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Introduction:
An actuator is a component that contains electronic parts and, when voltage and current are supplied to it by an ECU, takes action. This can range from adjusting a mechanical position to regulating a particular 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 air-fuel mixture of a gasoline engine is too lean, the oxygen sensor (sensor) measures an excess of oxygen. The ECU commands the injector (actuator) for a longer time until the oxygen sensor signal has reached its desired value. In doing so, the ECU has a regulating function. See also the page: procesregeling.
Actuator control:
The ECU sends current through the actuator by switching a positive, or in most cases, switching the ground. The actuators translate the ECU’s electronic signals into physical movements or actions. Actuators often contain a coil or electric motor that can carry out a command. We also find actuators as an electric motor (stepper motor), as a heating element, or as lighting.
Actuators with a coil:
- EVAP charcoal canister purge valve
- Ignition coil
- Common-rail pressure regulator
- Alternator rotor
- Injector
- A/C compressor magnetic clutch
- Camshaft adjuster
- PWM-controlled fuel lift pump
- Relay
- Wastegate or VGT actuator
Example: the image next to this shows a relay circuit. The ECU switches the relay control current 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 for the main current is pulled closed.
Actuators with an electric motor:
- Door locks
- Electronic throttle body or idle air control valve
- Power-adjustable seats and mirrors
- Heater doors in the HVAC housing (automatic A/C)
- Headlight leveling motor
- Radiator fan
- Windshield wipers
- Sunroof
Example: the image next to this shows the wiring diagram of the power mirror adjustment. One actuator motor is for vertical adjustment and the other for horizontal. Polarity determines the direction of rotation of the electric motors, and thus which way the mirror glass is tilted. The ECU determines, based on the input signals, how the adjustment motors are controlled. This can be: based on the switch operated by the driver, the memory function, or when selecting reverse gear.
Actuators as a heating element:
- Rear window defroster
- Battery pack heater
- Fuel filter heater
- Auxiliary heater for cabin ventilation
- Mirror glass heater
- Seat heater
- Steering wheel heater
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 coils heat the incoming cabin air. The ECU switches pulsed voltages to one or more glow coils to bring the component up to temperature as quickly as possible, and then keeps it at the desired temperature with a reduced current.
Actuator for lighting functions:
- Dashboard (warning) lights
- Lighting in headlamp and taillamp assemblies
Example: to limit the power of lighting, or to give a lamp multiple functions, incandescent bulbs, but also LEDs, are controlled by the ECU. In the image next to this we see a lamp that is controlled by a duty-cycle. The pulse width determines how brightly the lamp lights up. The lamp can now function as a taillight (25) or as a brake light (90%).
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