DCM motion technology

DCM Motion Technology is a term coined around 2003 by the Danish inventors Bo Fich and Mikkel Willadsen who started to work on how to extract meaningful information from the transient signals from DC motors.
Detection-Control-Monitoring of Brushed DC motors provides new ways of monitoring and controlling motors with commutators.
Without the use of external encoders and wires, the DCM Motion Technology makes it possible to Detect, Control and Monitor brushed DC motors based on a precise and revolving detection of specific physical points during each commutation.
Through the electronic encoding, it is possible to extract useful and valuable information about the real-time status and behaviour of any odd- or even poled brushed DC motor.

The technology is commercialised by IDEAdvance Ltd in the UK.
Detection
The DCM Motion Technology can be applied to mechanically commutated electric motors, i.e. motors where a brush and commutator arrangement changes the polarity of the current in the armature windings, as the armature rotates, within magnetic fields produced by the stator, see .
Many attempts to determine the commutation of mechanically commutated electric motors have been made, e.g. providing the motor with indicators, such as tachos, or by ripple counting on the supply current to the motor, i.e. the fluctuations on the supply current caused by the fact that the current in a coil cannot change momentarily because of the Back Electromotive Force. Such ripple counting is difficult because the commutator contacts normally supply current to several windings at the time in an overlapping manner.
The detection method in DCM Motion Technology is based on the physical behavior of a coil when a current running through it is disconnected (Law of Induction, see Electromagnetic Induction ). The Back-Fire transient from the collapsing magnetic field is identified in the coil when power to the coil is turned off. The Back-Fire or Kick-Back transient is a short duration event of a temporary excess voltage which is proven absolutely stable by its nature and is seen as a spark generated between the breaking contact points. The Kick-Back triggers the modulation of an electronic encoder signal for each of the motor commutations. Thus an N pole motor will encode N signals per rotation. The information from the Kick-Back can be extracted anywhere on the power wires to the motor.
Control
The signals extracted from the transient detection can be used to control commutated electric motors in various ways.
For example, the signals can be used to accurately count the rotational angle of the motor and to disconnect the power supply to the motor after a predetermined number of detected commutations. Thus in a number of applications it is possible to operate an ordinary mechanically commutated motor as a stepper motor (with a resolution determined by the number of commutations in the motor). This is a major advantage, as in many applications the high accuracy of a stepper motor is actually not required and ordinary motors cost far less than stepper motors.
In other typical electric motor applications, such a actuators for various automotive applications, it is possible to control the actuator motion without the need for sensors, e.g. hall effect sensors, thus offering a simple, reliable and cost effective actuator solution.
Another advantage of the DCM Motion Technology is that the detection kan be used to accurately control the supply current to the motor within each commutation. By controlling the supply current during a commutation the arcing which occurs during commutation can be reduced, thus leading to less wear and tear on the electric motor and a reduction in the production of corrosive gasses generated by arcing.
Various companies, e.g. Zetex Semiconductors plc, have previously reported work on how to remove commutation spikes from Brushless DC Motors but little has been reported on how to use the spikes for control purposes.
Monitoring
Different types of commutated electric motors may show different Back-Fire transients patterns. Individual commutators in a motor may also show sligthly different transient patterns, e.g. due to production variations or due to wear. The transient pattern from a motor may also change over time due to wear of the brushes. The signals detected by the DCM Motion Technology can be used for testing production inaccuracies during electric motor manufacturing (in-line production testing) as well as for monitoring, early fault detection and diagnostic analysis of commutated electric motors in critical or remote environments.

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