Topics:
Introduction:
An actuator is an object that contains electronic components and, when voltage and current are supplied by an ECU, takes action. This can range from adjusting a mechanical position to regulating a specific function within a vehicle or other controlled system. Every modern vehicle contains dozens of actuators in the engine compartment, the exterior, and the interior.
The ECU determines how the actuator should be controlled based on the sensor data and the program. Example: when the mixture of a petrol engine is too lean, the lambda sensor (sensor) measures an excess of oxygen. The ECU drives the injector (actuator) for a longer time until the signal from the lambda sensor has reached its desired value. The ECU thus has a regulating function. See also the page: process control.
Control of the actuators:
The ECU sends a current through the actuator by switching on a positive supply, or in most cases, the ground. The actuators translate electronic signals from the ECU into physical movements or actions. Actuators often contain a coil or electric motor with which a command can be executed. We also find actuators as an electric motor (stepper motor), as a heating element or as lighting.
Actuators with a coil:
- Evaporative emissions (activated carbon) canister purge valve
- Ignition coil
- Common-rail pressure regulator
- Alternator rotor
- Injector
- Magnetic clutch air-conditioning compressor
- Camshaft adjuster
- PWM-controlled fuel feed pump
- Relay
- Wastegate or VGT adjuster
Example: the illustration next to this shows a relay circuit. The ECU switches the control current of the relay on or off. When pin 85 is switched to ground by the ECU, current flows through the relay coil and it becomes magnetic. As a result of the magnetic field, the switch of the main current is pulled closed.
Actuators with electric motor:
- Door locks
- Electronic throttle valve or idle control valve
- Electrically adjustable seats and mirrors
- Heater flaps in heater housing automatic air conditioning
- Headlamp adjustment motor
- Radiator fan
- Windscreen wipers
- Sliding / tilting roof
Example: the illustration next to this shows the diagram of the electric mirror adjustment. One adjustment motor is for vertical adjustment and the other for horizontal. The polarity determines the direction of rotation of the electric motors, and thus to which side the mirror glass is tilted. The ECU determines how the adjustment motors are controlled based on the input signals. This can be: via the switch operated by the driver, the memory function, or when reverse gear is engaged.
Actuators as heating element:
- Rear window defogger
- Battery pack heater
- Fuel filter heater
- Auxiliary heater for interior ventilation
- Heated mirror glass
- Seat heating
- Steering wheel heating
Example: when an actuator has a heating function, the temperature is limited by a PTC. In this example we see an auxiliary heating element in which glow spirals provide the heating of the incoming interior air. The ECU switches pulsed voltages on one or more glow spirals to bring the component up to temperature as quickly as possible, and to keep it at the desired temperature with a reduced current.
Actuator for lighting functions:
- Dashboard (warning) lights
- Lighting in headlamp and taillight units
Example: to limit the power of lighting, or to give a lamp multiple functions, incandescent bulbs as well as LEDs are controlled by the ECU. In the illustration next to this we see a bulb that is controlled by a duty cycle. The pulse width determines how bright the lamp will shine. The lamp can now function both as tail light (25%) and as brake light (90%).
Related page: