JPH01194884A - Controller for motor - Google Patents

Abstract

PURPOSE:To enable a position error quantity to be quickly converged to come to zero, by determining a position controlling loop gain and a speed controlling loop gain based on a previously set function, according to the position error quantity. CONSTITUTION:Even when a large position error quantity DIFF is generated transiently, the position error quantity DIFF is quickly converged to come to zero. In order to keep the high precision of processed shape, there is provided with a gain determining section 12 by which a position controlling loop gain Kv and speed controlling loop gains P, I are made greater as the position error quantity DIFF gets greater. By the gain determining section 12, the position controlling loop gain Kv is determined based on a function set previously in accordance with the computed position error quantity DIFF, and is set to be a loop gain to be multiplied transferred to a position controlling section 3, and the P and I gains of the speed controlling loop are determined based on the previously set function and are transferred to a speed controlling section 6 and are PI-controlled.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a motor (servo motor) that performs position control or speed control of a motor (servo motor) based on the deviation between a position command value and a detected position value, that is, the amount of position error. The present invention relates to a control device.

(Prior Art) An example of the configuration of a conventional general servo motor control device is shown in FIG. Figure 4 shows a device that controls a brushless servo motor (permanent magnet type synchronous motor), and is a method that is widely used as a shaft drive method for numerical control (hereinafter referred to as NC) machine tools. .

The operation will be explained below. The function generating section 1 calculates the position to which the tool, etc. should move based on external input data such as an NC program, that is, generates a function, and converts the generated position command value ps into the position. It is transferred to the error amount calculation section 2 and the speed feedforward control section 11. The speed feedforward control section 11 is intended to perform high-speed positioning by reducing the adverse effects of positioning dead time in the -order lag control system or the occurrence of a position error amount DIFF, which will be described later. Speed command data SD is generated based on the transferred position command value PS, and the speed command data SO is transferred to the speed error amount calculation section 5 without passing through the position control section 3. With such a speed feedforward control function, the position error ir++rF can be set to 7 in a steady state as if the servo motor 9 were moving at a constant velocity. Further, the position error amount calculation unit 2 calculates the deviation between the motor position detection value MS obtained from the position detector 10 coupled to the servo motor 9 and the position command value ps, that is, the position error amount DIFF, and calculates the position error amount DIFF. The error amount DIFF is transferred to the position control section 3. The position control unit 3 uses a position control loop cane (Kv) for the position error amount DIFF.
By multiplying the rotation speed command R of the servo motor 9
5 is calculated, and this rotation speed command R5 is transferred to the speed error amount calculation section 5.

On the other hand, the speed calculation section 4 uses a known technique to detect the position detector 1.
The actual speed (speed detection value RV) of the servo motor 9 is calculated based on the motor position detection value MS from 0. Then, the speed error amount calculation section 5 calculates the difference between the rotation speed command R5 from the position control section 3, the speed command data SD from the speed feedforward control section 11, and the speed detection value RV from the speed calculation section 4. , is transferred to the speed control unit 6 as the speed error amount SE. The speed control unit 6 controls the manually operated speed error amount S.
By amplifying E by PI (proportional and integral), a torque command value TQ to be output to the servo controller 9 is calculated and manually inputted to the current command calculation section 7. The current command calculation unit 7 makes the amplitude of the current proportional to the torque command value TQ, which is the output of the speed control unit 6, and multiplies it by a unit sine wave corresponding to the rotational position of the servo motor 9 to obtain an alternating current command. Here, since a relationship is established in which the sum of the three-phase currents is always zero, the current command calculation unit 7 processes only two of the three phases, for example, the U phase and the V phase, and calculates the respective phase current commands. The values are transferred to the current control unit 8 as IUm and Iv''.The current control unit 8 configures a current control loop using a known method, and outputs current command values for each phase winding U, V, and W of the servo motor 9. is generated, a current based on the current command value is passed through each phase winding of the servo motor 9 by power amplification, and the servo motor 9 is rapidly driven to one position in a predetermined direction.

(Problem to be solved by the invention) Position command value PS and motor position detection value MS as described above
In a control method in which the rotational speed command ns is generated by multiplying the position error amount DIFF by the position control loop gain Kv, the position error amount DIFF is determined by the reciprocal of the position control loop gain Kv. It converges to a drop exponentially with a time constant. Now, DIFF the position error amount [
mm], rotational speed command ns to v [mm/5ecl
, position loop gain KV [17sec], then DIFF/position command value ps - actual position detection value MSv
-DIFF x Kv--(1), and the above (
From equation 1), DIFF −v/kv++++ (2) is obtained. That is, the position error amount DIFF is the position control loop gain Kv
It can be seen that the larger the value, the smaller the value. Then, 9 in the position control loop gain is the follow-up side, that is, the servo motor 91
The better the responsiveness of mechanical loads, control circuits, etc., the better the position command value P.
Since it can closely follow S, it is a good idea to set a large value. Furthermore, since the positional error amount DIFF directly affects the cutting accuracy in machine tools that perform synchronous operation of two or more glazes, it is a constant requirement to keep it as small as possible within the practicable range.

However, as mentioned above, the servo motor, mechanical load,
There are problems with the responsiveness of the control circuit, etc., and if a large position control loop gain Kv is set without taking these into consideration, adverse effects such as mechanical vibration will occur, so even under the worst use conditions for servo control, there will be no inconvenience. The upper limit value within the range in which this phenomenon does not occur was adopted as 9 for the position control loop gain. This gain value Kv is operated as a constant value. The upper limit values of the gains such as the proportional operation gain P and the integral operation gain I in the speed control loop are determined based on the same concept as for the position control loop gain, and are adopted as constant values in the speed control loop.

In this way, the position control loop gain 9 and the speed control loop canes P, I, etc. are constants that can avoid mechanical resonance and vibration in the steady control state, but the position error amount DIF
F has a fairly large value transiently, and as a result, the deterioration in machining accuracy may be greater than the deterioration in machining accuracy due to mechanical vibration caused by increasing the position control loop gain Kv. Figure 5 shows the transient position error amount DIF
This is an example showing how F is generated and converged, and in this example, the position control loop gain is constant at −35 [17 sec]. Also, this Fig. 5 is an example of controlling a single motor to which no mechanical load is connected, and the speed is On + m/sec - + 6000 mm/sec at 1-1° in the figure.
Start of acceleration to c, time from t to t2 is speed 6000mm
/sec constant speed command, speed 6000a++ at 1-12
Start of deceleration from n/sec to 0+nI++/sec, t-
The rotational speed command R5 is generated so that the speed becomes Omm/sec at t3. As can be seen from FIG. 5, when the speed of the servo motor 9 changes, the position error amount DIFF transiently increases. For example, at time t. During acceleration starting from , the position error amount DIFF reaches 13 μI, which is 1/Kv・1/35 [se
It decays exponentially with a time constant of c ]. The case in Figure 5 is an example of single motor control, but if a machine tool is connected as the motor load and position detection is performed using a position detector (for example, inductosin) installed at the bottom of the table, the delay factor in the mechanical system is also added, so acceleration/deceleration is 11! The positional error amount DIFF occurring at f becomes even larger than in the case of FIG.

In this way, the position error ff1, which is the deviation from the true trajectory,
Even in a transient state where DIFF is large, the position error is 4ij DI
The convergence of F F is performed with a time constant determined by 9 for the position control loop gain determined in a steady state, and since there is no means to apply 9 to a value larger than the position control loop gain Kv, cutting with a large machining shape error is The drawback was that it lasted a relatively long time. This drawback has become a very serious disadvantage in the current situation where high-speed, high-precision machining demands are increasing.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to make each loop gain of position control and speed control variable in accordance with the magnitude of the position error amount DIFF, so that the position error amount DIFF is It is an object of the present invention to provide a motor control device that can set each gain to a larger value as the gain increases, and can ensure machining accuracy during high-speed machining, sudden acceleration, and sudden deceleration.

(Means for Solving the Problems) The present invention provides a motor, a position detecting means for detecting and feeding back the position of the motor, and a position detecting means for detecting a position error amount between a position command value and an actual detected position value. The present invention relates to a motor control device comprising an error amount detection means and controlling the motor in °C based on a predetermined position control loop gain and a speed control loop gain. Achieved by providing gain determining means for determining the position control loop gain and the speed control loop gain according to a preset function, and making the function have a characteristic of increasing each gain as the position error amount increases. be done.

(Function) In the present invention, the gain determining means determines the position control loop gain and the speed control loop gain according to a preset function according to the position error amount which is the deviation between the position command value and the actual position detection value. has been established. The gain determining means changes each gain according to the manually input position error amount, and when the error amount increases by 1+M, each loop gain is increased. As a result, even if an operation is performed in which the zero position error amount becomes excessively large, the position error amount can be quickly converged to zero, so that high machining accuracy can always be maintained.

(Embodiment) An embodiment of the wooden invention is shown in FIG. 1 in correspondence with the conventional example shown in FIG. In FIG. 1 illustrating the invention, the position error 1
The operation up to the calculation of DIFF is exactly the same as that of the conventional device explained in FIG.

In the wood invention, the positional error amount DIFF is transiently large (even if it occurs, the positional error amount DIFF quickly converges to zero, and the positional error amount D
As the IFF increases, the position control loop gain increases,
A gain determining unit 12 is provided to increase the speed control loop gains P and I. The gain determining unit 12 determines a position control loop gain KV according to a preset function corresponding to the calculated position error ff1DIFF, and transfers the determined position control loop gain KV to the position control unit 3 as the loop gain to be multiplied.

FIG. 2 shows an example of a function set in the gain determining section 12, and shows the absolute value l D of the position error amount DIFF.
By IFF l, IDIFFI≦d, Kv-α, (
The position control loop gain Kv is determined from the relationship: lower limit) l DTFF l≧d2 and 9·α2 (upper limit) dl < IDIFFI < d2. The position control unit 3 controls the position error amount DIFF and this position error f.
Depending on the magnitude of f1DIFF, a rotational speed command R5 is generated based on the position control loop gain Kv determined by the gain determining section 12 as described above.

Further, the gain determining unit 12 calculates the calculated positional error amount DIF.
Corresponding to F, the P gain (proportional) and (1) gain (integral) of the speed control loop are determined according to a preset function and transferred to the speed control section 6 for I'1 control. FIG. 3 shows that the speed control loop gain P,
This shows an example of a function that determines the positional error amount D.
Due to the absolute value of IFF I DIFF I, IDTFF1≦d! P−P,, l−11 (lower limit) l DIFF l≧d2, P=P2. hh
(Upper limit) dl < l DIFF l < P2.
The speed control loop gains P and I are determined from the relationship in 12.

Speed error ffi generated by the same process as the conventional device
Based on SE and the P gain and ① gain of the speed control loop determined by the gain determination section 12 as described above, the speed control section 6 generates a torque command value TQ and manually inputs it to the current command calculation section 7. After the operation of the current command calculation unit 7, the specified current flows to each phase of the servo motor 9, and the servo motor 9
The operation up to driving is exactly the same as that of the conventional device.

As described above, in the present invention, the position error io+F
Each time p is calculated, the gain determination unit 12 sets the position control loop gain to 9 and the speed control loop gains P and I to the position error ff1DIF according to the size of the position error amount o+FF.
Since it is determined to increase as F increases, even if the positional error amount DIFF increases transiently, it is possible to quickly converge the positional error amount DIFF to zero. Further, in a steady control state, the position control loop gain and the speed control loop gain can be set to stable control without causing mechanical resonance or the like in the control system.

(Effects of the Invention) According to the control device of the present invention, each control loop gain is increased as the position error amount DIFF increases, so that the position error amount DIFF transiently increases as during sudden acceleration or sudden deceleration. Even if becomes excessive, it can quickly converge to zero. Furthermore, each control loop gain in the steady control state can be set relatively smaller than the control loop gain in the transient state, depending on the size of the position error amount DIFF.
Stable control is possible without generating mechanical resonance or the like. As a result, machining trajectory errors can be kept small even when high-speed cutting is performed, and motors such as servo motors can be controlled at high speed and with high precision.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG.
Figure 3 is a diagram showing an example of a function of position control loop gain, Figure 3 is a diagram showing an example of a function of speed control loop gain, Figure 4 is a block diagram showing an example of a conventional motor control device, and Figure 5 is a diagram showing an example of a function of speed control loop gain. It is a figure which shows the characteristic example of a so-called position ship. l...function generation section, 3...ut control section, 4...
Speed calculation section, 6... Speed control section, 7... Current command calculation section, 9... Servo motor, 10... Position detector,
12...Kane decision section. Applicant's agent Yu Yasugata Sancha 2 Figure

Claims (1)

[Claims] 1. Equipped with a motor, a position detection means for detecting and feeding back the position of the motor, and a position error amount detection means for detecting a position error amount between a position command value and an actual position detection value, and performing predetermined position control. In a motor control device that controls the motor based on a loop gain and a speed control loop gain, gain determination determines the position control loop gain and speed control loop gain according to a preset function corresponding to the position error amount. A motor control device characterized in that the function is characterized in that each gain increases as the positional error amount increases.