Motion control has evolved over time, from simple grid connected motors to complex multi-axis servo drive solutions for machine tools and industrial robots. This evolution has been accelerated by the increasing complexity of automation required to deliver higher levels of productivity, flexibility, and autonomy in smart manufacturing.
Grid-connected motors
The most basic motion solutions are based on a grid-connected or AC-powered, 3-phase fixed speed motor that uses a switchgear to provide on/off control and protection circuitry. These basic motion solutions run at a relatively fixed speed, independent of any load variation. A reduction in output is implemented with mechanical controls—throttles, dampers, gears or valves, pumps, and fans are some typical asset examples.
Inverter-driven motors
The addition of a rectifier, DC bus, and a 3-phase inverter stage in effect creates a variable frequency and variable voltage source that is now applied to the motor to enable variable speed control.
This inverter driven motor enables significant reduction in energy consumption by running the motor at the optimum speed for the load and application. Examples include higher efficiency pumps and fans.
Variable speed drives
For higher performance motion control applications, a variable speed drive (VSD) enables accurate torque, velocity, and position control. To achieve this, current and position measurement are added into the basic open-loop inverter drive. More precise control of motor velocity, position, and torque is then possible. Conveyors, winding, printing, and extrusion machinery are typical examples of these applications.
Servo-driven systems
Synchronized, multi-axis servo-driven systems are used in more complex motion applications. Machine tools and CNC machines require synchronization of multiple axes, with extremely accurate position feedback. In CNC machining, 5-axis coordination is common, although there are applications that utilize up to 12 axes in which tools and workpieces are both being moved with respect to each other in space.
Collaborative and mobile robots
Industrial robots require multi-axis servo drives combined with mechanical integration and advanced machine control algorithms to achieve complex 3D spatial positioning. Robots typically have six axes that need to be controlled in a coordinated manner, and sometimes seven if the robot is moving along a rail.
Collaborative robots (cobots) build on industrial robotic solutions by adding power and force limiting (PFL) to deliver functionally safe, multi-axis machine control where an operator can work safely alongside the cobot. Finally, self-navigating, functionally safe machine control is deployed in mobile robots, with localization sensing and collision avoidance.
