CN114527655B - Periodic interference suppression and signal tracking method based on improved FDRC - Google Patents

Periodic interference suppression and signal tracking method based on improved FDRC Download PDF

Info

Publication number
CN114527655B
CN114527655B CN202210105248.9A CN202210105248A CN114527655B CN 114527655 B CN114527655 B CN 114527655B CN 202210105248 A CN202210105248 A CN 202210105248A CN 114527655 B CN114527655 B CN 114527655B
Authority
CN
China
Prior art keywords
finite
controller
dimension
stability
closed loop
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN202210105248.9A
Other languages
Chinese (zh)
Other versions
CN114527655A (en
Inventor
张会娟
祝瑞璞
张弛
姬淼鑫
袁航
赵志科
冯伟
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Henan University of Technology
Original Assignee
Henan University of Technology
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Henan University of Technology filed Critical Henan University of Technology
Priority to CN202210105248.9A priority Critical patent/CN114527655B/en
Publication of CN114527655A publication Critical patent/CN114527655A/en
Application granted granted Critical
Publication of CN114527655B publication Critical patent/CN114527655B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • GPHYSICS
    • G05CONTROLLING; REGULATING
    • G05BCONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B13/00Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion
    • G05B13/02Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion electric
    • G05B13/04Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion electric involving the use of models or simulators
    • G05B13/042Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion electric involving the use of models or simulators in which a parameter or coefficient is automatically adjusted to optimise the performance
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/40Arrangements for reducing harmonics

Landscapes

  • Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Artificial Intelligence (AREA)
  • Computer Vision & Pattern Recognition (AREA)
  • Evolutionary Computation (AREA)
  • Medical Informatics (AREA)
  • Software Systems (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Automation & Control Theory (AREA)
  • Feedback Control In General (AREA)

Abstract

The invention discloses a periodic interference suppression and signal tracking method based on improved finite-dimension repetitive control, which comprises the following steps: firstly, designing a classical controller to ensure the stability of a closed loop system under the action of a periodic interference signal and a reference signal; then designing an improved finite-dimension repetitive controller, and connecting the controller with an original closed-loop controller in parallel to form a composite controller, so that periodic interference signal suppression and reference signal tracking are realized; and finally, selecting a convergence coefficient according to the phase range of the system function, and designing a compensation link according to the convergence coefficient to improve the stability margin of the system. The invention adopts parallel finite dimension repetitive control, reduces the influence of infinite poles on the stability of the system, and simultaneously solves the problems of poor system stability and the like caused by interference signal amplification and phase lag in a non-harmonic frequency band of the traditional serial finite dimension repetitive control; the parallel structure is adopted, the control system is simple in structure, and parameters are easy to adjust.

Description

Periodic interference suppression and signal tracking method based on improved FDRC
Technical Field
The invention belongs to the field of periodic interference suppression and signal tracking, and particularly relates to an improved parallel finite-dimension repetitive control method which is used for suppressing periodic interference signals and tracking periodic reference signals.
Background
Periodic signals are common in rotating machinery systems, uninterruptible power supplies, energy storage converters, such as displacement signals in magnetic levitation motors, machine tools, hard disks, etc., harmonic current signals of uninterruptible power supplies and energy storage converters. In practical systems, it is generally required to suppress a periodic interference signal or track a reference signal, and currently, common methods include iterative control, adaptive control, wave trap, and repetitive control. The iterative control algorithm has poor self-adaptability and robustness and is sensitive to uncertain disturbance; although the adaptive control algorithm does not need an accurate mathematical model, it is difficult to achieve complete compensation for periodic disturbances; the method of designing the wave trap is easy, the calculated amount is small, but the inhibition capability is very limited. The repetitive control is a widely used control method at present, can effectively inhibit periodic interference which has known period, uncertain amplitude and multiple frequency components, and has the advantages of simple structure, small calculated amount, small occupied memory and the like, but the addition of the repetitive controller leads the closed loop system to introduce infinite virtual poles, thereby influencing the stability of the system. In order to improve the stability of the closed-loop system, the improved repetitive control is connected with a low-pass filter in series before a time lag link to filter out high-frequency poles, so that the effect of repetitive control on periodic signals and the stability of the closed-loop system are closely related to the low-pass filter.
Depending on the spectral characteristics of the periodic signal, the periodic signal spectrum is primarily focused on the first few lower harmonic frequencies. High-precision interference suppression and reference signal tracking can be realized by only eliminating main low-order harmonic frequency components. The Finite Dimensional Repetitive Control (FDRC) has a finite number of virtual poles, so that the influence of an infinite number of virtual poles introduced by the repetitive control on the stability of the system is reduced. The conventional finite-dimension repetition usually adopts a serial form, and serial finite-dimension repetition control is connected with an original system controller in series to realize the suppression of periodic interference signals or the tracking of reference signals. However, the serial limited dimension repetitive control has the problems of interference signal amplification, phase lag and the like in a non-harmonic frequency band, and causes the problems of poor system stability, poor inhibition or tracking precision and the like. Therefore, there is a need for improved forms of limited-dimensional repetitive control that achieve high accuracy periodic interference suppression and signal tracking while guaranteeing closed-loop system stability.
Disclosure of Invention
The invention aims to solve the technical problems that: the invention overcomes the defects of the prior art, and discloses an improved method for realizing periodic interference suppression and signal tracking by adopting a mode that a parallel finite-dimension repetitive controller is connected with an original closed-loop controller in parallel to form a composite controller, and design controller parameters according to a root locus method so as to realize periodic interference suppression and reference signal tracking on the basis of guaranteeing the closed-loop stability of a control system.
The technical scheme adopted for solving the technical problems is as follows:
a method for improved finite-dimension repetitive control includes designing a classical controller to ensure stability of an original closed-loop system; then designing an improved finite-dimension repetitive controller, and connecting the controller in parallel with the original closed-loop controller to form a composite controller; and finally, selecting a convergence coefficient according to the phase range of the system function, reasonably designing a compensation link according to the convergence coefficient to improve the stability of the system, and realizing high-precision periodic interference suppression and reference signal tracking.
The specific steps of the invention are as follows:
(1) Classical closed-loop controller design, ensuring the basically stable closed-loop system
Design classical closed loop controller G c And(s) ensuring the stability of the closed loop system under the action of the periodic reference signal R(s) and the interference signal D(s), namely ensuring that all characteristic roots of the closed loop system are on the left half plane of the complex plane.
(2) Improved finite dimension repetitive controller design
Improved finite-dimension repetitive controller C fd (s) modifying the conventional series-form finite-dimension repetitive controller into a parallel-form, wherein the expression is as follows:
Figure BDA0003493740140000021
wherein C is f,i (s) is an i-th order basic finite dimension repetitive controller; lambda (lambda) i As a convergence coefficient, the value of the convergence coefficient not only determines the convergence speed of the system, but also influences the stability of the system; k (K) i (s) is a compensation link, compensation C f,i (s) the influence of the introduced closed loop virtual pole on the system stability is improved, and the stability margin is improved; m is the order of the finite-dimension repetitive controller and is determined by the system interference suppression precision or the signal tracking precision.
Improved finite-dimension repetitive controller C fd (s) and original closed-loop controller G c (s) are connected in parallel to form a composite controller, so that the periodic interference signal suppression and the reference signal tracking are realized.
Under the action of the periodic reference signal R(s) and the interference signal D(s), the closed loop system error E(s) is as follows:
Figure BDA0003493740140000031
as is clear from the above, when i is not more than m,
Figure BDA0003493740140000032
the amplitude gain of the systematic error is 0, indicating that the improved finite-dimension repetitive controller can effectively track and suppress the periodic reference signal R(s) and the interference signal D(s) with the frequency of iΩ.
(3) Parameter design and system stability analysis
Closed loop system incorporates an improved finite-dimension repetitive controller C f,i After(s), the control system introduces m pairs of virtual poles, so that the stability margin of the system is reduced, and the closed loop system is in a critical stable state. To ensure the stability of the closed loop system, K is adopted i And(s) correcting the closed loop system to realize high-precision periodic interference suppression and signal tracking.
According to the root locus method, the improved finite-dimension repeated control parameter design comprises the following steps: first according to the system function R i-1 (s) determination of convergence coefficient lambda for phase-frequency characteristics i Sign, lambda of i The sign selection principle of (2) enables the compensation link to provide a phase compensation angle as small as possible; then according to lambda i Symbol determination compensation element K i (s) let R be i-1 (s)K i (s) satisfying a phase condition capable of ensuring the stability of the closed loop system at ω=iΩ:
Figure BDA0003493740140000033
compared with the prior art, the invention has the following advantages:
(1) The invention adopts parallel finite dimension repetitive control, avoids the influence of introducing infinite poles on the system stability, and solves the problems of poor system stability and the like caused by interference signal amplification and phase lag in a non-harmonic frequency band in the traditional serial finite dimension repetitive control;
(2) The parallel finite-dimension repetitive controller designed by the invention can reasonably select the order according to the system control precision and the system hardware, and reduce the calculated amount of the control system;
(3) The controller designed by the invention adopts a parallel structure, the original closed-loop controller can not be changed, the control system has simple structure, and the parameters are easy to adjust;
(4) The invention designs the compensation link, can effectively improve the stability margin of the control system and enhance the anti-interference capability of the control system.
Drawings
FIG. 1 is a flow chart of the design of the present invention;
FIG. 2 is a schematic diagram of periodic interference suppression and signal tracking based on improved finite dimensional repetitive control;
FIG. 3 is a graph of parallel finite dimension repetitive control frequency characteristics;
fig. 4 is a series finite-dimension repetitive control frequency characteristic curve.
Detailed Description
The invention is further described with reference to the drawings and specific steps of implementation.
As shown in fig. 1, the specific implementation steps of the present invention are as follows:
(1) Classical closed-loop controller design, ensuring the basically stable closed-loop system
As shown in fig. 2, a classical closed loop controller G is designed c And(s) ensuring the stability of the closed loop system under the action of the periodic reference signal R(s) and the interference signal D(s), namely ensuring that all characteristic roots of the closed loop system are on the left half plane of the complex plane. Wherein R(s) and D(s) are a periodic reference signal and an interference signal respectively, and the period is T; g p (s) is a controlled object transfer function; e(s) is the systematic error.
(2) Improved finite dimension repetitive controller design
Improved finite-dimension repetitive controller C fd (s) modifying the conventional series-form finite-dimension repetitive controller into a parallel-form, wherein the expression is as follows:
Figure BDA0003493740140000041
wherein C is f,i (s) is an i-th order basic finite dimension repetitive controller; lambda (lambda) i As a convergence coefficient, the value of the convergence coefficient not only determines the convergence speed of the system, but also influences the stability of the system; k (K) i (s) an advanced correction compensation step for the ith-order basic finite-dimension repetitive controller, compensating C f,i (s) the influence of the introduced closed loop virtual pole on the system stability is improved, and the stability margin is improved; m is the order of the finite-dimension repetitive controller, and is determined by the control precision of the system and the system hardware, so that the calculated amount of the control system is reduced.
Ith-order basic finite-dimension repetitive controller C f,i (s) is expressed as:
Figure BDA0003493740140000051
where Ω=2ρt is the fundamental frequency of the periodic signal.
In order to compare the advantages of the improved parallel finite-dimension repetitive controller provided by the invention, the invention provides K at 200Hz i (s)=1,m=5,λ i When=1m, the improved parallel and conventional series finite-dimension repetitive control frequency characteristic curves. As shown in fig. 3, the improved finite dimensional repetitive control is carried out at each harmonic frequency, the amplitude gain is infinite, and the phase is changed by 180 degrees; the amplitude gain at non-harmonic frequencies is almost zero and the phase is approximately an integer multiple of 2 pi. As shown in fig. 4, the amplitude gain at each harmonic frequency is infinity while the amplitude gain at non-harmonic frequencies is not zero by the conventional tandem finite-dimension repetitive controller, i.e., the addition of the tandem finite-dimension repetitive controller amplifies the signal at non-harmonic frequencies while suppressing periodic disturbances and tracking the periodic reference signal. In addition, the series-connection type finite-dimension repetitive control has certain phase lag at the non-harmonic frequency, and has great influence on the stability of a closed-loop system. Therefore, the invention provides improved finite dimensional repetitive controlThe method is superior to the traditional series limited-dimensional repetitive control.
As shown in fig. 2, the improved finite-dimension repetitive controller C fd (s) and original closed-loop controller G c (s) are connected in parallel to form a composite controller. Under the action of the periodic reference signal R(s) and the interference signal D(s), the closed loop system error E(s) is as follows:
Figure BDA0003493740140000052
as is clear from the formula (3), when i is not more than m,
Figure BDA0003493740140000053
the amplitude gain of the systematic error is 0, indicating that the improved finite-dimension repetitive controller can effectively track and suppress the periodic reference signal R(s) and the interference signal D(s) with the frequency of iΩ.
(3) Parameter design and system stability analysis
Closed loop system incorporates an improved finite-dimension repetitive controller C f,i After(s), the control system introduces m pairs of virtual poles, so that the stability margin of the system is reduced, and the closed loop system is in a critical stable state. To ensure the stability of the closed loop system, K is adopted i And(s) correcting the closed loop system to realize high-precision periodic interference suppression and reference tracking. Thus lambda is i And K i The parameter design of(s) plays a crucial role in the stability of the closed loop system.
As can be seen from fig. 2, the characteristic equation of the closed loop system after adding the m-order parallel finite dimensional repetitive controller is:
Figure BDA0003493740140000061
in which Q 0 (s)=1+G c (s)G p And(s) is a characteristic polynomial of the original closed-loop system.
When the closed loop system joins C f,i (s) when the closed loop system is added with the previous i-1 order finite dimensional repetitive controller and the system is stable, the closed loop system is at the momentThe effective characteristic equation is:
Q i (s)=[s 2 +(iΩ) 2 ]Q i-1 (s)+λ i G p (s)K i (s)(s+iΩ) 2 =0 (5)
in which Q i-1 (s) is a system characteristic polynomial containing a first i-1 order parallel finite dimension repetitive controller, wherein characteristic roots are all positioned on the left half plane of a complex plane, and the expression is as follows:
Figure BDA0003493740140000062
to ensure the addition of C f,i (s) stability of post-closed loop system, compensation Link K i The design of(s) should ensure that all feature roots of equation (6) lie in the left half plane of the complex plane.
Definition of the definition
Figure BDA0003493740140000063
As a system function. According to the root locus method, the compensation link K i The design of(s) should be such that the following formula satisfies the phase condition at s= ±ijΩ: />
Figure BDA0003493740140000064
Wherein arg () represents the argument; l is an integer.
Therefore, the steps of the improved finite-dimension repetitive control parameter design are as follows: first according to the system function R i-1 (s) determination of phase-frequency characteristics lambda i Sign, lambda of i The sign selection principle of (2) enables the compensation link to provide a phase compensation angle as small as possible; then according to lambda i Symbol determination compensation element K i (s) let R be i-1 (s)K i (s) satisfies a phase condition capable of ensuring the stability of the closed loop system at ω=iΩ.
What is not described in detail in the present specification belongs to the prior art known to those skilled in the art.
Finally, it should be noted that the above-mentioned embodiments are only for illustrating the technical scheme of the present invention and are not limiting; while the invention has been described in detail with reference to the preferred embodiments, those skilled in the art will appreciate that: modifications may be made to the specific embodiments of the present invention or equivalents may be substituted for part of the technical features thereof; without departing from the spirit of the invention, it is intended to cover the scope of the invention as claimed.

Claims (1)

1. The periodic interference suppression and signal tracking method based on the improved finite-dimension repetition control is characterized by comprising the following steps of:
step one, designing a classical controller G c (s) ensuring the stability of the closed loop system under the action of the periodic reference signal R(s) and the interference signal D(s), namely ensuring that all characteristic roots of the closed loop system are on the left half plane of the complex plane;
step two, designing an improved finite-dimension repetitive controller C fd (s) connecting the controller in parallel with the original closed-loop controller to form a composite controller;
improved finite-dimension repetitive controller C fd (s) to improve the traditional series-form finite-dimension repetitive controller into a parallel-form, the expression is as follows:
Figure FDA0004116739000000011
wherein C is f,i (s) is an ith order basic finite dimension repetitive controller, lambda i For convergence factor, K i (s) is a compensation link, m is the order of the finite-dimension repetitive controller;
step three, designing parameters of a closed loop system and analyzing the stability of the system, and selecting a convergence coefficient according to the phase range of a system function so as to enable a compensation link to provide a phase compensation angle as small as possible;
the system stability is improved according to the sign design compensation link of the convergence coefficient, and high-precision periodic interference suppression or signal tracking is realized;
for lambda i And K i Parameter design of(s):
the characteristic equation of the closed loop system after the m-order parallel finite-dimension repetitive controller is added is as follows:
Figure FDA0004116739000000012
in which Q 0 (s)=1+G c (s)G p (s) is a feature polynomial of the original closed-loop system;
when the closed loop system joins C f,i (s) when the closed loop system is added with the first i-1 order finite dimensional repetitive controller and the system is stable, the equivalent characteristic equation of the closed loop system is as follows:
Q i (s)=[s 2 +(iΩ) 2 ]Q i-1 (s)+λ i G p (s)K i (s)(s+iΩ) 2 =0
wherein Ω is the fundamental frequency of the periodic signal; g p (s) is a controlled object transfer function; q (Q) i-1 (s) is a system characteristic polynomial containing a first i-1 order parallel finite dimension repetitive controller, wherein characteristic roots are all positioned on the left half plane of a complex plane, and the expression is as follows:
Figure FDA0004116739000000021
definition of the definition
Figure FDA0004116739000000023
Is a system function; according to the root locus method, the compensation link K i The design of(s) is such that the following satisfies the phase condition at s= ±ijΩ:
Figure FDA0004116739000000022
/>
wherein arg () represents the argument; l is an integer;
first according to the system function R i-1 (s) determination of phase-frequency characteristics lambda i Is used in the sign of (a),λ i the sign selection principle of (2) enables the compensation link to provide a phase compensation angle as small as possible;
then according to lambda i Symbol determination compensation element K i (s) let R be i-1 (s)K i (s) the phase condition is satisfied at frequency ω=iΩ.
CN202210105248.9A 2022-01-28 2022-01-28 Periodic interference suppression and signal tracking method based on improved FDRC Active CN114527655B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202210105248.9A CN114527655B (en) 2022-01-28 2022-01-28 Periodic interference suppression and signal tracking method based on improved FDRC

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202210105248.9A CN114527655B (en) 2022-01-28 2022-01-28 Periodic interference suppression and signal tracking method based on improved FDRC

Publications (2)

Publication Number Publication Date
CN114527655A CN114527655A (en) 2022-05-24
CN114527655B true CN114527655B (en) 2023-06-09

Family

ID=81623611

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202210105248.9A Active CN114527655B (en) 2022-01-28 2022-01-28 Periodic interference suppression and signal tracking method based on improved FDRC

Country Status (1)

Country Link
CN (1) CN114527655B (en)

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3751239B2 (en) * 2001-09-28 2006-03-01 横河電子機器株式会社 Automatic steering apparatus and method
CN106444372B (en) * 2016-08-25 2019-05-31 浙江工业大学 Sliding formwork repetitive controller for motor servo system
CN106655274A (en) * 2017-02-23 2017-05-10 湘潭大学 Control method for grid-connected current of three-phase grid-connected inverter
CN107844052B (en) * 2017-10-14 2020-11-10 河南工业大学 Method for suppressing harmonic current of magnetic bearing system based on parallel finite dimension repeated control
CN109240077A (en) * 2018-10-09 2019-01-18 台州学院 Discrete multicycle repetitive controller for period servo-system
CN110412876B (en) * 2019-08-18 2022-02-08 台州学院 Inverter repetitive control method based on attraction law
CN112068423B (en) * 2020-08-06 2024-06-18 浙江工业大学 Design method of finite power attraction repetitive controller

Also Published As

Publication number Publication date
CN114527655A (en) 2022-05-24

Similar Documents

Publication Publication Date Title
CN108649780B (en) LCL filter parameter optimization method considering inverter stability under weak grid
CN110635707A (en) Three-phase LCL inverter control method and device based on harmonic interference observer
CN114142781B (en) Method for adjusting PI parameters of current loop of pre-filter permanent magnet synchronous motor
CN105224811A (en) A kind of PMU dynamic data processing method based on feedback iteration formula frequency-tracking
CN112612208B (en) Plug-in type improved repetitive control method
CN114884125A (en) High-stability control method for LCL type grid-connected inverter system under weak power grid
CN113036784A (en) Flexible-direct high-frequency oscillation control method and system based on hysteresis link
CN114865633A (en) Self-adaptive quasi-PR active damping low-frequency harmonic suppression method
CN114442485B (en) Design method of universal fractional order multi-period characteristic harmonic repetitive controller and controller
CN114527655B (en) Periodic interference suppression and signal tracking method based on improved FDRC
CN116565944A (en) Synchronous frequency adaptive resonance-based negative sequence voltage compensation method for grid-structured converter
CN113824160A (en) Adaptive virtual inductor-based micro-grid parallel inverter power regulation method
CN107919668B (en) Active power filter and control method thereof
CN113258615B (en) Grid-connected inverter frequency self-adaptive control method, device, equipment and storage medium
CN116191912A (en) Current control method for energy storage converter
CN109165474B (en) Inverter repetitive control design method based on neural network
CN115842468A (en) Harmonic active suppression optimization method based on improved search algorithm
CN114597975A (en) Power distribution method and control equipment for parallel system
CN114675532A (en) Design method of fractional order multicycle 6k +/-1 harmonic repetition controller and controller
CN113541209A (en) Frequency self-adaptive phase locking method based on three-phase energy storage inverter closed-loop system
CN110880881A (en) Electric energy quality control method of four-bridge arm inverter and embedded repetitive controller thereof
CN113629751B (en) Phase-locked loop phase compensation method and system for high-frequency oscillation control of flexible direct system
CN110880784A (en) Current frequency self-adaptive repetitive control method for grid-connected inverter
US20230396196A1 (en) Method and device for determining current of electric motor or generator
Wang et al. Active disturbance rejection control of three-phase LCL power conversion system under non-ideal grid conditions

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant