What is Cabinet-Free Motion Control?

Controllers, drivers, and servomotors usually control automated platforms and machines in the automated production industry. With the evolvement of technology for machine motion, control and driving of individual machine axes is being increasingly taken over by highly intelligent electronics. Therefore, the control cabinet is assuming the central role with the rest of the system being designed around it.

With the rest of the machinery developing much more slowly, the faster evolving complex automation design and development becomes a cost-constraint for the OEM, system designers, and end users. Control cabinets need redesigning, especially with the increasing numbers of servo-driven axes. Typically, the location of the control cabinet is relatively fixed on the machine, which limits the manufacturers’ ability to modify and update the footprint of their machines.

As a solution to the above constraints, system designers are moving towards a new concept where the motion control and servo-drive mechanism is distributed rather than bound within a physical cabinet. By locating the controllers, servo drives, and power supplies nearer to the motors and axes they control, OEMs and system designers overcome several challenges arising from installation, cabling, and multiple engineering.

Initially, system designers had reoriented their designs in attempting to drive multiple machine components with a single servo motor. Although this approach had the benefit of reducing the physical number of servo motor and drives, it required a larger motor with higher power to handle the load, and several additional mechanical components for delivering the centralized power. A Cartesian motion system with a single motor for a palletizing application is an example of such a centralized approach.

By separating the servo motors on each axis, mounting them on the independent frames, and driving them separately, system engineers were able to use smaller motors, thereby reducing the overall power requirement, and developing a solution with higher efficiency.

One of the barriers to cabinet-free motion control architecture comes from PLC limitations. By limiting the axis count supported by their PLCs to 16 or 32 axes, some manufacturers force users to purchase a second PLC, which means addition of a more expensive control box with higher capacity.

For some time now, OEMs have been following a common practice of moving power supplies, servo drives, and related devices out of the control cabinet and placing them closer to each motor and its drive axis. This trend began with several leading suppliers introducing electric motors with their drives integrated into the motors’ housings. This required control electronics to be shock and vibration resistant as well as capable of withstanding the higher temperatures usually associated with environment outside the control cabinet.

Recent advances of cabinet-free components include separate ac-to-dc power supplies, independent drive units capable of mounting close to the servomotor on the machine, and power cables integrating communication capable of daisy-chaining several drive-integrated servomotors into a single circuit.

A further introduction of newer motion controllers or PLCs is helping the cabinet-free technology portfolio. These integrate the controller hardware into modules capable of mounting on the machine along with the necessary power supplies and drives. This eliminates the requirement of a control cabinet entirely.