Application Overview
Hello everyone! Today, I want to talk about the application of the S7-200 PLC combined with the CANopen bus in the new energy vehicle test bench. The development of new energy vehicles is progressing rapidly, and the test bench serves as the “health check center” for these vehicles, capable of detecting various performance metrics. The S7-200 PLC paired with the CANopen bus acts like an intelligent brain and an efficient neural network for this “health check center,” making the testing process more precise and efficient. Imagine various sensors acting as little guardians, quickly and accurately transmitting the collected data to the S7-200 PLC via the CANopen bus, which then analyzes and processes the data according to preset programs. Isn’t that super cool!
Hardware Configuration
The hardware configuration is the foundation of the entire project, just like laying a solid foundation before building a house. For the S7-200 PLC, I chose the CPU226 module, which is like a versatile little helper with fast speed, strong communication capabilities, and six independent high-speed counters along with two RS485 communication/programming ports, fully meeting the needs of the test bench.
For the CANopen bus, I used a communication module with a CAN interface, which is like giving the PLC a pair of “all-seeing eyes” and “listening ears,” allowing it to communicate smoothly with other devices on the CANopen network. Additionally, 120Ω termination resistors must be added at both ends of the bus, acting like a “stabilizer” to ensure the stability of data transmission. Various sensors, such as current sensors, voltage sensors, and temperature sensors, act like sensitive antennae, continuously sensing various parameters on the test bench.
Program Design Approach
Program design is a technical task that requires careful consideration. First, the functional requirements of the test bench must be clarified, such as detecting the charging and discharging performance of the battery, the speed and torque of the motor, etc. Based on these requirements, the program is divided into different functional modules, just like cutting a large cake into smaller pieces to enjoy one at a time.
For the data acquisition module, I need the sensors to collect data at regular intervals and send it to the PLC via the CANopen bus. The data processing module acts like a smart little housekeeper, classifying, organizing, and analyzing the collected data. The control module then uses the results of the data processing to control the devices on the test bench to perform corresponding actions, such as adjusting the charging and discharging current of the battery or controlling the speed of the motor.
Program Implementation
Variable Definition
Before programming, various variables must be defined, just like preparing ingredients before cooking. I defined some global variables, such as battery voltage, current, temperature, motor speed, and torque. These variables act like little boxes for storing the collected data. There are also some flag variables to indicate the operational status of the devices, such as whether the device is started or if a fault has occurred.
Main Program Implementation
The main program acts like the director of a spectacular performance, coordinating the work of various functional modules. At the start of the program, initialization settings are performed, such as setting the parameters for the CANopen bus and initializing the sensors. Then, it enters a loop, continuously calling the data acquisition module, data processing module, and control module.
NETWORK 1
// Initialization settings
LD SM0.1
CALL CANopen_Init
CALL Sensor_Init
NETWORK 2
// Main loop
LD SM0.0
CALL Data_Collection
CALL Data_Processing
CALL Control
Function Block Templates
In the traffic signal control program, the template is a clock pulse function block that generates precise clock signals, like a precise little alarm clock. However, in the new energy vehicle test bench, I used data acquisition and control function blocks. The data acquisition function block acts like a diligent little bee, regularly collecting data from the sensors and sending it to the PLC via the CANopen bus. The control function block then controls the devices on the test bench based on the results of the data processing.
// Data acquisition function block
FUNCTION_BLOCK Data_Collection
VAR_INPUT
Sensor_ID : INT; // Sensor ID
END_VAR
VAR_OUTPUT
Sensor_Data : REAL; // Collected data
END_VAR
BEGIN
// Collect data from the specified sensor
// Code implementation omitted
END_FUNCTION_BLOCK
// Control function block
FUNCTION_BLOCK Control
VAR_INPUT
Battery_Voltage : REAL; // Battery voltage
Motor_Speed : REAL; // Motor speed
END_VAR
VAR_OUTPUT
Control_Signal : BOOL; // Control signal
END_VAR
BEGIN
// Control based on battery voltage and motor speed
IF Battery_Voltage < 300 THEN
Control_Signal := FALSE; // Stop charging
ELSIF Motor_Speed > 5000 THEN
Control_Signal := FALSE; // Stop motor
ELSE
Control_Signal := TRUE; // Normal operation
END_IF
END_FUNCTION_BLOCK
Function Expansion
As the technology of new energy vehicles continues to develop, the functions of the test bench must also be expanded. For example, a battery life prediction function can be added, which analyzes historical data to predict the battery’s lifespan, like providing a “health check report” for the battery. Additionally, a motor efficiency optimization function can be added to improve the motor’s efficiency by adjusting control parameters, allowing new energy vehicles to travel further and more efficiently.
Debugging Methods
Debugging is a technical task that requires patience and attention to detail. I generally use a step-by-step debugging method, first debugging the data acquisition module to see if the data collected by the sensors is accurate. Then, I debug the data processing module to check if the results are reasonable. Finally, I debug the control module to observe whether the devices on the test bench can perform actions as expected.
During the debugging process, I also use a CAN analyzer, which can monitor the data on the bus, acting like a “data detective” to help identify the causes of communication failures. If I find issues with data transmission, I check the parameter settings of the CANopen bus and the connections of the termination resistors.
Application Expansion
In addition to the new energy vehicle test bench, the S7-200 PLC combined with the CANopen bus can also be applied in many other fields. For example, in industrial automation, it can be used to control equipment on production lines, improving production efficiency. In the intelligent transportation field, it can be used for traffic signal control and vehicle scheduling. Imagine a future city traffic system functioning like an intelligent chessboard, where vehicles and traffic lights can intelligently adjust based on real-time conditions; how cool would that be!
Troubleshooting
In practical applications, it is inevitable to encounter some faults. For example, sensor failures may lead to inaccurate data collection. In such cases, I check whether the sensor connections are loose or if the sensor is damaged. There may also be CANopen bus communication failures, such as node ID conflicts or mismatched baud rates. I check the configuration of the devices on the bus to ensure that the parameter settings are correct.
Once, the test bench suddenly stopped working, and upon inspection, I found that a sensor had failed. After replacing the sensor, the system returned to normal. Through this experience, I learned the importance of troubleshooting and gained some valuable experience.
Conclusion
Through the application of the S7-200 PLC combined with the CANopen bus in the new energy vehicle test bench, I have learned a lot and faced many challenges. However, it is these challenges that have allowed me to grow and improve continuously. I believe that as technology continues to develop, the application of the S7-200 PLC combined with the CANopen bus will become increasingly widespread across various fields.
Everyone, if you are also interested in this project, why not give it a try? Don’t be afraid to encounter problems; research more and ask others for help. I believe you will achieve great results in this field! Keep it up! 💪