Design of Controller Development Device Based on AD5336 Chip to Realize Automobile Anti-lock Braking System

Anti-lock Braking System (ABS) can effectively prevent the vehicle from locking the wheels during the braking process, so as to avoid the danger of steering failure and tail drift caused by the locking of the wheels, so as to ensure the safety of the vehicle. safe braking. Among them, the controller (ie Electronic control unit, ECU) is the control core of the entire ABS and the main key in the development process of ABS. The traditional ABS development process requires a large number of vehicle road tests to verify the control software functions of ABS. Limited by manpower and material resources, the development cycle of ABS is quite long.

introduction

Anti-lock Braking System (ABS) can effectively prevent the vehicle from locking the wheels during the braking process, so as to avoid the danger of steering failure and tail drift caused by the locking of the wheels, so as to ensure the safety of the vehicle. safe braking. Among them, the controller (ie electronic control unit, ECU) is the control core of the entire ABS and the main key in the development process of ABS. The traditional ABS development process requires a large number of vehicle road tests to verify the control software functions of ABS. Limited by manpower and material resources, the development cycle of ABS is quite long.

Based on Infineon’s XC164CS and ADI’s AD5336 chip, this paper designs a simple ABS controller development device, which can test most of the functions of the ABS control software without the participation of the whole vehicle or even the brakes. development provides great convenience.

System components

As shown in Figure 1, the designed ABS controller development device mainly includes three parts: one is the driving/braking simulation controller, which is mainly used to simulate the driving and braking of the wheels; the other is the hardware equipment part, including four representative The ring gear of the wheel and the four motors that drive the four ring gears each, four rotational speed sensors, a control panel for various controls, and LED indicators for the status of each solenoid valve, ABS motor, and warning lights ;The third is the GUI interface software running on the upper computer PC, which is mainly used for various parameter settings, as well as collecting and monitoring various states of the ABS controller during real-time operation, including the original wheel speed, reference vehicle speed, and the state of each solenoid valve. Wait.

 

Drive/Brake Analog Controller Design

The main core of the ABS controller development device of this design is the design of the drive/brake simulation controller. The functions that must be realized include:

(1) The ring gear can be stably operated at a certain speed according to the setting;

(2) It can quickly adjust the speed of the ring gear with different accelerations and decelerations to simulate the wheel speed changes when the vehicle brakes on different road surfaces and different working conditions, and the accuracy of speed regulation is high;

(3) It can communicate in real time with the ABS controller developed by the target and the GUI software of the host computer.

According to the functional requirements, the circuit block diagram of the designed drive/brake analog controller is shown in Figure 2.

The main control chip selected is Infineon’s 16-bit microcontroller XC164CS, and its main advantages are as follows:

(1) The operation speed is fast. Single clock cycle instruction execution speed, the maximum allowed clock frequency is 40MHz;

(2) The memory capacity is large. There are 128KB rewritable Flash for storing codes and 2KB dual-port RAM+2KB data SRAM for storing data variables on-chip;

(4) It is convenient to download and debug the program. It has an on-chip bootstrap bootloader, and the program can be downloaded through the serial port. It has an on-chip debugging interface (OCDS), and can perform single-step and breakpoint debugging of the program through Keil-C166 and other compilers.

These advantages of XC164CS can fully meet the requirements of high-speed real-time control of this design.

Since XC164CS requires two core voltages, 5V and 2.5V, to work normally, TLE7469GV52, which can generate these two voltages, is used as a power management chip to simplify the circuit design. TLE7469GV52 is Infineon’s LDO power chip, which has low Features such as voltage alarms, overtemperature and overload protection, and watchdogs provide an excellent power management solution for this design.

For motor control, this design uses a voltage-regulated DC motor, and AD5336 from ADI is used as the D/A output chip to drive the motor. Figure 3 is the functional block diagram of AD5336. The chip is characterized by four on-chip One independently controlled 10-bit precision D/A output channel, low power consumption, using parallel interface, the D/A conversion update time only needs 6μs, which can fully meet the requirements of high precision and fast speed regulation of the motor in this design. Each D/A channel on the chip has a rail-rail output buffer amplifier, which has a strong load capacity, so it can directly drive a DC motor with voltage speed regulation without any peripheral circuit. This method can greatly simplify the motor drive circuit. , and also simplifies the design of the motor control program.

In this design, a passive magnetoelectric wheel speed sensor is used, and its output is a sine signal. In the wheel speed processing module, LM139 is used as a voltage comparison chip to realize the conversion from a sine signal to a square wave signal. CC2 of XC164CS is used. The module captures the wheel speed pulse, monitors the speed of the four ring gears in real time, and realizes the speed feedback control of the ring gear motor, thereby ensuring the accuracy of the speed control of the ring gear. The CAN interface is designed to meet the three-party communication between the drive/brake simulation controller, the target-developed ABS controller and the host computer GUI software in this design. OCDS interface and ASC interface are designed for the convenience of program download and debugging.

software design

The core principle of this development device is to use the drive/brake simulation controller to simulate the brake, and to convert the intervention of the ABS controller developed by the target to the brake, that is, by controlling each solenoid valve to realize actions such as pressurization, decompression, pressure maintenance, etc. To send the corresponding control information to the drive/brake simulation controller. According to the control information sent by the ABS controller, the drive/brake simulation controller simulates the actions of pressurizing, decompressing, and maintaining the pressure of the brake to adjust the speed of the ring gear motor. The ABS controller obtains the speed sensor from the ring gear. The wheel speed signal, and then continue the ABS brake control, so as to achieve the purpose of detecting the ABS brake control software.

In addition, the influence of different road surfaces is also considered in the software design, that is, when braking on roads with different adhesion coefficients, the driving/braking simulation controller reflects the changes in the speed of the ring gear motor by simulating the action of the brake. , in this design, the driving/braking simulation controller can simulate the braking on four kinds of road surfaces: high-adhesion road, low-adhesion road, road with sudden change in adhesion coefficient (ie, split road) and road with separation coefficient of adhesion (ie, butt road). condition.

According to the above software design, the working process of the development device and the verification of the ABS controller are briefly described below.

(1) Connect the ABS controller developed by the target to the system and power on, the drive/brake simulation controller will analyze and process the data packets on the CAN bus in real time. When receiving the speed setting and adjustment commands of the GUI software, The drive/brake analog controller makes the ring gear motor rotate at a certain speed according to the corresponding settings. The ABS controller should calculate various parameters such as wheel speed, wheel acceleration and deceleration in real time, and send them to the CAN bus. superior. The GUI interface prints this information to the screen in the form of drawing, etc., so that it can be observed in real time whether the various calculations of the ABS controller are accurate.

(2) Select a road surface and issue a braking command through the GUI interface. The drive/brake simulation controller first simulates conventional braking and brakes the ring gear motor at a fixed deceleration. At this time, the ABS controller The ABS braking intervention should be judged by detecting the signal of the ring gear speed sensor, so as to send the corresponding control information to the CAN bus, and the drive/brake motor will simulate the action of the brake according to the control information to adjust the speed of the ring gear motor. By observing the speed change of the ring gear and the LED indicators, and observing various calculation results of the ABS controller obtained on the GUI interface, including the wheel speed curve, solenoid valve status, etc., it is possible to verify whether the control process of the ABS controller is correct. correct.

Epilogue

Based on the high-performance 16-bit microcontroller XC164CS and the high-precision D/A conversion chip AD5336, this paper successfully designs and develops a drive/brake analog controller that can simulate the wheel speed changes during vehicle braking, and uses the motor to drive the ring gear. The method simulates the wheel operation, and uses simple LED indicators to indicate various solenoid valve states and ABS motor states, which can verify most of the control functions of the ABS controller developed by the target. For the newly developed ABS controller, it is only necessary to control it The software can be modified appropriately for the operation of the development device without the participation of the whole vehicle or the brakes, and without the need for a large number of road experiments, thus greatly reducing the ABS development cost and shortening the ABS development cycle.

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