ABSTRACT
Objective:To solve the problem of leg shaking caused by the sudden change of angular acceleration at the joint of periodic motion during circular gait training of lower limb rehabilitation robot. Methods:A kind of quasi-circular gait was proposed, which divided the periodic motion into three phases: start phase, middle phase and end phase. The time was equal in the start phase and the end phase, and could be adjusted with the parameter ratio. The joint trajectories of the two phases were planned by quintic polynomial, and the middle phase was still the circular gait joint trajectory. The trajectory of the proposed quasi-circular gait was simulated. Results:The angular velocity was continuously differentiable and 0, the angular acceleration was continuous and 0, and the end-effector trajectory became flat with the increase of ratio. The results on the physical prototype of the lower limb rehabilitation robot were principally consistent with the simulation, and the machine worked smoothly. Conclusion:The proposed variable quasi-circular gait had smooth angular acceleration at the junction of periodic motions, which effectively solved the jitter problem when using circular gait for lower limb rehabilitation training and avoided secondary injury to the patients.
ABSTRACT
Objective:To develop an automatic adjustment algorithm of bed height of multi-position lower limb rehabilitation robot, to meet the variety of leg lengths and training modes to avoid the collision between robot and ground. Methods:Six mathematical models of robot bed body height were established for six training modes of multi-position lower limb rehabilitation robot, which were described with leg length and bed tilt angle. The influence was analyzed that mechanical clearance and deflection as well as the jitter error of leg bracket during movement. Furthermore, a software related to these models was developed to automatically adjust the bed height for training. Volunteers were recruited to test actually. Results:The test data of bed height are consistent with the theoretical calculation of six mathematical models. Clearance and deflection did not affect the theoretical results of bed height. The end of robot's lower limb was always above the safe height during rehabilitation training. Conclusion:The automatic adjustment algorithm of bed height has been established, which can ensure that the rehabilitation robot runs at a safe height.
ABSTRACT
Objective:To solve the movement mode adapting to individual differences for the trajectory planning of lower limb rehabilitation robots. Methods:After summarizing the six movement modes of the lower limb rehabilitation robot, according to the multi-rigid body theory of the human body, the exoskeleton of the lower limb rehabilitation robot was simplified into a two-bar linkage mechanism, the inverse kinematics analysis of the motion mode was performed, and the motion pattern solving system was designed based on C#. Results:The motion mode joint angle value calculated based on the C# motion mode solving system was transmitted to the upper computer, and the six motion modes were successfully applied to the lower limb rehabilitation robot. Through the inversion kinematics analysis of the motor model, the C#-designed motion mode solving system could solve the motorized joint angle values that adapted to individual of different leg lengths with lower extremity motor dysfunction. Through physical prototype experiments, the lower limb rehabilitation robot could drive the human body model for rehabilitation training according to the planned exercise mode. The actual joint angle curve and the theoretical joint angle curve were basically coincident, the joint angle error was small. Conclusion:The individual difference motion pattern solution is valid and feasible.