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Claims  |
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What is claimed is:
1. A brushless motor comprising:
a field means having a permanent magnet type rotor for producing P field poles (P is an even number integer not less than 2);
K-phase driving windings (K is an integer not less than 2) fixed to a stator;
driving commanding means for generating a substantially sinusoidal driving command signal; and
driving control means for supplying a substantially sinusoidal driving current to said driving windings responding to said driving command signal,
said driving commanding means comprising:
rotation detecting means for obtaining a pulse signal in synchronization with rotation of said rotor;
time interval measurement means for measuring a timing interval of said pulse signal; and
driving command generating means for estimating an estimated electric angle at an estimating interval shorter than said timing interval and responsive to a measurement result of said time interval measurement means, and generating the
substantially sinusoidal driving command signal corresponding to said estimated electric angle.
2. A brushless motor in accordance with claim 1, wherein said driving command generating means comprises:
electric angle estimating means for obtaining a generated timing signal at a time interval responding to the measurement result of said time interval measurement means, and estimating the estimated electric angle responding to generation of the
generated timing signal; and
command generating means for generating the substantially sinusoidal driving command signal corresponding to the estimated electric angle.
3. A brushless motor in accordance with claim 1, wherein said driving command generating means comprises:
electric angle estimating means for obtaining a generated timing signal at a time interval responding to the measurement result of said time interval measurement means, and estimating the estimated electric angle responding to generation of the
generated timing signal; and
command generating means for generating the substantially sinusoidal driving command signal corresponding to the estimated electric angle;
deviation amount detecting means for detecting a deviation of the estimated electric angle from a predetermined value at a timing of the pulse signal in said rotation detecting means; and
deviation correcting means for, in accordance with the deviation, correcting the time interval of the generated timing signal.
4. A brushless motor in accordance with claim 1, wherein said driving command generating means comprises:
electric angle estimating means for obtaining a generated timing signal at a time interval responding to the measurement result of said time interval measurement means, and estimating the estimated electric angle responding to generation of the
generated timing signal; and
command generating means for generating the substantially sinusoidal driving command signal corresponding to the estimated electric angle; and
deviation correcting means for correcting the estimated electric angle to a predetermined value at a timing of the pulse signal in said rotation detecting means.
5. A brushless motor in accordance with claim 1, wherein said driving command generating means comprises:
electric angle estimating means for obtaining a generated timing signal at a time interval responding to the measurement result of said time interval measurement means, and estimating the estimated electric angle responding to generation of the
generated timing signal; and
command generating means for generating the substantially sinusoidal driving command signal corresponding to the estimated electric angle;
acceleration/deceleration detecting means for detecting an acceleration/deceleration state of said rotor; and
acceleration/deceleration correcting means for, in accordance with an output of said acceleration/deceleration detecting means, correcting the time interval of the generated timing signal.
6. A brushless motor in accordance with claim 1, wherein said driving command generating means comprises:
electric angle estimating means for obtaining a generated timing signal at a time interval responding to the measurement result of said time interval measurement means, and estimating the estimated electric angle responding to generation of the
generated timing signal; and
command generating means for generating the substantially sinusoidal driving command signal corresponding to the estimated electric angle;
deviation amount detecting means for detecting a deviation of the estimated electric angle from a predetermined value at a timing of the pulse signal in said rotation detecting means; and
deviation correcting means for, in accordance with the deviation, correcting the time interval of the generated timing signal;
acceleration/deceleration detecting means for detecting an acceleration/deceleration state of said rotor; and
acceleration/deceleration correcting means for, in accordance with an output of said acceleration/deceleration detecting means, correcting the time interval of the generated timing signal.
7. A brushless motor in accordance with claim 1, wherein said driving commanding means further comprises:
position detecting means for generating a rotational position signal corresponding to a rotational position of said rotor; and
start driving command generating means for, in a start process, generating the driving command signal in accordance with the rotational position signal.
8. A brushless motor in accordance with claim 1, wherein said driving commanding means uses said rotation detecting means for obtaining the pulse signal corresponding to a counter electromotive force generated in said driving windings during
rotation.
9. A brushless motor comprising:
a field means having a rotor for producing P field poles (P is an even number not less than 2);
K-phase driving windings (K is an integer not less than 2) fixed to a stator;
driving commanding means for generating a substantially sinusoidal driving command signal; and
driving control means for obtaining a current feedback signal corresponding to a current supplied to said driving windings, and supplying a substantially sinusoidal driving current to said driving windings in accordance with a result of
comparison between the driving command signal and the current feedback signal,
said driving commanding means comprising:
rotation detecting means for obtaining a pulse signal in synchronization with rotation of said rotor;
time interval measurement means for measuring a timing interval of said pulse signal;
electric angle estimating means for obtaining a generated timing signal at a time interval responding to the measurement result of said time interval measurement means, and estimating the estimated electric angle responding to generation of the
generated timing signal; and
command generating means for generating the substantially sinusoidal driving command signal corresponding to the estimated electric angle;
deviation amount detecting means for detecting a deviation of the estimated electric angle from a predetermined value at a timing of the pulse signal in said rotation detecting means; and
deviation correcting means for, in accordance with the deviation, correcting the time interval of the generated timing signal.
10. A brushless motor in accordance with claim 9, wherein said driving commanding means further comprises:
acceleration/deceleration correcting means for, in accordance with an output of said acceleration/deceleration detecting means, correcting the time interval of the generated timing signal.
11. A brushless motor in accordance with claim 9, wherein said driving commanding means further comprises:
position detecting means for generating a rotational position signal corresponding to a rotational position of said rotor; and
start driving command generating means for, in a start process, generating the driving command signal in accordance with the rotational position signal.
12. A brushless motor according to claim 9, wherein said driving commanding means uses said rotation detecting means for obtaining the pulse signal corresponding to a counter electromotive force generated in said driving windings during
rotation.
13. A brushless motor comprising:
a field means having a permanent magnet type rotor for producing P field poles (P is an even number not less than 2),
K-phase driving windings (K is an integer not less than 2) fixed to a stator;
current commanding means for generating a current command signal;
current detecting means for obtaining a current feedback signal corresponding to a current supplied to said driving windings;
transforming and comparing means for comparing the current feedback signal with the current command signal; and
driving control means for supplying a substantially sinusoidal driving current to said driving windings in accordance with an output signal of said transforming and comparing means,
said transforming and comparing means comprising:
rotation detecting means for obtaining a pulse signal in synchronization with rotation of said rotor;
time interval measurement means for measuring a timing interval of said pulse signal;
electric angle estimating means for obtaining a generated timing signal at a time interval responding to a measurement result of said time interval measurement means, and estimating an estimated electric angle responding to generation of the
generated timing signal;
transform feedback means for obtaining a transformed feedback signal by operating coordinate transformation on the current feedback signal with the estimated electric angle;
control signal generating means for obtaining a control signal responding to a result of comparison between the transformed feedback signal and the current command signal;
transformed control signal generating means for obtaining a transformed control signal which is obtained by operating coordinate transformation on the control signal with the estimated electric angle; and
output generating means for obtaining the output signal responding to the transformed control signal.
14. A brushless motor in accordance with claim 13, wherein said transforming and comparing means further comprises:
deviation amount detecting means for detecting a deviation of the estimated electric angle from a predetermined value at a timing of the pulse signal in said rotation detecting means; and
deviation correcting means for, in accordance with the deviation, correcting the time interval of the generated timing signal.
15. A brushless motor in accordance with claim 13, wherein said transforming and comparing means further comprises:
deviation correcting means for correcting the estimated electric angle to a predetermined value at a timing of the pulse signal in said rotation detecting means.
16. A brushless motor in accordance with claim 13, wherein said transforming and comparing means further comprises:
acceleration/deceleration detecting means for detecting an acceleration/deceleration state of said rotor; and
acceleration/deceleration correcting means for, in accordance with an output of said acceleration/deceleration detecting means, correcting the time interval of the generated timing signal.
17. A brushless motor in accordance with claim 13, wherein said transforming and comparing means further comprises:
position detecting means for generating a rotational position signal corresponding to a rotational position of said rotor; and
means for, in a start process, changing the output signal of said transforming and comparing means responding to the rotational position signal.
18. A brushless motor in accordance with claim 13, wherein said transforming and comparing means uses said rotation detecting means for obtaining the pulse signal corresponding to a counter electromotive force generated in said driving windings
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Claims |
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Description |
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FIELD OF THE INVENTION AND RELATED ART STATEMENT
1. Field of the Invention
The invention relates to a brushless motor wherein a substantially sinusoidal driving current is supplied in synchronization with rotation of rotor.
2. Description of the Related Art
Recently, many brushless motors are used which detects the rotational position of the rotor and switches currents to be supplied to the driving windings, thereby conducting the rotation driving in a predetermined direction.
FIG. 23 shows the configuration of a prior art brushless motor. A position detector 502 consists of an optical rotary encoder which is disposed so as to be coaxial with a rotor magnet 501. The optical rotary encoder has three photocouplers
respectively consisting of light emitting diodes 503a, 503b, and 503c, and phototransistors 504a, 504b, and 504c. An optical slit 505 is disposed between the light emitting diodes and the respective phototransistors so that the position of the optical
slit 505 is changed as the rotor magnet 501 is rotated, thereby changing the outputs of the phototransistors 504a, 504b, and 504c. The output currents of the phototransistors 504a, 504b, and 504c are converted into three-phase detection voltages by
resistors 507a, 507b, and 507c. Comparators 510a, 510b, and 510c compare the detection voltages of the respective phases with a reference voltage of a reference voltage source 508 and generate three-phase digital signals. The output digital signals
from the comparators 510a, 510b, and 510c are amplified by amplifiers 511a, 511b, and 511c and then applied to the three-phase driving windings 520a, 520b, and 520c.
In accordance with rotation of the rotor magnet 501, the position of the optical slit 505 is changed so that the output digital signals of the comparators 510a, 510b, and 510c are changed. As a result, the driving voltages applied to the driving
windings 520a, 520b, and 520c are switched and a torque in a predetermined direction is continuously generated.
However, such a configuration of the prior art has the following problems.
First, in the prior art configuration, since the position detector which detects the rotational position of the rotor and which has a relatively simple structure is used, the power supply to the driving windings is conducted by means of a
rectangular voltage. As a result, the currents are distorted by the inductances of the windings so that the driving torque is largely varied. Furthermore, the current distortion due to the digital voltage switching causes the motor to vibrate and
produces noises, thereby producing large problems.
Second, since the position detector has an optical rotary encoder configured by the three light emitting diode, three phototransistors and the optical slit, the position detector has a large number of parts and wirings, thereby making the
mass-production of the position detector very cumbersome. The parts for position detection which are disposed in the vicinity of the rotor magnet and the driving windings are used in a severe environment which has a high temperature and is dusty.
Therefore, it is preferable to reduce the parts to a number as small as possible.
OBJECT AND SUMMARY OF THE INVENTION
It is a primary object of the invention to provide a brushless motor which can solve the first problem of the prior art and supply a sinusoidal driving current by using a rotary detector having a simple structure. It is another object of the
invention to provide a brushless motor which can solve the first and second problems and supply a sinusoidal driving current by using a rotary detector having a very simplified structure.
In the brushless motor of the invention, timing intervals of a pulse signal which is synchronized with rotation of the rotor are measured, an estimated electric angle is estimated at estimating time intervals according to the measurement result,
and substantially sinusoidal driving currents corresponding to the estimated electric angle are supplied to the driving windings. Therefore, adverse current distortion due to the winding inductance exerts a very small influence. Therefore, a driving
torque which is less varied, namely is uniform, is obtained. Accordingly, the motor is smoothly rotated and vibration and noises of the motor are reduced to a very low level. Furthermore, the pulse signals for detecting rotation can be reduced in
number, and hence it is possible to employ a rotation detector with a reduced number of parts and a simple structure.
In order to achieve the above-mentioned object, the brushless motor in accordance with the present invention comprises:
a field means having a permanent magnet type rotor for producing P field poles (P is an even number integer not less than 2);
K-phase driving windings (K is an integer not less than 2) fixed to a stator;
driving commanding means for generating a substantially sinusoidal driving command signal; and driving control means for supplying a substantially sinusoidal driving current to the driving windings responding to the driving command signal,
the driving commanding means comprising:
rotation detecting means for obtaining a pulse signal in synchronization with rotation of the rotor;
time interval measurement means for measuring a timing interval of the pulse signal; and
driving command generating means for estimating an estimated electric angle at an estimating interval shorter than the timing interval and responsive to a measurement result of the time interval measurement means, and generating the substantially
sinusoidal driving command signal corresponding to the estimated electric angle.
In order to achieve the above-mentioned object, another aspect of the brushless motor in accordance with the present invention comprises:
a field means having a rotor for producing P field poles (P is an even number not less than 2);
K-phase driving windings (K is an integer not less than 2) fixed to a stator;
driving commanding means for generating a substantially sinusoidal driving command signal; and
driving control means for obtaining a current feedback signal corresponding to a current supplied to the driving windings, and supplying a substantially sinusoidal driving current to the driving windings in accordance with a result of comparison
between the driving command signal and the current feedback signal,
the driving commanding means comprising:
rotation detecting means for obtaining a pulse signal in synchronization with rotation of the rotor;
time interval measurement means for measuring a timing interval of the pulse signal;
electric angle estimating means for obtaining a generated timing signal at a time interval responding to the measurement result of the time interval measurement means, and estimating the estimated electric angle responding to generation of the
generated timing signal; and
command generating means for generating the substantially sinusoidal driving command signal corresponding to the estimated electric angle;
deviation amount detecting means for detecting a deviation of the estimated electric angle from a predetermined value at a timing of the pulse signal in the rotation detecting means; and
deviation correcting means for, in accordance with the deviation, correcting the time interval of the generated timing signal.
In order to achieve the above-mentioned object, still other aspect of the brushless motor in accordance with the present invention comprises:
a field means having a permanent magnet type rotor for producing P field poles (P is an even number not less than 2),
K-phase driving windings (K is an integer not less than 2) fixed to a stator;
current commanding means for generating a current command signal;
current detecting means for obtaining a current feedback signal corresponding to a current supplied to the driving windings;
transforming and comparing means for comparing the current feedback signal with the current command signal; and
driving control means for supplying a substantially sinusoidal driving current to the driving windings in accordance with an output signal of the transforming and comparing means,
the transforming and comparing means comprising:
rotation detecting means for obtaining a pulse signal in synchronization with rotation of the rotor;
time interval measurement means for measuring a timing interval of the pulse signal;
electric angle estimating means for obtaining a generated timing signal at a time interval responding to a measurement result of the time interval measurement means, and estimating an estimated electric angle responding to generation of the
generated timing signal;
transform feedbacking means for obtaining a transformed feedback signal by operating coordinate transformation on the current feedback signal with the estimated electric angle;
control signal generating means for obtaining a control signal responding to a result of comparison between the transformed feedback signal and the current command signal;
transformed control signal generating means for obtaining a transformed control signal which is obtained by operating coordinate transformation on the control signal with the estimated electric angle; and
output generating means for obtaining the output signal responding to the transformed control signal.
According to these configurations, a new estimated electric angle is sequentially obtained at time intervals synchronized with rotation of the rotor, by using only the pulse signal of the rotation detection means. While conducting the generation
of the driving command signal, or the coordinate transformation by using the electric angle, the sinusoidal driving command signal corresponding to the estimated electric angle is supplied. Even when the rotor is rotated at a higher or lower speed,
therefore, the electric angle can be correctly estimated so that the supply of a sinusoidal driving current synchronized with the rotational position is realized. Since a substantially sinusoidal driving current is supplied to the driving windings in
this way, the driving current is smoothly changed and hence the current distortion due to the winding inductance is reduced to a very small level. Consequently, a driving torque which is less varied or is uniform is obtained, with the result that the
motor is smoothly rotated and vibration and noises of the motor are reduced to a very low level.
The pulse signal of the rotation detection means is not always required for three phases. Even when only one pulse signal is used, the invention can be configured. Consequently, parts which are to be disposed in the vicinity of the driving
windings can be largely reduced in number, and hence the rotation detection means can have a simple structure. In the specification, an electric angle of 360 degree corresponds to two poles of the field unit. And the terms of a sinusoidal driving
command signal and a sinusoidal driving current mean that the driving command signal and the driving current vary sinusoidally in response to the change of the electric angle.
Further in this invention, the words "substantially sinusoidal" includes not only sinusoidal, but also like-sinusoidal, or analogously sinusoidal, or effectively sinusoidal, or nearly sinusoidal, etc., which will give similar or effectively
analogous works to sinusoidal.
While the novel features of the invention are set forth particularly in the appended claims, the invention, both as to organization and content, will be better understood and appreciated, along with other objects
and features thereof, from the following detailed description taken in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a circuit diagram of a first embodiment of the invention.
FIG. 2 is a diagram of the motor of the first embodiment.
FIG. 3 is a circuit diagram of a rotation detector 41 of the first embodiment.
FIG. 4 is a circuit diagram of a time interval measurement unit 42 of the first embodiment.
FIG. 5 is a circuit diagram of an electric angle estimator 44 of the first embodiment.
FIG. 6 is a flowchart of a command generator 45 of the first embodiment.
FIG. 7 is a circuit diagram of a driving controller 22 and a power supply unit 23 of the first embodiment.
FIG. 8 is a waveform chart illustrating the operation of the first embodiment.
FIG. 9 is a circuit diagram of a second embodiment of the invention.
FIG. 10 is a first flowchart of a microcomputer 101 of the second embodiment.
FIG. 11 is a second flowchart of the microcomputer 101 of the second embodiment.
FIG. 12 is a third flowchart of the microcomputer 101 of the second embodiment which is used in place of the first flowchart.
FIG. 13 is a circuit diagram of a third embodiment of the invention.
FIG. 14 is a diagram of the motor of the third embodiment.
FIG. 15 is a circuit diagram of a rotation detector 201 of the third embodiment.
FIG. 16 is a first flowchart of a microcomputer 101 of the third embodiment.
FIG. 17 is a second flowchart of the microcomputer 101 of the third embodiment.
FIG. 18 is a waveform chart illustrating the operation of the third embodiment.
FIG. 19 is a circuit diagram of a fourth embodiment of the invention.
FIG. 20 is a first flowchart of a microcomputer 312 of the fourth embodiment.
FIG. 21 is a second flowchart of the microcomputer 312 of the fourth embodiment.
FIG. 22 is a circuit diagram of a PWM device 303 and a power supply unit 23 of the fourth embodiment, and
FIG. 23 is a diagram of a prior art brushless motor.
It will be recognized that some or all of the Figures are schematic representations for purposes of illustration and do not necessarily depict the actual relative sizes or locations of
the elements shown.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[Embodiment 1]
Hereinafter, an embodiment of the invention will be described with reference to the accompanying drawings.
FIGS. 1 to 7 show a brushless motor of a first embodiment of the invention. FIG. 2 shows the structure of the motor of the first embodiment. A rotor permanent magnet 12 which produces magnetic fluxes of four field poles is fixed together with
an inner yoke 11 which is made of a ferromagnetic material and constitutes inner magnetic paths to the rotating shaft 10 of the rotor. The permanent magnet 12 has four magnetic poles (N, S, N, and S) which are arranged at equal angular intervals (90
degree) or at substantially equal angular intervals. An outer yoke 13 which is made of a ferromagnetic material, e.g. soft iron, is fixed to the outer peripheral face of the permanent magnet. The outer yoke 13 comprises yoke blocks 13a, 13b, 13c, and
13d which constitute outer magnetic paths at positions for covering the pole face of the permanent magnet 12. The portions which mechanically connect the four yoke blocks to each other are very thin in the radial direction so that magnetic saturation
occurs in the portions. Thereby, the yoke blocks are magnetically separated from each other. In other words, fluxes which directly pass through the connecting portions of the yoke blocks are so small in magnitude that they are negligible. The rotating
shaft 10, the inner yoke 11, the permanent magnet 12, and the outer yoke 13 are integrated so as to form the rotor, thereby configuring a field unit in which four field poles are formed by using fluxes generated by the permanent magnet 12 of the rotor.
In a stator core 14, twelve salient poles are arranged at equal angular intervals (30 degree in this embodiment) or at substantially equal angular intervals. And driving windings A1, A2, A3, A4, B1, B2, B3, B4, C1, C2, C3, and C4 are wound on
the stator core 14 in the manner that each winding or coil is wound on three salient poles and the windings are shifted in phase from each other. The driving windings A1, A2, A3, and A4 are connected in series in the manner that the current directions
in the windings are alternately inverted, thereby forming a first-phase driving winding 20A. Similarly, the driving windings B1, B2, B3, and B4 are connected in series in such a manner that the current directions in the windings are alternately
inverted, thereby forming a second-phase driving winding 20B, and the driving windings C1, C2, C3, and C4 are connected in series in the manner that the current directions in the windings are alternately inverted, thereby forming a third-phase driving
winding 20C.
The fluxes generated by the permanent magnet 12 of the field unit pass through the yoke blocks 13a, 13b, 13c, and 13d to enter the salient poles or salient teeth of the stator core 14 so as to link the driving windings. With respect to the
linkage fluxes due to the permanent magnet 12, there exist phase differences of an electric angle of 120 degree among the first-, second- and third-phase driving windings. In the embodiment, a mechanical angle of 180 degree (a mechanical angle for two
poles) corresponds to an electric angle of 360 degree.
A single detection device 17 is disposed at a part of the stator core 14. The detection device detects the fluxes generated by the permanent magnet 12 attached to the rotor and generates an electric signal corresponding to the magnitude of the
detected fluxes. As the detection device 17, useful are a Hall element, a magnetoresistive element which is magnetically biased, a saturable reactor, etc.
FIG. 1 shows the circuit configuration of the brushless motor of the first embodiment. In FIG. 1, numeral 5 designates the rotor, numerals 20A, 20B, and 20C respectively designate the three-phase driving windings. Output signals of the driving
command unit 21 are given to a driving controller 22. And output signals of the driving controller 22 are given to a power supply unit 23 as control signals. In this invention, an arrow mark with inclined short bar crossing thereon indicates plural
output ports or plural output lines in comprehensive manner. Three current detectors 24a, 24b, and 24c are coupled to three output lines of the power supply unit 23, respectively, so as to give detection outputs to the driving controller 22. The power
supply unit 23 comprises upper driving transistors 31a, 3lb, and 31c, upper diodes 32a, 32b, and 32c, lower driving transistors 33a, 33b, and 33c, and lower diodes 34a, 34b, and 34c. In the embodiment, the driving transistors 31a, 31b, 31c, 33a, 33b,
and 33c are MOS FETs. The driving command unit 21 comprises a rotation detector 41, a time interval measurement unit 42, and a driving command generation unit 43 (an electric angle estimator 44 and a command generator 45), and further comprises a
controller 46 as required.
The rotation detector 41 of the driving command unit 21 generates from an output signal of the detection device 17 a pulse signal g of a frequency which is proportional to the rotational speed of the rotor. FIG. 3 shows an example of the
configuration of the rotation detector 41. The output signal e of the detection device 17 is amplified by a low-pass or band-pass amplifier 51 and then waveform-shaped into the pulse signal g by a shaping circuit 52. Since the detection device 17
detects the fluxes of the permanent magnet 12 attached to the rotor, the pulse signal g is generated in synchronization with rotation of the rotor so that one pulse is generated as a result of the rotation corresponding to two poles. In other words, one
pulse is generated as a result of the rotation of an electric angle of 360 degree The timing when the pulse is changed corresponds to that when the detection device 17 opposes one of switching positions where the poles of the permanent magnet 12 are
switched over.
The time interval measurement unit 42 receives the output pulse signal g of the rotation detector 41 and measures the intervals of adjacent falling edges of the pulse signal g. FIG. 4 shows an example of the configuration of the time interval
measurement unit 42. As shown in FIG. 3, the rotation detector 41 comprises the detection device 17, an amplifier 51 for amplifying the output signal of the detection device 17, and a shaping circuit 52 for shaping waveform of the amplifier output
signal. By using a falling edge of the pulse signal g as a trigger, a first differentiating circuit 61 generates a first differential pulse which is "H" (high potential state) during a predetermined interval, and, with using a falling edge of the first
differential pulse as a trigger, a second differentiating circuit 62 generates a second differential pulse y which is "H" during a predetermined interval. A first counter circuit 64 is reset by the generation of the second differential pulse y, and
counts up the clock pulse ck1 of a first clock circuit 63. The count value of the first counter circuit 64 is latched by a first latch circuit 65 at the timing of the generation of the first differential pulse of the first differentiating circuit 61.
The latched value is output as an output signal f of the time interval measurement unit 42. Consequently, the output signal f of the first latch circuit 65 is a time measurement result corresponding to the timing interval of the pulse signal g.
The driving command generation unit 43 which consists of the electric angle estimator 44 and the command generator 45 receives the measurement result signal f of the time interval measurement unit 42, estimates the electric angle corresponding to
the rotational position of the rotor, and outputs three-phase sinusoidal driving command signals ja, jb, and jc by using the electric angle. The amplitudes of the driving command signals ja, jb, and jc are changed in accordance with current command
signals jq and jd of the controller 46.
FIG. 5 shows an example of the configuration of the electric angle estimator 44. A multiplying circuit 71 in FIG. 5 multiplies the measurement result signal f of the time interval measurement unit 42 by a correction signal n (which is
substantially equal to 1) of a correction coefficient circuit 78 which will be described later. A second latch circuit 72 latches a multiplied signal from the multiplying circuit 71 in response to the generation of the second differential pulse y. A
second counter circuit 74 counts down the clocks pulse ck2 of a second clock circuit 73. At the timing when the count value reaches zero, the second counter circuit outputs an internal timing signal (zero detection pulse) z of a predetermined pulse
width. At the timing when the next clock pulse ck2 reaches, the latched value of the second latch circuit 72 is loaded into the second counter circuit 74, and the count-down operation is then continued. Each time the count value reaches zero, the
second counter circuit 74 repeats the above-mentioned operation so that the internal timing signal (zero detection pulse) z is output at time intervals corresponding to the latched value of the second latch circuit 72. The frequency of the clock pulse
ck2 of the second clock circuit 73 is higher than that of the clock pulse ck1 of the first clock circuit 63 by a predetermined factor. In the embodiment, for the sake of convenience of description, the frequency of the clock pulse ck2 is 12 times of
that of the clock pulse ck1, i.e., frequency ratio of [ck2/ck1] is 12 (a higher ratio is better, and the ratio of 36 or higher is actually preferable). As a result, the second counter circuit 74 outputs the internal timing signal z at time intervals
which are about 1/12 times the intervals of the detection timing (the intervals of the edge of the pulse signal g) of the time interval measurement unit 42. A third counter circuit 75 counts up the clock pulse of the internal timing signal z. When the
count value v of the third counter circuit 75 reaches a second preset value v2 as shown in FIG. 8(e), a second-preset value detection circuit 77 is activated so that a first-preset value v1 of a first preset value output circuit 76 is loaded into the
third counter circuit 75 at the timing of the next pulse of the internal timing signal z. Thereafter, the count-up operation continues sequentially in response to the generation of the internal timing signal z. As a result, count value v of the third
counter circuit 75 is in the range between the first and second preset values v1 and v2. The count value v represents the electric angle. In the embodiment, for the sake of convenience of description, the values are set in terms of an electric angle so
that vl=-180 degree, and v2=180 degree-(one step)=150 degree.
The correction coefficient circuit 78 obtains the correction signal n from the count value v of the third counter circuit 75. The correction signal n is used only at the timing when the second differential pulse y is generated for activating the
second latch circuit 72. The correction signal n will be described. The correction coefficient circuit 78 sets the correction signal n in the following manner. When the count value (converted into an electric angle) v of the third counter circuit 75
is equal to zero, the correction signal n is set to be 1. When the count value v is negative, the correction signal n is set to be (1+k) where k is a negative correction value according to the ratio with respect to an electric angle of 360 degree. When
the count value v is positive, the correction signal n is set to be (1+k) where k is a positive correction value according to the ratio with respect to an electric angle of 360 degree. When a deviation v3 from a predetermined value (zero) of the count
value v (electric angle) at the timing of the generation of the second differential pulse y is detected, therefore, the correction signal n corresponding to the deviation v3 is obtained. The measurement output signal f of the time interval measurement
unit 42 is subjected to multiplication correction and then stored in the second latch circuit 72. The latched value of the second latch circuit 72 will function as data for determining the cycle time intervals (the time intervals of generating the
internal timing signal z) of the second counter circuit 74. Therefore, the time intervals of generating the internal timing signal z are corrected by the correction signal n of the correction coefficient circuit 78.
FIG. 8 is a signal waveform chart illustrating the operational relationships between the main portions of the rotation detector 41, the time interval measurement unit 42, and the electric angle estimator 44 (in the figure, the waveforms are shown
in the form of analog waveforms). In each waveform of FIG. 8, abscissa is graduated with time, and ordinate with signal amount. A flux detection signal ((a) of FIG. 8) of the rotor permanent magnet 12 which is output from the detection device 17 is
waveform-shaped by the rotation detector 41, and then output as the pulse signal g ((b) of FIG. 8). The first counter circuit 64 of the time interval measurement unit 42 digitally measures the timing intervals of falling edges of the pulse signal g ((c)
of FIG. 8), and the output signal f of the first latch circuit 65 is obtained as the measurement result. The second counter circuit 74 of the electric angle estimator 44 periodically counts down from the latched value of the second latch circuit 72 in
accordance with the output signal f of the time interval measurement unit 42 ((d) of FIG. 8), so that, each time the count value reaches zero, the internal timing signal (zero detection pulse) z is generated. Each time the internal timing signal z is
generated, the count value ((e) of FIG. 8) of the third counter circuit 75 corresponding to the estimated electric angle is changed and then output as the electric angle signal v. The deviation v3 between a predetermined value (zero in this embodiment)
and the value of the estimated electric angle at the timing of a falling edge of the pulse signal g is detected. The measurement result signal f of the time interval measurement unit 42 is multiplied by the correction signal n corresponding to the
deviation v3, and the multiplication result is latched by the second latch circuit 72. As a result, the time intervals of the internal timing signal z generated by the second counter circuit 74 are corrected in accordance with the deviation v3.
Specifically, when the estimated electric angle lags (v3<0), the time intervals of the internal timing signal z are corrected so as to become shorter, and, when the estimated electric angle leads (V3>0), the time intervals of the internal timing
signal z are corrected so as to become longer. As a result, the deviation at the timing of the next falling edge of the pulse signal g becomes smaller or zero. Consequently, it is possible to obtain the count signal v (corresponding to the estimated
electric angle) of the third counter circuit 75 which is synchronized with the pulse signal g indicative of the rotational position of the rotor.
[Calculation Process in the Command Generator 45]
The command generator 45 receives the count signal v, the internal timing signal z, and the current command signals jq and jd, and outputs the three-phase sinusoidal driving command signals ja, jb, and jc. The command generator 45 is configured
by a microcomputer and operates the calculation process which is shown in the flowchart of FIG. 6.
(1) Interruption start process 80:
In response to the generation of the internal timing signal z, the following interruption process is operated.
(2) Input process 81:
The count signal v and the current command signals jq and jd (two-phase current command signals) are input.
(3) Two-phase rotary/stationary transformation process 82:
An electric angle w (in degree) for transformation is calculated from the count signal v, which has undergone the phase matching.
where k0 is a proportional coefficient and v0 is an amount of the phase shift. The two-phase current command signals jq and jd are transformed by the coordinate transformation between the rotational coordinate and the stationary coordinate with
the electric angle w, thereby to produce transformed current command signals hq and hd, shown in the below-mentioned equation (1): ##EQU1##
The transformed current command signals hq and hd are two-phase signals which are different in phase from each other by an electric angle of 90 degree.
(4) Two-phase/three-phase transformation process 83:
The three-phase driving command signals ja, jb, and jc are obtained from the two-phase transformed current command signals jq and jd in accordance with the following equation (2): ##EQU2## where Jo is a proportional constant. The driving command
signals ja, jb, and jc obtained as a result of the two-phase/three-phase transformation process are three-phase signals which are different in phase from each other by an electric angle of 120 degree.
(5) Output process 84:
The driving command signals ja, jb, and jc are D/A-converted and then output.
(6) Termination process 85:
The interruption process is terminated.
The controller 46 supplies the two-phase current command signals jq and jd to the command generator 45. In the embodiment, a speed command signal r is compared with the measurement result signal f of the time interval measurement unit 42 and a
predetermined speed control calculation is performed so as to make the difference between the signals zero, thereby obtaining the current command signals jq and jd. As shown in the flowchart of FIG. 6, the amplitudes of the driving command signals ja,
jb, and jc of the command generator 45 are changed in proportion to the current command signals jq and jd.
The driving controller 22 compares the driving command signals ja, jb, and jc with current feedback signals da, db, and dc and conducts the PWM control (Pulse-Width Modulation control) on the driving transistors so that driving currents Ia, Ib,
and Ic corresponding to the driving command signals are supplied to the driving windings 20A, 20B, and 20C, respectively.
FIG. 7 shows the configuration of the driving controller 22, and the connection among the power supply unit 23 an | | |
