JP3213796B2 - Servo motor controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a servo motor control device such as a digital servo control device.

[0002]

2. Description of the Related Art A conventional servo motor control device will be described below. The servo motor control device detects the speed of the servo motor in each speed control cycle and controls the speed by feeding back the detected speed. In a servomotor including an encoder, the speed is detected by measuring the number of output pulses of the encoder for each speed control cycle.
At a low speed in which an output pulse of the encoder (hereinafter simply referred to as an output pulse) cannot be obtained in each speed control cycle, the speed is obtained as the reciprocal of the time interval value of the output pulse. In the speed control at such a low speed, in the speed control period section in which the output pulse is obtained, the speed obtained from the speed control is used, and the speed control in which the output pulse is not obtained
In the cycle section, the value used in the previous speed control cycle section is used. However, when an encoder with a small number of pulses is used in such a means, the speed sampling delay time increases at low speeds, and the control system becomes unstable.
Therefore, there is a means for estimating and using the speed during a speed control period in which an output pulse cannot be obtained at a low speed.

FIG. 2 is a block diagram showing a configuration of an example of a servo motor control device having means for calculating an estimated speed. In the drawing, 1 is a servo motor, 2 is an encoder that outputs a pulse train of a number proportional to the rotation speed of the servo motor 1, 3 is a quadruple circuit that quadruples the pulse train, 4
Is a speed calculating unit for calculating the speed of the servo motor 1 from the pulse train multiplied by 4, 5 is an estimated load torque calculating unit for estimating load torque, 6 is an estimated speed calculating unit for estimating speed, and 7 is a speed for each speed control cycle. A selection switch that switches and selects the output of the calculation unit 4 or the output of the estimated speed calculation unit 6 and feeds it back to the speed control unit 8 as a speed feedback signal. 4 is selected, otherwise, the output of the estimated speed calculator 6 is selected. Speed control unit 8 and the command speed instructed from the outside, it commands the current value of the servo motor 1 corresponding to the difference between the detected velocity or estimated velocity fed back via the selector switch 7. 9 is a current detector 1
A current control unit that controls the current value according to the difference between the detected current of the servo motor 1 detected at 0 and the current command value.

[0004] In the above structure, the speed control unit 8 or Re not have the estimated speed calculated by the detection rate or estimated velocity calculation unit 6 is calculated based on the pulse output of the encoder 2 is fed back, a difference between the speed command The current control unit 9 controls the current so that the detected current of the servomotor 1 detected by the current detector 10 does not differ from the current command value, thereby controlling the servomotor 1. Is controlled so that the speed becomes the speed command value.
At this time, when the speed cannot be detected by the output pulse of the encoder 2 in the speed control cycle section, the estimated speed is calculated by the estimated load torque calculation unit 5 and the estimated speed calculation unit 6, and the estimated speed is set via the selection switch 7. Feedback control the speed.

Hereinafter, the principle of calculating the estimated torque will be described. First, a description will be given to the estimated load torque calculating unit 5. The estimated load torque calculation unit 5 estimates the load torque when the speed can be detected from the output pulse of the encoder 2 and constantly updates and maintains the estimated load torque value in case an output pulse cannot be obtained. The estimated load torque is calculated by subtracting the acceleration torque from the generated torque generated by the servo motor 1 as the load torque.
The generated torque is obtained from the current value detected by the current detector 10 at the time of an output pulse or at a predetermined time between two output pulses. The acceleration torque can be obtained when the output pulse of the encoder 2 is obtained.
Is divided by the output pulse interval time, and the result is multiplied by an inertia moment value obtained by summing the inertia moment of the servo motor 1 and the load inertia moment. The estimated load torque calculator 5 does not operate when an output pulse is not obtained, and holds the last estimated load torque value. As another method for obtaining the estimated load torque, there is a method using a state estimator for estimating the load torque from the speed of the servomotor and the generated torque.

Next, the speed estimation operation of the estimated speed calculation section 6 will be described. This speed estimation is equivalent to the reverse of the load torque estimation. That is, the acceleration torque is obtained by subtracting the estimated load torque calculated when the output pulse was obtained by the estimated load torque calculation unit 5 from the torque generated by the servo motor 1. The amount of speed change during the speed control cycle by dividing by the moment of inertia, that is, the amount of acceleration, is obtained, and the actual speed known when the output pulse is finally obtained is used as an initial value, and the amount of acceleration is used for each speed control cycle section. By accumulating sequentially, the speed control cycle from which no subsequent output pulse can be obtained
The speed in the period section. When an output pulse can be obtained from the encoder 2, the control may be performed again at the detection speed.

[0007]

In such a conventional means using the estimated speed, it is necessary to reduce the error in the estimated load torque as much as possible in order to reduce the error in the speed estimation. For that purpose, it is necessary that the accuracy of the speed of the motor and the accuracy of the generated torque input to the estimated load torque calculation unit be sufficiently high.

However, the encoder used for detecting the speed of the motor often has a pulse interval error. In this case, the speed of the motor input to the estimated load torque calculating section 5 includes an error. For this reason, an error occurs in the estimated load torque, the accuracy of speed estimation is deteriorated, and speed control at low speed cannot be stabilized .

[0009] The present invention is intended to solve the above problem, the encoder if there is a pulse interval error pulses outputted to estimate the speed of the motor accurately can also stabilize the speed control in the low speed Rusa Bomota control It is intended to provide a device.

[0010]

According to the first aspect of the present invention, a pulse interval error of an encoder provided in a servomotor is provided.
A speed calculation means for calculating from the output pulses of the n pulse period the speed of the servo motor as a detected speed with the
Said servo motor each time the output pulse is generated n times, and the estimated load torque calculating means for exiting calculate the estimated load torque by said detected speed and the current value of the servo motor, the estimated load torque and the said current value Estimated speed calculating means for calculating an estimated speed of the motor, and speed control means for controlling the speed of the servo motor in a predetermined speed control cycle in response to an external speed command, wherein the detected speed is controlled within the speed control cycle section. If There can be calculated, the detection rate calculating said by <br/> the estimated load torque calculation hand stage Ri推 constant load torque as well as speed controls the servo motor so that the speed command by the speed control unit Update the speed control cycle
When said detected speed can not be calculated in the period within the interval, the by estimated speed calculation means calculates the estimated speed from the previous Ki推 constant load torque, the speed control means is a servo motor so that the estimated speed is the speed command Is a servo motor control device that controls the speed of the servo motor.

[0011] As a result, the output pulse of the encoder path
The speed control accuracy can be improved by reducing the influence of the loose interval error.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, an encoder provided in a servo motor has a pulse interval error having an error.
A speed calculation means for calculating from the output pulse of the pulse period the speed of the servo motor as a detection speed, the output pulse
Each time the scan occurs n times, and the estimated load torque calculating means for exiting calculate the estimated load torque by said detected speed and the current value of the servo motor, the said current value and the estimated load torque of the servo motor Estimated speed calculating means for calculating an estimated speed, and speed control means for controlling the speed of the servo motor in a predetermined speed control cycle in response to a speed command from the outside, wherein the detected speed is within the speed control cycle section. If can be calculated, the detection rate is calculated and updated the Ri推 constant load torque due to the estimated load torque calculation hand stage as well as speed controls the servo motor so that the speed command by the speed control means, said If a speed control period in the interval the detected speed can not be calculated, to calculate the estimated speed from the previous Ki推 constant load torque by the estimated speed calculation means,
It said speed control means is a servo motor control device for speed control of the servo motor so that the estimated speed is the speed command, also, the present invention according to claim 2, estimated
The load torque calculation means determines that n = 4 and the encoder pulse
Output pulse of 4 pulse cycle with interval error occurs 4 times
Ru servo motor controller der according to claim 1, wherein which is adapted to calculating calculates the estimated load torque to Rugoto.

Hereinafter, embodiments of the present invention will be described.

[0014]

EXAMPLES (Example 1) Hereinafter, with reference to the drawings with the embodiments of the servo motor control apparatus of the present invention. This embodiment relates to claims 1 and 2.

FIG. 1 is a block diagram showing the configuration of this embodiment. The same components as those of the conventional example shown in FIG. 2 are denoted by the same reference numerals . The difference between the servo motor control device of the present embodiment and the conventional example shown in FIG. 2 is that the estimated load torque calculating section 5 generates the output pulse of the quadruple circuit 3 n times.
Speed calculated by the speed calculation unit 4 and the current detector 1
0 to calculate the estimated load torque
It is to have done. In the present invention, the output of n pulse periods
A force pulse is a cycle of the same pulse consisting of n pulses.
It means a pulse train output periodically. In this embodiment,
Encoder 2 generates a pulse in one pulse cycle and multiplies by 4
Through the circuit 3, an output pulse having a 4-pulse cycle
And four pulse periods with n = 4 in the present invention.
It is configured to obtain an output pulse, but has a quadruple circuit 3.
First, encoder 2 outputs pulses with a 4-pulse cycle
It may be the case.

The operation of the above configuration will be described. Speed
Output pulse of encoder 2 is obtained in the degree control cycle section
At this time, the speed calculation unit 4 always calculates the speed of the servo motor 1.
Out, that is, the output pulse of the quadruple circuit 3 is generated four times.
The detection speed is calculated for each of the current detectors 10
Always detects the current value of the servo motor 1. Estimated negative
The load torque calculation unit 5 outputs the output pulse of the quadrupling circuit 3 four times.
Each time the detection speed and the current detection of the speed calculation unit 4 are detected,
Calculate the estimated load torque by inputting the detected current of output unit 10
I do. At this time, the pulse between the output pulses of the quadruple
Every four even if there is a separation error (arbitrary first and n + 1
Calculated because there is no error due to the periodicity in the pulse interval
The detected speed does not include an error. Note that the estimated load
Since the speed input becomes every four pulses,
Need to consider sampling rate for acceleration calculation
Needless to say.

Thus, the output pulse of the quadruple circuit 3 is
By calculating the estimated load torque every four occurrences
Error in the output pulse of the quadrature multiplier 3
Even if the estimated load torque without error can be obtained,
Improve accuracy of load torque and accuracy of estimated speed
be able to.

[0018] In this embodiment, the speed calculator 4 is described to calculate a detection rate from the output pulses of the 4 multiplier circuit 3, it may be calculated from the output pulse itself encoder 2 needless to say No. When n = 4
Has been described, but the present invention is not limited to this.

[0019]

As is apparent from the above description, according to the present invention, even if there is an error in the output pulse interval of the encoder 2,
Since the error of the estimated load torque can be reduced, the speed of the servomotor can be accurately estimated, and the speed control at low speed can be stabilized .

[Brief description of the drawings]

Block diagram showing the configuration of a servo motor control apparatus in Embodiment 1 of the present invention

2 is a block diagram showing a configuration of a conventional servo motor system GoSo location

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Servo motor 2 Encoder 3 4 Multiplication circuit 4 Speed calculation part (speed calculation means) 5 Estimated load torque calculation part (estimated load torque calculation means) 6 Estimated speed calculation part (estimated speed calculation means) 7 Selection switch 8 Speed control part ( Speed control means) 9 current control unit (speed control means) 10 current detector

Continuation of the front page (72) Inventor Kiyoshi Oishi 1-3-3, School Town, Nagaoka City, Niigata Prefecture 5-101 Nagaoka Residence (56) References JP-A-2-307384 (JP, A) JP-A-61- 266086 (JP, A) JP-A-6-327281 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02P 5/00

Claims (2)

(57) [Claims] An encoder pallet provided on a servomotor.
Speed calculation means for calculating the speed of the servo motor as a detection speed from output pulses having an n-pulse cycle having a pulse interval error; and each time the output pulse is generated n times, the detected speed and the current value of the servo motor are calculated. and the estimated load torque calculating means for exiting calculate the estimated load torque, the estimated speed calculation means for calculating an estimated speed of the servo motor by the said current value and the estimated load torque, in response to the speed command from the outside Speed control means for controlling the speed of the servo motor at a predetermined speed control cycle, and when the detected speed can be calculated within the speed control cycle section, the speed control means sets the detected speed to the speed command. the calculated and updated the Ri推 constant load torque due to the estimated load torque calculation hand stage as well as the speed control of the servomotor, the
If a speed control period in the interval the detected speed can not be calculated, to calculate the estimated speed from the previous Ki推 constant load torque by the estimated speed calculation means, said speed control means the as the estimated speed is the speed command Servo motor controller that controls the speed of the servo motor. 2. The method according to claim 1, wherein the estimated load torque calculating means sets n = 4.
4-pulse cycle output with pulse interval error of encoder
The servo motor control device according to claim 1 , wherein an estimated load torque is calculated and calculated every time a pulse is generated four times .