CN112413109B - Whole vehicle reverse analysis working method based on CAN bus network signal - Google Patents

Abstract

The invention provides a whole vehicle reverse analysis working method based on CAN bus network signals, which comprises the following steps: CAN bus data analysis and test analysis of other signals except CAN bus signals. The CAN bus data analysis steps are as follows: s1, analyzing the CAN bus network topological structure; s2, analyzing the corresponding relation between the message and the node; and S3, analyzing the key control signal. The signal analysis working method CAN effectively obtain the signal characteristics, and then based on the CAN bus data analysis result, the MCU of the whole vehicle simulator calculates the numerical value of the signal to be simulated according to the designed algorithm by the related signal on the CAN bus, so as to keep the whole vehicle running normally.

Description

The working method of vehicle reverse analysis based on CAN bus network signal

technical field

The invention relates to an analysis method, in particular to a reverse analysis working method of a vehicle based on a CAN bus network signal.

Background technique

The test machine is usually disassembled from the whole vehicle, and then the expected performance data is obtained through the engine bench test. However, with the advancement of modern automotive technology, the engine control system and other related systems of the vehicle have gradually become a whole through signal interaction, and the operating conditions of the engine are affected by the operating status of the rest of the vehicle's related systems to varying degrees. For example, the engine's top speed may be limited when in neutral, and engine torque may be limited when the drivetrain fails. In order to make the benchmarking machine run normally on the performance bench, and then measure accurate performance data, firstly, the normal signal interaction between the engine and the various systems of the vehicle is necessary; secondly, some signals that will affect the performance of the engine are required. Must also be a suitable value. Therefore, the research on vehicle signal analysis and simulation technology has become a difficult problem that needs to be overcome first in the performance benchmarking of benchmarking machines. And with the increasing complexity of automobile and engine electronic control systems, especially the emergence of hybrid vehicle engine benchmarking requirements, the difficulty of vehicle signal analysis and simulation is becoming more and more difficult. Therefore, research and establish a set of Effective vehicle signal analysis and simulation technology is also becoming more and more important.

To sum up, in order to establish the engine forward development capability, it is necessary to carry out a large number of advanced engine test evaluation and accumulation work, and the reverse analysis and simulation technology research of the vehicle signal is the first thing that needs to be completed in the development of the engine forward development capability building. Task.

SUMMARY OF THE INVENTION

The present invention aims to at least solve the technical problems existing in the prior art, and particularly innovatively proposes a working method for reverse analysis of a vehicle based on the CAN bus network signal.

In order to achieve the above-mentioned purpose of the present invention, the present invention provides a vehicle reverse analysis working method based on CAN bus network signal, comprising the following steps:

S1, get the status signal of the torque converter, the signal is located in the upper two bits of the byte7 byte of 0x39A, 0 means the engine is disconnected from the gearbox input shaft, 1 means the engine is combined with the gearbox input.

S2, obtain the speed signal of the input shaft of the gearbox, which is located in bytes 3-4 of 0x1AF. When the torque converter state is 1, the engine speed and the gearbox input shaft speed are close to the same; when the torque converter state is 0, There is a large gap between the engine speed and the input shaft speed;

S3, obtain the speed signal of the output shaft of the gearbox, which is located in bytes 5-6 of 0x1AF, the 6-speed ratio of AT is: 1st gear is 4.459, 2nd gear is 2.508, 3rd gear is 1.555, 4th gear is 1.142, 5th gear is 0.851 and 6th gear is 0.672. When the torque converter is in the combined state, the speed of the input shaft/the speed of the output shaft = the transmission ratio of the corresponding gear;

S4, obtain the wheel speed signal, the wheel speed signal includes a total of four, front, rear, left and right, all of which are located in the 0x254 message, and the four signals have the same value when driving in a straight line;

S5, obtain the vehicle speed signal, the signal is located in bytes 2-3 of 0x1A1, and its change trend is consistent with the wheel speed signal.

S6, in order to ensure the reliability of the data on the CAN bus, the data frame will contain the corresponding verification information; by parsing the vehicle data frame to obtain the verification bytes including two different algorithms in the same frame, one is to gradually increase from 0 to 1 Until the periodic check of 14, it is fed back whether the receiver has lost frames; the other is the CRC8 check algorithm, which ensures the reliability of the remaining bytes of the data frame. Get all bytes of data frame 0x1AF, check byte 1 is 4bits data, check byte 2 is 8bits data;

When the signal is simulated, the relevant parameter values on the CAN bus need to be modified. After the modification, the check value needs to be recalculated, so the CRC8 algorithm is parsed out;

Preferably, it also includes:

Between 0-57s, when the gear signal 1 simulates the vehicle speed as 140km/h, the gear signal 2 keeps the signal of D2/M2 gear 0xC6, the gear signal 3 keeps the signal of D2/M2 gear 0xC6, the gear Signal 4 remains the signal of M gear 0xF2, between 58s-111s, when gear signal 1 simulates the vehicle speed as 0km/h, gear signal 2 remains the signal of R gear 0xC2, and gear signal 3 remains R gear The signal of 0x0, the gear signal 4 is 0xF1, between 112s-278s, when the gear signal 1 simulates the vehicle speed as 140km/h, the gear signal 2 remains as the signal of D1/M1 gear 0xC5 from 112s-130s, at 131s-176s remains as D2/M2 file 0xC6 signal, 177s-205s as D3/M3 file 0xC7 signal, 206s-218s as D4/M4 file 0x08 signal, 219s-230s as D5/M5 signal The signal of gear 0xC9 is kept as the signal of D4/M4 gear 0x08 from 231s-232s, the signal of D3/M3 gear 0xC7 is kept from 233s-238s, and the signal of D2/M2 gear 0xC6 is kept from 239s-270s, the gear signal 3 Keep the signal of D1/M1 file 0xC5 from 112s-130s, the signal of D2/M2 file 0xC6 from 131s-176s, the signal of D3/M3 file 0xC7 from 177s-205s, and the D4 signal from 206s-218s The signal of /M4 file 0x08 is the signal of D5/M5 file 0xC9 from 219s-230s, the signal of D4/M4 file 0x08 is maintained from 231s-232s, and the signal of D3/M3 file 0xC7 is maintained from 233s-238s. 239s-270s remain as the signal of D2/M2 gear 0xC6, and the gear signal 4 is 0xF1.

Preferably, it also includes:

During 239s-270s, it remains as the signal of D2/M2 gear 0xC6, and during 112s-130s, gear signal 3 remains as the signal of D1/M1 gear 0xC5, and during 131s-176s, it remains as the signal of D2/M2 gear 0xC6, and at 177s-205s Keep the signal of D3/M3 file 0xC7, keep the signal of D4/M4 file 0x08 in 206s-218s, keep the signal of D5/M5 file 0xC9 in 219s-230s, and keep the signal of D4/M4 file 0x08 in 231s-232s The signal is kept as D3/M3 gear 0xC7 signal from 233s-238s, D2/M2 gear 0xC6 signal from 239s-270s, and gear signal 4 is 0xF1.

Preferably, it also includes:

Between 58-59s, when the torque converter state changes from 1 to 0 and then to 1, the engine speed increases from 1100r/min to 1800r/min, and the gearbox input shaft speed changes from 800r/min to 2000r/min; Between 104-106s, when the torque converter state changes from 1 to 0 and then to 1, the engine speed increases from 1300r/min to 1600r/min, and the gearbox input shaft speed increases from 1200r/min to 1500r/min; Between 107-109s, when the torque converter state changes from 1 to 0 and then to 1, the engine speed increases from 1300r/min to 1750r/min, and the gearbox input shaft speed increases from 1250r/min to 1600r/min; Between 108-110s, when the torque converter state changes from 1 to 0 and then to 1, the engine speed increases from 1250r/min to 1600r/min, and the gearbox input shaft speed increases from 1200r/min to 1500r/min; Between 110-112s, when the torque converter state changes from 1 to 0 and then to 1, the engine speed increases from 1200r/min to 1850r/min, and the gearbox input shaft speed increases from 1100r/min to 1600r/min.

Preferably, it also includes:

Between 186-188s, when the torque converter state changes from 1 to 0 to 1 again, the engine speed increases from 1200r/min to 1600r/min, and the gearbox input shaft speed increases from 1400r/min to 1600r/min; Between 191-193s, when the torque converter state changes from 1 to 0 and then to 1, the engine speed increases from 1100r/min to 1800r/min, and the gearbox input shaft speed increases from 1100r/min to 1600r/min; Between 231-238s, when the torque converter state repeatedly changed from 1 to 0 and then changed to 1, the engine speed repeatedly increased from 1300r/min to 1700r/min, and the gearbox input shaft speed repeatedly increased from 1200r/min to 1600r /min.

Preferably, it also includes:

Between 304-306s, when the torque converter state changes from 1 to 0 and then to 1, the engine speed increases from 1100r/min to 1800r/min, and the gearbox input shaft speed increases from 1100r/min to 1700r/min; Between 348-350s, when the torque converter state changes from 1 to 0 and then to 1, the engine speed increases from 1100r/min to 1800r/min, and the gearbox input shaft speed increases from 1100r/min to 1600r/min; Between 38-398s, when the torque converter state repeatedly changes from 1 to 0 and then to 1, the engine speed increases from 1100r/min to 1700r/min, and the gearbox input shaft speed increases from 1250r/min to 1650r/min .

Preferably, it also includes:

At 10s-28s, the gear is M1, the input shaft speed is increased from 800r/min to 1800r/min, and the output shaft speed is increased from 0r/min to 400r/min; at 28s-34s, the gear is M2, The input shaft speed is increased from 1200r/min to 2000r/min, and the output shaft speed is increased from 400r/min to 800r/min; at 34s-56s, the gear is M3, the input shaft speed is 1100r/min-1500r/min, The output shaft speed is 100r/min-800r/min; at 36s-74s, the gear is M2, the input shaft speed is 800r/min-2000r/min, and the output shaft speed is 0r/min-800r/min; at 76s -84s, the gear is M3, the input shaft speed is 1250r/min-1950r/min, and the output shaft is 800r/min-1200r/min; at 84s-91s, the gear is M4, and the input shaft speed is 1350r/min-1800r/min, output shaft speed is 1200r/min-1600r/min.

Preferably, it also includes:

From 91s to 101s, the gear is M5, the input shaft speed is 1350r/min-1800r/min, and the output shaft speed is 1600r/min-2150r/min; from 101s to 103s, the gear is M6, and the input shaft The speed is 1200r/min-1800r/min, the output shaft speed is 2000r/min-2150r/min; in 103s-106s, the gear is M5, the input shaft speed is 1200r/min-1600r/min, and the output shaft speed is 1600r/min-2000r/min; at 106s-110s, the gear is M4, the input shaft speed is 1200r/min-1700r/min, and the output shaft speed is 1200r/min-1600r/min; at 110s-112s, The gear is M3, the speed of the input shaft is 1150r/min-1600r/min, and the speed of the output shaft is 800r/min-1200r/min; at 112s-148s, the gear is M2, and the speed of the input shaft is 800r/min- 2000r/min, the output shaft speed is 100r/min-800r/min; at 148s-175s, the gear is M3, the input shaft speed is 1250r/min-1950r/min, and the output shaft speed is 800r/min-1200r/ min; at 175s-187s, the gear is M4, the input shaft speed is 1200r/min-1600r/min, and the output shaft speed is 1200r/min-1400r/min; at 187s-190s, the gear is M3, The input shaft speed is 1200r/min-1600r/min, the output shaft speed is 800r/min-1200r/min; in 190s-202s, the gear is M2, the input shaft speed is 1000r/min-2000r/min, the output shaft The rotating speed is 200r/min-800r/min.

Preferably, it also includes:

In 202s-209s, the gear is M3, the input shaft speed is 1200r/min-2000r/min, and the output shaft is 800r/min-1200r/min; in 209s-220s, the gear is M4, and the input shaft The speed is 1400r/min-2400r/min, the output shaft speed is 1200r/min-2000r/min; in 220s-226s, the gear is M5, the input shaft speed is 1800r/min-2200r/min, and the output shaft speed is 2000r/min-2600r/min; at 226s-230s, the gear is M6, the input shaft speed is 1200r/min-2200r/min, and the output shaft speed is 2100r/min-2600r/min; at 230s-232s, The gear is M5, the input shaft speed is 1200r/min-1600r/min, and the output shaft speed is 1800r/min-2100r/min; at 232s-234s, the gear is M4, and the input shaft speed is 1200r/min- 1600r/min, the output shaft speed is 1300r/min-1800r/min; at 234s-236s, the gear is M3, the input shaft speed is 1200r/min-1600r/min, and the output shaft speed is 1000r/min-1300r/ min; at 236s-300s, the gear is M2, the input shaft speed is 800r/min-2000r/min, and the output shaft speed is 100r/min-1000r/min; at 300s-306s, the gear is M3, The speed of input shaft is 1180r/min-2000r/min, and the speed of output shaft is 850r/min-950r/min; in 306s-326s, the gear is M2, the speed of input shaft is 1100-2000, and the speed of output shaft is 200r/ min-800r/min; at 326s-348s, the gear is M3, the input shaft speed is 1100-1800, and the output shaft speed is 800r/min-1100r/min; at 348s-358s, the gear is M2, The input shaft speed is 1100r/min-1800r/min, the output shaft speed is 200r/min-800r/min; at 358s-366s, the gear is M3, the input shaft speed is 1200r/min-2000r/min, the output shaft The rotating speed is 800r/min-1200r/min.

Preferably, it also includes:

From 366s to 378s, the gear is M4, the input shaft speed is 1400r/min-3000r/min, and the output shaft speed is 1200r/min-2500r/min; from 378s to 382s, the gear is M5, and the input shaft The speed is 2200r/min-3000r/min, the output shaft speed is 2500r/min-3000r/min; in 382s-388s, the gear is M6, the input shaft speed is 1200r/min-2400r/min, and the output shaft speed is 2000r/min-2500r/min; at 388s-390s, the gear is M5, the input shaft speed is 1200r/min-1800r/min, and the output shaft speed is 1600r/min-2000r/min; at 390s-392s, The gear is M4, the speed of the input shaft is 1200r/min-1800r/min, and the speed of the output shaft is 1200r/min-1600r/min; at 392s-396s, the gear is M3, and the speed of the input shaft is 1200r/min- 1800r/min, the output shaft speed is 700r/min-1200r/min; at 396s-468s, the gear is M2, the input shaft speed is 800r/min-2000r/min, and the output shaft speed is 50r/min-750r/ min; at 468s-476s, the gear is M3, the input shaft speed is 1000r/min-2000r/min, and the output shaft speed is 750r/min-900r/min; at 476s-498s, the gear is M2, The input shaft speed is 700r/min-2000r/min, and the output shaft speed is 0r/min-900r/min.

To sum up, due to the adoption of the above technical solutions, the present invention has the beneficial effects of realizing the whole-vehicle signal analysis process in the benchmarking work of advanced engine performance.

The reverse analysis method of this patent can be effectively applied to the subsequent vehicle simulation. The analog signal obtained from this is not only more accurate, but also more easily recognized by the vehicle system, providing a set of effective solutions for the benchmarking work of advanced models with increasingly complex electronic control systems, effectively improving our Market competitiveness in the field of advanced engine testing and evaluation.

Additional aspects and advantages of the present invention will be set forth, in part, from the following description, and in part will be apparent from the following description, or may be learned by practice of the invention.

Description of drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of embodiments taken in conjunction with the accompanying drawings, wherein:

Fig. 1 is the network topology structure diagram of the present invention;

Fig. 2 is the gear position signal diagram of the present invention;

Fig. 3 is the speed diagram of the gearbox input shaft of the present invention;

4 is a diagram showing the relationship between the speed of the input shaft of the gearbox of the present invention and the speed of the output shaft;

Fig. 5 is the wheel speed signal diagram of the present invention;

Fig. 6 is the vehicle speed signal diagram of the present invention;

Fig. 7 is a data frame check byte diagram of the present invention;

Fig. 8 is the flow chart of CRC8 algorithm of the present invention;

Fig. 9 is the gateway schematic diagram of the present invention;

Figure 10 is a flow chart of the gateway program of the present invention.

Detailed ways

The following describes in detail the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals refer to the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary, only used to explain the present invention, and should not be construed as a limitation of the present invention.

In order to complete the engine benchmarking work, it is necessary to make the engine run normally on the test bench. After the engine is disassembled from the vehicle, the wheels, gearbox and other parts of the vehicle cannot operate normally. In this case, the ECU usually does not operate normally for theft prevention and safety reasons, and there may be a speed limit. or torque limit. At this time, it is necessary to simulate the signals that affect the normal operation of the engine (such as the signal of the vehicle speed and the gearbox), so that the engine can run normally on the bench.

Usually, equipment such as a signal generator is used to simulate signals such as wheel speed. The disadvantage is that the simulated signal cannot respond to the actual operating conditions of the engine in time. As the automotive electronic control system becomes more and more complex, the defects of this method become more and more obvious, and it can no longer meet the signal simulation requirements of the standard model.

The method used in this case considers the influence of the signals on the CAN bus on the engine operation, first analyzes the CAN bus signal of the whole vehicle, and then uses the gateway method to filter and modify the key signals that affect the engine operation at the vehicle end. Sent to the ECU to ensure the normal operation of the engine. Based on the results of CAN bus data analysis, the analog signal is automatically calculated and output by the microcontroller according to the designed strategy, which matches the actual operating conditions of the engine and can respond in time to changes in engine operating conditions.

The implementation of data simulation technology based on CAN bus mainly includes three aspects of work, one is CAN bus data analysis work, the other is signal simulation work, and the third is the drive control work of some actuators.

The CAN bus data analysis work is roughly divided into the following aspects:

1) Analysis of CAN bus network topology;

2) Analysis of the correspondence between messages and nodes, to clarify which messages are sent by the transmission control unit, the engine control unit, and the ABS/ESP control unit;

3) Analysis of key control signals, including vehicle speed, gear, engine speed and load, etc., to clarify which messages have an impact on engine operation, and focus on analyzing these messages.

The whole vehicle signal simulation work is divided into two aspects, one is CAN bus signal simulation, and the other is other signal simulation that affects the normal operation of the engine after the locomotive is separated. The bus signal simulation adopts the form of adding gateways between network nodes. Based on the results of previous data analysis, the signal simulation system gives appropriate analog values for the key signals affecting the engine operation and sends them to the network, and directly forwards other non-critical signals. .

For the simulation of signals other than CAN bus signals, it is roughly divided into three steps:

1) Test and analyze the signal characteristics, including wheel speed, vehicle speed, gearbox input shaft and output shaft speed and other signals;

2) Based on the CAN bus data analysis result, the MCU of the vehicle simulator calculates the value of the signal to be simulated from the relevant signals on the CAN bus according to the designed algorithm;

3) The analog signal is output by the hardware circuit of the signal simulation system, and the electrical parameters of the hardware are adjusted to ensure that the characteristics of the analog signal are basically the same as those of the original signal.

In order to complete the engine performance benchmarking test task, it is usually necessary to independently control the throttle valve, pressure regulating valve and other actuators of the benchmarking machine. The signal simulation system has specially designed corresponding drive control functions for this purpose.

The present invention is further described below in conjunction with the accompanying drawings and embodiments (taking BMW MINI as an example):

1 Overview

During the engine benchmarking test, in order to ensure the normal operation of the engine on the bench, it is necessary to simulate the signals of other modules of the vehicle during the test, such as the input and output shaft signals of the gearbox and the wheel speed sensor signals. Therefore, it is necessary to analyze the important signals of the whole vehicle in the early stage, and simulate the relevant signals according to a certain strategy during the bench test, and cooperate to complete the bench test.

2. CAN network signal analysis

2.1 Signal Analysis Content

(1) Determine the CAN network topology of the BMW MINI vehicle;

(2) Analyze the basic attributes such as the correspondence between each message and the network node, and the sending period;

(3) Analyze the key CAN signals and control logic of the vehicle;

2.2 Using the device

CANoe hardware and software, laptops, BMW diagnostics, DB9, multimeters

2.3 Terms and abbreviations

DME: Engine Controller

EGS: Transmission Controller

DSC: Dynamic Stability Control System

ZGM: Central Gateway

KOMBI: Dashboard

2.4 Analytical Results and Simulation Analysis

2.4.1 Network topology: As shown in Figure 1, the vehicle has two power CANs, PT-CAN and PT-CAN2. PT-CAN is used for vehicle communication, PT-CAN2 is mainly for communication between DME and EGS, and the communication rate is 500kb/s. DSC communicates with ZGM through flexray, ZGM converts flexray data frame into CAN data frame and communicates with DME through PT-CAN.

2.4.2 CAN bus messages and attributes

When the vehicle is powered on normally and there is no fault, there are 122 frames of messages on PT-CAN and 25 frames of messages on PT-CAN2, as shown in Table 1.

Table 1 CAN bus message

2.4.3 Analysis of key signals and control strategies

Since the gearbox did not work during the engine bench test, in order to make the engine run normally, it is necessary to simulate the relevant signals of the gearbox. Considering that the mini gearbox is AT, the input shaft and output shaft signals of the gearbox need to be simulated. At the same time, it is also necessary to simulate signals such as vehicle speed and gear position. Therefore, the above signals are analyzed on the CAN bus, and the results are shown in Table 2.

Table 2 Analysis results of key signals

2.4.3.1 Gear Signal 1

This signal is located in the byte2 byte of 0x3FD, indicating the handle position, which is defined as follows:

P file: 0x20 R file: 0x40 N file: 0x60 D file: 0x80 S file: 0x81 M file: 0x82

2.4.3.2 Gear Signal 2

The signal is located in the byte2 byte of 0x1AC, and the values of the D and M files are the same in the corresponding gears. The specific definitions are as follows:

P file: 0xC3 N file: 0xC1 R file: 0xC2

D1/M1 file: 0xC5 D2/M2 file: 0xC6 D3/M3 file: 0xC7

D4/M4 file: 0xC8 D5/M5 file: 0xC9 D6/M6 file: 0xCA

2.4.3.3 Gear Signal 3

This signal is located in the byte3 byte of 0x39A. The manual gear and the automatic gear multiplex the same value. The specific definitions are as follows:

N file: 0x01 R file: 0x02 P file: 0x03

D1/M1 file: 0x05 D2/M2 file: 0x06 D3/M3 file: 0x07

D4/M4 file: 0x08 D5/M5 file: 0x09 D6/M6 file: 0x0A

2.4.3.4 Gear Signal 4

M file: 0xF2 P file, R file, N file, D file: 0xF1

The gear signal collected by the real vehicle is shown in Figure 2.

2.4.3.5 Torque Converter Status

This signal is located in the upper two bits of the byte7 byte of 0x39A, 0 means the engine is disconnected from the gearbox input shaft, and 1 means the engine is combined with the gearbox input.

2.4.3.6 Gearbox input shaft speed

The signal is located in byte 3-4 of 0x1AF, and the result parsed by CANoe is shown in Figure 3. When the torque converter state is 1, the engine speed and the transmission input shaft speed are close to the same; when the torque converter state is 0, the engine speed and the input shaft speed have a large gap.

Between 0-57s, when the gear signal 1 simulates the vehicle speed as 140km/h, the gear signal 2 keeps the signal of D2/M2 gear 0xC6, the gear signal 3 keeps the signal of D2/M2 gear 0xC6, the gear Signal 4 remains the signal of M gear 0xF2, between 58s-111s, when gear signal 1 simulates the vehicle speed as 0km/h, gear signal 2 remains the signal of R gear 0xC2, and gear signal 3 remains R gear The signal of 0x0, the gear signal 4 is 0xF1, between 112s-278s, when the gear signal 1 simulates the vehicle speed as 140km/h, the gear signal 2 remains as the signal of D1/M1 gear 0xC5 from 112s-130s, at 131s-176s remains as D2/M2 file 0xC6 signal, 177s-205s as D3/M3 file 0xC7 signal, 206s-218s as D4/M4 file 0x08 signal, 219s-230s as D5/M5 signal The signal of gear 0xC9 is kept as the signal of D4/M4 gear 0x08 from 231s-232s, the signal of D3/M3 gear 0xC7 is kept from 233s-238s, and the signal of D2/M2 gear 0xC6 is kept from 239s-270s, the gear signal 3 Keep the signal of D1/M1 file 0xC5 from 112s-130s, the signal of D2/M2 file 0xC6 from 131s-176s, the signal of D3/M3 file 0xC7 from 177s-205s, and the D4 signal from 206s-218s The signal of /M4 file 0x08 is the signal of D5/M5 file 0xC9 from 219s-230s, the signal of D4/M4 file 0x08 is maintained from 231s-232s, and the signal of D3/M3 file 0xC7 is maintained from 233s-238s. 239s-270s remain as the signal of D2/M2 gear 0xC6, and the gear signal 4 is 0xF1.

2.4.3.7 Gearbox output shaft speed

The signal is located in bytes 5-6 of 0x1AF. The 6-speed ratio of AT is: 1st 4.459, 2nd 2.508, 3rd 1.555, 4th 1.142, 5th 0.851, 6th 0.672. As shown in Figure 4, when the torque converter is in the combined state, the input shaft speed/output shaft speed = the transmission ratio of the corresponding gear, and the ratio when the torque converter is disconnected is different from the theoretical value.

2.4.3.8 Wheel speed signal

There are four wheel speed signals including front, rear, left and right, all of which are located in the 0x254 message. The values of the four signals are the same when driving in a straight line, but there will be certain differences when turning. The analysis results are shown in Figure 5.

2.4.3.9 Vehicle speed signal

This signal is located in bytes 2-3 of 0x1A1, and its change trend is consistent with the wheel speed signal, as shown in Figure 6.

2.4.4 Analysis of CAN bus verification signal

2.4.4.1 Bus check signal

Generally, in order to ensure the reliability of the data on the CAN bus, the data frame will contain the corresponding verification information. By parsing the data frame of MINI, it is found that the same frame includes two check bytes of different algorithms, one is a periodic check that increases from 0 to 14, which can inform the receiver whether there is frame loss; The other is a more complex CRC8 check algorithm, which ensures the reliability of other bytes of data in the data frame. Figure 7 shows all the bytes of the data frame 0x1AF, in which the first two signals are the check values obtained by the two check algorithms, the check byte 1 is 4 bits of data, and the check byte 2 is 8 bits. data.

Considering that the relevant parameter values on the CAN bus need to be modified during signal simulation, the check value needs to be recalculated after modification, so the CRC algorithm must be parsed.

2.4.4.2 Analysis of CRC8 Algorithm

The CRC8 algorithm is to perform binary division between the value to be checked and an 8-bit polynomial, and then perform an XOR operation on the result of the calculation and a byte. Therefore, to analyze the algorithm is to determine the value of the polynomial and the XOR.

The calculation function of CRC8 is CRC8_Cal (unsigned char*ptr, unsigned char poly_v, unsigned char xor_v). The algorithm flow is shown in Figure 8.

Among them, *ptr: points to the array where the check value needs to be calculated,

poly_v: the value of the polynomial is 0-255,

xor_v: XOR value is 0-255,

Through this algorithm, the polynomial and XOR value can be quickly determined, and finally it is found that the CRC8 of all data frames is the same polynomial, and each XOR value is different, as shown in Table 3.

Table 3 Checksum specific information

message ID XOR (hex) The byte where the CRC check is located 0xF3 0x8F Byte0 0x1A1 0x0F Byte0 0x1AC 0xE0 Byte7 0x1AF 0x43 Byte0 0x3FD 0x70 Byte0

3. Signal simulation

When the engine bench test is carried out, the signal is simulated based on the previously analyzed relevant signals and the control strategy of the engine to make the engine work normally.

3.1 Gateway function

As shown in Figure 9, the signal simulation is implemented through two gateways. Disconnect the two CAN buses of the original car from the engine side and add them to the gateway. Each gateway has 2 CAN modules, which are respectively connected to the disconnected CAN bus. Its function is to directly forward the data received on one CAN from the other, or modify the corresponding value according to a certain strategy from the other CAN. forwarded.

3.2 Signal Simulation Strategy

For automatic transmission AT, if the gear is shifted to D or M during the bench test, the transmission overheating failure will occur after the engine runs for a certain period of time. Therefore, the test can only be carried out by shifting the gear to the N gear. In order to maximize the engine performance, it is necessary to tell the engine to be in the M gear through the CAN bus, and simulate different gears according to the different engine speeds. At the same time, it is necessary to simulate the speed of the input shaft and output shaft of the gearbox, as well as the vehicle speed signal.

Since the signals of the two CAN buses need to be synchronized according to the engine speed, only the PT-CAN has the engine speed information. In order to obtain the real-time engine speed information on the PT-CAN2 bus, communication between gateway 1 and gateway 2 is required. According to Hardware configuration can be achieved through the serial port (SCI). The program flow chart of the gateway is shown in 10.

According to the results of the previous signal analysis, the frame of the signal to be modified includes 0xF3 (including engine speed), 0x1AC (gear information), 0x39A (gear and torque converter status), 0x3FD (gear information), 0x1AF (including gear shift information) box input shaft and output shaft speed), 0x1A1 (vehicle speed information), 0x254 (wheel speed information), etc.

The signal simulation is performed in the N gear. When the gateway 2 recognizes that the engine speed is greater than 900rpm, it will modify the gear signal, torque converter lock signal, vehicle speed and wheel speed signals on the PT-CAN engine side to reasonable values; if the engine speed If it is less than 800rpm, gateway 2 directly forwards the packets without any modification.

At the same time, gateway 2 sends the actual engine speed, state change parameter St_Val (determined by engine speed), and gear to gateway 1 through SCI. If St_Val is 0x55, gateway 1 modifies the engine speed, gear, The torque converter lock state, input shaft and output shaft speeds (determined by engine speed and gear) are the corresponding values; if St_Val is 0, gateway 1 directly forwards the message without any modification.

4. Analysis of other parameters of the engine

In order to obtain more engine parameter values and conduct more in-depth engine bench tests, real-time data of relevant parameters can be obtained by analyzing the diagnostic instrument protocol.

4.1 Analysis of Diagnostic Protocol

The CANH and CANL are drawn from the diagnostic interface, and the messages on the bus during the data stream operation are read by the CANOE observation diagnostic instrument. After analysis, it can be seen that the application layer diagnostic protocol is the UDS protocol—the protocol of the ISO 14229 network layer conforms to ISO 15765-2 , including the definition of single frame, start frame, continuous frame and data flow control.

The message ID sent by the diagnostic instrument and the message ID returned by each module are shown in Table 4 below. Each module judges whether the first byte sent by the diagnostic instrument is a data stream read to the module (as shown in Table 5). If the judgment is yes, the value of the corresponding parameter will be returned, otherwise, no response will be made.

Table 4 Diagnosis-related message IDs

message type Packet ID (hex) Diagnostic tool data flow request message 0x6F1 The engine controller returns the message 0x612 Transmission controller return message 0x618 Body controller return message 0x640

Table 5 The value of the 0th byte of the data flow request service message of the diagnostic instrument

Diagnostic tool data stream request module The value of the 0th byte of the request message engine 0x12 gearbox 0x18 body controller 0x40

4.2 Data flow analysis

The analysis shows that the diagnostic instrument uses different services for reading data streams of different modules [1], that is, achieves the same purpose through different methods.

(1) For the EGS gearbox controller module, the diagnostic instrument directly uses the service 0x22 (through the ID reading service) to read the data stream;

(2) For the DME engine controller module, the diagnostic instrument first uses the service 0x2C (dynamic definition ID service) to dynamically define the original ID value of the parameter as 0xF300, and then uses the service 0x22 to read the value of 0xF300, and the corresponding parameter can be read value of .

Since it is mainly to read the parameters of the DME module, only the second way is needed to parse the data stream, and the results of the parsing are shown in Table 6. PID means that the real-time data of the parameter can be obtained through the corresponding PID value according to the protocol; the length means that the parameter value is represented by several bytes; the coefficient and offset represent the conversion relationship between the bus value and the physical value.

Table 6 Analysis results of engine parameters

4.3 Data Stream Collection

Using the PID values corresponding to the parameters in Table 6, write codes according to the ISO14229 protocol to obtain the real-time values of the corresponding parameters, and send these values to the bench through the CAN module to realize the collection of data streams.

Claims (1)

1. A whole vehicle reverse analysis working method based on CAN bus network signals is characterized by comprising the following steps:

s1, acquiring a state signal of the torque converter, wherein the signal is positioned at the upper two bits of byte7 of 0x39A, 0 represents that the engine is disconnected with the input shaft of the gearbox, and 1 represents that the engine is combined with the input shaft of the gearbox;

s2, acquiring a speed signal of the input shaft of the gearbox, wherein the speed signal is located at byte3-4 of 0x1AF, and when the state of the torque converter is 1, the rotating speed of the engine is approximately consistent with the rotating speed of the input shaft of the gearbox; when the state of the torque converter is 0, the rotating speed of the engine has a larger difference with the rotating speed of the input shaft;

s3, acquiring a speed signal of the output shaft of the gearbox, wherein the speed signal is located AT byte5-6 of 0x1AF, and the 6-gear speed ratios of the AT are respectively as follows: 4.459 for the 1 st gear, 2.508 for the 2 nd gear, 1.555 for the 3 rd gear, 1.142 for the 4 th gear, 0.851 for the 5 th gear and 0.672 for the 6 th gear; when the torque converter is in a combined state, the rotating speed of the input shaft/the rotating speed of the output shaft is equal to the transmission ratio of the corresponding gear;

s4, wheel speed signals are obtained, the wheel speed signals comprise four signals in all, namely, front, rear, left and right, and are all located on the 0x254 message, and the values of the four signals are consistent when the four signals are in straight line driving;

s5, acquiring a vehicle speed signal, wherein the vehicle speed signal is located at byte2-3 of 0x1A1, and the change trend of the vehicle speed signal is consistent with the wheel speed signal;

s6, in order to ensure the reliability of the data on the CAN bus, the data frame contains corresponding check information; acquiring check bytes comprising two different algorithms in the same frame by analyzing the vehicle data frame, wherein one is a periodic cyclic check from 0 to 1 step by step until 14, and feeds back whether a receiver loses frames or not; the other is a CRC8 checking algorithm, which ensures the reliability of the data of the rest bytes of the data frame; acquiring all bytes of a data frame 0x1AF, wherein check byte 1 is data of 4bits, and check byte2 is data of 8 bits;

when the signals are simulated, relevant parameter values on the CAN bus need to be modified, and check values need to be recalculated after modification, so that the CRC8 algorithm is analyzed;

the signal simulation is carried out in an N gear, when the gateway 2 identifies that the rotating speed of the engine is greater than 900rpm, gear signals, torque converter locking signals, vehicle speed and wheel speed signal values of the PT-CAN engine side are modified; if the rotating speed of the engine is less than 800rpm, the gateway 2 directly forwards the message without any modification;

meanwhile, the gateway 2 sends the actual engine speed, the state change parameter St _ Val and the gear to the gateway 1 through the SCI, and if the St _ Val is 0x55, the gateway 1 modifies the engine speed, the gear, the torque converter locking state and the input shaft and output shaft speed of the PT-CAN2 engine side into corresponding values; if St _ Val is 0, the gateway 1 directly forwards the message without any modification;

further comprising:

between 0-57s, when gear signal 1 simulates vehicle speed as 140km/h, gear signal 2 remains as a signal of D2/M2 gear 0xC6, gear signal 3 remains as a signal of D2/M2 gear 0xC6, gear signal 4 remains as a signal of M gear 0xF2, between 58s-111s, when gear signal 1 simulates vehicle speed as 0km/h, gear signal 2 remains as a signal of R gear 0xC2, gear signal 3 remains as a signal of R gear 0x0, gear signal 4 is 0xF1, between 112s-278s, when gear signal 1 simulates vehicle speed as 140km/h, gear signal 2 remains as a signal of D1/M0 xC5 between 112s-130s, between 131s-176s remains as a signal of D2/M2 gear 0xC6, between 177 s-177 s and 7 as a signal of D3/M7, signals of D4/M4 gear 0x08 are kept at 206s-218s, signals of D5/M5 gear 0xC9 are kept at 219s-230s, signals of D4/M4 gear 0x08 are kept at 231s-232s, signals of D3/M3 gear 0xC7 are kept at 233s-238s, signals of D2/M2 gear 0xC6 are kept at 239s-270s, and gear signal 4 is 0xF 1;

further comprising:

signals of D2/M2 gear 0xC6 are kept at 239s-270s, signals of D1/M1 gear 0xC5 are kept at 112s-130s, signals of D2/M2 gear 0xC6 are kept at 131s-176s, signals of D3/M3 gear 0xC7 are kept at 177s-205s, signals of D4/M4 gear 0x08 are kept at 206s-218s, signals of D5/M5 gear 0xC5 are kept at 219s-230s, signals of D5/M5 gear 0x5 are kept at 231s-232s, signals of D5/M5 gear 0x5 are kept at 233 s-s, signals of D5/M5 gear 0xC5 are kept at 239s-270s, signals of D5/M5 gear 0xC5 are kept at 239s-270s, and signals of D5/M5 gear 0xC5 are 5 at 5 f 5;

further comprising:

between 58-59s, when the state of the torque converter changes from 1 to 0 and then to 1, the engine speed is increased from 1100r/min to 1800r/min, and the speed of the input shaft of the gearbox is increased from 800r/min to 2000 r/min; between 104 and 106s, when the state of the torque converter changes from 1 to 0 and then to 1, the rotating speed of the engine is increased from 1300r/min to 1600r/min, and the rotating speed of the input shaft of the gearbox is increased from 1200r/min to 1500 r/min; between 107-; between 108-; between 110 and 112s, when the state of the torque converter changes from 1 to 0 and then to 1, the rotating speed of the engine is increased from 1200r/min to 1850r/min, and the rotating speed of the input shaft of the gearbox is increased from 1100r/min to 1600 r/min;

further comprising:

between 186 and 188s, when the state of the torque converter changes from 1 to 0 and then to 1, the engine speed is increased from 1200r/min to 1600r/min, and the speed of the input shaft of the gearbox is increased from 1400r/min to 1600 r/min; between 191-193s, when the state of the torque converter changes from 1 to 0 and then to 1, the engine speed is increased from 1100r/min to 1800r/min, and the speed of the input shaft of the gearbox is increased from 1100r/min to 1600 r/min; between 231-;

further comprising:

between 304-306s, when the torque converter state changes from 1 to 0 to 1, the engine speed increases from 1100r/min to 1800r/min and the transmission input shaft speed increases from 1100r/min to 1700 r/min; between 348 and 350s, when the state of the torque converter changes from 1 to 0 and then to 1, the rotating speed of the engine is increased from 1100r/min to 1800r/min, and the rotating speed of the input shaft of the gearbox is increased from 1100r/min to 1600 r/min; between 38-398s, when the torque converter state repeatedly changes from 1 to 0 to 1, the engine speed is increased from 1100r/min to 1700r/min, and the speed of the input shaft of the gearbox is increased from 1250r/min to 1650 r/min;

further comprising:

at 10s-28s, the gear is M1, the rotating speed of the input shaft is increased to 1800r/min from 800r/min, and the rotating speed of the output shaft is increased to 400r/min from 0 r/min; at 28s-34s, the gear is M2, the rotating speed of the input shaft is increased from 1200r/min to 2000r/min, and the rotating speed of the output shaft is increased from 400r/min to 800 r/min; when the speed is 34s-56s, the gear is M3, the rotating speed of the input shaft is 1100r/min-1500r/min, and the rotating speed of the output shaft is 100r/min-800 r/min; at 36s-74s, the gear is M2, the rotating speed of the input shaft is 800r/min-2000r/min, and the rotating speed of the output shaft is 0r/min-800 r/min; at 76s-84s, the gear is M3, the speed of the input shaft is 1250r/min-1950r/min, and the speed of the output shaft is 800r/min-1200 r/min; when the speed is between 84s and 91s, the gear is M4, the rotating speed of the input shaft is 1350r/min to 1800r/min, and the rotating speed of the output shaft is 1200r/min to 1600 r/min;

further comprising:

when the speed is 91s-101s, the gear is M5, the rotating speed of the input shaft is 1350r/min-1800r/min, and the rotating speed of the output shaft is 1600r/min-2150 r/min; when the speed is 101s-103s, the gear is M6, the rotating speed of the input shaft is 1200r/min-1800r/min, and the rotating speed of the output shaft is 2000r/min-2150 r/min; when the speed is 103s-106s, the gear is M5, the rotating speed of the input shaft is 1200r/min-1600r/min, and the rotating speed of the output shaft is 1600r/min-2000 r/min; at 106s-110s, the gear is M4, the rotating speed of the input shaft is 1200r/min-1700r/min, and the rotating speed of the output shaft is 1200r/min-1600 r/min; at 110s-112s, the gear is M3, the rotating speed of the input shaft is 1150r/min-1600r/min, and the rotating speed of the output shaft is 800r/min-1200 r/min; at 112s-148s, the gear is M2, the rotating speed of the input shaft is 800r/min-2000r/min, and the rotating speed of the output shaft is 100r/min-800 r/min; when the speed is 148s-175s, the gear is M3, the rotating speed of the input shaft is 1250r/min-1950r/min, and the rotating speed of the output shaft is 800r/min-1200 r/min; when the speed is 175s-187s, the gear is M4, the rotating speed of the input shaft is 1200r/min-1600r/min, and the rotating speed of the output shaft is 1200r/min-1400 r/min; when 187-190 s, the gear is M3, the rotating speed of the input shaft is 1200r/min-1600r/min, and the rotating speed of the output shaft is 800r/min-1200 r/min; at 190s-202s, the gear is M2, the rotating speed of the input shaft is 1000r/min-2000r/min, and the rotating speed of the output shaft is 200r/min-800 r/min;

further comprising:

when the speed is 202s-209s, the gear is M3, the rotating speed of the input shaft is 1200r/min-2000r/min, and the rotating speed of the output shaft is 800r/min-1200 r/min; when the speed is 209s-220s, the gear is M4, the rotating speed of the input shaft is 1400r/min-2400r/min, and the rotating speed of the output shaft is 1200r/min-2000 r/min; at 220s-226s, the gear is M5, the rotating speed of the input shaft is 1800r/min-2200r/min, and the rotating speed of the output shaft is 2000r/min-2600 r/min; at 226s-230s, the gear is M6, the rotating speed of the input shaft is 1200r/min-2200r/min, and the rotating speed of the output shaft is 2100r/min-2600 r/min; at 230s-232s, the gear is M5, the rotating speed of the input shaft is 1200r/min-1600r/min, and the rotating speed of the output shaft is 1800r/min-2100 r/min; when the speed is 232s-234s, the gear is M4, the rotating speed of the input shaft is 1200r/min-1600r/min, and the rotating speed of the output shaft is 1300r/min-1800 r/min; at 234s-236s, the gear is M3, the rotating speed of the input shaft is 1200r/min-1600r/min, and the rotating speed of the output shaft is 1000r/min-1300 r/min; when the speed is 236s-300s, the gear is M2, the rotating speed of the input shaft is 800r/min-2000r/min, and the rotating speed of the output shaft is 100r/min-1000 r/min; at 300s-306s, the gear is M3, the rotating speed of the input shaft is 1180r/min-2000r/min, and the rotating speed of the output shaft is 850r/min-950 r/min; at 306s-326s, the gear is M2, the input shaft speed is 1100-2000, and the output shaft speed is 200r/min-800 r/min; at 326s-348s, the gear is M3, the input shaft speed is 1100-1800, and the output shaft speed is 800r/min-1100 r/min; when the speed is 348s-358s, the gear is M2, the rotating speed of the input shaft is 1100r/min-1800r/min, and the rotating speed of the output shaft is 200r/min-800 r/min; at 358s-366s, the gear is M3, the rotation speed of the input shaft is 1200r/min-2000r/min, and the rotation speed of the output shaft is 800r/min-1200 r/min;

further comprising:

at 366s-378s, the gear is M4, the rotating speed of the input shaft is 1400r/min-3000r/min, and the rotating speed of the output shaft is 1200r/min-2500 r/min; at 378s-382s, the gear is M5, the rotating speed of the input shaft is 2200r/min-3000r/min, and the rotating speed of the output shaft is 2500r/min-3000 r/min; at 382s-388s, the gear is M6, the rotating speed of the input shaft is 1200r/min-2400r/min, and the rotating speed of the output shaft is 2000r/min-2500 r/min; when the speed is 388s-390s, the gear is M5, the rotating speed of the input shaft is 1200r/min-1800r/min, and the rotating speed of the output shaft is 1600r/min-2000 r/min; at 390s-392s, the gear is M4, the rotating speed of the input shaft is 1200r/min-1800r/min, and the rotating speed of the output shaft is 1200r/min-1600 r/min; at 392s-396s, the gear is M3, the rotating speed of the input shaft is 1200r/min-1800r/min, and the rotating speed of the output shaft is 700r/min-1200 r/min; when 396s-468s is reached, the gear is M2, the rotating speed of the input shaft is 800r/min-2000r/min, and the rotating speed of the output shaft is 50r/min-750 r/min; when 468s-476s is needed, the gear is M3, the rotating speed of the input shaft is 1000r/min-2000r/min, and the rotating speed of the output shaft is 750r/min-900 r/min; at 476s-498s, the gear is M2, the input shaft speed is 700r/min-2000r/min, and the output shaft speed is 0r/min-900 r/min.

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