Variable Structure Compensation PID Control of Asymmetrical Hydraulic Cylinder Trajectory Tracking

A novel variable structure compensation PID control, VSCPID in short, is proposed for trajectory tracking of asymmetrical hydraulic cylinder systems. This new control method improves the system robustness by adding a variable structure compensation term to the conventional PID control. The variable structure term is designed according to sliding mode control method and therefore could compensate the disturbance and uncertainty. Meanwhile, the proposed control method avoids the requirements for exact knowledge of the systems associated with equivalent control value in SMC that means the controller is simple and easy to design. The stability analysis of this approach is conducted with Lyapunov function, and the global stability condition applied to choose control parameters is provided. Simulation results show the VSCPID control can achieve good tracking performances and high robustness compared with the other control methods under the uncertainties and varying load conditions.

A Novel Compound Control Method for Hydraulically Driven Shearer Drum Lifting

In order to adjust shearer drum swiftly and precisely to adapt to the changes of coal seam, a compound control approach based on cerebellar model articulation control and fractional order PID controller was proposed. As the movement precision and response speed of hydraulic system were determined mainly by the control precision of valve-controlled asymmetrical hydraulic cylinder, its working principle and characteristics were analyzed in this paper, with particular focusing on the asymmetry problem. Furthermore, RBF neural network was applied to obtaining reasonable tuning parameters and a control algorithm of proposed controller was designed. Finally, laboratory experiments were developed to verify the validity and effectiveness of proposed compound control method. The testing results, compared with those for other controllers, proved that the proposed compound control method can acquire high movement precision and respond speed in the system of hydraulically driven shearer drum lifting with different control conditions.

Analysis and Design of Hydraulic System of a Hydraulically Actuated Quadruped Robot

Quadruped not only possess excellent kinetic speed and stability but also can adapt to various complex terrains, with the result that hydraulically actuated quadruped bionic robots with high load and outstanding adaptability have become the research hotspot. Hydraulic system, which is regarded as the dynamic part of a hydraulic quadruped robot, has a direct effect on the kinetic capability of robots. Based on dog’s structure bionics, hydraulically actuated quadruped robot was designed. In accordance with distribution modes of hydraulic cylinders which drive robot’s kinetic joints, a hydraulic oil-line system of the robot was designed in this paper. Combining the maximum design kinetic velocity, trotting movement pattern within foot’s work space was planned. Velocity curve of each joint’s hydraulic cylinder was obtained through simulation analysis of dynamic analysis software. According to the structure of asymmetrical hydraulic cylinder, minimum flux which the oil hydraulic pump theoretically requires at the robot’s maximum kinetic speed was calculated. With practical experience, the oilsource parameter which could meet the demands of hydraulic quadruped robot were determined.