Body Vertical Accelerometers

Three body vertical accelerometers are used in the AD system:

• A front body vertical accelerometer is attached to the body behind the right front wheel, on the front side member to dash gusset.
• A rear body vertical accelerometer is installed on each side of the luggage compartment, attached to the related rear quarter panel.

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

Each body vertical accelerometer is connected to the ISCM 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 ± 0.05 v/g.