Page 25 - Industrial Technology July 2021
P. 25

MACHINE BUILDING



       Miniaturisation means smaller,





       higher performing machines







                                                                                          use in motion control amplifiers. It involves a traditional
                                                                                          copper PCB which holds the integrated circuits onto a
                                                                                          relatively thick aluminium or copper substrate. This layer
                                                                                          acts as a dielectric layer which efficiently transfers the
                                                                                          heat from the PCB. The MCPCB thermal transfer
                                                                                          technology has accelerated the power density of motion
                                                                                          control amplifiers and the latest generation devices
                                                                                          achieve results of more than 100W per cc3.

                                                                                          The closer the better
                                                                                          The more compact the motion control device, the greater
                                                                                          the potential to deploy it locally or embed the motor and
                                                                                          controller into the host machine. These embedded
                                                                                          controllers can take the form of cable connected modules
                                                                                          or an application specific control board built from PCBs or
                                                                                          ICs. The control advantage of these devices, particularly
                                                                                          those that integrate analogue sensors such as sin/cos
                                                                                          encoders, is more accurate signals while the reduced
                                                                                          length of physical communications means higher speed
                                                                                          servo loops. These gains are augmented for ultra-high
                                                                                          accuracy systems where performance is measured in nano
                                                                                          or picometers.
       AS OEMS STRIVE TO DEVELOP EVER MORE MOBILE AND COMPACT                               As a result, the trend shifts closer towards the
                                                                                          advantage of embedded motion control solutions versus
       MACHINES, THE TREND IS FORCING MINIATURE MOTION CONTROL                            those which are remotely mounted, especially for smaller
       MANUFACTURERS TO MAINTAIN PACE. MINIATURE MOTORS AND                               machines requiring miniature motion control systems.
                                                                                          Even though the current technology may not represent
       CONTROLLERS ARE ENABLING PRECISION PERFORMANCE CONTROL
                                                                                          significant performance gains for large machines, even for
       WITH AN INCREASING NEED FOR RELIABILITY IN DEMANDING                               these applications a single PCB-based embedded motion
       APPLICATIONS. GERARD BUSH OF INMOCO EXPLAINS HOW IN                                solution creates a more compact footprint compared to an
                                                                                          external device.
       MEETING THE DEMANDS, MINIATURE MOTION TECHNOLOGY IS                                  Cost-wise, embedded control can be less expensive
       MOVING TOWARDS DECENTRALISED CONTROL.                                              than module-based control providing a sufficiently high
                                                                                          volume of devices are involved, but at the same time a
             he increased need for applications which are   operation for some applications using control techniques   new motion control device is easing the barrier to building
             mobile, lightweight and compact has passed on   such as electronic stall detection for stepper motors as   application specific embedded control boards. Known
             these same requirements to designers of   well as back-EMF for Brushless DC motors.   variously as an intelligent amplifier, programmable
       Tminiature motion control systems. Answering   However, the challenge for sensorless techniques in   amplifier, or motion control module, these PCB-mountable
       these demands, miniature motion solution development   many uses, such as electronic stall detection, can be to   devices simplify custom control board design and
       has also facilitated the reorganisation of machine   match the required level of reliability. This is pushing the   development.
       architecture, allowing OEMs to decentralise motion control   trend for even very small motors to upgrade their sensors   PCB-mounted motion control modules can run user
       to local, embedded positions. As a result, in addition to   or to include encoders where they were not previously   application code, generate motion profiles, control servo
       machines with highly compact footprints, this trend is   used. This demand for more robust sensors has also seen   positioning and drive the motor with an on-board
       enabling improved performance, increased reliability and   an increased trend for magnetic rather than optical   amplifier. These devices can also interface via serial, CAN
       helping to reduce costs.                 encoders, especially when deployed in harsh conditions   and Ethernet. Crucially they maintain the advantages of
         Brushless DC motors remain in favour for their high   and medical applications.   small size, measuring just 3-5cm in length and they can
       power to weight ratio and their ability to generate a                              be interconnected, plug-and-play style.
       constant torque up to high RPM. Alternatively, stepper  Miniature motion control     From drones to robots to patient treatment devices,
       motors are frequently used in portable applications as a   Whether using a motion control IC or a module, the most   compact and mobile applications continue to increase in
       result of their high torque to weight ratio. Despite the once   significant contributor to the size reduction in electronic   number while the machines themselves decrease in size.
       detracting effect of a lowered effective torque because of   motion controls is the performance increase of digital   Along with miniature motors, motion control electronics
       their tendency to oscillate, the stepper servo technique   switching amplifiers. Most frequently, this means the   have not only reduced in size and weight but have
       has resolved the issue and uses an encoder to enable   metal–oxide semiconductor field-effect transistor switch.   increased in performance capability. Performance has also
       higher torque across the operating range of the motor,   Today, MOSFETs are reliable and compact, with significant   been able to advance with the greater potential of
       eliminating mid-range instability.       improvements in energy losses to increase their efficiency.   distributed architecture that local, embedded motion
         Particularly for steppers, as motor size reduces it   Another advance has been in heat flow management   allows, at the same time increasing reliability with the
       becomes harder to add sensors without impacting the   and a new, specialized PCB, known as a metal clad   potential to reduce cost.
       overall footprint. This explains the trend in sensorless   printed circuit board (MCPCB) is gaining prominence for   MORE INFORMATION: www.inmoco.co.uk

       July 2021 • INDUSTRIAL TECHNOLOGY                                                                                       25
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