Full-State Error Constraints Based Dynamic Surface Control of Electro-Hydraulic System

An electro-hydraulic system (EHS) has unknown lumped uncertainties caused by some uncertain hydraulic parameters and external loads, which will decline the output response performances and internal state stability. To handle these lumped uncertainties, a barrier Lyapunov function-based dynamic surface control method is adopted in EHS to constrain the full-state errors in the desirable boundaries. The full-state error constraints represent not only the tracking accuracy of the cylinder position but also the rate-limit of the cylinder response and the feasible load pressure boundary of the cylinder. The dynamic surface is used to avoid the explosion of complexity, since the virtual control variable has been repeatedly calculating its differentiation. All the states of EHS are ultimate boundary with satisfactory dynamic tracking performance and high stable accuracy by the proposed controller. Some comparison results with the PI controller have verified the effectiveness of the proposed controller in both nominal and lumped uncertainties conditions.