Compliant Control of Lower Limb Rehabilitation Exoskeleton Robot Based on Flexible Transmission

To ensure the safety, comfort, and effectiveness of lower limb rehabilitation exoskeleton robots in the rehabilitation training process, compliance is a prerequisite for human–machine interaction safety. First, under the premise of considering the mechanical structure of the lower limb rehabilitation exoskeleton robot (LLRER), when conducting the dynamic transmission of the exoskeleton knee joint, the soft axis is added to ensure that the rotation motion and torque are flexibly transmitted to any position to achieve flexible force transmission. Second, to realize the active compliance control of LLRER, the sliding mode impedance closed-loop controller is developed based on the kinematics and dynamics model of LLRER, and the stability of the designed control system is verified by Lyapunov method. Then the experiment is designed to track the collected bicycle rehabilitation motion data stably, and the algorithm and dynamic model are verified to satisfy the experimental requirements. Finally, aiming at the transmission efficiency and response performance of the soft shaft in the torque transmission process of the knee joint, the soft shaft transmission performance test is carried out to test the soft shaft transmission performance and realize the compliance of the LLRER, so as to ensure that the rehabilitation training can be carried out in a safe and comfortable interactive environment. Through the design of rehabilitation exercise training, it is verified that the LLRER of flexible transmission under sliding mode impedance control has good adaptability in the actual environment, and can achieve accurate and flexible control. During the experiment, the effectiveness of monitoring rehabilitation training is brought through the respiratory belt.

Cable-Driven Flexible Exoskeleton Robot for Abnormal Gait Rehabilitation

The number of people with abnormal gait in China has been increasing for years.Compared with traditional methods,lower limb rehabilitation robots which address problems such as longstanding human guidance may cause fatigue,and the training is lacking scientific and intuitive monitoring data.However,typical rigid rehabilitation robots are always meeting drawbacks like the enormous weight,the limitation of joint movement,and low comfort.The purpose of this research is to design a cable-driven flexible exoskeleton robot to assist in rehabilitation training of patients who have abnormal gait due to low-level hemiplegia or senility.The system consists of a PC terminal,a Raspberry Pi,and the actuator structure.Monitoring and training are realized through remote operation and interactive interface simultaneously.We designed an integrated and miniaturized driving control box.Inside the box,two driving cables on customized pulley-blocks with different radii can retract/release by one motor after transmitting the target position to the Raspberry Pi from the PC.The force could be transferred to the flexible suit to aid hip flexion and ankle plantar flexion.Furthermore,the passive elastic structure was intended to assist ankle dorsiflexion.We also adopted the predictable admittance controller,which uses the Prophet algorithm to predict the changes in the next five gait cycles from the current ankle angular velocity and obtain the ideal force curve through a functional relationship.The admittance controller can realize the desired force following.Finally,we finished the performance test and the human-subject experiment.Experimental data indicate that the exoskeleton can meet the basic demand of multi-joint assistance and improve abnormal postures.Meanwhile,it can increase the range of joint rotation and eliminate asymmetrical during walking.