Barrier Function-Based Adaptive Sliding-Mode Control And Its Application To Active Suspension Systems

Most of the practical applications involve nonlinear systems,and due to the increasing complexity of controlled objects,there are often various uncertainties in such systems,such as model errors,parameter changes,and external disturbances.It makes the modeling and control of these nonlinear systems very difficult,and its steady-state performance,transient performance and robustness are difficult to guarantee.In order to solve these problems,many advanced control schemes have been proposed,in which sliding mode control is widely applied to various fields because of its robustness and ease of implementation.However,the use of sliding mode control requires knowledge of the upper bound of uncertainties,and its main disadvantage is that the gain is easily overestimated and chattered.Therefore,this paper studies a model-free adaptive sliding mode control based on the barrier function.The main research contents of this paper include:For a class of second-order nonlinear systems with uncertainties,firstly,the time delay estimation method is used to estimate the system model,and the influence of model errors and parameters variation in the system is eliminated,and simple and efficient model-free control is realized.Secondly,a class of barrier functions is defined to design adaptive sliding mode control laws based on barrier functions.The adaptive strategy can ensure that the system is stable in a limited time,and the sliding variable converges to a predetermined zero neighborhood within a finite time,avoiding the overestimation of the gain and weakening the chattering phenomenon,and does not require any knowledge of uncertainties in the whole process.Then,choose the appropriate Lyapunov function to prove the stability of the closed-loop system.Finally,the effectiveness of the proposed scheme is proved by a active suspension systems model simulation.For the same second-order nonlinear system,the control strategy in practice should not only ensure that the system converge in a finite time,but also need to have better transient performance,including fast convergence characteristics and small tracking error.First,introducing the method of prescribed performance based on the above control strategy to ensure the transient performance of the system by using a transformed error,and the maximum overshoot and convergence rate of the system tracking error are confined to the predefined bound.Then,choose the appropriate Lyapunov function to prove the stability and transient performance of the closed-loop system.Finally,the effectiveness of the proposed scheme is proved by a active suspension systems model simulation.From the perspective of application,the control strategy proposed in this paper is applied to a quarter-car active suspension system experimental platform,and compared with the passive suspension system and the PD-controlled suspension system.The experimental results show that the proposed control strategy can make the suspension system have better ride comfort and anti-interference ability,and has obvious advantages in steady-state performance,transient performance and model-free control.Therefore,the control strategy proposed in this paper has the advantages of simple in form,robustness,high-accuracy and adaptation,and can be applied to practical applications simply and efficiently.