具有自适应增益的电液位置伺服系统超螺旋滑模控制

Super-twisting Sliding Mode Control of Electro-hydraulic Positioning Servo Systems with Adaptive Gains

电液位置伺服系统是复杂的非线性控制对象,存在各种建模不确定性,使得设计高性能的控制器以满足系统伺服精度要求更加困难。针对考虑各种建模不确定性的电液位置伺服系统,设计了一种具有自适应增益的超螺旋滑模控制方法。利用已知的系统模型信息,在传统超螺旋滑模控制算法中引入基于模型的前馈控制律,提升系统伺服精度。采用自适应律实时更新控制器增益,无需先获知系统建模不确定性的确切界,避免了传统算法中由人为设定与该界相关的控制增益造成的保守性。基于Lyapunov稳定性理论证明了闭环系统全局稳定,系统跟踪误差可在有限时间内渐近收敛到零附近任意小的范围内,且收敛的速度和稳态误差的界可通过参数进行调节。仿真结果表明,所提出的控制方法可有效地抑制建模不确定性对系统的不利影响,显著提高其跟踪精度,且所得到的控制输入是连续的,更利于实际应用。

Electro-hydraulic positioning servo system is a complicated nonlinear control object,and usually suffers various modeling uncertainties,which make it more difficult of the high performance controllers design to meet the servo accuracy requirements. A super-twisting sliding mode control strategy with adaptive gains was designed for the electro-hydraulic system with consideration of various modeling uncertainties. With using known information of the model,the feedforward control law based on the model was imported into the traditional super-twisting sliding mode control algorithm,so as to improve the accuracy of servo system. By utilizing the adaptive laws to update the control gains in real-time and without knowing the prior knowledge of the exact bounds of modeling uncertainties,the conservatism caused by the artificially selected control gains which are related to those bounds in traditional control algorithm was avoided. The global stability of the closed-loop system was proved based on the Lyapunov stability theory. The system tracking error was guaranteed to converge to an arbitrary small neighborhood around zero in finite time,and the converging rate and the bound of the steady state tracking error could be adjusted by control parameters. Simulation results show that the proposed control strategy can effectively attenuate the adverse effect brought by the modeling uncertainties and apparently improve the tracking accuracy. In addition,the achieved control input is continuous,which is more suitable for application in practice.