Novel Cascade Sliding Mode Control of Loader Electro-Hydraulic Systems Based on Improved Extended State Observers

To address the challenges arising from external load uncertainties and the limitations of hydraulic system modeling accuracy, this article proposes a novel cascaded nonlinear integral sliding mode control (CNISMC) scheme, enhanced by an improved extended state observer (ESO). The proposed solution, in contrast to conventional sliding mode control (SMC) approaches that are susceptible to chattering, incorporates a novel convergence law and a modified sliding surface, thereby substantially mitigating chattering effects and enhancing transient performance. Furthermore, by implementing a cascaded control structure, the hydraulic system is segmented into two subsystems, each aligned with specific disturbance sources and integrated with an advanced ESO for accurate disturbance compensation. The proposed scheme is validated through a series of simulations and experimental studies, showing a significant improvement in control performance compared to conventional controllers.