Method and device for online global optimization of feedback control parameters of radio frequency low-level system

Abstract

The present invention discloses a method and device for online global optimization of RF low-level system feedback control parameters, including: generating parameter scanning grids of parameter α and α, wherein α is proportional gain and α is integral gain; using an "S" type path to scan the parameter scanning grid to obtain several PI parameter combinations; collecting the cavity pressure signal of the RF cavity under each set of PI parameters; calculating the rms mean of the cavity pressure based on the cavity pressure signal of each set of PI parameters; making a contour map based on the rms mean of the cavity pressure, and obtaining the best PI parameter combination based on the contour map. Therefore, the present invention can effectively adjust the PI parameters, not only can find the globally optimal PI parameters, but also can avoid loop instability.

Description

Technical Field

[0001] The invention relates to a method, a device, a equipment and a medium for online global optimization of feedback control parameters of a radio frequency low-level system, and relates to the field of particle accelerators. Background Art

[0002] In a particle accelerator, the RF cavity is mainly used to provide an acceleration field for the particle beam and is the core component of the accelerator. The beam is easily affected by various factors during the acceleration process of the RF cavity, especially in superconducting linear accelerators. The instability of the high-Q superconducting RF system caused by accidental factors can easily lead to poor beam quality or even beam loss. The low-level RF control system can achieve precise control of the RF field and is a key factor in determining the beam quality.

[0003] With the rapid development of microelectronics and digital chip technology, the new generation of particle accelerators generally adopts digital low-level systems (LLRF). Among them, digital proportional and integral control (PI control) controllers are widely used in accelerator digital low-level systems due to their simple structure, model independence, good adaptability and strong reliability. One of the application difficulties of PI control is the difficulty of parameter tuning. Traditional PI parameter tuning methods mostly emphasize dynamic indicators, such as: rise time, peak time, loop overshoot of step response, etc.; or calculate loop parameters (such as cutoff frequency, gain margin, damping ratio) according to the mathematical model of transfer function, and then complete parameter tuning based on engineer experience. However, in the field of low-level RF, the stability of the cavity pressure signal in steady state is directly related to the longitudinal indicators of the beam (such as beam energy dispersion, etc.), which is the core requirement of particle accelerators. Traditional tuning methods do not fully consider this factor. In addition, the RF loop usually contains a variety of nonlinear factors (such as: nonlinear RF power source system, nonlinear Lorentz detuning, etc.), and the tuning method based on the linear model of the transfer function is no longer applicable.

[0004] Advanced foreign laboratories represented by the German Electron Synchrotron Radiation Research Center (DESY) and the High Energy Accelerator Research Organization (KEK) in Japan usually use a two-dimensional parameter scanning method to achieve PI parameter tuning. The basic idea is: give the adjustable ranges of the P parameter and the I parameter in advance; then fix the P parameter, scan the I parameter point by point in turn, and record the stability of the cavity pressure signal under each set of PI parameters; increase the P parameter, scan the I parameter point by point in turn, and record the stability of the cavity pressure signal under each set of PI parameters; repeat this process, and finally obtain a two-dimensional contour map, whose horizontal and vertical coordinates are the PI parameters, and the data on the contour line are the stability of the cavity pressure signal. However, this method has some problems in practical applications. The most critical difficulty is that under certain PI parameters, the poles of the system may be close to the negative semi-axis region of the complex plane, resulting in loop instability during the scanning process. In order to eliminate loop instability, it is necessary to select the adjustable range of the PI parameter as conservatively as possible, which makes it difficult to find the global optimal position in the scanned two-dimensional contour map.

[0005] In summary, the setting of PI parameters is related to the stability of the RF field and the longitudinal index of the particle beam. Due to the particularity of the accelerator RF system itself, the traditional parameter setting method is no longer applicable. The two-dimensional scanning method proposed in the prior art also faces some problems in practical application. It is difficult to lock the optimal parameter position, which restricts its comprehensive promotion and application in the field of particle accelerators. Summary of the invention

[0006] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, in view of the above problems, the purpose of the present invention is to provide a method, device, equipment and medium for online global optimization of feedback control parameters of a radio frequency low-level system, which can effectively adjust the PI parameters, not only find the global optimal PI parameters, but also avoid loop instability.

[0007] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is:

[0008] In a first aspect, the present invention provides a method for online global optimization of feedback control parameters of a radio frequency low-level system, comprising:

[0009] Generate Parameters and parameters The parameter sweep grid is is the proportional gain, is the integral gain;

[0010] The parameter scanning grid was scanned using an “S”-shaped path to obtain several PI parameter combinations;

[0011] Collect the cavity pressure signal of the RF cavity under each set of PI parameters;

[0012] Based on the cavity pressure signal of each set of PI parameters, the rms mean of the cavity pressure is calculated;

[0013] A contour map was made based on the rms mean of the cavity pressure, and the optimal PI parameter combination was obtained based on the contour map.

[0014] In one possible implementation, the parameters are generated and parameters The parameter sweep grid includes:

[0015] Determine the parameters With parameters The boundary value of

[0016] Based on the determined boundary values, the indivual Parameter Set and indivual Parameter Set , and obtain the parameter sweep grid.

[0017] In one possible implementation, the parameter scanning grid is:

[0018] .

[0019] In one possible implementation, the parameters With parameters The process of the boundary value is:

[0020] parameter The process of determining the boundary value of is as follows: Set to 0 and gradually increase Until the feedback loop oscillates due to excessive gain, The value is recorded as Set the maximum value of the network scan 0.7~0.8 times ; Minimum Should be less than 1 / 50 of

[0021] parameter The process of determining the boundary value of is as follows: The maximum value of Set as cavity half bandwidth ω 0.5 100 times of ,parameter r Minimum value of r 1Set to ω 0.5 1 / 10~1 / 2 of.

[0022] In one possible implementation, an “S”-shaped path is used to scan the parameter scanning grid to obtain several PI parameter combinations. The specific process is as follows: the minimum parameter pair ( K p1 , r 1) Start scanning and keep the proportional gain first K p1 Unchanged, scan parameters from small to large r ; When the parameter r Scan to maximum value r m When , the scanning parameter pair is ( K p1 , r m ), the next scan parameter pair is ( K p2 , r m ), and then proceed in sequence to complete the "S" type scanning path, generating PI parameter combinations, specifically:

[0023] .

[0024] In a possible implementation, based on the cavity pressure signal under each set of PI parameters, the rms mean of the cavity pressure is calculated, and the specific process is as follows:

[0025] The collected cavity pressure signal V c The plural form is V c =| V c | e j∠Vc , where | V c | is the amplitude, ∠ V c is the phase;

[0026] For a single measurement, the amplitude stability index and phase stability index are calculated as follows:

[0027] ;

[0028] in, n is the total number of collections, For the i The measured cavity pressure amplitude, For the i The cavity pressure phase measured by and represent the mean of amplitude and phase respectively, and The smaller it is, the more stable the cavity pressure is;

[0029] For each set of PI parameters, multiple measurements were performed and the average was calculated to obtain the rms mean of the cavity pressure.

[0030] In a possible implementation, a contour map is produced based on the rms mean value of the cavity pressure, and an optimal PI parameter combination is obtained based on the contour map, including:

[0031] Based on the rms mean values ​​of the amplitude and phase of the cavity pressure under different PI parameter combinations, a two-dimensional contour map is obtained, whose horizontal and vertical axes are the parameters and parameters, the data on the contour line are the rms radius of the cavity pressure signal;

[0032] In the contour map, always look for the closed curve with the smallest rms value, and its center position is the optimal PI parameter , when there are multiple closed curves with equal rms values, select Smaller closed curve.

[0033] In a second aspect, the present invention further provides a device for online global optimization of RF low-level system feedback control parameters, the device comprising:

[0034] A parameter generation unit configured to generate parameters and parameters The parameter sweep grid is is the proportional gain, is the integral gain;

[0035] A scanning unit is configured to scan a parameter scanning grid using an "S"-shaped path to obtain a plurality of PI parameter combinations;

[0036] A cavity pressure acquisition unit is configured to acquire a cavity pressure signal of the radio frequency cavity under each set of PI parameters;

[0037] an rms calculation unit, configured to calculate an rms mean value of the cavity pressure based on the cavity pressure signal under each set of PI parameters;

[0038] The control parameter acquisition unit is configured to make a contour map based on the rms mean value of the cavity pressure, and acquire the best PI parameter combination based on the contour map.

[0039] In a third aspect, the present invention further provides an electronic device, comprising:

[0040] at least one processor; and

[0041] A memory communicatively connected to the processor; wherein,

[0042] The memory stores instructions executable by the processor, and the instructions are executed by the processor to enable the processor to perform any one of the methods described above.

[0043] In a fourth aspect, the present invention further provides a computer-readable storage medium storing one or more programs, wherein the one or more programs include computer instructions, and the computer instructions are used to enable a computer to execute any one of the methods described.

[0044] The present invention adopts the above technical solution, and has the following characteristics:

[0045] 1. The present invention can scan within a wider parameter range, thereby effectively locking the global optimal PI parameter combination; at the same time, by optimizing the scanning path and scanning mode, loop instability is avoided, ensuring the stable operation of the system.

[0046] 2. The present invention can be deployed inside an existing digital low-level system to achieve online optimization of PI parameters.

[0047] In summary, the present invention can be widely applied to feedback parameter optimization of particle accelerator LLRF system. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Throughout the accompanying drawings, the same reference numerals are used to represent the same components. In the accompanying drawings:

[0049] Figure 1 This is the schematic diagram of the PI controller of the LLRF system.

[0050] Figure 2 Schematic diagram of traditional PI parameter scanning. (a) The traditional PI scanning method is prone to loop instability in the unstable area shown in the figure, and the optimal PI parameter combination usually appears on the scanning boundary after narrowing the scanning area; (b) is the contour map of the traditional PI scanning method when adjusting the stability of the cavity pressure phase; (c) is the cavity pressure oscillation phenomenon in the upper left corner of the traditional PI scanning method.

[0051] Figure 3 The scanning area obtained by the traditional PI scanning method and the scanning area obtained by the PI scanning method proposed in the embodiment of the present invention are compared.

[0052] Figure 4 Figure 1 is a schematic diagram for comparing scanning schemes, wherein Figure (a) is a traditional "N" type parameter scanning scheme; Figure (b) is a scanning scheme implemented in an embodiment of the present invention. “S” type parameter sweep scheme for parameter tuning.

[0053] Figure 5 The low-level online measurement of the superconducting cavity voltage signal of the embodiment of the present invention , and Experimental block diagram.

[0054] Figure 6 This is a flow chart of a method for online global optimization of feedback control parameters of a radio frequency low-level system proposed in an embodiment of the present invention.

[0055] Figure 7 1 is an example of the use of an embodiment of the present invention in a CAFe device, wherein (a) is an rms radius heat map of the cavity pressure amplitude and phase obtained by scanning the method proposed in the present invention on CM2-4 of the CAFe device according to an embodiment of the present invention; (b) is an rms radius heat map of the cavity pressure amplitude and phase obtained by scanning the method proposed in the present invention on CM2-5 of the CAFe device according to an embodiment of the present invention; and (c) is an rms radius heat map of the cavity pressure amplitude and phase obtained by scanning the method proposed in the present invention on CM2-6 of the CAFe device according to an embodiment of the present invention.

[0056] Figure 8 This is a structural diagram of an electronic device of the present invention. DETAILED DESCRIPTION

[0057] It should be understood that the terms used herein are only for the purpose of describing specific example embodiments and are not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms "one", "an" and "said" as used herein may also be meant to include plural forms. The terms "include", "comprise", "contain", and "have" are inclusive, and therefore specify the existence of stated features, steps, operations, elements and / or parts, but do not exclude the existence or addition of one or more other features, steps, operations, elements, parts, and / or combinations thereof. The method steps, processes, and operations described herein are not interpreted as necessarily requiring them to be performed in the specific order described or illustrated, unless the execution order is clearly indicated. It should also be understood that additional or alternative steps may be used.

[0058] Although the terms first, second, third, etc. can be used in the text to describe multiple elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms can only be used to distinguish an element, component, region, layer or section from another region, layer or section. Unless the context clearly indicates, terms such as "first", "second" and other numerical terms do not imply order or sequence when used in the text. Therefore, the first element, component, region, layer or section discussed below can be referred to as the second element, component, region, layer or section without departing from the teaching of the example embodiments.

[0059] For ease of description, spatially relative terms may be used herein to describe the relationship of one element or feature relative to another element or feature as shown in the figures, such as "inside", "outside", "inner side", "outer side", "below", "above", etc. Such spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation depicted in the figures.

[0060] The two-dimensional scanning method proposed in the prior art also faces some problems in practical application, and it is difficult to lock the optimal parameter position, which restricts its comprehensive promotion and application in the field of particle accelerators. The method, device, equipment and medium for online global optimization of the feedback control parameters of the radio frequency low-level system provided by the present invention include: generating parameters and parameters The parameter sweep grid is is the proportional gain, is the integral gain; the "S" type path scanning parameter scanning grid is used to obtain several PI parameter combinations; the cavity pressure signal of the RF cavity under each set of PI parameters is collected; based on the cavity pressure signal of each set of PI parameters, the rms mean of the cavity pressure is calculated; a contour map is made based on the rms mean of the cavity pressure, and the best PI parameter combination is obtained based on the contour map. Therefore, the present invention can effectively adjust the PI parameters, not only can the global optimal PI parameters be found, but also the loop instability phenomenon can be avoided.

[0061] The exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0062] PID control is a classic control strategy, widely used in industrial automation and process control. Since the RF system emphasizes the steady-state performance of the loop, PID control is often simplified to PI control in the LLRF (low-level control) field. Figure 1 As shown in the figure, the PI controller adjusts the system output through two gain links: proportional gain P and integral gain I. Proportional control adjusts the control output through the current error value, providing fast response and reducing transient errors. Integral control adjusts the control output through the accumulated error, eliminating the steady-state error of the system and improving the accuracy of the system.

[0063] In the RF cavity, the control relationship between the output and input of PI control is as follows:

[0064]

[0065] in, is the voltage signal output by the PI controller, such as Figure 1 As shown, in the RF low-level loop, the PI controller output is generally directly transmitted to the solid-state amplifier SSA through the analog-to-digital converter DAC. is the proportional gain, is the integral gain, It's time The error signal, is from the initial time 0 to the time The error integral of .

[0066] By performing Laplace transform on the above equation and assuming that the Laplace transform of the error signal is , then the above formula can be transformed into:

[0067]

[0068] in, is the transfer function, which is the output With input ratio.

[0069] Note that in the LLRF system, two basic cavity pressure feedback loops are usually included. In the amplitude phase control mode, one loop is used to control the amplitude of the cavity pressure, and the other loop is used to control the phase of the cavity pressure. In the I / Q control mode, one loop is used to control the in-phase component of the cavity pressure, and the other loop is used to control the orthogonal component of the cavity pressure. The present invention mainly relates to the amplitude phase control mode, and the I / Q control mode is similar to it and will not be described in detail. In order to distinguish the amplitude and phase control loops, the PI parameters of the amplitude control loop are defined as , Correspondingly, the PI parameters of the phase control loop are defined as .

[0070] Two-dimensional parameter scanning is widely used internationally to achieve and Parameter setting, such as Figure 2 (a) In the actual LLRF system, the PI parameters need to be optimized. When the PI parameters are too small, the loop cannot fully suppress the interference signal, resulting in a large steady-state error of the cavity pressure, such as Figure 2 (b) shows that it also cannot provide a sufficiently large loop bandwidth, reducing the dynamic performance of the low-level loop. However, when the P parameter and the I parameter are too large, the loop gain of the system may exceed the critical gain, and eventually cause the loop oscillation to become unstable, such as Figure 2 In addition, when the P parameter is too small and the I parameter is too large, it may cause zero-pole mismatch in the closed-loop system, and eventually induce loop oscillation, as shown in Figure 2 (a) is shown in the upper left corner. In order to avoid loop instability during parameter scanning and cause measurement interruption, the PI parameter grid is usually scanned in a relatively conservative rectangular area. In some cases, this area cannot completely cover the global optimal PI parameters. Figure 2 (b) In accordance with Figure 2 The measured results of parameter scanning in the rectangular area in (a). Figure 2 (a) The PI combination in the upper left corner has caused the cavity field to oscillate. The cavity pressure phase waveform corresponding to the black dot in the upper left corner is as follows: Figure 2 (c) If the range of the rectangular area is further expanded, it may directly lead to the collapse of the low-level loop.

[0071] In view of the above problems, this embodiment proposes a new PI parameter scanning method, which can obtain the global optimal PI parameter combination while avoiding cavity pressure oscillation. Do the following conversion:

[0072]

[0073] in, is the transfer function The zero point.

[0074] It should be noted that the present invention designs two loops with a total of 4 PI parameters, all of which are named K xy The first small subscript " x " takes the value "a" or "p", representing the amplitude control loop and the phase control loop respectively. The second subscript " y" takes the value "p" or "i", which respectively represents the proportional gain and integral gain in the PI parameters, as shown in Table 1 below:

[0075] Table 1 PI parameters

[0076]

[0077] Because the PI parameters of the amplitude and phase control loop in the present invention are and If there is no special explanation in the following text, it will be used uniformly. Represents the PI parameters of the above two loops, and no special distinction is made. In order to achieve a reasonable zero-pole configuration, The value of cannot be too large. Then, by scanning the parameters and , and find the optimal and Parameter combination to achieve and Parameter setting. Figure 3 As shown, in and On the two-dimensional scan map with coordinates, and The two-dimensional parameter grid is no longer a rectangle, but a right triangle. The maximum value of (i.e. the slope corresponding to the hypotenuse of the right triangle), that is, the unstable area can be bypassed to obtain the global optimum and combination.

[0078] Based on the above principles, the method for online global optimization of RF low-level system feedback control parameters provided in this embodiment includes:

[0079] S1. Generation and The scan grid.

[0080] In this embodiment, the generated and The scanning grid should first determine the parameters and The boundary values ​​of , i.e., the maximum and minimum values. Among them, the scanning parameters The maximum value of can be determined experimentally, and the process is as follows: Set to 0 and gradually increase Parameters until the feedback loop oscillates due to excessive gain. The value is recorded as , you can set the maximum value for scanning the network value 0.7~0.8 times ,For example For a superconducting radio frequency cavity, the minimum value( K p1 ) should generally be less than 1 / 50 of. For example: K p , max =200, then K pn Optional is 150, K p1 Can be selected as 2. Scan Parameters r The maximum value of r m Can be set to cavity half bandwidth ω 0.5 30~100 times of . r Minimum value of r 1 can be set to ω 0.5 1 / 10~1 / 2 of For example, if the half bandwidth of the cavity is ω 0.5 is 1000 radians per second (corresponding to about 160 Hz), then r m The option is 100000; r 1 can be selected as 100, as an example, but not limited to this. After determining the boundary value ( K p1 , K pn )and( r 1, r m ), the parameter set can be determined according to the geometric principle. For example, if K p1 =2, K pn =256, then scan parameter set [ K p1 , K p2 ,… K pn ] can be selected as [2,4, …,256]. The scanning parameter set [ r 1, r 2,… r m The selection principle of ] is the same as that of , so it will not be repeated here. indivual Parameter sets and parameter sets and indivual Parameter Set , the generated parameter sweep mesh is:

[0081] .

[0082] Among them, the parameter pair on the lower left Corresponding parameter pairs The minimum value of Corresponding parameter pairs The maximum value of .

[0083] S2, use the "S" type path to scan the above parameters to generate PI parameter combinations.

[0084] It should be noted that the traditional method generally directly uses the integral gain With proportional gain As the scanning parameter to construct the scanning network, this embodiment uses the integral gain as well as and Ratio As scanning parameters. The traditional "N" scanning path is as follows Figure 4 As shown in (a), the process is as follows: From the minimum parameter pair in the lower left corner ( K p1 , r 1) Start scanning and keep the proportional gain first K p Unchanged, scan parameters from small to large r ; When the parameter r Scan to maximum value r m When , the scanning parameter pair is ( K p1 , r m ), the next scan parameter pair is ( K p2 , r 1). It can be seen that the parameters r m and r 1 has a large difference in value ( r m >200 r 1). In a closed-loop control system, a sudden change in control parameters by a large multiple may cause transient instability in the system. To avoid the above problem, this embodiment adopts the following Figure 4 (b) shows the “S”-shaped scanning path. The scanning process is as follows: As with the traditional method, the minimum parameter pair ( K p1 , r1) Start scanning. Keep the proportional gain K p Unchanged, scan parameters from small to large r ; When the parameter r Scan to maximum value r m When , the scanning parameter pair is ( K p1 , r m ), the next scan parameter pair is ( K p2 , r m ), it can be seen that the parameter K p1 and K p2 The value difference is small (for example: K p2 =K p1 The “S” type scanning path effectively avoids the instantaneous instability of the system caused by the sudden change of closed-loop parameters. Figure 4 As shown in (b), according to the "S"-shaped path, the PI parameters are configured using a python script to generate The PI parameter combinations are:

[0085] .

[0086] S3. Online acquisition of the cavity pressure signal of the RF cavity under each set of PI parameters.

[0087] In this embodiment, for each group Parameters, first convert them into The parameters are then input into the LLRF system using the EPCIS (Experimental Physics and Industrial Control System) commonly used in the accelerator field, and the cavity sampling signal is obtained through the RF low-level system based on online measurement. P t , cavity incident signal and reflected signal Then the cavity pressure of the RF cavity is obtained and forward voltage and reverse voltage For each group Parameter combination, record several groups of cavity signals, for example, 5 to 20 groups of cavity signals, including: cavity pressure, cavity incident and reflected signals, etc.

[0088] Furthermore, the low-level system measures the cavity sampling signal online , cavity incident and reflected signals and Signal, where , and The signals correspond to the cavity pressure of the superconducting cavity , forward and reverse voltage and The voltage involved in the present invention (such as , and etc.) are all in complex form, and they are expressed in the form of amplitude and phase, for example: V =| V | e j∠V , where | V | is the amplitude, ∠ V For phase.

[0089] S4. Read the cavity pressure signal under each set of PI parameters and calculate the rms mean.

[0090] In this embodiment, different The stability of the cavity pressure signal under the combination. Cavity pressure signal V c is a complex number and can be expressed as V c =| V c | e j∠Vc , therefore, the stability here includes the amplitude | V c |Stability and phase ∠ V c This embodiment uses the Root Mean Square Radius (RMS radius) as the stability evaluation index.

[0091] For a single measurement, the amplitude stability index and phase stability index are calculated as follows:

[0092]

[0093] A single measurement result may be affected by random noise and interference. Combination, multiple measurements should be performed and the average should be calculated. Taking the measurement of amplitude stability index as an example, this embodiment performs 7 measurements in total, and the rms value is calculated using the above formula for each measurement. The results of these 7 times are stored in the array [ a 1, a 2,… a 7], name this array V c_rms In the array V c_rms In the above example, we need to set the maximum value max(V c_rms ) and minimum value min( V c_rms ) is removed to eliminate the influence of occasional factors (such as impulse noise). Assume that max( V c_rms ) and min( V c_rms ) respectively correspond to a 2 and a 5. Remove a 2 and a The new array after 5 V′ c_rms =[ a 1, a 3, a 4, a 6, a 7], the new array is averaged to obtain the final amplitude stability index. According to the above process, the superconducting cavity pressure amplitude is calculated | V c The algorithm for the rms mean of | is as follows:

[0094]

[0095] It should be noted that the superconducting cavity phase ∠ V c Stability index calculation method and cavity pressure amplitude | V c The calculation method of | is exactly the same and will not be repeated here.

[0096] S5. Create a contour map based on the calculated rms cavity pressure to obtain the best PI parameter combination.

[0097] In this embodiment, a two-dimensional contour map is obtained based on the calculation of the rms radius of the amplitude and phase of the cavity pressure under different sets of PI parameters, and its horizontal and vertical coordinates are respectively and Parameters, the data on the contour line is the rms radius of the cavity pressure signal.

[0098] like Figure 7 As shown in (a), the values ​​on the contour lines are the calculated rms values ​​(e.g. 0.0282% and 0.04°). In the contour map, find the closed curve with the smallest rms value, and its center is the optimal parameter. Figure 7 In (a), the closed curve with the smallest cavity pressure amplitude rms value is 0.0282%, and the closed curve with the smallest cavity pressure phase rms value is 0.04°. The center positions of the two groups of closed curves are marked with black squares. The parameters are: (13, 10000) and (17, 20000).

[0099] like Figure 7 As shown in (b) on the left and 7 (c) on the right, when there are multiple closed curves with equal rms values, the one that should be selected first is Smaller closed curve.

[0100] The application of the method for online global optimization of feedback control parameters of a radio frequency low-level system of the present invention is described in detail below through specific embodiments.

[0101] The superconducting cavity used in this embodiment is a half-wavelength superconducting cavity (HWR010, whose relativistic speed is 0.1). The resonant frequency of the cavity is 162.5 MHz, and the loaded quality factor is ( ) is approximately The online data acquisition system used in this embodiment is as follows: Figure 5 As shown, it includes a digital low-level system 1, a solid-state power source 2, a directional coupler 3, an input coupler 4, a radio frequency cavity 5, a signal extraction coupler 6 and a host computer 7. The output end of the digital low-level system 1 is connected to the input end of the solid-state power source 2, the output end of the solid-state power source 2 is connected to the input end of the directional coupler 3, the output end (through port) of the directional coupler 3 is fed into the radio frequency cavity 5 through the input coupler 4, and the directional coupler 3 is used to extract the cavity incident signal of the radio frequency cavity 5 P f and cavity reflection signal P r The signal extraction coupler 6 is connected to the RF cavity 5 to extract the cavity sampling signal. The cavity incident signal, cavity reflection signal and cavity sampling signal are sent to the digital low-level system 1 after down-conversion. The digital low-level system 1 is based on the cavity incident signal P f , cavity reflection signal P r and cavity sampling signal P t Demodulate the corresponding cavity pressure , forward voltage and reverse voltage and uploaded to the host computer 7 via the data bus.

[0102] Based on the above system, Figure 6 As shown, the method for online global optimization of the feedback control parameters of the RF low-level system of this embodiment has the following specific process:

[0103] 1. Generate and Parameter sweep mesh of .

[0104] In this embodiment, the indivual parameter: and indivual parameter: , generate a parameter sweep mesh:

[0105] .

[0106] in, The selection can be a linear arithmetic sequence or a nonlinear sequence (such as a geometric sequence). In general, due to the response of the system The small changes are not sensitive enough, usually you can choose is a geometric progression. .

[0107] use Figure 4 The S-shaped scanning method shown in (b) scans the parameters point by point, generating indivual Parameter combination:

[0108] .

[0109] Scanning Phase PI parameters When maintaining the PI parameters of the amplitude The preset position remains unchanged. The preset value of can usually be selected as the critical value , The preset value of can usually be selected as 1 to 10 times the cavity half bandwidth (e.g. K ai =5 ω 0.5 After completing the phase control loop PI parameter scan, a set of optimal For example, after scanning the superconducting cavity CM 2-4 After the phase control loop, Figure 7 (a) Right, we can get the optimal Parameters (17, 20000). Among them, , then the optimal PI parameters of the phase control loop ( K pp , K pi ) is (17, 340000). Set the PI parameters of the phase control loop to the above optimal parameters remain unchanged (i.e., the PI parameters are set to K pp =17, K pi=340000), the sweep amplitude control loop Parameters, such as Figure 7 (a) As shown on the left, the optimal ( ) is (13, 10000), where r a = K ai / K ap , then the optimal PI parameters of the phase control loop ( K ap , K ai ) is (13, 130000). The PI parameter tuning method of amplitude and phase is equivalent to scanning the two PI control loops of phase and amplitude in sequence.

[0110] 2. Measuring the cavity pressure of a superconducting cavity , forward and reverse voltage and .

[0111] In this embodiment, for each group Parameters, first convert them into Parameters are then entered into the LLRF system using EPCIS and Figure 5 The experimental block diagram shown in the figure collects cavity pressure data: uses the signal extraction coupler 6 to measure the cavity sampling signal of the superconducting cavity online ; Use directional coupler 3 to measure the cavity incident signal and reflected signal online and ,in, , and All of them are 162.5 MHz RF signals. After the above RF signals are down-converted and digitized in turn, the digital low-level system 1 obtains the original digitized baseband voltage signal, i.e., the cavity pressure , forward voltage and reverse voltage The above signals are all complex numbers expressed in the form of amplitude and phase, for example: V =| V | e j∠V , where | V | is the amplitude, ∠ V For phase.

[0112] In order to eliminate the influence of random errors, for each group Parameters, a total of 5 to 20 sets of cavity pressure data are measured and recorded (7 sets are selected in this embodiment), the sampling rate is 0.01 MHz, a total of 10,000 points, and the corresponding waveform data duration is 1 second. For each cavity, first scan according to the scanning method mentioned in step 1. Phase Parameter grid, measure and store different Under the parameter combination , and Signal.

[0113] 3. Calculate each group Under the combination of parameters, the phase and amplitude of cavity pressure rms radius, and draw a two-dimensional contour map to find the optimal PI parameters.

[0114] In this embodiment, according to the cavity pressure measured in step 2 Signal, the following indicators are used to describe its stability:

[0115]

[0116] in, , and Respectively represent The amplitude and phase of and represent the mean of amplitude and phase respectively, and The smaller it is, the more stable the cavity pressure is.

[0117] In the scanning range Parameters, for each group The following 5~20 sets of measurement data are first calculated according to the above formula The mean value after removing the maximum and minimum values ​​is then used as an indicator to measure this group The stability of the cavity pressure amplitude under the parameters. Similarly, Parameters, As an indicator for sorting, the maximum and minimum values ​​will be removed. The mean is used to measure the The stability of the cavity pressure phase under the parameters is determined, thereby completing the parameter setting of the two PI control loops of cavity pressure amplitude and phase.

[0118] PI parameter scanning results: Based on the above scanning method, a PI parameter tuning experiment was carried out on a half-wavelength HWR superconducting cavity. Figure 7 These are the experimental results on different cavities. For each cavity, the proposed method can find the globally optimal PI parameters. Figure 7(b) Right and Figure 2 (b) is the PI parameter scanning process of the cavity pressure phase of the same cavity (CM2-5). Figure 7 As shown, the method proposed by the present invention can be used to avoid Figure 2 (b) While scanning the oscillation region in the upper left corner, a larger parameter range is scanned to determine the globally optimal PI parameter combination, thereby improving the operating stability of the cavity and the longitudinal indicators of the beam.

[0119] Embodiment 2: The above-mentioned embodiment 1 provides a method for online global optimization of RF low-level system feedback control parameters. Correspondingly, this embodiment provides a device for online global optimization of RF low-level system feedback control parameters. The device provided in this embodiment can implement the method for online global optimization of RF low-level system feedback control parameters of embodiment 1, and the device can be implemented by software, hardware, or a combination of software and hardware. For the convenience of description, the present embodiment is described separately by functions divided into various units. Of course, the functions of each unit can be implemented in the same or more software and / or hardware during implementation. For example, the device may include integrated or separate functional modules or functional units to perform the corresponding steps in each method of embodiment 1. Since the device of this embodiment is basically similar to the method embodiment, the description process of this embodiment is relatively simple. For relevant parts, please refer to the partial description of embodiment 1. The embodiment of the device for online global optimization of RF low-level system feedback control parameters provided by the present invention is only schematic.

[0120] Specifically, the present invention also provides a device for online global optimization of RF low-level system feedback control parameters, the device comprising:

[0121] A parameter generation unit configured to generate parameters and parameters The parameter sweep grid is is the proportional gain, is the integral gain;

[0122] A scanning unit is configured to scan a parameter scanning grid using an "S"-shaped path to obtain a plurality of PI parameter combinations;

[0123] A cavity pressure acquisition unit is configured to acquire a cavity pressure signal of the radio frequency cavity under each set of PI parameters;

[0124] an rms calculation unit, configured to calculate an rms mean value of the cavity pressure based on the cavity pressure signal under each set of PI parameters;

[0125] The control parameter acquisition unit is configured to make a contour map based on the rms mean value of the cavity pressure, and acquire the best PI parameter combination based on the contour map.

[0126] Embodiment 3: This embodiment provides an electronic device corresponding to the method for online global optimization of RF low-level system feedback control parameters provided in this embodiment 1. The electronic device may be an electronic device for a client, such as a mobile phone, a laptop computer, a tablet computer, a desktop computer, etc., to execute the method of embodiment 1.

[0127] like Figure 8 As shown, the electronic device includes a processor, a memory, a communication interface and a bus, and the processor, the memory and the communication interface are connected through the bus to complete mutual communication. The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component (PCI) bus or an Extended Industry Standard Component (EISA) bus, etc. The memory stores a computer program that can be run on the processor. When the processor runs the computer program, it executes the method of Embodiment 1. The implementation principle and technical effect are similar to those of Embodiment 1 and will not be repeated here. Those skilled in the art can understand that Figure 8 The structure shown in the figure is only a block diagram of a part of the structure related to the scheme of the present application, and does not constitute a limitation on the computing device to which the scheme of the present application is applied. The specific computing device may include more or fewer components than shown in the figure, or combine certain components, or have a different arrangement of components.

[0128] In a preferred embodiment, the logic instructions in the above-mentioned memory can be implemented in the form of a software functional unit and can be stored in a computer-readable storage medium when it is sold or used as an independent product. Based on this understanding, the technical solution of the present application can be essentially or partly embodied in the form of a software product that contributes to the prior art. The computer software product is stored in a storage medium, including several instructions to enable a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), optical disk and other media that can store program codes.

[0129] In a preferred embodiment, the processor may be a central processing unit (CPU), a digital signal processor (DSP) or other general-purpose processors of various types, which are not limited herein.

[0130] Embodiment 4: This embodiment provides a computer-readable storage medium storing one or more programs, wherein the one or more programs include computer instructions. When the computer instructions are executed by a computer, the computer executes the method provided in the above-mentioned embodiment 1.

[0131] Embodiment 5: This embodiment provides a computer program product. The computer program product may include a computer program stored on a computer-readable storage medium. The computer program includes program instructions. When the program instructions are executed by a computer, the computer can execute the method provided in the above-mentioned embodiment 1. Its implementation principle and technical effects are similar to those of embodiment 1 and will not be repeated here.

[0132] In a preferred embodiment, the computer-readable storage medium may be a tangible device that holds and stores instructions used by the instruction execution device, such as but not limited to an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any combination thereof. The computer-readable storage medium stores computer program instructions that cause the computer to execute the method provided in the first embodiment.

[0133] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (apparatus), and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0134] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0135] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0136] Each embodiment in this specification is described in a progressive manner, and the same and similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In the description of this specification, the description of reference terms "a preferred embodiment", "further", "specifically", "in the present embodiment", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of this specification. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples without contradiction.

[0137] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for online global optimization of feedback control parameters of a radio frequency low-level system, characterized in that: include: Generate Parameters and parameters The parameter sweep grid is is the proportional gain, = / , is the integral gain; Use the "S" path to scan the parameter scanning grid to obtain several PI parameter combinations. The specific process is: from the minimum parameter pair in the lower left corner of the parameter scanning grid ( K p1 , r 1) Start scanning and keep the proportional gain first K p1 Unchanged, scan parameters from small to large r ; When the parameter r Scan to maximum value r m When , the scanning parameter pair is ( K p1 , r m ), the next scan parameter pair is ( K p2 , r m ), and then proceed in sequence to complete the "S" type scanning path, generating PI parameter combinations, specifically: ; Collect the cavity pressure signal of the RF cavity under each set of PI parameters; Based on the cavity pressure signal of each set of PI parameters, the rms mean of the cavity pressure is calculated; A contour map is made based on the rms mean of the cavity pressure, and the best PI parameter combination is obtained based on the contour map. The specific process is: a two-dimensional contour map is obtained based on the rms mean of the amplitude and phase of the cavity pressure under different PI parameter combinations, and its horizontal and vertical coordinates are parameters and parameters r , the data on the contour line is the rms radius of the cavity pressure signal; find the closed curve with the smallest rms value in the contour map, and its center position is the optimal PI parameter , when there are multiple closed curves with equal rms values, select Smaller closed curve.

2. The method for online global optimization of RF low-level system feedback control parameters according to claim 1, characterized in that: Generate Parameters and parameters The parameter scanning grid includes: determining the parameters K p With parameters r The boundary value of Based on the determined boundary values, the indivual Parameter Set and indivual Parameter Set , and obtain the parameter sweep grid.

3. The method for online global optimization of RF low-level system feedback control parameters according to claim 2, characterized in that: The parameter sweep mesh is: 。 4. The method for online global optimization of RF low-level system feedback control parameters according to claim 3, characterized in that: Determine the parameters K p With parameters r The process of the boundary value is: parameter K p The process of determining the boundary value is as follows: r Set to 0 and gradually increase K p Until the feedback loop oscillates due to excessive gain, K p The value is recorded as K p , max , set the maximum value of the scan grid K pn 0.7~0.8 times K p , max ; Minimum K p1 Should be less than K p, max 1 / 50 of parameter r The process of determining the boundary value is as follows: r The maximum value of r m Set as cavity half bandwidth ω 0.5 30 to 100 times of r Minimum value of r 1Set to ω 0.5 1 / 10~1 / 2 of.

5. The method for online global optimization of RF low-level system feedback control parameters according to claim 4, characterized in that: Based on the cavity pressure signal under each set of PI parameters, the rms mean of the cavity pressure is calculated. The specific process is: The collected cavity pressure signal V c Use plural representation V c =| V c | e j∠Vc , where | V c | is the amplitude, ∠ V c is the phase; For a single measurement, the amplitude stability index and phase stability index are calculated as follows: ； in, n is the total number of collections, For the i The measured cavity pressure amplitude, For the i The cavity pressure phase measured at this time is and represent the mean of amplitude and phase respectively, and The smaller it is, the more stable the cavity pressure is; For each set of PI parameters, multiple measurements were performed and the average was calculated to obtain the rms mean of the cavity pressure.

6. A device for online global optimization of feedback control parameters of a radio frequency low-level system, characterized in that: The device includes: A parameter generation unit configured to generate parameters and parameters The parameter sweep grid is is the proportional gain, = / , is the integral gain; The scanning unit is configured to use an "S"-shaped path to scan the parameter scanning grid to obtain a number of PI parameter combinations. The specific process is: from the minimum parameter pair ( K p1 , r 1) Start scanning and keep the proportional gain first K p1 Unchanged, scan parameters from small to large r ; When the parameter r Scan to maximum value r m When , the scanning parameter pair is ( K p1 , r m ), the next scan parameter pair is ( K p2 , r m ), and then proceed in sequence to complete the "S" type scanning path, generating PI parameter combinations, specifically: ; A cavity pressure acquisition unit is configured to acquire a cavity pressure signal of the radio frequency cavity under each set of PI parameters; an rms calculation unit, configured to calculate an rms mean value of the cavity pressure based on the cavity pressure signal under each set of PI parameters; The control parameter acquisition unit is configured to make a contour map based on the rms mean value of the cavity pressure, and obtain the best PI parameter combination based on the contour map. The specific process is: based on the rms mean value of the amplitude and phase of the cavity pressure under different PI parameter combinations, a two-dimensional contour map is obtained, and its horizontal and vertical coordinates are parameters and parameters r , the data on the contour line is the rms radius of the cavity pressure signal; find the closed curve with the smallest rms value in the contour map, and its center position is the optimal PI parameter , when there are multiple closed curves with equal rms values, select Smaller closed curve.

7. An electronic device, characterized in that: include: at least one processor; as well as A memory communicatively connected to the processor; wherein, The memory stores instructions executable by the processor, and the instructions are executed by the processor to enable the processor to perform the method according to any one of claims 1 to 5.

8. A computer-readable storage medium storing one or more programs, characterized in that: The one or more programs include computer instructions for causing a computer to execute the method according to any one of claims 1-5.

Images