CN105827554A - Optimization method and apparatus of matched resistance of flexray bus node - Google Patents

Abstract

The invention, which belongs to the technical field of data bus communication, relates to an optimization method and apparatus of matched resistance of a flexray bus node. According to the invention, an excitation signal is applied to a flexray bus; a voltage signal of a flexray bus node is measured and calculated; on the basis of the voltage signal, an optimal matched resistance value of the flexray bus is obtained by combining a distribution parameter model of the flexray bus. With the method and apparatus, the quality of signal communication of the flexray bus can be improved; the error rate in a data communication process can be reduced; and stability and reliability of flexray bus data communication can be guaranteed.

Description

A kind of optimization method and device of FlexRay bus node build-out resistor

Technical field

The invention belongs to data bus communication technical field, relate to the optimization method and device of a kind of FlexRay bus node build-out resistor.

Background technology

Automotive electronics has become a staple market of automobile industry, and the focus of Automobile Electronic Industry maximum is exactly networking.Automobile of today is a portable massaging device already, by in-vehicle network system, can receive, sends and process substantial amounts of data, and some situation is made the reaction of necessity.The development trend of future automobile necessarily automaticity is more and more higher, makes automobile safer, more reliable, more comfortable, it means that to use more sensor, actuating device and electronic control unit in car, and this also will propose higher requirement to In-vehicle networking.For the demand for development of future automobile In-vehicle networking, FlexRay arises at the historic moment.FlexRay is concerned with some core demands of current automobile industry, and including faster data rate, more flexible data communication, more fully topology select and fault-tolerant computing etc..The appearance of FlexRay, compensate for existing bus protocol and applies at automotive line Ore-controlling Role or fault-tolerance and transfer rate the lowest deficiency during with safety-related system, and will progressively replace CAN and become the automobile bus of a new generation.

Requirement to FlexRay is, provides reliably, transmits with very efficient data in real time between electrically and mechanically electronic component.The peak data transfer rate of each passage of FlexRay bus is 10MBit/s, and therefore FlexRay is a system very at a high speed.But, if the impedance matching of FlexRay bus does not design, then can cause data traffic signals Quality Down, the too high bit error rate will cause whole FlexRay bus system communication efficiency significantly to decline, and even result in whole FlexRay bus cisco unity malfunction.

In sum, it is badly in need of invention one and can improve FlexRay bus signals communication quality, reduce the optimization method of the impedance matching of the bit error rate, to improve the reliability and stability of FlexRay bus comprehensively.

Summary of the invention

In view of this, it is an object of the invention to provide the optimization method and device of a kind of FlexRay bus node build-out resistor, by this device, FlexRay bus is applied pumping signal, by measuring and calculate the voltage signal of FlexRay bus node, and combine the distributed parameter model of FlexRay bus, it is thus achieved that most preferably mate impedance about FlexRay bus.The method can be effectively improved FlexRay bus signals communication quality, reduces the bit error rate in data communication process, it is ensured that the Stability and dependability of FlexRay bus data communication.

For reaching above-mentioned purpose, the present invention provides following technical scheme:

The optimization method of a kind of FlexRay bus node build-out resistor, comprises the following steps:

S1: the Chirp code signal source of 1M～10MHz is encouraged successively each node of FlexRay bus；

S2: when Chirp code signal source excitation certain node of FlexRay bus, speed A/D converter, under the effect of synchronizing signal SYNC, gathers the differential signal of other all FlexRay bus nodes successively；

S3: according to actual FlexRay physical bus Node distribution, build the distributed parameter model of FlexRay bus；

S4: by the data of actual acquisition, substitute into the distributed parameter model of FlexRay bus, calculate the terminal build-out resistor obtaining FlexRay each node of bus.

Further, in step sl, specifically include:

The Chirp code signal source of S11: described 1M～10MHz, the expression formula of this signal source is:

$e\left(t\right)=cos\left(\frac{\mathrm{\π}B}{T}{t}^2\right)---\left(1\right)$

Wherein the bandwidth B of Chirp code signal source is 10MHz, duration T be 10uS, t be time variable, cos (.) is cosine function；

S12: when the Chirp code signal source output drive FlexRay bus node of 1M～10MHz, export corresponding synchronizing signal SYNC.

Further, in step s 4, specifically include:

S41: according to the characteristic of Chirp code signal source, substitutes into the measurement parameter of different FlexRay node respectively, by below equation (2) be calculated 1MHz, 2MHz, 3MHz ..., 10MHz amount to 10 groups of a, b numerical value: [a₁,b₁], [a₂,b₂] ..., [a₁₀,b₁₀]；

$U_{oc}=\frac{1}{2}{U}^2(\cosh 2bL+cos2aL)---\left(2\right)$

In formula (2), U_ocFor the voltage signal at FlexRay bus node, U is the Chirp code excited signal of 1MHz～10MHz, and L is the distance of FlexRay bus node distance pumping signal, and cosh (.) is hyperbolic cosine function, and cos (.) is cosine function；

S42: according to formula (3), substitutes into a, b numerical value of 10 groups respectively: [a₁,b₁], [a₂,b₂] ..., [a₁₀,b₁₀], it is calculated 10 groups of R₀、L₀、C₀、G₀Distributed constant_,It is designated as [R respectively₀₁,L₀₁,C₀₁,G₀₁], [R₀₂,L₀₂,C₀₂,G₀₂] ..., [R₀₁₀,L₀₁₀,C₀₁₀,G₀₁₀]；

$\left\{\begin{array}{c}a=2\mathrm{\π}f\sqrt{L_0{C}_0}\[1+\frac{1}{32{\mathrm{\π}}^2{f}^2}{(\frac{R_0}{L_0}-\frac{G_0}{C_0})}^2\]\\ b=(\frac{R_0}{2}\sqrt{\frac{C_0}{L_0}}+\frac{G_0}{2}\sqrt{\frac{C_0}{L_0}})(1-\frac{1}{32{\mathrm{\π}}^2{f}^2}{\left(\frac{R_0}{L_0}-\frac{G_0}{C_0}\right)}^2)\end{array}\right.---\left(3\right)$

In formula (3), f is the frequency that a, b numerical value is corresponding, R₀For unit line segment resistance, L₀For unit line segment inductance, C₀Differential coupling electric capacity, G for unit line segment₀Leakage conductance for unit difference line segment；

S43: substitute into [a respectively₁,b₁]、[a₂,b₂] and corresponding frequency f, set up equation group by formula (3), solve i.e. available [R₀₁,L₀₁,C₀₁,G₀₁], then substitute into [a₂,b₂], [a₃,b₃], solve i.e. available [R₀₂,L₀₂,C₀₂,G₀₂], by that analogy, finally substitute into [a₁₀,b₁₀], [a₁,b₁], solve i.e. available [R₀₁₀,L₀₁₀,C₀₁₀,G₀₁₀]；

S44: according to the communication frequency f of FlexRay bus, substitute into the R that respective communication frequency is corresponding₀、L₀、C₀、G₀Parameter, the peripheral circuit equivalent predigesting of FlexRay bus node is two-port network model by the application Dai Weinan principle of equal effects, thus is calculated the equivalent matched resistance of FlexRay bus node.

Present invention also offers the optimization device of a kind of FlexRay bus node build-out resistor, including speed A/D converter, high-speed DAC transducer, high speed amplifier, field programmable logic device FPGA and microcontroller STM32F407；

The Chirp code signal of field programmable logic device FPGA output 1MHz～10MHz of FlexRay bus test device, after high-speed DAC transducer and amplifier drive, as the pumping signal of FlexRay bus, exports synchronizing signal SYNC of Chirp code simultaneously；

Speed A/D converter, under the synchronizing signal SYNC effect of Chirp code, carries out data sampling by high-speed AD controller, and sampled result is placed in the high speed dual port RAM within field programmable logic device FPGA；

Microcontroller STM32F407 reads sampling data results, and the distributed constant completing FlexRay bus in inside calculates and the optimization calculating of node matching resistance.

The beneficial effects of the present invention is: present invention employs a kind of method that FlexRay bus node build-out resistor optimizes, launched by device and have the Chirp code signal of characteristic frequency, the voltage's distribiuting of test FlexRay bus node, physical model in conjunction with FlexRay bus, calculate the distributed constant obtaining FlexRay bus, finally FlexRay bus is simplified by the application Dai Weinan principle of equal effects, thus calculates the equivalent matched impedance resistors obtaining FlexRay bus.The method can obtain the build-out resistor of accurate FlexRay bus node, effectively improves the traditional method rule of thumb selecting build-out resistor, thus improves the communication quality of FlexRay bus, the problem such as bit error rate significantly reducing FlexRay bus.

Accompanying drawing explanation

In order to make the purpose of the present invention, technical scheme and beneficial effect clearer, the present invention provides drawings described below to illustrate:

Fig. 1 is the schematic flow sheet of the method for the invention；

Fig. 2 is the distributed parameter model of FlexRay bus；

Fig. 3 is that FlexRay bus distributed constant tests schematic diagram.

Detailed description of the invention

Below in conjunction with accompanying drawing, the preferred embodiments of the present invention are described in detail.

Fig. 1 is the schematic flow sheet of the method for the invention, as it can be seen, during FlexRay bus node build-out resistor optimizes, comprise the following steps:

Step one: the Chirp code signal source of 1M～10MHz is encouraged each node of FlexRay bus by test device successively；

The expression formula of the Chirp code signal source of 1M～10MHz used in step one is

$e\left(t\right)=cos\left(\frac{\mathrm{\π}B}{T}{t}^2\right)---\left(1\right)$

Wherein the bandwidth B of Chirp code signal source is 10MHz, duration T be 10uS, t be time variable, cos (.) is cosine function；When the Chirp code signal source output drive FlexRay bus node of 1M～10MHz, export corresponding synchronizing signal SYNC.

Step 2: when the node of Chirp code signal source excitation FlexRay bus, speed A/D converter, under the effect of synchronizing signal SYNC, gathers the differential signal of other all FlexRay bus nodes successively；

Step 3: according to actual FlexRay physical bus Node distribution, build the distributed parameter model of FlexRay bus.Specific practice is according to actual FlexRay physical bus length, material and Node distribution, builds the distributed parameter model of FlexRay bus, R₀For unit line segment resistance, L₀For unit line segment inductance, C₀Differential coupling electric capacity, G for unit line segment₀Leakage conductance for unit difference line segment；Fig. 2 is the distributed parameter model of FlexRay bus.

Step 4: by the data of actual acquisition, substitute into the distributed parameter model of FlexRay bus, calculate the terminal build-out resistor obtaining FlexRay each node of bus.Concrete method is:

1) by below equation (2) be calculated 1MHz, 2MHz, 3MHz ..., 10MHz amount to 10 groups of a, b numerical value: [a₁,b₁], [a₂,b₂] ..., [a₁₀,b₁₀]；

$U_{oc}=\frac{1}{2}{U}^2(\cosh 2bL+cos2aL)---\left(2\right)$

In formula (2), U_ocFor the voltage signal at FlexRay bus node, U is the Chirp code excited signal of 1MHz～10MHz, and L is the distance of FlexRay bus node distance pumping signal, and cosh (.) is hyperbolic cosine function, and cos (.) is cosine function；

2) a, b numerical value of 10 groups: according to formula (3), is substituted into respectively: [a₁,b₁], [a₂,b₂] ..., [a₁₀,b₁₀], it is calculated 10 groups of R₀、L₀、C₀、G₀Distributed constant, be designated as [R respectively₀₁,L₀₁,C₀₁,G₀₁], [R₀₂,L₀₂,C₀₂,G₀₂] ..., [R₀₁₀,L₀₁₀,C₀₁₀,G₀₁₀]；

$\left\{\begin{array}{c}a=2\mathrm{\π}f\sqrt{L_0{C}_0}\[1+\frac{1}{32{\mathrm{\π}}^2{f}^2}{(\frac{R_0}{L_0}-\frac{G_0}{C_0})}^2\]\\ b=(\frac{R_0}{2}\sqrt{\frac{C_0}{L_0}}+\frac{G_0}{2}\sqrt{\frac{C_0}{L_0}})(1-\frac{1}{32{\mathrm{\π}}^2{f}^2}{\left(\frac{R_0}{L_0}-\frac{G_0}{C_0}\right)}^2)\end{array}\right.---\left(3\right)$

In formula (3), f is the frequency that a, b numerical value is corresponding, R₀For unit line segment resistance, L₀For unit line segment inductance, C₀Differential coupling electric capacity, G for unit line segment₀Leakage conductance for unit difference line segment；

3): substitute into [a respectively₁,b₁]、[a₂,b₂] and corresponding frequency f, set up equation group by formula (3), solve i.e. available [R₀₁,L₀₁,C₀₁,G₀₁], then substitute into [a₂,b₂], [a₃,b₃], solve i.e. available [R₀₂,L₀₂,C₀₂,G₀₂], by that analogy, finally substitute into [a₁₀,b₁₀], [a₁,b₁], solve i.e. available [R₀₁₀,L₀₁₀,C₀₁₀,G₀₁₀]；

4): according to the communication frequency f of FlexRay bus, substitute into the R that respective communication frequency is corresponding₀、L₀、C₀、G₀Parameter, the peripheral circuit equivalent predigesting of FlexRay bus node is two-port network model by the application Dai Weinan principle of equal effects, thus is calculated the equivalent matched resistance of FlexRay bus node.Fig. 3 is that FlexRay bus distributed constant tests schematic diagram.

Finally illustrate is, preferred embodiment above is only in order to illustrate technical scheme and unrestricted, although the present invention being described in detail by above preferred embodiment, but skilled artisan would appreciate that, in the form and details it can be made various change, without departing from claims of the present invention limited range.

Claims (4)

1. the optimization method of a FlexRay bus node build-out resistor, it is characterised in that: comprise the following steps:

S1: the Chirp code signal source of 1M～10MHz is encouraged successively each node of FlexRay bus；

S2: when certain node of Chirp code signal source excitation FlexRay bus, speed A/D converter, under the effect of synchronizing signal SYNC, gathers the differential signal of other all FlexRay bus nodes successively；

S3: according to actual FlexRay physical bus Node distribution, build the distributed parameter model of FlexRay bus；

S4: the data of actual acquisition substitute into the distributed parameter model of FlexRay bus, calculates the terminal build-out resistor obtaining FlexRay each node of bus.

The optimization method of a kind of FlexRay bus node build-out resistor the most according to claim 1, it is characterised in that: in step sl, specifically include:

The Chirp code signal source of S11: described 1M～10MHz, the expression formula of this signal source is:

$e\left(t\right)=cos\left(\frac{\mathrm{\π}B}{T}{t}^2\right)---\left(1\right)$

Wherein the bandwidth B of Chirp code signal source is 10MHz, duration T be 10uS, t be time variable, cos (.) is cosine function；

S12: when the Chirp code signal source output drive FlexRay bus node of 1M～10MHz, export corresponding synchronizing signal SYNC.

The optimization method of a kind of FlexRay bus node build-out resistor the most according to claim 1, it is characterised in that: in step s 4, specifically include:

S41: according to the characteristic of Chirp code signal source, substitutes into the measurement parameter of different FlexRay node respectively, by below equation (2) be calculated 1MHz, 2MHz, 3MHz ..., 10MHz amount to 10 groups of a, b numerical value: [a₁,b₁], [a₂,b₂] ..., [a₁₀,b₁₀]；

$U_{oc}=\frac{1}{2}{U}^2(\cosh 2bL+cos2aL)---\left(2\right)$

In formula (2), U_ocFor the voltage signal at FlexRay bus node, U is the Chirp code excited signal of 1MHz～10MHz, and L is the distance of FlexRay bus node distance pumping signal, and cosh (.) is hyperbolic cosine function, and cos (.) is cosine function；

S42: according to formula (3), substitutes into a, b numerical value of 10 groups respectively: [a₁,b₁], [a₂,b₂] ..., [a₁₀,b₁₀], it is calculated 10 groups of R₀、L₀、C₀、G₀Distributed constant, be designated as [R respectively₀₁,L₀₁,C₀₁,G₀₁], [R₀₂,L₀₂,C₀₂,G₀₂] ..., [R₀₁₀,L₀₁₀,C₀₁₀,G₀₁₀]；

$\left\{\begin{array}{c}a=2\mathrm{\π}f\sqrt{L_0{C}_0}\[1+\frac{1}{32{\mathrm{\π}}^2{f}^2}{(\frac{R_0}{L_0}-\frac{G_0}{C_0})}^2\]\\ b=(\frac{R_0}{2}\sqrt{\frac{C_0}{L_0}}+\frac{G_0}{2}\sqrt{\frac{C_0}{L_0}})(1-\frac{1}{32{\mathrm{\π}}^2{f}^2}{\left(\frac{R_0}{L_0}-\frac{G_0}{C_0}\right)}^2)\end{array}\right.---\left(3\right)$

In formula (3), f is the frequency that a, b numerical value is corresponding, R₀For unit line segment resistance, L₀For unit line segment inductance, C₀Differential coupling electric capacity, G for unit line segment₀Leakage conductance for unit difference line segment；

S43: substitute into [a respectively₁,b₁]、[a₂,b₂] and corresponding frequency f, set up equation group by formula (3), solve i.e. available [R₀₁,L₀₁,C₀₁,G₀₁], then substitute into [a₂,b₂], [a₃,b₃], solve i.e. available [R₀₂,L₀₂,C₀₂,G₀₂], by that analogy, finally substitute into [a₁₀,b₁₀], [a₁,b₁], solve i.e. available [R₀₁₀,L₀₁₀,C₀₁₀,G₀₁₀]；

S44: according to the communication frequency f of FlexRay bus, substitute into the R that respective communication frequency is corresponding₀、L₀、C₀、G₀Parameter, the peripheral circuit equivalent predigesting of FlexRay bus node is two-port network model by the application Dai Weinan principle of equal effects, thus is calculated the equivalent matched resistance of FlexRay bus node.

4. the optimization device of a FlexRay bus node build-out resistor, it is characterised in that: include speed A/D converter, high-speed DAC transducer, high speed amplifier, field programmable logic device FPGA and microcontroller STM32F407；

The field programmable logic device FPGA output data of FlexRay bus signals test device obtain the Chirp code signal source of 1MHz～10MHzFlexRay bus after high-speed DAC transducer and amplifier drive, and export synchronizing signal SYNC of Chirp code simultaneously；

Speed A/D converter, under the synchronizing signal SYNC effect of Chirp code, carries out data sampling by high-speed AD controller, and sampled result is placed in the high speed dual port RAM within field programmable logic device FPGA；

Microcontroller STM32F407 reads sampling data results, and the distributed constant completing FlexRay bus in inside calculates and the optimization calculating of node matching resistance.