康复外骨骼的人-机重力平衡策略

Human-Machine Gravity Balance Strategy of Rehabilitation Exoskeleton

针对一种上肢康复外骨骼,提出了2种被动人-机重力平衡策略,以减小关节负载力矩、降低驱动电机功率.采用2套零初长弹簧单元作为重力平衡装置,以人-机系统在任意位姿下的势能总和保持恒定为理论依据,推导出人-机系统的完全重力平衡模型.为简化平衡系统及避免发生干涉,仅引入单套零初长弹簧单元,以人-机系统在给定运动范围内势能变化最小为优化目标,施以约束条件,对弹簧安装位置及劲度系数进行优化设计,实现人-机系统的部分重力平衡.通过计算人-机系统各位姿下的关节力矩,对2种平衡方式下的算例进行了对比分析.结果表明:完全平衡后各关节重力矩被完全消除,部分平衡后各关节重力矩被大部分消除,验证了2种平衡策略的合理性.

For an upper limb rehabilitation exoskeleton,two passive human-machine gravity balance strategies were proposed to decrease the joint torque and the power of the driving motor. Two units of zero-free-length springs were added in the exact gravity balance system of the exoskeleton. According to the constant potential energy of the human-machine system,a balance model of the exact gravity balance system was established. To simplify the balancing system and avoid colliding with human body,an approximate gravity balance system was presented and only one unit of zero-free-length springs was introduced in the exoskeleton. The locations and main parameters of the installed springs were optimized and obtained based on the minimum change of the total potential energy in the given workspace. To verify the balance system mentioned above,two examples were compared and analyzed by calculating the joint torques at different poses of the exoskeleton. Results show that the torque of each joint can be eliminated completely by the exact gravity balance system and reduced mostly by the approximate one.