So What Are Servo Motors And How Do Servo Motors Work?
Servo is a motor that is attached to a position feedback device
. Generally there is a circuit that allows the motor to be commanded to go to a specified "position". A very common use of servos is in Radio Controlled models.
R/C Servos come in standard "sizes" (so that they fit models well) and use similar control schemes. Unlike general purpose motors, R/C servos are constrained from full rotation. Instead they have a limited rotation of about 180 degrees or less.
A typical R/C looks like a rectangular box with a motor shaft coming out of one end and a connector with three wires out of the other end. Attached to the motor shaft is usually (but not always) a "control horn". This is a plastic piece with holes in it for attaching push rods or other mechanical linkages to the servo. The three wires are V+, Control, and Ground. R/C servos typically run on 4.8v (four NiCd batteries) but they often work with voltages between 4 and 6 volts. The control line is used to position the servo. In an R/C model, this line it attached to the radio receiver, on robots it is usually attached to the processor.
These servos are "active" devices, meaning that when commanded to move they will actively hold their position. Thus, if a servo is commanded to the neutral position and an external force is present to push against the servo (presumably through the mechanical linkage) the servo will actively resist being moved out of that position. The maximum amount of force the servo can exert is the torque rating of the servo.
Another parameter that varies from servo to servo is the slew rate. This is the time it takes for the servo to change from one position to another. The worst case slewing time is when the servo is holding at the minimum rotation and it is commanded to go to maximum rotation. This can take several seconds on very high torque servos. Typically it takes less than two seconds.
For expert advice and guidance about R/C servos and large industrial Servo Motors such as Brushless, Torque and hollow shat DC, talk to the people that know. Servo Motors U.K is the worlds leading distributer of Servo Motors