JPH08313548A - Device for detecting speed of motor - Google Patents

Abstract

PURPOSE: To provide a speed detecting device the circuit of which can be reduced in size and which can eliminate the error of motor speed calculated values even when the data of a counter and register are updated while the data are fetched. CONSTITUTION: A microcomputer 1 is incorporated with a first counter 2, second counter 3, and register 4 which keeps the output value of the second counter 3. A pulse generator 5 generates a pulse train of a frequency proportional to the rotating speed of a motor 6. The first counter 2 counts the output pulse mpls of the generator 5 and the second counter 3 counts the internal clock of the microcomputer 1. The count value of the second counter 3 is latched to the register 4 at the leading and trailing edges of the output pulse mpls of the pulse generator 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor speed detecting device for detecting a motor speed by a signal from a pulse generator attached to a motor, and is suitable for, for example, an electric vehicle.

[0002]

2. Description of the Related Art In order to detect the rotation speed of a rotor of a motor, a pulse generator that outputs a plurality of pulse signals for one rotation is often used. Japanese Patent Publication No. 6-1279, for example, is a device for detecting the speed using this pulse generator. This mainly consists of a counter that counts the number of pulses of the pulse generator, a counter that measures time, and a latch circuit that latches the value of the counter that measures time in synchronization with the pulses of the pulse generator. The value of a counter that counts the number of pulses and the value of a latch circuit are taken in every cycle to calculate the motor speed.

[0003]

In this system, the speed detecting circuit is constructed as a circuit separate from the microcomputer. Therefore, in order to incorporate the data of the counter for counting the number of pulses and the latch circuit into the microcomputer, the microcomputer is used. Since the data bus and the like are externally output and connected to the speed detection circuit, there is a problem that the entire circuit cannot be downsized. In addition, when the data is updated while the data of the counter that counts the number of pulses and the latch circuit is being fetched from the microcomputer, the number of pulses of the counter that counts the number of pulses and the data of the time of the latch circuit are at the same time point. However, there is a problem that an error occurs in the calculated value of the motor speed.

[0004]

A pulse generator for outputting a pulse each time the motor rotates, a first counter for counting the number of pulses from the pulse generator, and a clock pulse for measuring time A microcomputer having a second counter for counting, a register for latching the output value of the second counter in synchronization with a pulse from the pulse generator, and a speed calculating means for calculating the speed of the motor in the microcomputer. And the speed calculation means first captures and stores one of the output value of the first counter and the output value of the register for each predetermined sampling time, and then stores the other value. A value is captured and stored, and finally the value that was captured first is captured again and stored, and the value that is captured and stored first and the last When the fetched and stored values are the same, the fetched and stored output value of the first counter is the motor position data for the current sampling, and the fetched and stored output value of the register is the current sampling time data. When the value captured and stored at the beginning is different from the value captured and stored at the end, the other value is captured and stored again, and the output value of the first counter captured and stored a second time is sampled this time. Motor position data, the output value of the register captured and stored a second time is used as the time data of this sampling, and the motor speed is calculated from the motor position data and the time data of the current sampling and previous samplings. Calculate

[0005]

The pulse generator generates a pulse each time the motor rotates. The first counter counts the number of pulses from the pulse generator. The second counter counts clock pulses for measuring time. The register latches the value of the second counter in synchronization with the pulse of the pulse generator.
The microcomputer is the first every fixed sampling time.
The values of the counter and the register are alternately fetched, and the values of the first counter and the register at the same time point are determined even when the timings of fetching the value and updating the value of the register overlap. The rotation speed of the motor is calculated from the data.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. The microcomputer 1 has a first counter 2 and a second counter 3 and a register 4 for storing the output value of the second counter. Further, the microcomputer 1 fetches the output values of the first counter 2 and the second counter 3 and the register 4 to perform the speed calculation processing of the motor, and controls the speed or torque of the motor based on the speed command or the torque command. CPU7, ROM8, which performs the processing
A timer 10 for generating a signal for operating the RAM 9 and the drive circuit 11 is built in. The drive circuit 11 is composed of a power converter composed of a power semiconductor and its control circuit, and rotates the motor 6 in response to a signal from the microcomputer 1. The pulse generator 5 generates a pulse train having a frequency proportional to the rotation speed of the motor 6. The first counter 2 counts the output pulse mpls from the pulse generator 5. The second counter 3 is the microcomputer 1
Count the internal clock of. The frequency of this internal clock is sufficiently higher than the frequency of the pulse output from the pulse generator 5. Alternatively, a clock pulse of a constant cycle may be input from the outside to measure. The count value of the second counter 3 is latched in the register 4 at the fall and rise of the output pulse mpls from the pulse generator 5.

FIG. 2 shows the waveform of the output pulse mpls and the timing of changes in the first counter 2, the second counter 3 and the register 4. The value of the first counter 2 is incremented in synchronization with the rising and falling edges of the output pulse mpls. The value of the second counter 3 is incremented in synchronization with the internal clock having a constant cycle. This second counter 3
Is latched in the register 4 in synchronization with the rising and falling edges of the output pulse mpls.

FIG. 3 shows the processing performed by the microcomputer 1 at regular sampling times. The motor position is read from the first counter 2 and the time when the motor position changes is read from the register 4. First of all
The value of the counter 2 of 1 is fetched into the variable motor1 (step 301). Next, the value of the register 4 is loaded into the variable time1 (step 302). Further, the value of the first counter 2 is loaded into the variable motor2 (step 303). Here, it is determined whether or not the values of the variable motor1 and the variable motor2 are the same (step 304). If they are the same,
The value of the variable motor1 is substituted for the variable motor indicating the motor position (step 305), and the value of the variable time1 is substituted for the variable time indicating the time when the motor position changes (step 306). As a result of the determination in step 304, the variable motor
When the value of 1 is different from the value of the variable motor2, the value of the register 4 is fetched again and is substituted into the variable time (step 307), and the value of the variable motor2 is substituted into the variable motor (step 308).

FIG. 4 and FIG. 5 show the timing of changing the first counter and the register and the timing of reading data from the first counter 2 and the register 4, which is performed at every constant sampling time shown in FIG. It shows the relationship. In FIG. 4, a series of processes from step 301 to step 303 does not coincide with the timing of changing the first counter 2 and the register 4. At this time, the values of the variable motor1 and the variable motor2 are the same. FIG. 5 shows a case where the series of processing from step 301 to step 303 coincides with the timing of changing the first counter and the register. At this time, the values of the variable motor1 and the variable motor2 are different. The value of the variable time1 becomes the value synchronized with the variable motor1 in the upper case of FIG. 5, but becomes the value synchronized with the variable motor2 in the lower case of FIG. 5, and the upper state and the lower state of FIG. With the variable time
It is impossible to determine which one the value of 1 corresponds to. Therefore, the processing step 307 for fetching the value of the register 4 is performed again. FIG. 6 shows a process performed by the microcomputer 1 at constant sampling time intervals. The motor position is read from the first counter and the time when the motor position changes is read from the register. The processing here is different from the processing shown in FIG. 3 in the order of the processing of fetching the data of the first counter 2 and the register 4. First, the value of register 4 is loaded into variable time1 (step 601). Next, the first counter 2
The value of is taken into the variable motor1 (step 602). Further, the value of the register 4 is fetched into the variable time2 (step 603). Here, it is determined whether the values of the variable time1 and the variable time2 are the same (step 604). If they are the same, the variable motor indicating the motor position is set to the variable moto.
The value of r1 is substituted (step 605), and the value of the variable time1 is substituted for the variable time indicating the time when the motor position changes (step 606). As a result of the determination in step 604, when the values of the variable time1 and the variable time2 are different, the value of the first counter 2 is read again and substituted into the variable motor (step 607), and the value of the variable time2 is substituted into the variable time ( Step 608). This process makes register 4
4 and the value of the first counter 2 are read alternately.
And for the same reason as shown in FIG.

The process of FIG. 7 is a process performed by the microcomputer 1 at regular sampling intervals, and is for calculating the motor speed. This process is performed by the process shown in FIG. 3 or FIG.
It shall be performed continuously after the value of the variable time, which indicates the time when r and the motor position change, is fixed.

First, the variable time and the variable prereg indicating the previous value of the register 4 are compared to determine whether the value of the register 4 has been updated (step 701).

When the value of the register 4 is updated, the deviation between the variable time and the variable pretime indicating the time determined by the previous sampling is calculated and substituted into the variable dtime (step 702). The value of the variable dtime is added to the value of the variable stime integrated up to the previous sampling (step 703). Variable motor and variable pr indicating the previous motor position
The difference from the emotor is calculated and assigned to the variable dmotor (step 704). The motor speed omegam changes the variable dmotor to the variable st
The value divided by ime is multiplied by the coefficient k1 to obtain (step 7).
05). The value of the variable time is substituted for the variable prereg (step 706). Variable prestim indicating the value obtained by integrating the previous time
The value of the variable stime is substituted for e (step 707). Substitute the value of the variable time for the variable pretime (step 70)
8). Variable motor to the variable premotor that indicates the previous motor position
Is substituted (step 709). The value of the variable stime is cleared to 0 (step 710). The value of the variable count is cleared to 0 (step 711).

When the value of the register 4 is not updated in step 701, it is determined whether or not the variable count indicating the number of times the register 4 is not continuously updated exceeds the maximum value MAX (step 712). This is the variable stim that integrates time
This is for the purpose of preventing the overflow of the value of e, and so that the value of the variable omegam becomes 0 even if the register 4 is updated in the next sampling and the motor speed is calculated (step 705). Determine the variable type of the variable stime (if the variable time is a short variable, the variable stime
Is a long variable, etc.).

If the variable count does not exceed the maximum value MAX, the value of the second counter 3 for measuring the time is read and substituted into the variable cnt2 (step 713). Variable cnt
2 and a variable pre that indicates the time determined by the previous sampling
The deviation from time is calculated and substituted for the variable dtime (step 714). Variables integrated up to the last sampling
The value of the variable dtime is added to the value of stime (step 71
5). Variable stime and variable pres indicating the previous integrated time
When it is compared with time (step 716) and the value of the variable stime is large, the motor speed omegam calculates as a value obtained by dividing the coefficient k1 by the value of the variable stime (step 71).
7). The value of the variable cnt2 is substituted for the variable pretime (step 718). The value of the variable count is incremented (step 719). In the processing here, when the value of the register 4 is not updated, the value of the second counter 3 is directly fetched, so that the motor speed can be detected without problems even if the second counter 3 overflows.

When the variable count exceeds the maximum value MAX, the value of the motor speed omegam is set to 0 (step 72).
0).

FIG. 8 shows the changes in the first counter 2, the second counter 3, and the register 4 and the calculation timing of the speed detection process. The speed detection process is repeated many times before the register 4 changes. This is the case in the low speed region. The first counter that counts pulses is incremented at time A, time B, and time C. In the speed detection process between time B and time C, since the register 4 is updated at the sampling time immediately after time B, the motor speed is calculated in step 705 of FIG. 7, and the time difference between time A and time B is calculated. Is saved as the variable prestime. While the register 4 is not updated at the sampling point of the speed detection process thereafter, the time from time B to the sampling point is calculated as the variable stime. Variable prestime and variable st
By comparing the values of ime, the value of the variable prestime is
When it is larger than the value of e, speed calculation is not performed and time B
The value of the motor speed omegam calculated at the time of sampling immediately after is held. When the value of the variable stime becomes larger than the value of the variable prestime, the motor speed omegam is calculated by the formula shown in step 717 of FIG. 7. In this case, the larger the value of the variable stime at the time of sampling,
Although the value of the motor speed omegam becomes smaller, the value of the motor speed omegam calculated at the time of sampling immediately after the time B and the value of the motor speed omegam calculated at the time of sampling of the speed detection processing immediately after the time C do not become discontinuous. Has become.

Another embodiment of the present invention will be described with reference to FIG. The pulse generator 905 generates a pulse train having a frequency proportional to the rotation speed of the motor 906. First counter 902
Counts the output pulse mpls from the pulse generator 905. The second counter 903 is a clock pulse generator 90.
The clock pulses generated by 5 are counted. The frequency of this internal clock is sufficiently higher than the frequency of the pulse output from the pulse generator 905. Pulse generator 90
The count value of the second counter 903 is latched in the latch circuit 904 at the falling edge and the rising edge of the output pulse mpls from 5. The microcomputer 901 takes in the data of the first counter 902 and the latch circuit 904 and calculates the motor speed. Further, the microcomputer 90
Reference numeral 1 controls the speed or torque of the motor based on the speed command or the torque command, and outputs a signal for operating the drive circuit 907. The drive circuit 907 includes a power converter formed of a power semiconductor and a control circuit for the power converter, and rotates the motor 906 in response to a signal from the microcomputer 901. Output pulse mpls waveform and first
Counter 902, second counter 903, register 9
The change timing of 04 is the same as that shown in FIG. In the circuit configuration shown in FIG. 9 as well, the same flow chart as that shown in FIG. 3 or 6 is executed by the microcomputer 901, so that when the data of the first counter 902 and the latch circuit 904 is taken in, the motor Even when the pulse is input and the data is updated, the position of the motor and the time corresponding thereto can be captured. Further, the motor speed can be calculated according to a flowchart similar to that shown in FIG.

Another embodiment of the present invention will be described with reference to FIG. The microcomputer 1001 has a first counter 1
002 and a second counter 1003, a first register 1004 for storing the output value of the first counter and a second register 1005 for storing the output value of the second counter are incorporated. Further, the microcomputer 1001
Is the first counter 1002 and the second counter 100.
3 and the output values of the first register 1004 and the second register 1005 are fetched, the motor speed calculation processing is performed, and the processing of controlling the motor speed or torque based on the speed command or torque command is executed. CPU1008, ROM1009, RAM1010,
A timer 1011 that generates a signal for operating the driver circuit 1012 is incorporated. The drive circuit 1012 is composed of a power converter composed of a power semiconductor and a control circuit thereof, and rotates a motor 1007 in response to a signal from the microcomputer 1001. Pulse generator
1006 generates a two-phase signal pulse train having a frequency proportional to the rotation speed of the motor 1007. The first counter 1002 counts the two-phase output pulse from the pulse generator 1006. The second counter 1003 is the microcomputer 1
The internal clock of 001 is counted. The frequency of this internal clock is sufficiently higher than the frequency of the pulse output from the pulse generator 1006. Alternatively, a clock pulse of a constant cycle may be input from the outside to measure. The count value of the first counter 1002 is latched in the first register 1004 at the rising or falling of the B phase of the two-phase output pulse from the pulse generator 1006, and the count value of the second counter 1003 is stored in the second register. Latch to 1005. Here, the same applies when the A-phase signal is used instead of the B-phase. With the counter and register configuration shown in FIG.
When the first counter 1002 counts two-phase signals, the two-phase signals A-phase signal and B-signal are generated to generate a latch signal for transferring the value of the second counter 1003 indicating time to the second register 1005. A separate circuit for taking the EXOR of the phase signals is required. In order not to use another circuit, another register in the microcomputer is used, and the first counter is used at the same timing as when the value of the second counter 1003 is transferred.
It is necessary to transfer the value of the counter 1002 of 1 to the first register 1004.

FIG. 11 shows a two-phase pulse signal, a first counter 1002, a second counter 1003, and a first register 1.
004, the operation timing of the second register 1005 is shown. The first counter 1002 counts pulses of a two-phase signal, and the second counter 1002 counts clock pulses indicating time. Here, only the falling edge of the B-phase signal is used as the latch signal, and the second counter 1
The value of 003 is transferred to the second register 1005, and the value of the first counter 1002 is transferred to the first register 1004. In the case of the configuration shown in FIG. 1, the flowchart shown in FIG. 3 or 6 was executed to read the motor position and the time corresponding thereto, but in the case of the configuration shown in FIG. 1st in the flowchart shown
Steps 301 and 303 for reading the counter value of
Alternatively, it is necessary to change the processing of steps 602 and 607 to the processing of fetching the value of the first register 1004.
The flow chart for calculating the velocity shown in FIG. 7 can be used as it is.

[0020]

According to the present invention, a data bus or the like can be transferred from the microcomputer to the outside by using a counter and a register built in the microcomputer instead of separately providing a circuit for detecting the motor speed. The circuit can be miniaturized because there is no need to take it out. Further, even if the data is updated while the data of the counter and the register is being fetched, the values of the counter and the register at the same point in time can be determined by reading the data twice, eliminating the error in the calculated motor speed value. be able to.

[Brief description of drawings]

FIG. 1 is a diagram showing a speed detection device according to an embodiment of the present invention.

FIG. 2 is a diagram showing operation timings of a motor pulse, a counter, and a register.

FIG. 3 is a flowchart of a process of loading a counter and a register.

FIG. 4 is a diagram showing a timing of speed detection processing and a timing of updating a register.

FIG. 5 is a diagram showing a timing of speed detection processing and a timing of updating a register.

FIG. 6 is a flowchart of a process of loading a counter and a register.

FIG. 7 is a flowchart of a motor speed calculation process.

FIG. 8 is a motor speed detection process in a low speed region.

FIG. 9 is a diagram showing a speed detection device according to an embodiment of the present invention.

FIG. 10 is a diagram showing a speed detection device according to an embodiment of the present invention.

FIG. 11 is a diagram showing operation timings of a motor pulse, a counter, and a register.

[Explanation of symbols]

1 ... Microcomputer, 2 ... First counter, 3 ...
Second counter, 4 ... Register, 5 ... Pulse generator, 6
…motor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Eiichi Otsu 2520 Takaba, Hitachinaka City, Ibaraki Prefecture Hitachi Ltd. Automotive Equipment Division, Hitachi Ltd.

Claims (6)

[Claims] 1. A pulse generator that outputs a pulse each time the motor rotates, a first counter that counts the number of pulses from the pulse generator, and a second counter that counts clock pulses for measuring time. Of the counter, a microcomputer including a register for latching the output value of the second counter in synchronization with the pulse from the pulse generator, and a speed calculation means for calculating the speed of the motor in the microcomputer. A motor speed detection device characterized by the above. 2. The speed calculation means according to claim 1,
Of the output value of the first counter and the output value of the register for each predetermined sampling time, either one of the values is first captured and stored, then the other value is captured and stored, and finally the above-mentioned. The first captured value is again captured and stored, and when the first captured and stored value is the same as the last captured and stored value, the captured and stored output value of the first counter is The sampling motor position data is used, and the output value of the register captured and stored is the time data of the current sampling, and when the value captured and stored at the beginning is different from the value captured and stored at the end, the other value is stored. Is again captured and stored, and the output value of the first counter that is captured and stored a second time is used as the motor position data for this sampling. The output value of the register that was captured and stored a second time is used as the time data for the current sampling, and the motor speed is calculated from the motor position data and the time data for the current sampling and previous samplings. Motor speed detection device characterized by. 3. A pulse generator that outputs a pulse each time the motor rotates, a first counter that counts the number of pulses from the pulse generator, and a clock pulse generator that outputs a clock pulse of a constant frequency. A second counter that counts the clock pulses; a latch circuit that holds an output value of the second counter in synchronization with a pulse from the pulse generator; an output value of the first counter and the latch A motor speed detecting device comprising: a microcomputer capable of fetching an output value of a circuit; and a speed calculating means for calculating a speed of a motor in the microcomputer. 4. The speed calculation means according to claim 3,
Of the output value of the first counter and the output value of the latch circuit for each predetermined sampling time, either one of the values is first captured and stored, then the other value is captured and stored, and finally The first captured value is again captured and stored, and when the first captured and stored value is the same as the last captured and stored value, the captured and stored output value of the first counter is The sampling motor position data, the captured and stored output value of the latch circuit is the current sampling time data, and when the first captured and stored value is different from the last captured and stored value, the other Value of the first counter is stored again and stored, and the output value of the first counter stored and stored a second time is used as the motor position for this sampling. As the data, the output value of the latch circuit that is captured and stored the second time is used as the time data of the current sampling, and the motor speed is calculated from the motor position data and the time data of the current sampling and the sampling before that. A motor speed detection device characterized by the above. 5. A pulse generator that outputs a pulse each time the motor rotates, a first counter that counts the number of pulses from the pulse generator, and a second counter that counts clock pulses for measuring time. Counter, a first register that latches the output value of the first counter in synchronization with the pulse from the pulse generator, and an output value of the second counter in synchronization with the pulse from the pulse generator. A motor speed detecting device comprising: a microcomputer having a second register for latching; and speed calculating means for calculating the speed of a motor in the microcomputer. 6. The speed detecting means according to claim 5,
Of the output value of the first register and the output value of the second register for each predetermined sampling time, either one of the values is first captured and stored, and then the other value is captured and stored, Finally, the first captured value is captured again and stored, and when the value captured and stored at the beginning and the value captured and stored at the end are the same, the output value of the first register captured and stored. Is the motor position data for the current sampling, and the output value of the second register that has been captured and stored is the time data for the current sampling, and the first captured and stored value is different from the last captured and stored value. Sometimes, the other value is captured and stored again, and the output value of the first register that is captured and stored a second time is stored in the current sampling value. Over data and the position data, the second stored incorporates a second time
The motor speed detecting device is characterized in that the output value of the register is used as the time data of the current sampling, and the speed of the motor is calculated from the motor position data and the time data of the current sampling and the sampling before that.