Simplified STR Applied to Level Control of Electrohydraulic Bending Machine

Abstract

A two-actuator electrohydraulic bending machine is a typical MIMO system, where the level control function is degraded by the interior structural difference between the two actuators and also by the hydraulic drive interaction. The conventional self-tuning control and decoupling method are too complicated and time-consuming, and are not suitable for this system. Based upon our previous studies, this system can be simplified as two individual sets of servo-control actuating system, which is simulated as a 1st-order ARMAX model and its coupling interactions between actuators are treated as a disturbance term of the ARMAX model. Then, two sets of implicit self-tuning controller and a level control regulator are designed for servo-tracking and level control. This proposed control scheme not only reduces the number of parameter estimations significantly, but also yields the effect of dither in order to overcome the drawbacks of servovalve stickiness and mechanical frictions. Finally, the experimental results indicate its satisfactory performance and prove its superior decoupling ability and disturbance rejection.