An any-resolution pressure localization scheme using a soft capacitive sensor skin

We present a method to determine the location of an applied pressure on a large-area, monolithic, silicone-based capacitive sensor. In contrast to pressure sensor arrays composed of n × n discrete sensors, we utilize a single sensor body with a single instrumentation interface to detect n pixels. We interrogate the capacitive sensor at different frequencies, thus modulating the effective length of the sensor. These interrogation frequencies are governed by the sensor's total capacitance and resistance, and the desired spatial resolution. We developed an analytical model to calculate the frequency response at different length segments of the sensor and used the results to determine the interrogation frequencies for experimental studies. We performed experimental tests on a 1 × n sensor strip and an n × n sensor sheet and showed greater than 90% accuracy in predicting the location of the applied pressure using a model generated by a multi-class kernel support vector machine. This approach towards distributed localization of point pressures greatly reduces the hardware complexity in comparison to discrete sensor arrays and increases the physical robustness of the system.