JPS59117479A - Speed detecting system for servo motor - Google Patents

Abstract

PURPOSE:To reduce the load of a microprocessor by calculating a current loop for the prescribed period and a speed loop for the prescribed period, and calculating the actual speed for each period from the actual current value read out for the prescribed period and the armature voltage command value outputted from the prescribed period. CONSTITUTION:When position detecting pulses P1, P2 do not arrive during the period of a sampling pulse, it is judged as a low speed, and a processor 108a calculates the actual speed (v) on the basis of the armature voltage command (u) obtained by the armature current (i) and the current loop calculation. At this time, the current loop calculation is performed for each period T1, and the armature current is read out at the period T2 of the integer magnification of the period T1. Accordingly, the actual speed is calculated for each period T2 from the armature current for each period T2 and the armature voltage command value for each period T1. At a high speed rotation time, the actual speed (v) is calculated on the basis of the interval T0 of the position detecting pulses.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a servo motor speed detection method for detecting the actual speed with high accuracy when the servo motor rotates at low speed in a servo motor speed control device, and particularly to a method for detecting the actual speed when the servo motor rotates at low speed. This invention relates to a speed detection force formula for a servo motor that detects speed without increasing the load on the arithmetic circuit.

In order to control the speed of a DC motor or an AC motor, it is necessary to detect the actual speed of the motor and compare it with a commanded speed to control the motor. FIG. 1 is a block diagram of a general servo control circuit, and position detection is performed every predetermined amount of rotation of the servo motor 1 from a rotary encoder (position detector) 2 directly connected to the rotating shaft of the servo motor 1. Nokurusu PP and
The difference (position error) from the position command pulse PCMD commanded from the outside is taken by the arithmetic circuit 6 and set in the error register 4. The contents of the error register 4 are converted into an analog voltage by a digital-to-analog converter 5 and inputted to a speed control circuit 7 as a speed command voltage.

On the other hand, from the position detection pulse PP to the speed detection port ll12i6
The actual speed is not detected and input to the speed control circuit 87, and the current four-current control circuit 8 controls the speed of the servo motor 1 based on the speed error between the speed command voltage and the actual speed.

Among such servo control stations, one has been developed in which the speed control loop and current control loop circuits, ie, the circuits from the arithmetic circuit 3 to the current control circuit 8, are operated by a microprocessor. Since a microprocessor performs digital calculations, it is necessary to perform speed detection digitally.

Figure 2 is a diagram showing the configuration of a conventional digital speed detection system.
Figure m6 is an explanatory diagram of the operation. In the figure, 6a is a counter, which is the position pulse H1 number inputted during the sampling period T, and whose divisor value of seven is reset by the sampling pulse SP, and 6b is a register, which is the position pulse H1 number inputted during the sampling period T. The count value of the counter 6a is set, and 9 is a microprocessor, which calculates the four-ball position error with the arithmetic circuit 6 and generates a speed command VC.
It calculates M, obtains the actual speed TSC from the argument value from the register 6b, and outputs the speed error which is the difference between the speed command VCM and the actual speed TSC.

The operation of the conventional M configuration shown in FIG. 2 will be explained with reference to FIG. 6. Since the counter 6a is reset by the sampling pulse SPK ordered at regular intervals, the counter 6a is reset by the sampling pulse SPK ordered at regular intervals. This means that the number of detection pulses is counted, and this number of position detection pulses is set in the register 6b. The microcomputer 9 reads the argument value of the register 6b when each sampling pulse is generated.
b. Through this, the actual speed TSC is obtained, and the speed error i EB-
Calculate and output.

However, such conventional speed detection methods have the following drawbacks.

First, during low-speed rotation, especially when the interval between position detection pulses PP is larger than the sampling period, not a single position detection pulse is input within one sampling period, so speed detection becomes impossible for each sampling period. .

Second, during high-speed rotation, even if the number of position detection pulses PP input during the sampling period is 101, this is the average speed during the sampling period, and the instantaneous speed when the sampling pulse is generated. isn't it. For this reason, the response characteristics of speed control by the microprocessor deteriorate, making it impossible to achieve high responsiveness.

For this reason, the inventor of the present invention has filed an application for a speed detection force formula that eliminates this drawback.

In such a proposal, the position detection pulse P within the sampling period
During low-speed rotation when no P is input, speed cannot be detected from the position detection pulse, so a state transition equation derived from a differential equation based on the physical characteristics of the servo motor is used to Estimate the instantaneous speed at the time of sampling from the current, current, and armature voltage.

- At the time of force and high-speed rotation, the period of the position detection pulse PP input immediately before sampling is used as an argument, and the instantaneous speed at sampling is determined from its reciprocal.

Furthermore, during medium speed rotation, the estimated value of the instantaneous speed obtained using the speed estimation method during low speed rotation is corrected by the instantaneous speed obtained using the speed detection method during high speed rotation.

As a result, the microprocessor can obtain an instantaneous sampling speed from low speed to high speed 1.

On the other hand, when a servo motor speed control device is controlled by a microprocessor, the microprocessor performs a speed loop calculation that calculates a current command from the difference speed between the command speed and the actual speed of the servo motor, and a current command There is a method that performs at least a current loop calculation that calculates a command to the current drive circuit of the servo motor based on the differential pressure between the current drive circuit and the armature current of the servo motor. In order to achieve desirable operating characteristics of a servo motor, the response characteristics of the current loop are required to be faster than those of the speed loop, but if the speed loop is calculated at the sampling period required for the current loop, , due to the overload of the microprocessor,
As shown in Figure 4, the current loop calculation and the speed loop calculation are controlled separately and the sampling period of each is made different, thereby reducing the load on the microprocessor and achieving the desired response characteristics of the current loop. A satisfactory method has already been proposed. That is, the actual rotation speed V of the servo motor 1 is detected in the speed control loop shown in FIG.
The difference between MD and MD is calculated using the performance Fa 0PC1, and the obtained difference speed is used as the current command Is using the speed loop performance 1R3VLC.
After changing the current control loop, servo motor 1
A calculation unit 0PC2 calculates the difference between the current i and the actual current i flowing through the servo motor 1, and a current loop calculation circuit CLC performs calculation 1-1 to amplify the power of this difference N current and apply it to the servo motor 1. The operating cycle is such that the cycle TI of the current loop is smaller than the cycle T2 of the speed loop, for example, T2=nT, so that the response of the current loop is faster.

If the previously proposed speed detection method during low-speed rotation is used in a speed control device based on the operation of such a mital processor, since the current, root current, and voltage commands in the current loop are used, It is necessary to perform the speed estimation calculation at a period of Ill. However, since the speed loop operates in period T2, the speed estimate is required in period T, and is not needed in other periods, so calculating in period T would be wasteful, and would actually increase the microprocessor's capacity. This has the disadvantage of requiring additional processing time.

Therefore, an object of the present invention is to provide a speed control device that executes speed loop calculations and current loop calculations at different intervals.
An object of the present invention is to provide a speed detection method for a servo motor that can perform speed estimation calculations in the calculation period of a speed loop using the output of a current loop when the servo motor rotates at a low speed.

Hereinafter, one embodiment of the present invention will be explained in detail.

First, the speed estimation method for G during low speed rotation, which has been proposed, is adopted as the fifth method.
This will be explained using figures.

FIG. 5 is an explanatory diagram of the principle of speed detection during low-speed rotation according to an existing proposal, and is a block diagram showing the characteristics of the servo motor 1 using a transfer function. In the figure, U is the electric 1st arm voltage command, i
is the armature actual current, ■ is the actual speed, Hill is the load torque, Ke is the back electromotive force constant of the servo motor, Kt is the torque constant of the servo motor, RaFi armature DC resistance, Mu is the armature inductance, J is the motor and This is the inertia of the load. Here, T is a hold circuit and T is a sampling period.

If we obtain the differential equation based on the physical characteristics of the servo motor from Fig. 5, we will convert it to a discrete value format to be processed by a microprocessor.

By deleting and transforming the load torque Tt and [kl from equation (5), looking at equation (6), we see that the armature current detection value 1 (k-1
), 1(kl, electric machine pre-voltage, and pressure command value u(k-1)), the estimated value of the actual speed V of the motor can be detected.

However, in order to estimate the speed using equation (6), armature current detection value 1 (kt), armature frost pressure command value u (kl
Since is an output in the current loop, it is generated every calculation period of the current loop, and it is necessary to perform speed estimation calculation accordingly. For this reason, calculations for the speed loop must also match the period of the current loop, which increases the load on the microprocessor.

For this reason, the present invention is improved so that speed estimation calculation can be performed in the calculation period of the speed loop.

FIG. 6 is a diagram showing the relationship between the calculation cycles of the speed loop and the current loop according to the present invention.

Here, if the sampling period T1 of the frost and flow loop calculation is T, and the sampling period T2 of the velocity loop calculation is 4T, the state estimation equation at time (k+4) is obtained by transforming equation (4) as follows: become.

-FP(2T) Q(T)u(k+1)+P(3T)
Qffl u (kl-1(R(Tl + P(TI
Rke7+P(2T)EJTl+P(sT)Kun DT k
)... (7) However, Tt, (k+3)=TL(k+2)=Tb(
k+1)-Tc(kl), and it is assumed that there is no variation in the load torque - during a period of 4T.

If Tt, (kl are eliminated in the same manner as the expansion to equation (5) above,
It is a coefficient determined from the elements of F-.

Looking at equation (8), the estimated speed v (kl, armature current value 1 (kl, armature current value r at (k+4)) at time k (k+4)p k, (k+1),
Armature voltage command value u(k
l, u (k+1), u (k+2).

The estimated speed v(k-1-4) at time (k+'l) can be obtained from u(k-1-3).

That is, the estimated speed can be obtained by calculating the signature every 4T, which is the nine cycles of the velocity loop.

Next, a configuration for realizing the present invention will be explained.

FIG. 7 is a circuit diagram of an embodiment of the present invention, in which a single microphone computer performs a speed loop and a current loop.

In the figure, 101 is a rotating field type synchronous motor, 108 is an arithmetic control section, and the operations of the arithmetic circuit 0PC1, speed loop arithmetic circuit VLC, arithmetic circuit 0PC2, and current loop arithmetic circuit fj8cLc in FIG. 4 are controlled by a program. This is done through arithmetic operations. The arithmetic control unit 108 includes a processor 10a that operates according to a motor control program.
, a program memory 108b for storing a motor control program, and a data memory j110 for storing data.
8c, an input/output capo for receiving commands from an external device such as an NC device) 108d, and a pulse width modulation circuit 114
A digital/analog (1) A) converter 108e for giving an analog current command to the converter 108e, and a galvanometer 5112U,
Actual phase current Iau, Ia from 112V, 112W
First, a position code indicating the rotational position α of the field pole of the synchronous motor 101 is loaded from the analog-to-digital (AD) converter 108f for receiving v, Iaw and converting it into a digital value, and the pulse cog 113, and the position code indicating the rotational position α of the field pole of the synchronous motor 101 is loaded. A counter 10 that counts rotation pulses P, , P2 issued from the descending pulse coder 113 every time the synchronous motor 101 rotates by a predetermined angle.
8g, an input/output capacitor 108i which receives the output of a low speed/high speed discrimination circuit to be described later, and an address/data bus 108h for connecting these. The pulse cog 113 generates a position code indicating the position of the field pole of the synchronous motor 101 and a rotation pulse output every time the synchronous motor 101 rotates by a predetermined angle. 114
115 is a pulse width modulation circuit, 115 is an inverter controlled by the output signal of the pulse width modulation circuit, 116 is a 6-phase AC power supply, and 117 is a known rectifier circuit that rectifies three-phase or current into DC, including a group of diodes 117a and a capacitor 117b. have. The pulse width modulation circuit 114 generates a sawtooth wave STS/4E times N as shown in FIG.
5TSG and ratio M? '4 COMU, COMV,
It consists of COMW, NO'T, ~N0T3, drivers DV, ~DV, and an inverter I.
NV has six power transistors Qq and diodes D1-D. Pulse width modulation 5 Each PWM comparator COMU COMV COMW compares the amplitude of the sawtooth wave signal STS and the three-phase AC signal Iu, Iv, Iw, and when Iu, Iv, and Iw are thicker than the STS value, When tL171 is small, llO7' is Jc'
FL output it. Therefore, focusing on iu VC, the current command iuc shown in FIG. 9 is output from the comparator COMU. iu, iv.

Three-phase current commands iuc, ivc, and iwc that are pulse width modulated according to the amplitude of iw are output. and,
These three-phase current and current commands IUC, IVC, and IWC
are not gates N0T1 to N0T3, driver DVI
~ DV6 and inverter drive signal SQ, -5Q6
It is output as , and inputted manually to the inverter 115 . These inverter drive signals S input to the inverter 115
Q1~sQe are power transistors Q, ~Q, respectively
6 is input to the base of the power transistor Q~Q6.
On/off control is performed to supply three-phase current to the synchronous motor 101. Reference numeral 118 denotes a low speed/high speed discrimination circuit, which determines low speed/high speed from the position detection pulse PP, and also determines the above-mentioned interval T. The circuit shown in FIG. 10 includes a flip-flop FF that is set by the sampling pulse SP, reset by the position detection pulse PP, and outputs a low/high speed discrimination signal FFQ, and a clock. A counter CT that divides the pulse CL and is reset by the position detection pulse PP and measures the interval between each position detection pulse PP, and a first register in which the measured value of the counter CT is set every time the position detection pulse PP arrives. RECh and
It has a second register REG 2 whose contents are set every time the sampling pulse SP arrives, and if the position detection pulse PP does not arrive within the sampling period 4T from the Noritsubu flop I'F. When even one position detection pulse PP arrives, a high-level ("1") low-speed discrimination output is generated, a low-level ("0") high-speed discrimination output is generated, and a sampling pulse SP is output from the second register EG2. The interval T between the previous position nox PP is the output trough.

Next, regarding the operation of the embodiment configuration shown in FIG. 7, the synchronous motor 10
Assuming that 1 is rotating at low speed, high speed rotation command C■
Let's explain what happens when input.

(2) If the position detection pulse PP does not arrive during the period of the sampling pulse SP, the flip-flop FF of the low speed/high speed discrimination circuit 118 outputs a high level output, so that the processor 108a performs an input/output capo) 108i.

This is read every sampling period via the bus 108h, and it is determined that the rotation is at a low speed, and the speed estimation equation (8) for low speed rotation is executed. That is, at time (k+4),
Data memo IJ 108CK The estimated actual speed V (kl) calculated at the time point is stored in advance in the armature current i [kl, at time k. Note that the armature current i lkl is the actual phase current Iau, It is obtained from Iav and Iaw by the following formula.

Moreover, the data memory 108CK is (k+1), (
k+2>.

Electric machine pre-voltage and pressure command u (kl, u
(k+1).

u (k+2) and u (k-1-3) are stored. Here, it is obtained from the D/A converter command values iu and iviv at the time utAiA by the following equation.

uri1±(iu'+ i v2+ 1w2)2
α0 Therefore, the processor 108a first obtains the actual phase current Iau (k+a) at time (k+4) from the AD converter 108f.

1 (k-1-4) is deduced and stored in data memory 1080.

Next, processor 108a includes data memory 108c.
v(kl, i[kl, u(kl, u
(k-1-1), u (k+2).

Read u (k+3), i (k+4), and
8) Execute the expression.

In this case, ψ11 to ψ24 in equation (3). Δ0. Since Δ2 is a characteristic of the synchronous motor 101, it is determined in advance through experiments, etc., and is stored as a fixed value as a parameter of the control program. Therefore, by calculating ff1 (8), (
Actual speed v (k+a) (=RV(k
+4) ) can be found.

(Actual speed operation step at low speed).

On the other hand, if even one position detection pulse PP arrives within the sampling period T2 of the speed loop, the low speed/high speed discrimination circuit 1
Since the output of the 18 flip-flops FF' is a low level output, the processor 108a has an input/output capo of 1 osi at each sampling period T2.

108h is read and it is determined that the rotation is medium speed or high speed. Next, the processor 108a reads the interval % from the second register REG2 of the low speed/high speed discrimination circuit 118, and determines whether the speed is medium speed or high speed. That is, the interval T. is T2/n
If it is above Tsuka, it is judged to be medium speed, and if it is below, it is judged to be high speed. Here, n is 2 to 3. If it is determined that the speed is high, the actual speed is determined as follows.

That is, since a large number of position detection pulses PP are input within the sampling period T at high speed, the interval between the position detection pulses PP immediately before each sampling pulse is measured. 1st
In Figure 1, the interval % between the position detection pulse Pn and Pn-1 immediately before the sampling pulse Sn is measured, and the motor speed v
(k), v (kl = − T.

Find it by

Therefore, the instantaneous velocity 1 m before the zumbling pulse can be obtained.

Also, since there is unevenness in the rotational speed, the interval between the bare number of position detection pulses immediately before the sampling pulse, for example, the interval T between the position detection pulses Pn-s and Pn-2 in FIG.
2. Interval T1 between position detection pulses Pn-2 and Pn-1, and interval T between position detection pulses Pn-1 and Pn. Find the average value TM using the following formula.

TM = , (TO+'f'l +T2)
αηConverting this into a general equation, we can substitute TK in the second equation to find the speed using the following equation.

v(k)=TM(Ll That is, at normal high speeds KH (7+ formula may be used, but at extremely high speeds, the interval T of formula 90.

becomes very small, and when this is counted using clock pulses, the interval between clock pulses has a significant influence. Therefore, the speed may be detected by using the above-mentioned formula @ and formula α. (High-speed actual speed calculation step Next, the processor 108
If a is determined to be medium speed rotation, the actual speed is calculated as follows.

In the speed detection method using position detection pulse PP, speed detection is possible if even one position detection pulse PP is input within one sampling period T2, but this position detection pulse may come at the beginning of the cycle or In some cases, it may come to the end of , and it cannot be said to be the instantaneous velocity at the time of sampling pulse generation. Similarly, when two to three one position detection pulses PP are input within one sampling period T2, it cannot be said that the speed is instantaneous. Therefore, during medium-speed rotation when one to several position detection pulses PP are generated within one sampling period T, the instantaneous speed estimation method (Equation (8)) during low-speed rotation and the actual speed detection method during high-speed rotation are used. (Equation (a)) is combined to find the instantaneous speed. In other words, during medium speed rotation, the estimated speed obtained using the instantaneous speed estimation method is corrected by the actual speed obtained using the actual speed detection method to obtain the instantaneous speed.
It is given by the following formula.

K is a constant number, and 0<K<1.

Incidentally, the constant may be one pair, or may be changed depending on the number nK of position detection pulses PPO within one sampling period.
For example, if n-1 = 0. x.

=0.5 when n=2. For n=3, K=0.8
It can be done.

Therefore, the processor 108a executes a low-speed actual speed calculation step and a high-speed calculation step, each of which includes va (k+
4) Determine -, and then execute equation (b) to determine the actual speed v(k+a) at the middle speed rotation T0. (Actual speed calculation step at medium speed).

■Next, enter/output capo) 108d, bus 108h.
The input command speed cv and the obtained actual speed RV (kl
The processor 108a calculates the difference between the two and performs proportional integration shown in the following equation to calculate the amplitude command l5(k+4).

Incidentally, the performance result Is of the 00 type corresponds to the amplitude of the city 1 machine current. Also, when the load fluctuates or the speed command changes, the speed error ER (=Vc - Va) increases, and the armature current amplitude Is also increases accordingly.

As Is increases, a large torque is generated, and this torque brings the actual speed of the motor to the commanded speed. (Amplitude command calculation step) 5 Furthermore, in the data memory, v (kl of 08 e is changed to v(k-1-J), 1(kl
is updated to 1(k-)-4). (memory update step).

The above is the velocity loop calculation step, which is performed every sampling period T as shown in FIG.

Next, the processor 108a calculates, from the count value of the counter 08g, a digital value of SINα indicating the rotational position 2π of the field pole of the synchronous motor 01, and a digital value of 5IN (at α+) indicating the rotational position 14 of the field pole of the synchronous motor 01. The value is stored in the data memory 1080 and retrieved from the crab table. Using this value, the processor 08a calculates three-phase current commands Iu, Iv, and Iw from the following equations.

(Current command wave layer step).

■Furthermore, the processor 08a has galvanometers 112U, 11
2V.

Actual phase current Iav, Iaw Ia obtained from 112W
u was digitized by AD converter ID8f, @East current was changed to 108h, and the reading was increased by 9. The above-mentioned three-phase current commands Iu, Iv, Iw and the actual phase currents 1av, Iav<
The difference ER with Iau is calculated, and the proportional-integral calculation shown in the following equation is performed to obtain command values iu and iv to the DA converter 108e.

(Command value calculation step).

Next, the processor 10a calculates the actual speed Va VC obtained in the speed performance step of the speed loop described above, and the coefficient k described above.
Multiply by f to obtain the speed compensation output ■CO, and subtract it from the command values iu, iv, and iw to the 1)/A converter mentioned above.
Compensated command values iu, iv to the 1)/A converter
, get iw.

This is provided to cancel the speed feedback to the current loop due to the back electromotive force of the synchronous motor ioi.
The characteristics of the current loop are made independent of the speed of the synchronous motor 101, and the speed loop and current loop are controlled independently. (
Compensation Step) Next, the processor 101 calculates U(
k-1-4), and u (
U(k-1-4)l'i: Update kl. (Frost 5 machine voltage command calculation step) The above is the current loop calculation step, which is constantly performed at the sampling period T in FIG. 6.

Therefore, at time (k+s), the data memory 1080 has the armature voltage commands u (k-1-4), u (
k+5).

u(k+6) and u(k+7) are stored.

The compensated D/A converter command values iu, iv, iw thus obtained are sent by the processor 108a to the DA converter 108e via the node 108h, where they are analog-converted and sent to the pulse width modulation circuit 114. Then, in the same way, the three-phase current of the synchronous motor 101 is suddenly increased 115.
Sent from.

In the above embodiment, a synchronous motor was used as an example of a servo motor, but it can also be applied to other current motors or blood flow motors, and the current loop and speed loop are performed in one calculation control section. , this may be performed by separate arithmetic control units.

Further, the pulse width modulation circuit 114 is configured with a timer, and the processor 108a issues DA converter commands iu and iV.

It is also possible to pulse width modulate iw, output a digital pulse width modulation command, directly operate the timer, and send the pulse width modulation signal to the inverter 115.

In addition to Oi explained above, according to the present invention, the speed control of the servo motor is performed in which the control unit performs current loop calculation at a period T1 and performs speed loop operation at a period T2 which is an integral multiple of the period T1 to control the speed of the servo motor. In the device, in order to obtain the actual speed at low speed, the actual current value (armature current value) for each period T,
Since the computation is performed every cycle T2 from the armature pressure command value every cycle T, it is possible to estimate the actual speed at low speed in the speed loop computation that operates at the cycle T2. In this dispute, the calculation of the actual speed is performed using the period T of the current 4-current loop.
1 does not have to be performed, the load on the control unit is reduced,
Moreover, the speed detection wave W can be incorporated into the speed loop dance, and the processing time for the first part can be shortened.

In addition, even if the speed loop calculation is performed at the period T, the instantaneous speed at the time of sampling can be detected, which has the effect of improving the response characteristics of the speed loop.Furthermore, since the speed can be detected at the period T2, the speed control loop There is also an effect that the load for calculation is reduced, the period T1 of the current required loop is shortened, and the response characteristics of the current loop are improved.

Although one embodiment of the present invention has been described, the glaze may be modified within the spirit of the present invention, and these modifications are not excluded from the scope of the present invention.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a general servo control circuit, Figure 2 is a configuration diagram of a conventional speed detection method, Figure 3 is an explanatory diagram of the operation of the configuration shown in Figure 2, and Figure 4 is based on a previously proposed microprocessor. An operational block diagram of the speed and current loops, Fig. 5 is a diagram explaining the principle of speed detection during low speed rotation as previously proposed, Fig. 6 is a diagram showing the relationship between calculation cycles according to the present invention, and Fig. 7 is a circuit diagram of an embodiment of the present invention. , FIG. 8 is a block diagram of the main parts of the structure shown in FIG. 7, FIG. 9 is an explanatory diagram of the operation of the structure shown in FIG. 8, and FIG. 10 is a block diagram of the main parts of the structure shown in FIG.
FIG. 11 is an explanatory diagram of the operation of the vehicle shown in FIG. In the figure, 101... motor, 1o8... calculation control unit,
112U112V, 112W... Galvanometer, 115...
・Inverter. Patent applicant Fanuc Co., Ltd. agent Patent attorney Minoru Tsuji and two others Figures 4, 5, /-Figure 6

Claims (2)

[Claims] (1) A detector that detects the actual current flowing through the servo motor, an electric and blade drive circuit of the servo motor, and an amplitude command is obtained based on the speed difference between the speed command and the actual speed of the servo motor. a control unit that performs a speed loop calculation to obtain a current command from the detected amplitude command, and a current loop calculation to obtain an armature voltage command from the difference between the current command and the detected actual current; The current loop calculation is performed every cycle T, the armature voltage command is output, and the speed loop calculation is performed every cycle T.
In a speed control device for a servo motor which is executed at a period T2 which is an integer multiple of 1, and which supplies the armature voltage command to the power drive circuit, the control unit controls the actual current value read from the detector every period T2. and the electric machine pre-charge output every period T,
A servo motor speed detection method characterized by calculating an actual speed every cycle T2 from a pressure command value. (2) The calculation of the actual speed is based on the actual speed calculated one sampling period before, the actual current value one sampling period before,
A speed detection method for a servo motor according to claim (1), characterized in that the control section performs the detection using the actual current value of the current sampling period and the armature voltage command value for each period T. .