Data acquisition and analysis system of AMT

Data acquisition and analysis system of vehicle AMT

1 introduction

electronically controlled mechanical automatic transmission, namely AMT (automated me mechanical transmission), plays an important role in the automatic transmission family because of its advantages of high transmission efficiency, low cost and easy manufacturing [1]. Its basic control principle is shown in Figure 1-1. AMT system is a complex multi input and multi output control system with many parameters and fast changes, which is difficult to be analyzed and studied by manual direct observation [2]. In order to develop AMT, a data acquisition and analysis system is developed. While collecting a large amount of data, the system must also have the functions of data classification, storage and analysis, and directly display the technical indicators that researchers are concerned about

2 system composition

the data acquisition and analysis system is composed of a lower computer and an upper computer. The lower computer and the upper computer transmit data through serial port communication

the lower computer mainly completes the signal acquisition. Because the signal of the data acquisition system is also used by the AMT's electric control unit ECU, in order to simplify the system structure, the lower computer of the acquisition system and the AMT's control system can share some hardware, and on this basis, a serial interface circuit is added

the upper computer is a PC, which is mainly perpendicular to the plane of the leaf spring seat: the fulcrum completes the functions of data classification, storage and Analysis on the axis line of the 2 steering knuckle

3 system hardware design

the design of system hardware fully considers the impact of working environment such as vehicle vibration and impact, electromagnetic compatibility, high and low temperature, power supply changes, and adheres to the principle of reliability. The hardware composition of the system is shown in Figure 3-1. The upper computer adopts PC104 Embedded Computer with excellent performance, mature technology and high reliability

3.1 signal acquisition

the signals to be collected and the corresponding processing circuits can be divided into three categories:

speed signals: engine speed Ne, input shaft speed n1, output shaft speed N2

analog signals: accelerator pedal LPD, throttle position lth, gear selection position ts, gear shift position TX, clutch position LC

switch signal: switch, handle signal

speed signal processing circuit: the signal generated by the speed sensor is filtered, clamped, amplified and shaped to become a pulse signal that can be processed by the single chip microcomputer

analog signal processing circuit: filter and amplify the analog signal generated by the sensor to make it within the amplitude range that can be processed by a/D conversion of single chip microcomputer

switch signal processing circuit: send the switch signal on the vehicle to the single chip microcomputer after optical isolation, which can reduce mutual interference

3.2 power supply circuit

DC/DC converter is used to convert the 24V power supply on the vehicle into the 5V power supply used by the lower computer. At the same time, the ground of the data acquisition system is isolated from the ground of the power supply on the vehicle to avoid mutual interference and ensure the reliability of the power supply of the acquisition system

3.3 serial interface circuit

80c196 single chip microcomputer and PC both have serial ports, and the communication between them is completed through the serial port. However, the serial port input/output of 80C196 high-speed railway spiral reinforcement is a special kind of ribbed reinforcement on high-speed railway, and the TTL level is output, while the serial port of PC is designed according to RS-232 standard, and the level conversion between the two is completed through the intermediate interface circuit. MAX232 is selected as the interface chip of the system, and RS-232 optical isolator is used to isolate the upper and lower computers

4 system software design

the data acquisition and analysis system software is mainly composed of two parts. One part is the acquisition and data transmission software of the lower computer, which is compiled in assembly language; The other part is the data receiving and data processing analysis software of the upper computer, which is compiled with VB language

4.1 software design of the lower computer end

because the lower computer runs the main control program of automatic gear shift while running the acquisition and data transmission program, the program is mainly interrupted in order to make the system work harmoniously and efficiently. The main control program and interrupt program, interrupt program and interrupt resolve relevant disputes through negotiation, and the communication between the programs is through global variables, so as to realize the integration of the main control program and interrupt program

4.1.1 data frame composition

since the maximum baud rate of 80C196 serial communication is 9600, and the system needs to collect more signals, if the same frequency is used for collection and transmission, the sampling frequency will inevitably be too low, so the method of variable frequency sampling is adopted. Signals with fast dynamic response, such as displacement signals, are sampled every 10 ms to form a high-frequency sampling module. Among them, the gear selection position signal (TS) and gear shift position signal (TX) are 8-bit precision and single byte during a/D conversion. Other signals are 10 bit precision, double byte. The composition of high frequency sampling module is shown in Figure 4-1. Signals with slow dynamic response, such as speed signal (double byte) and switch signal (single byte), are sampled every 100 ms to form a low-frequency sampling module. As shown in Figure 4-2:

100 ms is a complete sampling period. Pack the data collected within 100 ms into a data frame. Each frame data consists of one frame synchronization byte, one low-frequency data module and nine high-frequency data modules, with a total of 81 bytes. As shown in Figure 4-3:

4.1.2 software design of signal acquisition

the acquisition of each signal is completed by the software timer, and an interrupt is generated at a certain interval. This software interrupt is used to start the sampling, conversion and reading of the input signal, and the first byte of the data block to be sent is sent to the serial port sending register, so as to start the serial port interrupt service program. The software timer interrupt service program is shown in Figure 4-4

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