Servo Motor Control

In the simplest case, you want to maintain some performance level. Think for a minute about driving a car down a straight road where the speed limit is 100 km/hr and there are lots of police to give you a ticket if you speed.

So, perhaps once a second you look at the speedometer. If you're over 100 km/hr, you reduce the gas pedal. If you're under 100 km/hr, you increase the gas pedal. That's called feedback (the comparison) and your foot is the control signal.

Or, you can read this link

http://www.compumotor.com/whitepages/ServoFundamentals.pdf

In Radar applications, this is the motor that turns the antenna and at the same time sends a signal to a second motor that keeps the beam on the scope turning at the same speed and same direction. In this special case there's a "master motor" and a "slave motor" where the "master" dictates to the "slave" how fast or slow it has to turn, and the slave controls the related systems. just one application of many thousands... but the trick is always the same. today, many of the mechanical motors have been replaced by digital circuitry. Faster quieter no moving parts and much more reliable.

Wangito.

Few references are well given . Thanks .

"I really want to know How a servo motor can be controlled?What is the practical function of a servo controller?"

You need to learn about control theory. There are many excellent texts available. Here is one of the best:

Amazon.com: Modern Control Engineering (4th Edition): Katsuhiko OGATA (List $147.00, sale $130.58 - so, go to a library - a large well stocked technical library.)

If you can not obtain an Introductory Control Theory textbook, here is a web site that has relevant information:

http://www.educypedia.be/electronics/motorservo.htm

The best thing to do is to take a course in control theory, while designing and building simple servo motor systems yourself. You can buy small DC servo motor control systems from Hobby Shops that deal in radio control airplanes, boats, and cars.

The function of a servo controller is to control a servo motor, either AC or DC. The servo controller receives an electrical input (generally based upon the error between the desired motor output and the actual motor output). The controller then produces its own electrical output to drive the servo motor to the desired final state. In the DC case, the servo motor controller can consist of a simple operational amplifier, wired up to produce the error signal, followed by a power amplifier to drive the DC motor. Electrical transducers are required to sense or generate a DC voltage proportional to the actual motor output, and the desired motor output. And most often, the DC motor's output is not the desired output, but rather the position of some other component driven by the motor is the desired output. An example of this is Automobile Power Steering, driven by a DC servomotor. Honda's NSX system consists of a rack-and-pinion steering gear with a DC electric motor (Servo Motor) installed concentrically around the rack. The motor transmits its power through a recirculating ball drive mechanism to push the rack right or left.

These days, stepper motors with digital controllers have replaced many if not most AC and DC servo motors and servo controllers. Just about every ink jet printer contains stepper motors, and digital stepper motor controllers.

Think of a water tank that will be filled to a certain level with water.

Level is "0" at the bottom and "100" at the top of tank.

There must be a "motorised valve" supplying water to the tank.

There must be a "level gauge / transmitter" measuring where the level is (feedback).

There must be a "servo-controller" supplying output to the motorized valve.

Initially u must "set" the controller for the required level of water anywhere between "0" and "100".

Servo controller informed by level transmitter about where the water level is.

Motorized valve commanded (open or close) by the servo controller to fix the level to the "set level".

Now think of this example together with the one that's given by TVP45:

The motorized valve acts like your foot.

The level transmitter acts like speed dial (and your eyes).

And the servo controller acts like your brain.