# Development and Assist-As-Needed Control of an End-Effector Upper Limb Rehabilitation Robot
## 2 Development of the End-Effector Upper Limb Rehabilitation Robot (EULRR)  
### Mechanical Design of the EULRR  
EULRR is a new end-effector upper limb rehabilitation robot that could guide the patient's arm who have upper limb motor dysfunction to carry out spatial trajectory rehabilitation training. Compared with the unilateral rehabilitation robot, only the robot on the affected side of the patient needs to be used for the upper limb rehabilitation training, and the robot on the other side moves to the safe position designated by us. Conversely, when the other side manipulator is used for rehabilitation training, the manipulator at the opposite side also moves to a safe position. Unlike the unilateral rehabilitation robot, which either needs to adjust the patient's position or needs to design specific devices to move the base of the robot to adapt to the rehabilitation training for patients with different side motor dysfunction of the upper limb. To illustrate the structural design of EULRR clearly, a three-dimensional SolidWorks model design is given in Figure 1. EULRR mainly consists of the body structure module and the motion assistance module. The body structure module, which is equipped with six universal wheels, is mainly used to support the assistance motion module, as well as the robot control cabinet, the control computer, and the electrical structure. The motion assistance module that consists of two commercial manipulators is installed outside the body structure module and is used to support and assist the patient's arm to completing rehabilitation training. Each manipulator has 7 DOF (degree of freedom), and each joint is equipped with a torque sensor and a position encoder, which can be realized by the torque control. The load of the manipulator is 7 kg, and the working radius of the manipulator is 800 mm. Two handles are installed at the end of the manipulators, which are used to connect the manipulator with the patient's hand through the bandage, as shown in Figure 2. The handle in EULRR is mainly used for testing, and further design is needed for actual use in patients' rehabilitation training.  
According to the dual-arm workspace of human upper limbs [34], the motion assistance module of the EULRR designed in this paper is installed horizontally, and the two manipulators are installed at a mutual vertical angle. The base mounting distance between the two manipulators in EULRR is designed based on the anthropometric theory. [PERSON] et al. [35] suggested that the shoulder width had a  
Figure 1: Three-dimension model of the end-effector upper limb rehabilitation robot (EULRR) designed in SolidWork.  
Figure 2: Three-dimension model of the handle.  
mean measurement of 355.8 mm (female) and 389.4 (male) at age 17. In the prototype of the EULRR, the base mounting distance is designed as 520 mm, which can be applied to patients with different shoulder widths. Considering the connection and comfort between the hand of patients and the end of the robot, the end handle width of the EULRR is designed to be 120 mm [36]. Besides, the height of the seat could be adjusted to adapt to the height of different people, and the position of the seat could also be adjusted forward and backward. The display screen is installed on the column of the robot body, which is mainly used for debugging. There is also a removable additional screen for the training scene, placed in front of the patient, which is not shown here.