Research And Implementation On Compliance And Force Control Of Hydraulically Actuated Quadruped Robot

Since ancient times, man has always dreamed to create the artificial legged, similar to the wisdom of animal, walking mechanical means of transport, alongside the Creator. This dream duration may be longer than the human dream of flying in the sky. BigDog appears like a gust of stimulants, a worldwide boom sets off a wave of quadruped robot research. However, in today's technological level, what legged mobile machinery can be produced by humans? And what can be found out or which work can be performed by legged robots to help humanity? Compared to our existing vehicles and other means of transport, what are the advantages of these legged mobile robots?Faced with the challenges of this issue, we have successfully designed and developed hydraulic driving quadruped robot-SCalf. This paper concentrates on the system architecture design, design and implementation of compliance control method and hopping control based on the planar model during the process of SCalf development. The content mainly includes the following aspects:1. According to the distributed characteristics of each subsystem of SCalf robot, a centralized control system with dual CAN bus is designed and implemented; subsequently, aiming to improve the servo bandwidth and achieve the goal of joint torque control, the distributed digital reconstruction of the servo system is carried out on the basis of the original centralized control. The distributed control method based on the system is designed simutaneously; Based on a single leg servo controller in the above distributed system, a single leg testing platform for force control is designed and implemented.2. The floating base dynamic model of single leg system is constructed based on Newton Euler method; In view of the actual platform, we design and develope the foot impedance compliant control method based on the plantar force sensing and joint position control, foot impedance compliant control method based on the plantar contact force calculation and joint positon control and compliant control method based on virtual model and joint force control. Analysing the characteristics of the above three methods and experimental results, the second method is implemented on the SCalf-II robot and carried out on the rough terrain.3. On the basis of virtual model control and energy planning method, we studied on the running and hopping control of the robot with trot gait. The simulation experiment is carried out in the virtual physical environment, and the validity of the method is verified; through the detection of the robot trunk posture, it enhances the adaptability of the method in rough terrain; the robustness of the method is tested and discussed in the case of the assumption of the proposed method is not satisfied.Through the above research, the achievements of this paper are as follows:1. The centralized control system of hydraulic quadruped robot based on double CAN bus is designed and realized. On the basis of it, a distributed control system based on fieldbus and single leg servo controller is realized on the hydraulic driving quadruped robot for the first time. And we propose a distributed control architecture of quadruped robot.2. We construct a planar single leg testing platform with indoor hydraulic drive, which can carry out the single leg motion test and foot-ground interaction experiment oriented to whole torque control.3. The floating base dynamic model of single leg system is constructed based on Newton Euler method. On the basis of the model, we implement the legged compliance control experiments based on the plantar force sensing, plantar force calculation and virtual model. Finally we find the most suitable compliance control method for SCalf-II robot.4. We propose the planar hopping control method for quadruped robot based on the virtual model and energy planning, and improve the adaptability of the method on rugged terrain.In this paper, not only the academic issues are studied, but also the development cost, manufacturing/maintenance difficulty and other factors are all considered. Through the virtual physical simulations and physical prototype experiments, it is proved that the conclusions have the advantage of strong realizability.