Fault location and interference elimination of CAN bus of new energy buses

Ankai Bus Fault Diagnosis Record

    Ankai New Energy Bus is one of the earliest domestic companies to develop and mass-produce electric buses. It was the first to be listed in the national electric vehicle bulletin, and the number of bulletins ranked first in the country. At present, its domestic market share has reached more than 70%, and it has been exported in large quantities to Europe and the United States, becoming a leading brand in the industry. The reason why Ankai has gained the trust of a wide range of users is that the company has extremely high standards for driving safety and reliability. In response to the common problem of electromagnetic interference on the CAN bus of new energy buses, Ankai cooperated with Guangzhou Zhiyuan Electronics Co., Ltd. to use the CANScope-Pro professional version of the CAN bus analyzer to successfully locate the fault, eliminate interference, and conduct reliability tests to ensure the stable operation of Ankai's new energy buses.

● Spectrum analysis accurately locates the root cause of the fault

    New energy buses are different from traditional buses. They use batteries and capacitors to store energy, and then convert it into AC through inverters to drive the motors to drive the vehicles. When the bus accelerates or decelerates, the huge current changes generated by the inverter form strong magnetic field interference, which is coupled to the nearby CAN bus through the power cable, causing communication delays and interruptions, and even causing equipment to freeze or damage. As a result, the dashboard display lags and control fails, seriously affecting the safety of people's lives and property.

CANScope-Pro uses FFT spectrum analysis statistics to accurately locate the interference source frequency and the frequency of the inverter.

   
● Anti-interference solution
In response to the customer's rectification goals, Zhiyuan Electronics' CANScope-Pro analysis report proposed three thorough solutions:
1. The CAN bus interface of the customer's subsequent R&D products all use the CTM1051 isolation transceiver module to achieve power and signal isolation and limiting, and prevent strong interference signals from entering the main circuit and causing the controller to crash;
2. Replace the current wire material with a shielded twisted pair with a denser lay to improve the cable's anti-interference ability;
3. For buses that have already left the factory, install a CANbridge isolation bridge to ensure the safe operation of the vehicle.
Through rectification, the interference signal has been greatly reduced, and through CANScope-Pro spectrum analysis, it can meet the requirements of safe operation.

● Reliability test improves system robustness
    In order to further improve the reliability of the CAN bus system of Ankai new energy buses, Zhiyuan Electronics used CANScope-Pro to develop a comprehensive reliability test for Ankai:

 Bit width tolerance test: verify whether the bus CAN node will crash under the condition of baud rate fluctuation;
 Message stress test: verify whether the bus CAN node will crash under the condition of large data load;
 Error baud rate stress test: verify whether the bus CAN node will crash under the condition of error baud rate;
 Anti-interference ability test: verify whether the bus CAN node will crash under high-intensity interference;
 Bus short circuit test: verify whether the bus CAN node can self-recover in the case of bus short circuit;
 Bus open circuit test: verify whether the bus CAN node can self-recover in the case of bus open circuit;
 Capacitive reactance increase stress test: verify the maximum capacitive reactance value that the bus CAN node can adapt to;
 Bus network impedance test: verify the maximum impedance value that the bus CAN node can adapt to;
 Short circuit to positive and negative power supply or ground: verify whether the bus CAN node can self-recover when the bus is short-circuited to positive and negative power supply or ground;
 Terminal resistance change stress test, etc.: verify the terminal resistance range that the bus CAN node can adapt to.
These reliability tests verified the stress resistance and self-recovery capabilities of the bus CAN bus equipment under these extreme conditions. Through the joint efforts of ZHIYUAN Electronics and Ankai, the robustness of Ankai Bus's CAN bus system was comprehensively improved.

● Comprehensive and efficient localized services
    As a leading domestic CAN bus company, Guangzhou Zhiyuan Electronics Co., Ltd. is equipped with highly skilled CAN bus technical engineers in major cities across the country, which can provide customers with timely services, professional test reports and solutions.
Zhiyuan Electronics is one of the earliest companies to enter the measuring instrument industry in China. It has nearly 400 senior research and development engineers and sales and service outlets throughout the country. It not only responds to customer requirements very quickly, but also provides customized services according to the differentiated needs of industry users. We will unremittingly promote and lead the development and improvement of China's high-end instruments. We believe that the world will be different because of our existence.