The effect of joint assistance on human-machine interactive forces for weight-bearing exoskeleton robots

The weight-bearing exoskeleton robot helps wearer reduce the burden of carrying load, and the interactive pressure of lower limbs can be alleviated with joint assistance in the mid support phase. In order to analyze the influence of assistance at different joints on the forces between wearer and exoskeleton and propose a rational driving control mode, this paper established the mechanical model of exoskeleton according to the equivalent links and explored the interactive forces under different assistance of hip, knee and ankle joint. We found that supplying hip assistance could inconspicuously reduce the contact pressure. The mean interactive force was little at thigh but increased to 25N at shank when knee extension assistant torque with a peak value of 7Nm was provided. The human-machine force at shank was slight if a large ankle driving torque with a peak value of 18Nm was exported, without changing the interactive force at thigh. The results illustrated that the assistance of knee and ankle joint could significantly reduce lower limb contact forces compared with that of hip. Providing assistant torque at ankle joint could play a better effect if a high-power device could be applied.