In order to make full use of the remaining motor ability of hemiplegic patients and improve their degree of participation during training

an assist-as-needed control strategy based on error-bands is proposed.Firstly

based on the human-machine coupling model

the relationship between the variables of robot joint and the human angles of lower limb joint motion is determined

and a gait information acquisition system is built.Secondly

based on the characteristics of ankle joint position in the sagittal and horizontal planes

the error-bands are established and divided

and the starting moments of the error-bands at different stages are determined.A control method is proposed to set a sliding point on the desired trajectory and use the sliding point as the motion reference of the ankle joint position on the affected side.Finally

a gait rehabilitation robot experimental system is built to complete the active movement experiment of the healthy limb and the experiment of the affected limb following the trajectory of the healthy limb.The experimental results show that the robot can follow the movement of the affected limb when the error of motion trajectory of the affected limb side is within the error-bands.When the motion trajectory of the affected limb side is outside the error-bands

the robot can assist the movement of the affected limb to make the trajectory error within the error-bands

so that assist-as-needed gait rehabilitation training is realized.