CN101339409B - Digital-analog and analog-digital transition card identification method based on equivalent model transform - Google Patents

Abstract

The present invention discloses a method for identifying digital-to-analog (D/A) and analog-to-digital (A/D) conversion cards on the basis of equivalent model conversion, belonging to the technical field of industrial control. The method comprises the steps of: establishing a test platform of the D/A conversion card and the A/D conversion card by adopting Simulink and xPCTarget for performing a series connection test of the D/A conversion card and the A/D conversion card which are connected in series in a semi-physical simulation control system and obtaining accurate input and output test data by using pure digital signal input and storage process; establishing an equivalent model of the D/A conversion card and the A/D conversion card connected in series on the basis of the principle of equivalent model transformation, and identifying the equivalent model by using the input and output test data acquired under the test platform, including obtaining a constant drift and a quantization error of the D/A conversion card and the A/D conversion card by means of curve fitting and normal distribution verification, and obtaining a conversion time delay model on the basis of prediction error minimization.The method of the present invention improves the performance of the control system by using the equivalent model to replace the D/A conversion card and the A/D conversion card and using an off-line design control algorithm.

Description

A/D and D/A conversion card identification method based on the equivalent model conversion

Technical field

What the present invention relates to is the A/D and D/A conversion card identification method in a kind of industrial control technology field, specifically is a kind of A/D and D/A conversion card identification method based on the equivalent model conversion.

Background technology

In the industrial control system design process, a semi-physical simulation control system has comprised analog-to-digital conversion card, digital-to-analog conversion card, signal-processing board, controller, driving circuit, controlled device and other monitoring units usually.In order to obtain reliable control performance, need carry out mathematical modeling and emulation to the semi physical control system.In system modelling, often ignore analog to digital conversion and digital-to-analog conversion part or only they are regarded as a gain link.Yet according to digital-to-analog conversion and analog-to-digital ultimate principle, signal conversion process not only can produce constant value drift and quantization error, and can produce transfer delay, promptly signal by digital-to-analogue and analog to digital conversion after, its phase place and amplitude characteristic will change.When digital-to-analog conversion card that adopts in the control system and analog-to-digital conversion card poor-performing, can produce bigger influence to control signal.For accurate semi-physical simulation control system, produce very big departure, even may cause control system to be dispersed especially.In order to improve the performance of semi-physical simulation control system, need logarithmic mode and analog-to-digital conversion card to carry out mathematical modeling.

Find through literature search prior art, Han Fengtian " becomes structure and works the dc static supporting system research of propping up with the rigidity compensation " in (in September, 2002 60-64 page or leaf) at Tsing-Hua University's PhD dissertation, model logarithmic mode and analog-digital conversion process that employing has time-delay and zero-order holder characteristic are similar to, wherein time delay process is represented the time that analog to digital conversion and digital-to-analog conversion consume, zero-order holder has been described the process that simulating signal keeps, and will be similar to model and bring closed-loop control system redesign controller into, improve the performance of control system.Because time constant all is similar in the model, often can not react the transfer delay of actual analog to digital conversion and digital-to-analog conversion card, so the accuracy of this model is not very high.And for multichannel digital-to-analog conversion card and analog-to-digital conversion card, the transfer delay of each passage can there are differences, and does not provide this species diversity usually in the corresponding handbook.In addition, produce reason although quantization error has been discussed in the document, and provide the method that reduces quantization error, do not mention the influence of constant value drift.In fact for digital-to-analog conversion card and analog-to-digital conversion card, constant value drift has bigger influence than quantizing error to control system stability, and it not only can reduce the control system performance, even can cause control system to be dispersed.

Summary of the invention

The present invention is directed to the problem that prior art exists, propose a kind of A/D and D/A conversion card identification method based on the equivalent model conversion.According to semi-physical simulation control system characteristics, with the unified identification that is together in series of digital-to-analog conversion card and analog-to-digital conversion card.Utilize Simulink (the modularization simulation modeling platform of Mai Si Volco Inc exploitation) and xPCTarget (the real-time simulation modeling tool case of Mai Si Volco Inc exploitation) to set up digital-to-analog conversion card and analog-to-digital conversion card test platform.Utilize test data, the equivalent model of logarithmic mode transition card and analog-to-digital conversion card carries out identification.This equivalence model has comprised transfer delay, constant value drift and quantization error, can accurately simulate the operating characteristic after digital-to-analog conversion card and analog-to-digital conversion card are connected.In the semi-physical simulation Control System Design, the equivalent model that control engineering teacher can adopt identification method to obtain substitutes digital-to-analogue transition card and analog-to-digital conversion card, sets up the realistic model of control system.Further can utilize various optimized Algorithm redesign controllers, improve the performance of control system.

The present invention is achieved by the following technical solutions, the present invention includes following steps:

The first step, adopt Simulink and xPCTarget to set up the test platform of a digital-to-analogue transition card and analog-to-digital conversion card, be used for the series connection test of semi-physical simulation digital-to-analog conversion card and analog-to-digital conversion card, signal input and storage by the pure digi-tal formula obtain input/output test data accurately;

Second step, based on equivalent model conversion principle, set up the equivalent model after digital-to-analog conversion card and analog-to-digital conversion card are connected, this model has comprised constant value drift, quantization error and transfer delay.Utilize the input/output test data of under test platform, gathering then, equivalent model is carried out identification, comprise constant value drift identification, quantization error identification and transfer delay identification, wherein adopt curve fitting and normal distribution proof method to obtain the constant value drift and the quantization error of digital-to-analog conversion card and analog-to-digital conversion card, and based on the minimized method acquisition of predicated error transfer delay model, carry out the equivalent model checking at last, finish whole identification process.

The described test platform of setting up digital-to-analog conversion card and analog-to-digital conversion card, step is as follows:

1. software is installed: test platform is based on that main frame-target machine pattern sets up, and therefore needs two PCs.A main frame is used for modelling, code generation and data analysis; A target machine machine is used for test model real time execution and data acquisition, and wherein the target machine machine can be ordinary PC, PC104 or Industry Control plate.The Matlab development environment is installed on main frame, comprise Simulink, xPCTarget, Real Time Workshop (the real-time code Core Generator case of Mai Si Volco Inc exploitation), Curve Fitting (the curve fitting tool box of Mai Si Volco Inc exploitation) and System Identification (the System Discrimination tool box of Mai Si Volco Inc exploitation), above tool box can be bought by Mai Si Volco Inc.Utilize the xPCTarget tool box to generate a real time operating system, be installed on the target machine.

2. hardware connects

Main frame is communicated by letter with target machine: based on ICP/IP protocol, by netting twine main frame and target machine are coupled together in LAN (Local Area Network), realize the communication between the two.The code of main frame can download to target machine like this, and the test data of target machine can upload to main frame.

3. digital-to-analog conversion card and analog-to-digital conversion card are installed:, transition card and target machine are coupled together according to the interface shape of transition card.For example transition card is a pci interface, then transition card is inserted the PCI slot of target machine.For model after logarithmic mode transition card and the analog-to-digital conversion card series connection carries out identification, couple together with the simulation output and the analog input channel of lead with the two.

4. test model is set up

Set up digital-to-analog conversion card and analog-to-digital test model under Simulink, this model comprises a standardized digital signal source, digital-to-analog conversion card interface module, analog to digital conversion card interface module and data acquisition module.Usually provide the interface module of multiple transition card in the I/O storehouse of xPCTarget, if there is not the corresponding interface module, the user can simply revise with reference to other transition card interface modules under xPCTarget, sets up the interface module that needs.

5. test data collection:

On main frame, utilize Real Time Workshop tool box that test model is compiled, generate real-time code.Then real-time code is downloaded on the target machine.The user defines working time, sampling period etc. according to demand, carries out real-time simulation then.Data exist in the internal memory of target machine in the simulation process, and emulation must upload on the main frame after finishing.

Described constant value drift identification is meant: deduct reference-input signal with analog-to-digital conversion card in the test data and digital-to-analog conversion card output result under Matlab, obtain the residual values of the two.Utilize Fourier progression that the residual error curve is carried out match, can obtain smooth curve.In order to improve the accuracy of match, simultaneously time that can overspending, adopt eight rank fourier series.

$f\left(x\right)=\frac{a_0}{2}+\underset{n=1}{\overset{8}{\mathrm{\Σ}}}[a_n\cos \left(\mathrm{n\ωx}\right)+b_n\sin \left(\mathrm{n\ωx}\right)]---\left(1\right)$

Here a ₀, a _n, b _nBe Fourier leaf-size class coefficient, ω is a fundamental frequency.Utilize Data Statistics instrument among the Matlab can obtain the average of matched curve.This average is the constant value drift of digital-to-analog conversion card and analog-to-digital conversion card.

Described quantization error identification is meant: on constant value drift identification basis, utilize residual values to deduct matched curve, the difference table registration mould transition card of the two and the quantization error of analog-to-digital conversion card.Need to prove in this error and may comprise a part of circuit noise.Adopt normal distribution method that this part difference distribution character is verified.In the proof procedure, adopt normplot (X) the order picture data profile among the Matlab, wherein X represents the difference data set.If the data Normal Distribution, the figure that obtains is approximately straight line, and (X, alpha) order acquisition difference data is integrated into average and the variance under (1-alpha) % confidence level to utilize normfit then.If obey other distributions, then comprised segment of curve in the figure, then need to adopt other distribution proof method.

Described transfer lag identification is meant: because digital-to-analog conversion card and analog-to-digital conversion card have time-delay and zeroth order retention performance, the transfer delay model that can obtain the two by its corresponding simplified processing is:

$G_{\mathrm{delay}}\left(s\right)=\frac{K(1+\mathrm{as})}{1+\mathrm{bs}}---\left(2\right)$

K wherein, a, b be the parameter to be identified in the representation model respectively.Utilize the SystemIdentification tool box among the Matlab to carry out identification.At first adopt process model discrimination method based on the predicated error minimum; According to the transfer lag model structure, select only to comprise the model of a pole and zero then; The interval of parameter to be identified in the model then is set: K ∈ (0, inf); A ∈ (0, inf); B ∈ (0, inf).The times N of selecting the identification process recurrence to carry out in addition, N is a natural number.

Described equivalent model checking, be meant: the equivalent model that under Simulink, constant value drift, quantization error and transfer lag model group is constituted altogether digital-to-analog conversion card and analog-to-digital conversion card, and equivalent model put into the authentic testing model, the digital-to-analog conversion card that substitutes and the interface module of analog-to-digital conversion card promptly do not have actual digital-to-analog conversion card and analog-to-digital conversion card in the test model.Utilize Real Time Workshop to generate the code of new test model, and download to real time execution on the target machine, after operation is finished new test result is uploaded to main frame.The test result that comprises analog-to-digital conversion card and digital-to-analog conversion card in acquisition test result and the authentic testing model under the new test model is compared, if the mean approximation of the two difference is zero, illustrate that equivalent model can accurately simulate the constant value drift of digital-to-analog conversion card and analog-to-digital conversion card; If the two difference does not have the visible trend item, illustrate that equivalent model can accurately simulate the transfer delay characteristic of digital-to-analog conversion card and analog-to-digital conversion card.

For the equivalent model after logarithmic mode transition card and the analog-to-digital conversion card series connection carries out identification, the present invention has set up a novel test platform based on main frame-target machine pattern, this platform does not need outside reference power supply and high precision measurement equipment, signal input and storage by the pure digi-tal formula, obtain input/output test data accurately, a series of tool boxes that utilization Matlab provides carry out identification to equivalent model.In the semi-physical simulation Control System Design, the equivalent model that control engineering teacher can adopt identification method to obtain substitutes digital-to-analogue transition card and analog-to-digital conversion card, sets up the realistic model of control system like this.Further can utilize various optimized Algorithm redesign controllers, improve the performance of control system.

Description of drawings

Fig. 1 is the digital-to-analog conversion card PCI1720U of the embodiment of the invention and the test platform architecture block diagram of analog-to-digital conversion card PCI1710HG.

Fig. 2 be the embodiment of the invention the sinusoidal reference signal synoptic diagram.

Fig. 3 is the semi-physical simulation control system transport function synoptic diagram in the embodiment of the invention;

Wherein: be ssystem transfer function before the equivalent transformation (a), (b) be ssystem transfer function behind the equivalent transformation.

Fig. 4 is the four-way curve fitting synoptic diagram that the employing Fouier Series Method of the embodiment of the invention obtains;

Wherein: (a) being the curve fitting of passage 1, (b) is the curve fitting of passage 2, (c) is the curve fitting of passage 3, (d) is the curve fitting of passage 4; (a)～(d) last figure all represents curve fitting, and dotted line is represented actual residual error, and solid line is represented matched curve; (a)～(d) figure below is all represented the difference between the actual residual sum matched curve.

Fig. 5 is the quantization error distribution proof diagram that the employing normal distribution method of the embodiment of the invention obtains;

Wherein: (a) being the quantization error distribution of passage 1, (b) is that the quantization error of passage 2 distributes, and (c) is that the quantization error of passage 3 distributes, and (d) quantization error of passage 4 distributes.

The output that Fig. 6 comprises the new test model of digital-to-analog conversion card and analog-to-digital conversion card equivalent model and actual test model for the embodiment of the invention is the difference synoptic diagram as a result;

Wherein: (a) being the difference of passage 1, (b) is the difference of passage 2, (c) is the difference of passage 3, (d) is the difference of passage 4.

Embodiment

What set forth below in conjunction with accompanying drawing is the good Model Distinguish effect that a embodiment that the present invention provides shows.It may be noted that, the present invention is not only limited to following embodiment, present embodiment is implemented not departing from essence spirit of the present invention and do not exceed under the prerequisite of the related scope of flesh and blood of the present invention, provide A/D and D/A conversion discrimination method based on the equivalent model conversion, be applicable to various dissimilar digital-to-analog conversion card and analog-to-digital conversion cards, can be widely used in the semi-physical simulation control procedure in the industries such as Aero-Space, automobile, machinery.

Embodiment: at the digital-to-analog conversion card PCI1720U that grinds magnificent company and the analog-to-digital conversion card PCI1710HG that often adopt in the semi-physical simulation control system, employing is introduced concrete implementation step based on the A/D and D/A conversion card identification method of equivalent model conversion.

1). software is installed:

Present embodiment is based on main frame-target machine pattern, and as main frame, a PC of being furnished with floppy drive is as target machine with a PC.The Matlab development environment is installed on main frame, is comprised tool boxes such as Simulink, xPCTarget, Real Time Workshop, Curve Fitting and System Identification.Generate real time operating system with the xPCTarget tool box and be used to start target machine.By netting twine main frame and target machine are distinguished access to LAN then.

2). hardware connects:

PCI digital-to-analog conversion card that adopts among the embodiment and PCI analog-to-digital conversion card are respectively PCI1720U and the PCI1710HG of Advantech.Two transition cards all are based on pci bus, can directly they be inserted on two PCI slots of target machine, then adopt cable separately that transition card and their terminal block are coupled together.For four road I/O passages are carried out identification, couple together with four four analog input mouths of simulating delivery outlet and analog input terminal strip of four leads with the analog output daughter board.In addition, target machine and main frame are connected respectively on the router, carry out communication based on ICP/IP protocol between target machine and the main frame by the RJ45 netting twine.The test platform that makes up as shown in Figure 1.

3). set up test model:

Set up the test model of analog-to-digital conversion card and digital-to-analog conversion under Simulink, this model comprises an amplitude 5V, the sinusoidal reference signal of frequency 100HZ, and this signal is as the input of four passages of PCI1720U interface module in the test model.Connect by external hardware, the four-way analog output signal of digital-to-analog conversion card is then realized digital signal acquiring by PCI1710HG interface module in the test model as the four-way analog input signal of analog-to-digital conversion card.

4). test data collection:

On main frame, utilize Real Time Workshop tool box that test model is compiled, generate real-time code.Then download to real-time code on the target machine and carry out real-time simulation.Setting the real time execution time in the experiment is that 4000s, sampling period are 0.002s etc., gathers 2e altogether ⁶Individual sample.Owing to comprised model discretize process during the test model compiling, and the discretize time of setting in the test model discretize process is 1e ^-8S, so sinusoidal signal only moved 0.02s, as shown in Figure 2.

5). set up the equivalent model of digital-to-analog conversion card and analog-to-digital conversion card based on equivalent transformation

For the validity of equivalent model in the semi-physical simulation control system of verifying PCI1720U and PCI1710HG, set up the model of the semi-physical simulation control system of classics.As shown in Figure 3.C (s) wherein: controller transfer function; G _D/A(s): the equivalent transfer function of digital-to-analog conversion card PCI1720U; K: the equivalent link of power driving circuit, generally take the constant gain amplifier form; F (s): the equivalent transfer function of signal processing circuit; P (s): the equivalent transfer function of controlled device; G _A/D(s): the equivalent transfer function of analog-to-digital conversion card PCI1710HG.

According to Fig. 3 (a), can obtain the transport function of closed-loop control system:

$T_C\left(s\right)=\frac{C\left(s\right)\·G_{D/A}\left(s\right)\·k\·P\left(s\right)\·F\left(s\right)\·G_{A/D}\left(s\right)}{1+C\left(s\right)\·G_{D/A}\left(s\right)\·k\·P\left(s\right)\·F\left(s\right)\·G_{A/D}\left(s\right)}---\left(1\right)$

In Fig. 3 (b), owing to comprised the series connection model G (s) of PCI1720U and PCI1710HG, so the transport function of its closed-loop control system can be written as:

$T_C^{\′}=\frac{C\left(s\right)\·G\left(s\right)\·k\·P\left(s\right)\·F\left(s\right)}{1+C\left(s\right)\·G\left(s\right)\·k\·P\left(s\right)\·F\left(s\right)}---\left(2\right)$

G (s)=G _D/A(s) G _A/D(s) substitution formula (2), T ' as can be seen _C(s)=T _C(s).Therefore the equivalent model after PCI1720U and the PCI1710HG series connection can not exert an influence to the stability of semi-physical simulation control system, can unify identification to the equivalent model G (s) after the series connection.This equivalence model comprises constant value drift, quantization error and transfer lag.The test data of utilizing step 1-4 to obtain, the equivalent model to PCI1720U and PCI1710HG under the Matlab of main frame environment carries out identification.

5). the constant value drift identification:

At first deduct sinusoidal reference signal from four passage output results, obtain the residual values of four-way, shown in the last figure dotted line of every passage among Fig. 4, curve has comprised the phase deviation that constant value drift, quantizing noise and transfer delay cause as can be seen.Utilize eight rank Fourier progression that the residual error curve is carried out match, four passages of acquisition

Matched curve is shown in the last figure solid line of every passage among Fig. 4.Utilize that the data statistics instrument can calculate the average of matched curve among the Matlab.This average is the constant value drift of digital-to-analog conversion card PCI1720U and analog-to-digital conversion card PCI1710HG.Four passage constant value drifts are as shown in table 1.

Transformed error after table 1. digital-to-analog conversion card and the analog-to-digital conversion card series connection

6). the quantization error identification:

On the basis of step 5, residual values and matched curve data are subtracted each other, obtain the quantization error that digital-to-analogue in the transfer process transforms card and analog-to-digital conversion card, shown in the figure below of (a)-(d) among Fig. 4.Need to prove and comprise a part of circuit noise in this error.Adopt normal distribution method that this part difference is verified.In the proof procedure, adopt normplot (X) the order picture data profile among the Matlab, wherein X represents the difference data set.As shown in Figure 5, the distribution proof diagram of ("+" expression) expression quantization error among the figure, the figure of four passages is approximately straight line as can be seen, and this explanation quantization error is approximately normal distribution.(X, alpha) order obtains average and the variance of difference set under (1-alpha) % confidence level to utilize normfit then.Because the average of quantization error approaches zero, can ignore, and only calculates variance yields here.As shown in table 1.12 of the D/A resolution of analog-to-digital conversion card PCI1710HG in the experiment, input range [10V, 10V], gain 0.5; 12 of the A/D resolution of digital-to-analog conversion card PCI20U, input range [10V, 10V], gain is 0.5.For the PCI1710HG and the PCI1720U of the type of rounding up, the two quantization error is

Consider in the transfer process quantization error irrelevance of the two, the quantization error after their series connection should be 0.0024V.Actual quantization error ratio ideal value (0.0024V) is big as can be seen, and this is because the quantization error circuit noise that superposeed in the transfer process.Notice that the quantization error of being mentioned all refers to its standard deviation here.

7). the transfer lag identification

From the working mechanism of PCI1720U and PCI1710HG, all there is retention performance its inside.The zero-order holder characteristic of the two is used (a) and (b) expression in the formula (3) respectively.

$\left.\begin{array}{c}{\stackrel{\‾}{G}}_{D/A}\left(s\right)=\frac{1-e^{-T_{1}s}}{s}\\ {\stackrel{\‾}{G}}_{A/D}\left(s\right)=\frac{1-e^{-T_{2}s}}{s}\end{array}\right\}---\left(2\right)$

In conjunction with conversion delaing time constant separately, the complete model structure of PCI1720U and PCI1710HG can be used (a) and (b) expression in the formula (4) respectively:

$\left.\begin{array}{c}{G}_{D/A}\left(s\right)=e^{-T_{D/1}s}\·\frac{1-e^{-T_{1}s}}{s},\left(a\right)\\ G_{A/D}\left(s\right)=e^{-T_{A/D}s}\frac{1-e^{-T_{2}s}}{s},\left(b\right)\end{array}\right\}---\left(4\right)$

This model structure has embodied the transfer delay characteristic of analog to digital conversion and digital-to-analog conversion integrated circuit board on the principle, but parameter wherein can not directly obtain.In order to improve the accuracy of identification, need simplify model.Here at first adopt the second order Taylor series to come the simplified model structure.The reduced form of digital-to-analog conversion card is as follows:

$G_{D/A}\left(s\right)={\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2008100416670E00011.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\&CenterDot;e^{-T_{D/A}s}\&CenterDot;\frac{1-e^{-T_{1}s}}{s}=\frac{k(e^{T_{1}s}-1)}{s{\mathrm{<figure-callout\; id="1"\; label="e\; T"\; filenames="H2008100416670E00011.png"\; state="\{\{state\}\}">e</figure-callout>}}^{T_{}^{}}}\&ap;\frac{k_1(1+T_{1}s+\frac{{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="H2008100416670E00011.png"\; state="\{\{state\}\}">T</figure-callout>}}_1^2{s}^2}{2}-1)}{s(1+{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="H2008100416670E00011.png"\; state="\{\{state\}\}">T</figure-callout>}}_1^{\&prime;}s+\frac{{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="H2008100416670E00011.png"\; state="\{\{state\}\}">T</figure-callout>}}_1^{\&prime;2}{s}^2}{2})}---\left(5\right)$

T ' in the formula (5) ₁=T ₁+ T _D/A, k ₁Be the digital-to-analog conversion gain.

Ignore the second order term in the denominator, further arrangement can get:

$G_{D/A}\left(s\right)\&ap;\frac{k_1{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="H2008100416670E00011.png"\; state="\{\{state\}\}">T</figure-callout>}}_1+\frac{k_1{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="H2008100416670E00011.png"\; state="\{\{state\}\}">T</figure-callout>}}_1^{2}s}{2}}{1+{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="H2008100416670E00011.png"\; state="\{\{state\}\}">T</figure-callout>}}_1^{\&prime;}s}=\frac{K_{D/A}(1+a_{1}s)}{1+b_{1}s}---\left(6\right)$

A wherein ₁, b ₁, K _D/AIt is the model coefficient of PCI1720U.

By similar abbreviation, can obtain the model of digital-to-analog conversion card PCI1710HG:

$G_{A/D}\left(s\right)\&ap;\frac{K_{A/D}(1+a_{2}s)}{1+b_{2}s}---\left(7\right)$

A wherein ₂, b ₂, K _A/DIt is the model coefficient of PCI1710HG.

According to the series characteristic of PCI1720U and PCI1710HG, ignore the transfer delay model that can get the two after the second order term:

$G_{\mathrm{delay}}\left(s\right)=G_{D/A}\left(s\right)G_{A/D}\left(s\right)\&ap;\frac{K_{D/A}(1+a_{1}s)}{1+b_{1}s}\frac{K_{A/D}(1+a_{2}s)}{1+b_{2}s}\&ap;\frac{K(1+\mathrm{as})}{1+\mathrm{bs}}---\left(8\right)$

K=K in the formula (8) ₁K ₂, a=a ₁+ a ₂, b=b ₁+ b ₂

As can be seen, the transfer delay characteristic of PCI1720U and PCI1710HG can be by only comprising the model representation of a pole and zero.

On the basis of step 5, from test data, deduct constant value drift, then sinusoidal reference signal and test data are gathered as the inputoutput data of discrimination method.Utilize the SystemIdentification tool box among the Matlab to carry out identification.At first adopt process model discrimination method based on the predicated error minimum; According to the transfer lag model structure, select only to comprise the model of a pole and zero then; The interval of parameter to be identified in the model then is set: K ∈ (0, inf); A ∈ (0, inf); B ∈ (0, inf)

The identification result of four passages of formula 9 expressions.

$\left.\begin{array}{c}{G}_1\left(s\right)=\frac{0.99405(1+0.0053732s)}{1+0.0053731s}\\ G_2\left(s\right)=\frac{0.9981(1+0.022858s)}{1+0.022866s}\\ G_3\left(s\right)=\frac{0.99684(1+0.0041722s)}{1+0.0041722s}\\ G_4\left(s\right)=\frac{0.99539(1+0.29686s)}{1+0.29612s}\end{array}\right\}---\left(9\right)$

For the simplified model structure of verifying that second portion proposes, other several model structures are used to compare.Model structure in the table 2 is expressed as follows respectively:

The identification accuracy rate (%) of the different model structures of table 2.

P1D: comprise a limit and pure delay link

P2D: comprise two limits and pure delay link

P1DZ: comprise a limit, zero point and pure delay link

P1Z: comprise a limit, zero point and pure delay link

Table 2 has provided and has adopted the PEM method to carry out the four-way identification result that obtains after 20 recurrence.As can be seen, in these four kinds of model structures, adopt the P1Z model structure can obtain the highest identification accuracy rate, illustrate that the P1Z model structure is effective.Relative other several structures in addition, the P1Z model structure is a kind of fairly simple linear model, in the design of control system system modelling, model that can simplified control system makes things convenient for system modelling and emulation.

8). set up the equivalent model after PCI1720U and PCI1710HG connect

Under Simulink, adopt a constant module to represent the constant value drift of PCI1720U and PCI1710HG; Employing normal distribution noise module is represented the quantizing noise in the two conversion process; Employing comprises the transport function of a pole and zero and represents the transfer lag model; The simulating signal input range of considering PCI1710HG in the experiment simultaneously is [10V, 10V], and the output area of PCI1720U is [10V, 10V], therefore need increase saturation element at the input and output side of identification model.In the semi-physical simulation Control System Design, control engineering teacher can adopt equivalent model to substitute digital-to-analogue transition card and analog-to-digital conversion card, sets up the realistic model of control system.Further can utilize various optimized Algorithm redesign controllers, improve the performance of control system.。

9). the checking equivalent model

Under Simulink, utilize equivalent model to substitute PCI1720U and PCI1710HG, build up a new test model.Utilize Real Time Workshop to generate real-time code, and download to real time execution on the target machine, after operation is finished test result is uploaded to main frame.The test result that the test result that obtains under the new test model and actual test model are obtained relatively, as shown in Figure 6.The mean approximation of the two difference is zero as can be seen, illustrates that equivalent model can accurately simulate the constant value drift of digital-to-analog conversion card and analog-to-digital conversion card; The two difference does not have the visible trend item yet, illustrates that equivalent model can accurately simulate the transfer delay characteristic of digital-to-analog conversion card and analog-to-digital conversion card.The reason that difference produces between the two: because these two test models do not belong to same test process, the error in the new test model and the quantization error of actual test model do not have correlativity.Variance computing formula according to two uncorrelated signals:

D(X-Y)＝D(X)+D(Y) (10)

X, Y represent respectively to obtain data sequence in two test processs, and when the two subtracted each other, their noise variance can be folded mutually.

By present embodiment as can be seen, the transfer lag equivalent model structure after adopt simplifying, the identification rate of accuracy reached to 99.88% of four passages, the error that last identification result almost causes without any constant value drift and transfer lag.The A/D and D/A conversion discrimination method based on the equivalent model conversion is adopted in this explanation, has picked out the equivalent model of PCI1720U and PCI1710HG accurately.

Claims (6)

1. A/D and D/A conversion card identification method based on the equivalent model conversion is characterized in that may further comprise the steps:

The first step, adopt Simulink and xPCTarget to set up the test platform of a digital-to-analogue transition card and analog-to-digital conversion card, be used for the series connection test of semi-physical simulation digital-to-analog conversion card and analog-to-digital conversion card, signal input and storage by the pure digi-tal formula obtain input/output test data accurately;

Second step, based on equivalent model conversion principle, set up the equivalent model after digital-to-analog conversion card and analog-to-digital conversion card are connected, this model has comprised constant value drift, quantization error and transfer delay, utilize the input/output test data of under test platform, gathering that equivalent model is carried out identification then, comprise the constant value drift identification, quantization error identification and transfer delay identification, wherein adopt curve fitting and normal distribution proof method to obtain the constant value drift and the quantization error of digital-to-analog conversion card and analog-to-digital conversion card, and based on the minimized method acquisition of predicated error transfer delay model, carry out the equivalent model checking at last, finish whole identification process;

Described constant value drift identification is meant: deduct reference-input signal with analog-to-digital conversion card in the test data and digital-to-analog conversion card output result under Matlab, obtain the residual values of the two, utilize Fourier progression that the residual error curve is carried out match:

$f\left(x\right)=\frac{a_0}{2}+\underset{n=1}{\overset{8}{\mathrm{\&Sigma;}}}[a_n\cos \left(\mathrm{n\&omega;x}\right)+b_n\sin \left(\mathrm{n\&omega;x}\right)]---\left(1\right)$

Wherein: a ₀, a _n, b _nBe Fourier leaf-size class coefficient, ω is a fundamental frequency, utilizes Data Statistics instrument among the Matlab can obtain the average of matched curve, and this average is the constant value drift of digital-to-analog conversion card and analog-to-digital conversion card;

Described quantization error identification is meant: on constant value drift identification basis, utilize residual values to deduct matched curve, the difference table registration mould transition card of the two and the quantization error of analog-to-digital conversion card;

Described transfer lag identification is meant: the transfer delay model of digital-to-analog conversion card and analog-to-digital conversion card is:

$G_{\mathrm{delay}}\left(s\right)=\frac{K(1+\mathrm{as})}{1+\mathrm{bs}}---\left(2\right)$

Wherein: K, a, the parameter to be identified in the b difference representation model, K ∈ (0, inf); A ∈ (0, inf); B ∈ (0, inf);

Described equivalent model checking, be meant: the equivalent model that under Simulink, constant value drift, quantization error and transfer lag model group is constituted altogether digital-to-analog conversion card and analog-to-digital conversion card, and equivalent model put into the authentic testing model, the digital-to-analog conversion card that substitutes and the interface module of analog-to-digital conversion card promptly do not have actual digital-to-analog conversion card and analog-to-digital conversion card in the test model.

2. the A/D and D/A conversion card identification method based on the equivalent model conversion according to claim 1 is characterized in that, the described test platform of setting up digital-to-analog conversion card and analog-to-digital conversion card, and step is as follows:

1. test platform is based on main frame-target machine pattern foundation, adopt two PCs, a main frame is used for modelling, code generation and data analysis, another target machine machine is used for test model real time execution and data acquisition, the Matlab development environment is installed on main frame, comprise Simulink, xPCTarget, Real TimeWorkshop, Curve Fitting and System Identification, utilize the xPCTarget tool box to generate a real time operating system, be installed on the target machine;

2. based on ICP/IP protocol, in LAN (Local Area Network) main frame and target machine are coupled together, realize the communication of the two, the code of main frame can download to target machine like this, and the test data of target machine can upload to main frame;

3. according to the interface shape of transition card, transition card and target machine are coupled together,, couple together with the simulation output and the analog input channel of lead with the two for model after logarithmic mode transition card and the analog-to-digital conversion card series connection carries out identification;

4. set up digital-to-analog conversion card and analog-to-digital test model under Simulink, this model comprises a standardized digital signal source, digital-to-analog conversion card interface module, analog to digital conversion card interface module and data acquisition module;

5. on main frame, utilize Real Time Workshop tool box that test model is compiled, generate real-time code, then real-time code is downloaded on the target machine, the user defines working time, sampling period according to demand, carry out real-time simulation then, data exist in the internal memory of target machine in the simulation process, and emulation must upload on the main frame after finishing.

3. the A/D and D/A conversion card identification method based on the equivalent model conversion according to claim 1, it is characterized in that, described constant value drift identification, be meant: under Matlab, deduct reference-input signal with analog-to-digital conversion card in the test data and digital-to-analog conversion card output result, obtain the residual values of the two, utilize Fourier progression that the residual error curve is carried out match and obtain smooth curve, adopt eight rank fourier series to improve the accuracy of match:

$f\left(x\right)=\frac{a_0}{2}+\underset{n=1}{\overset{8}{\mathrm{\&Sigma;}}}[a_n\cos \left(\mathrm{n\&omega;x}\right)+b_n\sin \left(\mathrm{n\&omega;x}\right)]$

Here a ₀, a _n, b _nBe Fourier leaf-size class coefficient, ω is a fundamental frequency, utilizes the average of Data Statistics instrument acquisition matched curve among the Matlab, and this average is the constant value drift of digital-to-analog conversion card and analog-to-digital conversion card.

4. the A/D and D/A conversion card identification method based on the equivalent model conversion according to claim 1, it is characterized in that, described quantization error identification, be meant: on constant value drift identification basis, utilize residual values to deduct matched curve, the difference table registration mould transition card of the two and the quantization error of analog-to-digital conversion card, may comprise a part of circuit noise in this error, adopt normal distribution method that this part difference distribution character is verified, in the proof procedure, adopt normplot (X) the order picture data profile among the Matlab, wherein X represents the difference data set, if the data Normal Distribution, the figure that obtains is approximately straight line, (X, alpha) order acquisition difference data is integrated into average and the variance under (1-alpha) % confidence level to utilize normfit then.

5. the A/D and D/A conversion card identification method based on the equivalent model conversion according to claim 1, it is characterized in that, described transfer lag identification is meant: digital-to-analog conversion card and analog-to-digital conversion card have time-delay and zeroth order retention performance, handle the transfer delay model that obtains the two by simplification to be:

$G_{\mathrm{delay}}\left(s\right)=\frac{K(1+\mathrm{as})}{1+\mathrm{bs}}$

K wherein, a, parameter to be identified in the b difference representation model, utilize the SystemIdentification tool box among the Matlab to carry out identification: at first to adopt process model discrimination method based on the predicated error minimum, then according to the transfer lag model structure, select only to comprise the model of a pole and zero, the interval of parameter to be identified in the model then is set: K ∈ (0, inf); A ∈ (0, inf); B ∈ (0, inf), the times N of selecting the identification process recurrence to carry out, N is a natural number.

6. the A/D and D/A conversion card identification method based on the equivalent model conversion according to claim 1, it is characterized in that, described equivalent model checking, be meant: under Simulink with constant value drift, quantization error and transfer lag model group constitute the equivalent model of digital-to-analog conversion card and analog-to-digital conversion card altogether, and equivalent model put into the authentic testing model, the digital-to-analog conversion card that substitutes and the interface module of analog-to-digital conversion card, be not have actual digital-to-analog conversion card and analog-to-digital conversion card in the test model, utilize Real Time Workshop to generate the code of new test model, and download to real time execution on the target machine, after operation is finished new test result is uploaded to main frame, the test result that comprises analog-to-digital conversion card and digital-to-analog conversion card in acquisition test result and the authentic testing model under the new test model is compared, if the mean approximation of the two difference is zero, illustrate that equivalent model can accurately simulate the constant value drift of digital-to-analog conversion card and analog-to-digital conversion card; If the two difference does not have the visible trend item, illustrate that equivalent model can accurately simulate the transfer delay characteristic of digital-to-analog conversion card and analog-to-digital conversion card.

Images