Finger Displacement Sensing: FEM Simulation and Modelling of a Customizable Three-Layer Electrode Design

Home based or tele technological systems and smart devices have provided alternative delivery forms to promote hand rehabilitation. As a step towards the targeted system, a finite element method (FEM) simulation based on MGC3130 three-layer electrode design in Comsol®, and a nonlinear regression analysis using Matlab® were carried out. Concerning different combinations of fingers’ movement and the symmetrical structure of the simulation model, nine cases in total are simulated. In each case, there are ten testing points, ranging from 0mm to 30mm, to explore the inherent relationship between the distance changed from finger motion and the voltage signals detected in the receive electrodes. The results in both the original electrode design and the modified electrodes design agree with the quasi-static electrical near field theory and the symmetrical structure of the three-layer electrodes. Based on the simulation result, the functional relationship of the data was also investigated. The nonlinear equation, describing the performance of the electrode layers, fits well in both electrode designs, which implies a clear inverse relation between the changed distance and the detected voltage signals. The equation also reflects the sensitive and finite features of the design, which helps to guide and optimize the practical design of the electrodes in the future investigations. Keywords—finger movement detection; Comsol® simulation; capacitive sensor; electrode design; hand rehabilitation