Servo motors are used in robotic applications that require
precise positioning. Before immersing yourself too much in the way servos are
used in robotics, it is useful to first learn the basic functions and forms of
the key components of motion control.
What is Servo?
The servo, the most basic element, is a way to convert the
rotational movement with precision and power linear movement. The servo (or
sometimes known as a servomotor)
consists of:
1. Electronic set consisting of an AC or DC electric motor,
controller board and potentiometer.
2. Case, which is a plastic housing for engines and other
components.
3. The drive gear
reduces the high-speed motor output to a slower and higher torque servo output.
4. The output spline is attached to the output axis and is
the end point of interaction between the servo and the object of movement it is
creating. A good example is the servo of a remote controlled airplane. The
servo outlet slot can be connected to a control surface, such as a spoiler or
rudder, through a control bar. Therefore, the movement of the servo will cause
an equal movement of the plane itself.
How Does A Servo
Work?
1. Servo receives a signal from the motion controller.
2. The servo rotates a certain amount according to the pulse
width modulation (PWM) of the input signal. In steady state, the servo output
spline is typically 0 ° Based on the expected pulse rate of 20 milliseconds
(ms), a pulse width of 1.5 ms rotates the output spline 90 ° in one direction.
If the pulse width is 2 ms, the output spline will continue to rotate 90 ° more
to the 180 ° position. A pulse width of 1 ms rotates the output spline 180 °
again to the initial position of 0 °.
3. The potentiometer constantly monitors the position of the
output spline. When the output slot reaches the desired position, the servo
will remain in that position until the engine is turned off and no signal is
received. While standing in a certain position, the servomotor attempts to
actively maintain that position.
4. The main feature of the servo is the proportional
operation. The servomotor operates only as necessary to rotate from the current
position to the desired position. If the servo stops in the 180 ° position but
needs to be in the 0 ° position, the motor will turn and reach very fast. If it
stops at a position already close to 0 °, the motor will turn much slower and
get there.
How Are Servos Useful
In Robotics?
Servo motors offer many advantages in robotic applications.
Small, powerful, easy to program and precise. But most importantly, it allows
almost perfect movement repeat-ability. Used in robotic applications such as:
1.Robotic welding: The servomotors are mounted on all the
joints of the robotic welding arms to activate the movement and add dexterity.
2.Robotic vehicles: The servos are used in steering systems
in autonomous vehicles used for the release and disposal of pumps.
