Parallel:
   
    Refers to a data communication format wherein many signal lines are used to communicate more than one piece of data at the same time. May also refer to a motor mounting style on an actuator which brings the motor back parallel with the actuator body versus inline with the actuator body.
   
    Permanent Magnet Motors:
   
    Permanent Magnet Motors are typically not used in industrial applications. PM motors generally have a high step angle, are low torque, low cost and used in high volume consumer applications such as printers, fax machines and toys.
   
    Phase-Locked Servo System:
   
    A hybrid control system in which the output of an optical tachometer is compared to a reference square wave signal to generate a system error signal proportional to both shaft velocity and position errors.
   
   
    Phase Angle:
   
    The angle at which the steady state input signal to a system leads the output signal.
   
    Input Output
   
    Phase Angle
    Phase Margin:
   
    The difference between 180° and the phase angle of a system at its crossover frequency.
   
    Pitch:
   
    An angular deviation possible in positioning systems, in which the tables leading edge rises or falls as the table translates along its direction of travel. This represents rotation around a horizontal axis, perpendicular to the direction of travel.
   
   
    PID?-Proportional-Integral-Derivative:
   
    An acronym that describes the compensation structure that can be used in a closed-loop system.
   
   
    PLC:
   
    Programmable logic controller; a machine controller that activates relays and other I/ O units from a stored program. Additional modules support motion control and other functions.
   
    PMC:
   
    Programmable motion controller, primarily designed for single- or multi-axis motion control with I/O as an auxiliary function.
   
    Pole:
   
    A frequency at which the transfer function of a system goes to infinity.
   
    Point-to-Point Move:
   
    A multi-axis move from one point to another where each axis is controlled independently. (No coordination between axes is required).
   
   
    Position Error:
   
    The difference between the present actuator (feedback) value and the desired position command for a position loop.
   
   
    Position Feedback:
   
    Present actuator position as measured by a position transducer.
   
   
    Power:
   
    The rate at which work is done. In motion control, Power = Torque x Speed.
   
   
    Process Control:
   
    A term used to describe the control of machine or manufacturing processes, especially in continuous production environments.
   
    Pull-In Torque (also called Starting Torque):
   
    This is the maximum torque the stepper motor can develop when instantaneously started at that speed.
   
    Pull-Out Torque (also called Slewing Torque):
   
    This is the maximum torque that the stepper can develop once an acceleration profile has been used to "ramp" it to the target speed.
   
    Pulse Rate:
   
    The frequency of the step pulses applied to a motor driver. The pulse rate multiplied by the resolution of the motor/ drive combination (in steps per revolution) yields the rotational speed in revolutions per second.
   
    PVT:
   
    Position Velocity Time. In PVT mode a controller sends Position, Velocity and Time signals to the drive. The drive follows these commands and uses interpolation algorithms to "connect the dots" and create smooth coordinated motion. This network based command greatly reduces network traffic by allowing the drive to interpolate the intermediate points between the PVT points. PVT can tightly coordinate multiple axes with smooth, precise and exactly timed motion.
   
    PWM:
   
    Pulse Width Modulation. A method of controlling the average current in a motors phase windings by varying the on-time (duty cycle) of transistor switches.
   
    Quadrature Encoder Signal:
   
    Refers to signal characteristics of interfaces to positioning devices such as encoders or resolvers. Specifically, that property of position transducers that allows them to detect direction of motion using the phase relationship of two signal channels. (A type of incremental encoder output in which the two square wave outputs are offset by 90 degrees).
   
   
    Ramping:
   
    The acceleration and deceleration of a motor. May also refer to the change in frequency of the applied step pulse train.
   
    Rated Torque:
   
    The torque producing capacity of a motor at a given sped. This is the maximum torque the motor can deliver to a load and is usually specified with a torque/speed curve.
   
    Recommended Standard 232 (RS-232):
   
    The standard for serial transmission between a DTE (computer) and a DCE (modem, mouse, etc.). This is a single-ended (unbalanced) hardware configuration that employs a method of communicating digital information in which the data bits are transmitted sequentially over one line. The typical transmission speed of an RS-232 connection is 9600 bps over a maximum distance of 50ft (15m).
   
    Recommended Standard 422 (RS-422):
   
    The standard for serial data communication protocol which specifies 4 wire, full duplex, differential line, multi-drop communications. It provides for balanced data transmission with unidirectional/non-reversible, terminated or non-terminated transmission lines. With a transmission rate of 9600 bps, RS-422 can be used at distances up to 4,000 feet (1,275 meters).
   
    Recommended Standard 485 (RS-485):
   
    This standard is an enhanced version of RS-422 with the added capability to allow up to 32 devices (transmitters and receivers) that share the same serial data communication lines. It uses a 2 wire, half duplex, multipoint serial connection.
   
    Regeneration:
   
    Usually refers to a circuit in a drive amplifier that accepts and drains energy produced by a rotating motor either during deceleration or free-wheel shutdown.
   
    Registration Move:
   
    Changing the predefined move profile that is being executed, to a different predefined move profile following receipt of an input or interrupt.
   
    Repeatability:
   
    The degree to which the positioning accuracy for a given move performanced repetitively can be duplicated.
   
    Resolution:
   
    The smallest positioning increment that can be achieved. Frequently defined as the number of steps required for a motors shaft to rotate one complete revolution.
   
    Resolver:
   
    An electromagnetic feedback device which converts angular shaft position into analog signals. These signals can be processed in various ways, such as with an RDC (resolver-to-digital converter) to produce digital position information. There are two basic types of resolvers; transmitter and receiver. A transmitter-type is designed for rotor primary excitation and stator secondary outputs. Position is determined by the ratio of the sine output amplitude to cosine output amplitude. A receiver-type is designed for stator primary excitations and rotor secondary output. Position is determined by the phase shift between the rotor output signal and one of the primary excitation signals.
   
    Resonance:
   
    Designates the condition resulting from energizing a motor at a frequency at or close to the motors natural frequency. Lower resolution, open-loop systems will exhibit large oscillations from minimal input.
   
    RFI:
   
    Radio Frequency Interference
   
   
    Ringing:
   
    Oscillation of a system following a sudden change in state.
   
    Robot:
   
    A reprogrammable multifunctional manipulator designed to move material, parts, tools or specialized devices through variable programmed motions for the performance of a variety of tasks.
   
   
    Robot Control:
   
    A computer-based motion control device to control the servo-axis motion of a robot.
   
   
    Roll:
   
    An angular deviation from ideal straight line motion, in which the positioning table rotates around its axis of travel as it translates along that axis.
   
   
    Root Mean Square Current (RMS Current):
   
    In an intermittent duty cycle application, the RMS current is equal to the value of steady state current which would produce the equivalent resistive heating over a long period of time.
   
   
    Root Mean Square Torque (RMS Torque):
   
    For an intermittent duty cycle application, the RMS torque is equal to the steady state torque which would produce the same amount of motor heating over long periods of time.
   
   
    Rotor:
   
    The rotating part of a magnetic structure. In a motor, the rotor is connected to the motor shaft.
   
   
    RS-232C:
   
    A data communications standard that encodes a string of information on a single line in a time sequential format. The standard specifies the proper voltage and time requirements so that different manufacturers devices are compatible.
   
    Run away:
   
    In control systems, Run Away occurs when feedback is lost or inverted. When there is no feedback the system detects that the velocity is zero or the position is stationary. If the system is trying to reach a velocity or position other than what it is detecting, the system will try to compensate. However with no feedback it will appear to the system that the load is not moving so the system will try to add more power. The end result is a system that is outputting full power that causes the load to spin out of control and possibly crash into something.