Modeling Bi-directional Wedge-type Segmented Soft Pneumatic Bending Actuator for Hand Rehabilitation using Finite Element Method

Models of different actuators for hand rehabilitation gloves have been sought by many developers. Hand rehabilitation exercises require flexion and extension of the fingers. However, existing actuators for this application do not conform to these requirements. In this paper, a bi-directional wedge-type segmented soft pneumatic bending actuator is proposed that could accomplish flexion and extension with positive and negative (vacuum) pressure, respectively. The model is simulated in finite element software and is characterized according to the varying pressure at each joint to its equivalent force depicted by each of the links of the finger. The results show that the model was able to bend in flexion -90
^○
at a pressure of 220 kPa and in extension at +15
^○
at -60 kPa pressure. An artificial neural network was set up with 2484 data sets as an inverse kinematic solution in deriving a pressure-to-bending angle function. An R of 0.99997 was obtained for both the training, validation, and test. The force and torque generated at the tip of each joint in an axial direction of the actuator have been evaluated to measure the actuator model's bending ability. This model can be used as an assistive device that can do hand rehabilitation exercises requiring flexion and extension such as tendon gliding exercises.