KR100218930B1 - Velocity control method and velocity control apparatus of servo motor - Google Patents

Abstract

The present invention relates to a control method and a control device for a servo motor, and the control device includes a forward control unit for calculating a control torque by differentiating a target speed and multiplying the nominal inertia efficiency of the servo motor, and an output speed and a negative feedback speed of the servo motor. And a feedback controller for inputting the target speed to calculate the correction torque, and an adder for calculating the torque command by adding the correction torque to the control torque. With such a configuration, it is possible to obtain a control apparatus and a control method of the servomotor having a simple configuration of the control system and excellent control response performance.

Description

Servo motor speed control method and speed control device.

The present invention relates to a speed control method and a speed control apparatus for a servomotor.

In order to obtain a desired speed from the servo motor to be controlled, the control device of the servo motor should have a control unit that calculates a control torque input from the speed of the set servo motor, and a feedback unit which feeds back the output of the control object and compares it with the input value. Should be,

However, in servomotors, mechanical disturbances caused by vibration, load torque fluctuations, or dynamic characteristics act on the overall control system. These disturbances are added to or subtracted from the control torque input or added to the feedback signal, resulting in poor system response and unstable system. Therefore, in order to minimize the effects of disturbance, a method of adding a load torque observer to the PI controller is used.

3 shows a block diagram of a control system of the servomotor which imposes the load torque observer 12 on the PI controller 11 as described above. As can be seen in FIG. 3, the actual motor speed ω is subtracted from the target speed ω ^* to calculate the speed difference, which is input to the PI controller 11 to generate a torque command ω ^* and to generate a torque command. (ω ^* ) is a control loop inputted to the servo motor 2 by subtracting the load torque ω _d , and the output speed ω of the servo motor 2 is differentiated and the inertia efficiency of the servo motor 2 is reduced. (J _n ) is multiplied by the control torque command (ω ^* ) and multiplied by (J _n ) to the observer filter 14, and the output torque signal ω _d of the observer filter 14 is returned to the control torque command. The addition consists of the other control loop.

In this conventional servo motor control system, the load torque observer adds the actual load to the LPF (low pass filter), so it is difficult to remove the disturbance of relatively high frequency, and to increase the frequency band of the observer to increase the disturbance removal performance, Noise makes the control system unstable. In addition, since the conventional servomotor control system is a type of load torque observer imposed, it is difficult to design and analyze the entire control system, thereby causing an inefficient problem.

Therefore, an object of the present invention is to configure the control device of the servo motor that traps only one feedback control unit together with the forward control unit, which is easy to design and analyze, and has superior tracking performance compared to the conventional control system of the servo motor having a load torque observer. It is to provide a control system of a servo motor with robust characteristics against disturbances.

1 is a block diagram of a servo motor control system according to the present invention;

2 is a block diagram of a servo motor control system according to the prior art;

3 is a response line diagram of speed tracking performance of a servo motor control system in the absence of disturbance;

4 is a response line diagram of the speed maintenance performance against the disturbance of the servomotor control system according to the present invention;

5 is a response line diagram of speed maintenance performance against disturbance of a servo motor control system according to the related art.

* Explanation of symbols for main parts of the drawings

1: Forward control unit 2: Servo motor

3: feedback control unit 4: subtraction unit

5: adder

The object of the present invention is to calculate the control torque by differentiating the target speed and multiplying the nominal inertia efficiency of the servomotor in the speed control method of the servomotor, and outputting the output speed and the target speed fed back from the servomotor. Calculating a speed difference between a target speed and an output speed by inputting; calculating a corrected torque by removing and suppressing disturbance by inputting the speed difference; and adding the corrected torque to the control torque to add to the servo motor. Loss is achieved by a speed control method of a servomotor, comprising calculating a torque command.

In addition, the transfer function of calculating the corrected torque may be represented by Equation 1 to include the PI control of the servomotor and the load torque observation.

[Equation 1]

C (s) = J _n (ωs ³ + ωs ² + ωs + ω) / (s ³ + ω _o ² s)

Where C (s) is the transfer function, α = 2ω _c + ω _b, β = ω _c ² + 2ω _c ω _b, γ = 2ω _c ω _o ² + ω _c ² ω _b, δ = ω _c ² ω _b ² Where J _n is the nominal inertia efficiency of the servomotor, s is the Laplace derivative, ω _c is the frequency band of the feedback control section, ω _o is the reference frequency of disturbance, and ω _b is the frequency variation of the disturbance.

In addition, the object of the present invention, in the speed control apparatus of the servo motor, a forward control unit for differentiating the target speed and multiplying the nominal inertia efficiency of the servo motor to calculate the control torque, the output speed and the target output speed returned from the servo motor A subtraction unit for calculating a speed difference between a target speed and an output speed by inputting a speed; It is achieved by a speed control apparatus for a servomotor, comprising an adder for calculating a torque command.

In addition, the transfer function of the feedback control unit for calculating the corrected torque may be represented by Equation 1 below to serve as a PI controller and a load torque observer.

[Equation 1]

C (s) = J _n (ωs ³ + ωs ² + ωs + ω) / (s ³ + ω _o ² s)

Where C (s) is the transfer function, α = 2ω _c + ω _b, β = ω _c ² + 2ω _c ω _b, γ = 2ω _c ω _o ² + ω _c ² ω _b, δ = ω _c ² ω _b ² Where J _n is the nominal inertia efficiency of the servomotor, s is the Laplace derivative, ω _c is the frequency band of the feedback control section, ω _o is the reference frequency of disturbance, and ω _b is the frequency variation of the disturbance.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention;

1 shows a block diagram of a control system of a servomotor according to the present invention. As can be seen in FIG. 1, the control system includes a forward control unit 1, a feedback control unit 3, and a subtraction unit 4. It consists of the adder 5. The forward control unit 1 is configured to calculate the control torque ω _u by multiplying the nominal inertia efficiency J _n by making the angular acceleration by differentiating the target speed ω ^* . Since the forward control unit 1 includes the differentiator s, the target speed ω ^* is constant. The value of the control torque (ω _u ) is 0, which is equivalent to not operating. On the other hand, when the target speed (ω ^* ) is time-varying tracking control, the control torque ω _u is additionally calculated to follow the time-varying target speed (ω ^* ).

The subtraction unit 4 calculates the speed difference between the target speed ω ^* and the output speed ω by subtracting the output speed ω returned from the servomotor 2 to the target speed ω ^* . The calculated speed difference is input to the feedback controller 3.

The feedback controller 3 inputs the speed difference and calculates a corrected torque ω _o according to the transfer function shown in Equations 2 and 3 below.

[Equation 2]

C (s) = J _n s (1-F (s)) / F (s)

Where C (s) is the transfer function, Jn is the nominal inertia efficiency, F (s) is the disturbance suppression filter function, and s is the Laplace fine molecule.

[Equation 3]

F (S) = ∏ _{K = 1, N} (1-Q _K (s)

Where s is the Laplace micromolecule, F (s) is the disturbance suppression filter function, and Q _K (s) is the disturbance selection function.

In addition, the feedback controller has the performance of the PI controller and the disturbance elimination filter by setting the value of Q _k in Equation 3 as shown in Equations 4 and 5 below.

[Equation 4]

Q ₁ = Q ₂ = ω _c / (s + ω _c )

Where s is the Laplace derivative and ω _c is the frequency band of the feedback controller.

[Equation 5]

Q ₃ = ω _b s / (s ² + ω _b s + ω _o ² )

Where s is the Laplace derivative, ω _o is the reference frequency of the disturbance, and ω _b is the frequency variation of the disturbance.

Therefore, the transfer function of the feedback controller 3 is expressed as Equation 1, and serves as a PI controller and a load torque observer.

[Equation 1]

C (s) = J _n (ωs ³ + ωs ² + ωs + ω) / (s ³ + ω _o ² s)

Where C (s) is the transfer function, α = 2ω _c + ω _b, β = ω _c ² + 2ω _c ω _b, γ = 2ω _c ω _o ² + ω _c ² ω _b, δ = ω _c ² ω _b ² Where J _n is the nominal inertia efficiency of the servomotor, s is the Laplace derivative, ω _c is the frequency band of the feedback control section, ω _o is the reference frequency of disturbance, and ω _b is the frequency variation of the disturbance.

In addition, the adder 5 adds the corrected torque ω _o calculated by the feedback control unit 3 to the control torque ω _u calculated by the forward control unit 1 and inputs the torque to the servomotor 2. Compute the command (ω ^* ).

Referring to the operation of the present invention according to the configuration of the speed control method and the speed control apparatus of the servo motor according to the embodiment of the present invention as described above are as follows.

First, when the target speed ω ^* to rotate the servomotor 2 is input to the forward control unit 1, the target speed ω ^* is differentiated in the forward control unit 1 and the nominal inertia efficiency J _It is amplified by _n ) to calculate the control torque (ω _u ). The control torque ω _u is added to the corrected torque ω _o calculated by the feedback controller 3 and the adder 5 so that the torque command ω ^* is calculated and the torque command ω ^* is the servomotor 2. ) To drive the servomotor (2). The servomotor 2 may be disturbed by disturbances such as the load torque ω _d and rotate at the actual speed ω different from the target speed ω ^* . The output speed ω and the target speed ω ^* of the servomotor 2 are input to the subtraction unit 4, and a difference between the target speed ω ^* and the output speed ω is calculated to calculate the feedback control unit 3. Is entered. The feedback controller 3 has a transfer function as shown in Equation 1, and removes the disturbance such as the load torque ω _d applied to the servo motor 2 so that the servo motor 2 can rotate at the target speed ω ^* . The corrected torque (ω _o ) is calculated.

According to Equation 2 and Equation 3, the relationship between the target speed ω ^* and the output speed ω may be expressed as shown in Equation 6.

[Equation 6]

ω (s) = ω ^* (s) -F (s) ω _d (s) / J _n s

Where J _n is the nominal inertia efficiency of the servomotor, s is the Laplace fine molecule, and F (s) is the disturbance suppression function.

As shown in Equation 6, when no disturbance is applied to the servomotor 2 and the control system, the output speed ω is exactly the same as the target speed ω ^* , so that the control system of the present invention has perfect speed tracking performance. Will have In addition, when disturbance is applied, the disturbance suppression filter function F (s) serves as a disturbance suppression function to remove the effects of the disturbance. At this time, the specific function value of the disturbance suppression filter function is set by the equation (3).

Controlling the speed of the servomotor by the control method and control apparatus of the servomotor according to the present invention as described above has the following effects.

First, when disturbance such as load torque is not applied to the servomotor, the target speed ω ^* and output speed ω are completely the same by applying ω ^* = ω in Equation 6 above, so that the load torque is applied to the PI controller. It can be seen that the speed tracking performance is superior to the speed tracking performance of the control system according to the related art in which an observer is imposed. Figure 3 shows the response diagram of the speed following performance as described above, the speed tracking diagram 22 by the PI controller with a load torque observer is delayed with respect to the target speed (ω ^* ), but the control according to the present invention. It can be seen that the speed tracking diagram of the device is completely consistent with the target speed.

4 is a response diagram of the speed maintenance performance against the disturbance of the servo motor control system according to an embodiment of the present invention, and FIG. 5 is a response diagram of the speed maintenance performance against the disturbance of the servomotor control system according to the prior art. As can be seen in Figure 4, the control system according to the present invention eliminates the speed change of the servomotor due to disturbance, but as shown in Figure 5, the control system having the load torque observer and the PI controller exceeds the frequency band of the load torque observer. Can not eliminate disturbance. However, the control system according to the present invention has an advantage that the disturbance of the high frequency band can be eliminated by selecting the function Q _K of Equation 3 above.

In addition, the control apparatus according to the prior art separately installs the PI controller and the load torque observation, the control apparatus according to the present invention, because it performs the control of the servo motor with one feedback controller, there is an advantage that the design and analysis is easy.

Claims (4)

A method for controlling the speed of a servomotor, the method comprising: calculating a control torque by differentiating a target speed and multiplying the nominal inertia efficiency of the servomotor, and inputting the output speed and the target speed returned from the servomotor to determine the target speed and the output speed. Calculating a speed difference, calculating a corrected torque by removing and suppressing disturbance by inputting the speed difference, and calculating a torque command applied to the servo motor by adding the corrected torque to the control torque. Speed control method of the servo motor comprising a. The method of claim 1, wherein the transfer function of calculating the corrected torque is expressed by Equation (1). [Equation 1] C (s) = J _n (ωs ³ + ωs ² + ωs + ω) / (s ³ + ω _o ² s) Where C (s) is the transfer function, α = 2ω _c + ω _b, β = ω _c ² + 2ω _c ω _b, γ = 2ω _c ω _o ² + ω _c ² ω _b, δ = ω _c ² ω _b ² Where J _n is the nominal inertia efficiency of the servomotor, s is the Laplace derivative, ω _c is the frequency band of the feedback control section, ω _o is the reference frequency of disturbance, and ω _b is the frequency variation of the disturbance. A speed control apparatus for a servomotor, comprising: a forwarding control unit for calculating a control torque by differentiating a target speed and multiplying the nominal inertia efficiency of the servomotor, and inputting the output speed and the target speed returned from the servomotor to the target speed and the output speed. A subtractor for calculating a speed difference, a feedback controller for inputting the speed difference to remove and suppress disturbance to calculate a corrected torque, and an adder for calculating a torque command by adding the corrected torque to the control torque. Speed control device of the servo motor, characterized in that The speed control apparatus of claim 3, wherein the feedback control unit that calculates the corrected torque has a transfer function represented by Equation 1. 4. [Equation 1] C (s) = J _n (ωs ³ + ωs ² + ωs + ω) / (s ³ + ω _o ² s) Where C (s) is the transfer function, α = 2ω _c + ω _b, β = ω _c ² + 2ω _c ω _b, γ = 2ω _c ω _o ² + ω _c ² ω _b, δ = ω _c ² ω _b ² Where J _n is the nominal inertia efficiency of the servomotor, s is the Laplace derivative, ω _c is the frequency band of the feedback control section, ω _o is the reference frequency of disturbance, and ω _b is the frequency variation of the disturbance.