JPH07318575A - Method and apparatus for detecting rotational speed and rotational speed control method - Google Patents

Abstract

PURPOSE:To obtain method and apparatus for attaining detection amounts continuously with high accuracy through an intermittent measuring method in the detection of the rotational speed of a motor. CONSTITUTION:The rotational speed detector comprises a rotational pulse generator 9 connected directly with a motor, a circuit 10 for measuring the interval of the rotational pulse, an average speed calculating circuit 11 for calculating an amount proportional to the reciprocal of the measured pulse interval, and a circuit 12 for calculating a predictive speed of a rotor using the calculated amount.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation speed detecting method and device for accurately detecting the rotation speed of a rotating body such as an electric motor, and further to a rotation speed controlling method and device for accurately controlling the rotation speed of the rotating body. Regarding

[0002]

2. Description of the Related Art FIG. 1 shows a conventional method for detecting a rotational speed and a speed feedback control system constructed by using the method. In the figure, 1 is an electric motor, 2 is a rotary pulse generator directly connected to the electric motor 1, and 3 is a pulse. An interval measuring circuit, 4 is an average speed calculating circuit, 5 is a speed reference value, 6 is a speed adjusting circuit, and 7 is a motor driving circuit.

FIG. 2 shows operation waveforms for explaining the principle of detecting the rotation speed of this speed feedback control system.

The operation of the speed feedback control system constructed using the conventional rotation speed detection method will be described with reference to FIG.

When the electric motor 1 is driven, from the rotary pulse generator 2 directly connected to the electric motor 1, time ... t _i-1 ,
At t _i , t _{i + 1} , t _{i + 2} ..., The rotation pulse train shown at the top of FIG. 2 ... P _i-1 , p _i , p _{i + 1} , p _{i + 2} ...
Is output to the pulse interval measuring circuit 3. The pulse interval measuring circuit 3 measures the interval of the rotation pulse using the measuring clock pulse shown in FIG. Specifically, the number of measurement clock pulses between the rotation pulse generation times is measured. The number of measured clock pulses is inversely proportional to the rotation speed of the electric motor 1. Therefore, an amount proportional to the reciprocal of the measured pulse number is used as the average speed calculation circuit 4
Calculate by

Now, a case where the rotation speed n of the electric motor 1 increases substantially linearly as shown in FIG. 2 with respect to time t will be described as an example. At this time, the rotation speed at time t _i-1 is n _i-1 ,
The rotation speed at time t _i is n _i , the proportional constant is k, and time t is
_{When the} number of measured clock pulses in the period T _pi between _i-1 and t _i is M _ci , the average rotation speed N _i of the electric motor 1 is given by the following equation.

[0007]

[Equation 1]

Since this value is obtained immediately after the time t _i , this detected value can be used for the period T _{pi + 1} between the times t _i and t _{i + 1} as shown in FIG. Become. Time t _i-1
Since the average rotation speed N _{i-1 of} one cycle before has been obtained in the period of t _i and t _i , this detected value is used.

Such average rotational speed is supplied to the speed adjusting circuit 6, and the difference from the speed reference value is supplied to the electric motor drive circuit 7.

[0010]

[0005] In the configured using a conventional rotational speed detection method speed feedback control system, the average rotational speed N _i which is measured in the period T _pi between times t _i-1 and t _i ,
Since it is used in the next period T _{pi + 1} , a detection delay occurs,
The difference between the motor rotation speed n and the average rotation speed N is the speed error. These are shown at the bottom of FIG.

If the speed error becomes excessive, the following problems will occur. That is, in the conventional speed feedback control system, this speed error is added to the control amount deviation with respect to the speed reference value as the feedback amount. Therefore, if the speed error becomes excessive, the accuracy deteriorates and the response speed is fast and stable. It becomes difficult to control.
In particular, at low speeds, the rotation pulse interval becomes large and the conventional method has an excessive error with respect to changing speeds, and control cannot be performed in response.

An object of the present invention is to provide a rotation speed detecting method and device which solves the above problems.

Another object of the present invention is to provide a rotation speed control method and device which solves the conventional problems.

[0014]

According to the present invention, in a method for detecting a rotation speed of a rotating body, a pulse interval of rotation pulses generated by a rotation pulse generating means directly connected to the rotating body is measured and measured. An amount proportional to the reciprocal of the pulse interval is calculated, and the predicted velocity of the rotating body is calculated using the calculated amount.

Further, the present invention is, in an apparatus for detecting a rotation speed of a rotating body, directly connected to the rotating body, for generating a rotation pulse, and for measuring a pulse interval of the generated rotation pulse. And means for calculating an amount proportional to the reciprocal of the pulse interval, and means for calculating the predicted speed of the rotating body using the calculated amount.

In the method of controlling the rotation speed of a rotating body, the present invention measures the pulse interval of the rotation pulse generated from the rotation pulse generating means directly connected to the rotating body, and calculates the reciprocal of the measured pulse interval. Is calculated, the predicted amount of the rotating body is calculated using the calculated amount, and the speed is adjusted by using the difference between the calculated predicted speed and the speed reference value. It is characterized by being driven.

Further, according to the present invention, in an apparatus for controlling a rotation speed of a rotating body, means directly connected to the rotating body for generating a rotation pulse, and means for measuring a pulse interval of the generated rotation pulse are measured. And a means for calculating an amount proportional to the reciprocal of the pulse interval, a means for calculating the predicted speed of the rotating body using the calculated amount, and a speed using the difference between the calculated predicted speed and the speed reference value. It is characterized by having a means for adjusting and a means for driving the rotating body by the output of the speed adjusting means.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 is a block diagram showing an embodiment of the rotation speed control device of the present invention.

In FIG. 3, 8 is an electric motor, 9 is a rotary pulse generator, 10 is a pulse interval measuring circuit for measuring the pulse interval of rotary pulses, 11 is an average speed calculation circuit, 12 is a predicted speed calculation circuit, and 13 is a speed. Reference numeral 14 is a speed adjusting circuit, and 15 is an electric motor drive circuit.

The rotary pulse generator 9 is usually a pulse encoder directly connected to the electric motor. When the electric motor is a brushless motor, a rotary magnetic pole position detector is used, and the rotary magnetic pole position detector has a three-phase rectangular shape. It is possible to generate a pulse train of 6 pulses per 360 electrical degrees by combining pulse generation circuits and the like based on the wave signal.

FIG. 4 is a diagram showing the principle of speed detection.
The case where the rotation speed n of the electric motor 8 increases almost linearly with respect to the time t is shown.

The operation of this embodiment will be described with reference to FIG.

When the electric motor 1 is driven, a rotational pulse train is directly supplied to the electric motor 8 and a rotational pulse train is given to the pulse interval measuring circuit 10. Pulse interval measuring circuit 10
Then, the rotation pulse interval is measured using the measurement clock pulse shown in FIG.

As shown in FIG. 4, assuming that the motor rotation speed at time t _i-1 is n _i-1 and the rotation speed at time t _i is n _i , the pulse interval given by the following equation

[0025]

[Equation 2]

M is the number of measurement clock pulses counted in
_{Assuming ci} , the average motor rotation speed N _i is as follows.

[0027]

[Equation 3]

FIG. 4 shows these relationships. As is clear from FIG. 4 and Expression (2), the following relational expression holds.

[0029]

[Equation 4]

In FIG. 4, the coordinates A (t _i-1 , n _i-1 )
And the equation of a straight line passing through two points of coordinates B (t _i , n _i ) is as follows.

[0031]

[Equation 5]

This equation can be linearly approximated even when the change in the number of revolutions is a curve with respect to time. The pulse interval T _pi is calculated by the pulse interval measuring circuit 10, and the average speed N _i of the equation (3) is calculated by the average speed calculating circuit 12. In the predicted speed calculation circuit 12, the rotation speed n at the given initial time t _i-1
i-1 and the average rotation speed N _i measured at the pulse interval T _pi
Accordingly, the rotation speed n is generated as a function of the time t by the equation (6).

Since the expression (6) holds even at time t ≧ t _i , the rotational speed n after the time t _i shown by the double straight line in FIG. 4 is calculated using various measured values in the measuring period T _pi. , Can be predicted. The predicted speed calculation circuit 12 realizes this function.

As can be seen from FIG. 4, since a continuous quantity approximate to the motor rotation speed n is obtained from the output of the predicted speed calculation circuit 12, this value is used as a feedback value and the speed adjustment circuit 14 together with the speed reference value 13 is used. PID control signal is obtained by performing transfer function processing such as proportional, integral, and differential on the difference between the two.
5 to drive the electric motor 8.

[0035]

According to the present invention, since the continuous rotation speed with respect to time can be detected even during acceleration / deceleration, there is an effect that a highly accurate continuous detection amount can be obtained regardless of the intermittent measurement method. Further, by using this detected amount as the feedback amount, there is an effect that continuous rotation speed control can be performed with high accuracy and stability. Further, even if the number of pulses per rotation is small, there is an effect that a continuous detection amount can be obtained.

In particular, at low speeds, the rotation pulse interval becomes large and the conventional method has an excessive error with respect to the changing speed, and control is impossible due to the response. However, in the method and apparatus of the present invention, continuous rotation speeds are Since it can be detected and is used as the feedback amount, it becomes close to continuous control, and there is an effect that accurate detection and stable control can be performed even at low speed.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a conventional speed detection feedback control system.

FIG. 2 is a diagram showing operation waveforms in FIG.

FIG. 3 is a block diagram showing an embodiment of the present invention.

FIG. 4 is a diagram for explaining a speed detection principle.

[Explanation of symbols]

 1,8 Electric motor 2,9 Rotational pulse generator 3,10 Pulse interval measuring circuit 4,11 Average speed calculation circuit 5,13 Speed reference value 6,14 Speed adjustment circuit 7,15 Electric motor drive circuit 12 Predicted speed calculation circuit

Claims (4)

[Claims] 1. A method for detecting a rotation speed of a rotating body, wherein a pulse interval of a rotation pulse generated from a rotation pulse generating means directly connected to the rotating body is measured, and the pulse interval is proportional to the reciprocal of the measured pulse interval. A method for detecting a rotation speed, comprising: calculating an amount, and using the calculated amount, calculating a predicted speed of the rotating body. 2. A device for detecting a rotation speed of a rotating body, which is directly connected to the rotating body, generates a rotation pulse, measures a pulse interval of the generated rotation pulse, and measures the pulse interval. And a means for calculating a predicted speed of the rotating body using the calculated quantity, and a rotation speed detecting device. 3. A method for controlling a rotation speed of a rotating body, wherein a pulse interval of a rotating pulse generated from a rotating pulse generating means directly connected to the rotating body is measured, and the pulse interval is proportional to a reciprocal of the measured pulse interval. Calculate the amount, using the calculated amount, to calculate the predicted speed of the rotating body, adjust the speed using the difference between the calculated predicted speed and the speed reference value, to drive the rotating body, A rotation speed control method characterized by the above. 4. A device for controlling the rotation speed of a rotating body, which is directly connected to the rotating body, generates a rotation pulse, measures the pulse interval of the generated rotation pulse, and measures the pulse interval. Means for calculating an amount proportional to the reciprocal of the following, means for calculating the predicted speed of the rotating body using the calculated amount, and means for speed adjustment using the difference between the calculated predicted speed and the speed reference value And a means for driving the rotating body by the output of the speed adjusting means, the rotation speed control device.