基于稳定阈度分析的外骨骼动态步长规划方法

Dynamic step length planning method based on stable threshold analysis for exoskeleton

在医疗领域,康复外骨骼机器人能够帮助下肢瘫痪的患者重新行走,因此得到广泛的关注。由于下肢截瘫患者身体的特殊性,针对该类患者使用的外骨骼机器人大多使用拐杖作为平衡辅助工具。在固定步长的情况下,不同的拐杖支撑点位置,会很大程度影响步行稳定阈度。通过分析穿戴者拄拐步态所形成的多边形支撑面,利用零力矩点(ZMP)理论计算相应的压力中心位置,从而得到四足步态的稳定阈度表达式;并在此基础上提出动态调整步长的方法,得到拐杖支撑点与步长的拟合曲面,对步长进行实时、适当调整;最后通过外骨骼机器人的运动学模型,规划相应的步态轨迹。通过在课题组自主研发的外骨骼机器人样机上进行大量对比实验,证明了在每个步态周期中,针对不同的拐杖支撑位置,提出的方法可以有效增加系统步态的稳定阈度,降低拐杖支撑点的随机性对系统稳定性的影响。

In medical field,the mobile rehabilitation exoskeleton robots arouse wide concern as they can help the paraplegic to regain the ability to walk again. Due to the body specificity of paraplegic patients,as the balance axillary means,crutches are necessary for the paraplegic patients who wear the exoskeleton robot to keep balance. We found that in the case of fixed step length,different support point positions of the crutches have great impact on the gait stable threshold. In the paper,through analyzing the polygon support plane formed when the users wear the exoskeleton robot to walk with crutches,ZMP theory is used to calculate corresponding position of the center of pressure. Thus,the stable threshold expression of quadruped gait is obtained. Based on these,the method of dynamically adjusting step length is proposed,and the fitting surfaces of the crutch support point and step length is obtained,thus the step length can be adjusted properly and in real time. Finally,the gait trajectory is planned using the kinematic model of the exoskeleton robot. A large number of comparison experiments were carried out on the exoskeleton robot developed independently by our team,the results prove that aiming at different crutch support positions,the proposed method can significantly increase the system gait stable threshold and reduce the influence of the crutch position randomness on system stability in each gait cycle.