JP4495403B2 - Control method of servo motor encoder - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a servo motor encoder, and more particularly, to a servo motor encoder and a control method thereof for reducing the number of signal lines.
[0002]
[Prior art]
Conventionally, an incremental encoder that outputs a three-phase incremental signal (A, B, Z) and a three-phase magnetic pole position detection signal (U, V, W) has been used for servo motor control. Incremental signals (A, B, Z) are composed of two layers of square wave signals (A, B) with different phases by 90 ° and square wave output (Z) of the origin signal output at the origin position. The Based on this incremental signal, the rotation direction, rotation speed, and rotation position of the motor are detected. That is, the rotation direction is detected based on which of the A and B signals is output first, and the rotation speed is detected based on the period of the A and B signals. Further, the reference position of the motor rotor is detected from the Z signal, and the rotor rotational position is detected by integrating (or subtracting) the A and B signals from that point.
[0003]
The magnetic pole position detection signal (U, V, W) is a square wave output signal having a phase difference of 120 ° corresponding to the electrical angle. As the motor is driven, a three-phase magnetic pole position detection signal is output, and the magnetic pole position of the rotor is detected by the combination thereof. According to this magnetic pole position, the coil on the stator side is appropriately switched and excited to form a rotating magnetic field around the rotor. As a result, the rotor continues to rotate and the motor is driven in a desired speed and direction.
[0004]
In such an encoder, a circuit configuration as shown in FIG. 10 is conventionally used for detecting each signal. FIG. 10 is a block diagram showing a circuit configuration of a conventional servo motor encoder. The servo motor encoder includes a motor unit 51 disposed on the motor side and a controller 52 disposed on the control device side. The motor unit 51 is provided with an encoder 53 and a line driver 54. The controller 52 is used for motor control, and is provided with a line receiver 55 and a CPU 56. For signal transmission between the line driver 54 and the line receiver 55, a differential balanced type system such as RS-422 which is resistant to noise is used.
[0005]
The encoder 53 includes an incremental signal output unit 57 that outputs a three-phase incremental signal (A, B, Z) and a magnetic pole position detection signal output unit 58 that outputs a three-phase magnetic pole position detection signal (U, V, W). It has. The incremental signal output unit 57 and the magnetic pole position detection signal output unit 58 are connected to driver units 59A, 59B, 59Z; 61U, 61V, 61W provided in the line driver 54, respectively.
[0006]
The driver units 59A, 59B, 59Z of the line driver 54 are provided for each incremental signal. Each driver unit 59A and the like are connected to the corresponding incremental signal output unit 57 on the input side, and a pair of output terminals 62A, 62B, and 62Z are provided on the output side. Incremental signals A, A bar, B, B bar, Z, Z bar having different phases are respectively output from the output terminals 62A, 62B, 62Z. Incremental signals A, A and the like are used for detecting the rotor position of the motor.
[0007]
The driver units 61U, 61V, 61W of the line driver 54 are also provided for each magnetic pole position detection signal. Each driver unit 61U and the like is connected to the corresponding magnetic pole position detection signal output unit 58 on the input side, and a pair of output terminals 63U, 63V, and 63W are provided on the output side. Magnetic pole position detection signals U, U bar, V, V bar, W, W bar having different phases are output from the output terminals 63U, 63V, 63W, respectively.
[0008]
The line driver 54 is connected to the line receiver 55 via the signal line 64. The line receiver 55 is provided with receiver portions 65A, 65B, 65Z; 66U, 66V, 66W. The receiver units 65A, 65B, and 65Z receive signals from the driver units 59A, 59B, and 59Z of the line driver 54. The receiver units 66U, 66V, 66W receive signals from the driver units 61U, 61V, 61W of the line driver 54. The receiver unit 65A and the like receive signals from the driver unit 59A and the like, and output an incremental signal (A, B, Z) and a magnetic pole position detection signal (U, V, W) to the CPU 56.
[0009]
Further, power lines 67 and 68 are provided between the motor unit 51 and the controller 52. The power supply line 67 is used for + power supply (VCC), and the power supply line 68 is used for ground connection (GND). As a result, power is supplied to the encoder 53 and the line driver 54 of the motor unit 51.
[0010]
[Patent Document 1]
Japanese Patent Laid-Open No. 8-18455
[Problems to be solved by the invention]
However, since such a servo motor encoder has the above-described configuration, a total of 14 wires are used between the motor unit 51 and the controller 52 as shown in FIG. That is, twelve signal lines 64 ((A, B, Z; U, V, W) × 2) and two power supply lines 67, 68 are provided. For this reason, the number of harness cores between the line driver 54 and the line receiver 55 is increased, the number of parts and the number of assembling steps are increased, and there is a problem that the product cost is increased.
[0012]
An object of the present invention is to reduce the number of signal lines and reduce the cost of circuit components by commonly using signal lines.
[0018]
[Means for Solving the Problems]
The servo motor encoder control method according to the present invention includes an encoder that outputs a three-phase incremental signal (A, B, Z) and a three-phase magnetic pole position detection signal (U, V, W), and the magnetic pole position. a detection signal, and a D / a converter output circuit that converts an analog signal output having a voltage value corresponding to a combination of U of the magnetic pole position detection signal, V, W phases of the signal state (H, L), wherein based on the voltage value of the analog signal, the analog signal, the magnetic pole position detection signal of each phase of the signal state (H, L) servo motor comprising a control means for converting the signal information indicating a combination of the a control method for use encoder, the control means, prior to said encoder start, the initial rotor electrical angle of the servo motor based on a combination of each phase of the signal state of the magnetic pole position detection signals (H, L) Estimate value It is characterized in.
[0019]
In the servo motor encoder control method of the present invention, since the rotor electrical angle is estimated before the motor is started, the magnetic pole position detection signal (U, V, W) does not change, and the analog signal obtained therefrom Will not change. Therefore, it is not necessary here to transmit the analog signal at high speed, and the magnetic pole position information can be transmitted without any problem even with the analog signal.
[0020]
Further, in the control method of the servo motor encoder, the control means estimates an initial value of the rotor electrical angle before starting the servo motor, and then includes the servo motor in the incremental signal as the servo motor starts. When the origin signal (Z) output once per rotation of the rotor is input , the rotor electrical angle of the servo motor is corrected to an angle at a predetermined position where the origin signal (Z) is output. good. Further, the control means uses the estimated initial value of the rotor electrical angle as an origin until the origin signal (Z) is obtained, and a plurality of pulse signals that are output per rotation of the rotor of the servo motor among the incremental signals. A counter may be incremented or decremented using (A, B) to estimate and calculate the rotor electrical angle of the servo motor.
[0021]
Further, the control means corrects the rotor electrical angle of the servo motor based on the origin signal (Z) , and then uses the pulse signal (A, B) of the incremental signal to rotate the rotor electrical angle of the servo motor. May be calculated to control the drive of the servo motor.
[0022]
In addition, the control means may set the center value of the range of the rotor electrical angle indicated by the combination of the signal states (H, L) of the phases as the estimated initial value of the rotor electrical angle. good.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a circuit configuration of a servo motor encoder according to an embodiment of the present invention. As shown in FIG. 1, the servo motor encoder includes a motor unit 1 arranged on the motor side and a controller 2 arranged on the control device side. The motor unit 1 is provided with a D / A conversion output circuit 11 in addition to the encoder 3 and the line driver 4. The controller 2 is provided with an interface circuit 12 in addition to the line receiver 5 and the CPU (control means) 6. The motor unit 1 and the controller 2 are connected via signal lines 16 and 24. For signal transmission between the line driver 4 and the line receiver 5, a differential balanced system such as RS-422 is used.
[0024]
The encoder 3 includes an incremental signal output unit 7 that outputs a three-phase incremental signal (A, B, Z) and a magnetic pole position detection signal output unit 8 that outputs a three-phase magnetic pole position detection signal (U, V, W). It has. The incremental signal output unit 7 is connected to the line driver 4, and the magnetic pole position detection signal output unit 8 is connected to the D / A conversion output circuit 11.
[0025]
Further, power lines 25 and 26 are provided between the motor unit 1 and the controller 2. The power line 25 is used for + power supply (VCC), and the power line 26 is used for ground connection (GND). As a result, power is supplied to the encoder 3, the line driver 4, and the D / A conversion output circuit 11 of the motor unit 1.
[0026]
The line driver 4 is provided with driver units 13A, 13B, and 13Z. The driver units 13A, 13B, and 13Z are connected to the output terminals 14A, 14B, and 14Z of the respective phases of the incremental signal output unit 7. The driver units 13A, 13B, and 13Z are provided with a pair of output terminals 15A, 15B, and 15Z. The signal A and the signal A bar are selectively output from the output terminal 15A, the signal B and the signal B bar are selectively output from the output terminal 15B, and the signal Z and the signal Z bar are selectively output from the output terminal 15Z, respectively.
[0027]
The line receiver 5 is provided with receiver portions 17A, 17B, and 17Z. The line receiver 5 is connected to the line driver 4 via the signal line 16, and the receiver units 17A, 17B, and 17Z receive signals from the driver units 13A, 13B, and 13Z of the line driver 4, respectively. The receiver unit 17A and the like receive a signal from the driver unit 13A and the like, and output an incremental signal (A, B, Z) to the CPU 6.
[0028]
The D / A conversion output circuit 11 converts the three-phase magnetic pole position detection signal (U, V, W) output from the magnetic pole position detection signal output unit 8 of the encoder 3 into an analog signal (analog voltage value) and outputs it. To do. FIG. 2 is a block diagram showing the configuration of the D / A conversion output circuit 11. As shown in FIG. 2, the D / A conversion output circuit 11 is a resistance ladder type digital-to-analog converter that converts a combination of magnetic pole position detection signals (U, V, W) into eight analog voltages. Output.
[0029]
Signals (U, V, W) output from the output terminals 18U, 18V, 18W of the respective phases of the magnetic pole position detection signal output unit 8 are respectively C-MOS type buffer ICs (for example, 74HC04 type) 19U, 19V, It is input to 19W. Resistors 21U, 21V, and 21W are connected downstream of the buffer ICs 19U, 19V, and 19W. Subsequent stages of the resistors 21U, 21V, and 21W are grounded via the resistors 22U, 22V, and 22W, and are connected to the operational amplifier 23. The operational amplifier 23 is connected to a voltage follower and is supplied with power from the VCC in a single power supply system. The output signal of the operational amplifier 23 is input to the interface circuit 12 of the controller 2 through the signal line 24.
[0030]
The interface circuit 12 is connected to the CPU 6 and is used as a noise filter. The analog signal output from the D / A conversion output circuit 11 is input to the CPU 6 via the interface circuit 12 and is 3 bits corresponding to the states of U, V, and W by the A / D converter built in the CPU 6. Is converted to a digital value. 3 is a table showing the relationship between the magnetic pole position detection signal (U, V, W) of the encoder 3 and the output signal of the D / A conversion output circuit 11, and FIG. It is a table | surface which shows the relationship with the 3-bit digital value (U, V, W) produced based on.
[0031]
As shown in FIG. 3, the magnetic pole position detection signals (U, V, W) of the encoder 3 are inverted (UB, VB, WB) by the buffer ICs 19 U, 19 V, 19 W and input to the operational amplifier 23. At this time, the output voltage from the operational amplifier 23 changes from 0 (V) to 7/8 VCC (V) as shown in FIG. 3 according to the input signal. That is, the 3-bit combination of the magnetic pole position detection signals (U, V, W) is converted by the D / A conversion output circuit 11 into analog signals having eight voltage values corresponding to the signal states of each phase.
[0032]
On the other hand, on the CPU 6 side, based on the voltage value of the input analog signal, the analog signal is converted into a 3-bit digital value (signal information) indicating the signal state of each phase of the magnetic pole position detection signal. For example, when the input voltage is not less than 11/16 VCC and less than 13/16 VCC, it is determined that (U, V, W) is the center value 12/16 = 6/8 VCC, and the relationship of FIG. It is assumed that (U, V, W) = (0, 0, 1). Similarly, for example, in the case of 5/16 VCC or more and less than 7/16 VCC, (U, V, W) is changed from the center value 6/16 = 3/8 VCC to (U, V, W) = (1, 0, 0) ). When the voltage value is 13/16 VCC or more or 1/16 or less, (U, V, W) = (0,0,0) or (1,1,1), which cannot appear when the motor is operating. Since it is a combination of signals, it is determined as an error (error).
[0033]
Next, the operation of the servo motor encoder will be described. FIG. 5 is a flowchart showing the operation at the start of the encoder of FIG. Here, first, the magnetic pole position detection signal (U, V, W) is acquired, the current rotor electrical angle is estimated, and the value is stored in the RAM of the CPU 6 (step S1). The rotor electrical angle is estimated by a combination of three magnetic pole position detection signals (U, V, W). At this time, the above-described (U, V, W) converted from the analog voltage value of the D / A conversion output circuit 11 is estimated. W) value is used.
[0034]
FIG. 6 is a time chart showing the relationship between the magnetic pole position detection signal and the rotor electrical angle when the rotor rotates counterclockwise. FIG. 7 shows the magnetic pole position detection signal and the rotor electrical angle when the rotor rotates clockwise. It is a time chart which shows the relationship. For example, when the analog voltage value is 3/16 VCC or more and less than 5/16 VCC, the (U, V, W) value is (1, 0, 1) as shown in FIG. In this case, when the position where the combination of U, V, and W is (1, 0, 1) = “H, L, H” in FIG. 6 is seen, this indicates that the rotor has an electrical angle of 0 ° to 60 °. It can be seen that this is the case. Therefore, at this time, the rotor is estimated to be at the position of the electrical angle of 30 ° of the central value, and the value is set as the initial value of the electrical angle, which is stored in the RAM. Similarly, when the analog voltage value is 1/16 VCC or more and less than 3/16 VCC, the (U, V, W) value is (1, 1, 0), and the combination of U, V, W is “H, H, Since the position of “L” is in the case of an electrical angle of 120 ° to 180 °, the estimated initial value of the electrical angle is set to 150 ° at this time.
[0035]
Here, the magnetic pole position detection signals (U, V, W) can be obtained even when the motor is not rotating. Therefore, such estimation of the rotor electrical angle can be performed before starting the motor. Since the magnetic pole position detection signal (U, V, W) does not change when the motor is stopped, the analog signal obtained therefrom does not change. That is, high-speed transmission of U, V, and W signals is not necessary here, and information can be transmitted without any problem even with analog signals that are generally inferior in information transmission speed compared to digital signals. The analog signal is easily affected by noise, but the rotor electrical angle estimation process can be performed when the motor is stopped, so that the noise is small. Furthermore, since the interface circuit 12 and the CPU 6 can perform noise filter processing, sufficient measures against noise are taken. It is possible.
[0036]
After setting the initial value of the electrical angle in this way, the value of the electrical angle written in the RAM is written in the presettable with origin (step S2). For example, in the above example, when the estimated initial value of the electrical angle is 30 °, the count value corresponding to that value is written in the presettable counter as the initial value.
[0037]
As the motor is driven, signals A and B are input to the CPU 6. FIG. 8 is a time chart showing the incremental signals (A, B, Z) when the rotor rotates counterclockwise, and FIG. 9 shows the incremental signals (A, B, Z) when the rotor rotates clockwise. It is a time chart. As shown in FIGS. 8 and 9, the signal A and the signal B among the incremental signals are output with a 90 ° phase shift with the rotation of the rotor. On the other hand, the signal Z is output once per rotation of the rotor. The position where the signal Z is output is known in advance from the installation position of the magnetic detection element, and the rotation angle of the rotor can be detected by counting the number of input pulses of the signals A and B after obtaining the signal Z. .
[0038]
When the signals A and B are input to the CPU 6, the presettable counter is thereby incremented (counterclockwise) or decremented (clockwise) (step S3). At this time, the CPU 6 monitors whether or not a Z-phase incremental signal (origin signal) has been input (step S4). Until the Z signal is input, the count in step S3 is continued. Based on this value, the rotor rotation angle is estimated and the coil excitation phase is controlled. When the electrical angle error is φ, the motor torque is a value obtained by multiplying cos φ as compared with the case where there is no electrical angle error. For this reason, when φ = −30 ° to + 30 ° as in the above estimated value, cos φ ≧ (√3) /2≈0.866, and the motor starting torque is within a range of about 13.4% reduction at the maximum. Be controlled.
[0039]
When the Z signal is input, the process proceeds to step S5, and the counter is reset. As described above, the rotor rotation angle when the Z signal is input is determined in advance, and when it is input, the rotor rotation angle is accurately grasped, so the counter is reset to that angle. In step S6, the motor is controlled by accurate rotor position detection reset by the Z signal.
[0040]
In this way, the servo motor encoder converts the three-phase magnetic pole position detection signal (U, V, W) into an analog signal having eight values and outputs it. It becomes possible to cover with one. Accordingly, as shown in FIG. 1, the wiring between the motor unit 1 and the controller 2 is nine (six digital signal lines 16, one analog signal line 24, and two power supply lines 25, 26). Servo motor encoders can be formed with a reduced configuration. With this line saving, the number of circuits between the line driver 4 and the line receiver 5 is reduced by half, and even if the signal line 24 is added, it is possible to reduce five wirings. Therefore, the number of harness cores between the motor unit 1 and the controller 2 can be reduced, and the number of parts and assembly man-hours are reduced. In addition, since an inexpensive resistor ladder type converter can be used for the D / A conversion output circuit 11, although the D / A conversion output circuit 11 and the interface circuit 12 are added, the cost of the circuit components as a whole can be reduced. It becomes possible to plan.
[0041]
It goes without saying that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention.
For example, in the servo motor encoder described above, an ASIC (Application Specified IC) may be used instead of the CPU 6. In the above-described embodiment, the counter is incremented when counterclockwise, but the counter may be incremented when clockwise and decremented when counterclockwise. Furthermore, although the configuration using a resistance ladder type converter as the D / A conversion output circuit 11 is shown, other types of digital / analog converters can be used.
[0042]
【The invention's effect】
According to the servo motor encoder control method of the present invention, since the rotor electrical angle is estimated before the motor is started, the magnetic pole position detection signal (U, V, W) does not change, and the analog signal obtained therefrom is also obtained. It does not change. Therefore, the servo motor encoder does not need to transmit an analog signal at high speed, and can transmit magnetic pole position information without any problem even with an analog signal. The servo motor encoder to which the control method of the present invention is applied converts the magnetic pole position detection signal (U, V, W) into an analog signal having a voltage value corresponding to the signal state of each phase and outputs it. / A conversion output circuit and a control means for converting the analog signal into signal information indicating the signal state of each phase of the magnetic pole position detection signal based on the voltage value. It is possible to cover a single signal line for transmitting a signal to the control means, so that the encoder can be saved. For this reason, the number of parts and assembly man-hours of the servo motor encoder can be reduced, and the cost of the circuit parts can be reduced.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a circuit configuration of a servo motor encoder according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a configuration of a D / A conversion output circuit.
FIG. 3 is a table showing a relationship between an encoder magnetic pole position detection signal (U, V, W) and an output signal of a D / A conversion output circuit.
FIG. 4 is a table showing a relationship between an output signal of a D / A conversion output circuit and a 3-bit digital value (U, V, W) created based on the output signal.
5 is a flowchart showing an operation at the time of starting in the encoder of FIG. 1. FIG.
FIG. 6 is a time chart showing the relationship between the magnetic pole position detection signal and the rotor electrical angle when the rotor rotates counterclockwise.
FIG. 7 is a time chart showing the relationship between the magnetic pole position detection signal and the rotor electrical angle when the rotor rotates clockwise.
FIG. 8 is a time chart showing incremental signals (A, B, Z) when the rotor rotates counterclockwise.
FIG. 9 is a time chart showing incremental signals (A, B, Z) when the rotor rotates clockwise.
FIG. 10 is a block diagram showing a circuit configuration of a conventional servo motor encoder.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Motor part 2 Controller 3 Encoder 4 Line driver 5 Line receiver 6 CPU
7 Incremental signal output unit 8 Magnetic pole position detection signal output unit 11 D / A conversion output circuit 12 Interface circuit 13A, 13B, 13Z Driver unit 14A, 14B, 14Z Output terminal 15A, 15B, 15Z Output terminal 16 Digital signal line 17A, 17B , 17Z Receiver unit 18U, 18V, 18W Output terminal 19U, 19V, 19W Buffer IC
21U, 21V, 21W Resistor 22U, 22V, 22W Resistor 23 Operational Amplifier 24 Signal Line 25 Power Line 26 Power Line 51 Motor Unit 52 Controller 53 Encoder 54 Line Driver 55 Line Receiver 56 CPU
57 Incremental signal output unit 58 Magnetic pole position detection signal output unit 59A, 59B, 59Z Driver unit 61U, 61V, 61W Driver unit 62A, 62B, 62Z Output terminal 63U, 63V, 63W Output terminal 64 Signal line 65A, 65B, 65Z Receiver unit 66U, 66V, 66W Receiver 67 Power supply line 68 Power supply line

Claims (1)

An encoder that outputs a three-phase incremental signal (A, B, Z) and a three-phase magnetic pole position detection signal (U, V, W);
The magnetic pole position detection signal is converted to an analog signal having eight analog voltage values corresponding to combinations of signal states (H, L) of the U, V, and W phases of the magnetic pole position detection signal and output. An A conversion output circuit;
Control means for converting the analog signal into signal information composed of a 3-bit digital value indicating a combination of signal states (H, L) of each phase of the magnetic pole position detection signal based on the voltage value of the analog signal; , And
The control means sets, as the initial value of the rotor electrical angle, the central value of the range of the rotor electrical angle indicated by the combination of signal states (H, L) of each phase of the magnetic pole position detection signal before the servo motor is started. After estimation, start the servo motor,
Until the origin signal (Z) is obtained, the estimated initial value of the rotor electrical angle is used as the origin, and among the incremental signals obtained as the servo motor is started, a plurality of outputs are output per rotation of the rotor of the servo motor. Using the pulse signals (A, B) generated, the counter is incremented or decremented to estimate the rotor electrical angle of the servo motor,
Among the incremental signals, when an origin signal (Z) output once per rotor rotation of the servo motor is input, a rotor electrical angle of the servo motor is determined at a predetermined position where the origin signal (Z) is output. Corrected to the angle of
After correcting the rotor electrical angle of the servo motor based on the origin signal (Z), the rotor electrical angle of the servo motor is calculated using the pulse signal (A, B) of the incremental signal, and the servo motor control method for a servo motor encoder, wherein the drive control.

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