Description And Operation: Accelerometers

Three accelerometers are used in the adaptive dynamics system. The accelerometers are located as follows:

• One each on the front edge of the LH (left-hand) and RH (right-hand) A pillars.
• One in the luggage compartment, in the rear LH corner adjacent to the rear lamp assembly.

The accelerometers measure acceleration in the vertical plane and output a corresponding analogue signal to the ADCM. The algorithms in the ADCM calculate the heave, pitch and roll motions of the vehicle, which are used by the controller to control road induced body motion.

Each accelerometer is connected to the ADCM via three wires, which supply ground, 5 V supply and signal return.

The sensing element comprises a single parallel plate capacitor, one plate of which moves relative to the other dependant on the force (acceleration) applied. This causes the capacitance to change as a function of applied acceleration. This capacitance is compared with a fixed reference capacitor in a bridge circuit and the signal is processed by means of a dedicated integrated circuit to generate an output voltage that varies as a function of applied acceleration. The sensors output a signal voltage of approximately 1 V/g ± 0.05 V/g. When the vehicle is stationary, each accelerometer outputs approximately 2 volts.