Electronic Control (1)

Electronic Control (1)

 

Together with big technical advance in electronic industry, every side of our life is also being equipped with electronic devices and controllers, and our car is not an exception of this trend. The value of electronic part in our car is getting bigger every year, if electronic vehicle comes to our daily life the automotive industry can be categorized as a part of electronic industry, I think. At the moment there are a lot of electronic controller already in a vehicle, such as ECU (Engine Control Unit) which controls engine, TCU (Transmission Control Unit), ABS (Anti-Lock Brake System) which controls the brake fluid pressure to avoid wheel lock, and TCS (Traction Control System) which keep optimum traction force of the wheel on the road and VDC (Vehicle Dynamic Controller) which controls vehicle stability during braking and acceleration and Navigation System, ASS (Active Suspension System) and VIM (Vehicle Immobilizer). Several decades ago our father and grandfather have driven their cars without any kind of electronic devices. Then, what is the basic reason of adding more and more numbers of electronic control devices ?

 

 

The most powerful feature of electronic control unit is the calculation speed which human cannot do. Through the millions of calculation loops from micro processor the control unit can find an optimal control path of an actuator which leads much better performance of vehicle. This better or optimal controllability can lead eventually better fuel economy, of lower exhaust emission or better comfort and safety.

 

For example, ECU controls the fuel amount supplied into engine combustion chamber. The most important function of ECU is to keep the air-fuel ration to guarantee optimal combustion in the chamber. Decades ago when carburetor has played this role the air-fuel ration was controlled by a Venturi-tube which totally depends on physical relationship of nature. Of course the accuracy of the air-fuel ration was influenced quite a lot by several factors such as temperature and pressure changes which has lead again into higher amount of exhaust emission or lower fuel efficiency. Further more, a preset mechanical relationship can also be deviated by aging of the vehicle or engine.  This aging effect, the mechanical devices had no way to compensate it.

 

 

On the other hand, the ECU is checking air mass at every millisecond and calculate required fuel amount based on the calculated air amount and optimal air-fuel ratio. The amount of fuel is controlled by opening time of injector nozzle and fuel system pressure. We can imaging which way of control can offer better or precise control of air and fuel amount for optimal operation of an internal combustion engine.

 

A similar example can be found in ABS. The basic purpose of ABS is to avoid locking of wheel on the road which can lead losing of vehicle controllability by giving precise control of brake fluid pressure which presses brake pad on the wheel. To achieve the necessary controllability, the most important input signal is the wheel speed. By monitoring the wheel speed, the brake fluid pressure can be controlled by feed-back mode not to lock the wheel. Of course highly trained race driver can control the vehicle close to this optimal mode, but it is only possible after very long period of hard training.

 

To be continued at part (2)

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