# A Novel Soft Robotic Exoskeleton System for Hand Rehabilitation and Assistance Purposes
## 2 Development of the SEG Device
### Development of the SEG Device's Hardware  
Besides the soft actuators, there are some other components that complete the hardware of the developed SEG device, namely the control glove, the electro-pneumatic control system, the rest of the electronics, and the components of the housing. In the current section, the structures of these aforementioned components are presented thoroughly.  
The control glove is an additional glove applied to the healthy hand, and its objective is to capture motion data in order to use it for the control/motion of the SEG. In the control glove, there are five one-axis soft flex sensors, namely the Bend Labs Digital Flex Sensor, one for each finger, in order to capture the finger's motion. These bend sensors utilized the variable capacitance technology offering high accuracy and reliability with low power consumption. The other parts of the control glove are the controller configuration (PCB) and the battery. As is depicted in Figure 4, the PCB consists of the microcontroller (MCU) embedded with a WiFi module, the power management module, the sensors readoutcircuitry, other buttons, LEDs, and terminals. It is important to highlight that as MCU hardware, the module Esspresif ESP32-WROOM-32 was utilized. In addition, the control glove was designed to operate autonomously in terms of power due to the existence of a Lithium Polymer (LiPo) battery. Figure 4 shows the overall configuration of the control glove and its components.  
Figure 4: The overall configuration of the control glove and its components.  
Figure 3: (a) 3D design; (b) Physical model of the actuator’s core; (c) Final configuration of the developed actuator for the SEG application [28].  
The next critical module of the SEG device is the electro-pneumatic system that controls the motion of the applied soft actuators. The developed electro-pneumatic system was designed to receive pressurized air above 300 kPa and regulated at 200 kPa, which is considered the optimum value for the actuators in terms of force and durability. The pressurized air could be provided by a preinstalled pneumatic system or by a portable air pump, and the regulation of the air pressure inside the SEG device was performed with a pressure regulator. Having achieved the optimum air pressure inside the device, the next step was the selection and set-up of the electromagnetic valve system that controls each actuator. For this purpose, the TX miniature switching solenoid valve was utilized due to its small size allowing the portability of the pneumatic system. More specifically, for each actuator, three micro-valves were employed in order to allow the intake of pressured air and the outtake of the free flow in a controllable manner. Figure 5a portrays an illustration of the flexion (left side) and extension (right side) of a single actuator coupled with the schematic diagram of the pneumatic circuit. The C1 and C0 point out the condition of the valve for active or disabled status, respectively. Furthermore, the overall 15 valves are controlled via an MCU (Esspresif ESP32-WROOM-32), and the control system and the valves are positioned on a PCB. In Figure 5b, the overall pneumatic circuit is presented, coupled with the configuration of the PCB. The other electronics include power buttons, reset buttons, power and USB connector, etc. All electronics and the electro-pneumatic system were positioned on a metal case fabricated via sheet metal processing apart from the PCB and battery for the control glove that was placed into a customized 3D-printed case on the glove.