SYSTEM COMPRISING ROBUST OPTIMAL DISTURBANCE OBSERVER FOR HIGH-PRECISION POSITION CONTROL PERFORMED BY ELECTRONIC DEVICE, AND CONTROL METHOD THEREFOR

BACKGROUND
Technical Field

The present disclosure relates to a system including a robust optimal disturbance observer for high-precision position control performed by an electronic device, and a control method therefor.

Background Art

Designing a controller that can be stably driven all the time with desired performance is one of the goals to be considered in designing a control system. Furthermore, when designing a control system, compensating for variations and uncertainty of a plant caused by errors in the manufacturing process also need to be considered.

Such a control system can be applied to various driving devices, and, specifically, can be applied to inspection equipment used in the manufacture of semiconductors and displays and to unmanned aerial vehicles such as drones, medical devices such as genetic testing machines, etc.

However, in the case of conventional control systems, a controller is designed by a trial-and-error method for the high-precision position/velocity control, and the designed controller is frequently driven unstably because the stability thereof is not guaranteed.

In addition, in the case of the existing design method, tolerances in the manufacturing process are not taken into account. Therefore, driving devices need to be precisely manufactured, and there is a problem that performance of a control system is greatly influenced by errors of the driving devices.

SUMMARY

The purpose of the present disclosure is to provide a system including a robust optimal disturbance observer for high-precision position control performed by an electronic device, and a control method therefor.

The purposes of the present disclosure are not limited to the above-mentioned purpose, and, by the following description, other purposes that have not been mentioned will be clearly understood by a person having ordinary skills in the art.

There may be provided the system including the robust optimal disturbance observer for high-precision position control performed by the electronic device according to an aspect of the present disclosure for achieving the above-mentioned purpose, including: a plant P to be controlled; a controller C; a first weight function W1; a second weight function W2; and a disturbance observer, wherein the first weight function W1 may receive a difference value between a disturbance w and an output u_DOof the disturbance observer as an input value, the second weight function W2 may receive a difference value between an output value of the controller C and the output u_DOof the disturbance observer as an input value, the plant P to be controlled may receive, as an input value, a sum value of the disturbance w and the difference value between the output value of the controller C and the output u_DOof the disturbance observer, and the controller C may receive an output value of the plant P to be controlled as an input value.

Other specific details of the present disclosure are included in the detailed description and drawings.

It may be possible that the control system designed according to the various embodiments of the present disclosure described above minimizes disturbances, stabilizes the system, and has robustness.

The effects of the present disclosure are not limited to the above-mentioned effect, and, by the following description, other effects that have not been mentioned will be clearly understood by a person having ordinary skills in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a system including a robust optimal disturbance observer for high-precision position control according to an embodiment of the present disclosure.

FIG. 2 is an exemplary view showing an example of frequency characteristics of a plant to be controlled according to an embodiment of the present disclosure.

FIG. 3 is an exemplary view for explaining frequency characteristics of a first weight function and a second weight function according to an embodiment of the present disclosure.

FIG. 4 is an exemplary view illustrating an open-loop transfer function of the system to which the first weight function and the second weight function according to an embodiment of the present disclosure have been applied.

FIG. 5 is an exemplary view showing a sensitivity function according to an embodiment of the present disclosure.

FIG. 6 is an exemplary view illustrating a torque transfer function according to an embodiment of the present disclosure.

FIG. 7 is an exemplary view illustrating an output of the plant in response to a disturbance input according to an embodiment of the present disclosure.

FIG. 8 is an exemplary view for comparing power spectrums and accumulated position error signals according to an embodiment of the present disclosure.

FIG. 9 is an exemplary view for explaining a region of uncertainty of a controlled model according to an embodiment of the present disclosure.

FIG. 10 is an exemplary view for explaining robustness of a controlled model according to an embodiment of the present disclosure.

FIG. 11 is a block diagram showing a device according to an embodiment of the present disclosure.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Advantages and characteristics of the present disclosure and methods for achieving them will become clear with reference to the embodiments described below in detail with the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed below and may be implemented in a variety of different forms, the embodiments are provided only to make the present disclosure complete and to make a person having ordinary skills in the technical field to which the present disclosure belongs fully understand the scope of the present disclosure, and the present disclosure is only defined by the scope of the claims.

Terms used in this specification are for the purpose of describing the embodiments and are not intended to limit the present disclosure. In this specification, expressions in the singular form include the meaning of the plural form unless otherwise specified. The expression “comprises” and/or “comprising” as used herein does not exclude the presence or addition of one or more components other than the mentioned components. Throughout the specification, one particular reference number consistently refers to one particular component, and, by the expression “and/or,” each of the mentioned components and all possible combinations thereof are included. Although expressions such as “first” and “second” are used to describe various components, it is needless to say that these components are not limited by these expressions. The expressions are only used to distinguish one component from another. Accordingly, it goes without saying that a first component mentioned below may also be a second component within the technology of the present disclosure.

Unless otherwise defined, all terms (including technical and scientific terms) used in this specification may have a meaning commonly understood by a person having ordinary skills in the technical field to which the present disclosure pertains. In addition, terms defined in commonly used dictionaries should not be interpreted ideally or excessively unless explicitly specifically defined.

The term “unit” or “module” used in this specification refers to software components and hardware components such as FPGA and ASIC, and the “units” or “modules” perform certain roles. However, the “units” or “modules” are not limited to software or hardware. The “units” or “modules” may be designed to be present in an addressable storage medium and may be designed to reproduce one or more processors. Therefore, for example, the “units” or “modules” include components such as software components, object-oriented software components, class components, task components and processes, functions, properties, procedures, subroutines, segments of a program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. Functions provided by the components and the “units” or “modules” may be combined into a smaller number of components and “units” or “modules,” or may be further separated into additional components and “units” or “modules.”

Expressions such as “below,” “beneath,” “lower,” “above,” and “upper,” which have spatially relative meanings, may be used to easily describe the relationship between one component and other components as shown in the drawings. It should be understood that the expressions having spatially relative meanings also refer to different directions of components that the components have when being used or operated in directions other than those shown in the drawings. For example, when a component shown in the drawings is flipped, that component that has been described as being “below” or “beneath” another component may be “above” the other component. Accordingly, the exemplary expression “below” may refer to both the directions below and above. The components can be oriented in other directions as well, so the expressions with spatially relative meanings can be interpreted according to the orientation.

In this specification, a computer refers to any type of hardware devices including at least one processor, and can be understood to also refer to software components operating in a corresponding hardware device according to an embodiment. For example, the computer can be understood to refer to all of a smartphone, a tablet PC, a desktop computer, a laptop computer, and user clients and applications running on each of these devices, and is not limited thereto.

Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

Each step described in this specification is described as being performed by a computer, but the subject of each step is not limited thereto. That is, according to the embodiments, at least a part of each step may be performed by a different device as well.

FIG. 1 is a block diagram illustrating a system including a robust optimal disturbance observer for high-precision position control according to an embodiment of the present disclosure.

In order to solve the existing problems, according to the present disclosure, a controller may be designed by designing a weight function for desired performance, a function in which errors due to uncertainty of a device to be driven are considered, and a nominal model as one model. Furthermore, the controller according to the present disclosure may be designed with an optimization method of a linear matrix inequality (LMI) so that the stability of the entire system is always guaranteed.

That is, in relation to a driving system, there are a problem that performance degradation occurs due to external disturbances and a problem that performance degradation is caused by uncertainty due to errors in the manufacturing process of a controlled object. Therefore, it may be possible to design a stabilized closed-loop system by designing the controller shown in FIG. 1.

Specifically, as shown in FIG. 1, the system according to an embodiment of the present disclosure may include a plant P to be controlled, a controller C, a first weight function W1, a second weight function W2, and a disturbance observer.

The first weight function W1 may receive a difference value between a disturbance w and an output u_DOof the disturbance observer as an input value, the second weight function W2 may receive a difference value between an output value of the controller C and the output u_DOof the disturbance observer as an input value, the plant P to be controlled may receive, as an input value, a sum value of the disturbance w and the difference value between the output value of the controller C and the output u_DOof the disturbance observer, and the controller C may receive an output value of the plant P to be controlled as an input value.

When the controller is designed by the above-mentioned method, it may be possible that the disturbance observer always stabilizes the closed-loop system, (2) effectively removes disturbances, and (3) effectively works even when there is uncertainty due to errors in the manufacturing process of a model to be controlled.

In other words, as shown in FIG. 1, when the controller is designed based on the linear matrix inequality, it may be possible to match the output of the controller with the disturbance and to solve the problem caused by uncertainty.

Specifically, the first weight function W1 may be a weight function for minimizing the difference between the applied disturbance w and the output u_DOof the disturbance observer based on the frequency characteristics of the plant P to be controlled, and the stability of the system may be improved by the first weight function.

Furthermore, the second weight function W2 may be a weight function for controlling the uncertainty of the plant P to be controlled, and, thanks to the second weight function, effective operation may be possible even in the presence of uncertainty due to errors in the manufacturing process of a model to be controlled.

That is, the disturbance observer according to an embodiment of the present disclosure may be formed based on the first weight function W1 and the second weight function W2, and, as described above, may improve the stability of the system by removing the disturbances and design a robust control model at the same time.

Meanwhile, according to an embodiment of the present disclosure, the plant P to be controlled, the controller C, the first weight function W1, and the second weight function W2 may be expressed by a state space expression as shown in Equation 1 below.

[Equation 1]

$\begin{matrix} P : \begin{matrix} \dot{x_{P}} (t) = A_{P} x_{P} (t) + B_{P} u_{P} (t) \\ y_{P} (t) = C_{P} x_{P} (t) \end{matrix} C : \begin{matrix} \dot{x_{C}} (t) = A_{C} x_{C} (t) + B_{C} u_{C} (t) \\ y_{C} (t) = C_{C} x_{C} (t) + D_{C} u_{C} (t) \end{matrix} W_{1} : \begin{matrix} \dot{x_{W_{1}}} (t) = A_{W_{1}} x_{W_{1}} (t) + B_{W_{1}} u_{W_{1}} (t) \\ y_{W_{1}} (t) = C_{W_{1}} x_{W_{1}} (t) + D_{W_{1}} u_{W_{1}} (t) \end{matrix} W_{2} : \begin{matrix} \dot{x_{W_{2}}} (t) = A_{W_{2}} x_{W_{2}} (t) + B_{W_{2}} u_{W_{2}} (t) \\ y_{W_{2}} (t) = C_{W_{2}} x_{W_{2}} (t) + D_{W_{2}} u_{W_{2}} (t) \end{matrix} & [Equation 1] \end{matrix}$

Here, as shown below, from the controller designed according to FIG. 1 and Equation 1, a state equation of the plant P to be controlled (Equation 2), a state equation of the controller C (Equation 3), and state equations of the first weight function W1 and the second weight function W2 (Equation 4) may be derived.

$\begin{matrix} \begin{matrix} {\dot{x}}_{P} (t) = A_{P} x_{P} (t) + B_{P} u_{P} (t) \\ = A_{P} x_{P} (t) + B_{P} u_{P} (t) + C_{C} x_{C} (t) + \\ D_{C} C_{P} x_{P} (t) - u_{DO} (t)) \\ = (A_{P} + B_{P} D_{C} C_{P}) x_{P} (t) + B_{P} C_{C} x_{C} (t) + \\ B_{P} w (t) - B_{P} u_{DO} (t) . \end{matrix} & [Equation 2] \end{matrix}$

$\begin{matrix} \begin{matrix} {\dot{x}}_{C} (t) = A_{C} x_{C} (t) + B_{C} u_{C} (t) \\ = A_{C} x_{C} (t) + B_{C} C_{P} x_{P} (t) \\ = B_{C} C_{P} x_{P} (t) + A_{C} x_{C} (t) . \end{matrix} & [Equation 3] \end{matrix}$

$\begin{matrix} \begin{matrix} {\dot{x}}_{W_{1}} (t) = A_{W_{1}} x_{W_{1}} (t) + B_{W_{1}} (w (t) - u_{DO} (t)) \\ = A_{W_{1}} x_{W_{1}} (t) + B_{W_{1}} (w (t) - B_{W_{1}} u_{DO} (t)) \end{matrix} \begin{matrix} {\dot{x}}_{W_{2}} (t) = A_{W_{2}} x_{W_{2}} (t) + B_{W_{2}} (C_{C} x_{C} (t) + D_{C} C_{P} x_{P} (t)) - u_{DO} (t)) \\ = A_{W_{2}} x_{W_{2}} (t) + B_{W_{2}} (C_{C} x_{C} (t) + D_{C} C_{P} x_{P} (t)) - B_{W_{2}} u_{DO} (t)) \\ = B_{W_{2}} D_{C} C_{P} x_{P} (t) + B_{W_{2}} C_{C} x_{C} (t) + A_{W_{2}} x_{W_{2}} (t) - B_{W_{2}} u_{DO} . \end{matrix} & [Equation 4] \end{matrix}$

Meanwhile, based on Equations 1 to 4 above, it may be possible to obtain an output value z1 of the first weight function W1 and an output value z2 of the second weight function W2, which can be expressed by Equation 5 below.

$\begin{matrix} \begin{matrix} z_{1} (t) = C_{W_{1}} x_{W_{1}} (t) + D_{W_{1}} (w (t) - u_{DO} (t)) \\ = C_{W_{1}} x_{W_{1}} (t) + D_{W_{1}} w (t) - D_{W_{1}} u_{DO} (t)), \end{matrix} \begin{matrix} z_{2} (t) = C_{W_{2}} x_{W_{2}} (t) + D_{W_{2}} (C_{C} x_{C} (t) + D_{C} C_{P} x_{P} (t) - u_{DO} (t)) \\ = C_{W_{2}} x_{W_{2}} (t) + D_{W_{2}} C_{C} x_{C} (t) + D_{W_{2}} D_{C} C_{P} x_{P} (t) - D_{W_{2}} u_{DO} (t) \\ = D_{W_{2}} D_{C} C_{P} x_{P} (t) + D_{W_{2}} C_{C} x_{C} (t) + C_{W_{2}} x_{W_{2}} (t) - D_{W_{2}} u_{DO} . \end{matrix} & [Equation 5] \end{matrix}$

Furthermore, state equations for an input and an output of the disturbance observer may be derived as in Equation 6 below, and, from Equations 1 to 5, the parameters shown in Equation 6 may be derived as in Equation 7.

$\begin{matrix} \begin{matrix} \dot{x} (t) = Ax (t) + B_{1} w (t) + B_{2} u_{DO} (t) \\ z (t) = C_{1} x (t) + D_{11} w (t) + D_{12} u_{DO} (t) \\ y_{DO} (t) = C_{2} x (t) + D_{21} w (t) + D_{22} u_{DO} (t), \end{matrix} & [Equation 6] \end{matrix}$

$\begin{matrix} x (t) = {[x_{P}^{T} (t) x_{C}^{T} (t) x_{W_{1}}^{T} (t) x_{W_{1}}^{T} (t)]}^{T}, & [Equation 7] \end{matrix}$

$A = [\begin{matrix} A_{P} + B_{P} D_{C} C_{P} & B_{P} C_{C} & 0 & 0 \\ B_{C} C_{P} & A_{C} & 0 & 0 \\ 0 & 0 & A_{W_{1}} & 0 \\ B_{W_{2}} D_{C} C_{P} & B_{W_{2}} C_{C} & 0 & A_{W_{2}} \end{matrix}], B_{1} = [\begin{matrix} B_{p} \\ 0 \\ B_{W_{1}} \\ 0 \end{matrix}], B_{2} = [\begin{matrix} - B_{p} \\ 0 \\ - B_{W_{1}} \\ - B_{W_{2}} \end{matrix}],$

$C_{1} = [\begin{matrix} 0 & 0 & C_{W_{1}} & 0 \\ D_{W_{2}} D_{C} C_{P} & D_{W_{2}} C_{C} & 0 & A_{W_{2}} \end{matrix}], D_{11} = [\begin{matrix} D_{W_{1}} \\ 0 \end{matrix}], D_{12} = [\begin{matrix} - D_{W_{1}} \\ - D_{W_{2}} \end{matrix}],$

$C_{2} = [C_{P} 000], D_{21} = 0, D_{22} = 0.$

Then, by an electronic device 100, an optimized disturbance observer may be designed based on the output value z1 of the first weight function W1 and the output value z2 of the second weight function W2.

Specifically, as shown in FIG. 2, the electronic device 100 may obtain the first weight function W1 and the second weight function W2 as shown in FIG. 3 based on the output value z1 of the first weight function W1 and the output value z2 of the second weight function W2 for the frequency characteristics of the plant P to be controlled, and may design the disturbance observer based on the acquired W1 and W2.

To be specific, FIG. 4 is an exemplary diagram illustrating an open-loop transfer function of a system to which the first weight function and the second weight function according to an embodiment of the present disclosure have been applied.

It is seen that the open-loop transfer function of the control system where the designed disturbance observer (C*_DO) is combined with the controller C is the most stable.

Furthermore, as shown in FIGS. 5 and 6, it is seen that, in the case of the control system where the designed disturbance observer (C*_DO) is combined with the controller C, performance against disturbances is improved in terms of sensitivity and a torque transfer function.

As an embodiment, in order to verify the control system according to the present disclosure, the output of the plant was observed after inputting the disturbance as in Equation 8 below to the control system.

w(t)=sin(2π50t)+0.5 sin(2π500t)+0.3 sin(2π10000t) [Equation 8]

[75] As shown in FIG. 7, it is seen that the control system including the disturbance observer is less affected by the disturbance than the control system without it.

On the other hand, since disturbances can occur in various frequency bands, it is necessary to check whether the control system has stability even for disturbances having a full range of frequency components.

To be specific, as shown in FIG. 8, by analyzing the output of the plant P to be controlled after applying a random disturbance to the control system, a change in output caused by disturbances was observed. It is seen that, when the designed disturbance observer is applied, the disturbance has less influence and the performance is improved by approximately 10% when comparing the accumulated position error signal (PES).

In the meantime, it is also necessary to analyze the influence of uncertainty of the plant caused by errors in the manufacturing process. In general, control systems that are actually applied have almost no error in a low-frequency region, and have more errors in a high-frequency region so that uncertainty thereof increases. Therefore, as shown in FIG. 9, the plant to be controlled was designed, seeking the control system having an error of 10% in the low-frequency region (100 Hz or less) and an error of 100% in the high frequency region (1 KHz or more).

In this case, as shown in FIG. 10, it is seen that the control system may have robustness in the entire frequency domain. Specifically, when the y-axis (SSV) on the graph in FIG. 10 has a value greater than 10⁰(=1), the robustness does not materialize. However, since the control system according to an embodiment of the present disclosure may not exceed this limit in the entire frequency domain, it may be possible to build a robust control system against errors occurring in the manufacturing process.

Consequently, when using the control system designed according to an embodiment of the present disclosure, it may be possible to secure the ability to eliminate disturbances, to solve the problem of not having robustness due to errors in the manufacturing process, and to keep a closed-loop system stable at all times.

FIG. 11 is a block diagram showing a device according to an embodiment of the present disclosure.

A processor 102 may include one or more cores (not shown) and a graphic processing unit (not shown) and/or a connection path (e.g., a bus) for transmitting and receiving signals to and from other components.

The processor 102 according to an embodiment of the present disclosure may execute one or more instructions stored in a memory 104 to implement the method described in connection with the above-mentioned disclosure.

On the other hand, the processor 102 may further include a random-access memory (RAM; not shown) and a read-only memory (ROM; not shown) that temporarily and/or permanently store signals (or data) processed in the processor 102. In addition, the processor 102 may be in the form of a system on chip (SoC) including at least one of a graphic processing unit, RAM, and ROM.

Programs (one or more instructions) for processing and controlling the processor 102 may be stored in the memory 104. The programs stored in the memory 104 may be divided into a plurality of modules by function.

Steps of the method or the algorithm that has been described in relation to the embodiments of the present disclosure may be implemented directly by hardware, implemented by a software module executed by the hardware, or implemented by a combination thereof. The software module may reside in a random-access memory (RAM), a read-only memory (ROM), an erasable programmable ROM (EPROM), an electrically erasable programmable ROM (EEPROM), a flash memory, a hard disk, a removable disk, a CD-ROM, or any form of computer readable recording media well known in the technical field to which the present disclosure pertains.

The components of the present disclosure may be provided in the form of a program (or application) to be executed in combination with a computer, which is hardware, and stored in a medium. The components of the present disclosure may be executed by software programming or software elements, and, similarly, the embodiments of the present disclosure may include various algorithms in the form of combinations of data structures, processes, routines, or other programming components and may be implemented in programming or scripting languages such as C, C++, Java, and Assembly. The functional aspects may be carried out by an algorithm running on one or more processors.

Although the embodiments of the present disclosure have been described with reference to the accompanying drawings, a person having ordinary skills in the technical field to which the present disclosure belongs will be able to understand that the present disclosure can be embodied in other specific forms without changing its technology or essential features. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

There may be provided the system including the robust optimal disturbance observer for high-precision position control performed by the electronic device according to an aspect of the present disclosure for achieving the above-mentioned purpose, including: the plant P to be controlled; the controller C; the first weight function W1; the second weight function W2; and the disturbance observer, wherein the first weight function W1 may receive a difference value between a disturbance w and an output u_DOof the disturbance observer as an input value, the second weight function W2 may receive a difference value between an output value of the controller C and the output u_DOof the disturbance observer as an input value, the plant P to be controlled may receive, as an input value, a sum value of the disturbance w and the difference value between the output value of the controller C and the output u_DOof the disturbance observer, and the controller C may receive an output value of the plant P to be controlled as an input value.

SYSTEM COMPRISING ROBUST OPTIMAL DISTURBANCE OBSERVER FOR HIGH-PRECISION POSITION CONTROL PERFORMED BY ELECTRONIC DEVICE, AND CONTROL METHOD THEREFOR

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