MINI-ME - Miniature Inductive Motor Encoders

Billions of electric motors are made every year and the number is growing. Electric motors
are all around us - in our kitchen appliances, office equipment, heating & air-conditioning
systems, even our toys & games.
Traditionally, motors use carbon brushes to commutate power to their windings but the
brushes create dust and wear out. A growing proportion of motors are ‘brushless’. Rather
than carbon brushes, they trigger power to their windings according to rotor angle.
The situation can be compared with that of old and new cars. Older cars used a distributor
cap to energize the spark plugs in each of the engine’s cylinders – whereas modern cars use
electronic fuel injection. As with a car's engine, the key to performance in an electric motor is
precise triggering of the power injection point. This requires the angle of the rotor to be
measured accurately and quickly because even a tiny difference between the actual and ideal
trigger points makes a big difference to energy efficiency and performance.
Various sensing techniques have been used as motor encoders but each is problematic:-
- Hall effect is fairly inaccurate and limited to benign conditions
- optical encoders are delicate and unreliable in dirty or wet environments
- resolvers are too bulky or expensive for most applications.
The business opportunity is to offer system integrators, actuator & electric motor
manufacturers an encoder with the following advantages:-
- less cost
- more reliable
- greater operating envelope – notably at high temperatures
- long-life
- compact & lightweight
- accurate
- easy to install
- readily customized to suit specific applications
- ecologically friendly.
The concept that offers these advantages is called 'MINI-ME' (MINiature Inductive Motor
Encoder) which uses a novel sensing technique to contactlessly measure angle. MINI-ME's
patent is granted in UK and pending in USA, Germany, France & China. The next step to
commercial exploitation is to develop and test MINI-ME pre-production prototypes.
Development will lead to a range of MINI-ME products (of various sizes) being launched in
2014.
MINI-ME has excellent commercial prospects because it will enable manufacturers to get
more torque or speed from a given motor. This is possible because they will have more
precise and reliable control of motor energization. This means that for a given application a
smaller, less costly and more energy efficient motor can be used.
Improved control will also enable more accurate positioning of the motor rotor in lower speed
applications – notably in servo control of actuators. This is where MINI-ME's early adopters
will be quick to realize the technical advantages.
Appendix A provides a technical description.