GB2345204A - Motor control - Google Patents

Motor control Download PDF

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Publication number
GB2345204A
GB2345204A GB9908409A GB9908409A GB2345204A GB 2345204 A GB2345204 A GB 2345204A GB 9908409 A GB9908409 A GB 9908409A GB 9908409 A GB9908409 A GB 9908409A GB 2345204 A GB2345204 A GB 2345204A
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GB
United Kingdom
Prior art keywords
motor
speed
rotational speed
measurement
control system
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB9908409A
Other versions
GB9908409D0 (en
GB2345204B (en
Inventor
Jason Lewis
Dev Kumar Banerjee
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Penny & Giles Drives Technolog
Original Assignee
Penny & Giles Drives Technolog
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Penny & Giles Drives Technolog filed Critical Penny & Giles Drives Technolog
Priority to GB9908409A priority Critical patent/GB2345204B/en
Publication of GB9908409D0 publication Critical patent/GB9908409D0/en
Priority to US09/438,034 priority patent/US6184636B1/en
Priority to DE10019161A priority patent/DE10019161A1/en
Publication of GB2345204A publication Critical patent/GB2345204A/en
Application granted granted Critical
Publication of GB2345204B publication Critical patent/GB2345204B/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
    • H02P6/06—Arrangements for speed regulation of a single motor wherein the motor speed is measured and compared with a given physical value so as to adjust the motor speed
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
    • H02P6/14—Electronic commutators
    • H02P6/16—Circuit arrangements for detecting position
    • H02P6/17—Circuit arrangements for detecting position and for generating speed information

Abstract

A control system (2,4) for driving a brushless direct current (DC) motor (6), wherein driving signals are supplied to the stator windings of the motor in accordance with a measurement of the rotational speed of the motor and the position of the rotor of the motor. The speed measurement is obtained by combining a first signal representing the rotational speed of the motor (6) derived from a measurement (14) of the back-EMF developed in the stator windings of the motor and a second signal representing the rotational speed of the motor derived from the output (8,10,12) of means which sense the position of the rotor of the motor, such as a Hall-effect sensor.

Description

Motor Control The present invention relates to a control system for driving a brushless direct current (DC) motor.
Brushless DC motors are now commonplace and are typically driven by signals supplied to the stator windings of the motor in accordance with the outputs of one or more Halleffect sensors which detect the alignment therewith of the rotor poles of the motor.
Thus the requirement for brushes to effect commutation of the driving signals is obviated.
However, at low rotation speeds, smooth and stable control of the motor becomes difficult due the substantial time delays between successive changes of state of the Hall-effect sensor outputs.
We have now devised an arrangement which overcomes the limitations of existing control systems for driving DC brushless motors.
In accordance with the present invention, there is provided a control system for driving a brushless direct current (DC) motor, the control system comprising means for providing a measurement of the rotational speed of the motor by combining a first signal representing the rotational speed of the motor derived from a measurement of the back-EMF developed in the stator windings of the motor and a second signal representing the rotational speed of the motor derived from the output of means which sense the position of the rotor of the motor, such that as the rotational speed of the motor is increased from a first rotational speed to a second rotational speed, the combined speed measurement is determined to a greater extent by said second speed signal and to a lesser extent by said first speed signal, and means for supplying driving signals to the stator windings in accordance with the combined speed measurement and the position of the rotor of the motor.
Preferably at said first rotational speed the combined speed measurement is determined from said first speed signal only and preferably at said second rotational speed the combined speed measurement is determined from said second speed signal only.
Whilst the respective proportional contributions made to the combined speed measurement by each of said first and second speed signals may vary in one or more discrete steps between said first and second speeds, the respective proportional contributions preferably vary continuously with increasing or decreasing motor speed, thereby avoiding any abrupt transitions in the combined speed measurement.
Most preferably, within a region between said first and second speeds, the respective proportional contributions made to the combined speed measurement by each of said first and second speed signals vary linearly with respect to one another.
Preferably the position sensing means comprise one or more position sensing transducers. Most preferably the or each position sensing transducer comprises a Hall-effect sensor for detecting the alignment therewith of each of the rotor poles.
Also in accordance with the present invention, there is provided a method of driving a brushless direct current (DC) motor, wherein driving signals are supplied to the stator windings of the motor in accordance with a measurement of the rotational speed of the motor and the position of the rotor of the motor, the combined speed measurement being determined by combining a first signal representing the rotational speed of the motor derived from a measure of the back-EMF developed in the stator windings and a second signal representing the rotational speed of the motor derived from the output of means which sense the position of the rotor of the motor, such that as the rotational speed of the motor is increased from a first rotational speed to a second rotational speed, the combined speed measurement is determined to a greater extent by said second speed signal and to a lesser extent by said first speed signal.
An embodiment of the present invention will now be described by way of an example only and with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram of a prior art control system connected to a DC brushless motor; Figure 2 is a schematic diagram of a control system in accordance with the present invention connected to a DC brushless motor; and Figure 3 is a graph showing the variation in the proportional contribution made by each of two signals to a combined measurement of the speed of the motor, over a range of motor speeds.
Referring to Figure 1 of the drawings, a prior art control system is shown comprising a microprocessor 2 for controlling the output of an FET based switching amplifier 4 which applies a high frequency switched voltage signal to the stator windings of a three phase permanent magnet brushless DC motor 6.
Voltage is applied to each of the stator windings in turn, in accordance with the outputs 8,10,12 of three Halleffect sensors, mounted around the rotor, which sense passing magnetic fields produced by permanent magnets on the rotating rotor. The three sensors are mounted such that two of the sensors are mounted equidistantly from, and on either side of, the third sensor.
The outputs 8,10,12 of the Hall-effect sensors are used to synchronise the energising of respective stator windings by the switching amplifier to maintain a substantially constant phase relationship between the rotor flux and the stator flux, thereby maximising the torque of the motor.
To vary the speed of the motor, the voltage applied to the stator windings is pulse width modulated using a signal representing the speed of the motor determined by measuring the time taken between successive changes of state of the Halleffect sensor outputs. However, at low rotation speeds, the substantial time delays between successive Hall-effect sensor outputs mean that a signal accurately representing the present speed of the motor is difficult to obtain.
The above problem is overcome by the control system in accordance with the present invention, an embodiment of which is shown in Figure 2. The control system shown in Figure 2 corresponds to that shown in Figure l and like parts are given like reference numerals. In addition, the control system of Figure 2 is arranged to derive a measurement the speed of the motor from a measurement 14 of the back-EMF developed in the stator windings. At low rotational speeds, this signal provides a substantially more reliable representation of the speed of the motor than that derived from the Hall-effect sensor outputs.
The measurement of the back-EMF developed in the stator windings is preferably obtained using known means which measure the voltage V applied to each winding in turn and the resulting steady-state current I flowing through that winding, the back EMF being equal to V-IR, where R is the resistance of the winding.
In the control system of Figure 2, driving signals are applied to the stator windings of the motor 6 in accordance with a measurement of the rotational speed of the motor: this measurement is derived by combining a first signal derived from the measurement 14 of the back-EMF developed in the stator windings, and a second signal derived from the outputs 8,10,12 of the Hall-effect sensors, the first and second signals being combined such that as the rotational speed of the motor is increased from a first rotational speed to a second rotational speed, the combined speed measurement is determined to a greater extent by the second speed signal and to a lesser extent by the first speed signal.
In the calculation of the combined speed measurement, respective weightings Wf"Wf2 are applied to the first and second signals, over a range of rotational speeds including a first speed N, and a second speed N2 subject to the following conditions Wf2 = 1-Wfl N, > = 0 N2 > = N, if N, = 0 then N2 > 0 and for N < Nl, O < Wf, < =l and Wf, > Wf2 for N > N2, 0 < =Wf < 1 and Wfl < Wf-, for N, < =N < =N2, 0 < =Wf < =1 Figure 3 shows a first preferred weighting scheme, wherein Nl > 0 N2 > Ni and for N < Nj, Wfl for N > N2, Wf, > 0 Figure 4 shows a second preferred weighting scheme, wherein Nl > O N2 > N, and for N < Nl, Wf=1 for N > N2, Wf, =0 In each of the two embodiments illustrated, for rotational speeds less than NA or greater than N2, the respective weightings applied to the first and second speed signals are substantially constant. Also, the respective weightings Wf, and Wf2 vary linearly between N, and N2, thereby avoiding any abrupt transition in the value of the combined speed measurement.
However, it will be appreciated that for ease of implementation, Wf, and Wf2 may instead vary in one or more discrete steps between N, and N2.
The arrangement thus described overcomes the low speed limitations of existing brushless DC motor controllers whose driving signals are determined by rotor-position feedback devices alone.

Claims (1)

  1. Claims 1) A control system for driving a brushless direct current (DC) motor, the control system comprising means for providing a measurement of the rotational speed of the motor by combining a first signal representing the rotational speed of the motor derived from a measurement of the back-EMF developed in the stator windings of the motor and a second signal representing the rotational speed of the motor derived from the output of means which sense the position of the rotor of the motor, such that as the rotational speed of the motor is increased from a first rotational speed to a second rotational speed, the combined speed measurement is determined to a greater extent by said second speed signal and to a lesser extent by said first speed signal, and means for supplying driving signals to the stator windings in accordance with the combined speed measurement and the position of the rotor of the motor.
    2) A control system as claimed in Claim 1, wherein at said first rotational speed the combined speed measurement is determined from said first speed signal only 3) A control system as claimed in Claim 1 or Claim 2, wherein at said second rotational speed the combined speed measurement is determined from said second speed signal only.
    4) A control system as claimed in any preceding claim, wherein between said first and second rotational speeds the respective proportional contributions made to the combined speed measurement by each of said first and second speed signals vary continuously with increasing or decreasing motor speed.
    5) A control system as claimed in Claim 4, wherein between said first and second rotational speeds the respective proportional contributions made to the combined speed measurement by each of said first and second speed signals vary linearly with respect to one another.
    6) A control system as claimed in any preceding claim, wherein the position sensing means comprise one or more position sensing transducers.
    7) A control system as claimed in Claim 6, wherein the or each position sensing transducer comprises a Hall-effect sensor for detecting the alignment therewith of each of the rotor poles.
    8) A control system substantially as herein described with reference to the accompanying drawings.
    9) A method of driving a brushless direct current (DC) motor, wherein driving signals are supplied to the stator windings of the motor in accordance with a measurement of the rotational speed of the motor and the position of the rotor of the motor, the combined speed measurement being determined by combining a first signal representing the rotational speed of the motor derived from a measure of the back-EMF developed in the stator windings and a second signal representing the rotational speed of the motor derived from the output of means which sense the position of the rotor of the motor, such that as the rotational speed of the motor is increased from a first rotational speed to a second rotational speed, the combined speed measurement is determined to a greater extent by said second speed signal and to a lesser extent by said first speed signal.
    10) A method of driving a brushless direct current (DC) motor, the method being substantially as herein described with reference to the accompanying drawings.
    11) A brushless direct current (DC) motor driven by a control system, the control system comprising means for providing a measurement of the rotational speed of the motor by combining a first signal representing the rotational speed of the motor derived from a measurement of the back-EMF developed in the stator windings of the motor and a second signal representing the rotational speed of the motor derived from the output of means which sense the position of the rotor of the motor, such that as the rotational speed of the motor is increased from a first rotational speed to a second rotational speed, the combined speed measurement is determined to a greater extent by said second speed signal and to a lesser extent by said first speed signal, and means for supplying driving signals to the stator windings in accordance with the combined speed measurement and the position of the rotor of the motor.
    12) A brushless direct current (DC) motor substantially as herein described with reference to the accompanying drawings.
    Amendments to the claims have been filed as follows 1) A control system for driving a brushless direct current (DC) motor, the control system comprising means for providing a measurement of the rotational speed of the motor by combining a first signal representing the rotational speed of the motor derived from a measurement of the back-EMF developed in the stator windings of the motor and a second signal representing the rotational speed of the motor derived from the output of means which sense the position of the rotor of the motor, such that as the rotational speed of the motor is increased from a first rotational speed to a second rotational speed, the combined speed measurement is determined to a greater extent by said second speed signal and to a lesser extent by said first speed signal, and means for supplying driving signals to the stator windings in accordance with the combined speed measurement and the position of the rotor of the motor.
    2) A control system as claimed in Claim 1, wherein at said first rotational speed the combined speed measurement is determined from said first speed signal only 3) A control system as claimed in Claim 1 or Claim 2, wherein at said second rotational speed the combined speed measurement is determined from said second speed signal only.
    4) A control system as claimed in any preceding claim, wherein between said first and second rotational speeds the respective proportional contributions made to the combined speed measurement by each of said first and second speed signals vary continuously with increasing or decreasing motor speed.
    5) A control system as claimed in Claim 4, wherein between said first and second rotational speeds the respective proportional contributions made to the combined speed measurement by each of said first and second speed signals vary linearly with respect to one another.
    6) A control system as claimed in any preceding claim, wherein the position sensing means comprise one or more position sensing transducers.
    7) A control system as claimed in Claim 6, wherein the or each position sensing transducer comprises a Hall-effect sensor for detecting the alignment therewith of each of the rotor poles.
    8) A control system substantially as herein described with reference to Figures 2 and 3 of the accompanying drawings.
    9) A method of driving a brushless direct current (DC) motor, wherein driving signals are supplied to the stator windings of the motor in accordance with a measurement of the rotational speed of the motor and the position of the rotor of the motor, the combined speed measurement being determined by combining a first signal representing the rotational speed of the motor derived from a measure of the back-EMF developed in the stator windings and a second signal representing the rotational speed of the motor derived from the output of means which sense the position of the rotor of the motor, such that as the rotational speed of the motor is increased from a first rotational speed to a second rotational speed, the combined speed measurement is determined to a greater extent by said second speed signal and to a lesser extent by said first speed signal.
    10) A method of driving a brushless direct current (DC) motor, the method being substantially as herein described with reference to Figures 2 and 3 of the accompanying drawings.
    11) A brushless direct current (DC) motor driven by a control system, the control system comprising means for providing a measurement of the rotational speed of the motor by combining a first signal representing the rotational speed of the motor derived from a measurement of the back-EMF developed in the stator windings of the motor and a second signal representing the rotational speed of the motor derived from the output of means which sense the position of the rotor of the motor, such that as the rotational speed of the motor is increased from a first rotational speed to a second rotational speed, the combined speed measurement is determined to a greater extent by said second speed signal and to a lesser extent by said first speed signal, and means for supplying driving signals to the stator windings in accordance with the combined speed measurement and the position of the rotor of the motor.
    12) A brushless direct current (DC) motor substantially as herein described with reference to Figures 2 and 3 of the accompanying drawings.
GB9908409A 1999-04-14 1999-04-14 Motor control Expired - Lifetime GB2345204B (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
GB9908409A GB2345204B (en) 1999-04-14 1999-04-14 Motor control
US09/438,034 US6184636B1 (en) 1999-04-14 1999-11-10 Motor control
DE10019161A DE10019161A1 (en) 1999-04-14 2000-04-12 Engine control

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB9908409A GB2345204B (en) 1999-04-14 1999-04-14 Motor control

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GB9908409D0 GB9908409D0 (en) 1999-06-09
GB2345204A true GB2345204A (en) 2000-06-28
GB2345204B GB2345204B (en) 2000-11-15

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US (1) US6184636B1 (en)
DE (1) DE10019161A1 (en)
GB (1) GB2345204B (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1798559A2 (en) * 2005-12-14 2007-06-20 Robert Bosch Gmbh Method and device for determining the rotational speed of an electrical machine
WO2012064693A3 (en) * 2010-11-08 2013-04-18 Regal Beloit America Inc. Lossless snubber drive for a permanent magnet synchronous motor
ITTO20130129A1 (en) * 2013-02-15 2014-08-16 Magna Closures Spa SYSTEM AND METHOD FOR CHECKING AN ELECTRIC MOTOR WITHOUT CURRENT CONTINUOUS BRUSHES WITH SINE-PUMP DRIVING FOR A AUTOMOTIVE POWER ACTUATOR

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WO2002043225A1 (en) * 2000-11-27 2002-05-30 Duke University Power supplies for drive assemblies which minimize net torque and/or vibration thereof
US6517560B1 (en) 2000-11-27 2003-02-11 Duke University Hand-held surgical instruments employing magnetic couplings for simultaneous rotary and longitudinal oscillations of distal workpieces
US6478681B1 (en) 2000-11-27 2002-11-12 Duke University Magnetic couplings for imparting simultaneous rotary and longitudinal oscillations
EP1271761B1 (en) * 2001-06-20 2007-07-18 Nissan Motor Co., Ltd. Motor controller and control method thereof
DE10300634A1 (en) * 2003-01-10 2004-08-12 Knorr-Bremse Systeme für Nutzfahrzeuge GmbH Method for controlling an electronically commutated direct current motor
DE10339028A1 (en) * 2003-08-25 2005-03-31 Siemens Ag Method and apparatus for controlling a brushless DC motor
CN100413203C (en) * 2004-04-12 2008-08-20 乐金电子(天津)电器有限公司 Hull sensor position deviation guarantee method for motor direct driving washing machine using brushless DC motor
JP4613513B2 (en) * 2004-04-28 2011-01-19 日本精工株式会社 Electric power steering device
KR100685716B1 (en) * 2005-12-29 2007-02-26 삼성전기주식회사 Apparatus and method for controlling rpm of brushless dc motor
DE102015212812A1 (en) 2015-07-08 2017-01-12 Conti Temic Microelectronic Gmbh Operation of a rotating electrical machine

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Cited By (6)

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Publication number Priority date Publication date Assignee Title
EP1798559A2 (en) * 2005-12-14 2007-06-20 Robert Bosch Gmbh Method and device for determining the rotational speed of an electrical machine
EP1798559A3 (en) * 2005-12-14 2009-12-02 Robert Bosch Gmbh Method and device for determining the rotational speed of an electrical machine
WO2012064693A3 (en) * 2010-11-08 2013-04-18 Regal Beloit America Inc. Lossless snubber drive for a permanent magnet synchronous motor
US9379659B2 (en) 2010-11-08 2016-06-28 Regal Beloit America, Inc. Lossless snubber drive for a permanent magnet synchronous motor
ITTO20130129A1 (en) * 2013-02-15 2014-08-16 Magna Closures Spa SYSTEM AND METHOD FOR CHECKING AN ELECTRIC MOTOR WITHOUT CURRENT CONTINUOUS BRUSHES WITH SINE-PUMP DRIVING FOR A AUTOMOTIVE POWER ACTUATOR
US9876451B2 (en) 2013-02-15 2018-01-23 Magna Closures S.P.A. System and method for controlling a sinusoidal-drive brushless DC electric motor for an automotive power actuator

Also Published As

Publication number Publication date
GB9908409D0 (en) 1999-06-09
DE10019161A1 (en) 2000-11-09
GB2345204B (en) 2000-11-15
US6184636B1 (en) 2001-02-06

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Expiry date: 20190413