CN104881394B - Single-mode system harmonic balance subtraction unit - Google Patents

Single-mode system harmonic balance subtraction unit Download PDF

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CN104881394B
CN104881394B CN201510295236.7A CN201510295236A CN104881394B CN 104881394 B CN104881394 B CN 104881394B CN 201510295236 A CN201510295236 A CN 201510295236A CN 104881394 B CN104881394 B CN 104881394B
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harmonic
amplitude
phase
average
subharmonic
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CN104881394A (en
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陈国强
王耿
康件丽
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Henan University of Technology
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Henan University of Technology
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Abstract

The invention discloses a kind of single-mode system harmonic balance subtraction unit, belong to computer engineering application field.The device includes nonlinear system arrangement components, symbolic variable definition component, calculating unit, output block.An objective function unit, the object function needed during for dynamic construction Optimization Solution average, the amplitude of each harmonic and phase are provided with calculating unit.The harmonic wave equilibrium method that the device is used, only considers the limited subharmonic in response, is classified as low-order harmonic part and high-frequency harmonic part.Optimization, iteration improve solving precision since low frequency part only includes average with first harmonic, it is continuously increased the number of times for the highest subharmonic that low frequency part is included, reduce the minimum subharmonic of high-frequency harmonic part simultaneously, obtained result is calculated as initial value using low-order harmonic part, average, the amplitude and phase of limited subharmonic in response is finally solved.The device that the present invention is provided has convergence rate and very high precision quickly.

Description

Single-mode system harmonic balance subtraction unit
Technical field
The invention belongs to computer engineering application field, in particular to a kind of single-mode system harmonic wave equilibrium method Device.
Background technology
Harmonic wave equilibrium method is a kind of very effective method for handling nonlinear system problem.Many actual control systems All meet should be in this way condition, therefore obtain a wide range of applications, such as gear drive, shake in field of engineering technology The analysis and design of the machines such as dynamic conveyer, vibration cooling machine, vibrating mill, engine, motor turning, electronic circuit and system In.Wherein single-degree-of-freedom nonlinear system is most commonly seen, is also Nonlinear System with Multi degree of Freedom research and the basis of application, obtains Domestic and international experts and scholars, the extensive concern of engineers and technicians, and put into substantial amounts of research.Basis and use that it is applied Processing method be:Output/response is expressed as to the form of Fourier space, limited subharmonic is only considered, passes through mathematical method The amplitude and phase of harmonic wave are solved, so as to obtain the frequency domain characteristic of system.In nonlinear system equation substitute into input/excitation with The Fourier space of output/response, compares both sides coefficient to set up equation group, and then solve the amplitude and phase of harmonic wave;But When nonlinear system becomes complexity, it is impossible to obtain explicit equation group, the method will be faced with many applications above it is difficult.Directly Scoop out with Fast Fourier Transform (FFT) (FFT), using the extremely complex nonlinear system of numerical method analysis, then with very strong logical The property used.But when the harmonic wave item number to be analyzed is many in the harmonic wave item number or response that system input/excitation is included, and in view of being The subharmonic and ultraharmonics of system output, then be related to harmonic amplitude and a large amount of unknown numbers to be solved such as phase, have impact on the effect of analysis Rate and precision, implement extremely complex, low precision, and the calculating time sharply increases, or even can not effectively analyze.
The content of the invention
Realize that complicated, analysis harmonic wave item number is few, time-consuming and precision is low during for harmonic Balance Analysis nonlinear system Problem, it is an object of the invention to provide a kind of single-degree-of-freedom nonlinear system harmonic balance subtraction unit, to solve the above problems.
The object of the present invention is achieved like this:A kind of single-mode system harmonic balance subtraction unit, using a kind of harmonic wave Balancing method, it considers the limited subharmonic in response when solving the response of single-degree-of-freedom nonlinear system, only, will be described limited Subharmonic is divided into low-frequency harmonics part and high-frequency harmonic part, and only include average from the low-frequency harmonics part opens with first harmonic Begin, by Optimization Method average, the harmonic amplitude of the low-frequency harmonics part and phase, estimate the high-frequency harmonic part Harmonic amplitude and phase, and precision is improved by iteration, is continuously increased the most high order that the low-frequency harmonics part includes humorous The number of times of ripple, increase by one every time, while removing the minimum subharmonic of high-frequency harmonic part, in terms of the low-frequency harmonics part Obtained result finally solves average, the amplitude and phase of the limited subharmonic in response as initial value,
The single-mode system harmonic balance subtraction unit is included with lower component:
Nonlinear system arrangement components, expression formula and excitation for defining nonlinear system,
Symbolic variable definition component, for define average in response of nonlinear system, the amplitude of the limited subharmonic with The symbolic variable of phase,
Calculating unit, for by the harmonic wave equilibrium method calculate response in average, the amplitude of the limited subharmonic with Phase, output block, for storing result that the calculating unit obtains, result being shown in the way of image conversion,
The calculating unit includes:Computing module preparation module, computing module main body module, computing module post processing mould Block, wherein, the computing module preparation module, for set the initial value of iteration, in a primitive period time dispersion number Mesh, the computing module main body module, for calculating average, the amplitude of the limited subharmonic in response by the method for iteration With phase, and evaluating, the computing module main body module is made up of two layers of circulation, and outer loop controls the low frequency humorous The number of times of ripple part highest subharmonic, interior loop by Optimization Method respond described in average in low-frequency harmonics part, The amplitude and phase of each harmonic;
An objective function unit is provided with the computing module main body module, is solved for constitution optimization described Object function in low-frequency harmonics part when average, the amplitude of each harmonic and phase, in an iterative process, object function The number of average, the amplitude of each harmonic and phase is in dynamic change in expression formula form, the low-frequency harmonics part to be optimized Change, the objective function unit is exactly to be used for constructing this object function.
Further, applicable single-degree-of-freedom nonlinear system is expressed as equation
In formula, t is the time;Y (t) is the response of system, that is, is exported;Single order, the second order respectively responded Derivative;For onWithFunction;F (t) is excitation, that is, is inputted;
In the calculating unit, the method bag that average, the amplitude of the limited subharmonic and phase are used in response is solved Include following steps:
S1:The cyclic variable k of the highest subharmonic number of times of the low-frequency harmonics part, interior loop variable i is represented to put just Value:Put initial value in k=1, i=1, the high-frequency harmonic part:yHF(t)=0, the initial value X0 of Optimization Solution is set;
S2:Optimization method calculates average, the amplitude of each harmonic and phase in the low-frequency harmonics part, including:
S21:Calculate the low-frequency harmonics part yLF(t) expression formula
In formula, A0/ 2 be average, AnWithThe respectively amplitude and phase of n-th harmonic, k is the low-frequency harmonics portion The number of times of highest subharmonic in point;Ω1For the angular frequency of the angular frequency of fundamental wave, i.e. first harmonic,
S22:Calculate the response y (t) of nonlinear system expression formula (6)
Y (t)=yLF(t)+yHF(t) (6)
S23:Seek error in equation sequence e (tm) character expression, seek its FFT character expression
In formula, tmFor discrete time point, m=1,2,3 ..., N, N is the points of the error in equation series of discrete;
S24:Seek the expression formula of object function
S25:With formula (9) minimum optimization aim, obtain in the low-frequency harmonics part average, the amplitude of each harmonic with Phase A0, A1 A2,..., Ak,Value;
S26:By the amplitude A of each harmonic in the low-frequency harmonics part1, A2..., AkIt is converted into nonnegative value, phaseBe transformed into it is interval [0,2 π) on, method is:
S3:Iterative initial value, high-frequency harmonic part are updated, including:
S31:Calculate the error in equation sequence e (tm) numerical expression, accounting equation error mean square root erms
S32:Judge whether interior loop meets exit criteria:1. the error in equation root-mean-square value ermsIt is reduced to setting Precision, 2. the iterations i of interior loop reach the upper limit of setting,
If meeting any of which condition, turning S4 increases the number of times k of the low-frequency harmonics part highest subharmonic, continues Iteration,
If be all unsatisfactory for, turn S33;
S33:The high-frequency harmonic part is updated, the initial value X0 of nonlinear optimization is set, cyclic variable increases by 1, i=i+1, Turn S22 and continue iteration, wherein, use equation below and step:
S331:The concrete numerical value of calculating formula (11),
In formula, yLFFor yLF(t) shorthand, yHFFor yHF(t) shorthand,For yLF(t) first derivative,For yHF(t) first derivative;
S332:The amplitude and phase of the harmonic wave included with FFT calculating formulas (11), are translated into cosine function and sinusoidal letter The form of number sum, obtains amplitude anWith bn, seek the expression formula (12) of the estimate of the high-frequency harmonic part
S4:Judge whether the cyclic variable k for representing the highest subharmonic number of times of the low-frequency harmonics part is not more than to set Upper limit number of times, or not up to precision conditions,
If it is, the initial value X0 of the nonlinear optimization is set, cyclic variable k increases by 1:K=k+1, goes to step S2;
Otherwise, calculating terminates.
Further, in step S4, upper limit number of times is not more than the points N of error in equation series of discrete described in step S2 Half N/2.
Further, in step S4, precision conditions are that outer loop previous cycle, i.e. kth wheel are circulated, with last round of circulation The obtained error in equation root-mean-square value it is equal or difference be less than setting the limits of error.
In some embodiments, in step S3, the initial value X0 of nonlinear optimization method to set up is:Interior loop In this i wheel circulations from 1 to i, when ith is circulated, by optimizing obtained average, harmonic amplitude and phase in step S2,
In step S4, the initial value X0 of the nonlinear optimization includes 2k+3 element, is this k wheel of the outer loop from 1 to k In circulation, under kth time circulation, in corresponding interior loop, when ith is circulated, the result obtained in step S2 and S3, wherein 2k + 1 element is by optimizing obtained average, harmonic amplitude and phase in step S2;Other 2 elements are FFT in step S3 Calculate the amplitude and phase of obtained corresponding harmonic wave.
In some embodiments, in step S3, the initial value X0 of nonlinear optimization method to set up is:Interior loop In this i wheel circulations from 1 to i, when ith is circulated, by optimizing obtained average, harmonic amplitude and phase in step S2,
In step S4, the initial value X0 of the nonlinear optimization includes 2k+3 element, is this k wheel of the outer loop from 1 to k In circulation, under kth time circulation, in this i wheel circulations of the corresponding interior loop from 1 to i, minimum error mean square root ermsIt is right The result answered, wherein 2k+1 element is by optimizing obtained average, harmonic amplitude and phase in step S2;Other 2 members Element calculates the amplitude and phase of obtained corresponding harmonic wave for FFT in step S3.
In some embodiments, step S33 detailed step is:Judge the error in equation root-mean-square value ermsWhether The value obtained less than last round of iteration, if it is not, then the initial value X0 of nonlinear optimization is added at random on the basis of original Disturbance, cyclic variable increase by 1:I=i+1, turns S2 and continues iteration;Otherwise, S331 and S332 is performed, iterative initial value X0 is set to step By optimizing obtained average, harmonic amplitude and phase in rapid S2, if the error in equation root-mean-square value ermsChanged with last round of The difference for the error mean square root that generation obtains is less than the limits of error of setting, then in X0 along with a random perturbation,
In step S4, the initial value X0 of the nonlinear optimization includes 2k+3 element, is this k wheel of the outer loop from 1 to k In circulation, under kth time circulation, in corresponding interior loop, when ith is circulated, the result obtained in step S2 and S3, wherein 2k + 1 element is by optimizing obtained average, harmonic amplitude and phase in step S2;Other 2 elements are FFT in step S3 Calculate the amplitude and phase of obtained corresponding harmonic wave.
Further, step S21~S24 symbolization computings, step S3 uses numerical operation.
Further, in the symbolic variable definition component, when being realized using perceptive construction on mathematics, represent equal The symbolic variable of value, amplitude and phase is made up of prefix with digital two parts, in Part I before average, amplitude symbolic variable Sew identical, the prefix of phase symbol variable is identical, Part II numeral is positive integer numeral, the determination method of digit is: If the highest overtone order of limited subharmonic described in response is M, then the minimum value of the digit of Part II numeral isIf digit not enough, is above supplied with numeral 0.
Yet further, the method that the objective function unit is used comprises the following steps:
a:Expression formula (4) is converted into character string myObjFunStr1 with char functions;
b:Then character string myObjFunStr1 average is replaced with into character string with character string replacement function strrep:x (1), amplitude replaces with character string:X (2), x (3) ..., x (k), x (k+1), phase replaces with character string:x(k+2)、x(k+ 3) ..., x (2k), x (2k+1), obtain representing the character string type expression formula myObjFunStr2 of object function;
c:Before character string myObjFunStr2 plus character string '@(x) ', obtain new character string myObjFunStr3;
d:Character string myObjFunStr3 is converted into object function with eval functions.
The present invention has significant advantage and beneficial effect compared with prior art:
(1) in the present invention, symbolization computing is combined with numerical operation, and computational accuracy is high, efficiency high.Symbolic operation Precision is ensure that, numerical operation improves operational efficiency, reduces the calculating time.
(2) the limited subharmonic considered in the response of nonlinear system is divided into low-frequency harmonics portion by the method that the present invention is used Point with high-frequency harmonic part, since low-frequency harmonics part only comprising average and first harmonic, only three are to be optimized unknown Amount, nonlinear optimization is simple and easy to apply;Gradually increase low-frequency harmonics part includes the item number of harmonic wave, and one high order of increase is humorous every time Ripple, introduces two unknown quantitys, and nonlinear optimization is from simple to complexity, it is ensured that optimization precision and efficiency.
(3) an objective function unit is provided with the device that the present invention is provided, makes non-linear objective function all the time Unknown quantity to be optimized is only included, i.e., there was only 2k+1 unknown quantity per suboptimization, the unknown quantity without redundancy improves optimization effect Rate, substantially reduce run time.
(4) in step S3, random perturbation is added when initial value X0 is set, it is to avoid repeat what is undergone during follow-up Optimized Iterative Calculating process, and add with randomization the speed of iteration convergence, can significantly improve the operational precision of device, reduce it is whole The number of times of body iteration.
(5) in step S4, when initial value X0 is set, FFT in step S3 is used for two newly-increased unknown quantitys to be optimized The amplitude and phase of obtained corresponding subharmonic are calculated, in the case of no prior information, the reasons why having abundant thinks it most Close to actual value, therefore the efficiency of next round nonlinear optimization can be improved, improve computational accuracy.
(6) symbolic variable Part II numeral positive integer digit groups as defined in digit of average, amplitude and phase are represented Into, and digit associates with the finite harmonic number of times to be considered, it is ensured that and it is readable, succinct that objective function unit is realized Property and convenience, using the present invention provide device when, it is only necessary to change highest overtone order be M value, conveniently make With.
Brief description of the drawings
The structure composition figure for the device that Fig. 1 provides for the present invention;
Fig. 2 is the schematic diagram for the harmonic wave equilibrium method that apparatus of the present invention are used;
Fig. 3 is the flow chart for the harmonic wave equilibrium method that apparatus of the present invention are used;
Fig. 4 is objective function element method figure;
Fig. 5 is the average and harmonic amplitude figure of the embodiment of the present invention 1;
Fig. 6 is the average and harmonic amplitude figure of the embodiment of the present invention 2;
Fig. 7 is the error in equation root-mean-square value of the embodiment of the present invention 3 with iterations variation diagram;
Fig. 8 is the average and harmonic amplitude figure of the embodiment of the present invention 3.
Embodiment
Below in conjunction with accompanying drawing and preferred embodiment, to the architectural feature provided according to the present invention, embodiment and its Effect, is described in detail as follows.
The invention provides a kind of single-mode system harmonic balance subtraction unit, structure is as shown in Figure 1.What this device was applicable Single-degree-of-freedom nonlinear system is represented by equation below
In formula, t is the time;Y (t) is the response of system, that is, is exported, convenient following for statement, and some ground places are omitted (t);The single order that respectively responds, second dervative;For onWithLetter Number;F (t) is excitation, that is, is inputted.
When solving the response of nonlinear system with harmonic wave equilibrium method, output/response is expressed as to the form of Fourier space, Only consider limited subharmonic, the number of times of highest subharmonic in response is set to a fixed value M.
Then output is expressed as
In formula, A0/ 2 be average, A1、A2、A3、…、AM-1、AMWithRespectively M humorous The amplitude and phase of ripple, Ω1For the angular frequency of fundamental wave.
If y is not accurate solution, just there is an error e (t) on equation (1) the equal sign left side and the right
Harmonic balance subtraction unit needs average, M harmonic amplitude, M harmonic phase in solution formula (2), altogether 2M+1 Individual unknown quantity.The single-mode system harmonic balance subtraction unit that the present invention is provided uses method as shown in Figure 2, will respond All harmonic waves in formula (2) are divided into the low-frequency harmonics part and the high-frequency harmonic part.The low-frequency harmonics part is included Harmonic wave item number, that is, highest subharmonic number of times, controlled with cyclic variable k.
The low-frequency harmonics are partially shown as
In formula, A0/ 2 be average;AnWithThe respectively amplitude and phase of n-th harmonic;K is the low-frequency harmonics part The number of times of middle highest subharmonic;Ω1For the angular frequency of the angular frequency of fundamental wave, i.e. first harmonic.
The low-frequency harmonics part described by formula (4) correspond to 1 average, k harmonic amplitude, k phase, so institute Low-frequency harmonics part is stated altogether comprising 2k+1 unknown quantity.
Then the high-frequency harmonic is partially shown as
The number of times for the minimum subharmonic that the higher hamonic wave part described by formula (5) is included is k+1, then the harmonic high frequency The harmonic wave item number that ripple part is included is M-k.This M-k harmonic wave corresponds to M-k amplitude and M-k phase, so the high frequency Harmonic includes altogether 2 (M-k) individual unknown quantitys.
During beginning, k=1, the low-frequency harmonics part only includes average and first harmonic, now there is average, first harmonic Amplitude and 3 unknown quantitys of phase, this 3 unknown quantitys are asked by nonlinear optimization, the initial value of optimization includes three elements, can be with Random generation is set according to the priori of nonlinear system.With the concrete numerical value of formula (3) accounting equation error, pass through FFT Calculating obtains the amplitude of the high-frequency harmonic part and the estimate of phase, altogether 2 (M-1) individual amount.According to the above results, repeatedly Iteration, improves average, the precision of 3 unknown quantitys of first harmonic amplitude and phase.
It is continuously increased the number of times for the highest subharmonic that the low-frequency harmonics part is included, the increase by 1 every time of k values.That is Low-frequency harmonics portions per increases by one, while removing the minimum subharmonic of the high-frequency harmonic part, i.e. k+1 subharmonic .Using outer loop as 1,2,3 ..., iteration result during k iterates, finally asked as the initial value of+1 iteration of kth Solve average in response, the amplitude and phase of M harmonic waves.
As shown in figure 1, the single-mode system harmonic balance subtraction unit is included with lower component:
Nonlinear system arrangement components, expression formula and excitation for defining nonlinear system,
Symbolic variable definition component, for define average in response of nonlinear system, the amplitude of the limited subharmonic with The symbolic variable of phase,
Calculating unit, for by the harmonic wave equilibrium method calculate response in average, the amplitude of the limited subharmonic with Phase, output block, for storing result that the calculating unit obtains, result being shown in the way of image conversion,
The calculating unit includes:Computing module preparation module, computing module main body module, computing module post processing mould Block,
Wherein, the computing module preparation module, for set the initial value of iteration, in a primitive period time from Dissipate number, the computing module main body module, for calculating average in response, the limited subharmonic by the method for iteration Amplitude and phase, and evaluating, the computing module main body module are made up of two layers of circulation, and outer loop control is described low The number of times of frequency harmonic highest subharmonic, interior loop by Optimization Method respond described in low-frequency harmonics part Value, the amplitude and phase of each subharmonic;
An objective function unit is provided with the computing module main body module, is solved for constitution optimization described Object function in low-frequency harmonics part when average, the amplitude of each harmonic and phase, in an iterative process, object function The number 2k+1 of average, the amplitude of each harmonic and phase is dynamic in expression formula form, the low-frequency harmonics part to be optimized State changes, and the objective function unit is exactly to be used for constructing this object function.
Specifically, the single-mode system harmonic balance subtraction unit that provides of the present invention mainly by two layers of circulation come Realize.The item number for the harmonic wave that the outer loop variable k controls low-frequency harmonics part is included;Internal memory cyclic variable i is controlled in k In the case of certain, the precision of average, the phase of harmonic wave and amplitude that the low-frequency harmonics part is included is improved by iteration, together When also improve the amplitude and the precision of phase estimation value of the harmonic wave that the high-frequency harmonic part is included.Specifically come institute, mainly include Following steps.
S1:The cyclic variable k of the highest subharmonic number of times of the low-frequency harmonics part, interior loop variable i is represented to put just Value:K=1, i=1, the high-frequency harmonic part yHF(t) initial value is put:yHF(t)=0, the initial value X0 of Optimization Solution is set, initially X0 can be generated at random, can also be determined according to the priori of non-thread system.
S2:Average, the amplitude of each harmonic and phase in the low-frequency harmonics part are calculated by optimization method, including:
S21:Calculate the low-frequency harmonics part yLF(t) expression formula (4);
S22:Calculate the response y (t) of nonlinear system expression formula (6);
Y (t)=yLF(t)+yHF(t) (6)
S23:And asked with formula (3) discrete type error in equation sequence e (tm)
e(tm)=yLF(tm)+yHF(tm) (7)
In formula, tmFor discrete time point, m=1,2,3 ..., N, N is the points of the error in equation series of discrete,
And seek error in equation sequence e (tm) Fast Fourier Transform (FFT) expression formula, and seek FFT expression formula
S24:Seek the expression formula of non-linear objective function
S25:With formula (9) minimum optimization aim, obtain in the low-frequency harmonics part average, the amplitude of each harmonic with Phase A0, A1,A2,..., Ak,Value;
S26:By the harmonic amplitude A in the low-frequency harmonics part1, A2..., AkIt is converted into nonnegative value, phaseBe transformed into it is interval [0,2 π) on, method is:
S3:Iterative initial value, high-frequency harmonic part are updated, including:
S31:Calculate the error in equation sequence e (tm), calculate its error mean square root erms
S32:Judge whether interior loop meets exit criteria:1. the error mean square root ermsIt is reduced under setting Limit, 2. iterations i reaches the upper limit of setting,
If meeting one of condition, turn the number of times k of S4 increase subharmonic, continue iteration,
If be all unsatisfactory for, turn S33;
S33:Update the high-frequency harmonic part, S35:The initial value X0 of nonlinear optimization, cyclic variable increase by 1 are set:I= I+1, turns S22 and continues iteration, wherein, use equation below and step:
S331:The value of calculating formula (11),
In formula, yLFFor yLF(t) shorthand, yHFFor yHF(t) shorthand,For yLF(t) first derivative,For yHF(t) first derivative;
S332:The amplitude and phase of the harmonic wave then included with FFT calculating formulas (11), are translated into cosine function and sine The form of function sum, obtains amplitude anWith bn, seek the expression formula of the estimate of high-frequency harmonic part
S4:Judge whether the cyclic variable k of the highest subharmonic number of times of low-frequency harmonics part described in table is not more than setting Upper limit number of times, or not up to precision conditions,
If it is, the initial value X0 of the nonlinear optimization is set,
Cyclic variable k increases by 1:K=k+1, goes to step S2;Otherwise, calculating terminates.
In step S4, upper limit number of times is not more than the half N/2 of the points N of error in equation series of discrete described in step S2.
With the increase of k values, the result precision more and more higher that the system with one degree of freedom harmonic balance subtraction unit is obtained.Work as k When increasing to a certain degree, the error mean square root erms keeps constant or reduction very slow, at this moment, it is believed that iteration is whole Only.
Step S3 and S4 are respectively that the next round of internal layer and outer loop is circularly set iterative initial value.As shown in Fig. 2 step X0 has 2k+1 element in S3, corresponding to average, the amplitude and phase of k low-order harmonics, is that the next round circulation of internal layer prepares Optimize initial value;X0 has 2k+3 element in step S4, is the next of outer layer corresponding to average, the amplitude and phase of k+1 harmonic waves Wheel circulation prepares optimization initial value.Outer loop increase by 1, it is meant that add a harmonic wave in the low-frequency harmonics part.Step S4 In 2 elements having more than the X0 in step S3 of X0 be the corresponding amplitude of this harmonic wave that the low-frequency harmonics part is increased newly With phase.For the setting of iterative initial value X0 in step S3 and S4, there are following 3 kinds technical sides that are all practical, working well Case.
Technical scheme 1:In step S3, the initial value X0 of nonlinear optimization method to set up is:Interior loop is from 1 to i This i wheel circulations in, when ith is circulated, by optimizing obtained average, harmonic amplitude and phase in step S2.
In step S4, the initial value X0 of the nonlinear optimization includes 2k+3 element, is this k wheel of the outer loop from 1 to k In circulation, under kth time circulation, in corresponding interior loop, when ith is circulated, the result obtained in step S2 and S3, wherein 2k + 1 element is by optimizing obtained average, harmonic amplitude and phase in step S2;Other 2 elements are FFT in step S3 Calculate the amplitude and phase of obtained corresponding harmonic wave.
Technical scheme 2:In step S3, the initial value X0 of nonlinear optimization method to set up is:Interior loop is from 1 to i This i wheel circulations in, when ith is circulated, by optimizing obtained average, harmonic amplitude and phase in step S2.
In step S4, the initial value X0 of the nonlinear optimization includes 2k+3 element, is this k wheel of the outer loop from 1 to k In circulation, under kth time circulation, in this i wheel circulations of the corresponding interior loop from 1 to i, minimum error mean square root ermsIt is right The result answered, wherein 2k+1 element is by optimizing obtained average, harmonic amplitude and phase in step S2;Other 2 members Element calculates the amplitude and phase of obtained corresponding harmonic wave for FFT in step S3.
Technical scheme 3:Step S33 detailed step is:Judge the error in equation root-mean-square value ermsWhether upper one is less than The value that wheel iteration is obtained, if it is not, then the initial value X0 of nonlinear optimization adds random perturbation, circulation on the basis of original Variable increase by 1:I=i+1, turns S2 and continues iteration;Otherwise, S331 and S332 is performed, iterative initial value X0 is set to lead in step S2 Average, harmonic amplitude and phase that optimization is obtained are crossed, if the error in equation root-mean-square value ermsObtained with last round of iteration The difference of error mean square root is less than the limits of error of setting, then in X0 along with a random perturbation, available random function is given birth at random Into.
In step S4, the initial value X0 of the nonlinear optimization includes 2k+3 element, is this k wheel of the outer loop from 1 to k In circulation, under kth time circulation, in corresponding interior loop, when ith is circulated, the result obtained in step S2 and S3, wherein 2k + 1 element is by optimizing obtained average, harmonic amplitude and phase in step S2;Other 2 elements are FFT in step S3 Calculate the amplitude and phase of obtained corresponding harmonic wave.
In step s 2, formula (8) is with all containing 2k+1 for unknown quantity to be asked in (9), and the form of these formulas in itself Change with nonlinear system equation (1), M and k change, and difference is huge;Therefore, in step S21~S24 using symbol Number computing, can make full use of the mathematical operation functions, pole such as powerful symbolic operation function, the derivation of engineering software or mathematical software The earth reduces the complexity of programming.Step S3 is to estimate the amplitude and phase of each harmonic of the high-frequency harmonic part Position, arithmetic speed can be greatly enhanced using numerical operation.
The single-mode system harmonic balance subtraction unit that the present invention is provided can be soft in many high-level programming languages, engineering Implement in part, mathematical software, such as MATLAB.During specific implementation, average, harmonic amplitude and phase in formula (2) have altogether 2M+1 amounts to be solved are, it is necessary to define corresponding variable to handle.In order to construct the convenience of object function, average, width are represented The symbolic variable of value and phase is made up of prefix with digital two parts.Average, the prefix of amplitude symbolic variable are identical, phase symbol The prefix of variable is identical;Part II numeral is positive integer numeral, and the determination method of digit is:If needing the response analyzed The number of times of middle highest harmonic wave is M, then the minimum value of the digit of Part II numeral isIf digit is not enough, It is then high-order to be supplied by numeral 0.
For example, average, the prefix of amplitude symbolic variable are An, the prefix of phase symbol variable is Phin.Work as M<When 100,Then the method for the symbolic variable defined in MATLAB is as follows:
If M=12, above method define 13 symbolic variable An01 for representing average and harmonic amplitude, An02, An03 ..., An11, An12, An13, also define 13 symbolic variable Phin01 for representing corresponding with above-mentioned amplitude phase, Phin02, Phin03 ..., Phin11, Phin12, Phin13, and also define two group numbers array An and Phin, all include 13 elements, the respectively symbolic variable of amplitude and phase.Because An01 is corresponding with average, symbolic variable Phin01 is to be The convenience of matching program, makes the amplitude of correspondence subharmonic with phase variant subscript consistent and definition, herein and without using.
Based on notation defined above variable, the method that the objective function unit is used comprises the following steps:
a:Expression formula (4) is converted into character string myObjFunStr1 with char functions;
b:Then character string myObjFunStr1 average is replaced with into character string with character string replacement function strrep:x (1), amplitude replaces with character string:X (2), x (3) ..., x (k), x (k+1), phase replaces with character string:x(k+2)、x(k+ 3) ..., x (2k), x (2k+1), obtain representing the character string type expression formula myObjFunStr2 of object function;
c:Before character string myObjFunStr2 plus character string '@(x) ', obtain new character string myObjFunStr3;
d:Character string myObjFunStr3 is converted into object function with eval functions.
Step b mainly uses strrep functions, and specific method is:
Represent average, amplitude and phase Part II numeral digit minimum value asA high position mend 0 be for Ensure to occur without wrong replacement during strrep functions are replaced.If not fixing digit, mistake occurs.Example Such as:If by variable-definition be An1, An2, An3 ..., An11, An12, An13, function strrep when A1 replaces with x (1), An10, An11, An12, An13 mistake can be substituted for x (1) 0, x (1) 1, x (1) 2, x (1) 3.
Implement the present invention in perceptive construction on mathematics.Illustrate beneficial effects of the present invention below with 3 embodiments.
Embodiment 1:The equation of single-degree-of-freedom nonlinear system is
Assuming that the angular frequency of first harmonic is 1 in response, iterative initial value X0=[0,0,0] is set, only considered less than 32 times Harmonic wave, i.e. M=32, the maximum times of interior loop are 5, sampling number N=64, and the limits of error is set to 1 × 10 in step S4-16, The scope of random perturbation is [- 5 × 10-5, 5 × 10-5].Implement technical scheme 3.With the increase of k values, the error in equation is equal Root value reduces rapidly, and error in equation mean-square value during preceding 6 circulations is followed successively by:
5.656854249492381e+000,2.496859179098087e-003,8.156122475628342e-008,
4.360844843951736e-012,4.360844843951736e-012,4.360844843951736e-012.
The amplitude of each harmonic is with phase as shown in figure 5, wherein 0 subharmonic corresponds to average, and 1~6 subharmonic is by step S2 nonlinear optimization is obtained, and 7~32 subharmonic are obtained by the numerical value FFT in step S3.
From above-mentioned data, it is apparent that working as k>After 4, iteration result tends to be constant, and precision grade is 10e-12, I.e. 10-12
Embodiment 2:Excitation in embodiment 1 is revised as cos2t, it is assumed that the angular frequency of first harmonic is 2 in response, if It is random generation, other specification be the same as Example 1 to put iterative initial value X0.Implement technical scheme 3.The amplitude and phase of each harmonic are such as Shown in Fig. 6, wherein 0 subharmonic correspondence average, 1~6 subharmonic obtains by step S2 nonlinear optimization, 7~32 subharmonic by Numerical value FFT in step S3 is obtained.Work as k>After 2, iteration result tends to be constant, and precision grade is 10-10
Embodiment 3:Excitation in embodiment 1 is revised as cos3t, it is assumed that the angular frequency of first harmonic is 3 in response, if Put iterative initial value X0 to generate to be random, only the harmonic wave of consideration less than 32 times, i.e. M=32, the maximum times of interior loop are 4, are adopted Number of samples N=64,.Implement technical scheme 3.With the increase of k values, the error in equation root-mean-square value reduces rapidly, such as Fig. 7 institutes Show, iteration result precision grade is 10-12.The amplitude of each harmonic is with phase as shown in figure 8, the corresponding average of wherein 0 subharmonic, 1 ~6 subharmonic are obtained by step S2 nonlinear optimization, and 7~32 subharmonic are obtained by the numerical value FFT in step S3.
The device that the present invention is provided only needs to change the number of times of the M i.e. controllable harmonic wave of value, using convenient.Above-mentioned 3 The result of embodiment, illustrates that the device of the invention provided has convergence rate and very high precision quickly.
If analyzing subharmonic, it is only necessary to set the frequency of first harmonic according to the angular frequency of subharmonic is wanted.
Object function can also be changed to the harmonic wave root-mean-square value of error in equation, good effect is equally can reach.
It should be noted that what above-mentioned specific embodiment was merely exemplary, under the above-mentioned teaching of the present invention, this area Technical staff can carry out various improvement and deformation on the basis of above-described embodiment, and these are improved or deformation all falls within this In the protection domain of invention.It will be understood by those skilled in the art that specific descriptions above are intended merely to explain the mesh of the present invention , it is not intended to limit the present invention.Protection scope of the present invention is limited by claim and its equivalent.

Claims (10)

1. a kind of single-mode system harmonic balance subtraction unit, it is characterised in that use a kind of harmonic wave equilibrium method, it is solving list During the response of free degree nonlinear system, only consider the limited subharmonic in response, the limited subharmonic is divided into low frequency humorous Ripple part and high-frequency harmonic part,
Only including average with first harmonic since the low-frequency harmonics part, pass through Optimization Method average, the low frequency The harmonic amplitude and phase of harmonic, estimate the harmonic amplitude and phase of the high-frequency harmonic part, and are carried by iteration High accuracy, is continuously increased the number of times for the highest subharmonic that the low-frequency harmonics part is included, every time increase by one, while removing height The minimum subharmonic of frequency harmonic, obtained result is calculated as initial value using the low-frequency harmonics part, final to solve Go out average, the amplitude and phase of the limited subharmonic in response,
The single-mode system harmonic balance subtraction unit is included with lower component:
Nonlinear system arrangement components, expression formula and excitation for defining nonlinear system,
Symbolic variable definition component, for defining average in response of nonlinear system, the amplitude and phase of the limited subharmonic Symbolic variable,
Calculating unit, for calculating average, the amplitude and phase of the limited subharmonic in response by the harmonic wave equilibrium method,
Output block, for storing result that the calculating unit obtains, result being shown in the way of image conversion,
The calculating unit includes:Computing module preparation module, computing module main body module, computing module post-processing module,
Wherein, the computing module preparation module, for set the initial value of iteration, in a primitive period time dispersion number Mesh,
The computing module main body module, average in responding, the width of the limited subharmonic are calculated for the method by iteration Value and phase, and evaluating, the computing module main body module are made up of two layers of circulation, and outer loop controls the low frequency The number of times of harmonic highest subharmonic, interior loop by Optimization Method respond described in low-frequency harmonics part Value, the amplitude and phase of each harmonic;
An objective function unit is provided with the computing module main body module, the low frequency is solved for constitution optimization Object function in harmonic when average, the amplitude of each harmonic and phase, in an iterative process, the expression of object function The number of average, the amplitude of each harmonic and phase is in dynamic change, institute in formula form, the low-frequency harmonics part to be optimized It is exactly to be used for constructing this object function to state objective function unit.
2. single-mode system harmonic balance subtraction unit according to claim 1, it is characterised in that applicable single-degree-of-freedom Nonlinear system is expressed as equation
In formula, t is the time;Y (t) is the response of system, that is, is exported;The single order that respectively responds, second dervative;For onWithFunction;F (t) is excitation, that is, is inputted;
Characterized in that, in the calculating unit, solving what average, the amplitude of the limited subharmonic and phase in response were used Method comprises the following steps:
S1:Represent the cyclic variable k of the highest subharmonic number of times of the low-frequency harmonics part, interior loop variable i and put initial value:k Put initial value in=1, i=1, the high-frequency harmonic part:yHF(t)=0, the initial value X0 of Optimization Solution is set;
S2:Optimization method calculates average, the amplitude of each harmonic and phase in the low-frequency harmonics part, including:
S21:Calculate the low-frequency harmonics part yLF(t) expression formula
In formula, A0/ 2 be average, AnWithThe respectively amplitude and phase of n-th harmonic, k be in the low-frequency harmonics part most The number of times of higher hamonic wave;Ω1For the angular frequency of the angular frequency of fundamental wave, i.e. first harmonic;
S22:Calculate the response y (t) of nonlinear system expression formula (6)
Y (t)=yLF(t)+yHF(t) (6)
S23:Seek error in equation sequence e (tm) character expression, seek its FFT character expression
In formula, tmFor discrete time point, m=1,2,3 ..., N, N is the points of the error in equation series of discrete;
S24:Seek the expression formula of object function
S25:With formula (9) minimum optimization aim, average, the amplitude of each harmonic and phase in the low-frequency harmonics part are obtainedValue;
S26:By the amplitude A of each harmonic in the low-frequency harmonics part1, A2..., AkIt is converted into nonnegative value, phaseBe transformed into it is interval [0,2 π) on, method is:
S3:Iterative initial value, the high-frequency harmonic part are updated, including:
S31:Calculate the error in equation sequence e (tm) numerical expression, accounting equation error mean square root erms
S32:Judge whether interior loop meets exit criteria:1. the error in equation root-mean-square value ermsIt is reduced to the essence of setting Degree, 2. the iterations i of interior loop reaches the upper limit of setting,
If meeting any of which condition, turning S4 increases the number of times k of the low-frequency harmonics part highest subharmonic, continues to change In generation, if be all unsatisfactory for, turn S33;
S33:The high-frequency harmonic part is updated, the initial value X0 of nonlinear optimization, cyclic variable increase by 1 are set:I=i+1, turns S22 continues iteration, wherein, use equation below and step:
S331:The concrete numerical value of calculating formula (11),
In formula, yLFFor yLF(t) shorthand, yHFFor yHF(t) shorthand,For yLF(t) first derivative, For yHF(t) first derivative;
S332:The amplitude and phase of the harmonic wave included with FFT calculating formulas (11), be translated into cosine function and SIN function it The form of sum, obtains amplitude anWith bn, seek the expression formula (12) of the estimate of the high-frequency harmonic part
S4:Judge whether the cyclic variable k for representing the highest subharmonic number of times of the low-frequency harmonics part is not more than the upper of setting Number of times, or not up to precision conditions are limited,
If it is, the initial value X0 of the nonlinear optimization is set, cyclic variable k increases by 1:K=k+1, goes to step S2;
Otherwise, calculating terminates.
3. single-mode system harmonic balance subtraction unit according to claim 2, it is characterised in that in step S4, the upper limit Number of times is not more than the half N/2 of the points N of error in equation series of discrete described in step S2.
4. single-mode system harmonic balance subtraction unit according to claim 3, it is characterised in that in step S4, precision Condition is that outer loop previous cycle, i.e. kth wheel are circulated, equal with the error in equation root-mean-square value that last round of circulation is obtained Or difference be less than setting the limits of error.
5. single-mode system harmonic balance subtraction unit according to claim 4, it is characterised in that
In step S3, the initial value X0 of nonlinear optimization method to set up is:In this i wheel circulations of the interior loop from 1 to i, When ith is circulated, by optimizing obtained average, harmonic amplitude and phase in step S2,
In step S4, the initial value X0 of the nonlinear optimization includes 2k+3 element, is this k repeating query of outer loop from 1 to k In ring, under kth time circulation, in corresponding interior loop, when ith is circulated, the result obtained in step S2 and S3, wherein 2k+1 Individual element is by optimizing obtained average, harmonic amplitude and phase in step S2;Other 2 elements are FFT meters in step S3 The amplitude and phase of obtained corresponding harmonic wave.
6. single-mode system harmonic balance subtraction unit according to claim 4, it is characterised in that
In step S3, the initial value X0 of nonlinear optimization method to set up is:In this i wheel circulations of the interior loop from 1 to i, When ith is circulated, by optimizing obtained average, harmonic amplitude and phase in step S2,
In step S4, the initial value X0 of the nonlinear optimization includes 2k+3 element, is this k wheel circulation of the outer loop from 1 to k In, under kth time circulation, in this i wheel circulations of the corresponding interior loop from 1 to i, minimum error mean square root ermsIt is corresponding As a result, wherein 2k+1 element is by optimizing obtained average, harmonic amplitude and phase in step S2;Other 2 elements are FFT calculates the amplitude and phase of obtained corresponding harmonic wave in step S3.
7. single-mode system harmonic balance subtraction unit according to claim 4, it is characterised in that
Step S33 detailed step is:Judge the error in equation root-mean-square value ermsWhether it is less than what last round of iteration was obtained Value, if it is not, then the initial value X0 of nonlinear optimization adds random perturbation, cyclic variable increase by 1 on the basis of original:i =i+1, turns S2 and continues iteration;Otherwise, S331 and S332 is performed, iterative initial value X0 is set to what is obtained in step S2 by optimization Average, harmonic amplitude and phase, if the error in equation root-mean-square value ermsThe error mean square root obtained with last round of iteration Difference be less than the limits of error of setting, then in X0 along with random perturbation,
In step S4, the initial value X0 of the nonlinear optimization includes 2k+3 element, is this k wheel circulation of the outer loop from 1 to k In, under kth time circulation, in corresponding interior loop, when ith is circulated, the result obtained in step S2 and S3, wherein 2k+1 Element is by optimizing obtained average, harmonic amplitude and phase in step S2;Other 2 elements are FFT calculating in step S3 The amplitude and phase of obtained corresponding harmonic wave.
8. the single-mode system harmonic balance subtraction unit according to claim 5,6 or 7, it is characterised in that step S21~ S24 symbolization computings, step S3 uses numerical operation.
9. single-mode system harmonic balance subtraction unit according to claim 8, it is characterised in that the symbolic variable is determined In adopted part, when being realized using perceptive construction on mathematics, the symbolic variable of average, amplitude and phase is represented by prefix and numeral Two parts are constituted, and average, the prefix of amplitude symbolic variable are identical in Part I, and the prefix of phase symbol variable is identical, and second Part number is positive integer numeral, and the determination method of digit is:If the highest harmonic wave of limited subharmonic described in response Number is M, then the minimum value of the digit of Part II numeral isIf digit is not enough, above with numeral 0 Supply.
10. single-mode system harmonic balance subtraction unit according to claim 9, it is characterised in that the object function The method that structural unit is used comprises the following steps:
a:Expression formula (4) is converted into character string myObjFunStr1 with char functions;
b:Then character string myObjFunStr1 average is replaced with into character string with character string replacement function strrep:X (1), Amplitude replaces with character string:X (2), x (3) ..., x (k), x (k+1), phase replaces with character string:x(k+2)、x(k+3)、…、x (2k), x (2k+1), obtains representing the character string type expression formula myObjFunStr2 of object function;
c:Before character string myObjFunStr2 plus character string '@(x) ', obtain new character string myObjFunStr3;
d:Character string myObjFunStr3 is converted into object function with eval functions.
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