An electric motor that responds to controller inputs by modifying its position, speed, or torque is called a servo motor. Servo is derived from the Latin word servus, which means slave or servant. This shows how servo motors have traditionally been used as auxiliary drives to support the primary drive system.
Nonetheless, modern servo motors may function as primary drives in various applications with great performance and accuracy.
In this reading, we’ll explore what a servo motor is, its application, diagram, parts, types, how it works, and how to control it. We’ll also learn its advantages and disadvantages.
Let’s get started!
What Is A Servo Motor?
A servo motor is a type of motor that rotates with high precision. This type of motor typically has a control circuit that provides feedback on the motor shaft’s present location. This feedback enables the servo motors to rotate very precisely.
A servo motor can be used to rotate an object at a certain angle or distance. The only component of it is a basic motor that is driven by a servo mechanism. It is referred to as a DC servo motor if it is powered by a DC power source and an AC servo motor if it is driven by an AC power source.
The servo motor consists of three parts:
- Controlled device
- Output sensor
- Feedback system
The system is a closed loop that employs a positive feedback system to regulate the ultimate position of the shaft and the motion. In this case, a feedback signal produced by comparing the output signal with the reference input signal controls the device.
The feedback mechanism generates the third signal after comparing the reference input signal with the reference output signal. Additionally, the device’s control system uses this third signal as an input signal.
A difference between the reference input and reference output signals or the generation of a feedback signal indicates the presence of this signal. Therefore, the main purpose of a servomechanism is to maintain a system’s output at the intended value in the presence of noise.
Application Of A Servo Motor
In many industries, servo motors are employed for comparable, if not identical, purposes. Some of its applications include:
Robotics
Robotics uses servo motors a lot to control the movement of robot arms, grippers, and leg joints. Robots can carry out tasks like walking, picking up objects, and assembling parts because of their accuracy and responsiveness.
Conveyor Systems
In industries that deal with packaging, food processing, and logistics, servo motors are used in conveyor belts to control speed and position precisely. They make sure that material handling and sorting processes run smoothly.
Toys and DIY Tools
Toys and DIY tools use servo motors for RC cars, planes, and robots. This makes them very popular with hobbyists and students studying mechanics and automation.
Scanners And Printers
Printing machines rely on servo motors to control the height of the printing panel, which applies heat and presses ink onto material. A servo motor controls the movement of the print head or scanning head in a printer or scanner. This fine-grained control ensures crisp, clear printing of all text and graphics. Servo motors contribute to printing output consistency.
CNC Machinery
Servo motors provide incredibly precise control over cutting tools or machine beds in computer numerical control (CNC) machines. This ensures the creation of high-quality components in industries such as automotive, aerospace, and manufacturing.
Medical Devices
Servo motors provide accurate movements and adjustments in medical devices such as imaging systems, prostheses, and surgical robots. For example, they make it possible for robotic arms to carry out delicate surgical procedures.
Home Automation
Smart curtains, remote-controlled gadgets, and automated doors all require servo motors. They improve the functionality of modern houses with their reliability and seamless operation.
Aerospace Engineering
Electronic controllers are necessary for space-related devices; servo motors meet this need by providing an angular controller for motion control and other functions. Flaps, ailerons, and rudders are just a few of the aircraft components that servo motors regulate.
Stable and effective management requires this level of precise control. Aircraft servo motors facilitate the accurate positioning of antennas and solar panels for optimal communication and operation.
Servo Motor Diagram
Related: What is a Blower Motor? Its Diagram and How it Works
Parts Of A Servo Motor
A servo motor is made up of a collection of interconnected parts. These parts include:
Motor Shaft
Similar to a prime mover, it can use that energy to increase the torque of the motor while decreasing its speed when connected to a gearbox or belt and pulley system. Typically, cold- or hot-rolled steel is used to make the motor.
Rotor
Typically, the rotor is positioned between two bearings and fastened to the motor shaft. The servo motor’s rotor is its moving component. The motor’s rotor rotates in the desired direction with the supplied voltage until the error is zero.
Bearings
Bearings can give the motor extremely low vibration and high accuracy. This makes the operation very smooth and cool. New greases and fret reduction techniques will increase bearing life.
Stator
The stator is responsible for producing a rotating magnetic field to generate torque effectively. This component of the servo motor remains in one place. Typically, a single copper wire connects twelve separately wrapped winding segments.
Encoder
An encoder is an electromechanical device that relays a motor’s direction and speed to the drive. This enables the operator to monitor and modify specific parameters as needed.
Brake
Brakes, which are composed of only a few parts, are used to hold objects in place when the machine is turned off or the E-stop is engaged. The motor will fall when the brakes are released, so be careful because the spring will release when voltage is applied.
Snap Ring
A snap ring keeps the shaft in place after an unwanted force hits it directly or nudges it, minimizing damage to the motor. The shaft could simply slide back into the housing without it.
Bearing Keeper
A bearing keeper is a small, portable plate that fits snugly against the pulley end and keeps the bearing from coming loose.
O Ring
An O-ring seals the two parts to prevent fluid from entering. Multiple O-rings can be found in servo motors, which are constructed from plastic polymers.
Housing
The servo motor is protected from outside debris by a coated aluminum housing that is approximately 1 inch (2.54 cm) thick. It is easy and quick to disassemble and reassemble the motor’s housing.
Types Of Servo Motors
There are several types of servo motors, each of which is best suited for a particular application and ensures smooth and reliable operation. The most popular varieties of servo motors are as follows:
AC Servo Motors
Alternating current (AC) powers AC servo motors. They provide smooth performance and are very dependable in applications that need precise control over heavy loads and high speeds. The efficiency and longevity of AC servo motors make them popular in industrial equipment such as robotics, CNC machines, and conveyor belts.
DC Servo Motors
Direct current (DC) powers DC servo motors. Compared to AC servo motors, they are easier to control and have a simpler design. They are frequently used in low-power applications like toys, tiny robotics, and home automation systems because of their quick response and low cost.
Positional Rotation Servo Motors
In terms of controlling angular movements, this type is by far the most common. They are perfect for applications like camera gimbals, antenna positioning, and robotic arms because they rotate to a precise angle in response to input signals.
Continuous Rotation Servo Motors
Continuous rotation servos, as opposed to positional servos, can move freely in either direction without coming to a stop at a predetermined angle. They work wonderfully for making robot wheels and conveyor systems.
Brushed Servo Motors
Brushes are used in brushed servo motors to supply current to the motor via the commutator. This conventional design is widely recognized and has been consistently employed in various applications for many years. These motors are frequently used in smaller industrial equipment, consumer electronics, and automotive applications.
Brushless Servo Motors
An electric motor that operates without brushes and utilizes permanent magnets is known as a brushless servo motor. This design minimizes wear and tear. Compared to brushed motors, it offers greater efficiency, greater speed, and a longer lifespan. They move smoothly and effectively, thanks to electronic commutation control.
Linear Servo Motors
Linear servo motors eliminate the need for mechanical systems such as gears or ball screws by directly converting electrical energy into linear motion. As a result, the motion control system becomes cleaner, more effective, and much more precise.
The linear servo motor is well suited for applications that require rapid movement and precise positioning, including high-speed transport systems, CNC machinery, and assembly robots.
Synchronous Motors
The purpose of a synchronous motor, also known as a synchronous AC servo motor, is to run at a constant speed in sync with the current’s frequency. These motors are incredibly precise since the applied frequency directly determines their speed.
Machines that rely on precise timing, such as synchronous clocks and conveyor systems, benefit greatly from these motors because of the reliability and stability of their speeds.
Asynchronous Motors
The basic idea behind asynchronous motors, often known as induction motors, is that a rotating magnetic field causes a rotor to generate power. This type of motor does not have permanent magnet motors, so it is usually easier to build than synchronous motors.
It is popular in industrial applications requiring speed variance and robustness. Pumps, fans, and conveyor systems are common applications where precise speed control is not as important.
How Does a Servo Motor Work?
A servo consists of a gear system, a potentiometer, a DC or AC motor, and a control circuit. The gear assembly helps lower the motor’s RPM while increasing its torque. Consider a servo motor shaft in its starting position with the potentiometer knob positioned such that the output port of the potentiometer does not generate an electrical signal.
At this point, the error detection amplifier’s second input terminal receives an electrical signal. Now a feedback mechanism will process the difference between the two signals—one from the potentiometer and the other from other sources—and deliver an output in the form of an error signal.
When the motor receives this error signal, it begins to rotate. Now, the potentiometer is attached to the motor shaft; when the motor rotates, the potentiometer will also emit a signal. As the potentiometer’s angular position changes, so does the output feedback signal. After some time, the potentiometer’s position reaches a point where its output matches the external signal.
The motor will stop rotating in this situation since there is no difference between the signal created at the potentiometer and the signal applied externally; hence, there will be no output signal from the amplifier to the motor input.
Controlling The Servo Motor
The servo motor, a DC motor, operates on the principle of PWM (Pulse Width Modulation) and can turn 90 degrees from its neutral position. The motor is controlled by a variable resistor (potentiometer) and some gears, which convert high-speed force into torque.
The potentiometer is connected to the output shaft of the servo to calculate the angle and stop the DC motor at the required angle. The servo can rotate from 0 to 180 degrees but can go up to 210 degrees depending on the manufacturing.
The degree of rotation can be controlled by applying an electrical pulse of proper width to its control pin. The pulse checks every 20 milliseconds, with 1 ms width rotating the servo to 0 degrees, 1.5 ms to 90 degrees (neutral position), and 2 ms to 180 degrees. All servo motors work directly with +5V supply rails, but caution must be taken when using multiple motors.
Advantages of Servo Motors
Servo motors offer several noticeable benefits for a wide range of applications. Some major advantages include the following:
Very Precise
One of the biggest benefits of servo motors is their precision, which makes them invaluable in industries where accuracy is of the utmost importance. Servo motors can attain high levels of precision by utilizing complex feedback systems that continuously adapt for positional accuracy.
Highly Reliable
Servo motors are known for their exceptional reliability, resulting in low downtime and maintenance expenses. These products are reliable because they are well-designed with long-lasting materials and cutting-edge engineering. The feedback mechanism in servo systems constantly analyzes and adjusts the motor’s performance, saving wear and tear and preventing common faults found in less modern motors.
Torque Control
Servo motors also have excellent torque control. Servo motors can precisely manage the amount of torque applied thanks to complex algorithms and feedback systems, which change dynamically to the work needs. Computer numerical control (CNC) machining and robotics are two examples of applications that rely on precise torque control for complex material manipulation.
Closed-loop Control
One of the most important features of servo motors is closed-loop control, which provides very accurate and precise operation. To achieve the required position, speed, or force, this system continuously modifies the motor’s operation based on the input. While open-loop systems, such as those in stepper motors, allow errors to accumulate, closed-loop control ensures excellent accuracy and repeatability.
Disadvantages of Servo Motors
Even with the noticeable benefits one can get from using a servo motor, some limitations still exist.
High Cost
For many people, one of the most significant downsides of servo motors is their high cost. Servo systems, which include motors and the necessary controllers and encoders, are typically pricier than simpler systems such as stepper motors.
For small enterprises or applications where cost is a crucial consideration, this higher initial investment may be a significant barrier to entry. When precision and speed are not critical, more cost-effective solutions may be recommended.
Setup and Maintenance Difficulty
Servo motors require complicated control systems and precise feedback mechanisms, which can make them difficult to set up and maintain.
Regular calibration is required, and specialized knowledge may be required to troubleshoot and repair these systems, which can raise operational costs and downtime. For lesser applications, this level of complexity may be unnecessary, making simpler motor systems more appealing due to their ease of use and maintenance.
Suitability for Specific Applications
While servo motors perform well in applications needing great precision, speed, and torque, they may not be the ideal option in all situations. Other motor types, such as direct drive motors, may provide greater efficiency and reduced operational expenses in applications with persistent high-load needs and minimum speed variation.
Environmentally Sensitive
Servo motors are susceptible to environmental conditions, including dust, vibrations, and heat, which can impair their performance and longevity. This sensitivity necessitates the installation of servo motor systems in well-controlled conditions, potentially raising the cost of infrastructure.
FAQs
What is a servo motor used for?
Servo motors, often known as “servos,” are electronic devices and rotary or linear actuators used to precisely rotate and push machine parts precisely. Servos are most commonly employed for angular or linear position, as well as particular velocity and acceleration.
What is the main function of a servo?
A servo motor is an electric motor that uses electrical power to generate mechanical power. It is often used in dynamic systems where rapid movement is required. To achieve this, the servo motor must have a low inertia or mass while producing a high force or torque for acceleration.
What is the working principle of a servo motor?
A servo motor is an electromechanical device that generates torque and velocity in response to current and voltage inputs. A servo motor is part of a closed-loop system that provides torque and velocity when instructed by a servo controller and closes the loop with a feedback device.
What is another name for a servo motor?
While “servo motor” is the most commonly used term, other names include “servo actuators,” “motion control motors,” and “precision actuators” in various industries. Historically, terminology like “servomechanisms” has emphasized the evolution of these devices and their growing applications.