Our blog on “Servo Motor Terminologies”! Servo motors offer precise control and efficiency across industries and applications. To work with these powerful devices, understanding their terminology is crucial.
In this blog, we will cover key terms related to servo motors. Topics covered include angular position, speed, commutation, and Bode plots. Whether a beginner or an experienced professional, this blog is your comprehensive guide to servo motors. Enhance your knowledge and navigate the world of servo motors. Let’s dive in and unravel the complexities of servo motor terminologies together!
A
Amplifier:
An amplifier is an electronic device that boosts the control signal to provide enough power for driving the servo motor. It takes the low-power input signal and increases its voltage or current to a level that can control the motor’s movement.
Angular Acceleration:
Angular acceleration refers to how the angular velocity of a servo motor changes over time. It measures the speed rate. Indicates the motor’s ability to speed up or decelerate.
Angular Position:
Angular position refers to the angular displacement of the servo motor’s output shaft from a reference point or position. It indicates the exact angle at which the shaft is positioned, allowing for precise control of the motor’s orientation.
Angular Speed:
Angular speed refers to the rate at which the servo motor rotates, measured by the change in angular position per unit of time. It represents how fast the motor is spinning and is crucial for controlling the motor’s rotational speed.
Armature:
The armature is the rotating part of a servo motor that interacts with the magnetic field to generate torque and rotation. It consists of a coil of wire wound around a core. Current flows through the coil. It produces a magnetic field that interacts with the field magnet. Motor movement occurs as a result.
B
Backlash:
Backlash is a kind of slack or plays in a mechanical system. In motors, it refers to any gap in response when changing the direction of motion.
Bandwidth:
In servo systems, bandwidth refers to the range of frequencies the system can follow. Higher bandwidth means a quicker response to changes.
Basic Type:
The basic type refers to the core design or fundamental classification of a servo motor. Examples include whether a motor is AC or DC, or brushed or brushless.
Bode Plot:
A Bode plot is a graph displaying the frequency response of a system. It shows the size and phase of a system’s frequency response, helping in analysis and design.
Brush:
In motors, a brush is a device that connects stationary and rotating parts. It enables the transfer of electrical current within the motor.
Brushless Motor:
A brushless motor, as the name implies, doesn’t use brushes for electrical current transfer. Instead, it relies on electronic control for commutation.
C
Closed Loop System:
A closed-loop system uses feedback to control its operation. It compares the output with a desired value and adjusts the input.
Communication Type:
This refers to the method used to send and receive data between a servo motor and its controller. Common types include serial and parallel communication.
Commutation:
Commutation in motors is the process of switching the electrical current direction in the windings. In brushless motors, this process is done.
Commutator:
A commutator is a device in brushed motors that reverses the current direction in the windings. It helps to maintain torque in one direction.
Continuous Stall Torque:
This is the largest torque that a motor can produce without movement and without overheating. It’s a key rating for servo motor performance.
Continuous Torque:
Continuous torque is the motor’s greatest torque. It should not exceed the temperature rating. It’s essential for the motor’s continuous operation.
Control Loop:
A control loop is a system of controlling a process. It uses feedback to adjust the system’s input to achieve the desired output. It’s the heart of a servo system.
D
Deadband:
Deadband refers to a range of input signals that don’t cause a system to respond. In servo motors, it’s often the zone where small signal changes don’t lead to movement.
Duty Cycle:
A duty cycle is the fraction of one period in which a signal is active. In motors, it often refers to the ratio of ‘on’ time to the total period of a PWM signal.
E
Encoder:
An encoder is a sensor attached to a servo motor’s shaft, providing feedback on the shaft’s position or speed. Encoders are vital in a servo system for precision control. They come in different types, like incremental encoders or absolute encoders, each serving specific needs in motor control.
F
Feedback Signal:
This is the crucial information a servo system receives about its actual state. In a servo motor, this could be the motor’s position, speed, or torque. The feedback signal is used to make necessary adjustments to reach the desired state.
Field Magnet:
In a servo motor, the field magnet creates a magnetic field that interacts with the armature to generate motion. It’s a permanent magnet in brushless motors or an electromagnet in brushed motors.
Flux:
Flux in a servo motor refers to the magnetic field produced by the field magnet. The strength and direction of this magnetic field (flux) influence the motor’s torque and speed.
Frame Size:
This term relates to the physical dimensions of a servo motor. Frame size is an important factor to consider in the motor selection process, as it can impact torque production and fit within a system.
Frame Symbol:
A frame symbol is a notation used to identify specific characteristics of a servo motor, like frame size or motor configuration. It can vary between different motor manufacturers but generally helps users identify the right motor for their needs.
G
Gain:
Gain is a vital concept in control systems like those in servo motors. It’s a measure of how responsive or sensitive the system is to changes in input. In the context of a servo motor, the gain can influence how the motor reacts to a command. For instance, a high gain might cause the motor to react and overshoot its target, while a low gain might lead to slower reactions. Tuning the gain is essential for achieving precise and stable control.
H
Hall Effect Sensor:
A Hall Effect sensor is a transducer that varies its output voltage in response to changes in a magnetic field. In brushless DC servo motors, these sensors are used to sense rotor position and aid in commutation, enabling efficient motor operation.
Holding Torque:
Holding torque is the largest load torque a servo motor can withstand without moving, while powered on. It’s important in applications that need the motor to hold a position, as it affects the motor’s ability to resist changes in its position.
Homing:
Homing is a process where the servo motor is moved to a known position at startup. This ‘home’ position serves as a reference point for future movements. It’s crucial in applications where precise positioning is required.
Hysteresis:
In servo systems, hysteresis exists. It is the difference between input signals. Signals start movement in one direction and the opposite direction. It’s a type of error that can affect the precision of the system.
I
Induction:
In servo motors, induction occurs. It induces an electric current in motor coils. It changes the magnetic field. This principle converts electrical energy to mechanical energy. Motor movement results.
Inertia:
Inertia represents an object’s resistance to changes in motion. In a servo motor system, the inertia of the motor and its load should be matched for optimal performance. Too much difference can lead to overshoots, oscillation, and poor control performance.
Insulation Class:
Insulation class refers to the thermal tolerance of the motor’s insulation materials. It’s often designated by letters (like A, B, F, or H), with each class able to tolerate a specific largest temperature. Choosing a servo motor with the right insulation class is crucial, as exceeding the temperature limit can damage the motor.
L
Load:
Omit servo motors, the load refers to the force or resistance against which the motor has to work. It can be static (like lifting a weight) or dynamic (like driving a conveyor belt). Understanding load characteristics is crucial for servo motor selection. It affects speed, torque, and performance. For instance, a motor that’s too small might not move the load, while one that’s too large might waste energy and add unnecessary cost.
M
Max. Current:
This refers to the greatest electrical current that the servo motor can draw under any operating condition. Exceeding this value can cause overheating and potential damage to the motor. Thus, understanding a motor’s max current can help prevent motor failure.
Max. Rotational Speed:
This is the largest speed at which the servo motor can rotate. It’s usually measured in revolutions per minute (RPM). This parameter is crucial when selecting a motor for a specific application as it impacts the system’s speed capability.
Moment of Inertia:
Moment of Inertia is a measure of an object’s resistance to changes in its rotational motion. For servo motors, load characteristics often refer to load inertia. Matching motor inertia ensures optimal performance. Responsiveness is improved.
Momentary Max. Peak Torque:
This is the highest amount of torque that a servo motor can produce in short, burst periods without causing damage. It’s often used during rapid acceleration or deceleration in the motor’s operation.
Motor Constant:
The motor constant is a value that links the motor’s electrical characteristics to its mechanical properties. It’s often used to compare motors’ efficiencies, as a higher motor constant usually indicates a more efficient motor.
Multifunction Type:
Multifunction refers to servo motors with many functions or tasks. They incorporate more features and capabilities. For example, they may include built-in encoders for precise control and feedback.
N
No Load Current:
This refers to the amount of electrical current that a servo motor draws when it’s running without any load attached, at its rated voltage. This value is essential as it can help to diagnose issues with the motor or the drive. A high no-load current might state a problem, such as a short circuit or a bearing issue.
No Load Speed:
This is the largest speed at which a servo motor can rotate when there’s no load, other than its own inertia. It’s an important parameter to consider in applications where speed is a critical factor. Keep in mind that the actual operating speed under load will be lower than the no-load speed due to the motor’s torque characteristics.
O
Open Loop System:
This is a type of control system where the output isn’t fed back into the input for correction. In an open-loop system, the servo motor operates on its output. This makes these systems simpler and cheaper but less accurate, as they don’t correct for errors.
Overload Capacity:
This refers to the largest amount of load that a servo motor can handle for a short period without damage or loss of performance. It’s expressed as a percentage of the motor’s rated capacity. Knowing a motor’s overload capacity helps ensure that it can withstand brief surges in demand.
Overshoot:
This term describes a situation where a servo motor exceeds its target position before settling back. It often occurs due to system instability or high gain. Minimizing overshoot is crucial for applications where precision is required, as it can lead to errors in positioning.
P
Peak Torque:
This is the largest torque that a servo motor can produce, usually for a brief period. It’s often used during rapid acceleration or deceleration. Understanding peak torque aids in designing systems. It handles high-demand situations. Prevents motor damage.
Phase:
In the context of motors, phase refers to the number of electrical circuits used to produce magnetic fields for operation. The three-phase motor uses three electric currents. It ensures smoother operation and higher power density.
Pole:
A pole in a servo motor refers to a region of the motor where a North or South magnetic field is created. The number of poles a motor has affects its speed and torque characteristics, with more poles leading to higher torque and lower speed.
Pole Pairs:
This term refers to a pair of north and south magnetic poles in a motor. The number of pole pairs is significant. It influences motor speed. The motor rotates once per pair of poles in each electrical cycle.
Positioning Error:
This is the difference between a servo motor’s actual position and its target position. Minimizing positioning errors is crucial in precision tasks. Feedback systems correct errors in real time.
R
Rated Current:
This is the largest level of current a servo motor can operate for an extended time without overheating. It’s a key specification to consider when sizing a motor for a specific task to avoid damaging the motor and ensure optimal performance.
Rated Current (A(rms)):
The rated current (A(rms)) is another way to express the rated current, but using root mean square (rms) Amps. This is particularly used in alternating current (AC) systems. The rms value of a currency is its effective value, indicating the equal direct current (DC) which would deliver the same amount of energy.
Rated Output:
Rated output is the largest continuous mechanical power a servo motor delivers. It avoids overheating risks. Measured in watts or horsepower. Determines motor suitability for specific applications or loads.
Rated Rotational Speed:
Rated rotational speed or speed is the largest safe operating speed. It prevents overheating in the servo motor. The specification in RPM is crucial. Matches motor to speed requirements. Essential for specific applications.
Rated Speed:
Rated speed is another term for rated rotational speed. It indicates the highest safe speed. Motorists avoid damage from excessive heat generation.
Rated Torque:
Rated torque refers to the largest amount of torque that a servo motor can produce on a continuous basis without overheating. Measured in Nm or ft-lb, torque is crucial in servo motor selection. It matches the motor to the load or application.
Regenerative Brake Frequency:
Regenerative brake frequency refers to how often regenerative braking occurs. Regenerative braking converts the motor’s kinetic energy. It turns into electrical energy during deceleration. It acts as a brake. This frequency can depend on the application and controller settings.
Resolver:
A resolver is a type of rotary electrical transformer used for measuring degrees of rotation. It’s used in servo motors to provide precise position and speed feedback, critical for the motor’s control system.
Rise Time:
In control systems, the rise time is the time taken for output change. It goes from a low value to a high value. It spans 10% to 90% of the total. It’s an important measure of how a servo motor responds to changes.
Rotor:
The rotor is the rotating part of a motor, which spins when a current is applied. In a servo motor, the rotor is the output part that drives the load. Its design affects the motor’s speed, torque, and efficiency.
S
S-curve Acceleration:
S-curve acceleration is a motion profile strategy used in servo systems to increase and decrease speed, mimicking the shape of an ‘S’. Smoother motion achieved. Reduced jerk, less stress on the mechanical system. Contrasts with abrupt starts and stops.
Servo Controller:
A servo controller is the brain of a servo system. Takes command signals. Compares with motor feedback. Adjusts output for desired position, velocity, or torque.
Servo Drive/Amplifier: A
A servo drive amplifies low-power command signals. It converts them into high-power current or voltage. The purpose is to drive the motor. It is also called a servo amplifier. It’s responsible for translating the controller’s instructions into precise movements.
Servo Gearbox:
A servo gearbox is a mechanical device attached to the output shaft of a servo motor. It increases the motor’s torque while decreasing its speed. This process gives a servo system better control, precision, and efficiency in delivering power to a load.
Servo Motor:
A servo motor is a rotary actuator. It can also be a linear motor. It enables precise control. Control includes angular or linear position, velocity, and acceleration. It comprises a motor, a sensor for position feedback, and a control circuit.
Servomechanism:
A servomechanism is an automated system. It uses error-sensing feedback. The purpose is to correct performance. It consists of a servo motor. It also includes a feedback sensor. A controller is part of it too. They all work together. The goal is to align the output with the commanded value.
Settling Time:
Settling time refers to a specific time. It is the time a servo motor takes. The goal is to reach a predefined error band. This happens after receiving a step input. The motor needs to stay within that error band. It is a critical metric in systems requiring fast and accurate positioning, like robotics and automation.
Slew Rate:
The slew rate is the largest rate at which the output of a system can change. In a servo motor, it’s the fastest speed the motor can adjust to a change in the input signal. The higher the slew rate, the faster the motor can respond to changes.
Speed Control Range:
This term refers to the range within which the speed of a servo motor can be controlled. It’s usually expressed as a ratio, such as 1:1000, where the motor can maintain its performance from its largest speed down to 1/1000th of that speed.
Stalling:
Stalling in a servo motor occurs when the load applied to the motor exceeds its largest torque, causing it to stop rotating. This can harm the motor, especially if power continues to be applied during the stall.
Starting Torque:
Starting torque, also known as breakaway torque, is the amount of torque that a servo motor produces at the instant it starts moving. Settling time is often higher. It exceeds the motor’s running torque. It becomes crucial in certain situations. The motor needs to overcome initial resistance. It also needs to overcome inertia from a standstill.
Stator:
The stator is the stationary part of the motor that contains the windings. Current passes through the windings. This creates a magnetic field. The magnetic field interacts with the rotor’s field. As a result, the rotor spins. The spinning rotor generates mechanical power.
Step Response:
Step response refers to a system’s output resulting from a sudden change or “step” in the input. In servo systems, the step response could state how and the motor responds to a sudden change in position command.
Stepper Motor:
A stepper motor is a type of motor that moves in distinct steps. Each step is triggered by an electrical pulse. This enables precise control of rotation. Stepper motors are popular for tasks requiring accurate positioning.
Synchronous Speed:
Synchronous speed is the speed at which the magnetic field of an AC motor rotates. It’s determined by the frequency of the power supply and the number of poles in the motor. In synchronous motors, the rotor rotates at this speed.
T
Time Constant:
The time constant is a key indicator of a system’s response speed. In the context of motors, it’s the time taken for a motor to reach approximately 63% of its final speed, torque, or current, from an initial state. A shorter time constant signifies a faster-responding system.
Torque:
Torque, in the context of motors, refers to the rotational force a motor produces to turn an object. It’s crucial to know the torque a servo motor can provide, as it impacts the load the motor can handle. High torque is necessary for tasks that must a significant amount of force.
Torque Constant:
The torque constant of a motor describes how much torque it produces per unit of current. It’s a critical parameter in motor selection as it relates the motor’s electrical input to its mechanical output. Higher torque constant means the motor will produce more torque for the same current.
Torque Ripple:
Torque ripple refers to the fluctuation or variation in torque output as a motor rotates. It can cause vibration and noise in servo motor applications. Minimizing torque ripple is crucial for smooth operation and precision in motor control.
Trapezoidal Acceleration:
Trapezoidal acceleration is a method. It accelerates a motor. It then maintains a constant speed. Finally, it decelerates. This creates a trapezoid-like profile. It’s ideal for applications where smooth start and stop transitions are necessary to prevent damage to the connected load.
V
Voltage Constant:
The voltage constant, often denoted as Kv, links the motor’s speed to the applied voltage. It specifies how many RPM (rotations per minute) the motor will achieve per volt applied, without any load. This constant is crucial in understanding motor speed control and efficiency. It’s usually provided by the manufacturer in the motor’s datasheet.
W
Winding:
In the context of a motor, a winding refers to the coils of wire wrapped around the motor’s core, within the stator. These windings create magnetic fields when electricity passes through them. The interaction between the magnetic fields and the current in the windings generates the force needed to spin the motor’s rotor. Winding configurations impact motor performance. It affects torque and speed characteristics.
Conclusion
In conclusion, we have covered a wide range of servo motor terminologies in this blog. Terms are crucial for understanding servo motors. They explain principles, functionality, and operation. Basic concepts (angular position, speed) contribute to understanding servo motors and drives. Intricate topics (commutation, Bode plots) enhance understanding as well.
Familiarizing with these terms improves communication, troubleshooting, and optimization of servo motor applications. Engineer, technician, or enthusiast, grasp of servo motor terminologies empowers control. Informed decisions are made. We hope this blog has provided valuable insights and enhanced your knowledge of servo motor terminologies. Keep exploring and harnessing the power of servo motors in your endeavors!