Embedded capacitive sensor system for hip surgery rehabilitation: Online measurements and long-term stability

We are developing an embedded system that measures the force between foot and insole with a low-cost laminated capacitive sensor matrix. The system is intended to guide a hip surgery patient to train the operated leg with a suitable force. In this paper, we present an embedded measurement system, which is able to estimate the total plantar force in real-time and to give instant feedback to a user. We also present a method for compensating the drift of capacitive sensors. A 5-hour long test measurement was made in order to validate the system. According to the preliminary test, the compensation method effectively prevents the drift of the baseline of the force reading.