Bookmark.icon

Motion control

The process of controlling the motion of the camera by a computer in order to obtain precise control over its movement.

Motion control is a sub-field of automation, encompassing the systems or sub-systems involved in moving parts of machines in a controlled manner. The main components involved typically include a motion controller, an energy amplifier, and one or more prime movers or actuators. Motion control may be an open-loop or closed loop. In open-loop systems, the controller sends a command through the amplifier to the prime mover or actuator and does not know if the desired motion was achieved. Typical systems include stepper motor or fan control. For tighter control with more precision, a measuring device may be added to the system (usually near the end motion). When the measurement is converted to a signal that is sent back to the controller, and the controller compensates for any error, it becomes a Closed-loop System.

Typically the position or velocity of machines is controlled using some type of device such as a hydraulic pump, linear actuator, or electric motor, generally a servo. Motion control is an important part of robotics and CNC machine tools, however, in these instances, it is more complex than when used with specialized machines, where the kinematics are usually simpler. The latter is often called General Motion Control (GMC). Motion control is widely used in the packaging, printing, textile, semiconductor production, and assembly industries. Motion Control encompasses every technology related to the movement of objects. It covers every motion system from micro-sized systems such as silicon-type micro induction actuators to micro-siml systems such as a space platform. But, these days, the focus of motion control is the special control technology of motion systems with electric actuators such as dc/ac servo motors. Control of robotic manipulators is also included in the field of motion control because most of the robotic manipulators are driven by electrical servo motors and the key objective is the control of motion.

The basic architecture of a motion control system contains:

  • A motion controller to generate setpoints (the desired output or motion profile) and (in closed-loop systems) close a position or velocity feedback loop.
  • A drive or amplifier to transform the control signal from the motion controller into energy that is presented to the actuator. Newer "intelligent" drives can close the position and velocity loops internally, resulting in much more accurate control.
  • A prime mover or actuator such as a hydraulic pump, pneumatic cylinder, linear actuator, or electric motor for output motion.
  • In closed-loop systems, one or more feedback sensors such as absolute and incremental encoders, resolvers or Hall effect devices to return the position or velocity of the actuator to the motion controller to close the position or velocity control loops.
  • Mechanical components to transform the motion of the actuator into the desired motion, including gears, shafting, ball screw, belts, linkages, and linear and rotational bearings.

The interface between the motion controller and drives it controls is very critical when coordinated motion is required, as it must provide tight synchronization. Historically the only open interface was an analog signal until open interfaces were developed that satisfied the requirements of coordinated motion control, the first being SERCOS in 1991 which is now enhanced to SERCOS III. Later interfaces capable of motion control include Ethernet/IP, Profinet IRT, Ethernet Powerlink, and EtherCAT.

Common control functions include:

  • Velocity control.
  • Position (point-to-point) control: There are several methods for computing a motion trajectory. These are often based on the velocity profiles of a move such as a triangular profile, trapezoidal profile, or an S-curve profile.
  • Pressure or Force control.
  • Impedance control: This type of control is suitable for environment interaction and object manipulation, such as in robotics.
  • Electronic gearing (or cam profiling): The position of a slave axis is mathematically linked to the position of a master axis. A good example of this would be in a system where two rotating drums turn at a given ratio to each other. A more advanced case of electronic gearing is electronic camming. With electronic camming, a slave axis follows a profile that is a function of the master position. This profile need not be salted, but it must be an animated function

Key Terms

actuator
amplifier
controller
desired motion
hydraulic pump
linear actuator
motion control
motion controller
position
prime mover

Additional Resources

No ressources found.

Acronymn

(none found)

Synonymns

Motion control
(none found)

Comments

No comment found.

Sources & Credits

Last modified on November 9 2019
Content adapted from Wikipedia
No credits found.
Copyright 2019 Videocide.com  |  All Rights Reserved
linkedin facebook pinterest youtube rss twitter instagram facebook-blank rss-blank linkedin-blank pinterest youtube twitter instagram