The number of the initially activated sensor is memorised and used further as a reference point. The position of the moment pressure spot is then measured with respect to the reference sensor. In the different control sessions, the reference point may change due to slight differences in the user’s body position in the wheelchair. The head direction (forward, left and right) is judged with regards to this reference point. The correct calculation of the reference point is important for the smooth operation of the wheelchair system. After the initial contact areas have been selected, all sensor values in each area are sampled. The program starts to analyse the signals from the force sensors and converts them into smooth proportional signal that correspond to the orientation of the user’s head. Also, the program calculates the signals for the wheelchair speed from the amount of pressure to the headrest in the separate parts of the headrest. The output values are transferred to the output pins as PWM signals. The output values are inverted if the button for forward-backward motion is activated.