JPH0965687A - Speed controller of motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a speed controller of a motor with which the control disturbance caused by noises which are contained in instructed speed signals can be reduced and the control for a wide range of an instructed revolution speed can be performed. SOLUTION: The value of an instructed revolution signal Vns outputted by an instructed revolution setting device 6 is converted into a digital value Dns by an A/D converter 8. A frequency which is proportional to the instructed revolution is defined as an instructed revolution frequency fns and the instructed revolution frequency fns corresponding to the digital value Dns is calculated by using a map. The deviation Δf between the instructed revolution frequency fns and the frequency fn of a revolution detection signal proportional to the revolution of a motor 1 is calculated. A PID calculation gain corresponding to the instructed revolution frequency fns is calculated by using a map and the duty ratio of the motor which is required to eliminate the deviation Δf is calculated by the obtained gain. A driving current is subjected to pulse width modulation so as to apply the driving current intermittently with the obtained duty ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed control device for an electric motor, which controls the rotational speed of the electric motor so as to keep it at an instructed rotational speed.

[0002]

2. Description of the Related Art Generally, a speed control device for controlling the rotation speed of an electric motor so as to keep it at a commanded rotation speed includes a speed detector for detecting the rotation speed of the motor, and a rotation speed detected by the speed detector and a commanded rotation speed. And a duty of the drive current of the electric motor required to make the deviation zero by performing proportional, integral and differential operations (PID operation) on the deviation calculated by the deviation calculating section. The PID calculator for calculating the ratio and the pulse width modulator for pulse width modulating the drive current of the electric motor so that the drive current is intermittently operated at the calculated duty ratio.

As a conventional speed control device, there are a deviation calculation unit and a PID calculation unit which are configured by analog circuits and one which is configured by using a microcomputer. In order to obtain a good control characteristic for a wide range of instructed rotation speeds in this type of control device, it is necessary to have a plurality of gains (referred to as PID gains) used when performing PID calculation. If the arithmetic unit and the PID arithmetic unit are configured using analog circuits, the PID gain cannot be easily switched. Therefore, recently, a speed control device in which the deviation calculation unit and the PID calculation unit are configured by using a microcomputer is widely used.

[0004]

SUMMARY OF THE INVENTION The present invention is directed to a speed control device for an electric motor, which realizes a deviation calculating section and a PID calculating section using a microcomputer.

In the conventional speed control device using a microcomputer, when the instructed rotational speed is given by an analog signal (for example, when the instructed rotational speed is given by a voltage signal obtained by dividing a constant DC voltage with a potentiometer), Since the value obtained by digitally converting the analog signal was used as it is as the data for giving the instructed rotation speed,
When noise is mixed in the analog signal, the noise often becomes a disturbance and disturbs the control.

Further, in the conventional speed control device, a plurality of PID gains are prepared and the PID gains are switched stepwise in accordance with the instructed rotation speed. Therefore, good control characteristics are obtained for all instructed rotation speeds. Was hard to get.

An object of the present invention is to provide a speed control device for an electric motor capable of reducing control disturbance due to noise mixed in an analog signal which gives an instruction rotational speed.

Another object of the present invention is to provide a speed control device for an electric motor in which the PID gain can be set appropriately for all instructed rotation speeds to obtain good control characteristics. It is in.

[0009]

SUMMARY OF THE INVENTION A motor speed control device according to the present invention includes a speed detector for outputting a speed detection signal having a frequency proportional to the rotation speed of the motor, and a size corresponding to an instruction rotation speed of the motor. Speed setting device that generates a speed command signal consisting of an analog signal having a certain degree, an analog-digital converter that converts the size of the speed command signal into a digital value (A / D conversion), and is proportional to the rotation speed command. A designated speed frequency calculation map storage unit that stores a designated speed frequency calculation map that gives a relationship between the digital value obtained from the analog-digital converter and the designated speed frequency with the frequency as the designated speed frequency, and a designated speed frequency calculation map. Using an instruction speed frequency calculating means for obtaining an instruction speed frequency corresponding to a digital value, A speed frequency deviation calculating means for calculating the difference from the wave number as a speed frequency deviation, and a duty of the drive current of the electric motor required to make the speed frequency deviation zero by performing proportional, integral and differential operations on the speed frequency deviation. A PID gain calculation map storage unit that stores a PID gain calculation map that gives the relationship between the PID calculation gain used when calculating the ratio and the designated speed frequency, and the PID calculation gain for the designated speed frequency is calculated as the PID gain calculation. PID gain calculating means for calculating using a map for use,
Using the PID calculation gain calculated by the PID gain calculation means, the duty ratio of the drive current of the electric motor required to perform proportional, integral and differential calculations on the speed frequency deviation to make the speed frequency deviation zero. PID to calculate
The calculation unit and the pulse width modulation unit that pulse-width-modulates the drive current so that the drive current is turned on / off at the duty ratio calculated by the PID calculation unit.

The instructed speed frequency calculating means standardizes the change amount of the digital value when the change in the digital value is detected by the signal change detecting means for detecting the presence or absence of the change in the digital value. A means for comparing with the value is provided, and the instruction speed frequency is calculated for the new digital value only when the variation exceeds the standard value.

The duty ratio of the drive current is usually expressed as an on-duty ratio. When the drive current is interrupted so that the on period ton and the off period toff are alternately generated, the on-duty ratio of the drive current is given by DF = {ton / (ton + toff)} × 100 [%] (1) .

The map used when various calculations are performed by the microcomputer is such that a plurality of points on a straight line or a curve giving a relationship between a specific variable and a target value calculated for the variable are map points. As numerical values (coordinates) that specify each of the plurality of map points
Is remembered.

In this specification, the word "calculation" is used in a broad sense, and the word "calculation" is used in the sense that it includes all operations for determining the value of a specific variable using a computer. . That is, in the sense that it includes not only an operation of obtaining a specific numerical value by causing a computer to perform an arithmetic operation using a mathematical expression but also an operation of determining a specific numerical value by only reading a numerical value stored in a storage device in advance. The word "arithmetic" is used.

For example, when the instruction speed frequency is calculated with respect to the digital value by using an instruction speed frequency calculation map which gives the relationship between the digital value obtained by A / D conversion of the instruction speed signal and the instruction speed frequency. , When the value of the indicated speed frequency is obtained by simply reading the value of the indicated speed frequency corresponding to the digital value from the map, and when the value of the indicated speed frequency is obtained by further interpolating the numerical value read from the map However, in the present specification, the instruction speed frequency is calculated in any of these methods.

As described above, when the digital value obtained by A / D converting the indicated rotational speed and the indicated speed frequency calculation map are used to calculate the indicated speed frequency for each digital value, The operation is performed according to the application of the electric motor, regardless of the relationship between the displacement amount of the speed adjustment operation unit (for example, the knob for moving the slider of the potentiometer) provided in the command speed setting device and the command speed signal. The relationship between the displacement amount of the section and the instructed speed can be set to a desired relationship.

For example, even if the relationship between the displacement amount of the operating portion of the indicated speed setting device and its output voltage is non-linear, the indicated speed frequency calculation map can be created appropriately so that the indicated speed can be calculated. It is possible to make the relationship between the displacement amount of the operation unit of the setting device and the instructed rotation speed a linear relationship. In addition, depending on the application of the electric motor (for example, when the electric motor is used in an electric vehicle), the displacement of the operating unit is not linearly increased with respect to the displacement amount of the operating unit of the instruction speed setting device. It may be desirable to increase the rate of increase in speed with an increase in the amount (for example, to increase the rotational speed in a quadratic function with respect to the displacement of the operating portion). Such characteristics can be easily realized by calculating the instructed speed frequency using the speed frequency calculation map.

Further, as in the present invention, the indicated speed signal is changed to A /
If the presence or absence of a change in the digital value obtained by D conversion is detected, and the instruction speed frequency is calculated for the new digital value only when the amount of change exceeds a predetermined standard value, analog Since it is possible to reduce the probability that the instruction rotational speed is erroneously set due to noise included in the signal, it is possible to reduce control disturbance due to noise.

When the speed frequency deviation is z, the integration time is Ti, and the differentiation time is Td, the duty ratio DF of the drive current is calculated, for example, by the following equation.

DF = K {z + (1 / Ti) ∫zdt + Td (dz / dt)} (2) where K is a PID calculation gain, and in the present invention,
When the indicated speed frequency is calculated, the calculated value and PI
The PID calculation gain K for each indicated speed frequency is calculated using the D gain calculation map. The PID calculation unit uses the PID calculation gain calculated in this way to calculate the duty ratio of the drive current required to make the speed frequency deviation z zero. In this way, if the PID calculation gain is calculated for each designated speed frequency, the PID calculation gain can be set to an appropriate value regardless of the designated speed frequency. It can be done well.

In order to obtain various different control characteristics,
By storing a plurality of PID gain calculation maps, the same speed control device can be applied to speed control of various different electric motors.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram for explaining an embodiment of the present invention. In the figure, 1 is a brushless DC electric motor as a control target, and the electric motor shown is
It is composed of a stator having three-phase armature coils Au to Aw, which are star-connected, and a rotor (not shown) having a magnet field. The electric motor 1 includes a position detector PS that detects the position of the rotor with respect to the armature coils of each phase of the stator by detecting the polarity of the magnetic poles of the rotor with a Hall element or the like, and the rotational speed of the electric motor. A rotary encoder RE as a speed detector for generating a pulse signal having a frequency proportional to is attached.

A three-phase bridge type inverter circuit 2 is provided in order to pass a driving current that commutates in a predetermined phase sequence through the armature coils Au to Aw of the electric motor 1. The inverter circuit 2 is a PNP transistor TR whose emitters are commonly connected.
NPN transistor TRx in which u to TRw are switch elements forming the upper side of the bridge and the emitters are commonly connected
.About.TRz as a switch element constituting the lower side of the bridge, and a bridge circuit of switch elements constituted by connecting collectors of transistors TRu to TRw to collectors of transistors TRx to TRz, respectively, and a transistor TR.
Feedback diodes Du to Dw connected in antiparallel between the emitters and collectors of u to TRw, and a transistor TR.
Feedback diodes Dx to Dz are connected in antiparallel between the collectors and emitters of x to TRz.

In the inverter circuit 2, the common connection points of the emitters of the transistors TRu to TRw and the common connection point of the emitters of the transistors TRx to TRz are positive and negative DC voltage input terminals 2a and 2 respectively.
b, the positive electrode side DC voltage input terminal 2a is connected to a positive electrode terminal of a DC power source (not shown) whose negative electrode is grounded,
The DC voltage input terminal 2b on the negative electrode side is grounded through a current detecting resistor R1 having a sufficiently small resistance value. Also, the collectors of the transistors TRu to TRw and the transistor TR
The output terminals 2 are connected to the collectors of x to TRz.
u to 2w, and these output terminals are connected to the terminals of the armature coils Au to Aw on the side opposite to the neutral point.

The position detector PS provided on the electric motor is
The position of the rotor is detected for each of the U, V, and W three-phase armature coils Au, Av, and Aw, and three rectangular wave-shaped position detection signals Hu, Hv, and Hw that are 120 degrees out of phase are generated. . These position detection signals are input to the distributor 3 together with the cw / ccw command signal for instructing whether the rotation direction of the electric motor is clockwise or counterclockwise.

The distributor 3 has output terminals respectively corresponding to the transistors TRu to TRw and TRx to TRz of the inverter circuit, and performs a predetermined logical operation on the position detection signals Hu to Hw to obtain cw / ccw. In order to determine the phase to be excited according to the rotation direction commanded by the command signal, and to supply the drive current to the armature coil of the determined phase,
The signals u ', v', w output from the output terminals corresponding to the transistors TRu to TRw and TRx to TRz, respectively.
The levels of ', x', y ', and z'are made high or zero. These signals are applied to the transistors TRu to T
It is input to the amplifier 4 having amplifier circuits corresponding to Rw and TRx to TRz. The amplifier 4 receives the signal u
′ To w ′ and x ′ to z ′ are amplified and output from the output terminals corresponding to the transistors TRu to TRw and TRx to TRz, respectively, to the transistors TRu to TRw and TR.
The drive signals u to w and x to z are supplied to the base of x to TRz.

A command speed setting device 6 is provided to give a command speed of the electric motor. Indicated speed setting device 6
Is a potentiometer VR to which a constant DC voltage E is applied. The potentiometer forming the command speed setting device 6 outputs a command speed signal Vns composed of an analog voltage having a magnitude corresponding to the amount of displacement of an operation part (not shown) for operating the slider.

The instructed speed signal Vns is input to the control unit 7 which is composed of a microcomputer. Control unit 7
Is an analog-digital converter (A / D converter) 8 for converting the magnitude of the instruction speed signal Vns into a digital value Dns, and a frequency proportional to the instruction rotation speed as an instruction speed frequency fns. An instruction speed frequency calculation map storage means 9 in which an instruction speed frequency calculation map for giving a relationship between the obtained digital value Dns and the instruction speed frequency fns is stored in the ROM or the EEPROM, and a digital value using the instruction speed frequency calculation map. Instructed speed frequency calculation means 1 for obtaining the instructed speed frequency fns corresponding to Dns
0, indicated speed frequency fns and speed detection signal frequency fn
The speed frequency deviation calculating means 11 for calculating the difference between the speed frequency deviation Δf and the speed frequency deviation Δf, and the drive current of the electric motor necessary for performing proportional, integral and differential operations on the speed frequency deviation Δf to make the speed frequency deviation zero. PID calculation gain K and designated speed frequency fns used when calculating the duty ratio of
And a PID gain calculation map storage means 12 in which a PID gain calculation map for giving a relationship with is stored in a ROM or an EEPROM, and a PID gain for calculating a PID calculation gain K with respect to an instructed speed frequency fns using the PID gain calculation map. Driving of the electric motor necessary for zeroing the speed frequency deviation by performing proportional, integral and differential operations on the speed frequency deviation Δf using the calculation means 13 and the PID calculation gain K calculated by the PID gain calculation means. The pulse width modulation section 5 is provided with a PWM signal that provides the duty ratio DF calculated by the PID calculation means 14. This PWM signal is composed of a pulse signal that is repeatedly turned on and off at the calculated duty ratio.

The pulse width modulation section 5 is provided with switch means for turning on / off the signals x to w output from the amplifier 4, and by turning on / off these switch means according to the PWM signal, the inverter circuit 2 TRu that forms the switch element on the upper side of the bridge
.About.TRw are turned on and off, and pulse width modulation is performed so that the drive currents respectively flowing through the armature coils Au to Aw are interrupted at a predetermined duty ratio.

The instructed speed frequency calculating means 10 detects the change in the digital value Dns and the change amount of the digital value when the change in the digital value is detected by the signal change detecting means. A means for comparing with a standard value is provided, and the instruction speed frequency is calculated for a new digital value only when the amount of change exceeds the standard value.

FIG. 2 is a flow chart showing an algorithm of control by the control unit 7 in FIG. The operation according to this flowchart is as follows. When the microcomputer is powered on by a switch (not shown), first, each part is initialized in step 1, and then in step 2, the magnitude of the instruction speed signal Vns is A / D converted by the A / D converter 8. The digital value Dns (stored in the register) obtained by doing is read. Next, in step 3, the instruction speed frequency fns corresponding to the read digital value is calculated using the instruction speed frequency calculation map that gives the relationship between the digital value and the frequency proportional to the instruction speed (instruction speed frequency). . In this case, the instruction speed frequency fns is set to be equal to the frequency of the pulse signal obtained from the rotary encoder (speed detector) RE when the electric motor rotates at the instruction speed.

After calculating the instructed speed frequency fns as described above, in step 4, it is judged whether or not a pulse (RE signal) is given from the rotary encoder RE. In this example, the rising edge of the pulse generated by the rotary encoder RE is recognized as the RE signal. RE
When the signal is recognized, in step 5, the difference between the instructed speed frequency fns and the frequency fn of the speed detection signal is calculated,
The calculated frequency difference is defined as velocity frequency deviation Δf. Then, the process proceeds to step 6, where the duty ratio D of the drive current required to make the instructed speed frequency and speed frequency deviation zero.
Using the PID gain calculation map that gives the relationship with F, the PID calculation gain K for the indicated speed frequency fns
[Refer to Expression (2)] is calculated. Next, at step 7, by using the calculated gain K for PID calculation, proportional, integral and differential calculations (PID calculation) are performed on the speed frequency deviation Δf, so that the drive current required for making the deviation Δf zero. The duty ratio DF is calculated, and in step 8, the PWM signal for interrupting the drive current with the duty ratio DF calculated from the pulse width modulator 5 is given to the pulse width modulator 5, and the process returns to step 4.

The pulse width modulator 5 operates the transistors TRu to TRw constituting the switch element on the upper side of the bridge of the inverter circuit 2 by intermittently connecting the signals u to w output from the amplifier 4 in accordance with the PWM signal. The drive current supplied to the electric motor 1 is pulse-width modulated by turning on and off with the duty ratio thus set.

If the RE signal is not recognized in step 4, the process shifts to step 9 to read a new digital value, and in step 10, the digital value read this time is compared with the digital value read last time and the variation ΔDns thereof is calculated. Calculate Next, at step 11, it is judged if the amount of change ΔDns is zero. If ΔDns is zero (when the digital value read this time is the same as the digital value read last time), the process returns to step 4. When ΔDns is not zero (when the digital value read this time is not the same as the digital value read last time), the process proceeds to step 12 and it is determined whether the change amount ΔDns of the digital value is less than or equal to the standard value. . As a result, when ΔDns is equal to or less than the standard value, it is determined that the change in the digital value is due to the noise included in the instruction speed signal Vns, and the operation returns to step 4 without calculating the instruction speed frequency. If ΔDns exceeds the standard value, it is considered that the instructed speed has been changed, and in step 13, the instructed speed frequency f is applied to the new digital value.
After calculating ns, the process returns to step 4.

In the case of the algorithm of FIG. 2, step 3 and steps 9 to 13 realize the instructed speed frequency calculating means for obtaining the instructed speed frequency corresponding to the digital value by using the instructed speed frequency calculation map. Further, the signal change detecting means for detecting the presence or absence of the change of the digital value is realized by steps 10 and 11, and step 12
Thus, when the change in the digital value is detected by the signal change detecting means, a means for comparing the amount of change in the digital value with the standard value is realized.

Further, the speed frequency deviation calculating means for calculating the difference between the instructed speed frequency and the frequency of the speed detection signal as the speed frequency deviation is realized by step 5, and step 6
As a result, the PID gain calculation means for calculating the PID gain for the indicated speed frequency using the PID gain calculation map is realized. Furthermore, in step 7, P
The PID calculation gain calculated by the ID gain calculation means is used to perform proportional, integral, and differential calculations on the speed frequency deviation to calculate the duty ratio of the drive current of the electric motor required to make the speed frequency deviation zero. A PID calculation means is realized.

In the equation (2) used in the above description,
The gain K for PID calculation is added to the sum of the proportional term, the integral term, and the derivative term.
However, the present invention can also be applied to the case where the proportional term, the integral term, and the derivative term are respectively multiplied by different gains K1, K2, and K3 for PID calculation as in the following equation. it can.

DF = K1 z + K2 (1 / Ti) ∫zdt + K3 Td (dz / dt)} (3) In the above example, the brushless DC motor is taken as an example of the motor to be controlled. The present invention can also be applied to the case where the drive current of the electric motor is PWM-controlled to control the speed.

[0038]

As described above, according to the present invention, by using the digital value obtained by A / D converting the instructed rotation speed and the instructed speed frequency calculation map, the instructed speed is calculated for each digital value. Since the frequency is calculated, regardless of the relationship between the displacement amount of the speed adjustment operation unit provided in the instructed speed setting device and the instructed speed signal, the operation unit can be operated according to the application of the electric motor. There is an advantage that the relationship between the displacement amount and the instructed speed can be set to a desired relationship.

Further, according to the present invention, the indicated speed signal is changed to A /
Since the presence or absence of a change in the digital value obtained by D conversion is detected, the instruction speed frequency is calculated for the new digital value only when the amount of change exceeds a predetermined standard value. There is an advantage that it is possible to reduce the probability that the instruction rotational speed is erroneously set due to noise included in the analog signal, and to reduce control disturbance due to noise.

Further, according to the present invention, when the designated speed frequency is calculated, the PID calculation gain for each designated speed frequency is calculated using the calculated value and the PID gain calculation map. In any case, the PID calculation gain can be set to an appropriate value regardless of the instruction speed frequency, and good control can be performed for a wide range of instruction speeds.

[Brief description of drawings]

FIG. 1 is a block diagram for explaining an embodiment of the present invention.

FIG. 2 is a flowchart showing a control algorithm according to the embodiment of the present invention.

[Explanation of symbols]

 1 Brushless DC Motor 2 Inverter Circuit 3 Distributor 4 Amplifier 5 Pulse Width Modulator 6 Indication Speed Setting Device 7 Control Unit 8 A / D Converter 9 Indication Speed Frequency Calculation Map Storage Means 10 Indication Speed Frequency Calculation Means 11 Speed Frequency Deviation Calculation means 12 PID gain calculation map storage means 13 PID gain calculation means 14 PID calculation means

Claims (1)

[Claims] 1. A speed detector for outputting a speed detection signal having a frequency proportional to the rotation speed of an electric motor, and an instruction speed for generating an instruction speed signal composed of an analog signal having a magnitude corresponding to the instruction rotation speed of the electric motor. A setter, an analog-digital converter for converting the magnitude of the instruction speed signal into a digital value, and a frequency proportional to the instruction rotation speed as an instruction speed frequency, and a digital value and an instruction speed frequency obtained from the analog-digital converter. And a designated speed frequency calculation map storage means for storing a designated speed frequency calculation map for giving a relationship with the designated speed frequency calculation map, and a designated speed frequency calculation means for obtaining a designated speed frequency corresponding to the digital value using the designated speed frequency calculation map. And a speed for calculating the difference between the instructed speed frequency and the frequency of the speed detection signal as a speed frequency deviation. A frequency deviation calculation means, proportional to the speed frequency deviation, by applying integration and differentiation operations used when calculating the duty ratio of the drive current of the motor required to zero the speed frequency deviation PI
A PID gain calculation map storage unit that stores a PID gain calculation map that gives a relationship between the D calculation gain and the designated speed frequency, and a PID calculation gain for the designated speed frequency using the PID gain calculation map. Necessary for performing proportional, integral, and differential operations on the speed frequency deviation using the PID gain operation means for operation and the PID operation gain calculated by the PID gain operation means to make the speed frequency deviation zero. P for calculating the duty ratio of the drive current of the electric motor
An ID calculation unit and a pulse width modulation unit that pulse-width-modulates the drive current so as to interrupt the drive current at the duty ratio calculated by the PID calculation unit. The signal change detecting means for detecting the presence or absence of a value change, and means for comparing the amount of change in the digital value with a standard value when the signal change detecting means detects a change in the digital value are provided. A speed control device for an electric motor, wherein the speed control device is configured to calculate an instructed speed frequency for a new digital value only when the amount exceeds a standard value.