Extended State Observer-Based Predefined Time Composite Anti-Disturbance Control for Hydraulic Cutting Arm

During tunnel excavation, designing a trajectory tracking controller based solely on a pure rigid body model is insufficient to achieve optimal section forming quality. Because when the cutting head is subjected to complex coal-rock loads, the presence of hydraulic oil elasticity will inevitably arise system vibration, further causing roadway over-excavation, ultimately deteriorating section quality. Hence, a rigid-flexible coupling model of the cutting mechanism, considering hydraulic system stiffness and damping, is first established in this article, and it is further decomposed into a slow-varying subsystem (SVS) and boundary layer subsystem (BLS) using singular perturbation theory for independent design of controllers. Secondly, a new time scale function is proposed for designing a predefined-time (PT) extended state observer, achieving estimation of the disturbance term suffered by the cutting system within a PT for the first time. Then, a PT dynamic surface controller with tunable convergence time is developed for SVS. A PT state constraint controller is designed for BLS to suppress vibration acceleration. Ultimately, through comparative experiments on a roadheader prototype, it is verified that the constructed composite controller can effectively attenuate system vibration while tracking cutting trajectory within a PT, thereby significantly improving section quality and beneficially extending key component lifespan.