JPS6359783A - Driving method for ac servo control system - Google Patents

Abstract

PURPOSE:To dispense with a pole sensor, by locking a motor by DC excitation in only a short period in power supply and by detecting the pole position with the positioning pulse at that time as its origin. CONSTITUTION:After the power supply, a switch 9 is turned so that the phase-U current command iuref may be switched to the current equivalent to rated torque and the phase-V current command ivref to-iuref, reading the count value PO from a counter 3 when a rotor is stopped. Then, after the base block is released, DC excitation is performed. There, when the rotor is stopped the count value PZ of the counter 3 is read to and the electric angle origin PORG from the count values PO and PZ. In normal operation, from a ROM 13 a phase angle phi is read against the difference between the electric angle origin PORG and every moment's count value Pi and from a ROM 12 sin phi and sin(phi+2/3pi) is read against the phase angle.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a C servo control system using a permanent magnet type synchronous machine.

[Conventional technology]

AC servo control of a permanent magnet synchronous machine requires detection of the position of the magnetic pole, and normally a signal based on the phase of the induced voltage is generated using a signal from a ball sensor attached to the motor shaft.

[Problem that the invention seeks to solve]

Conventionally, in addition to incremental pulses, this ball sensor uses phase pulses or GRAY code pulses whose phase is matched to the magnetic pole position, but both of these methods not only increase the size of the sensor, but also require a considerable amount of time to adjust the phase. It requires time and skill. There is also a method of accelerating at about the rated current for a short period of time at the time of input without using a ball sensor until the origin pulse whose phase is aligned with the magnetic pole position is captured, but even in this case, the phase alignment of the origin pulse is essential.

[Means for solving problems]

The driving method of the AC servo control system of the present invention is to stop the synchronous machine at a stable point by excitation with two-phase DC current prior to normal driving, and to make a difference between the count value of the incremental encoder at that time and the count value at the start of DC excitation. An encoder count corresponding to the origin of phase excitation is calculated, and thereafter, the electrical angle phase of the synchronous machine is determined and driven based on the deviation from this encoder count.

[For production]

In the composite torque of a permanent magnetic pole type synchronous machine motor, each phase current i is calculated by assuming virtual torque constants Ku, Kv, and Kw.
It is given by the following equation depending on the spatial phase of u, iv, and iw.

τ=Real (Ku iu +Kv iv
+Kw iw ) Taking Ku as the reference vector of space, Ku=Ku, Xv=Kvej%π, Xw =Kw e
It becomes jy3π.

Let iu be a direct current that does not change over time, and the phase angle θ of Ku
When considering only Here, if we set 了v=-iej%q, -+, = 0(
From formula 1), the resultant torque is r=Real (Ku iejθ−Kuie”π j
O=Ku jReai (cosO+ j si
nθ−cos(θ12π) + j 5in(θ10%π)) = u 1(cosθ−cos (θ+yarc>>
=-IKu i 5in(θ+%π) sin(-%π
) = AKu i sin (θ+%π)
---(2) becomes.

That is, as shown in Fig. 3, if a U-phase magnetic force is created with direct current in a space forming an electrical angle θ from the position of the U-phase ball, and a current with the opposite polarity is passed through the ■ phase, and the W-phase current is 20, (
2) It is generated with the torque given by Eq. Here, the sign of the resultant torque changes as θ=nπ−%π. This switching is the point at which the potential reaches a stable state (the point at which it reaches a maximum).

Here, unless torque is applied from the outside, the permanent magnet type synchronous motor excited with two-phase DC current will stop the rotor at the value θ.

Furthermore, from the condition that generates deceleration torque before and after θ, θ〈2
Therefore, the stopping position at π (during one electrical rotation) is the number of pole pairs P
For a synchronous machine, there are P stopping points per mechanical rotation. However, when direct current is applied in a stepwise manner, only one nearby point that can be moved with the minimum energy is selected and stopped. In any case, this allows the starting point of the phase to be determined, allowing the synchronous machine to be driven without phase pulses.

〔Example〕

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

FIG. 1 is a block diagram of an embodiment of a servo motor control system to which the drive method of the present invention is applied, and FIG. 2 is a flowchart of calculating the electrical angle origin PORG by direct current excitation in this embodiment.

An incremental shaft encoder 2 is attached to the permanent magnet type synchronous machine 1, which outputs pulses P with a 90° phase difference.
Outputs origin pulse PC that is unrelated to PB and magnetic pole position.

The PG counter 3 is a counter that counts up/down by looking at the phase relationship between the P^ and PB pulses. Multipliers 7 and 8 apply sinφ to current command i that has passed through compensator 5 and limiter 6, respectively.

Multiply by 5in (φ + %π) to obtain current command i for U phase and ■ phase.
ur. f, output as 1vref. The multiplier 10 multiplies the DC current command 1ref by -1 to reduce the stiffness to phase 1.
This is the current command 1 verf. A switch 9 is provided between the current amplifier 11, the multipliers 7 and 8, and the multiplier IO, and during DC excitation, the multiplier IO1 is connected to the multiplier 7.8 during normal operation. .

Note that this switching of the switch 9 is performed by software. During DC excitation, the CPU 4 interrupts the PG counter 3 to set the count value Po at the rotor starting point and the subsequent count value Pi (i=1.2...).

n) sequentially to obtain the count value P of the rotor stop position.
s is calculated, and from the count values Po and Ps, the electric river origin P O
RG is determined and used for control during normal operation thereafter.

ROM+3 is the electrical angle origin PO obtained in this way.
The value of the phase angle φ with respect to the difference (Pi−PORG) including the sign between RG and the subsequent count value Pi every moment is stored. The ROM 12 stores the value of a sine function sinφ, 5in(φ+%π) for the phase angle φ.

Next, the calculation of the electrical angle origin by direct current excitation in this embodiment will be explained with reference to the flowchart of FIG.

After the power is turned on (step 21), the entire system including the CPU 4 is initialized (step 22). Next, the U-phase current iur. f is j rated (current equivalent to rated torque), ■ phase current command 1 vref is -1 uref (°,
-iw=O), then read the count value Po when the rotor is stopped from the PG counter 3 (step 24), and then release the base block (step 2).
5) Perform DC excitation (step 26). At this time,
The switch 9 is naturally switched to the multiplier IO side. Then, the count value Pi of the PG counter 3
are sequentially read (step 27), and it is determined whether the absolute value of the difference from the previous value is smaller than the set value β.Step 2
8), if it is smaller, it is assumed that the rotor has stopped, and the count value Pi at this time is set as the count value Ps (step 29).
). Next, the electrical angle origin PORG is determined from this pulse count value Ps and the count value PO at the starting point (step 30
~32). Due to initial DC excitation, the rotor is at most l/2
It rotates P (P is the logarithm of the ball) and stops, but depending on the direction of rotation, the electrical angle origin P OR expressed as a pulse count
It is necessary to separate the calculation of G. That is, in Fig. 4, the pulse count is up in CCW and down in CW, and the pulse count corresponding to 360 degrees of electrical angle is P3.
60, case A (accelerates to COW and stops)・
-Ps-Pol.

PORG = Ps + P360 /3 Case B (accelerates to GW and stops)...Ps - Po<
It is necessary to determine that 0PORG=pS-P360/3. This assumes that the direction of the vector of DC excitation iw is reversed by 180 degrees.

After this, in base block step 33), from the difference (Pi-PORG) including the sign between the electrical angle origin PORG and the subsequent pulse count value Pi at every moment, l (with reference to OMI3) is output. By referring to l(0M12) in φ, sinφ, 5in(φ+2π/
The value of 3) is determined, and smooth sinusoidal current driving becomes possible. Incidentally, the cumulative error in position over multiple rotations can be avoided by checking the position relative to the origin pulse.

〔Effect of the invention〕

As explained above, the present invention has the following effects by locking the motor by direct current excitation for a short time when the power is turned on, and detecting the pole position using the position pulse at that point as the origin.

■The hardware for the phase pulse signal generator can be removed from the shaft encoder, resulting in weight reduction.

■Reduced man-hours for phase matching work.

■It is possible to operate permanent magnet type synchronous machines with any number of poles using software.

■ Rotate the motor shaft shaft with a load device under DC excitation, monitor the fluctuation of the load device current, and count the potential sheath points due to DC excitation (the number of peaks of the load input current is the potential sheath point (corresponds to the number of poles), so even if the number of poles is unknown for a motor, the number of poles can be determined.As long as the number of pulses per rotation of the incremental encoder is known,
It can be applied to any permanent magnet type synchronous machine.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of a servo motor control system to which the drive method of the present invention is applied, FIG. 2 is a flowchart for calculating the electrical angle origin P ORG by DC excitation in the embodiment of FIG. The figure shows the phase relationship between the torque constant and the current vector, and Fig. 4 shows the stop position due to DC excitation and the electrical angle origin P0f (G. 1...Synchronous machine, 2...Incremental shaft Encoder, 3...
・PG counter, 4...cpu.

Claims (1)

[Claims] In an AC servo control system using a permanent magnet type synchronous machine,
Prior to normal driving, the synchronous machine is stopped at a stable point by two-phase DC excitation, and the encoder count corresponding to the one-phase excitation origin is calculated from the incremental encoder count value at that time and the count value at the start of DC excitation.
A driving method for an AC servo control system characterized in that the electrical angle phase of the synchronous machine is determined and driven based on the deviation after the encoder count.