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Author Topic: Servos?Motors?Actuators?Wad exactly are the differences?  (Read 8716 times)

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Offline BADBOY13Topic starter

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Servos?Motors?Actuators?Wad exactly are the differences?
« on: January 28, 2007, 10:27:56 AM »
hi.
I've been wondering...
wad exactly are are the difference between servos, motors and actuators....
the only thinkg i'm sure of is that servos and motors are different in that the power and direction of a servo can be controlled but that of a motor(DC) cannot. and that servos can be set to turn to certain angles more accurately than a stepper motor...
as for actauators, wad exactly are they?
they seem to be used inter-changably with "sevos" or "motors.
wad exactly are thay?
wad's the difference between servos, motors and acutators???

anyone care to explain???
thanks

Offline Steve Joblin

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Re: Servos?Motors?Actuators?Wad exactly are the differences?
« Reply #1 on: January 28, 2007, 06:30:38 PM »
I don't profess to be an expert, but usually the term "actuator" typically refers to a device that provides linear motion... like a piston, a rod is pushed in a linear manner when voltage is applied.

A motor is a device that provides rotational movement (like in a toy car, the motor spins a wheel (usually through gears to reduce the speed and increase the tourque).

A servo is a motor along with electronics that provides a feedback loop to the motor. A Servo is a small device that has an output shaft. This shaft can be positioned to specific angular positions by sending the servo a coded signal. As long as the coded signal exists on the input line, the servo will maintain the angular position of the shaft. As the coded signal changes, the angular position of the shaft changes. In practice, servos are used in radio controlled airplanes to position control surfaces like the elevators and rudders. They are also used in radio controlled cars, puppets, and of course, robots.

Offline Zeol

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Re: Servos?Motors?Actuators?Wad exactly are the differences?
« Reply #2 on: January 29, 2007, 05:21:34 AM »
I'm not an expert either, but I think an actuator (http://en.wikipedia.org/wiki/Actuator) is any device that turns an input signal into a physical action (i.e. the dc motor is an actuator). Not quite sure what separates motors from actuators though.
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Offline Steve Joblin

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Re: Servos?Motors?Actuators?Wad exactly are the differences?
« Reply #3 on: January 29, 2007, 08:43:29 AM »
I think that technically Zeol is correct... I was taking it more from the practical aspect in how we refer to things (at least in the US) :)

Offline Somchaya

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Re: Servos?Motors?Actuators?Wad exactly are the differences?
« Reply #4 on: January 29, 2007, 01:26:36 PM »
I think I'd describe motors and servos as different kinds of actuators. Like you could say "the robot has an actuator on its arm" when it really has a servo doing the work.
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Offline Admin

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Re: Servos?Motors?Actuators?Wad exactly are the differences?
« Reply #5 on: January 30, 2007, 06:51:09 PM »
Zeol is right . . .

look at the PID diagram at the top of this page:
http://www.societyofrobots.com/programming_PID.shtml

other things that can be an actuator:
wing on a bird
muscle
heating pad
your legs
steam engine

Offline BADBOY13Topic starter

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Re: Servos?Motors?Actuators?Wad exactly are the differences?
« Reply #6 on: January 30, 2007, 09:37:13 PM »
Thanks for the replies.

No wonder the terms are used inter-changably...

actaully i asked because i went to this exhibition and there was this robot with 3 sockets labelled, power, actuators and motor. That what lead me to ponder what exactly is ther difference.

thanks again.

Offline Joe

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Re: Servos?Motors?Actuators?Wad exactly are the differences?
« Reply #7 on: April 08, 2007, 02:10:19 PM »
A motor is a type of actuator. They usually spin continuously.

Servos usually rotate to a desired position and stop. A servo is a package containing a small motor connected via a gear train (a bunch of gears) to a potentiometer which is connected to the output shaft (the "arm") is read by a control circuit which also reads input pulses and based on these 2 readings controls a motor driver that sends current through the motor which turns the output shaft via the gear train until the potentiometer which is connected to the output shaft reaches a certain position such that its voltage output is that awaited by the control circuit at which point it stops the motor. The output shaft (servo "arm") has now moved to the its desired position.

Servos can be modified to spin contiuosly like bare motors and motors can be combined with encoders and other hardware/software to make them go to positions and stop. Servos are much easier for either function.

In the case of the labels you saw, I would guess "actuators" in that case were linear actuators and "motors" of course were rotational. "Power" could have been a number of things.

 


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