Research On Wire-Driven Pelvis Motion Control Robot

In recent years, rehabilitation robots as an emerging special robot are developed quickly. They could help the function-barrier patient and the elderly to carry on the recovery training in order to make the joint and muscle recovery effectively, which their quality of life are improved. It is also a main development content of the national guideline on medium and long term program for science and technology development.In the paper, the pelvis motion control of the lower-limb rehabilitation robot was chosen, and the key technologies of wire-driven pelvis motion control robot were researched. Through the robot, the coordinated motion between the body trunk and the lower limbs was realized and simultaneously certain external force was got, which could make not only the trainer carry on the weight relief training but also exercise self-balance ability training, thus the better training effect could achieved. The research mainly included. the wire arrangement scheme of wire-driven pelvis motion control robot, the configuration analysis of 1R2T robot, the dynamics analysis of 1R2T robot, the motion planning and so on. An experimental prototype of the wire-driven 1R2T robot was developed. Based on the dSPACE system, the experimental study on robot's control characteristic and dynamics performance was carried.On the basis of the researches results of the lower-limb rehabilitation robot as well as the pelvis motion control machine at home and abroad, a kind of wire-driven pelvis motion control robot was proposed to meet the requirement of the lower limb gait recovery training. The characteristics of wire-driven robot were analyzed and the trend of development was discussed.According to the lower limb support condition of the normal human, the lower limbs were simplified as the equivalent structural style. Based on the equivalent model, the types of pelvis's degree of freedom were analyzed and the motion space of the pelvis was confirmed in the gait recovery process. Based on the requirement for the pelvis motion control and the controllability of wire-driven robots, the structural style of wire-driven robots which was able to satisfy this function was analyzed. A kind of incompletely restrained wire-driven robot was selected. In the horizontal plane, the size and quality of the working space on different arrangement form of the wire-driven robot was simulated. The wire arrangement scheme of the wire-driven pelvis motion control robot was determined finally.Aiming at the arrangement scheme of wires in the horizontal plane, using the degenerated three-pyramid method, the direct and inverse position and pose were analyzed. The kinematics equations were established by the influence coefficients, so that the mapping relationship between wire's motion and pelvis's motion was obtained. The static wrench balance equations were founded. Through the generalized inverse method, the solution space of wire tension was got, which included smallest norm solution and null space solution. The influence of incompletely restrained robots on the pelvis motion control was studied, and the error analysis was carried on.Using the Newton-Euler method, the dynamics equations were constituted. Based on the D'Alembert principle, the force equations between the pelvis movement and the wire tension were got. The influence of wire elasticity on the robot dynamics characteristics was analyzed. Because one of different properties between wire-driven system and rigid system was that the rigidity of wire-driven system was relatively small, the influence of wire rigidity and wire tension in null pace on the pelvis static rigidity was analyzed, and pelvis vibration situation was analyzed under the external force.On the basis of the desired motion state of the pelvis in the course of gait training, the kinematics model was established using MATLAB, And is was confirmed by the machine model which was established using ADAMS. The inverse dynamics model was built, in which the wire rigidity was neglected. The motion planning was conducted, in which the influence of the wire smallest tension value on wire tension change was analyzed. The mathematical model of the wire-driven robot was founded in view of wire rigidity. The effects of wire rigidity and wire tension on dynamics motion planning were analyzed.According to the requirement of the pelvis motion control in the horizontal plane, the experimental prototype of the wire-driven robot was developed. The components and function of the experimental system were described. Based on the dSPACE system, the experimental study was conducted, which mainly included. the actuation control characteristic experiment, the trajectory planning experiment and so on. Through the experimental analysis, the results showed that the control performance and precision of the wire-driven robot could meet the requirement of pelvis motion control in the process of the lower limb gait recovery training.