Glossary for Motion Control
Glossary for Motion Control defines the terminology behind the controllers, drives, and software that command precision movement in industrial automation. As the Glossary for Motion Control covers both hardware and software, it provides clarity on many complex concepts. It spans single-axis control, including point-to-point moves, homing, and limit switches. In addition, it covers multi-axis control, such as interpolation, coordinated motion, and kinematic transformation. It also discusses synchronous control, including electronic gearing, electronic camming, and flying shear synchronization. Moreover, there is coverage of the supporting hardware that operators and engineers interact with — HMI panels, PLCs, and SCADA systems. This thorough Glossary for Motion Control also covers the communication protocols that tie everything together. Examples are EtherCAT, PROFINET, and CANopen. It also explains core performance terms like following error, settling time, and encoder resolution. In summary, the Glossary for Motion Control is a valuable resource for anyone dealing with automation terminology. Moreover, using a Glossary for Motion Control ensures consistent understanding among professionals in the field.
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Category Term Definition Motion Control Fundamentals Motion Controller The hardware or software unit that calculates and issues position, velocity, and acceleration commands to one or more axis drives, acting as the brain of an automated motion system. Drive (Servo Drive) The power electronics unit that takes commands from a motion controller and converts them into the precise current and voltage needed to move a servo or stepper motor. Axis A single controllable direction of motion within a machine, such as one linear stage or one rotary joint, each typically requiring its own drive and feedback loop. Closed-Loop Control A control method in which a feedback device, such as an encoder, continuously reports actual position back to the controller, allowing it to correct for any deviation from the commanded path. Open-Loop Control A control method, typical of basic stepper motor systems, in which the controller issues commands without receiving position feedback, assuming the motor follows each command exactly. Motion Profile The planned curve of position, velocity, and acceleration over time that a controller commands an axis to follow during a move, often shaped to minimize vibration and settling time. PID Loop A feedback control algorithm using proportional, integral, and derivative terms to continuously adjust drive output and minimize the error between commanded and actual axis position. Feed Rate The commanded speed at which an axis or tool moves along a programmed path, a key parameter in both point-to-point and continuous-path motion control. Single-Axis Motion Control Single-Axis Motion Control A control architecture in which one controller and drive manage the motion of a single independent axis, without coordinating movement with any other axis. Point-to-Point Motion A single-axis motion mode in which the controller moves the axis directly from a current position to a target position, without controlling the path taken between the two points. Homing A routine in which a single axis moves to a known reference position, such as a limit switch or index pulse, to establish an accurate zero point after power-up. Limit Switch A sensor mounted at the physical end of an axis's travel range that signals the controller to stop motion, preventing mechanical overtravel and damage. Jog Mode A manual motion mode that moves a single axis at a fixed or operator-controlled speed for as long as a control input is held, commonly used for setup and maintenance. Standalone Drive A servo or stepper drive that includes its own onboard motion controller, capable of executing simple single-axis moves without an external motion controller. Multi-Axis Motion Control Multi-Axis Motion Control A control architecture in which a single controller coordinates the motion of two or more axes simultaneously, enabling complex paths such as straight lines, arcs, or contours across multiple directions. Interpolation The mathematical process by which a multi-axis controller calculates intermediate position commands for each axis so that their combined motion traces a smooth linear, circular, or contoured path. Coordinated Motion A multi-axis control mode in which multiple axes move together along a defined geometric path, as opposed to each axis completing its own independent point-to-point move. Cartesian Coordinate Motion A multi-axis motion mode that commands position in X, Y, and Z linear axes, commonly used for gantry systems, 3-axis robots, and XYZ pick-and-place platforms. Kinematic Transformation The calculation a multi-axis controller performs to convert a desired tool-tip position in space into the corresponding individual joint or axis commands needed to reach it. Path Blending A multi-axis control feature that smooths the transition between consecutive programmed move segments, avoiding a full stop at each corner to maintain continuous velocity. Master-Slave Axis Configuration A multi-axis control arrangement in which one axis, the master, generates a motion reference that one or more slave axes follow at a defined ratio or offset. Synchronous Motion Control Synchronous Motion Control A control mode in which two or more axes move in precise, real-time coordination with one another, maintaining a fixed relationship in position, speed, or timing throughout the motion. Electronic Gearing A synchronous control function in which a slave axis follows a master axis at a programmable ratio, replicating the behavior of a mechanical gearbox without physical gears. Electronic Camming A synchronous control function in which a slave axis follows a master axis according to a programmable position-versus-position curve, replacing a mechanical cam profile with software. Flying Shear Synchronization A synchronous motion application in which a cutting axis matches the speed of a continuously moving material before executing a cut, avoiding the need to stop the line. Registration Control A synchronous motion technique that adjusts axis timing in real time based on a sensor-detected mark or feature, keeping a process synchronized to material that has positional variation. Cyclic Synchronous Position (CSP) Mode A drive operating mode, common in EtherCAT-based systems, in which the controller sends a new position target to the drive on every communication cycle for tightly synchronized multi-axis motion. Latency The time delay between a controller issuing a command and a drive executing it, a critical factor in how tightly synchronized motion control performance can be. HMI Devices HMI (Human-Machine Interface) A display device, typically touchscreen, that allows operators to monitor machine status, adjust parameters, and issue commands to a motion control system without programming directly into the controller. Operator Panel A simplified HMI device, often with physical buttons or a small display, used for basic machine control functions such as start, stop, and mode selection. Touchscreen HMI An HMI device using a touch-sensitive display to present graphical controls, status screens, and alarms, replacing physical buttons with software-defined interface elements. SCADA (Supervisory Control and Data Acquisition) A higher-level software system that aggregates data and HMI functions from multiple machines or controllers across a facility, used for plant-wide monitoring beyond a single HMI panel. Alarm Management An HMI function that displays, logs, and prioritizes fault and warning conditions reported by the motion controller, helping operators diagnose issues quickly. Recipe Management An HMI function that stores and recalls predefined sets of motion parameters, allowing an operator to quickly reconfigure a machine for a different product or process. PLC PLC (Programmable Logic Controller) An industrial control computer that executes sequential logic, I/O handling, and safety interlocks, often working alongside or within a motion controller to manage the overall machine sequence. Ladder Logic A graphical PLC programming language that represents control logic as a series of rungs resembling an electrical relay ladder diagram, widely used for its readability by electricians and technicians. I/O Module (Input/Output Module) A PLC hardware component that reads signals from sensors and switches, or sends signals to actuators and indicators, forming the physical interface between the PLC and the machine. Scan Cycle The repeating sequence in which a PLC reads inputs, executes its logic program, and updates outputs, with scan time directly affecting how quickly the system can respond to changes. Motion-Integrated PLC A PLC that includes built-in motion control function blocks, allowing a single controller to handle both sequential logic and axis motion without a separate dedicated motion controller. Safety PLC A PLC certified to a defined safety integrity level, used to manage safety-related functions such as emergency stops and guard interlocks independently from standard machine logic. Communication Modes Fieldbus A category of industrial digital communication networks that connect controllers, drives, sensors, and I/O devices, replacing point-to-point analog wiring with a shared data link. EtherCAT A high-speed, deterministic industrial Ethernet protocol that allows a motion controller to exchange data with many drives and I/O devices within a single, very short communication cycle. PROFINET An industrial Ethernet communication protocol, widely used in automation, that supports both standard data exchange and motion-specific real-time performance modes. CANopen A fieldbus communication protocol built on the CAN physical layer, commonly used for lower-speed device networks including some motor drives and sensor systems. Modbus A widely supported, simple serial or Ethernet communication protocol often used to connect PLCs, HMIs, and drives where high-speed motion synchronization is not required. Determinism A communication network property describing whether data arrives within a fixed, predictable time window, essential for synchronous multi-axis motion control performance. Cycle Time (Communication) The fixed time interval at which a fieldbus network exchanges data between the controller and connected drives, directly limiting the achievable synchronization performance of the system. Performance & Specification Terms Following Error The instantaneous difference between a commanded position and the actual measured position of an axis during motion, monitored by the controller to detect performance or fault conditions. Settling Time The time an axis takes to come to rest within a specified position tolerance after reaching its commanded target, important in high-throughput positioning applications. Bandwidth (Servo Loop) A measure of how quickly a servo drive's control loop can respond to changes in commanded position or load disturbance, expressed in Hertz. Axis Count The total number of independently controllable motion axes a controller or drive system can manage, a key specification when scaling from single-axis to multi-axis applications. Encoder Resolution The number of distinct position values an encoder can report per revolution or per unit of linear travel, directly affecting the achievable positioning accuracy of the controlled axis. 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