In passenger vehicles, an electric parking brake (EPB) is used to hold the vehicle still on a flat, graded road. This is achieved by measuring the dip Angle with a uniaxial or biaxial accelerometer. The general practice is to mount an X /Y or Z low g accelerometer in a dedicated module in the EPB control unit. More and more cars now come with an ESC (electronic stability control) function that incorporates a combined low-g accelerometer and gyroscope in a single chip. This is to prevent the car from skidding and turning over; Nowadays, the function of ESC has become a mandatory requirement of laws of various countries or regions in the world. If obliquity is measured using a combination of components (a single chip, a combined accelerometer, and a gyroscope), there is no need to install a separate EPB module in the vehicle, resulting in a significant reduction in vehicle costs. Since composite devices are usually used in ESC, they are not optimized for inclination detection, and the measurement accuracy sometimes fails to meet the requirements when the inclination is measured by composite devices. Since the assembly is the XY or XYZ axis, the X axis is usually used for inclination measurements, and part of the conventional low-g accelerometer in the EPB module USES the Z axis because it is mounted vertically in the engine compartment. The axis should be perpendicular to gravity for greater accuracy — we’ll discuss this later.
Figure 1. Installation diagram of X – and z-axis accelerometers.
It is very important to evaluate the accuracy of inclination measurement in automobile. Might as well imagine, your car is parked in absolutely flat on the ground, as a result, the accelerometer Angle should be 0 °. If your car is parked on a ramp, the tilt should be accurately detected in order to activate the brake system correctly.
Figure 2. X axis detection inclination measurement diagram.