Research And Implementation On Complicance Control Of Hydraulicrobot Joints

Legged robot is a popular research area in recent years of the world, with complex terrain and environment adaptability, it can maximum to assist people to accomplish lots of complex tasks, so it has broad application prospects. Hydraulic servo dues to its large power density, fast dynamic response and strong resistance to electromagnetic makes the robot has the characteristics of higher load and dynamic performance. Robot trajectory control in natural space has been relatively mature, but it can’t be avoided contact with the external environment during the relevant job or walking. Due to the large hydraulic stiffness, it will seriously affects the robot stability with a bigger impact when contact with the outside world, Therefore, This article is based on engineering problems of hydraulic drive of legged robot, which allows the robot to exhibit compliant features by increasing the elastic element and smooth control algorithm, and has certain ability to cushion the impact. The main content is as follows:Firstly, by asymmetric hydraulic cylinder model is analyzed, the introduction of elastic element convert the force into position measurement, enhanced environmental adaptability. And analyzes the mathematical model of the hydraulic SEA and join the damper behind, after the establishment of a relationship of force control parameters, so that the hydraulic force drive can be accurately controlled. By analyze its stability verified it can satisfy the actual robot basic needs of smooth control.Then the article analyzes the model of location-based impedance control, also established a relationship between environmental forces and hydraulic cylinder position. Through the control method of inner and outer ring combined, and real-time stress state compensation. It simulates impedance characteristics at the robot end. So it has better unknown environmental adaptability. At the same time analyzes the model of virtual leg from the perspective of the whole robot legs, then established the relationship between virtual leg stiffness, elastic deformation and the displacement of hydraulic cylinder. It makes the robot can exhibit varying stiffness characteristics under stress.Finally, the article designed the hydraulic SEA, and built a robot experiment platform combining with control method. With embedded QNX system, completed the task of creating multi-threaded program and control algorithms. Through the simulation and experiments of single hydraulic cylinder proved its stability of force control and dynamic response, with the impedance control simulation and experiments analyzed the influence of stiffness on the robot flexibility and damping on the adjustment process, while the virtual leg stiffness control experiments verified its ability to provide variable stiffness. Eventually from the walking experiment result proved the two methods can achieve a certain effect compliance control. Provide the support for the robot stability.