Sunday, June 12, 2011

Understanding Motion Control Drives

Motion control is a term that describes a range of applications that involve movement in specific routes designed to precision performance. Earlier motion control applications require only an object to be moved from one place to another without paying too much heed to speed or change of motion. On the other hand, there are machine tool applications which require the exact coordination of all aspects of motion, including a high degree of synchronization for multiple simultaneous movements.

Motion control drives finds heavy usage in the robotics industry. Motion control drives are known to monitor the motion performance of the mechanism. The feedback and the subsequent rectification, if needed, makes it ideally placed to be used in the robotics field. These drives are connected to motors that can be AC or DC. Further categorization can be made of DC brushed, DC brushless, AC Induction, AC synchronization and Stepper.

The motor amplifier or servo drive is designed to takes commands from the motion controller. These signals are incorporated in the analogue version where the voltage with low current is converted to high current signals in order to drive the motor. Motor drives come in many various types and makes and are fitted when matched to a specific motor they need to run. Along with matching the motor technology, the drive needs to ensure a balance of voltage, a continuous current and the balanced correct peak current.

The feedback of the mechanism’s performance can be taken of different parameters like back EMF, current, velocity, acceleration, position and many more. It’s because the control of these parameters will ensure the overall control of the motion of the object. Some of the sources for these feedbacks are:
  • Hall effect sensors
  • Encoder
  • Potentiometer
  • Tachometer
  • Acceleration specific sensor

A motion control drive’s range of applications is far more specialized than any other manufacturing applications. Motion control drives must be capable of:
  • Zero-speed holding torque
  • Quick start/stop cycles
  • Repeatable velocity and torque profiles
  • High accelerating torque
  • Synchronization
  • Precise speed control
  • Positioning capabilities

Motion control can operate two levels – the linear or the rotational axis. A linear axis application like a vehicle in motion has a pre-defined traversing range with predefined end stops. The rotational axis has a vast and almost never-ending traversing range when applied. A rotary table on the other hand travels a pre-defined yet short distance. They have a selected path or direction for moving point to point.


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