Body Control Module

Introduction

Body Electronics is one of the fastest growing application segments within the automotive environment. In fact, the expansion of ECUs throughout the vehicle has created a need for expanded communications that has led to the "networked vehicle." With body controllers implementing functions that control seats, windows, door locks, airflow, lighting and wipers, the comfort and safety subsystems of the vehicle are directly impacted by the performance of body control ECUs.

What is Body Electronics?

The Body Electronics is a term used for the electronics involved in various Vehicle body functions. The most important component is Body Control Module or Body Control ECU's. There can be many BCM's in a vehicle. The Body electronics may also include the electronics involved in sensors and actuators.

In many texts the term Body Electronics is used for BCM but in general it is the electronics involved in the whole system.

What is a Body Control Module?

Body Control Module refers to the computer system in Automotive that controls systems like power windows, power locks, interior light, etc. Body Control Module generally refers to those things not controlled by engine, transmission, brake, etc. Body Control Module (BCM) is also known as Body control electronic control units (ECUs).

The Body Control Module (BCM) checks, regulates and operates electronic devices throughout the car. It supplies vehicle occupants with visual and aural information and controls various vehicle functions, to provide and receive information; the module is interfaced to the vehicle's serial bus communications network.

Many of the vehicle body functions can be controlled from a central body controller and is referred as Centralized system. Often the vehicle architecture distributes some of the processing to other local nodes which is referred as Distributed system.

Block Diagram of a Body Control Module

Photo Source: ehow.com

Why Body control Modules is required?

When electric devices were first began being used in cars and trucks, each device had a separate electric component to govern it. There was a module for the air conditioning, a module for the interior lighting, a module for the door locks and so forth. A body control module gathers all these separate modules under one system so that they function together instead of separately, a format easier to both manufacture and troubleshoot.

Typical Body control module improves the comfort and safety of vehicle occupants. Advancements in body control modules is an essential element in the ability of car manufacturers to produce smarter vehicles that are pleasing to drive, reliable and safer. Body control modules improve the safety factor of a vehicle by simplifying the operation of the vehicle and relieving the driver of distractions from secondary activities.

What are the Applications of a Body Control Module:

Typical applications for the BCM include controlling units such as doors, steering wheel, seats and motors and sensors in climate control, lighting, rain sensors, smart wipers, intelligent alternators, switch panels and RF receivers. These units can be easily connected to the car network using vehicles serial communication bus (CAN/LIN or any other) and become accessible to all types of diagnostics and services.

The BCM can provide the following features:
• Automatic door locks
• Battery protection
• Courtesy lamps
• BCM diagnostic support
• Door lock inhibit
• Headlamp time delay
• Ignition key lamp
• Power door locks (with/without remote keyless entry)
• Vehicle Theft Security system (VTSS)
• Windshield wipers / washers (front and rear)

What are the Components of a BCM?

While there are many different types of body control modules, they are generally alike, connecting sensors, switches and automatic reactions together in one computer system. These components are divided into inputs, such as sensor data about heat or speed, and outputs, or ways in which the body control module computer responds to control the vehicle's electronic functions. Inputs and outputs are further divided into analog and digital types of information, analog signals being used with modules that may change continuously (such as oil pressure) and digital signals being used for modules that can simply be on or off (like the headlights or the oil indication light).

Inputs and Outputs

Input components are divided into electric parts, such as the potentiometer, the variable resistor, the magnetic pickup and the voltage generator. A potentiometer is designed to change a voltage output to the computer, so that when a fuel setting or gas pedal position is changed the voltage will change, and the computer will be able to read the new voltage and respond accordingly. The variable resistor works in a similar fashion, but senses changes in temperature for reading engine coolant conditions and other data. The magnetic pickup reads the speed of a rotating object via a simple magnet attached to the object, and a voltage generator sends out a voltage signal based on the presence of compounds like oxygen so the computer can tell the oxygen-rich levels of a pipe or space.

Output devices consist of relays, solenoids, servomotors, switching transistors and others. Relays can turn other devices on and off by connecting or disrupting a circuit to turn on a fan or automatic air conditioning unit. Solenoids are analog components that use magnetic forces to move objects, such as fuel injectors. A servomotor is a mini-motor also used to move objects, usually to turn things, while a switching transistor is the digital version of a relay. Other output devices are very simple, such as LED lights, or very complex, such as a night-vision view of the road.

Computer Tasks

The body control module computer itself performs many of the functions of a normal computer, including storing data, using RAM, and sending or receiving radio waves. It is the computer's job to regulate many of the systems and troubleshoot all of its component modules. Some modules are set by timer, which the computer digitally keeps track of, while other modules like the anti-theft alarm need to be kept active even when the car is turned off.