Actuators have played a pivotal role in the evolution of the automobile; you could argue that the modern day car as we know it could not exist without them. Cars have always needed relatively simple motors to drive their internal devices, and the technology used has evolved over time to keep pace with modern developments. Cars originally had a lot of analog mechanical actuators that would make things go. Consider 'manual' windows; you turned a hand crank in the door and sheer mechanical advantage would get that window up and down. Adjusting your seat's legroom meant sliding up and down a ratchetted rail on a coil spring. The technology has come a long way, but what most people don't realize is that a lot of that progress is because of advances in actuators.

Specific Automotive Actuator Examples

The average modern car rolling off the line this year will have over 100 hydraulic, pneumatic, and electric actuators in it, and the number only increases as the price of the car does. All of these things we used to do ourselves are now handled sleekly and silently by various actuators, servos, and motors.

Door Locks: Remember the old days? Literally pulling that knob up to disengage the lock, all elbow grease and muscle power. Nowadays there is an electric linear actuator mounted inside the door frame assembly, powered by the car battery. Since the lock actuator is powered by electricity it doesn't require your muscles to move it anymore, and can be triggered by anything, regardless of the original force involved. Pushing a button on a remote key fob, entering a combination on the outside of the door, or just pressing the unlock button on the arm rest. Because of other advances in gearing, levers, and much lighter construction, the amount of force required to disengage the lock is tiny in comparison to what it was in the old days, meaning the linear actuator involved doesn't even have to be that powerful.

Power Steering and Power Brakes: Steering and braking in the past was a lot harder than it was today. You would have to exert far more pressure on the wheel to turn, and the steering system itself was often hooked up to a complicated series of linkages to multiply the force you did exert. The same was true of braking systems; you actually had to press the brake pedal hard enough to force the drum to engage with the wheel rim manually. Thankfully now we have hydraulic and electric actuators that magnify the pressure you apply while driving and braking considerably. This technology first appeared on (luxury) cars in 1951, though the US military had been using it for specialized vehicles since World War II.

Everything That Used to be on a Spring: You used to 'pop' your hood or trunk by releasing a latch, and then a powerful spring would push open the front or back of the car. While both still use latches to stay closed, most modern cars use an (usually hydraulic or pneumatic) actuator to provide controlled upward lift to the hood or trunk. Some car hobbyists install a linear actuator solution; since linear actuators can easily go forwards and backwards this means that hood or trunk can be opened and closed without having to get out and slam them. Several other simple spring and lever based devices that were formerly powered manually have been replaced by actuators: Automatic gas caps are opened by a simple electric linear actuator. Headlight covers open and close with pneumatic actuators. Even the air conditioning and heat vents can now be adjusted with chain or linear actuators.

Fuel Injection and the Engine: The most important part of the car, the engine, has evolved considerably alongside actuator technology. The most essential of which are the actuators used to drive the various valves in the engine, which control fuel flow rate, air mix, exhaust air, recycling and more. There are too many actuators (and actuator types) involved to go into specific detail, but these are some of the things that actuators powering valves in your engine can do:

• Auto-start/no-touch start (actuator powered idle air bypass valve)
• Greatly enhanced fuel efficiency (actuator powered fuel injection valves)
• Adjust and monitor engine timing without having to use the old standby's of vacuum chambers or frame weights
• Reduced air pollution from actuator switched valves recirculating exhaust air, or injecting clean air to burn off impurities

All in all, there's quite a lot of actuating going on inside your average car, to the point where it's difficult to imagine what a modern car would even be like without them. This applies to all vehicles, with the number and complexity of actuators increasing for planes, boats, submarines, and helicopters.