JPH0469088A - Method of detection of rotor position - Google Patents

Abstract

PURPOSE:To dispense with judgement of division overflow or the load of the overheads of other CPU's by always using either a sine wave signal or a cosine wave signal, which has a comparatively stable and large value, corresponding to the position of a rotor as a divisor. CONSTITUTION:A sine wave signal sintheta and a cosine wave signal costheta corresponding to the position of a rotor are sampled at the same time with an analogue-to-digital conversion circuit 10, converted into digital signals by time division, and transmitted to a polarity discrimination circuit 12, an absolute value comparison circuit 14, and a bus switching circuit 16. When for example the digital conversion data of sin theta is indicated as D{sintheta}, the polarity discrimination circuit 12 discriminates the polarity of D{sintheta} and D{costheta} when D{costheta}>0, transmits discrimination output g1, and, when D{sintheta}>0, transmits g2. When for example the absolute value of the digital conversion data of sintheta is indicated as D¦sintheta¦, the absolute value comparison circuit 14 transmits comparison output g3 when D¦costheta¦>D¦sin.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Industrial Application Field The present invention relates to a rotor position detection method for brushless DC motors, etc., and more specifically, the present invention relates to a rotor position detection method for brushless DC motors, etc. This invention relates to a method for detecting rotor position from signals at high speed and with high precision.

(B) Prior Art Brushless DC motors are widely used in devices that require precision, response characteristics, and reliability, such as robots, X-Y tables, integrated circuit manufacturing equipment, and magnetic disk drives.

In particular, the brushless DC motor disclosed in Japanese Patent Application Laid-Open No. 62-244265 is one of the most improved brushless DC motors today in terms of accuracy, response characteristics, and reliability.

First, the brushless DC motor disclosed in Japanese Unexamined Patent Publication No. 62-244265 will be explained with reference to FIGS. 5 and 6.

Figure 5 (A) shows the cross-sectional shape of the stator and its coil structure. It is shown with rectangular balls (34) arranged in a row and a coil (38) wound around each ball (34).

The stator balls (34
) is a circled number 1.2.4.5.7.8.9.10.11
and 13.14.15.16.17.18.19.2 as well as the first group of torque balls denoted by 12.
The torque balls are classified into three groups: a second group of torque balls designated by 1.22 and 24, and a sensor ball designated by 3.6.20 and 23.

The first group of torque balls are wound with polarity as shown, wired together and energized by the first phase power supplied to terminals (60) and (62). Similarly, the second group of torque balls are energized by second phase power supplied to terminals (64) and (66), respectively, to generate torque on the rotor. A feature of this motor is that a coil is connected to each adjacent pair of balls, and the coils are wound in opposite directions so that when the coil is energized, magnetic flux flows between the pairs of balls. In addition, a high frequency of about 100K82 is applied to the terminals (52) and (54) of the sensor balls wound with the polarities shown and bridge-connected, and the terminals (48 and 50) are connected to each other by π/2. A signal is generated that has a phase difference and changes in accordance with the rotor position.

FIG. 5(B) shows the cross-sectional shape of the rotor (40
) has a cylindrical core (42) and 18 rotor balls (44).
) and shaft (46). The rotor balls (44) are formed of high-magnetic permanent magnets such as samarium/cobalt alloy, and are arranged on the outer peripheral surface of the cylindrical core (42) by appropriate means so that their polarities are alternately different.
It is fixed. The ratio of the number of stator balls mentioned above to the number of rotor balls is 4:3 or 4:5.

FIG. 6 is a block diagram of a system for digital PTD control of a brushless DC motor having the above-described structure.

The torque balls of the first and second groups of the motor M are supplied with first and second phase power from amplifiers HA and H6, respectively, and the sensor ball terminals (52) (
54) is supplied with a high frequency signal of about 100KH2 from the oscillation circuit (122).

Line (124) from bridge connected sensor ball
(126), which have a phase difference of π/2 and change as the rotor rotates, are converted into vector signals by the synchronous detection circuit (120), and then
It is converted into a rotor position signal by the rotor position detection circuit (108). This rotor position signal may be an external reference signal input to a terminal (132) or a microprocessor (
100) internally outputs the reference signal and the input addition circuit (11
0), and the PID control circuit (112) (1140
116) to perform well-known digital PID control.

In addition to outputting the reference signal, the microprocessor (100) also outputs the PID control circuit (112) (114) (116).
For convenience of explanation, the rotor position detection circuit (1
0B), and also functions as a circuit shown independently as a monitor (102), an interface port (104).
).

Figure 7 shows a microprocessor (hereinafter referred to as CPU)
A block diagram of a conventional rotor position detection circuit (108) configured with the following is shown.

Bridge-connected sensor ball terminals (48) (50)
signals that have a phase difference of π/2 and change as the rotor rotates, i.e., cos θ and sin
θ is simultaneously sampled by the A/D conversion circuit (80), and is usually time-divisionally A/D converted and sent to the CPU (80).
2) is entered into a predetermined human-powered boat.

Digital data obtained by A/D converting sin θ is converted to D(s
in θ), the CPU (82) operates based on the control program and division program written in the interpreter (84), and first calculates D(sin θ)/D(c) at a predetermined timing.

This D(
Since the value range of tanθ) is large, the data table (86
), perform logarithmic compression with reference to p(tanθ)θ table (88) using this logarithmically compressed data as an address.
is accessed to obtain O, which is output as a digital rotor position signal from a predetermined eight ports.

The brushless DC motor described above has the advantage that highly accurate rotor position detection is possible because the magnetic balance is essentially good and the position detection signal is not modulated by the rotor rotational speed.

Furthermore, even if the position detection signal is modulated by the rotational speed of the rotor, it has the advantage of being canceled out by division.

(c) Problems to be Solved by the Invention However, the above-mentioned eight rotor position detection circuits can be
When configured with PU, for example, D(sin θ)/
When calculating D(cos θ)=D(tan θ), it is necessary to always judge whether there is a division overflow, or because of other CPU overhead problems, the calculation cannot be performed at the expected speed.

In addition, data configured by ROM or RAM
It also has the disadvantage of increasing the size of the table.

Therefore, the problem to be solved by the present invention is to provide a method that allows high-speed rotor position detection using a general-purpose CPU that does not require division overflow determination or other CPU overhead. Another object of the present invention is to provide a method that allows highly accurate rotor position detection despite using a small-scale data table.

(d) Means for Solving the Problems The present invention has been made in view of the above problems, and is designed to convert sine wave signals or cosine wave signals corresponding to the rotor position into
Divide into four time and angle regions at π/2 intervals starting from π/4, divide the sine wave signal amplitude by the cosine signal amplitude in the first and third regions, and divide the sine wave signal amplitude by the cosine wave signal amplitude in the first and third regions. By dividing the cosine wave signal amplitude by the sine wave signal amplitude, the burden of determining division overflow or other CPU overhead burden that exists in the prior art is reduced.

(E) By always using a signal that takes a relatively constant and large value among the sine wave signal or cosine wave signal corresponding to the rotor position as the divisor, there is no need to judge whether there is a division overflow or other CPU overhead is incurred. It becomes possible to reduce the burden on This division also provides a very good approximation of the rotor position, resulting in a small correction data table. Furthermore, since the division result is always a value smaller than 1, the rotor position pressure detection accuracy is improved.

(F) Embodiment A first embodiment of the present invention will be described with reference to FIGS. 1 and 2.

Figure 1 is a block diagram of eight rotor position detection circuits realized by the CPU.
14), bus switching circuit (16), CPU (20), RO
Interpreter (22) written in M and correction data table (24) written in ROM or RAM
It is indicated by.

The sine wave signal sin θ and cosine wave signal cos θ (in the present invention, the ratio thereof provides rotor position information, so the explanation will be made using standardized signals) corresponding to the rotor position are as shown in FIG. A/
The signals are simultaneously sampled by the D conversion circuit (10), A/D converted in a time division manner, and outputted to the polarity determination circuit (12), the absolute value comparison circuit (14), and the bus switching circuit (16).

When digital conversion data of sin θ is expressed as D(sin θ), the polarity discrimination circuit (12)
) and D(cosθ), respectively, and determine the polarity of D(
Discrimination output g1.1) (sin θ) when cos θ)>0
>0, outputs g2.

Also, the absolute value of the digital conversion data of sin θ is D1
When expressed as sinθ1, the absolute value comparison circuit (14
) outputs a comparison output g3 when [)lcosθl>I]sinθ1.

Therefore, referring to FIG. 2, the rotor position θ is determined by the discrimination output g+g2 and the comparison output g3, so that: ■ Dlcosθ1>Dlsinθ1 and D(cos
θ) > O (g, = 1, g3 = 1) region I, ■ Dl
cosθ1≦DIS1nθ1, D (sinθ)
>o (g2=1, g3=0) area 11, ■ D1
coSθl>I]sinθ1, and D(cosθ)<0
Area I11 of (gl”0, g3=1), ■ D l c
osθ1≦Dlsinθ1, and D(sinθ)<0
(g2=o, g3=o) The area is divided into four areas (3).

The bus switching circuit (16) is connected to the comparison output g3-1 and CP.
U (20) input capo-)p+ [)(cosθ),
Input capo) D (sin θ) into p2 and compare output g
When 3=0, D to the input port p of CPU (20)
(sin θ) and D(co's θ) are input to the input port p2.

The c p U (20) processes the data latched to the input ports p3 and p2 at a predetermined timing based on the operating procedure program and division program written in the interpreter (22) without determining the divisor or dividend. Automatically divide. Then, the discrimination output g1, g
2 and comparison output g3, the division result is further given as ■ 32xD (s in θ)/D(cos θ) (g+
= 1, g3= t), ■ 64-32xD (cosθ)/D(sinθ)(
g2=1, g+=0), ■ 128+32xD (s inθ)/D(cosθ
)(g+=o, g3=1), ■ 192-32xD (s in θ)/D(cos θ
) (gz=o, g3=0) to output a rotor position signal with 1-byte accuracy.

The first feature of the present invention is that the range of the divisor D (sin θ) or D (cos θ) is extremely limited as shown by α in FIG. 2, and the range of the dividend is also similarly shown by β. The point is that it is limited to. Therefore, in the present invention, in which it is guaranteed that the result of division is always less than or equal to 1, there is no need for the interpreter (22) to determine whether there is a division overflow, and high-speed calculation is possible.

The second feature of the present invention is that each of the above operations, including constant multiplication, includes only operations that can be executed at sufficient speed even by a general-purpose CPU.

Furthermore, the third feature of the present invention is that the rotor position signal θ is strictly j an-' [D (s in θ)/D(c).

Sθ)], but the error between this exact calculation result and the rotor position signal θ obtained by the above calculation is only 10% at most.

According to the third feature of the present invention, the correction data and
RAM or ROM shown as table (24)
It becomes possible to detect the rotor position with high precision without increasing the scale of the rotor.

In the above description of this embodiment, for convenience of explanation, the polarity discrimination circuit (12), absolute value comparison circuit (14), bus switching circuit (16), etc. were made into independent hardware circuits. It is clear that the functions of can be replaced by software processing.

Next, as a modification of the first embodiment described above, an example in which the rotor position θ is divided into four regions according to time intervals will be described with reference to FIG.

This rotor position detection circuit includes an A/D conversion circuit (10), -
Number output circuit (11), flag generation circuit (13), bus switching circuit (16), CPU (20), interpreter (22) written in ROM, and ROM or RAM
It consists of the correction data table (24) described in .

The coincidence detection circuit (11) has D(sinθ) and D(CO
Sθ) are both positive and when the values match, a pulse T is output. Note that D(s'jnθ) and D(co
A coincidence detection circuit that outputs a pulse T when the signals sθ) simply coincide with each other can also be used by slightly modifying the flag generation circuit (13), which will be described later.

The flag generating circuit (13) detects the time interval of this pulse T, and at a time interval of 1/2 of the time interval, a first flag f1 as shown in FIG. The flag f2 is output. Therefore, the sine wave signal or cosine wave signal corresponding to the rotor position is divided by this 2-bit flag into four time and angular regions I to 2 at intervals of π/2 starting from -π/4.

Referring again to FIG. 2, in the first region I, which is the second flag f20, and the third region 111, the second flag f20 is
The bus switching circuit (16) controlled by D(sin
θ) and D(cos θ) are CPU U (20
) is output to input ports p3 and p2. On the contrary,
The second area 11 and the fourth area where the second flag f2=1
In region (2), the bus switching circuit (16) outputs D (sin θ) and D (cos θ) to the input ports p1 and p2 of c P U (20), respectively.

Based on the operation procedure program and division program written in the interpreter (22), the CPU (20) automatically processes the data latched in the manual boats p1 and p2 at a predetermined timing without determining the divisor or dividend. Divide by. Therefore, CPU (20) performs [)(sin θ)/D(cos θ)=D(
tanθ), and the second flag f2-1 is calculated.
In the region 1 ■ and the fourth region ■])(cos θ)/
Calculate D(sin θ)=D(coto).

Next, a second embodiment of the present invention will be described with reference to FIG.

In the previous embodiment, division was performed by software, but this embodiment is characterized in that division is performed by a table lookup method.

In other words, although division using the table lookup method allows for high-speed calculations, it has the disadvantage that the scale of the data table increases when the range of the divisor and dividend is large; however, as explained earlier, According to the invention, the divisor,
The table lookup method is particularly effective because the range of the dividend is relatively limited.

This embodiment shows an A/D conversion circuit (10), a polarity discrimination circuit (12), an absolute value comparison circuit (14), and a bus switching circuit (
16), a CPU (20), an interpreter (22) written in the ROM, and a correction data table (24) and a division table (26) written in the ROM or RAM.

The A/D conversion circuit (10), polarity discrimination circuit (12), absolute value comparison circuit (14), and bus switching circuit (16) are the same as the circuits used in the explanation of the previous embodiment, so their explanation will be omitted. Then, in this embodiment, when digital data D (sin θ) and D (cos θ) are given to the input ports p1 and p2 of the CPU (20), the division table (26) is accessed using them as address data.
The quotient is immediately obtained from the division table (26).

As is clear from FIG. 2, the noteworthy features of the present invention are as follows:
The point is that the sine wave signal sin θ and the cosine wave signal cos θ in the first region (3) and the second region II are symmetrical with respect to the rotor position 31. This allows the division table (2
6), it is sufficient to prepare only one area, and the division table (26) can be made extremely small.

(1) Effects of the Invention As described above, according to the present invention, (1) A sine wave signal or a cosine wave signal corresponding to the rotor position is transmitted at four times of π/2 intervals starting from −π/4 of the sine wave signal or cosine wave signal. Furthermore, since the signal is divided into angular regions, the rotor position can be accurately approximated by dividing the amplitudes of the sine wave signal and the cosine wave signal. As a result, calculation of arc tangent becomes unnecessary, and rotor position/lateral ratio can be calculated at high speed.

(2) Because it is divided into the first to fourth regions by comparing the absolute values of the amplitudes of the sine wave signal and the cosine wave signal and by determining the polarity of the amplitudes of the sine wave signal and the cosine wave signal, a relatively small scale The position can be detected by software or hardware.

(3) Since the range of the sine wave signal and cosine wave signal serving as the divisor and dividend is limited, the rotor position resolution can be improved. Further, it is easy to apply the table lookup method to the division, and the rotor position can be detected even faster.

(4) Since the rotor position is detected from the ratio of the amplitudes of the sine wave signal and the cosine wave signal, highly accurate rotor position detection is possible even from the velocity modulated sine wave signal and cosine wave signal.

(5) Since the divisor does not become zero, there is no need to judge whether there is a division overflow, and high-speed rotor position detection becomes possible, and the division result does not diverge, so rotor position resolution can be improved.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a rotor position detection circuit explaining the first embodiment of the present invention, Fig. 2 is an explanatory diagram of the operation of the implementation port, Fig. 3 is a block diagram of a modified example, and Fig. 4 is a block diagram of the rotor position detection circuit according to the present invention. Block diagram of 8 rotor position detection circuits explaining the second embodiment of
Figures (A) and (B) are cross-sectional views of the stator and rotor of a brushless polyphase DC motor, respectively. Figure 6 is a block diagram of a control circuit for a brushless polyphase DC motor. Figure 7 is a conventional control circuit using a microprocessor. A block diagram of a rotor position detection circuit. (10)--A/D conversion circuit, (12)--Polarity discrimination circuit, (14)--Absolute value comparison circuit, (16)
-Bus switching circuit, (20)...CPU, (22)...
...Interpreter, (24)--Correction data table. Applicant Oriental Motor Co., Ltd.

Claims (6)

[Claims] (1) Divide the sine wave signal or cosine wave signal corresponding to the rotor position into four time and angle regions at π/2 intervals starting at -π/4, and in the first and third regions, the sine wave signal or cosine wave signal A rotor position detection method comprising dividing a signal amplitude by a cosine wave signal amplitude, and dividing the cosine wave signal amplitude by a sine wave signal amplitude in the second and fourth regions. (2) The first to fourth regions are divided by comparing the absolute values of the amplitudes of the sine wave signal and the cosine wave signal and determining the polarity of the amplitudes of the sine wave signal and the cosine wave signal. 1. The rotor position detection method described in 1. (3) The rotor position detection method according to claim 1, wherein the time interval of each region is 1/2 or 1/4 of the time interval in which the amplitudes of the sine wave signal and the cosine wave signal match. (4) The rotor position detection method according to claim 1, wherein the division result is corrected by a table lookup method to obtain rotor position data. (5) The rotor position detection method according to claim 1, wherein the division of the sine wave signal amplitude and the cosine wave signal amplitude is performed by a table lookup method. (6) The sign of the division result is determined for each of the four regions,
2. The rotor position detection method according to claim 1, further comprising determining an initial value.