JPH03124285A - Synchronous ac servo motor driver - Google Patents

Abstract

PURPOSE:To employ a motor in such application as full rotation of the motor upon throw-in of power supply causes a trouble by detecting the position of a pole when the motor is started to be rotated by gradually increasing its torque in a state that the motor is steady. CONSTITUTION:Since the torque of a motor 5 is gradually increased when the command value of a peak current command Im is slightly increased at each time a current electric angle thetae becomes 2pi, it soon overcomes a frictional torque to rotate in a positive or negative direction according to the relationship between the initial position of the pole and the angles thetae, thetae' at that time. In this case, an incremental encoder 6 attached to the motor 5 is simultaneously rotated to output pulse signals PA, PB. Accordingly, it is compared with a set value of preset small amount obtained by counting the number of pulses to detect a small rotation of the position of the pole together with its direction. It can be employed in such application as the rotation of the motor 5 upon turn ON of power source cause a trouble.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a synchronous AC servo motor drive device, and more particularly to a detection circuit for detecting the ball position of the motor.

[Prior Art] Conventionally, this type of detection circuit, as shown in FIG.
The ball position was detected using phase signals pu, pv, and p. Next, the operation of this conventional ball position detection circuit will be explained.

The currents flowing through the U-phase, ■phase, and W-phase windings of the synchronous AC servo motor are shown below.

1 in formula (1). , is the arc current value, and θ8 is the current electrical angle. The rotation angle (electrical angle) of the ball position of the magnet attached to the motor rotor from a predetermined fixed origin is θ, and 0. When =02, it is assumed that no torque is generated in the motor. In other words, the power factor is 0%. Therefore, in order to generate the maximum torque in the motor, the following equation (2) is used.
It is necessary to satisfy the following, and in this case, the power factor is 100%. Also, θ.

Assume that the motor torque is generated.

The electrical angle θ, which indicates the ball position, is detected by an encoder installed to detect the rotational position and speed of the motor, and the number of pulses P per two balls of the motor and the fixed origin (θ
11 = Orad ), it can be calculated using the following equation (3).

However, with an incremental type encoder, the value of N at the ball position when the power is turned on is not known, and θ cannot be detected. Therefore, in addition to the output signals PA and Pa of the incremental encoder, a ball detection signal Pu
, Pv, and P are generated and used, and FIG. 3 shows each signal Pu for θ2.

Pv and Pw are shown. This signal Pυ, Pv.

The rising edge and falling edge of P, ,
They are attached so as to match the respective values of θ shown in the figure.

Next, an example of ball detection using this signal will be given.

First, when the power is turned on, the signal level of each of the signals Pu, Pv, and Pw is read to determine whether it is at H or not. Next, for example, if it is in a zone of O to -π, the intermediate position -π of the zone is set to θ°2. Here, θ2 is the position of the ball itself, and θ°2 is the ball detection position. And for now, this θ° engineering and P
A, PR is used to detect the ball position and control the motor. At this time, the detection error θ2-θ' of the ball position becomes -π at the maximum, and the power factor is approximately 87% at the minimum.
The motor has a value that can be sufficiently controlled. Then, the motor rotates and the first signals PIJ, PV are generated.

02 is detected from the other two signal levels when any rising edge or falling edge of Po is detected. As shown above, when the power is turned on, the ball is located in the 0 to -π zone, and when the sled rotates in the positive direction, the falling edge of the signal Pw is first detected. Since the signal PU at this time is at H level and the signal Pv is at L level, 02 can be detected as 1 - π, and when this signal Pw falls, θ°2 is reset to -π. After that, the pulse signal PA is output from the incremental encoder.

By PR, 02 is detected from equation (3). Therefore, from this point on, the motor can generate torque with a power factor of 100%. θ with respect to θ2.

If the phase is always advanced by 1π, the torque T can be calculated using the ratio measurement number K as T=KII+, ...(
4).

[Problems to be Solved by the Invention] The conventional synchronous AC servo motor drive device described above requires a ball sensor that outputs signals Pu, Pv, and Pw to detect balls, and is expensive and requires A transmission cable is also required, which has the disadvantage of poor reliability. If an absolute encoder is used instead of an incremental encoder, 02 can be detected immediately when the current is turned on, but it is more expensive than an incremental encoder. Another method is to fix the electrical angle of the current and 1. When a current is passed through the windings with, for example, the rated current, the motor rotates until the power factor reaches 0% and then stops. At this time, θ2−θ. Therefore, θ1 can be detected, but since the motor rotates by a maximum of π when current is passed through the windings, it cannot be used in applications where it would be a problem if the motor rotates when the power is turned on.

The object of the present invention is to eliminate the need for the above-mentioned ball sensor,
To provide a synchronous AC servo motor drive device that detects a ball position using only an inexpensive incremental encoder and hardly rotating a motor.

[Means for Solving the Problem] When the synchronous AC servo motor drive device of the present invention is activated, it generates a current electrical angle, continuously changes it from O to 2π, and repeats this operation to generate a current electrical angle. A generator, when activated, generates and continuously outputs a preset peak current command, and every time a current electrical angle of 2π is input from the current electrical angle generator, the command value of the peak current command is set. A peak current command generator that adds a predetermined increment to the peak current command and continuously outputs it, and a command value of the peak current command input from the peak current command generator and a current electrical angle input from the current electrical angle generator. The current command distributor that generates and outputs the 3-phase current command and the pulse signal output from the incremental encoder attached to the motor are counted up when the motor is rotating in the forward direction, and up-counted when the motor is rotating in the reverse direction. The up/down counter counts down, and the count value from the up/down counter is compared with a preset setting value, and when the absolute value of the count value exceeds the setting value, the latch signal and the sign of the count value are A latch circuit that continuously inputs the current electrical angle from the current electrical angle generator and latches the current electrical angle using the latch signal from the comparator; When the sign input from the comparator is positive at the corner, m
-, and when the value is negative, -π is added, respectively.

[Operation] When the current electrical angle generator is activated, the current electrical angle θ
When the peak current command generator is activated, the peak current command generator commands the peak value of each phase current of the motor. A current command ■ is generated and output, and the current command distributor is a current electrical angle θ. and peak current command ■ A and Yori formula (
1) Each phase current■. + Generate current commands for each phase (Iu, Iv, I) corresponding to V+IW. The current amplifier receives these current commands and drives a three-phase synchronous AC servo motor.

0 Therefore, first, a peak current command of the minimum value is given to the stationary motor. Even if the motor is applied, the motor will not start due to frictional torque. Next, every time the current electrical angle becomes 2π, the peak current command 1. As the command value of is increased little by little, the motor torque gradually increases, eventually overcoming the friction torque and rotating in the positive or negative direction according to the relationship between the initial ball position and the current electrical angle at that time. At this time, the incremental encoder attached to the motor also rotates at the same time and outputs a pulse signal, so by counting the number of pulses and comparing it with a small preset value, the slight rotation of the ball position can be detected. It can be detected along with its direction. Therefore, the current electrical angle θ°0 at this point
If latched by a latch circuit, the latched electrical angle θ”
0 is the current electrical angle corresponding to the case of approximately 100% power factor, and thus the initial ball position θ゛2 of the motor is at a phase difference of −π. Which of ±−π is 1 can be determined by the sign of the count value, and θ“6
The value added to is θ゛2. Thereby, the subsequent ball position θ2 can be detected by counting the pulses of the incremental encoder.

[Example] Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a ball position detection circuit included in an embodiment of the synchronous AC servo motor drive device of the present invention, and FIGS. 2(a) and (b) respectively show the current of FIG. Electrical angle θ of the current generated by the electrical angle generator 2. 1 is a graph showing the peak current command ■1 generated by the peak current command generator 1. In this embodiment, it is assumed that a two-pole motor and a 1000 pulse/rotation incremental encoder are used.

After the peak current command generator 1 and the current electrical angle generator 2 are activated, they each issue a peak current command ■ which commands the peak current value of each phase current IU+2Iv, IW.
, and generates an electrical angle θゎ.

The current command distributor 3 receives the peak current command 1. output from the peak current command generator 1. and the current electrical angle θ output from the current electrical angle generator 2. From this, the current command for each phase corresponding to equation (1) is ■. ,I,,I, is output. The three-phase current amplifier 4 receives current commands 1. ,Iv,I.

3-phase current according to■. , Iv, and Iw are applied to each winding of the three-phase synchronous AC servo motor 5. The up/down/counter 7 counts up the pulse signals PA and PB output from the incremental encoder 6 attached to the motor 5 in ten directions when the motor 5 rotates forward, and counts down in one direction when the motor 5 rotates in the reverse direction. . The comparator 8 compares the count value input from the up/down counter 7 with a preset set value, and outputs a latch signal and the sign of the count value when the count value exceeds the set value. The latch circuit 9 latches the current electrical angle θ° inputted from the current electrical angle generator 2 based on the latch signal from the comparator 8. The adder 10 adds the sign of the count value inputted from the comparator 8 to the current electrical angle θ''8 latched by the latch circuit 9 to obtain the electrical angle θ of the initial ball position.

shall be.

Next, the operation of this embodiment will be explained.

When the current electrical angle generator 2 is activated, the current electrical angle generator 2 is activated as shown in FIG.
As shown in a), the current electrical angle θ. The output is continuously increased from 0 to 2π, and when it reaches 2π, the same output operation is repeated from 0 again. When the peak current command generator 1 is activated, as shown in FIG. 2(b), the peak current command generator 1 first generates a peak current command 1. corresponding to a minimum current value increment. After that, each time an electrical angle 2π is input from the current electrical angle generator 2, the peak current command I2. is increased by a predetermined increment.
13... are output in sequence.

Therefore, assume that the ball position is initially at -π,
Peak current command Ill I2+ x3-... is as follows
Set as shown in 4.

T=KI, 5in(θ2-θF) ・(
7) The absolute value of the generated torque T reaches its peak at sin
(θ2-θ.) is ±1, so θ2 is I here.

is the rated current of the motor 5. When the operation starts, the electrical angle is initially changed from 0 to 2π with respect to the peak current command (1), and the current commands (2) and (2) for each phase are output from the current command distributor 3 at this time.

Iv and I, respectively. The torque T at this time is T, = KI, ... (8
) Since this torque T1 is small, either the motor 5 does not rotate due to frictional torque, or the peak current command 1. As the value of is gradually increased to II, I2, 13, the peak value of the generated torque also gradually increases, and eventually the generated torque becomes larger than the friction torque and the motor 5 starts rotating. Since the electrical angle is varied from 0 to 2π, the peak of the generated torque appears first. The generated torque T of the motor 5 is expressed by the following equation using a proportionality constant K, where θ is the electrical angle at the ball position of the motor 5.

5 Raw torque is P! When the torque becomes larger than J Muku, motor 5
begins to rotate and the encoder 6 outputs incremental pulse signals PA and PR, and the up/town counter 7 counts this pulse signal PA+pH. In this case, the ball position is at -π and θ. (=-π) is in the delayed phase, so the motor 5 rotates in the opposite direction. Therefore, the up/down counter 7 counts down and the comparator 8 inputs this count value.
outputs a latch signal and the sign (-) of the count value if its absolute value exceeds a set value (a small value such as 2 pulses or 3 pulses). The latch circuit 9 receives the current electrical angle θ'e (Lg
-π), and the adder 10 latches this current electrical angle θ'
Add -π to the sign (-) of the separately input count value and use the following formula (9) to determine θ°2=-π as the first ball position of the motor 5. . Once θ°2 is determined, a normal servo loop is constructed, and the ball position θ', (n) is subsequently determined from the following equation.

However, .theta.', (n-1) is .theta.'2 obtained during the previous sampler, and .DELTA.N represents the change in the feedback pulse between the previous and current sampling.

[Effects of the Invention] As explained above, the present invention uses a peak current command generator or the like to gradually increase the torque in the motor's stationary state and detect the ball position when the motor starts rotating. By calculating and adding the rotation angle of the motor from the number of pulses from the incremental encoder, the ball position can be detected at all times. This has the advantage that the first ball position can be detected without rotating the motor, and it can be used in applications where the motor does not need to rotate too much when the power is turned on.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a ball position detection circuit included in an embodiment of the synchronous AC servo motor drive device of the present invention, and FIG. 2(a) is a peak current command generator 1 in FIG. 2(b) is an output time chart of the current electrical angle generator 2, and FIG. 3 is an output timing chart of a conventional ball sensor. 1... Peak current command generator 2... Current electrical angle generator 3... Current command distributor 4... Three-phase current amplifier 5... Synchronous AC servo motor 6... Incremental encoder 7 ...Up/town counter 8...Comparator 9...Latch circuit 10...Adder I,, I,, Is...Peak current command value θ. ,O゛
...Current electrical angle 9 ...Initial ball position, PR...Value number, Iv, I, ...each phase? Current command, Tv, Iw... Current of each phase

Claims (1)

[Claims] In a synchronous AC servo motor drive device that drives a synchronous AC servo motor by generating three-phase currents according to first and third-phase current commands, when activated, generates a current electrical angle. a current electrical angle generator that continuously changes the current from 0 to 2π and repeats this operation; and a current electrical angle generator that generates and continuously outputs a preset peak current command when activated, and A peak current command generator that adds a predetermined increment to the command value of the peak current command and continuously outputs it each time the current electrical angle 2π is input; The current command distributor generates and outputs a three-phase current command based on the command value and the current/electrical angle input from the current/electrical angle generator, and the pulse signal output from the incremental encoder attached to the motor is used to control the rotation of the motor. The count value is calculated by comparing the count value from the up/down counter with a preset value and an up/down counter that counts up when the motor is rotating in the forward direction and counts down when the motor rotation is in the opposite direction. A comparator that outputs a latch signal and the sign of the count value when the absolute value of If the sign input from the comparator is positive, -π/2 is added to the current electrical angle latched by the latch circuit, and if it is negative, 1/2π is added to the current electrical angle latched by the latch circuit. 1. A synchronous AC servo motor drive device comprising a motor pole position detection circuit comprising an adder and a motor pole position detection circuit.