Development and Evaluation of a Low-Cost, High-Precision Sensor System for Mouth-Operated Joysticks

Mouth-controlled mouse emulation devices enable people with limited mobility of the upper limbs to control computers and other digital products. To be useable for persons with restricted head movement or low muscle strength, highly sensitive sensor systems are required. Devices available on the market do not provide such sensitivity or are very expensive. In this work, we explore the phenomenon of piezoresistivity in SMD thick film resistors and utilize this effect for a low-cost force sensor module for mouth-operated joysticks. A proof-of-concept implementation is presented, including the PCB layout and signal processing strategy. The system allows the application of strain-gauge sensors or piezoresistive sensing elements. A mouth-operated joystick based on the novel sensor design was validated under laboratory conditions. Fitts' throughput (TP) was calculated as a measure of performance, showing TP = 1.52 +/- 0.28 bits/s for the strain-gauge sensor and TP = 1.50 +/- 0.25 bits/s for the piezoresistive sensor. In a user study with 5 persons with different motor disabilities the system obtained excellent usability ratings. The SMD sensor module can be produced almost completely automatically, reducing the cost of mouth-operated joysticks.