| When walking fast or crossing obstacle, modular biped robot has several unparalleled advantages. It can adjust itself to different conditions. It is simply maintained, friendly to environment, cost-effective and easy to be assembled. According to kinematic and dynamic requirements, robot can be assembled by standard link and joint modules. Modular biped robot in this paper is assembled by PowerCube modules which are produced by Schunk company. It has twelve degrees of freedom for the legs and the upper body is simplified with no degree of freedom.Firstly, we introduce the profile of modular biped robot. The forward kinematics of robot using D-H parameters and tansformation matrix are obtained. The dynamic equation of the robot is also attained based on Lagrange method which provides theoretical basis for further simulation.For the F/T sensor simulation, mathematical modeling analysis is done by simplifying force module for spring-damper-mass system and moment module for countertorque detecting device. Then we establish Linear Quadratic optimal controller and simulate it in simulink module of matlab. The response of control system is corrected by PID. The simulation of sensor control system with second order inverted pendulum and cart as input is implemented and the simulation results show that the control method is correct.When studying dynamic balance of the robot, a ZMP formula using Lie Group is given for detecting ZMP of robot in real time. This formula uses information from F/T sensor both in single support phase and in double support phase. ZMP point detecting experiment is carried out and detecting method is verified.At last, convex optimization for balance control is studied. The ZMP and COM constraints are established. The trajectories of hip, knee and ankle joints are obtained using Mosek toolbox in Matlab. The simulation results show that Second Order Cone Convex Optimization is effective and stable walking of robot can be realized. |
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