Glossary

AC stands for Alternating Current which periodically reverses direction, in contrast to direct current (DC) that flows only in one direction. AC is the typical power source that comes 'out of the wall'. Single phase and three AC phases are standard.

AC Line Filter is a filter that connects to the incoming AC on a machine. Intended to keep the electrical noise produced in the machine from polluting the AC in the building.

AC Servo is a general term referring to a motor drive that generates sinusoidal shaped motor currents.

Acceleration is the rate at which something increases its velocity. Acceleration is usually measured in units of velocity change for each unit of time (inches/ second (velocity)/second (time)) and in this example would be written as in./sec/sec or in./sec2.

Accuracy is the relative status of something compared to its absolute or perfect value. In motion control this will most often be a position description. A command may be sent to move 4.0”. The accuracy of the system will be defined by how close to the absolute value of 4.0” the system can affect the move. Accuracy may be defined as a one-time incident or the average over a number of cycles or motions. Positioning accuracy will normally be defined in terms of deviation (+/- from theoretical) or limits (acceptable variation from theoretical: ie. 3.8”-4.2” define acceptable limits of variation around a theoretical point of 4.0”)

Active Front End is a front end processor which interacts with both upstream and downstream equipment and makes required changes based on the incoming and outgoing parameters and data, without external control.

Actual Position is the position of an axis relative to the commanded position. This may be the position at the end of the commanded move or the lag between command position at any point during the move and the actual position of the axis at that point. The latter is commonly referred to as Following Error.

For servo systems, Actuator is a device (such as a motor) that outputs mechanical motion using electricity as the power source.

Alarm is an indication that a monitored parameter is not within the prescribed acceptable range. Usually this is in the form of an output that can be used to initiate an operator warning or advisory, to generate a corrective action, or to cause a cessation of the operation underway.

The temperature of the cooling medium, usually air, immediately surrounding the motor or another device.

Ampere is the basic unit of electric current. In short “Amp” or “Amps”.

A servo system that utilizes analog control and feedback systems such as voltage variation, pressure changes etc. Analog servos are most commonly found in hydraulic and similar systems.

Analog signal is a communication within the system that is accomplished by means of a signal that varies in direct relation to the intensity or magnitude of the external quality being measured. Typical examples are a 0-10 volt motor control signal, a hydraulic pilot pressure, a pneumatic control pressure.

Angular accuracy is the measure of shaft positioning accuracy on a servo or stepping motor.

The specific major directions along which controlled movement occurs. Usually the number of these major directions employed in a specific machine and defined as follows: ● X: Linear motion in positioning direction ●Y: Linear motion perpendicular to positioning direction ●Z: Vertical linear motion ●A: Angular motion around X (roll) ●B: Angular motion around Y (pitch) ●C: Angular motion around Z (yaw)

Axis is a principal direction along which movement of a tool, component or workpiece occurs.

Back EMF is the voltage generated when a permanent magnet motor is rotated. This voltage is proportional to motor speed and is present regardless of whether the motor winding(s) are energized or de-energized.

Breakaway torque is the torque required to start a machine in motion. Almost always greater than the running torque.

Brushed motor is a servo motor in which the commutation of the current is accomplished by the use of mechanical brushes rather than through electronic commutation. The brushes remain in contact with the commutator, therefore current is constantly flowing to the armature coils. The main advantages of a brushed motor are high starting torque and low cost, these features make them common in industrial environments.

A Brushless motor is a servo motor in which the commutation of the current is accomplished electronically rather than through the use of mechanical brushes and a commutator. In a brushless motor, the windings are on the stator and the magnetic field is provided by permanent magnets in the armature. This results in higher motor efficiency,  increased heat dissipation, longer lifespan, and quieter operation.

Bus is one or more conductors used as a path over which information is sent from one of many sources to one of many destinations.

CANopen is a communication protocol and device profile specification for embedded systems used in automation.

Centralized control is a control system in which all of the primary processing is done at a single location rather than at multiple points throughout the system.

Circular interpolation is the generation of an apparently circular motion through the coordinated movements of two axes. The actual path is a series of straight line approximations generated by software algorithms.

Closed Loop is a broadly applied term, relating to any system in which the output is measured and compared to the input. The output is then adjusted to reach the desired condition. In motion control, the term typically describes a system utilizing a velocity and/or position transducer to generate correction signals in relation to desired parameters.

Clogging is a term used to describe non-uniform angular velocity. Cogging appears as a jerkiness, especially at low speeds.

Collision detection is the use of sensors to detect the imminent impact of two or more parts in a system. The signals from the detection sensors can be used to stop motion or to provide a ramped slow down for a “soft” mating of the approaching components.

Commutation is a term which refers to the action of steering currents or voltages to the proper motor phases so as to produce optimum motor torque. In brush type motors, commutation is done electromechanically via the brushes and commutator. In brushless motors, commutation is done by the switching electronics using rotor position information obtained by Hall sensors, a tachometer, or resolver.

Controller is a term describing a functional block containing an amplifier, power supplies, and possibly position-control electronics for operating a servo motor or step motor.

Converter is the process of changing AC to DC and back to AC again. This is accomplished through the use of a diode rectifier or thyristor rectifier circuit. The term "converter" may also refer to the process in an adjustable frequency drive, consisting of a rectifier, a DC intermediate circuit, an inverter and a control unit.

Coordination is the integration of the movements of two or more axes of motion so that the resultant motion is a path which none of the axes are capable of independently. Coordination may also involve the use of sensors and other internal or external commands in the integration effort which assist in effecting the movement or work desired.

Current at Peak Torque is the amount of input current required to develop "peak torque". This is often outside the linear torque/current relationship.

Current controller is a  system that utilizes an electronic method of limiting the maximum current available to a motor. This current is adjustable so that the motor’s maximum current can be controlled and normally includes functions that serve as a protective measure to prevent extended overload conditions from damaging the motor or the controller.

Current - rated is the maximum allowable continuous current a motor can handle without exceeding motor temperature limits.

Cut to length is a sub-routine within a motion control processor or stand-alone processor that is designed to feed material being processed a pre-set distance prior to performance of a secondary function such as a cut off. Feedback systems are employed to ensure repeatability of the set feed length.

DC bus is a type of circuit or protocol that serves as a common communications pathway shared by several components and which uses a direct current voltage level as a reference. It may also be used to describe a power distribution system shared by multiple components within a machine or power distribution system.

Deceleration is the rate at which something decreases its velocity. Deceleration is usually measured in units of velocity change for each unit of time (Inches/ second (velocity)/ second (time)) and in this example would be written as in./sec/sec or in./sec2.

Decentralized control is a control system in which the logic functions and input/output functions are located at individual pieces of equipment or sub systems and function essentially independent of each other. Normally the independent systems will have some means of communicating vital information with each other.

Detent torque is the maximum torque that can be applied to an un-energized step motor without causing continuous rotating motion.

Deterministic scan time is the frequency with which a Programmable Logic Controller (PLC) executes a program, including scanning all the inputs and outputs on the system. This time is usually measured in milliseconds. PLCs will normally read or “scan” the instructions in the logic program in set, sequential manner. The time required to read a specific instruction and all of the following instructions, returning to the initial instruction is generally referred to as scan time.

Device level network is a means of putting sensors, actuators and other components on a common network cable that is connected to a PLC. It eliminates point -to-point wiring between the PLC and each device.

Diagnostic code is a code (usually alpha numeric or numeric) that is displayed on some type of operator interface or within a program that indicates the status of a monitored component. Usually diagnostic codes are used to indicate the location and nature of a fault or error condition that requires rectification.

Digital motion control is a motion control system that utilizes binary coding for all logic and control functions. Analog inputs can normally be used on a digital system, but they must be converted through an analog to digital converter before being processed.

Digital servo is a servo motor (see AC servo and Analog servo) which utilizes binary coding for all parameter generation and feedback.

Digital signal is a signal that communicates information in electrical pulses that represent binary 1s and 0s. It is widely believed that digital signals can transmit more information more reliably in a given unit of time than analog signals.

Drive is an electronic device that translates a given command from a motion controller into the electrical current that turns a motor.

For a repetitive cycle, Duty Cycle is the ratio of on time to total cycle time. Duty cycle (o) = [On time / (On time + Off time)] x 100o

Dynamic braking is a passive technique for stopping a permanent magnet brush or brushless motor. The motor windings are shorted together through a resistor which results in motor braking with an exponential decrease in speed.

A stop function which has all of the following requirements: ●It shall override all other functions and operations in all modes. ●Power to machine actuators that can cause a hazardous condition (s) shall be removed as quickly as possible without creating other hazards (e.g., by the provision of mechanical means of stopping requiring no external power, by reverse current braking for a Category 1 stop). ●Reset shall not initiate a restart. ●The emergency stop shall function as either a Category 0 or Category 1 stop. The choice of category of emergency stop shall be determined in accordance with the requirements of the application. ●Where a Category 0 stop is used for the emergency stop function, it shall have only hardwired electromechanical components. In addition, its operation shall not depend on electronic logic (hardware or software) or the transmission of commands over a communication network or link. ●Where a Category 1 stop is used for the emergency stop function, final removal of power to the machine actuators shall be ensured and shall be by means of electromechanical components.

The ratio of power output to power input.

A technique used to perform non-linear motion electronically similar to that achieved with mechanical cams.

The process of generating a slave profile based on master position or time periods by enabling and disabling electronic cam or gearing functions.

A method that simulates mechanical gears by electrically synchronizing one closed loop axis to a second axis (open- or closed-loop) through a variable ratio.

A virtual axis that is used as the master axis on a machine to which other axes are synchronized by electronic gearing or camming profiles.

A standard set by the European Directive, regulating the testing of electrical devices in order to check their ability of adhering to conducted/ radiated emissions.

A feedback device that translates mechanical motion into electrical signals indicative of actuator position. Incremental and absolute encoders are common varieties; as the names imply, their output indicates incremental or absolute changes of position.

The number of electrically identified positions occurring in 360 degrees of input shaft rotation.

An interface that has become a standard for serial data transfer covering position and parameters.

EtherCAT is a highly flexible Ethernet network protocol that is developing at a rapid rate and growing at an even faster clip. A unique principle called “processing on the fly” gives EtherCAT a handful of unique advantages.

An open networking standard, Ethernet is widely used in office automation and is increasingly being used for packaging machine networks. Originally developed for communications speed of 1.5 megabits/sec, newer versions permit speeds up to l00 megabits/sec.

A change-of-state of an input parameter, such as the triggering of a limit switch or proximity sensor.

The error received when a drive or control has attempted an illegal process and becomes disabled.

A signal which is transferred from the output back to the input for use in a closed loop system.

A method that "pre-compensates" a control loop for known errors due to motor, drive, or load characteristics to improve response. It depends only on the command, not the measured error.

A light wave system that utilizes a glass or plastic fiber guide to transmit light to a control source where the optic intensity is linearly translated into current or is used to determine the open/close state of a current path.

A process control network used for interconnecting sensors, actuators, and control devices to one another, as defined by ISA standard S50.02.

The ability of a drive to restart a spinning motor. This is normally done by sampling the motor speed, encoder input, or back EMF to restart the motor from the speed at which it is coasting.

The ability of a motion controller to swap virtual encoders instantly making advanced synchronizing features possible.

The difference between the commanded position of an axis and its actual position. The amount of Following Error present varies with the speed of the axis. The amount of following error allowed can be adjusted through the KV parameter.

The ratio of RMS current to average current. This number is a measure of the current ripple in a SCR or other switch-mode type of drive. Since motor heating is a function of RMS current while motor torque is a function of average current, a form factor greater than 1.00 means some fraction of motor current is producing heat but not torque.

Refers to a motion system which can operate in all four quadrants; i.e., velocity in both directions and torque in either direction. This means that the motor can accelerate, run and decelerate in either direction.

A motor format which consists of only the stator and rotor provided such that a manufacturer can directly incorporate it into the framework of his machine and eliminate the need for couplings, shafts, or mechanical transmissions.

A resistance to motion caused by contact with a surface. Friction can be constant with varying speed (Coulomb friction) or proportional to speed (viscous friction).

A software used for programming machining processes. Typical applications include 3-axis milling and 2-axis wire cutting.

An overhead framework that is designed to travel linearly in the X, Y, and/or Z axes. Tooling or other devices are generally designed into the framework to perform various functions as it moves from one location to another.

A feedback device which is used in a brushless servo system to provide information for the amplifier to electronically commutate the motor. The device uses a magnetized wheel and Hall Effect sensors to generate the commutation signals.

Refers to the ability of a controller to respond to an event immediately, without delay. While PLCs are inherently designed for this, PCs can be trickier. To be a hard, real-time controller, a PC-based controller's software must be considered the highest priority task, and made independent of the rest of the PCs task.

A switch that is operated by some part or motion of a power-driven machine or equipment to alter the electric circuit associated with the machine or equipment.

A positive-action mechanical friction device. Normal configuration is such that when the power is removed, the brake is set.

Sometimes called static torque, holding torque specifies the maximum external torque that can be applied to a stopped, energized motor without causing the rotor to rotate. Generally used as a figure of merit when comparing motors.

A reference position for all absolute positioning movements. Usually defined by a home limit switch and/or encoder marker. Normally set at power-up and retained as long as control system is operational.

Locating a unique reference position at power-up for axis calibration.

A Unit of measure of Power. One horsepower is equal to 746 watts. The measurement of Rotary power must take speed and torque into account. Horsepower is a measure of a motor's torque and speed capability. Formula:         HP = Torque (lb-in.) x Speed (RPM)/63,025 HP = Torque (lb-ft.) x Speed (RPM)/5,252 HP = Volts x

A host is a computer that is connected to a network. The term usually refers to a computer that is connected to a TCP/IP network, including the Internet. Each host on such a network has a unique IP address.

The console at which an operator or mechanic interacts with the controller of a packaging machine or line. An HMI, or MMI (man-machine interface) or OI (operator interface), often is a computer display with a PC or industrial computer built into or connected to run specialized HMI software.

Used in power section of servo drives to invert the PWM signal to the servo motor.

The range of position increments in which the axis is considered by the controller to be at the commanded position point. Can be thought of in terms of +/- N position increments from the commanded position.

An electronic unit that converts high-level commands from a host computer, PLC, or operator panel into step and direction pulses needed by a stepping motor driver.

An axis or axes in the process of moving to a pre-programmed position, at a defined velocity and acceleration/deceleration rate.

The electrical equivalent to mechanical inertia; that is, the property of a circuit, which has a tendency to resist current flow when no current is flowing, and when current is flowing has a tendency to maintain that current flow.

The property of an object to resist change in velocity unless acted upon by an outside force. Higher inertia objects require larger torques to accelerate and decelerate. Inertia is dependent upon the mass and shape of the object.

For most efficient operation, the system coupling ratio should be selected so that the reflected inertia of the load is equal to the rotor inertia of the motor.

A coordinated move of two or more axes in a linear and/or circular motion.

A drive that converts an AC power source to DC, then back to a variable frequency AC power source for a 3 phase induction motor.

Limits the rate of acceleration change during the movement of an axis. Its purpose is to eliminate mechanical jerking when speed changes are made.

In a master/slave configuration, it refers to the slave drive matching the speed of the master at an acceleration/deceleration rate that provides to a smooth transition.

An axis running at a fixed velocity and acceleration/deceleration rate, in a selected direction, with no specific destination.

Velocity Loop Proportional Gain. Determines how much velocity error will be allowed by the servo system during a move. See also: Tuning

Position Loop Gain. Determines how much positioning error or following error, will be allowed by the servo system during a move. See also: Tuning

The linear units for programming and configuring an axis, typically used in indexing, setting offsets, defining over travel limits etc. Length units are often defined in inches, feet, meters or millimeters.

A relationship between an input and output in which the output is in direct proportion to the input.

An electric induction motor that produces straight-line motion (as opposed to rotary motion) by means of a linear stator and rotor placed in parallel. It has been used to drive streetcars and monorails, where one part of the motor is on the underside of the vehicle and the other is in the track.

The time interval between updates to calculate the process variable from the following error.

In a rotary axis, the position increment at which the axis position returns to 0, i.e. 360 degrees.

Motion control is a sub-field of automation, in which the position or velocity of machines are controlled using some type of device such as a hydraulic pump, linear actuator, or electric motor, generally a servo.

A motion controller controls the motion of some object. Frequently motion controllers are implemented using digital computers, but motion controllers can also be implemented with only analog components.

Two or more axes of motion which must be coordinated. The term "multi-axis synchronization" refers to the motion which requires coordination, and the techniques used to achieve control of the motion.

Navi is a good aviator and navigator. A very strong and big budgie, almost English

An unwanted electrical signal. Typically from RFI or EMI induced onto the drive’s components, speed reference or feedback wiring, and can cause the axis to react unexpectedly. Sources of noise are AC power lines, motors, generators, transformers, fluorescent lights, CRT displays and radio transmitters.

A preset distance between the actual zero reference point and a programmed zero reference point.

Hardware and/or software designed in a way to provide interchangeability of components and connectivity from multiple vendors and suppliers.

Open loop control refers to a motion control system with no external sensors to provide position or velocity correction signals. A closed loop control is a motion control system that has position and velocity feedback to generate a correction signal by comparing its position and velocity to desired parameters. Feedback devices are typically encoders, resolvers, LVTDs and/or tachometers.

A system in which there is no feedback. Motor motion is expected to faithfully follow the input command. Stepping motor systems are an example of open-loop control.

A warning or alarm generated by a motor or drive that indicates the device is too heated. This is generally caused by the demand for excessive current through the device. There may be binding at the motor, calling for more torque, or the motor or drive may be undersized.

Any current in excess of the rated current of the drive to maintain or move to a new position at a given velocity and acceleration or deceleration rate.

The ability of a drive to withstand currents above its continuous rating. וt is defined by NEMA as 150o of the rated full-load current for "standard industrial DC motors" for one minute.

To force an axis to move during a faulted condition. Often required to get an axis to move off of an overtravel limit switch.

A system response where the output or result exceeds the desired value.

The maximum torque a brushless motor can deliver for short periods of time. Operating permanent magnet motors above the maximum torque value can cause demagnetization of the rare-earth magnets. This is an irreversible effect that will alter the motor characteristics and degrade performance.

Adjusting the position of one axis with respect to others during synchronization or electronic line shafting.

Programmable Logic Controller is a type of computer that provides hard, real-time control of packaging and other equipment thanks to fast, repeatable deterministic scan times.

A Programmable Limit Switch is a dedicated, high-speed control that converts the rotary motion of a shaft into digital signals. PLS's are typically used to increase the accuracy of material or product positioning or registration.

A method of wiring each component on a packaging machine directly to the PLC. Hard-wiring eliminates the potential for communication delays found on a network.

Refers to the number of magnetic poles arranged on the rotor of the brushless motor. Unlike an AC motor, the number of poles has no direct relationship to the base speed of the motor.

Error caused when the difference between the actual position, and the command position is greater than a pre-set amount.

Portion of the command signals that generates the position information based on position feedback.

Specifying a move by giving a target position, velocity and an acceleration. The target position can be an absolute position, or a relative position from the current position.

The rate at which work is done. וn motion control, power is equal to the voltage multiplied by current. Power= voltage x current. Power (watts) = force x distance/time.

Ratio of true power (kW) to apparent power (kVA).

A power supply unit (PSU) converts mains AC to low-voltage regulated DC power for the internal components of a computer. Modern personal computers universally use a switched-mode power supply.

Feature that captures the position of a passing mark on the product and then compares this position with the expected position based on current speed. It then compensates for the difference.

Graphical representation of movement. This can be position vs. time, velocity vs. time or torque vs. time.

See PLS

Interface that allows the user to control the motion system according to the demands of the user.

A particular method of encoding either analog or digital information for transmission over a cable. Often used interchangeably with Standard.

The frequency of the step pulses applied to a step motor driver. The pulse rate, multiplied by the resolution of the motor/driver combination (in steps per revolution), yields the rotational speed in revolutions per second.

A switch-mode control method used in amplifiers and drivers to control motor voltage and current to obtain higher efficiency than linear control. PWM refers to variable on/off times (or width) of the voltage pulses applied to the transistors.

A technique that separates signal channels by 90' (electrical) in feedback devices. It is used with encoders and resolvers to detect direction of motion.

Mathematical model that provides a square wave, triangular wave or sinusoidal wave output.

The maximum speed at which the servo motor can rotate.

Physical feedback which provides position information for a synchronized axis to follow.

Device that transforms AC power into DC for use by converter drives.

Procedure to set the feedback device relative to the real world.

Power generated by a motor/drive system during the deceleration phase of movement. In some systems, this regen power can be used by other axis or put back on the network.

The action during motor braking, in which the motor acts as a generator and takes kinetic energy from the load, converts it to electrical energy and returns it to the amplifier.

The degree to which a parameter such as position or velocity can be duplicated.

The smallest increment into which a parameter can be broken down. For example: a 1000 line encoder has a resolution of 1/1000 of a revolution.

A position transducer that uses magnetic coupling to measure absolute shaft position during one revolution. The resolver is a form of feedback.

Oscillatory behavior caused by mechanical or electromechanical harmonics and limitations.

Oscillation of a system following a sudden change in state.

וn an intermittent duty cycle application, the RMS current is equal to the value of steady state current which would produce the equivalent motor heating over a period of time.

RMS Torque - Root Mean Square Torque

Function that calculates speed of a rotary axis to keep the linear speed of the feed material constant as the diameter of the rotary axis changes

Moving in a circular way, using degrees to indicate position instead of mm, or inches in a linear axis

The moving part of the motor, consisting of the shaft and magnets. These magnets are analogous to the field winding of a brush-type DC motor.

S curve refers to a control pattern that accelerates and decelerates a motor slowly to reduce mechanical shock. This function is more sophisticated than linear acceleration, but does not have the performance of camming.

Procedure that turns off the power delivered to the motor.

Refers to software and hardware that (1) permits the control or management of an entire packaging line and (2) automatically collects data on that line' s efficiency.

A series of steps to be executed that then causes an action in a machine.

Serial Real-time Communications Standard. An open communications protocol (adopted as IEC 1491) designed especially for motion-control networks. Defines a method for transmitting digital information over a fiber-optic cable at speeds of 2, and more recently, 4 megabits/sec.

Transmitting digital 1s and 0s in a series over a single cable, the primary method of communication used in and between packaging equipment. Parallel communications use several wires to simultaneously transmit groups of 1s and 0s.

A powered mechanism producing motion or forces at a higher level of energy than the input level, e.g., in the brakes and steering of large motor vehicles, especially where feedback is employed to make the control automatic.

A servo drive is a special electronic amplifier used to power electric servomechanisms. A servo drive monitors the feedback signal from the servomechanism and continually adjusts for deviation from expected behavior.

An automatic, closed-loop motion control system that uses feedback to control a desired output such as position, velocity, or acceleration.

A motor that together with its resolver or encoder is capable of being precisely controlled. A resolver or encoder provides constant and highly accurate feedback on the motor's exact position, speed and torque to the drive that powers it.

The time required for a parameter to stop oscillating or ringing aroundits final value and stabilize on it.

A cable that has a metallic sleeve wrapped around all of the conductors that comprise its center. The metal sleeve is then grounded to eliminate the effects of electrical noise on the signals being carried by the cable.

An encoder that outputs both digital and high resolution analog signals used in servo control in packaging machines.

A software function that turns physical outputs on and off, depending on the level of a specified input. Servomotors, resolvers or encoders usually offer the input for software limit switches.

Acronym for Serial Synchronous Interface. This is a type of multi-turn absolute encoder. The position information is sent from the encoder to the device reading the encoder as a serial string in Gray code format.

The amount of torque developed with voltage applied and shaft locked, or not rotating. Also known as locked-rotor torque.

The non-moving part of the motor. Specifically, it is the iron core with the wire winding in it that is pressed into the frame shell. The winding pattern determines the voltage constant of the motor.

The ability to resist movement induced by an applied torque. Stiffness is often specified as a torque displacement curve, indicating the amount a motor shaft will rotate upon application of a known external force when stopped.

The condition that occurs when several functions of a machine (mechanical, servo or software) follow a common control signal and are in a specific position according to this signal.

An electromagnetic feedback transducer providing an analog voltage signal proportional to rotational speed.

A software system control that determines the execution rates and priority levels for software modules running in a motion control or PLC.

Transmission Control Protocol/Internet Protocol. A method of encoding data into a series of "packets" for transmission over a network. Designed initially for use on the Internet, TCP/IP is rapidly penetrating non-Internet uses, including the factory floor.

The position of an axis that is “taught” into the motion control program. The axis is moved, typically by jogging, to the desired position. This “ teach position” is then entered into the motion program automatically by the control (using whatever steps are required by the motion control manufacturer) and becomes the new Programmed position. The motion control used must have the ability to do this type of program manipulation.

Communication data packet between controller and device.

Velocity Loop Integral Action Time. Associated with KP. When velocity error occurs outside of the tolerance value set in KP, TN determines how quickly the servo drive will bring the velocity back within the specified tolerance. See also: Tuning

A measure of angular force which produces rotational motion. This force is defned by a linear force multiplied by a radius; e.g. lb-in.  Formula: Torque (lb-ft.) = 5,250 x HP/RPM

An expression of the relationship between input current and output torque. For each ampere of current, a fixed amount of torque is produced. NOTE: Torque constants ARE NOT linear over the operating range of a motor. They apply best at -75o of no load maximum speed or where the peak and continuous torque curves meet.

A servo function that allows the monitoring and limiting of the current supplied to a servo motor.

Defined as the motor's holding torque divided by the inertia of its rotor. The higher the ratio, the higher a motor's maximum acceleration capability will be.

Adjusting the servo drive’s internal characteristics to give it the ability to control the reflected inertia and gives the axis a smooth position/velocity profile. The process of Tuning involves setting the Velocity Loop Proportional Gain (KP), Position Loop Gain (KV), and the Velocity Loop Integral Action Time (TN) values so that the axis has a position/velocity profile allowing only as much position/ velocity error as the process will permit.

Twisted pair

The speed at which a motor or mechanical system runs.

A servo control function that sums a velocity command signal with a speed feedback signal from a servo motor, and outputs the difference as a torque command signal.

An encoder signal created in the software of a motion control to allow synchronizing multiple servo systems. A typical machine may have several virtual master encoders.

VxWorks is a real-time operating systems that guarantees an absolutely deterministic response. It is increasingly used in motion control because of its real-time behavior, stability, operating time, and memory efficiency. (Dev. by Wind River Systems)

The error condition received from a drive or a controller that a problem if not remedied within a specified period will result in a fault. The controller or drive is generally not disabled until a fault condition occurs.

The point at which a servomotor’s encoder position and the machines physical position line up. If these two points don’t agree, the servo axis must be “homed.”