JPH05197429A - Method and device for controlling stop angle of motor - Google Patents

Abstract

PURPOSE:To precisely control the stop angle of a motor without using a revolution speed detector. CONSTITUTION:A clock means 9 which is reset whenever the motor 1 rotates at a prescribed angle is provided. A first operation means 7A operating first output by multiplying a deviation between the present rotary angle of the motor and a target rotary angle by a first gain, a second operation means 7B operating second output by multiplying the measurement value of time by the clock means by a second gain and an addition means 7C operating the sum of first output and second output are provided. The motor is driven by generating output equivalent to the output of the addition means 7C. The first and second gains are set in such a way that the output torque of the motor, which is decided by first output, becomes less than the static torque of a load when the deviation becomes less than a set point, and the output torque of the motor exceeds the static torque when the motor stops and the measurement value of time by the clock means exceeds prescribed size.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stop angle control method for controlling a stop angle of an electric motor and a control device used for implementing the method.

[0002]

2. Description of the Related Art When a load is driven by using a reversible electric motor, a motor stop angle control device as shown in FIG. 2 is used to stop the load at an arbitrary position.

In FIG. 2, 1 is an electric motor to be controlled, 2 is a target rotation angle setter for setting a target stop angle of the electric motor, 3 is a rotation angle detector for detecting a rotation angle of an output shaft of the electric motor, and 4 is an electric motor. Is a rotation speed detector that detects the rotation speed of the. The rotation angle detector 3 is a detector that generates a detection pulse each time the electric motor rotates a certain angle (unit angle),
A rotary encoder is usually used as the rotation angle detector. The rotation speed detector outputs a signal proportional to the rotation speed of the electric motor, and a tacho generator is generally used as the rotation speed detector.

Reference numeral 5 is a rotation angle calculation means for calculating the current rotation angle of the electric motor by inputting the detection pulse obtained from the rotation angle detector 3, and this calculation means counts the detection pulses obtained from, for example, the rotation speed detector. Counter and a multiplier that multiplies the count value of the counter by a unit angle. Reference numeral 6 denotes a rotation speed calculation means for calculating the rotation speed (rpm) of the electric motor from the output of the rotation speed detector 4. The output of the rotation angle calculation means 5 and the output of the rotation speed calculation means 6 are given to the electric motor output calculation unit 7 '. Has been.

The electric motor output calculation unit 7'determines the deviation between the target rotation angle set by the target rotation angle setting device 2 and the current rotation angle calculated by the rotation angle calculation means,
At each rotational speed, the output of the electric motor required to make the deviation zero is calculated. The output of the electric motor output calculation unit 7 ′ is given to the electric motor drive unit 8, and the electric motor drive unit 8 outputs the output to the electric motor 1.
Is provided with a drive current required to generate the calculated output.

[0006]

In the conventional control device shown in FIG. 2, the rotation angle detector 3 and the rotation speed detector 4 are provided as two units.
Since it is necessary to attach two detectors to the electric motor, not only the cost becomes high, but also the electric motor unit becomes large.

In the control device shown in FIG. 2, the rotation speed detector 4 is omitted, and a detection pulse obtained from the rotation angle detector is given to the rotation speed calculation means 6 to determine the rotation speed from the generation interval of the detection pulse. It is also possible to calculate However, if such a rotation speed detection method is adopted when controlling the electric motor to stop at the target rotation angle, there are the following problems.

Since the rotation speed of the electric motor cannot be calculated after each detection pulse is generated from the rotation speed detector until the next detection pulse is generated, the rotation speed is low in a region where the detection pulse generation interval is long. Cannot be detected accurately (the rotation speed cannot be detected in time).

In a region where the rotation speed is low, microscopic fluctuations in the rotation speed of the electric motor are large, so that the detection error of the rotation speed becomes large.

It is impossible to judge from the detected value of the number of revolutions that the motor has stopped.

An object of the present invention is to provide a method for controlling a stop angle of an electric motor and a controller used for implementing the method, which makes it possible to precisely control the stop angle of the electric motor without using a rotation speed detector. To provide.

[0012]

According to the present invention, a deviation between a rotation angle of a motor for driving a predetermined load and a target rotation angle is detected, and the motor is controlled so that the deviation becomes zero. The present invention relates to a method for controlling a stop angle of an electric motor, which stops the electric motor when it becomes zero.

In the present invention, there is provided a clocking means for resetting each time the electric motor rotates by a certain angle, and a first calculation for calculating the first output by multiplying the deviation by the first gain. A second operation of multiplying the time measurement value by the time measuring means by the second gain to calculate the second output, and the electric motor corresponds to the sum of the first output and the second output. Drive the electric motor to produce an output.

The first gain is a coefficient by which the deviation is multiplied when a motor output required to make the deviation between the target rotation angle of the motor and the current rotation angle zero is obtained as a function of the deviation, and may be a constant. , A variable that changes according to the deviation may be used.

The second gain is a coefficient by which time is multiplied when a motor output required to start the motor against the static torque of the load is obtained as a function of time, and may be a constant. It may be a variable that changes.

According to the present invention, when the deviation between the rotation angle of the electric motor and the target rotation angle becomes less than the set value, the output torque of the electric motor determined by the first output becomes less than the static torque of the load, and the electric motor stops. Then, the first and second gains are set so that the output torque of the electric motor exceeds the static torque when the measured value of the time by the time measuring means exceeds a predetermined value.

As shown in FIG. 1, the control device of the present invention for carrying out the above-described method includes a target rotation angle setting device 2 for setting a target rotation angle of the electric motor 1 for driving a predetermined load,
A rotation angle detector 3 that outputs a detection pulse each time the electric motor rotates by a certain angle, a rotation angle calculation unit 5 that calculates the rotation angle of the electric motor using the detection pulse as an input, and a rotation calculated by the rotation angle calculation unit 5. An electric motor output calculation unit 7 that calculates the output of the electric motor necessary to make the deviation between the angle and the target rotation angle set by the target rotation angle setting unit 0, and an output that the electric motor calculates by the electric motor output calculation unit. And a motor drive unit 8 that supplies a drive current to the motor so as to generate

In the present invention, there is provided the clocking means 9 which is reset every time a detection pulse is generated, and the electric motor output calculation section calculates the first output by multiplying the deviation by the first gain. The calculating means 7A, the second calculating means 7B that calculates the second output by multiplying the time measurement value by the time measuring means 9 by the second gain, and the first output and the second output are added. And the adding means 7C. The method of setting the first gain and the second gain is the same as above.

Needless to say, it is necessary to stop the electric motor when the rotational angle position coincides with the target stop position and the deviation becomes zero, but in order to stop the electric motor, for example, the deviation becomes zero. At this time, a stop command may be issued to the electric motor drive section to forcibly stop the supply of the drive current to the electric motor, or when the deviation becomes zero, the time measuring operation by the time measuring means 9 is stopped. The electric motor output calculated by the electric motor output calculation unit 7 may be set to zero by setting the measured value of time to zero.

[0020]

With the above construction, the output of the electric motor is given by the following equation.

Motor output = δ × G1 + T × G2 (1) where δ is the deviation between the current rotation angle position of the motor and the target rotation angle, T is the time value measured by the timing means, and G1 is the first. The gain, G2, is the second gain.

When the target rotation angle is set and the deviation δ appears, the electric motor is driven so as to generate the output determined by the first term of the above equation (1). When the electric motor is rotating, the value measured by the time measuring means is zero, so the second term of the above equation (1) is zero.

When the rotation angle of the electric motor approaches the target rotation angle and the deviation becomes equal to or less than the set value, the output torque of the electric motor determined by the first term of the equation (1) becomes equal to or less than the static torque of the load, so the electric motor is temporarily stopped. To do. When the electric motor stops, the time measuring means is no longer reset, so the measured value of the time T by the time measuring means increases, and when the measured value exceeds a predetermined value, the electric motor restarts. When the electric motor rotates and the rotation angle detector 3 generates a detection pulse, the time measuring means 9
Since the measured value by becomes 0, the electric motor stops. By repeating these operations, the deviation δ between the rotation angle position (load position) of the electric motor and the target rotation angle approaches zero.
When the deviation becomes zero, the motor stops.

In the above configuration, it is conceivable to omit the time measuring means 9 and perform control using only the first term of the equation (1). In this case, however, if the first gain is small, the deviation will be small. When it approaches zero, the output of the electric motor is insufficient and the motor stops, so that the deviation cannot be reduced to zero due to insufficient control as shown by the curve a in FIG. Further, if the first gain is increased, over-control occurs as shown by a curve b in FIG. 3A, oscillation occurs around the target rotation angle, and it becomes impossible to converge the rotation angle of the electric motor to the target rotation angle. ..

On the other hand, when the control is performed using the first term and the second term of the equation (1) as in the present invention, the first gain is larger than the magnitude that may cause the control system to vibrate. It can be set low enough. Moreover, after the rotation angle approaches the target rotation angle and the motor is stopped once, the second term of the equation (1) is used to intermittently drive the motor until the rotation angle of the motor matches the target rotation angle. Therefore, Fig. 3
The deviation can surely be made zero as shown by the curve b in (B). The curve a in FIG. 3B shows the characteristic when the control is performed only by the first term of the equation (1).

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In realizing the control device of FIG. 1, as the rotation angle detector 3, a rotary encoder or the like that generates a pulse each time the electric motor rotates by a certain angle may be used, and its configuration is arbitrary. is there.

The clock means 9 can be composed of, for example, an oscillator for generating a clock pulse having a constant frequency, and a counter that counts the clock pulse and is reset each time the rotation angle detector 3 generates a detection pulse.

The rotation angle position calculation means 5 can be composed of a counter for counting the detection pulses output by the rotation angle detector 3 and a memory for storing the count value of the counter.

Each computing means of the motor output computing section 7 can be realized by using a computer.

The electric motor drive unit 8 may be a circuit that allows a drive current according to the electric motor output calculated by the electric motor output calculation unit 7 to flow to the electric motor, and a pulse current whose duty ratio changes according to the calculated electric motor output. A circuit adapted to supply the electric motor, a circuit adapted to phase-control the drive current of the electric motor according to the calculated electric motor output, or the like can be used.

FIG. 4 is a flowchart showing an example of a control algorithm when the electric motor output calculation unit 7 is realized by a computer. In the case of following this flow chart, when a control start command is given, first, each part (memory etc.) is initialized, and then it is checked whether or not an operation stop command is given. When the operation stop command is not given, the data of the target stop position θo and the data of the current rotational angle position θx are read, and the time measurement value T is read by the time measuring means. Next, the deviation δ is calculated, and when δ is not zero, A = δ × G1 [first term of equation (1)], B = T × G2 [second term of equation (1)] and C =
Calculate A + B. Then, the motor drive unit 8 is instructed to supply a drive current corresponding to the motor output C, and the motor is driven. After that, the process of reading the data of the target rotation angle θo is repeated, and the supply of the drive current is stopped when the deviation δ becomes zero.

The stop position can be controlled using only the rotation angle detector by obtaining the output of the electric motor using the following equation (2) instead of performing the control according to the equation (1). ..

[0033]

[Equation 1] The proportional gain of the equation (2) is the deviation when the motor output required to make the deviation _n zero is used as a function of the deviation _n.
It is a proportional constant multiplied by _n . Further, the integral gain is a coefficient by which the integral value of the deviation is multiplied when the motor output required to make the deviation zero is calculated as a function of the integral value of the deviation. Furthermore, the differential gain is the minute change in deviation (deviation _n-1
- as a function of the deviation _n), in case of obtaining the motor output required in order to improve the responsiveness of the control, small change in deviation (deviation _n-1 - is a coefficient to be multiplied by the deviation _n).

In the case of the above formula (2), since the PID control of the rotation angle is performed, the precise control as shown by the curve b in FIG. 3B is performed without the insufficient control or the overcontrol. be able to. However, in this case, since the calculation time is long, it is inevitable that the settling time is longer than that of the present invention.

[0035]

As described above, according to the present invention, the motor output is controlled so that the deviation becomes zero, and when the rotation angle of the motor approaches the target rotation angle, the motor is temporarily stopped, and thereafter, Since the target rotation angle is reached by intermittently driving the electric motor, the gain for determining the electric motor output required to reduce the deviation to zero is set to a relatively small value to prevent oscillation of the control system. It is possible to prevent and perform stable control. Also, since the motor is driven intermittently until the rotation angle matches the target rotation angle, the deviation can be reliably reduced to zero, and accurate stop angle control can be performed using only the rotation angle detector as a detector. There is an advantage that

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing an overall configuration of a conventional control device.

FIG. 3A is a diagram showing a control characteristic in the case of a conventional control device. (B) is a diagram showing a control characteristic in the case of an embodiment of the present invention.

FIG. 4 is a flowchart showing an example of a control algorithm according to the embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electric motor, 2 ... Target rotation angle setting device, 3 ... Rotation angle detector, 5 ... Rotation angle calculation means, 7 ... Electric motor output calculation part,
8 ... Electric motor drive unit, 9 ... Timing means.

Claims (2)

[Claims] Claim: What is claimed is: 1. A deviation between a rotation angle of a motor for driving a predetermined load and a target rotation angle is detected, the motor is controlled so as to reduce the deviation to zero, and the motor is controlled when the deviation becomes zero. In a method of controlling a stop angle of an electric motor for stopping the electric motor, a time measuring unit is provided which is reset every time the electric motor rotates by a certain angle, and the deviation is multiplied by a first gain to calculate a first output. 1 and a second calculation of multiplying the time measurement value of the time measuring means by a second gain to calculate a second output, and the electric motor outputs the first output and the second output. Driving the electric motor so as to generate an output corresponding to the sum of the output and the output torque of the electric motor determined by the first output when the deviation becomes equal to or less than a set value becomes equal to or less than the static torque of the load, When the electric motor is stopped, the timing means Stop angle control method of a motor, characterized in that the output torque of the motor is set to the first and second gain so as to exceed the static torque when the measured value of time exceeds a predetermined magnitude due. 2. A target angle setter for setting a target rotation angle of an electric motor for driving a predetermined load, a rotation angle detector for outputting a detection pulse each time the electric motor rotates by a predetermined angle, and the detection pulse. Rotation angle calculation means for calculating the rotation angle of the electric motor as an input, and necessary for zeroing the deviation between the rotation angle calculated by the rotation angle calculation means and the target rotation angle set by the target rotation angle setting device. A stop angle control device for an electric motor, comprising: an electric motor output calculation unit that calculates the output of the electric motor; and an electric motor drive unit that drives the electric motor so that the electric motor generates the output calculated by the electric motor output calculation unit. In the above, there is provided a clocking unit that is reset each time the detection pulse is generated, and the electric motor output calculation unit multiplies the deviation by a first gain to obtain a first output. First computing means for calculating, second computing means for computing a second output by multiplying a time measurement value by the time counting means by a second gain, the first output and the second output And an adding means for adding and, when the deviation becomes equal to or less than a set value, the output torque of the electric motor determined by the first output becomes equal to or less than the static torque of the load, the electric motor stops, and the timing means The stop angle control of the electric motor is characterized in that the first and second gains are set so that the output torque of the electric motor exceeds the static torque when the measured value of the time exceeds a predetermined value. apparatus.