A Novel Force/Position Control for the Flexible Lower Limb Exoskeleton with Hybrid Actuators

Lower limb exoskeletons can assist or augment human performances for various applications. Flexible lower limb exoskeletons have gained attention due to their light weight, comfortable wearability and other advantages. This paper presents a hybrid active-passive drive flexible lower limb exoskeleton to minimize energy consumption for human walking with the same external energy input. A novel force/position control for hip assistance is proposed with the exoskeleton. The controller accurately tracks and adjusts the actuator profiles in real time to achieve precise assistance to the wearer. The exoskeleton integrates IMUs and load cells to detect the wearer’s states. This paper models the human and exoskeleton coupled to generate the actuator profiles corresponding to the hip assistance force required during walking. Three individuals walk on a treadmill at a speed of 1.25 m/s to evaluate the controller’s performance. The results show that the average transmission force starts simultaneously with the peak angle of hip flexion, and the peak force error is within 5.25% for the given actuator profiles, indicating that the controller can effectively assist the wearer with the exoskeleton.