Research On Motion Control Of Wheeleg Robot Driven By Hydraulic Actuators

At present, the research on legged robot is active, but the legged robot is difficult to control. By contrast, wheel robot is easy to control and has the advantage of good stability. Integrating the advantages of legged robot and wheel robot, many research institutions develop the research of wheeleg robot, which has strong ability to adapt to unstructured terrain, while avoiding the shortcoming that legged robot is difficult to control, therefore the research of wheeleg robot has great theoretical value and engineering significance.Aiming at a kind of special structure of wheeleg, it’s motion control was studied. The robot is composed of two front legs and two rear wheels. Each front leg joint is driven by hydraulic actuators, and rear wheel is unpowered. The main achievements are in the following respects:1. Based on wheeleg robot motion characteristics, its movement is decomposed into two parts: stance phase and swing phase. The robot is simplified and its’ geometric constraints are introduced, the wheeleg robot’s kinematics models,in stance phase and swing phase, are established, at the same time, based on the Lagrange equation, dynamic model of legs, in stance phase and swing phase, were deduced.2. Propose a coordinated control strategy that based on supporting leg and swinging leg model. In stance phase, wheeleg robot’s body posture is controlled. The trajectory control of swinging leg’s foot endpoints and its soft control when contacting with the ground are researched. To solve the problem of conversing the swing phase and stance phase, the contact force is introduced. The effectiveness of the control strategy is verified by simulation.3. The joint torque control is the basis for the operational space control of robot. The research is mainly focused on the identification of joint model and force control of the hydraulic actuator. Based on the identification model, double PI force control algorithm was designed and force servo control experiment is developed, the experimental results verify the validity of the model identification and control algorithm.4. Build the wheeleg robot experiment platform, and carry out the pitching angle control experiment and the contact force control experiment. The experiment results verify the feasibility of the algorithm.