Motion control Basics
Motion control Basics
Motion control is a type of automation in which the position and/or velocity of actuators, usually electric motors, are controlled.
The common architecture of a motion-control system is:
- a motion-control board to generate the trajectory and close the position loop, sometimes also the velocity loop (this is also known as servo control)
- a drive or amplifier to transform the velocity or torque signal into a high-power electrical current
- an electric motor for actuation (hydraulics and pneumatics may also be used)
- mechanical power transmission (e.g., gearbox)
- a feedback sensor (proximity switch, limit switch, photo-eye, etc) to return the motor position to the motion-control board and the amplifier
Motion control is a critical part of robotics, but is also the heart of special machines, where the kinematics are usually simpler. The latter is often called General Motion Control (GMC). Motion control is widely used in the industry for packaging, printing or assembly.
Control functions commonly encountered in motion control are:
- move at constant speed
- move to a desired position following a velocity-, acceleration- and jerk-limited trajectory (S-Curve). The ability to change (program) the destination during a motion is advantageous for productivity.
- electronic gearing or camming: the position of a slave axis is “geared” to the position of a master axis. In the case of camming, a pre-defined profile is applied in addition. The difficulty in e-gearing is the engaging phase, when the master is already moving.
Motion control systems often contain matched components such as controllers, motor drives, motors, encoders, user interfaces and software. Components in these systems are optimally matched by the manufacturer.
Motion controllers range from simple linear controllers to complex user-programmable modules that act as controllers within complex, integrated multi-axis motion systems.
Motion control software uses advanced algorithms for programming, monitoring, and optimizing digital motion control products.
Pendants: Industrial control pendants are sophisticated, handheld terminals which are used to control robot or machine movements from point to point, within a determined space. They consist of a hanging control console furnished with joysticks, push-buttons or rotary cam switches. Teach pendants are a specific type of industrial pendant. They are devices equipped with switches and dials used to control a robot’s movements to and from desired points within a determined space.
AC servomotors are responsive, high-acceleration motors typically constructed as permanent magnet synchronous motors. They are often used in motion-control systems, often coupled with sophisticated drive amplifiers. DC motor types (brushless, servo motor, and gear motor) as well as linear, stepper and air motors may also be used.
Torque sensors, gauges, instruments, and switches are used to measure torque in a variety of applications. They often provide useful feedback to motion-control electronics during operation.
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