Abstract
Each joint of hydraulic drive legged robot adopts highly integrated electro-hydraulic servo system, and the system has two common forms, namely, valve-controlled cylinder system and pump-controlled cylinder system. The former has a large energy loss, which restricts the endurance of the legged robot in the field. Although the latter has the advantages of energy saving and high efficiency, the overall response ability of control system is unsatisfied. In this paper, a novel pump-valve compound drive system (PCDS) is designed. It combines the advantages of pump-controlled cylinder system and valve-controlled cylinder system, which can not only effectively reduce the energy loss of the system, but also ensure the electro-hydraulic servo system of the robot joint has the ideal response ability. This paper consists of three parts. In the first part, the mathematical model of nonlinear force control of PCDS is established, which takes into account the pressure-flow nonlinearity of servo valve, the asymmetry of servo cylinder and the complexity and variability of load. So this model has a high accuracy. In the second part, On the basis of the above model, a force control method combining tracking error compensation and load compensation control is designed. And this control method can improve the control precision of the robot. In the third part, the performance of the designed control method is verified by experiments. The experiments show that the designed force control method can effectively reduce the influence of external position disturbance on the tracking accuracy of the force control system and improve the control accuracy of the robot joint movement.
Highlights
In recent years, researchers in various countries have made in-depth studies on the field of mobile robots
This paper mainly focuses on the force control of pump-valve compound drive system (PCDS), and takes into account the response of the system, so the servo motor in the system adopts torque control mode
Aimed at the demand of energy saving, high precision and high response speed for legged robot joint driver, PCDS is designed in this paper to improve the cruising ability in field work, and the mathematical model of nonlinear force control of the system is established
Summary
Researchers in various countries have made in-depth studies on the field of mobile robots. In recent years the legged robot has been combined. The associate editor coordinating the review of this manuscript and approving it for publication was Yingxiang Liu. with hydraulic system, which makes the legged robot drive by hydraulic system more suitable for the missions such as detection, transportation, rescue and military assistance in complex environments or the wild. Most of the drive units of hydraulic drive legged robot use valve-controlled throttling system, but its energy utilization rate is still very low. The pump-control system with volumetric control can effectively improve the endurance of the robot, but its response speed is low and the control accuracy is unsatisfied [6], [7]. It is urgent to study a pump-valve compound control system and its control methods
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