# A Construction Method of Lower Limb Rehabilitation Robot with Remote Control System
## 2 Materials and Methods
### Design of Rehabilitation Robot System
#### 2.1.3 Design of Robot Mechanical and Electrical Structure  
The rehabilitation robot should have the characteristics of simple structure, high equipment stability, good robustness of the control system, and compliant human-computer interaction. The robot needs to realize the integration of medicine and engineering in the design process. The rehabilitation robot platform system is shown in Figure 1a,b. The size of the robot is 120 \(\times\) 98 \(\times\) 180 cm\({}^{3}\), forming an independent training space. The robot adopts a gantry scheme to facilitate the use of wheelchairs by patients. Second, the beam and column of the gantry structure are made of aluminum profiles, and the base is made of steel materials. This material choice can reduce the structure of the robot and improve the stability of the equipment. Two driving wheels are installed in the middle of the base to provide the driving force for the robot. At the same time, four non-central universal wheels are installed at the front and rear to carry the robot's own weight and load. The robot driving wheel is installed in the middle of the base so that the robot can realize a small radius or in situ steering, and improve the mobility of the robot. The robot drive system adopts a spring lever suspension design. The compression spring provides pressure to the drive wheel through the lever, so that the drive wheel can maintain contact with the ground and ensure the continuity of power output. The driving wheel adopts a 24 V dual-shaft hub servo motor with a maximum power of 200 W and a rated output torque of 2.4 N.m. The built-in 1024-line photoelectric encoder can accurately feedback the motion data of the driving wheel and achieve closed-loop robust control. The lower limbs of stroke patients cannot provide enough strength to maintain body balance. Patients need to use the upper limbs of the healthy side to assist the body balance during exercise. Patients need to rely on external forces to maintain body balance during rehabilitation training. The robot BWS system is shown in Figure 2. The patient has unilateral rehabilitation needs on the left or right side of the body, so the BWS system adopts a left-right symmetrical structure design. The system consists of steel cable, servo motor, worm gear reducer, force sensor, fixed shaft pulley, pulley moving pair, tension spring, linear guide, and traction arm. To make the system compact and to ensure sufficient output, the robot is equipped with a 1:40 worm gear reducer, which can provide a support force of 2500 N for the patient. The steel cable is combined with the worm gear reducer, and the other components are connected to realize the mechanical transmission. The cable transmission not only has a good consistency but also has the characteristics of low friction. Figure 1: (**a**) Design of rehabilitation robot structure; (**b**) system module of rehabilitation robot. The system servo motor adjustment supports the system value and adapts to the patient's training status. The force sensor can feedback the patient's lower limb strength data during the training, and objectively evaluate the patient's lower limb rehabilitation effect. The lower limbs of stroke patients cannot provide sufficient strength support for the body, and the upper limbs also have dysfunction, and the affected side of the body is in an uncontrolled state, and cannot provide effective assistance for the patient's recovery. During the rehabilitation, the patient's healthy upper limb often grips objects to maintain body balance. Although the robot BWS system helps the patient achieve physical balance, the patient still obtains a sense of psychological security by gripping the object, and cannot independently complete the human-machine collaborative rehabilitation. Doctors or family members are required to operate the robot to help patients achieve the goal of lower limb rehabilitation training. A human-computer interaction system was developed for this problem.