ESC-Integration

ESC – an important part of a whole.
In many countries, ESC is already mandatory. In the rest of the world, it will become mandatory in the near future. It is therefore becoming increasingly significant during the development of new models to take under consideration the implementation of ESC and its components into the overall vehicle. The selection of appropriate hardware and components depends on many parameters i.e. brake circuit layout and which value added functions will be implemented.

Bosch offers expertise in order to be able to technically support customers as well as a large selection of sensors and hardware for individual requirements:

• Passive, active or active-intelligent wheel speed sensors (WSS) measure the speed of all four wheels. Passive sensors can measure the rotational speed. Active sensors however can also sense the direction of travel. This information can be used for a park assist function.
• The steering angle sensor (SAS) senses the driver’s steering request. This sensor exists in many types so that in some cases it can also fulfill specific requirements of special ESC functions i.e. Rollover Movement Functions (RMF).
• Positioned at the vehicles center of gravity, the yaw rate sensor (YRS) measures both lateral acceleration and yaw rate. If requested, a longitudinal sensor can also be integrated in this component for certain value added functions i.e. for Hill Hold Control (HHC).
• A brake pressure sensor measures the brake pressure in the master cylinder (HBZ) and therefore evaluates the deceleration request of the driver.
• The analysis of all the available sensor signals takes place in the ESC ECU. In combination with the hydraulic unit, it forms a component which is usually situated in the engine bay. With the use of a pump and the valves inside the hydraulic unit, active wheel specific vehicle stabilizing interventions can also be performed in parallel to ABS pressure modulation.

In order to process important vehicle signals, interfaces to the ESC ECU must be defined. In this network, information from the vehicle databus (CAN, Flex-Ray, etc.) is read and processed. Examples of important input signals are the engine torque output, the selected gear or the status of the brake light switch. Important signals which are sent out from the ESC ECU are for example the requested engine torque, the vehicle speed used by the instrument cluster, and the ESC status lamp.

The correct integration of ESC into the overall vehicle is very important in order to satisfy specific customer requirements. Therefore, the selection of appropriate ESC components as well as the proper definition and use of the required interfaces are quintessential in order to provide a successful product.