Electric cars are something that show up in the news all the time. There are several reasons for the continuing interest in these vehicles: Electric cars create less pollution than gasoline-powered cars, so they are an environmentally friendly alternative to gasoline-powered vehicles (especially in cities). Any news story about hybrid cars usually talks about electric cars as well. Vehicles powered by fuel cells are electric cars, and fuel cells are getting a lot of attention right now in the news. An electric car is a car powered by an electric motor rather than a gasoline engine. From the outside, you would probably have no idea that a car is electric. In most cases, electric cars are created by converting a gasoline-powered car, and in that case it is impossible to tell. When you drive an electric car, often the only thing that clues you in to its true nature is the fact that it is nearly silent. Under the hood, there are a lot of differences between gasoline and electric cars: The gasoline engine is replaced by an electric motor. The electric motor gets its power from a controller. The controller gets its power from an array of rechargeable batteries. A gasoline engine, with its fuel lines, exhaust pipes, coolant hoses and intake manifold, tends to look like a plumbing project. An electric car is definitely a wiring project. In order to get a feeling for how electric cars work in general, let's start by looking at a typical electric car to see how it comes together.
Engine Control Unit
An ECU (Engine Control Unit) is also known as PCM (Powertrain Control Module). ECU is a type of electronic control unit that controls a series of actuators on an internal combustion engine to ensure optimal engine performance. In modern cars, it is almost impossible to build an emission-passing car without an ECU. A modern ECU might contain a 32-bit, 40-Mhz processor. The code in an average ECU takes up less than 1 megabyte of memory. ECU controls everything, such as, air/fuel ratio, ignition timing, idle speed, variable valve timing, etc.
• Control of Air/Fuel Ratio
For an engine with fuel injection, an engine control unit (ECU) will determine the quantity of fuel to inject based on a number of parameters. If the throttle position sensor is showing the throttle pedal is pressed further down, the mass flow sensor will measure the amount of additional air being sucked into the engine and the ECU will inject fixed quantity of fuel into the engine (most of the engine fuel inlet quantity is fixed). If the engine coolant temperature sensor is showing the engine has not warmed up yet, more fuel will be injected (causing the engine to run slightly 'rich' until the engine warms up). Mixture control on computer controlled carburetors works similarly but with a mixture control solenoid or stepper motor incorporated in the float bowl of the carburetor.
• Control of Ignition Timing
A spark ignition engine requires a spark to initiate combustion in the combustion chamber. An ECU can adjust the exact timing of the spark (called ignition timing) to provide better power and economy. If the ECU detects knock, a condition which is potentially destructive to engines, and determines it to be the result of the ignition timing occurring too early in the compression stroke, it will delay (retard) the timing of the spark to prevent this. Since knock tends to occur more easily at lower rpm, the ECU may send a signal for the automatic transmission to downshift as a first attempt to alleviate knock.
• Control of Idle Speed
Most engine systems have idle speed control built into the ECU. The engine RPM is monitored by the crankshaft position sensor which plays a primary role in the engine timing functions for fuel injection, spark events, and valve timing. Idle speed is controlled by a programmable throttle stop or an idle air bypass control stepper motor. Early carburetor-based systems used a programmable throttle stop using a bidirectional DC motor. Early TBI systems used an idle air control stepper motor. Effective idle speed control must anticipate the engine load at idle.
A full authority throttle control system may be used to control idle speed, provide cruise control functions and top speed limitation.
• Control of Variable Valve Timing
Some engines have Variable Valve Timing. In such an engine, the ECU controls the time in the engine cycle at which the valves open. The valves are usually opened sooner at higher speed than at lower speed. This can optimize the flow of air into the cylinder, increasing power and fuel economy.
Hybrid cars
Hybrid cars are the most important evolution to a Carbon Neutral way of driving, because most of the time you only drive short ways. So you can go full electric and also it’s possible to have a longer range with the combustion engine. There are different types of the concept for hybrid power cars.
Different system structures
• Series hybrid: Series-hybrid cars are driven by the electric motor with no mechanical connection to the engine. Instead there is an engine for running a generator to get the energy for the electric motor.
• Parallel hybrid: In a parallel hybrid car, the single electric motor and the internal combustion engine are installed such that they can power the vehicle either individually or together.
• Power-split hybrid: In a power-split hybrid electric drive vehicle there are two motors, an electric motor and an internal combustion engine. The power from these two motors can be shared to drive the wheels or regenerate power for the batteries.
Different Hybrid types
• Mild hybrid: These types use a generally compact electric motor to provide auto-stop/start features and to provide extra power assist during the acceleration, and to generate on the deceleration phase
• Full hybrid: Full hybrid vehicles with an electromotive power of more than 20 kW / t can purely drive on electric power and therefore it is the basis for a series hybrid.
• Plug-in hybrid: The plug-in hybrid is usually a general fuel-electric (parallel or serial) hybrid with increased energy storage, usually through a li-ion battery, which allows the vehicle to realize a full –electric drive mode. The distance depends on the battery size and its mechanical layout.
Sensors and Radar
There are a lot sensors and radar systems in our cars. We use them every day, mostly we don’t know that they exist. The most popular sensors are parking-, fuel-, temperature- and ultrasound-sensors. The word sensor comes from the Latin and means feel. It is a component, which can detect physical or chemical properties. For example: Sunshine, temperature, pressure, brightness, PH, Ion-Intensity, and much more. In the following I will explain the most popular sensor in a car: 1. Parking Sensors Parking Sensors measure distance between you and another car. In the beginning they started with passive systems. For example: At a lorry were extra flexible components at the fender, which can be used from the driver as landmarks by parking. But today, we have mostly active systems:
Ultrasound Systems
Ultrasound Systems are mounted at the bumper of the car. You can distinguish between 2-, 4- or 6-Sensors. The more sensors, the more accuracy. These sensors send and receive ultrasound. On this way the Signals will be evaluated from the control unit. The control unit compare the sender signals with the receiver signals and calculate than the distance. The first working ultrasound system in a car were produced from Toyota 1982 for the middle class car Corona.
Radar Systems
Parking aid with radar systems is possible since the development of the short wave millimetre wave radar. The method is the same like the ultrasound system. But here, you don’t need extra sensors in the bumper. The distance adjustment system will be used also for parking aid. You won’t have extra costs, but sometimes when it’s raining the radar system gives you wrong signals, because the water is running on the bumper.
Airbag
The Airbag was created to reduce the danger of injury while a car crash as low as possible. The owner of the Patent is Walter Linderer and he created the airbag in 1951. In general the Airbag is controlled by a airbag-controle-system. This is controled by crash sensors. To not a start the airbag by accident there are also sensors in the car who send signals depending on how hard something colides. If those sensors get activated the airbags pop out of their case and protect driver and co-drivers.
Sources
1. Parking aid: 18.01.2015 at 1:17pm
http://de.wikipedia.org/wiki/Einparkhilfe
2. Sensors: 18.01.2015 at 2:38pm
http://www.kfztech.de/kfztechnik/elo/sensoren/sensoren.htm
3. Sensors: 18.01.2015 at 4.03pm
http://de.wikipedia.org/wiki/Sensor
4. Engine Control Unit: 21.01.2015 at 10.53 am
http://en.wikipedia.org/wiki/Engine_control_unit