HF-103T Mitsubishi Industial AC Servo motor without Encoder 1KW 3AC 125V 5.3A 3000r/min

HF-103T Mitsubishi Industial AC Servo motor without Encoder 1KW 3AC 125V 5.3A 3000r/min

Introduction of Industrial Servo Motors

Types of servo motors

Servos come in many sizes and in three basic types: positional rotation, continuous rotation, and linear.

• Positional rotation servo: This is the most common type of servo motor. The output shaft rotates in about half of a circle, or 180 degrees. It has physical stops placed in the gear mechanism to prevent turning beyond these limits to protect the rotational sensor. These common servos are found in radio-controlled cars and water- and aircraft, toys, robots, and many other applications.
• Continuous rotation servo: This is quite similar to the common positional rotation servo motor, except it can turn in either direction indefinitely. The control signal, rather than setting the static position of the servo, is interpreted as the direction and speed of rotation. The range of possible commands causes the servo to rotate clockwise or counterclockwise as desired, at varying speed, depending on the command signal. You might use a servo of this type on a radar dish if you mounted one on a robot. Or you could use one as a drive motor on a mobile robot.
• Linear servo: This is also like the positional rotation servo motor described above, but with additional gears (usually a rack and pinion mechanism) to change the output from circular to back-and-forth. These servos are not easy to find, but you can sometimes find them at hobby stores where they are used as actuators in larger model airplanes.

How does a servo motor work?

The simplicity of a servo is among the features that make them so reliable. The heart of a servo is a small direct current (DC) motor, similar to what you might find in an inexpensive toy. These motors run on electricity from a battery and spin at high RPM (rotations per minute) but put out very low torque (a twisting force used to do work— you apply torque when you open a jar). An arrangement of gears takes the high speed of the motor and slows it down while at the same time increasing the torque. (Basic law of physics: work = force x distance.) A tiny electric motor does not have much torque, but it can spin really fast (small force, big distance). The gear design inside the servo case converts the output to a much slower rotation speed but with more torque (big force, little distance). The amount of actual work is the same, just more useful. Gears in an inexpensive servo motor are generally made of plastic to keep it lighter and less costly (see Figure 3 below). On a servo designed to provide more torque for heavier work, the gears are made of metal (see Figure 4 below) and are harder to damage.

Selecting a servo motor

When starting a project that uses servos, look at your application requirements. How fast must the servo rotate from one position to another? How hard will it have to push or pull? Do I need a positional rotation, continuous rotation, or linear servo? How much overshoot is allowable? The less you pay for the servo, the less mechanical power it will have to muster and the less precision it will have in its movements. You can pay a bit more and get one that moves quickly, but it may not have a lot of power. You can also buy one that will pull or push large loads, but it may not move quickly or precisely. Manufacturers' websites and online hobby guides will have a lot of this information you can use to compare models. You will also find that hobby stores have a selection of servos and can usually help you decide which one is right for your project and budget.

Controlling a servo motor

Servos take commands from a series of pulses sent from the computer or radio. A pulse is a transition from low voltage to high voltage which stays high for a short time, and then returns to low. In battery devices such as servos, "low" is considered to be ground or 0 volts and "high" is the battery voltage. Servos tend to work in a range of 4.5 to 6 volts, so they are extremely hobbyist computer-friendly.

Have you ever picked up one end of a rope that was tied to a tree or held one end of a jump rope while a friend held the other? Imagine that, while holding your end of the rope, you moved your arm up and down. The rope would make a big hump that would travel from your end to the other. What you have done is applied a pulse, and it traveled down the rope as a wave. As you raise your hand up and down, if you keep your hand in the air longer, someone watching this experiment from the side would see that the pulse in the rope would be longer or wider. If you bring your hand down sooner, the pulse is shorter or more narrow. This is the pulse width. If you keep your end going up and down, making a whole bunch of these pulses one after another, you have created a pulse train (see Figure 6 below). How often did you raise and lower your end? This is the frequency of your pulse train and is measured in pulses per second, or Hz (abbreviation of "hertz").