CN103905017A - Novel chaotic spread-spectrum SPWM wave generating method - Google Patents

Abstract

A novel chaotic spread-spectrum SPWM wave generating method comprises the steps that (1), a changing area of chaos variable parameters of an inter-conversion double-chaos sequence is determined; (2), fixed chaos parameters of a Logistic chaos sequence and a Tent chaos sequence are replaced by chaotic variable parameters; (3), a chaos sequence is generated through the chaotic viable parameters; (4) a slope coefficient of chaos triangular waves is calculated; (5), the slope of the chaos triangular waves is made to be chaotic through the inter-conversion double-chaos sequence; (6), a chaos triangular wave value is obtained through counting of an external clock of a SPWM wave generating module; (7), when the counting value of the chaos triangular waves reaches zero, the above steps are executed again, so that the chaos triangular waves are obtained, and the value of the chaos triangular waves is stored in a TRG for invoking; (8), parameters of a sine wave needing to be modulated are obtained from a controller to generate a sine table; (9) the update step length of the sine table is calculated; (10), a sine wave value is updated; (11), the sine wave value is obtained and stored in SIN for invoking; (12), the TRG is compared with the SIN, and chaotic SPWM waves are output. The novel chaotic spread-spectrum SPWM wave generating method has the advantages of being quick, real-time and low in harmonic wave.

Description

A kind of new chaotic spread spectrum SPWM ripple generation method

Technical field

The present invention relates to the generation technique field of SPWM ripple, be specifically related to a kind of new chaotic spread spectrum SPWM ripple generation method.

Background technology

The circuit of frequency converter is generally by rectification, intermediate dc link, inversion and controlling composition, and Voltage-output is PWM (Pulse width modulation, PWM) waveform.PWM is exactly pulse width modulation, the namely impulse waveform of variable duty ratio, and in reality output, different duty ratios is equivalent to different output levels, thereby can be equivalent to by regulating duty recently to reach the effect of analog voltage output.PWM control technology, take this conclusion as theoretical foundation, is controlled the turn-on and turn-off of semiconductor switch device, makes output obtain a series of amplitudes and equates and the unequal pulse of width, replaces sine wave or other needed waveforms with these pulses.By certain rule, the width of each pulse is modulated, both can be changed the size of inverter circuit output voltage, also can change output frequency.

Be that PWM ripple is exactly SPWM ripple by sine wave modulation, general frequency converter is substantially all directly to carry out the electric power such as direct-driving motor, transformer apparatus with SPWM ripple now.SPWM ripple is easy to use, be easy to realize, but the harmonic wave peak value that SWPM ripple comprises is very large, especially, near the switching frequency of semiconductor switch device, can form a high harmonic wave peak value.Harmonic wave causes electromagnetic interference in the meeting in service of power equipment, the quality of impact output electric energy; If transducer drive is motor, also likely causes mechanical resonant to make system cisco unity malfunction, and reduce motor useful life.

In field of power electronics, chaos sequence is modulated to SPWM ripple for the chaos spread spectrum of triangular wave, there is positive effect to reducing electromagnetic interference (electromagnetic interference, EMI) and eliminating mechanical resonant.In SPWM modulation, high order harmonic component can concentrate near the multiple of switching frequency and switching frequency, and reach very high peak value, triangular wave is carried out to chaos spread spectrum and can make the successive value of switching frequency in fixed value becomes certain interval, corresponding high order harmonic component distributes and is also become continuously from discrete, thereby reaches the object that reduces harmonic wave peak value.The major issue of this method in the time of application is to produce real-time chaos sequence, and in digital control, chaos sequence is subject to numerical calculation Accuracy, must deteriorate to periodic sequence.By periodic sequence, triangular wave is carried out to spread spectrum, can near sequence period and the product in triangular wave cycle, form a higher harmonic wave.

Summary of the invention

The problem existing in order to solve above-mentioned prior art, the object of the present invention is to provide a kind of new chaotic spread spectrum SPWM ripple generation system and method, has feature quick, real-time, low harmonic wave.

In order to reach above object, the present invention adopts following technical scheme:

A kind of new chaotic spread spectrum SPWM ripple generation method, comprises the steps:

Step 1: the constant interval of the chaos variable element of the two chaos sequences of variable element ratio-dependent change parameter as required, the two chaos sequences of described change parameter by Logistic chaos sequence and Tent chaos sequence in conjunction with generation,

y _n/K ₁ (1)

x _n/K ₂ (2)

In formula: x _nfor Logistic chaos sequence value; y _nfor Tent chaos sequence value; K ₁, K ₂for the variable element ratio of setting, can determine the constant interval of chaotic parameter by changing its size;

Step 2: obtain after the constant interval of chaos variable element, the fixing chaotic parameter of Logistic chaos sequence and Tent chaos sequence is replaced with to chaos variable element, obtain chaos variable element suc as formula shown in (3), formula (4):

${\stackrel{\‾}{K}}_x=K_x-y_n/K_1---\left(3\right)$

${\stackrel{\‾}{K}}_y=K_y-x_n/K_2---\left(4\right)$

In formula: K _xfor the original fixing chaotic parameter of Logistic of setting, K _yfor the original fixing chaotic parameter of Tent of setting, the Logistic chaos variable element calculating with Tent chaos variable element in given area, present chaos change;

Step 3: utilize chaos variable element to generate chaos sequence: for realizing quick computing, by Logistic chaos sequence value x _nwith Tent chaos sequence value y _nexpansion rounds, calculate with integer form, under 16 binary system precision; get excursion for (0; 60000), the chaos sequence that two kinds of mappings of Logistic and Tent are produced presents chaos change in (0,60000) scope; formula (3), formula (4), respectively as the new chaotic parameter of Logistic and Tent chaotic maps formula, are carried out to interative computation according to formula (5) and obtained chaos sequence in order to calling;

$\left\{\begin{array}{c}{x}_{n+1}={\stackrel{\‾}{K}}_x\·x_n(60000-x_n)/60000\\ y_{n+1}={\stackrel{\‾}{K}}_x\·\min (y_n,60000-y_n)\end{array}\right.---\left(5\right)$

Step 4: the parameter that obtains chaos triangular wave from controller is maximum amplitude, frequency and chaos frequency conversion ratio, according to the slope coefficient P of the calculation of parameter chaos triangular wave obtaining ₀, its calculating formula as the formula (6):

P ₀=2DNF _sin/F _clk （6）

In formula: P ₀for slope coefficient is the ratio of external clock frequency and chaos triangular wave count frequency, D is chaos triangular wave maximum amplitude, F _sinfor sine wave freuqency to be modulated, F _clkfor external clock frequency;

Step 5: utilize the two chaos sequences of change parameter by chaotization chaos triangular wave slope, select Logistic chaos sequence value x _n, obtain chaos frequency conversion ratio K from controller ₃, utilize formula (7) by chaotization chaos triangular wave slope:

P=P ₀(1-K ₃+2K ₃·x _n/60000) （7）

In formula: P is the chaos triangular wave slope coefficient after chaotization, the triangular wave slope obtaining after chaotization is at (1-K ₃p ₀, 1+K ₃p ₀) in present chaos change, triangular wave frequency is at (1-K ₃f _sin, 1+K ₃f _sin) present chaos change in scope, but its equivalent frequency is F _sin;

Step 6: utilize the external clock of SPWM ripple generation module to count to get chaos triangle wave number, represent triangular wave currency, COUNTER with TRG _trgrepresent external clock counter.In each external clock cycle, make COUNTER _trg=COUNTER _trg+ 1, and chaos triangle wave number TRG is by count value COUNTER _trgbeing multiplied by slope P obtains;

TRG=COUNTER _trg*P (8)

Step 7: in the time that chaos triangle wave number TRG reaches maximum D, subtract counting, count value COUNTER from increasing to count to become _trgzero clearing, slope is still P, in each external clock cycle, makes COUNTER _trg=COUNTER _trg+ 1, and chaos triangle wave number TRG deducts count value COUNTER by maximum D _trgbeing multiplied by slope P obtains;

TRG=D-COUNTER _trg*P (9)

Step 8: in the time that chaos triangular wave count value reaches 0, repeat above step, can obtain chaos triangular wave, its value is stored in TRG in order to calling;

Step 9: obtain the sinusoidal wave parameter that needs modulation: amplitude A from controller _sin, frequency F _sinwith initial phase P _sin, generate sine table sina[according to amplitude and phase place];

Step 10: according to sine table precision, sine wave freuqency calculates sine table and upgrades step-length N _sinif precision is 2 °, when sine table comprises 180 data, calculating formula is suc as formula (10):

N _sin=F _clk/(F _sin*180)（10）

Step 11: utilize the external clock of SPWM ripple generation module to calculate sinusoidal wave number, with COUNTER _sinrepresent the sine table position that current sinusoidal wave number is corresponding, represent sinusoidal wave value with SIN, according to external clock to COUNTER _sincounting, counting is often expired N _sinthe inferior COUNTER that makes _sin=COUNTER _sin+ 1 and upgrade sinusoidal wave number SIN, i.e. SIN=sina[COUNTER _sin];

Step 12: in the time that sine table is read last value, return to sine table heading, work as COUNTER _sin=180 o'clock, by its zero clearing COUNTER _sin=0, repeat the 9th to the 12nd step and can obtain sinusoidal wave value, be stored in SIN in order to calling;

Step 13: by TRG and SIN comparison, output chaos SPWM waveform.

Described as follows in conjunction with the method that generates the two chaos sequences of change parameter by Logistic chaos sequence and Tent chaos sequence:

The primitive form of described Logistic chaos sequence and Tent chaos sequence is as follows respectively:

x _n+1=K _xx _n(1-x _n),K _x∈(3.5699456,4),x∈(0,1) （11）

y _n+1=K _ymin(y _n,1-y _n),K _y∈(1,2),y∈(0,1) （12）

Wherein K _xfor the chaotic parameter of Logistic chaos sequence, K _yfor the chaotic parameter of Tent chaos sequence, x _nfor Logistic chaos sequence value, y _nfor Tent chaos sequence value, interative computation of every execution, sequential value changes once, obtains the Logistic chaos sequence value x after interative computation _n+1with Tent chaos sequence value y _n+1, obtain sequential value for the chaos sequence in (0,1) interval;

For avoiding the computing of floating number, do not adopt normalized chaos generation mapping equation, but calculate with integer form.Expand sequence span for this reason, but keep chaotic parameter constant.By chaos sequence value x _n, y _nconstant interval expand to (0,60000), formula (11) and formula (12) can be changed into formula (13) and formula (14):

The mapping equation of Logistic chaos sequence is

x _n+1=K _xx _n(60000-x _n)/60000,x _n∈(0,60000) (13)

The mapping equation of Tent chaos sequence is

y _n+1=K _ymin(y _n,60000-y _n),y _n∈(0,60000) (14)

In formula: x _nfor Logistic chaos sequence value; y _nfor Tent chaos sequence value; K _xfor the Logistic chaotic parameter of formula (13), K _yfor the Tent chaotic parameter of formula (14), the chaos sequence that these two kinds of mapping equations produce presents chaos change in (0,60000) scope;

Change the chaotic parameter K of the Logistic chaos sequence in formula (13) with Tent chaos sequence result _xvalue, the while changes the chaotic parameter K of Tent chaos sequence with Logistic chaos sequence result _yvalue;

Use formula (15) by the Logistic chaotic parameter K in formula (13) for this reason _xreplace with the Logistic chaotic parameter after improvement

logistic chaotic parameter after improvement

for

${\stackrel{\‾}{K}}_x=K_x-y_n/\left(1000K_1\right)---\left(15\right)$

In formula: y _nfor Tent chaos sequence value in formula (14); K ₁for the variable element ratio of setting; K _xfor the chaotic parameter of former chaos sequence setting.Chaos variable element

in the excursion of setting, present chaos change;

Ky in formula (14) is replaced with by formula (16)

for

${\stackrel{\‾}{K}}_y=K_y-x_n/\left(1000K_2\right)---\left(16\right)$

In formula: x _nfor Logistic chaos sequence value in formula (13); K ₂for the variable element ratio of setting; K _yfor the chaotic parameter of former chaos sequence; Equally, chaotic parameter in the excursion of setting, present chaos change;

By formula (15), formula (16) substitution formula (13), formula (14) respectively, obtain the two chaos sequence equations of change parameter and be

$\left\{\begin{array}{c}{x}_{n+1}={\stackrel{\‾}{K}}_x\·x_n(60000-x_n)/60000=[K_x-\\ y_n/\left(1000K_1\right)]x_n(60000-x_n)/60000\\ y_{n+1}={\stackrel{\‾}{K}}_x\·\min (y_n,60000-y_n)=[K_y-\\ x_n/\left(1000K_2\right)]\min (y_n,60000-y_n)\end{array}\right.---\left(17\right)$

In formula: x _n, y _nthe chaos sequence value that is respectively Logistic and Tent n step, regulates K ₁, K ₂and K _x, K _ysize, adjusting chaos variable element that can be corresponding

excursion; Same up-to-date style (17) just generates the two change parameter chaos sequences that are listed in given area.

Compared to the prior art, the present invention has the following advantages:

One, the two chaos sequences of this change parameter are compared with traditional Logistic chaos sequence, Tent chaos sequence, and in the case of same computational accuracy, chaos cycle stretch-out is more than 100 times.

Two, the two chaos sequence algorithms of this change parameter are highly suitable for the parallel arithmetic mode of FPGA, in real-time operation, can reach very high speed, and this algorithm adopted integer calculations form, on FPGA when computing without building floating-point mould, take resource few, real-time is good.

Three, this algorithm designs for operation platform with FPGA, and it is upper that its main computing work is placed on FPGA, on the hardware platform of FPGA collocation main control chip type, can save the calculation resources of main control chip in large quantities, improves the speed of service.

Accompanying drawing explanation

Fig. 1 is chaos triangular wave chaos spread spectrum principle schematic.

Fig. 2 is chaos SPWM ripple modulation principle schematic diagram, and wherein: Fig. 2 (a) is sinusoidal pattern, Fig. 2 (b) is chaos triangular wave figure, and Fig. 2 (c) is chaos SPWM ripple figure.

Fig. 3 is SPWM ripple harmonic analysis result spectrogram, wherein: Fig. 3 (a) is the SPWM ripple frequency spectrum of constant frequency triangular modulation, Fig. 3 (b) is the SPWM ripple frequency spectrum that uses the chaos triangular modulation after conventional Logistic chaos sequence spread spectrum, and Fig. 3 (c) is the SPWM ripple frequency spectrum of chaos triangular modulation of the present invention.

Fig. 4 is SPWM wave power analysis of spectrum result, wherein: Fig. 4 (a) is the SPWM wave energy spectrum of constant frequency triangular modulation, Fig. 4 (b) is the SPWM wave energy spectrum that uses the chaos triangular modulation after conventional Logistic chaos sequence spread spectrum, and Fig. 4 (c) is the SPWM wave energy spectrum of chaos triangular modulation of the present invention.

Embodiment

Below in conjunction with the drawings and specific embodiments, the present invention is described in further details.

In the present embodiment, require a sine wave of modulation, its parameter is as follows: amplitude 250, and frequency is 50Hz, initial phase is 180 °.Modulation requires: carrier wave ratio 50, and modulation ratio 1, chaos frequency conversion scope is 50%.The external clock of external hardware condition: FPGA is 10MHz.

Step 1: determine the constant interval of the chaos variable element of the two chaos sequences of change parameter, get K ₁=2000000, K ₂=300000.

y _n/2000000 (1)

x _n/300000 (2)

In formula: x _nfor Logistic chaos sequence value; y _nfor Tent chaos sequence value; Because its span is that (0,60000) is therefore can determine that the constant interval of chaotic parameter is respectively (0,0.003) and (0,0.02).

Step 2: obtain after the constant interval of chaos variable element, the fixing chaotic parameter of Logistic chaos sequence and Tent chaos sequence is replaced with to parameter variable element.The original chaotic parameter K of assignment Logistic _x=3.9999, Tent chaos initial parameter K _y=1.9999, in order to represent with integer form, be written as K _x=39999/10000, K _y=19999/10000.Obtain chaos variable element suc as formula shown in (3), formula (4):

${\stackrel{\‾}{K}}_x=K_x-y_n/K_1---\left(3\right)$

${\stackrel{\‾}{K}}_y=K_y-x_n/K_2---\left(4\right)$

Calculate chaos variable element

between given area, in (3.9969,3.9999) and (1.9799,1.9999), presenting chaos change respectively.

Step 3: utilize chaos variable element to generate chaos sequence.New chaotic parameter using formula (3), formula (4) as Logistic and Tent, carries out interative computation according to formula (5) and obtains in interval in (0,60000) becoming the chaos sequence of chaos change in order to calling.

$\left\{\begin{array}{c}{x}_{n+1}={\stackrel{\‾}{K}}_x\·x_n(60000-x_n)/60000\\ y_{n+1}={\stackrel{\‾}{K}}_x\·\min (y_n,60000-y_n)\end{array}\right.---\left(5\right)$

Step 4: obtain the parameter of chaos triangular wave from controller, carry out initialization according to the parameter obtaining, triangular modulation principle as shown in Figure 1:

Obtain slope coefficient P according to the triangular wave frequency of setting ₀, its calculating formula as the formula (6):

P ₀=2DNF _sin/F _clk （6）

Now known triangular wave frequency is 50, and modulation ratio is 50, and maximum amplitude is 500.External clock is 10MHz, therefore its slope is P ₀=2500Hz*1000/ (10MHz)=0.25.

Step 5: utilize the two chaos sequences of change parameter by chaotization chaos triangular wave slope.Select Logistic chaos sequence x _n, obtain chaos frequency conversion ratio K from controller ₃, because the frequency conversion ratio requiring is 50%, K ₃=0.5.Triangular wave slope is chaotization to be had:

P=0.25(0.5+x _n/60000) （7）

The triangular wave slope obtaining after chaotization presents chaos change in (0.125,0.375), and triangular wave frequency presents chaos change in (1.25kHz, 3.75kHz) scope, but its equivalent average frequency is 2.5kHz.

Step 6: utilize the external clock of SPWM ripple generation module to count to get chaos triangle wave number, represent triangular wave currency, COUNTER with TRG _trgrepresent external clock counter.In each external clock cycle, make COUNTER _trg=COUNTER _trg+ 1, and triangle wave number TRG is by count value COUNTER _trgbeing multiplied by slope P obtains.

TRG=COUNTER _trg*P (8)

Step 7: in the time that triangle wave number TRG reaches maximum 500, subtract counting, count value COUNTER from increasing to count to become _trgzero clearing, slope is still P.In each external clock cycle, make COUNTER _trg=COUNTER _trg+ 1, be multiplied by slope and obtain and triangle wave number TRG deducts count value by maximum.

TRG=500-COUNTER _trg*P (9)

Step 8: in the time that triangular wave count value reaches 0, repeat above step, can obtain chaos triangular wave data.Its value is stored in TRG in order to calling.

Step 9: obtained the sine wave parameter that needs modulation, amplitude A by controller _sin, frequency F _sin, initial phase P _sin.According to amplitude and phase place initialization sine table sina[].After initialization, set sinusoidal wave amplitude A _sin=250, frequency F _sin=50, and phase parameter P _sin=180.Offset of sinusoidal table sina[simultaneously] carry out initialization, sina[after initialization] represent that sine value is multiplied by A _sinafter be lifted on the occasion of result.In this example, get sinusoidal wave precision for twice, by sine table be lifted on the occasion of, constant interval is lifted to (0,500) by (250,250).Obtain sine table slightly.

Step 10: according to external clock, sine table precision, sine wave freuqency calculates sine table and upgrades step-length N _sinif precision is 2 °, when sine table comprises 180 data, calculating formula is suc as formula (10):

N _sin=F _clk/(F _sin*180) （10）

Calculating renewal step-length is 10M/ (50*180)=1111.

Step 11: with COUNTER _sinrepresent the sine table position that current sinusoidal wave number is corresponding, represent sinusoidal wave value with SIN.Because initial phase is 180 °, the COUNTER after initialization _sin=90.According to external clock to COUNTER _sincounting, counting is often expired N _sineven inferior COUNTER _sin=COUNTER _sin+ 1 and upgrade sinusoidal wave number SIN, i.e. SIN=sina[COUNTER _sin].

Step 12: in the time that sine table is read last value, return to heading, work as COUNTER _sin=180 o'clock, by its zero clearing COUNTER _sin=0.Repeat the 9th to the 12nd step and can obtain sinusoidal wave value, be stored in SIN in order to calling.

Step 13: be that Fig. 2 (a) is that Fig. 2 (b) compares with chaos triangle wave number TRG by sinusoidal wave number SIN, output chaos SPWM waveform is Fig. 2 (c).In the time of SIN>TRG, export 1 otherwise output 0.

Algorithm effect:

PWM waveform after PWM waveform after the PWM waveform of generation and traditional Logistic chaos sequence spread spectrum and constant frequency triangular wave waveform spread spectrum is analyzed to contrast.Show its harmonic content analysis and energy spectrum analysis, as shown in Figure 3 and Figure 4.

As shown in Figure 3, the high order harmonic component of the SPWM ripple of constant frequency triangular modulation concentrates near the multiple of switching frequency and switching frequency, has higher peak value.Triangular wave is carried out after chaos spread spectrum, and switching frequency is become continuously from discrete, harmonic wave is distributed and also become continuously from discrete, and in the situation that harmonic wave total amount is constant, corresponding harmonic wave peak value obviously reduces.From Fig. 3 (b), the harmonic wave peak value of conventional Logistic chaos algorithm drops to 15% from 45%, and algorithm in this paper is with respect to conventional Logistic chaos algorithm, maximum harmonic wave peak value further can be dropped to 5% from 15%, harmonic wave peak value inhibition is better.

As shown in Figure 4, in Fig. 4 (a), the harmonic power peak value of SPWM ripple is very high and more discrete.In Fig. 4 (b), power spectrum becomes continuously, and harmonic power peak value is from-drop to-30dB of 20dB, new algorithm in this paper further by harmonic power peak reduction to-35dB.

Claims (2)

1. a new chaotic spread spectrum SPWM ripple generation method, is characterized in that: comprise the steps:

Step 1: the constant interval of the chaos variable element of the two chaos sequences of variable element ratio-dependent change parameter as required, the two chaos sequences of described change parameter by Logistic chaos sequence and Tent chaos sequence in conjunction with generation,

y _n/K ₁ (1)

x _n/K ₂ (2)

In formula: x _nfor Logistic chaos sequence value; y _nfor Tent chaos sequence value; K ₁, K ₂for the variable element ratio of setting, can determine the constant interval of chaotic parameter by changing its size;

Step 2: obtain after the constant interval of chaos variable element, the fixing chaotic parameter of Logistic chaos sequence and Tent chaos sequence is replaced with to chaos variable element, obtain chaos variable element suc as formula shown in (3), formula (4):

${\stackrel{\‾}{K}}_x=K_x-y_n/K_1---\left(3\right)$

${\stackrel{\‾}{K}}_y=K_y-x_n/K_2---\left(4\right)$

In formula: K _xfor the original fixing chaotic parameter of Logistic of setting, K _yfor the original fixing chaotic parameter of Tent of setting, the Logistic chaos variable element calculating

with Tent chaos variable element

in given area, present chaos change;

Step 3: utilize chaos variable element to generate chaos sequence: for realizing quick computing, by Logistic chaos sequence value x _nwith Tent chaos sequence value y _nexpansion rounds, calculate with integer form, under 16 binary system precision; get excursion for (0; 60000), the chaos sequence that two kinds of mappings of Logistic and Tent are produced presents chaos change in (0,60000) scope; formula (3), formula (4), respectively as the new chaotic parameter of Logistic and Tent chaotic maps formula, are carried out to interative computation according to formula (5) and obtained chaos sequence in order to calling;

$\left\{\begin{array}{c}{x}_{n+1}={\stackrel{\‾}{K}}_x\·x_n(60000-x_n)/60000\\ y_{n+1}={\stackrel{\‾}{K}}_x\·\min (y_n,60000-y_n)\end{array}\right.---\left(5\right)$

Step 4: the parameter that obtains chaos triangular wave from controller is maximum amplitude, frequency and chaos frequency conversion ratio, according to the slope coefficient P of the calculation of parameter chaos triangular wave obtaining ₀, its calculating formula as the formula (6):

P ₀=2DNF _sin/F _clk （6）

In formula: P ₀for slope coefficient is the ratio of external clock frequency and chaos triangular wave count frequency, D is chaos triangular wave maximum amplitude, F _sinfor sine wave freuqency to be modulated, F _clkfor external clock frequency;

Step 5: utilize the two chaos sequences of change parameter by chaotization chaos triangular wave slope: to select Logistic chaos sequence value x _n, obtain chaos frequency conversion ratio K from controller ₃, utilize formula (7) by chaotization chaos triangular wave slope:

P=P ₀(1-K ₃+2K ₃·x _n/60000) （7）

In formula: P is the chaos triangular wave slope coefficient after chaotization, the triangular wave slope obtaining after chaotization is at (1-K ₃p ₀, 1+K ₃p ₀) in present chaos change, triangular wave frequency is at (1-K ₃f _sin, 1+K ₃f _sin) present chaos change in scope, but its equivalent frequency is F _sin;

Step 6: utilize the external clock of SPWM ripple generation module to count to get chaos triangle wave number, represent triangular wave currency, COUNTER with TRG _trgrepresent external clock counter.In each external clock cycle, make COUNTER _trg=COUNTER _trg+ 1, and chaos triangle wave number TRG is by count value COUNTER _trgbeing multiplied by slope P obtains;

TRG=COUNTER _trg*P (8)

Step 7: in the time that chaos triangle wave number TRG reaches maximum D, subtract counting, count value COUNTER from increasing to count to become _trgzero clearing, slope is still P, in each external clock cycle, makes COUNTER _trg=COUNTER _trg+ 1, and chaos triangle wave number TRG deducts count value COUNTER by maximum D _trgbeing multiplied by slope P obtains;

TRG=D-COUNTER _trg*P (9)

Step 8: in the time that chaos triangular wave count value reaches 0, repeat above step, can obtain chaos triangular wave, its value is stored in TRG in order to calling;

Step 9: obtain the sinusoidal wave parameter that needs modulation: amplitude A from controller _sin, frequency F _sinwith initial phase P _sin, generate sine table sina[according to amplitude and phase place];

Step 10: according to sine table precision, sine wave freuqency calculates sine table and upgrades step-length N _sinif precision is 2 °, when sine table comprises 180 data, calculating formula is suc as formula (10):

N _sin=F _clk/(F _sin*180) （10）

Step 11: utilize the external clock of SPWM ripple generation module to calculate sinusoidal wave number, with COUNTER _sinrepresent the sine table position that current sinusoidal wave number is corresponding, represent sinusoidal wave value with SIN, according to external clock to COUNTER _sincounting, counting is often expired N _sinthe inferior COUNTER that makes _sin=COUNTER _sin+ 1 and upgrade sinusoidal wave number SIN, i.e. SIN=sina[COUNTER _sin];

Step 12: in the time that sine table is read last value, return to sine table heading, work as COUNTER _sin=180 o'clock, by its zero clearing COUNTER _sin=0, repeat the 9th to the 12nd step and can obtain sinusoidal wave value, be stored in SIN in order to calling;

Step 13: by TRG and SIN comparison, output chaos SPWM waveform.

2. a kind of new chaotic spread spectrum SPWM ripple generation method according to claim 1, is characterized in that: described as follows in conjunction with the method that generates the two chaos sequences of change parameter by Logistic chaos sequence and Tent chaos sequence:

The primitive form of described Logistic chaos sequence and Tent chaos sequence is as follows respectively:

x _n+1=K _xx _n(1-x _n),K _x∈(3.5699456,4),x∈(0,1) （11）

y _n+1=K _ymin(y _n,1-y _n),K _y∈(1,2),y∈(0,1) （12）

Wherein K _xfor the chaotic parameter of Logistic chaos sequence, K _yfor the chaotic parameter of Tent chaos sequence, x _nfor Logistic chaos sequence value, y _nfor Tent chaos sequence value, interative computation of every execution, sequential value changes once, obtains sequential value for the chaos sequence in (0,1) interval; x _n+1for the Logistic chaos sequence value after interative computation, y _n+1for the Tent chaos sequence value after interative computation.

By chaos sequence value x _n, y _nconstant interval expand to (0,60000), formula (11) and formula (12) can be changed into formula (13) and formula (14):

The mapping equation of Logistic chaos sequence is

x _n+1=K _xx _n(60000-x _n)/60000,x _n∈(0,60000) (13)

The mapping equation of Tent chaos sequence is

y _n+1=K _ymin(y _n,60000-y _n),y _n∈(0,60000) (14)

In formula: x _nfor Logistic chaos sequence value; y _nfor Tent chaos sequence value; K _xfor the Logistic chaotic parameter of formula (13), K _yfor the Tent chaotic parameter of formula (14), the chaos sequence that these two kinds of mapping equations produce presents chaos change in (0,60000) scope;

Change the chaotic parameter K of the Logistic chaos sequence in formula (13) with Tent chaos sequence result _xvalue, the while changes the chaotic parameter K of Tent chaos sequence with Logistic chaos sequence result _yvalue; Use formula (15) by the Logistic chaotic parameter K in formula (13) for this reason _xreplace with the Logistic chaotic parameter after improvement

logistic chaotic parameter after improvement

for

${\stackrel{\‾}{K}}_x=K_x-y_n/\left(1000K_1\right)---\left(15\right)$

In formula: y _nfor Tent chaos sequence value in (14) formula; K ₁for the variable element ratio of setting; K _xfor the chaotic parameter of former chaos sequence setting.Chaos variable element

in the excursion of setting, present chaos change;

By formula (16) by Tent chaotic parameter K in formula (14) _yreplace with the Tent chaotic parameter after improvement

tent chaotic parameter after improvement

for

${\stackrel{\‾}{K}}_y=K_y-x_n/\left(1000K_2\right)---\left(16\right)$

In formula: x _nfor Logistic chaos sequence value in formula (13); K ₂for the variable element ratio of setting; K _yfor the chaotic parameter of former chaos sequence; Equally, chaotic parameter

in the excursion of setting, present chaos change;

By formula (15), formula (16) substitution formula (13), formula (14) respectively, obtain the two chaos sequence equations of change parameter and be

$\left\{\begin{array}{c}{x}_{n+1}={\stackrel{\‾}{K}}_x\·x_n(60000-x_n)/60000=[K_x-\\ y_n/\left(1000K_1\right)]x_n(60000-x_n)/60000\\ y_{n+1}={\stackrel{\‾}{K}}_x\·\min (y_n,60000-y_n)=[K_y-\\ x_n/\left(1000K_2\right)]\min (y_n,60000-y_n)\end{array}\right.---\left(17\right)$

In formula: x _n, y _nthe chaos sequence value that is respectively Logistic and Tent n step, regulates K ₁, K ₂and K _x, K _ysize, adjusting chaos variable element that can be corresponding

excursion; Formula (17) generates the two change parameter chaos sequences that are listed in given area.

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