Precision Motion Control of Hydraulic Actuators with Performance Guaranteed Online Parameter Estimation

With the development of industrialization, valve-controlled hydraulic actuators are gradually attracting attention for their impressive power-to-weight ratio, high torque/force output, and significant load capacity, and their future application in heavy engineering has great potential. However, due to the complex higher-order nonlinear dynamics as well as the parameter uncertainties and uncertain nonlinearities of hydraulic actuators, the design of their controllers is full of challenges. Moreover, when facing practical work requirements such as load estimation, achieving an ideal position-tracking effect alone may not be sufficient. Accurate parameter estimation becomes equally important in such cases. For this purpose, a direct/indirect adaptive robust controller (DIARC) is proposed in this paper. By incorporating nonlinearities and uncertainties into the dynamic modeling and compensating for them with adaptive robust controllers, the effectiveness of the control can be improved. Furthermore, we have enhanced the traditional adaptive law by integrating not only the tracking error but also the parameter estimation error information. This improvement allows for a more accurate and reliable estimation of the parameter. The control performance is simulated and verified. The simulated results indicate that the implemented controller not only enhances tracking accuracy but also accurately estimates the unknown parameter.