JP2016017953A - Motor speed detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a speed detection accuracy of an extremely low speed region of a motor without using an expensive rotary encoder.SOLUTION: A motor speed detection device includes: a rotary encoder 102 for detecting a rotational speed of a motor 101; and a motor speed control micro-computer 104 for measuring the time between pulse edges of a pulse signal of the rotary encoder 102 and including a speed detection part 105 for detecting the rotation speed of the motor from the time between the measured pulse edges. The speed detection part 105 measures time τ between the pulse edges, and detects the rotation speed of 1/a of the motor rotation speed as a motor rotation speed when (a) times (a is an actual number larger than 1) as large as the time τ between the pulse edges elapses after the motor rotation speed is detected and before the next pulse edge is obtained.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a motor speed detection device, and more particularly to a speed detection device used for motor speed control of an elevator using a rotary encoder.

  In motor speed control in an elevator, a function for accurately detecting a wide range of speeds from zero speed to a rated speed is required. In general, the optical rotary encoder that is used is very compatible with the speed detection accuracy for the motor rated speed (maximum speed) and the speed detection accuracy in the low speed range required for elevator speed control. Have difficulty. For this reason, a device has been devised to increase the accuracy by switching the speed detection mechanism between the high and low speed regions, such as dividing the encoder pulse. In an elevator, speed control in a very low speed range (immediately before arrival) is very important for the purpose of matching the floor level of the destination floor.

  In a motor speed detection device using a rotary encoder, the detection speed can be updated every time a pulse edge is detected, but the speed detection in the extremely low speed range where the pulse edge cannot be detected for a long time updates the detection speed for a long time. The detection accuracy is deteriorated. Therefore, for example, Japanese Patent Laid-Open No. 7-154990 (Patent Document 1) aims to prevent erroneous detection of speed data due to a delay in updating detection data of speed at low speed rotation even if an inexpensive and small encoder is used. A motor speed control device is disclosed that includes a cycle detection unit that measures a cycle of an encoder signal by measuring a clock, an arithmetic unit, a data holding unit, and a correction unit.

Japanese Patent Application Laid-Open No. 07-154990

  In Patent Document 1, when the encoder pulse is not input within the speed detection sampling period and the data holding means for holding the period measurement data is not updated, the correction means corrects the speed detection value using the sampling time. It is supposed to be. In this correction, if the latest sampled speed sampling data and at least one previous speed sampling data are the same, it is determined that the data is not updated by the encoder signal within the speed sampling period. Assuming that the motor is slower than the detected data or stopped, the reciprocal of the sampling time is corrected to be the current rotational speed of the motor.

  However, although the technique described in Patent Document 1 can prevent erroneous detection of speed data due to a delay in updating the detection data of the speed at the time of low-speed rotation, it is intended to increase the speed detection accuracy in the extremely low speed range. Not.

  Therefore, a problem to be solved by the present invention is to improve speed detection accuracy in a very low speed region of a motor without using an expensive rotary encoder.

  In order to solve the above problems, the present invention measures a time between pulse edges of a pulse signal of a pulse signal of the rotary encoder and a rotary encoder that detects a rotation speed of the motor, and the motor rotation speed is calculated from the measured time between the pulse edges. Speed detection means for detecting the time, the speed detection means measures the time between the pulse edges, and after the motor rotation speed is detected and before obtaining the next pulse edge, When a time a times (a is a real number larger than 1) between the pulse edges before obtaining the next pulse edge has elapsed, 1 / a rotation speed of the motor rotation speed is detected as the motor rotation speed. It is characterized by. Note that problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

  According to the present invention, it is possible to improve the speed detection accuracy in the extremely low speed region of the motor without using an expensive rotary encoder.

It is a block diagram which shows schematic structure of the motor speed control circuit which concerns on embodiment of this invention. It is a timing chart which shows the pulse signal of the rotary encoder in the motor very low speed range used as the premise of this invention. It is a flowchart which shows the detection procedure of the speed detection of the technique used as the premise of this invention. 4 is a timing chart corresponding to the flowchart shown in FIG. 3. It is a flowchart which shows the detection procedure of the speed detection which concerns on embodiment of this invention. 6 is a timing chart corresponding to the flowchart shown in FIG. 5.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a schematic configuration of an elevator motor speed control circuit according to an embodiment of the present invention.

  As shown in FIG. 1, an elevator motor speed control circuit 100 according to the present embodiment basically includes a motor 101, a rotary encoder 102, a motor speed control microcomputer 104, and an inverter 110.

  The motor 101 is a drive source for driving a main rope for raising and lowering the elevator and raising and lowering the elevator car. A rotary encoder 102 is attached to the motor 101, and a pulse signal 103 detected by the rotary encoder 102 is input to a speed detection unit 105 mounted on a motor speed control microcomputer 104. The speed detection unit 105 calculates the speed detection value 106 of the motor 101 and outputs it to the speed control unit 108. The speed control unit 108 outputs an inverter control signal 109 as an operation amount to the inverter 110 from the difference between the input speed detection value 106 and a separately input motor speed command value 107. The speed of the motor 101 (rotational speed) is controlled by a motor current 111 output from the inverter 110 based on the output inverter control signal 109. That is, the motor speed control according to the present embodiment is a feedback control in which the speed of the motor 101 is detected and the motor speed is controlled by the motor current 111 based on the detected speed detection value 106 and the motor speed command value 107. is there. In this embodiment, the rotary encoder 102 that detects the rotational speed of the motor and the motor speed control microcomputer 104 function as a motor speed detection device.

  In the motor speed control circuit 100 configured as described above, for example, the speed in the extremely low speed region during motor deceleration is detected as follows. Here, it is assumed that the number of pulses per rotation of the rotary encoder 102 is N and the duty is 50%.

FIG. 2 is a timing chart showing pulse signals of the rotary encoder 102 in the extremely low speed region during motor deceleration. 2, using the time tau ₁ between pulse edge from time T ₀ to time T _1, the motor average speed for a period of time T ₁ from the time T ₀ is
ω ₁ = 1 / 2Nτ ₁ (1)
Can be calculated as

  Here, the equation (1) is derived by setting the duty of the rotary encoder 102 to 50%, but the time between pulse edges is τ, the number of pulses per one rotation of the rotary encoder is N, and the duty is D%. Then, the motor average rotational speed ω at the time τ can be calculated as ω = D / 100Nτ.

When the speed detection unit 105 detects a pulse edge at time T ₁ , the elapsed time τ ₁ from the previous pulse edge detection time T ₀ is measured, so that the motor rotation speed is calculated based on the above equation (1). Can be detected. As a result, the motor speed detection value can be updated each time the pulse edge of the rotary encoder 102 is detected. In the example of FIG. 2, the speed detection value can be updated to ω ₁ at time T ₁ .

Note that the input capture function of the microcomputer can be used to measure the time between pulse edges. Further, when the state in which the τ _L pulse edge is not detected for a certain time continues, the speed detection value is set to zero.

  FIG. 3 is a flowchart showing a speed detection procedure corresponding to the output waveform of the rotary encoder pulse shown in FIG. 2, which is executed by software of a motor speed control microcomputer. FIG. 4 is a timing chart showing speed detection values based on the speed detection procedure of FIG. 3 when the output waveform of the rotary encoder pulse of FIG. 2 is obtained.

In FIG. 3, when the process is started and an input capture (interrupt) is generated (T ₁ ) due to the falling edge of the pulse signal of the rotary encoder 102 (step S1) (step S1), the timer counter counts from the previous input capture occurrence (T ₀ ). The elapsed time (τ ₁ ) is measured (step S2).

Then, the rotational speed ω ₁ (= 1 / 2Nτ ₁ ) of the motor 101 at time T ₁ is calculated by the above equation (1), the detected speed ω is updated to ω ₁ (step S3), and the timer count is cleared. (Step S4) Wait for the next interrupt to occur.

Here, since the detection speed (speed detection value) ω ₁ at time T ₁ is held until the next pulse edge rise (time T ₂ ), in the extremely low speed range where the pulse edge of the rotary encoder 102 cannot be detected for a long time, There is a possibility that the state in which the detection error has occurred continues for a long time.

Incidentally, it maintains 4, the detection rate at time _{T 2,} the (1 / 2Nτ ₂₎ and maintained until the time _{T 3,} the detection rate at time _{T 3} the (1 / 2τ ₃₎ to time _{T 4.} If no pulse edge is detected at time τ _L between time T ₃ and time T ₄ , the speed is determined to be zero, and the detection speed ω is set to 0 after time T ₄ .

  If controlled in this way, it takes time to update the detection speed in the extremely low speed region, and the speed detection accuracy deteriorates. In an elevator, this deterioration in accuracy causes a deterioration in riding comfort (car vibration) upon arrival at the target floor and a deterioration in accuracy of floor level alignment.

  Therefore, in this embodiment, speed detection is performed on the pulse signal of the rotary encoder 102 as shown in FIG. 2 by the speed detection procedure shown in the flowchart of FIG. Thereby, feedback control can be performed with the speed detection value as shown in the timing chart of FIG.

That is, in FIG. 5, when the input capture time T ₁ which detects the falling pulse edge (interrupt) is generated (step S11: YES), the time τ from the time T ₀ which detects the rising of the preceding pulse edge ₁ is measured by a timer counter, and an elapsed time τ (τ _{1 in} FIG. 6) from the previous input capture occurrence (time T ₀ ) is measured (step S12). Next, the rotational speed of the motor 101 is calculated from the equation (1), the detected speed ω is updated to this value ω ₁ (= ½Nτ ₁ ) (step S13), and the timer count is cleared (step S14).

Then, the compare match setting is updated so that an interrupt is generated after the time 2τ _{1 has} elapsed (step S15), and the next interrupt is generated.

Step S11 Input Capture (interrupt) if no generated by, after input capture, when the time 2.tau ₁ has elapsed (time _{T 1} '), compare match (interrupt) is generated (step S16). That is, when from the time T ₁ time (τ ₁ × 2) has elapsed, if not detected pulse edge to yet time T ₁ after the rotation speed of the motor 101 is a half or less of the detected speed Therefore, the motor detection speed is updated to (1 / 4Nτ ₁ ) (step S17). Thereafter, the compare match setting is canceled (step S18), and the next interrupt is generated.

On the other hand, when detecting a rising pulse edge at time _{T 2} (step S11: YES), using the time tau ₂ from time _{T 1} to time _{T 2,} the motor speed ω ₂ = (1 / 2Nτ ₂ )
And the detection speed (speed detection value ω) is updated (steps S12 and S13). Hereinafter, likewise, to be detected pulse edges until the time _{T 3,} at the time of the lapse of time 2.tau ₂ (time _{T 2} '), compare match (interrupt) is generated (step S16). That is, when from time T _2, the time (τ ₂ × ₂₎ has elapsed, if not detected pulse edge to yet time T _2, after the rotation speed of the motor 101 and 1/2 or less of the detected speed omega ₂ since it should become, the detected motor speed _{ω 2/2 (= 1 /} 4Nτ 2)
(Step S17). Thereafter, the compare match setting is canceled (step S18), and the next interrupt is generated.

If no pulse edge is detected at time τ _L between time T ₃ and time T ₄ , the speed is determined to be zero, and the detection speed (speed detection) ω is set to 0 after time T ₄ . Further, in the flowchart of FIG. 5, each process from the start to the end is repeated every time an interrupt occurs, so that no suffix is added to the time τ and the detection speed ω.

Note that the conveyor match function of the microcomputer can be used to measure the time lapse of (τ ₁ × 2) from time T ₁ . Even in a very low speed range where the pulse edge of the rotary encoder 102 cannot be detected for a long time by this speed detection method, the speed detection value 106 can be updated with the passage of time.

In the present embodiment, updating the detected motor speed (omega _1/2), the denominator in this case need not be "2", for example, if a real number larger than 1 "a" In this case, the motor detection speed is updated to (ω ₁ / a).

  As described above, according to this embodiment, after the time τ between pulse edges is measured by the speed detection unit 105 in the motor speed control microcomputer 104 and the motor rotation speed ω is detected, When a time a times (a is a real number larger than 1) elapses between pulse edges before obtaining the next pulse edge has elapsed before obtaining a pulse edge, the rotational speed is 1 / a of the motor rotational speed. Is detected as the motor rotation speed when the time elapses, the speed detection accuracy in the extremely low speed region of the motor can be improved without using an expensive rotary encoder.

  The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention, and all technical matters included in the technical idea described in the claims are included. The subject of the present invention. The above-described embodiments show preferred examples, but those skilled in the art can realize various alternatives, modifications, variations, and improvements from the contents disclosed in the present specification. These are included in the technical scope described in the appended claims.

DESCRIPTION OF SYMBOLS 100 Motor speed control circuit 101 Motor 102 Low-crease encoder 103 Pulse signal 104 Motor speed control microcomputer 105 Speed detection part 106 Motor detection part τ, τ ₁ , τ ₂ , τ ₃ , τ _L Time between pulse edges

Claims (2)

A rotary encoder that detects the rotational speed of the motor;
A speed detection means for measuring a time between pulse edges of the pulse signal of the rotary encoder, and detecting a motor rotation speed from the measured time between the pulse edges;
With
The speed detection means measures the time between the pulse edges, and after the motor rotation speed is detected, before obtaining the next pulse edge, before obtaining the next pulse edge, The motor speed detection device detects a rotation speed 1 / a of the motor rotation speed as a motor rotation speed when a time (a is a real number greater than 1) has elapsed. The motor speed detection device according to claim 1,
The motor speed detecting device, wherein the motor is a motor for driving a main rope for raising and lowering an elevator.