How do actuators in fly-by-wire systems on aircraft work?

[lucy_b14]

Hi, I'm doing some research into fly-by-wire system on aircraft and need some more information on actuators. I know that electrical signals are sent to the actuator from an onboard computer, but I'm not sure how the actuators then move the control surfaces. Do they use hydraulics? If so how do they convert the electrical signal into movement in the hydraulic system. From my knowledge of hydraulics I know that some form of force needs to be applied to move the piston. Is an electric motor used for this?

Thanks, any help will be appreciated.

 

[Integral]

I would suspect that for the controls of of an RC plane you would want a small stepper motor. These can be quite small and can be given digital commands to move a small fraction of a revolution. This would give you very good control of your aircrafts control surfaces. Hydraulics require heavy fluids and pumps and still must be controlled by an electric motor of some sort.

My money is on a stepper motor. Simple, direct,, but somewhat expensive. If you only needed 2 positions then you could use a cheaper DC motor.

 

[FredGarvin]

The older fly-by systems used a combination of electrical and hydraulics. The electrical signal was sent to a solenoid valve and was controlled using a scheme called Pulse Width Modulation. This essentially allowed for extremely fast actuation and positioning of a hydraulic actuator. The newest version I can think of is on the new Airbus A380 which uses both electrical and hydraulic. Refer to the paragraph entitled "Dual Architecture System."

http://www.fpweb.com/archive/aerospace1202.html


The trend now is toward all electrical systems, thus greatly reducing the weight required for hydraulic systems.

http://www.afrlhorizons.com/Briefs/0006/VA9902.html