A Structural Design and Decoupling Method of a Flexible Capacitive Pressure Sensor for Measuring Spatial Force

This article focuses on the spatial force decoupling method of specially designed flexible capacitive structures. In previous work, multidimensional force decoupling was mostly understood as decouple the force along the three reference axes of
${x}$
,
${y}$
, and
${z}$
, but the multidimensional force decoupled in this article includes any angle in 3-D space, which we called space force. It was found that the capacitance of the pressure sensor is mainly affected by the opposite area and the distance between the electrodes, which can all be attributed to the variations of the displacement within the space of the four capacitors; more specifically, spatial forces are the main cause of displacement variations. Thus, the decoupling method can be abstracted into a mechanical model, from which the main elements of the force can be obtained. The designed capacitor as a whole is obtained one time by casting and curing the elastic material polydimethylsiloxane (PDMS) on a mold. The structure constitutes four capacitive sensors with air as the dielectric layer and copper sheets as the electrodes. The analysis of capacitance values in simulated data and the multicapacitor test platform built in the experiment not only verified the rationality of the calculation, but also measured that the sensitivity of the sensor is 0.00192, and the response time is 75 ms. Compared with the actual value, the calculated
$\alpha $
,
$\gamma $
, and
${F}$
value errors are 0.18°, 0.3°, and 0.025 N, respectively, which provide some insight into the application of sensors that decouple spatial forces.