MOTION SYSTEMS HANDBOOK
Controllers for motion control and beyond The main task of any motion controller is to command the motion of some machine or system, including any motors and other mechanical components such as actuators. Whether control is needed for simple point-to-point positioning or for multi-axis interpolated moves, choosing the right motion controller can have lasting effects on the final designed system. For instance, a controller with insufficient computing power or capabilities that fails to meet a machine’s motion control needs can degrade the machine’s performance and abilities. On the other hand, overly powerful or robust controllers can add unnecessary system cost. More specifically, motion controllers calculate and generate the commands for the motor or actuator to move. These are known as motion trajectories and involve calculating the right speed and position. These commands can be sent to a drive which develops the necessary current to drive the motor. In a closed-loop system, there will also be some type of feedback from the process that helps to adjust the commands in order to meet system requirements. Controllers can use a number of algorithms needed to generate commands including control loops, interpolators and step generators. Choosing the right motion controller can be challenging because they range in complexity and capability — from simple indexing to full-fledged motion control systems. But knowing as much as possible about the immediate application and of the range of controllers on offer can vastly simplify the task.
CATEGORIZING CONTROLLERS Controllers can be categorized in a number of different ways depending on what is prioritized. For instance, they can be divided
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DESIGN WORLD — MOTION
8 • 2020
The iQ-R Series from Mitsubishi Electric is a fully integrated controller designed to support a host of manufacturing applications. It integrates motion, safety, process, redundant, and other control disciplines on a single platform, interfaces with enterprise and visualization systems, and conforms with global standards such as IEC 61131-3 programming languages. by the physical format (plug-in board, stand-alone, embedded,) or by function (PLC, PAC, motion controller) or even by architecture (distributed or centralized.) If we focus first on size, we can start from the smallest motion controllers; embedded controllers. These are so-called because the control is literally embedded into the device or system being controlled. Most often these are circuit-board-sized controllers with a main processor on board, memory, and control circuitry. They also motioncontroltips.com | designworldonline.com
