmeasured system states is firstly transformed into the equal decoupled form and then augmented into the descriptor form.Upon the descriptor model,the sliding mode observer is designed that the coupled disturbance is reconstructed.The criterium about stability analysis of the observation error system is given.The bounded constraint in the sliding mode observer is solved by the LMI method.Two numerical simulations are offered to examine the scheme of this dissertation.With the estimated states obtained from the sliding mode observer and the amplitude values of the disturbances,a sliding mode controller is firstly designed,such that the desired trajectory can be tracked even disturbance exists and a partial of the system state is not measured.To be more accurate while tracking the desired trajectory,an advanced sliding mode controller and a state-feedback based compensation controller are then designed.These three controllers are compared with each other by two numerical simulations with the same parameters.The three trajectory controllers can avoid the inverse calculation of inertial matrix when they are used to track the referenced trajectory in robot,and are with the ability of fault tolerant.On the basis of above two points,the protective framework for the nonlinear robot system is studied.With the disturbance reconstruction approach provided,the torque disturbance can be reconstructed,such that a event trigger based protective framework is designed: the robot can track the desired trajectory well when it encounters weak disturbance and the event is not triggered,but it can protect itself when it encounters strong disturbance and the event is triggered.In the presented reaction strategies,the position of the obstacle disturbance is considered seriously: when the obstacle position is not available and the event is triggered,the control input is bounded such that the robot is avoided to be further damaged;while the obstacle position is available and the event is triggered,the trajectory is modified such that the motion system can decrease the damage and even flee away from 'danger'.Two numerical simulations are provided to examine the effectiveness of the protective reaction strategies.And,the sliding mode observer method is applied to the area of singular stochastic system.The disturbance estimation and fault tolerant control issues for singular stochastic system are considered,and the sensor and actuator faults are taken into account simultaneously.Via twice equal transformations,the original descriptor stochastic system is augmented into a new descriptor system where the system state and faults are put into the new system state.Upon the new descriptor system model,a novel sliding mode observer with two discontinuous functions is designed.By the estimated system state and actuator fault,a state feedback based compensation controller is designed.The theorems on examining the effectiveness of the observer and controller are offered.Via one numerical simulation,the scheme of sliding mode observer and compensation controller is testified.To show the engineering values of relevant theoretical results above,experiments on the 2-DOF and 3-DOF robot manipulators are offered.The trajectory tracking results are examined on the 3-DOF robot manipulator.The protective schemes are testified with the experiments on 2-DOF robot manipulator.Through the whole dissertation,three basic techniques are taken: Sliding mode observer method is the first technique.The coupled disturbance is reconstructed by the sliding mode observe approach.The desired trajectory is followed by the controllers designed with the estimated states obtained from the sliding mode observer.All the three trajectory tracking controllers,the basic sliding mode controller,the advanced sliding mode controller and the sate-feedback controller depend on the results of sliding mode observer.In the protection framework,the sliding mode observer is the basis for the reconstruction of disturbance and the estimation of the system state.In the singular stochastic system,the sliding mode observer is also used to estimate the faults and full system state.Besides the sliding mode technique,the singular augment technique is the another one used mostly in this dissertation.Based on this technique the nonlinear system is firstly transformed into the descriptor form and then changed into the new descriptor form such that the sliding mode observer method can be applied in this systems that not proper for the sliding mode method.The decouple transformation technique is also used many times,which offers convenience for the reconstruction of coupled disturbance and trajectory tracking.And,for the motion systems modelled by the Euler-Lagrange equation,the controller based on this idea,on one aspect,can employ the popular schemes used in linear areas directly,on the other aspect,can simplify the calculation process by avoiding the inverse calculation of inertia matrix.