Motion Controllers
Programmable Logic Controllers ( PLCS ) & Programmable Logic Controller
Robots having closed-loop systems are controlled by programmable logic controllers ( PLCS ) through digital-to-analog (d/a) I/O modules. These modules convert digital PC signals to analog outputs having ±10-V range. The outputs serve as speed references for the hydraulic or electrical servosystems that typically power each axis. Each axis is mechanically coupled to a potentiometer or encoder that feeds position and velocity data back to a programmable logic controller ( PLCS ), closing a feedback control loop. Digital commands from a programmable logic controller ( PLCS ) to a converter initiates motion, sets acceleration rates, determines speeds, and initiates deceleration. Motion is halted when the feedback indicates the robot has reached the proper position.
Suitably equipped programmable logic controllers ( PLCS ) can generally control point-to-point or vectored motion. Point-to-point movement along each axis is initiated and halted independently of other axes. This type of motion is easily programmed, requires little memory, and is suitable for many robot applications.
Vectored motion, however, requires that the movements along two or more axes be interdependent. The programmable logic controller ( PLCS ) adjusts acceleration rates and speed for each axis so that all movement terminates simultaneously. By this means a robot arm moves from point to point along the shortest path. Vectored motion control usually reduces the time required for each move. To perform vectored control, programmable logic controllers ( PLCS ) must be equipped with arithmetic firmware that calculates speeds required for each axis. Although standardized algorithms are used for these calculations, vectored motion programs are somewhat more complex and require more memory than those for point-to-point motion.
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Programmable Logic Controller & Programmable Logic Controllers ( PLCS ): AC Linear Motion Controller Information
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