柔性双手康复外骨骼抛接任务的过程协同控制

Cooperative Control of the Two-handed Flexible Exoskeleton for Rehabilitation Based on the Process of Juggling Task

针对柔性双手外骨骼在抛接任务中响应速度慢等问题,提出了一种双手抛接物体过程的能量传递模型以及具有位置前馈的力/位协同混合控制系统.首先基于双手接抛物体过程的运动特征,建立抛接物―人手碰撞能量传递模型;利用能量守恒定律与虚功原理建立柔性外骨骼手―人手耦合数学模型,推导出抛接碰撞模型中的绳索伸长量,以绳索伸长量作为前馈信息进行位置补偿;抛接过程初段对驱动绳索采用位置控制,当绳索伸长量保持不变且绳索拉力值持续增大时系统转换为力交互控制;最后通过柔性双手外骨骼抛接抓握实物的位置控制实验和力交互实验验证了基于绳索伸长量的位置前馈控制的动态响应性和有效性以及后段力交互控制下指尖接触力的稳定性.实验结果表明,柔性双手康复外骨骼可以辅助用户实现对抛接物的快速抓握,满足抛接任务对外骨骼手的协同控制要求.

To solve the problems of two-handed flexible exoskeleton in juggling task,such as slow response,an energy transfer model of two-handed juggling process and a hybrid force/position cooperative control system with position feedforward are proposed.Firstly,an energy transfer model of object-hand collision is established based on the movement characteristics of two-handed juggling process.Then,a mathematical model of coupling between the flexible exoskeleton hand and the human hand is established based on the law of energy conservation and the principle of virtual work.Meanwhile,the rope elongation in the juggling-collision model is deduced,which is considered as the feedforward value in position compensation.For the driving rope,the control system adopts position control at the beginning of juggling process,and switches to force control when the rope elongation remains unchanged and the tension value of the rope continues to increase.Finally,position control and force interaction experiments in juggling an actual object with the two-handed flexible exoskeleton are carried out to prove the dynamic responsiveness and effectiveness of the proposed position feedforward control strategy based on the rope elongation and the stability of fingertip contact force under the force interaction control in the posterior period.The experimental results show that the two-handed flexible exoskeleton for rehabilitation can assist the user to realize the rapid grasp of the objects,and meet the cooperative control requirements for the exoskeleton hand in the juggling task.