Gait Planning And Motion Control Of Hexapod Robot In The Nuclear Power Plant Circumstances

Because the environment of the scene of the nuclear plant accident accident is very bad,with large amounts of radiation,as well as a lot of steam of high temperature and high pressure generated by the accident,humans can't access to the site for disaster relief task.Therefore,it is very necessary and urgent to develop nuclear power plant disaster relief robot.Due to the complicated disaster environment,realizing the robot's stable equilibrium,overloading and flexible operation,the reasonable allocation of power consumption and rescue time and the control tasks for the underactuated walking robot are very difficult,so it is significant take the research on the relief master-slave robot control and self-discipline collaborative as one of basic science problems of nuclear power plant emergency relief robot.In this paper,in order to solve the stable control problem of the robot walking in the complex unstructured environment,the modeling,gait planning and control problem for the robot are systemically studied in this dissertation.The main research contents are listed as follows.1.The kinematics model of the disaster relief robot is established,based on the analysis of the mechanical structure and topological structure of the hexapod robot.Then the inverse model of the robot is obtained by analyzing the kinematics model.A reasonable gait is chosen for the robot to meet the requirements of stability and rapidness in the rescue tasks.2.A MPC controller is proposed,which comprehensively considers the characteristics of robot institutions and environmental constraints.By analyzing the robot's nonlinear hybrid dynamical system model and the periodic motion analysis of the robot leg joints,we transform the complex nonlinear model to a new linear space using transverse linearization technology,at the same time,we ensure that the dynamic characteristics of the transformed system model is the same with the original model.Then we design the MPC controller in the new space,which considers the system constraints in the actual rescue tasks.3.A fault-tolerant MPC control strategy is proposed to guarantee the robot can still walk to carry on rescue tasks even if the actuators of the robot are damaged.By analyzing the possible faults,in order to track the ideal trajectory and minimize energy consumption,we establish the trajectory optimization model of underactuated robot,and then design a fault-tolerant MPC control strategy to realize fault-tolerant control for the robot,considering system constraints such as geometric structure,motion balance and boundary conditions.4.A multi-objective hierarchical optimal controller is designed by comprehensively considering the requirements of energy consumption and rescue time in the rescue tasks.As energy consumption and rescue time are two conflicting goals,in order to solve their balance assignment problem,the first step we build the model of the robot,through the analysis of the model,the optimal control problem of the energy consumption is defined.Then we can minimize the energy consumption of the robot by optimizing the gait parameters,including robot walking step length,step height and other two parameters.The second step is to use Pareto optimality to solve the balance assignment problem of energy consumption and rescue time.5.The software system of the hexapod robot is built,after debugging the system,we conduct a series of experimental studies,to test the effectiveness of the controller designed in this paper.The experimental results verify the adaptability of the robot to unstructured terrain and dynamic environment under the action of the MPC designed in this paper.Meanwhile,The experimental results also verify that,with the optimal controller designed in this paper,the rescue time and energy consumption of the robot are Pareto optimal.