Apparatus and method for controlling brushless electric motors and position encoders and indicating position thereof

Abstract

A brushless direct current motor is energized by a power stage. Switches of the power stage are selectively switched by an electronic control device. In order to determine the correct commutation pattern, without using rotor position indicators such as Hall effect devices, the control device is arranged to sample the power fed to the motor. The samples, each responsive to a test signal or normal energization pulses received by the motor, in a ordered sequence define an analogue function whose parameters can be determined by mathematical analysis. The analysis applied to the samples derives the necessary commutation information and the energization signals in a rapid manner by employing a vector or complex number addition based on functions dependent on variable inductance in the operation of the motor.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]The invention of this application is related to that of our copending patent application Ser. No. 07 / 805,154, filed Dec. 11, 1991.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The invention relates to a motor or a position indicator (position sensor) comprising an apparatus or method for controlling a brushless electric motor. The term motor is here understood to mean also e.g. a linear motor, whose position is to be detected. Both a rotary motor and a linear motor has as its movable part a rotor.[0004]2. Description of the Related Art[0005]Different types of position sensors are known and are e.g. used for determining the position of motor elements. In most cases there is an associated linear acting principle for a rotary acting principle. The most important classes of such position sensors or indicators are based on the following:[0006]Position sensors with direct contact with the movable element:[0007]a) Mechanical con...

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Benefits of technology

[0044]These problems are solved according to the invention by the measures given in claim 1 and the following claims. The invention makes it possible to increase the usable speed range compared with the prior art. According to the invention using microelectronics means and the relevant software, it is possible to obtain an improved accuracy and reduce the relative errors during position determination.

Problems solved by technology

It is disadvantageous that in place of an externally fitted sensor, there must be a sensor in the form of at least one additional measuring coil within the motor.

However, the circuit suffers from the disadvantage that a range of 360° el to be measured is split up into two undistinguishable ranges of in each case 180° el.

Moreover the precision of the position determination is limited to approximately ±60° el.

However, here again the position determination precision is not adequate and the typically attainable precision is limited to ±15° el.

However, in such cases the reliability is limited by that of the sensor components, their feedline and by the operating temperature of the sensors and the control magnets.

However, it is relatively difficult to detect the position when the motor is stopped.

The difficulties more particularly consist of generating sufficiently precise position information within the shortest measurement time and signal processing time from a minimum of measurement information.

This sets increased demands on the power of the associated electronics and software used.

Another difficulty in the known methods is to exclude type-typical phase errors of ±180° el in the case of a rotor position determination.

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