KR100584620B1 - Method and apparatus for auto-tuning a controller of paper feeding system in a printer - Google Patents

Abstract

The present invention provides a method and apparatus for automatic controller tuning of a printer paper feed system. A controller automatic tuning method of a printer paper feed system according to the present invention includes: a data acquisition step of performing an open loop test to obtain input / output data for the paper feed system; A system model derivation step of deriving a system model by identifying a system using the input / output data; A speed control step of controlling the speed of the paper feed system by calculating gain of the controller using the derived system model; And an observer model forming step of forming a disturbance observer model by using the system model parameter estimated in the system model derivation step. According to the present invention, by forming a disturbance observer model for observing and compensating for the disturbance during low speed driving of the printer paper feed system, the low frequency disturbance component can be removed using the disturbance observer to improve the low speed control performance.

Description

Method and apparatus for auto-tuning a controller of a printer feeding system {method and apparatus for auto-tuning a controller of paper feeding system in a printer}

1 is a block diagram showing the configuration of a printer servo system using a PID controller to which the present invention is applied.

Figure 2 is a block diagram showing in detail the configuration of the controller automatic tuning unit of the printer paper feed system according to the present invention.

3 is a flowchart showing in detail a controller automatic tuning method of a printer paper feed system according to the present invention.

The present invention relates to a printer paper feed system, and more particularly, to a method and apparatus for automatic controller tuning of a printer paper feed system for forming a disturbance observer model for observing and correcting a disturbance during low speed driving of a printer paper feed system.

PID controllers are widely used in paper feeding systems using a DC motor as a power source. The PID controller includes a proportional controller, an integral controller, and a derivative controller. In addition, a PI controller including a proportional controller and an integral controller is also widely used.

Printer servo systems have various kinds of disturbances such as load friction, torque ripple, ripple due to mechanical vibration, drift offset, and the like. This disturbance is a major cause of deterioration of control performance in systems requiring low speed precision driving. However, it is difficult to compensate for low frequency disturbance with the conventional PID controller alone.

An object of the present invention is to provide a method and apparatus for automatic controller tuning of a printer feeding system that forms a disturbance observer model for observing and compensating for disturbance during low speed driving of a printer feeding system.

In order to accomplish the above technical problem, a controller automatic tuning method of a printer paper feed system includes: a data obtaining step of performing open-loop test to obtain input / output data for the paper feed system; A system model derivation step of deriving a system model by identifying a system using the input / output data; A speed control step of controlling the speed of the paper feed system by calculating gain of the controller using the derived system model; And an observer model forming step of forming a disturbance observer model by using the system model parameter estimated in the system model derivation step. The data acquiring step may include inputting a test signal to maintain a constant sign of the output speed to remove the influence of load friction. The deriving a system model may include deriving a system model using a least square method. The speed control step may include calculating a gain of the controller by a pole placement method using the derived system model.

In order to accomplish the above technical problem, a controller automatic tuning device for a printer paper feed system includes: a data acquisition unit configured to obtain an input / output data for the paper feed system by performing an open loop test; A system model derivation unit for deriving a system model by identifying a system using the obtained data; A gain calculator configured to control the speed of the paper feed system by calculating a gain of the controller using a system model derived by the system model guider; And an observer model forming unit forming a disturbance observer model by using the system model parameter estimated by the system model deriving unit.

Hereinafter, with reference to the accompanying drawings will be described a preferred embodiment of the automatic tuning method and apparatus of the paper feeding system according to the present invention.

1 is a block diagram illustrating a configuration of a printer servo system using a PID controller to which the present invention is applied. The printer servo system 100 includes a control signal generator 110, a PID controller 120, and a servo system 130. , Sensor 140, automatic tuning unit 150, and disturbance observation unit 160.

The control signal generator 110 generates a control signal for a motion plan of the servo system 130 to be controlled.

The PID controller 120 calculates a control input of the servo system 130 from the difference between the control signal and the output signal.

The automatic tuning unit 150 compares the control signal with the output signal sensed by the sensor 160 to adjust the gain of the PID control unit 120 and form an observer model.

The disturbance observing unit 160 serves to observe the disturbance existing in the servo system 130. The estimated disturbance is compensated through the input.

2 is a block diagram showing in detail the configuration of the automatic controller controller of the printer paper feeding system according to the present invention.

As shown in FIG. 2, the feed controller automatic tuning unit 150 that automatically tunes the controller in the printer feed system using the DC motor includes a data acquisition unit 210, a preprocessing filter 220, and a system model induction unit 230. , A gain calculator 240, and an observer model forming unit 250.

The data acquisition unit 210 performs an open loop test to obtain input / output data for the paper feeding system. In addition, the data acquirer 210 may acquire input / output data by designing a test signal that maintains a constant sign of the output speed in order to remove the influence of load friction.

The preprocessing filter 220 may remove the drift offset from the input / output data obtained from the data acquisition unit 210. In particular, the pretreatment filter 220 removes the drift offset using a curve fitting method. The pretreatment filter 220 also includes a low pass filter for removing ripple due to torque ripple and instrument vibration.

The system model derivation unit 230 may identify a system using the data filtered by the preprocessing filter 220 to derive a system model. In particular, the system model derivation unit 230 derives a system model using a least square method.

The gain calculator 240 may control the speed of the paper feeding system by calculating the gain of the controller using the system model derived by the system model deriving unit 230. In particular, the gain calculator 240 calculates a gain of the controller by a pole placement method using the derived system model.

The observer model forming unit 250 forms a disturbance observer model using the system model parameters K and T estimated by the system model deriving unit 230.

In general, the speed output of a paper feeding servo system of a printer employing a DC motor can be approximated to a primary system as follows.

Where Y (s) is velocity, U (s) is system input, d (s) is disturbance, K is system DC gain, and T is Is a time constant.

Disturbance of the printer servo system can be modeled by experimental observations such as load friction, torque ripple, mechanical vibration, and drift offset. Such disturbance is difficult to express with the disturbance model assumed in the conventional least square method. In the present invention, after estimating the low frequency disturbance existing in the system using the disturbance observer, it is intended to compensate for this through the controller.

To design the disturbance observer, system model parameters must be known. After the preprocessing, the system model parameters are obtained using the least square method.

The present invention can accurately estimate the parameters (K, T) in spite of the disturbance existing in the actual system as in Equation (1). In other words, in order to estimate the parameters K and T, it is necessary to design a preprocessing filter for removing disturbance.

First, the effects of load friction can be eliminated by designing the test signal to keep the sign of the output speed constant.

In addition, ripple due to torque and instrument vibration can be eliminated by using a low pass filter. The low pass filter can be implemented as a general finite impulse response (FIR) digital filter. The cutoff frequency is designed to be greater than the frequency of the test signal and less than the frequency of the output ripple and noise.

On the other hand, in order to design a filter for removing a drift offset, when curve fitting is performed on a signal as a linear function, the linear function immediately represents the drift offset. Therefore, the drift offset can be eliminated by canceling the first order function value in the original signal. The detailed algorithm for obtaining the drift offset is as follows.

Where x represents time and y represents velocity output. N represents the number of measured data, and Ts represents the sampling interval. First, find the average of x and y as follows.

If the slope of the linear function is A and the y-intercept is B, A and B can be calculated by Equation 4.

Where T represents the transformation of the matrix.

The final filter output of the drift filter is expressed by Equation 5.

Now, a least square method is applied to the filtered signal to estimate the system model parameters (K, T).

Least squares method is based on a discrete time model. Therefore, when Equation 1 is converted into a discrete time model, Equation 6 is obtained.

If Equation 6 is transformed into a vector form, it can be expressed as Equation 7.

Here, φ (k-1) and θ are as follows.

In Equation 6, the disturbance d (k-1) is eliminated through the preprocessing filter according to the present invention, and thus it is not considered here. When the number of data is N, equation (9) can be obtained from equation (7).

Here, Y and Φ are measurable variables, and θ is a parameter to be estimated, so θ is calculated by Equation 10 by the least square method.

Where Φ and Y are as shown in Equation (11).

As described above, the least squares method can be used to estimate the system model parameters (K, T).

3 is a flowchart showing in detail a controller automatic tuning method of a printer paper feed system according to the present invention.

First, the sampling period Ts and the frequency? Of the test signal are initialized (step S300).

Next, the parameters A and Aoffset of the test input signal Vin are designed such that the output speed is always greater than zero (step S310). At this time, the test input signal Vin is expressed by Equation 12.

The test input signal Vin is applied to the system (step S320), and an open loop test is performed to measure and store input / output data for each sampling period Ts (step S330). The high frequency noise is removed from the measured input / output signal using a low pass filter (step S340), and the drift offset is removed from the input / output signal using a drift filter (step S350).

The system model parameters (K, T) are estimated by applying the least square method as described above to the filtered signal (step S360).

The gain (Kp, Ki) of the PI controller is calculated by using a pole placement method using the derived system model (step S370). Since the pole arrangement method for calculating the gain of the PI controller is known, a detailed description thereof will be omitted.

Equation 13 may be used to calculate the gain of the PI controller in the pole arrangement method.

Equation 13 may be used to calculate gains Kp and Ki of the controller from Equation 14.

In the manner as described above, the system can be identified and the gain of the PID controller can be calculated and applied to the paper feeding system to perform speed control.

Next, the disturbance observer is designed using the system model parameters K and T (step S370).

The shape of the disturbance observer is shown in Equation 15 below.

Is the time constant of the low pass filter. Designed to have a cutoff frequency greater than the bandwidth of the control system. Therefore, it can be easily proved that Equation 16 holds.

Therefore, Equation 15 serves to observe the disturbance existing in the servo system. The estimated disturbance is compensated through the input. Therefore, it is possible to eliminate the low frequency speed ripple existing in the low speed driving.

According to the present invention, by forming a disturbance observer model for observing and compensating for the disturbance during low speed driving of the printer paper feed system, the low frequency disturbance component can be removed using the disturbance observer to improve the low speed control performance.

Claims (5)

A data acquisition step of performing input and loop test to obtain input and output data for the paper feeding system; A system model derivation step of deriving a system model by identifying a system using the input / output data; A speed control step of controlling the speed of the paper feed system by calculating gain of the controller using the derived system model; And And an observer model forming step of forming a disturbance observer model using the system model parameter estimated in the system model derivation step. The method of claim 1, wherein the data acquisition step And a step of eliminating the influence of load friction by inputting a test signal to maintain a constant sign of the output speed. The method of claim 1, wherein deriving the system model A method for automatically tuning a controller of a printer paper feed system comprising the step of deriving a system model using a Least Square Method. The method of claim 1, wherein the speed control step Calculating the gain of the controller by a pole placement method using the derived system model. A data obtaining unit which performs an open loop test to obtain input / output data for the paper feeding system; A system model derivation unit for deriving a system model by identifying a system using the obtained data;  A gain calculator configured to control the speed of the paper feed system by calculating a gain of the controller using a system model derived by the system model guider; And And an observer model forming unit for forming a disturbance observer model using the system model parameters estimated by the system model deriving unit.

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