Modules Physical Placements

In the previous section, the electrical layout of the module interconnects were depicted in Fig. 1.9 , which is the representation of how the modules are electrically interconnected in a typical vehicle. In this section we will try to give you a brief summary about where the modules are physically installed at different mounting locations and how the modules are connected through the harness and connectors.

A vehicle module is normally attached to the vehicle body or chassis or to the vehicle cockpit by a mounting scheme. The mounting scheme may or may not use a bracket depending upon many factors i.e. space, weight, function and mounting location. An air suspension module, for example, can be attached to the vehicle body by using a bracket; however, an airbag must not be attached to the vehicle body rather it has to be attached to the vehicle chassis directly. Instrument panel on the other hand must be fi tted inside the cockpit, visible to the driver at all times and the engine controller must have to be fi tted inside the engine compartment to gain all the electrical advantages.

We now review some of the modules locations in a typical vehicle.

1.33.1 An Airbag Module

An air bag module, for example, must be rigidly attached to the vehicle chassis and does not require any bracket attachment. The module electronic circuits are mounted inside a safe-casing comprises of a cover and the housing. The cover and the housing must be made up of metal or rigid material to get the accurate vehicle movements.

Plastic material could also be used on a simple rule: if the module is installed inside the passenger cabin or inside the trunk. It is safe from the external environment (dust, dirt, water, chemicals, and large variations of temperature), then it can be encapsulated in a plastic cover. However, this is just one key factor, and there are many other factors that need to be considered before deciding about the type of casing.

An example of airbag module is shown in the Fig. 1.36 . The airbag module is rigidly attached to the chassis because the accelerometers that are mounted inside the module demand accurate readings of vehicle movements. The module installa-tion locainstalla-tion and x, y, z direcinstalla-tions are highly critical for the crash impact detecinstalla-tion, and measurement. The module connector mating harness is not shown for the sake of clarity.

1.33.2 An Instrument Cluster

The instrument cluster is installed in the instrument panel (IP) with the aid of mounting screws or by other mechanical means or by a well-defi ned mounting scheme. The instrument cluster is located in front of the driver. However, in

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recent years, some manufacturers have tried to shift the instrument cluster towards the center of the cockpit. Nevertheless majority of vehicles still have instruments clusters installed in front of the driver. Irrespective of where you place the instrument cluster, the basic philosophy is to show the clear display of critical vehicle parameters. The Fig. 1.37 shows the Instrument Cluster com-prises of engine temperature indicator, engine revolutions indicator, Fuel tank indicator and Odometer clearly placed right in front of the driver. If the vehicle is driven by right-hand rules in the target market then all the instruments must follow right-hand rules of the cockpit.

1.33.3 Multimedia, Location

The radio, cassette, compact disc, USB or any other audio related functions are grouped as multimedia components. The multimedia components are generally mounted in the center of instrument panel near the center pedestal. The basic

Direction of Impact

Mating Connector

Direction of Impact

Airbag Module Direction of Impact

Vehicle Chassis Top View

Fig. 1.36 Airbag module installation location

MULTIMEDIA RPM SPEED

TEMP. FUEL

HVAC CONTROLS Message Center

Fig. 1.37 Cockpit or instrument panel ( front view ) 1.33 Modules Physical Placements

philosophy of the installation location is to have easy access by the customer for the display and the controls (Buzz word → HMI→ meaning human Machine Interface). In Fig. 1.37 , the multimedia components are placed to the center of the cockpit

1.33.4 Climate Controls

The heating ventilation and air-conditioning (HVAC) controls are mounted to the center of the cockpit or closer to the center pedestal. Again, the basic philosophy of the installation location is to have easy access by the customer for the display and the controls (Fig. 1.37 )

1.33.5 Engine Controller

The engine controller is typically installed in the engine compartment—a location very well-justifi ed for many reasons, and has proved that the location closer to the engine makes it closer to sensors & actuators which are critical for many engineer-ing underlyengineer-ing principles. For example, a shorter distance to the controllengineer-ing and sensing mechanism shortens the overall wiring lengths, increases the effi ciency for the high current switching with better controls and electro-magnetic compliance performance. The location of engine controller shown in the Fig. 1.38 is one exam-ple. However, the location varies as per needs and wants of the design and develop-ment team. No matter where the fi nal location could be selected by the OEM for a vehicle platform, the engine controller resides inside the engine compartment (under the hood). The functions and features governing the fi nal decision to select the loca-tion are governed by the technology, engine type, and physical-size, wiring and real state in the compartment.

1.33.6 Anti-Lock Brake (ABS) Module

The anti-lock brake electronics module is frequently married to the hydraulic- assembly that is attached to the pump-motor. The pump-motor generates the necessary brake fl uid pressure transfers through the hydraulic lines to the hydraulic valves, which acts as a gateway to the fl uid dynamic forces to operate on individual wheel-braking mechanism. The preferred installed location ought to be closer to the brake-booster and master-cylinder (Fig. 1.38 ).

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1.33.7 Power Steering Module Location

The electrical steering assisted electronics-module is typically placed next to the steering control assembly, thus making it easy to connect to the high-current motor to a shorten the electrical distance, which is a great benefi t for the high current power devices. As mentioned earlier, the steering system still keeps the mechanical linkage to the wheels; however, the electrical motor is used to assist steering efforts.

In Fig. 1.38 the steering control module is shown mounted on top of the steering assist motor—clearly showing the steering wheel mechanically connected to the steering system as well. Failure to the motor or the electronics may cause extra efforts needed to steer the vehicle, but total system failure would not occur.