High-precision electro-hydraulic position servo system for machine tools utilizing mathematical model identification and control techniques

Abstract

The electro-hydraulic servo control system often suffers from low accuracy and poor stability due to its nonlinear and time-varying parameters. To tackle this, an experimental model was created using a third-order nonlinear open-loop system with a unit step input. Through xPC semi-physical simulation, stability and identification analyses led to the development of a mathematical identification model. A composite control switching method was proposed, highlighting the relationship between control methods and self-adjusting factors. An online self-adjusting fuzzy PID control approach allows real-time adjustments of control rules, aiming to enhance performance. The proposed algorithm's stability is set for theoretical and quantitative analysis, with feasibility validated through simulation. Additionally, challenges arise from severe nonlinearity, time-varying internal parameters, and external load interference, impacting both static and dynamic control performance. To mitigate these issues, a switching control method combining fuzzy PID schemes was suggested. This approach effectively reduces response times and errors while improving stability and control accuracy near operating points. Simulations using xPC semi-physical setups and MATLAB demonstrated that the online self-adjusting fuzzy PID method significantly enhanced control accuracy in high-precision electro-hydraulic servo systems, boosting speed and dynamic performance while eliminating stability errors.