# Configuration Design of an Upper Limb Rehabilitation Robot with a Generalized Shoulder Joint
## 7 Experiment  
The kinematic analysis, inverse kinematics solution and kinematic performance analysis of the two configuration design schemes show that the kinematic performance of \(5R_{a}1P\) is better, so a prototype of the \(5R_{a}1P\) configuration was built, as shown in Figure 22. The prototype has a generalized shoulder joint, which can realize 5-DOF movement at the shoulder joint; the elbow joint, forearm joint and wrist joint each have one active DOF.  
Particularly, two passive DOFs are added to the forearm man-machine contact component, which are the freedom of rotation around the forearm axis and the freedom of movement in the axis direction, as shown in Figure 23. By setting four nylon rollers, the forearm support ring is fixed on the virtual circular track, the support ring is equipped with a linear guide and a slider, and the strap is internally fixed on the slider to realize the two passive DOFs of the forearm man-machine contact parts. A spring is added between the forearm support ring and the nylon roller support frame. Two identical compression springs are placed on both sides of the sliding block in the support ring. An elastic element is added to the mechanical structure of the passive pair to make the passive pair have a certain degree of flexibility during movement, relieving the uncertainty of exercise and the  
Figure 21: Manipulability ellipsoid of \(5R_{a}1P\) in the horizontal plane. (**a**) \(\alpha=30^{\circ}\); (**b**) \(\alpha=60^{\circ}\); (**c**) \(\alpha=90^{\circ}\); (**d**) \(\alpha=120^{\circ}\).  
Figure 22: Prototype of \(5R_{a}1P\) configuration.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Plane**} & \multicolumn{4}{c}{\(2P_{a}1P3R_{a}\)} & \multicolumn{4}{c}{\(5R_{a}1P\)} & \multirow{2}{*}{**Dominant**} \\ \cline{2-3} \cline{5-10}  & \(30^{\circ}\) & \(60^{\circ}\) & \(90^{\circ}\) & \(120^{\circ}\) & \(30^{\circ}\) & \(60^{\circ}\) & \(90^{\circ}\) & \(120^{\circ}\) \\ \hline \(30^{\circ}\) coronal plane & 0.24 & 0.45 & 0.57 & 0.45 & 0.2 & 0.32 & 0.56 & 0.42 & \(-0.21\) \\ sagittal plane & 0.25 & 0.45 & 0.57 & 0.45 & 0.23 & 0.23 & 0.94 & 0.44 & 0.12 \\ horizontal plane & 0.57 & 0.57 & 0.57 & 0.57 & 0.56 & 0.56 & 0.94 & 0.62 & 0.4 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Comparison of operability ellipsoids of the \(2P_{a}1P3R_{a}\) and \(5R_{a}1P\).  
instability of exercise coordination. Friction was avoided between the support ring and the patient's skin, discomfort was avoided, and the patient was restrained.  
Due to the safety of patient movement, the prototype was designed with mechanical limits in structure. The rotational range of the shoulder 1 movement module is 0\({}^{\circ}\)\(\sim\)110\({}^{\circ}\); the rotational range of the shoulder 2 movement module is \(-\)90\({}^{\circ}\)-30\({}^{\circ}\); the rotational range of the shoulder 3 movement module is \(-\)60\({}^{\circ}\)-90\({}^{\circ}\), in which the shoulder 1, shoulder 2 and shoulder 3 movement modules correspond to the three intersecting rotation axes of the shoulder joint in sequence so that the prototype can move along the maximum space boundary to realize several kinds of movement states of human upper limbs, as shown in Figure 24.