A Design Scheme for Intelligent Vehicle Power Distribution System

Various special vehicles often have oil leakage problems during use, resulting in waste of lubricating oil and fuel, and consuming the power and work efficiency of special vehicles. Therefore, a system should be designed to solve this problem. The vehicle intelligent power distribution system based on embedded technology, dual redundant CAN bus and LIN bus can realize the intelligent and digital management of the vehicle power distribution system. It can solve the current problems

1 Hardware Design of Intelligent Power Distribution System

The power distribution system is divided into three parts: power distribution terminal, intelligent power distribution manager and vehicle management terminal, as shown in Figure 1. The power distribution terminal is mainly used for status monitoring of 28 V equipment.

Since the power of the electrical equipment of special vehicles is relatively small, a fast MOSFET with low on-resistance is used inside the power distribution terminal to control the on and off of the electrical equipment. And current, voltage detection and short-circuit protection technology are used to realize the status monitoring of electrical equipment, automatic protection of faults and complete isolation of faults. In addition, the power distribution terminal has a storage memory function, which can memorize the recorded information when the equipment fails. In order to realize the digitalization of remote control and distribution system, the power distribution terminal adopts the controller LPC935 and the low-cost and easy-to-develop LIN bus. Since special vehicles have a large number of inductive loads, the impact current at startup is too large, and the current may exceed 5 to 10 times the rated current in an instant. The power distribution terminal adopts a current limiting startup method. Considering the large number of electrical equipment in the whole vehicle, the power distribution terminal adopts a modular design. One main electrical equipment is equipped with a distribution terminal, and the intelligent distribution manager is responsible for managing each distribution terminal.

The intelligent power distribution manager is mainly responsible for managing the power-consuming equipment at the power distribution terminal and monitoring the operating status of the power-consuming equipment. At the same time, the intelligent power distribution manager provides dual redundant CAN channels for data communication with other management terminals of the vehicle, thereby realizing digital management of the entire vehicle electrical system.

The main parts of the intelligent power distribution manager include: keyboard and touch screen input, LCD display, dual redundant CAN interface and LIN interface, I/O input, output, test, configuration and fault detection interface and backup information storage. Due to the complex functions of the intelligent power distribution manager, considering the real-time control and the large number of power-consuming devices, the 32-bit microprocessor LPC2119 is used on the hardware platform. LPC2119 has dual CAN controllers, two UARTs, rich I/0 resources and built-in RAM and FLASH memory. The touch screen uses the ADS7846 controller, the LCD selection supports touch screen operation of the TFT true color screen, the information storage uses 8 KB ferroelectric FLASH, and the keyboard uses a dedicated keyboard management chip. On the software platform, the real-time multi-tasking operating system μC/OS-Ⅱ is selected.

2 Software Design of Vehicle Intelligent Power Distribution System

2.1 Mechanism and principle of power distribution terminal application software implementation

The program processing flow of the power distribution terminal is shown in Figure 2.

The power distribution terminal software uses four A/D channels to collect the voltage at the input, the voltage, current and temperature at the output, and filters the collected digital quantities, thereby realizing overvoltage, undervoltage, overcurrent and temperature fault protection for electrical equipment. Short circuit protection uses hardware processing. If a short circuit is detected, the hardware automatically shuts down the MOSFET tube and transmits the short circuit signal to the I/O input port of the microcontroller so that the microcontroller can identify and judge the short circuit. The external control interface uses I/O input detection, and digital filtering is used for external control signals. The information backup of the power distribution terminal is stored in the internal memory of LPC935. In order to prevent the operating parameters from fluctuating near the set parameter points, the software uses parameter setting point regression processing.

In order to realize the digital output of the distribution terminal and the digital control of the distribution system, the distribution terminal adopts LIN bus communication, and the standard LIN 1.2 protocol is adopted in the LIN application layer protocol. Since the LIN bus belongs to the complete master-slave mode, in order for the intelligent distribution management to correctly access each distribution terminal, the automatic address allocation processing method is adopted when the system is powered on, and the distribution manager allocates a unique address to each terminal. In terms of software, LIN communication data adopts CRCl6 check to ensure the normal operation of the equipment.

2.2 Mechanism and Principle of Distribution Manager Application Software Implementation

The system uses the real-time multitasking operating system μC/OS-Ⅱ as the software platform of the power distribution manager. μC/OS-Ⅱ has open source code, small kernel, convenient transplantation and easy development. Each function of the power distribution manager can be implemented as an independent task, which greatly enhances the reliability and stability of the system software.

2.2.1 Design of power distribution manager application software

How the whole system coordinates its operation is shown in Figure 3.

The software of the embedded power distribution management terminal mainly realizes the functions of reading and setting equipment parameters, human-computer interaction, monitoring of power equipment, CAN, LIN communication data transmission, etc. The reading and setting functions of equipment parameters provide on-site modification of equipment parameters, which can also be modified through the remote monitoring terminal. The authentication information and equipment parameters are stored in the ferroelectric FLASH memory. The system uses a 4×4 keyboard, touch screen and LCD display as the input and output interface of system information.

2.2.2 Mechanism and Principle of Dual CAN Redundancy

In order to ensure the stability and reliability of the digital management of the vehicle electrical system, the external communication interface of the power distribution system adopts a CAN bus with stable performance and reliable operation. At the same time, in order to ensure the reliability of the communication of the vehicle electrical system and the handling of abnormalities, the power distribution system adopts a dual redundant CAN bus. The dual CAN redundant communication flow chart is shown in Figure 4.

The CAN bus communication program includes two functional blocks: data transmission and bus management. The functions implemented by the data transmission module include CAN initialization, CAN filter design, CAN message sending and CAN message receiving.

The functions implemented by the bus management functional block are mainly bus detection, judging whether there is a fault in CAN. If there is a fault, it will enter another bus detection; if the redundant bus is good, the redundant bus communication will be used.

CAN communication data is divided into the reception of command data, the response to commands, and the automatic reporting of fault status.

The reception and processing of command data mainly receives commands from other management terminals of the vehicle and performs comprehensive management of power-consuming equipment. When the power distribution manager detects a power-consuming equipment failure, it automatically reports it to other management terminals to achieve comprehensive management and digitization of vehicle power distribution. At the same time, the priority of the power-consuming equipment can be set, and the power distribution manager reasonably controls the power-consuming equipment according to the set priority.

When sending messages to other management terminals, fill the message content into the CAN sending buffer according to the CAN protocol format, start the sending command, and send the message. If it cannot be sent successfully, the bus fault processing is carried out, and the redundant channel is automatically called after the waiting timeout, and the redundant channel is used for sending. If the redundant channel also fails, the fault processing is entered, the fault alarm is issued and the message is exited.

3 Conclusion

The design results of this system make up for the shortcomings of traditional vehicle power distribution systems, realize the digitization and intelligence of the entire vehicle power distribution system, and have a humanized side. This design breaks through some rigid programs of the old system, and the new program allows the machine to run more quickly.