ESO-based adaptive sliding mode control of servo system

In addressing the control challenges posed by backlash nonlinearity in servo systems, which can significantly degrade performance, a novel control strategy has been developed. This strategy integrates adaptive sliding mode control (ASMC) with an extended state observer (ESO). The ASMC component is adept at handling uncertainties and disturbances by dynamically adjusting control parameters, making it particularly suitable for systems with varying operating conditions. Meanwhile, the ESO serves to accurately estimate and compensate for unmodeled dynamics and external disturbances, including the backlash effect, thus enhancing the system's robustness. The backlash and frictional nonlinearities were modelled and converted into system disturbances, leading to the establishment of a series-integral type system structure. An improved sliding surface scheme was constructed that incorporates nonlinear functions, which effectively accelerates system state convergence to stability while mitigating chattering effects. For feedforward control implementation, an adaptive weighting tuning law was designed for online estimation of unknown nonlinearities, eliminating the need for prior system information and instead relying on adaptive laws for estimation. Simulation experiments have demonstrated that the control scheme exhibits superior control performance in suppressing the backlash nonlinearities in servo systems.