If she were a simple motor in a robot arm and you were the microprocessor, you would have to spend some of your time watching what she did and giving her commands to move her back to the right spot (this is called a feedback loop). But if she went out farther than you can throw, you would have to call out "closer" until she got back to the right spot.
You could keep calling out "farther, farther, farther" until she got as far away as you wanted. You stand at one end and want your friend to go out for a long throw. Imagine you are playing catch with a friend on a sports field. Did you notice how few parts are on the circuit board? Servos have evolved to a very efficient design over many years. The circuit board and DC motor in a high-power servo. It then compares the desired position to the actual position and decides which direction to rotate the shaft so it gets to the desired position.įigure 5. The electronics on the circuit board decode the signals to determine how far the user wants the servo to rotate. The electronic input signal from the computer or the radio in a remote-controlled vehicle also feeds into that circuit board. The sensor tells this circuit board how far the servo output shaft has rotated. A positional sensor on the final gear is connected to a small circuit board (see Figure 5 below). Unlike a simple DC motor, however, a servo's spinning motor shaft is slowed way down with gears. With a small DC motor, you apply power from a battery, and the motor spins. Better quality is more expensive, and high-output servos can cost two or three times as much as standard ones. The motor is usually more powerful than in a low-cost servo and the overall output torque can be as much as 20 times higher than a cheaper plastic one. In a high-power servo, the plastic gears are replaced by metal ones for strength. 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.įigure 4. Gears in an inexpensive servo motor are generally made of plastic to keep it lighter and less costly (see Figure 3 below). The amount of actual work is the same, just more useful. The gear design inside the servo case converts the output to a much slower rotation speed but with more torque (big force, little distance). (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). An arrangement of gears takes the high speed of the motor and slows it down while at the same time increasing the torque. Work- you apply torque when you open a jar). 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 The heart of a servo is a small direct current (DC) motor, similar to what you might find in an inexpensive toy. The simplicity of a servo is among the features that make them so reliable.
quarter and is intended for applications where smallness is a critical factor but a lot of power is not. The miniature servo is about the size of a U.S. The standard servo on the left can range in power or speed to move something quickly, or it can accommodate a heavier load, such as steering a big radio-controlled monster truck or lifting the blade on a radio-controlled earthmover toy. Commercial aircraft use servos and a related hydraulic technology to push and pull just about everything in the plane.įigure 2. The car's computer calculates that information and other data from other sensors and sends a signal to the servo attached to the throttle to adjust the engine speed. In 21st-century automobiles, servos manage the car's speed: The gas pedal, similar to the volume control on a radio, sends an electrical signal that tells the car's computer how far down it is pressed. Electronic devices such as DVD and Blu-ray Disc TM players use servos to extend or retract the disc trays. Servos also appear behind the scenes in devices we use every day. By rotating a shaft connected to the engine throttle, a servo regulates the speed of a fuel-powered car or aircraft. In a model car or aircraft, servos move levers back and forth to control steering or adjust wing surfaces. If you have a radio-controlled model car, airplane, or helicopter, you are using at least a few servos. Servos are found in many places: from toys to home electronics to cars and airplanes. Servo motors (or servos) are self-contained electric devices (see Figure 1 below) that rotate or push parts of a machine with great precision.
0 kommentar(er)
