A motion control system typically includes: a controller that processes motion algorithms and signals; an amplifier that amplifies signals and supplies motion output to actuators; and a feedback (sensor/transmitter) system that adjusts process variables based on a comparison of the output and input values.
The system also includes an operator interface or a front-end device. Feedback means that most motion control systems are closed-loop systems; however, some are open-loop systems, especially stepper motor systems. Actuators come in various forms—electric motors, cylinders, helical coils, etc.—and can be electrical, hydraulic, pneumatic, or other types of devices.
Axis: Any moving part of a machine or system that requires controlled operation. Many motion axes can be combined into a single, equivalent multi-axis system.
Circular interpolation: The coordinated movement of two independent axes of motion produces a circular motion. It is achieved through a software algorithm using a series of approximate straight lines;
Commutation: Continuous excitation of the motor coils maintains a relative phase angle between the rotor and stator magnetic fields, controlling the motor's output within a specified range. In brushed DC motors, this function is accomplished by a mechanical rectifier and carbon brushes; in brushless motors, it is achieved through rotor displacement feedback.
Electronic gears: A method of simulating mechanical transmission electronically, "forcing" one closed-loop shaft to be driven by another shaft (open-loop or closed-loop) in a variable ratio manner.
An encoder is a feedback device that interprets mechanical motion and represents the displacement of an actuator as an electronic signal. Incremental and absolute encoders are commonly used and come in various models; similarly, their outputs represent the increase and absolute change in displacement.
Feedforward: A method that pre-compromises a control loop based on known errors derived from the characteristics of the motor, drive, or load to improve response. It depends solely on the command, not the measurement error.
Indexer: An electronic unit that converts high-level commands from the host, PLC, or operator panel into step and pointing pulse signals required by the stepper motor driver;
Loop bandwidth: The maximum rate at which a control loop can respond to a control parameter variable. It reflects the loop's performance and is expressed in Hz;
Motion specification: The ratio of velocity to time (or displacement) of motion, generated by the motion axis;
Overshoot: A system's response output or result exceeds its rated value;
Pulse Width Modulation (PWM): A switching control method used in amplifiers and drivers to control the voltage and current of a motor, achieving higher efficiency than linear control. PWM refers to the variable duty cycle or width of a voltage pulse.
Orthogonal: A technique that separates signal channels at 90° intervals in a feedback device. Encoders and decoders use this technique to determine the direction of motion;
Solver: A displacement transducer that uses electromagnetic coupling to measure absolute axial displacement during rotation;
Servo device: An automated closed-loop motion control system that uses feedback to control rated outputs such as displacement, velocity, or acceleration;
Tachogenerator: An electromagnetic feedback converter that provides an analog voltage signal proportional to the rotational speed.
