Is There A Large Deviation in The Test Data Of The Electric Chassis Dynamometer? Guidelines For Torque Sensor Calibration, Inertia Matching, And Environmental Interference Investigation

The following is a systematic troubleshooting and solution guide for large deviations in test data of electric chassis dynamometers, covering key aspects such as torque sensor calibration, inertia matching, and environmental interference：

1, Calibration of torque sensor
①Pre calibration inspection
Physical state: Confirm that the sensor has no mechanical deformation, loose connectors, or damaged cables.
Zero drift: When disconnecting the load, observe whether the zero output is stable (error should be<± 0.1% FS).
Temperature compensation: Record the ambient temperature. If it exceeds the sensor calibration range (usually 10 ℃~50 ℃), recalibration is required.
② Calibration process
Static calibration:
Apply known torque using standard weights or hydraulic loading devices, covering 20%, 50%, 80%, and 100% of the measuring range.
Record the linear relationship between input and output values, and calculate the nonlinear error (target ＜ ± 0.2% FS).
Dynamic calibration:
Apply a sine wave load through an exciter and test the frequency response (bandwidth ≥ 100Hz).
Check the phase delay and amplitude attenuation to ensure that the dynamic characteristics meet the requirements.
Repeatability verification: When loading the same torque multiple times, the standard deviation should be less than 0.1% FS.
③Common problem handling
Zero offset: Perform zero calibration again or replace the sensor.
Nonlinear error: Segmented linear fitting or replacement of high-precision sensors (such as strain gauge sensors).
Temperature drift: Enable the built-in temperature compensation module or install a constant temperature box.

2, Inertia matching optimization
① Inertia calculation and verification
Theoretical inertia: Calculate the equivalent moment of inertia based on vehicle parameters (mass, center of mass position) (formula: J=m × r ², including tires, flywheel, etc.).
Actual inertia measurement: During no-load operation, the actual inertia of the system is measured using the step response method or frequency scanning method.
Matching error: When the difference is greater than 5%, the flywheel group or software compensation coefficient needs to be adjusted.
②Dynamic inertia compensation
Real time monitoring: Collect the speed change rate (d ω/dt) during testing and dynamically correct the inertia deviation.
Software algorithm: Use Kalman filtering or Model Predictive Control (MPC) to optimize inertia estimation.
③Mechanical system inspection
Bearing friction: Insufficient lubrication can result in additional loads, requiring cleaning and the addition of specialized grease.
Transmission efficiency: The belt/chain transmission needs to be tightened regularly, and the gearbox oil needs to be replaced (recommended every 500 hours).

3, Environmental interference investigation
① Electromagnetic interference (EMI)
Shielding measures: The sensor cable adopts double-layer twisted shielded wire with a grounding resistance of less than 4 Ω.
Filter circuit: Install a low-pass filter (cut-off frequency ≥ 1kHz) at the signal input end.
Isolation transformer: Configure an isolation power supply for the dynamometer power supply system to reduce grid noise.
②Temperature and humidity
Temperature control system: The laboratory temperature is controlled at 20 ± 2 ℃, and the humidity is maintained at 40%~60%.
Thermal expansion compensation: Correction of thermal expansion coefficient for metal components such as shafts and brackets.
③ Vibration and impact
Isolation platform: Use rubber isolation pads or active isolation systems, with vibration amplitude less than 0.5g.
Structural reinforcement: Ensure sufficient rigidity of the dynamometer base to avoid resonance (modal testing frequency>200Hz).

4, Comprehensive verification and maintenance
①Repeatability test: Run the same operating conditions continuously for 3 times, and the data fluctuation should be less than ± 0.5%.
②Comparative verification: Cross compare with another high-precision device (such as a torque meter).
③ Log recording: Save calibration parameters, environmental data, and raw signal waveforms for easy traceability and analysis.

5, Recommended Tools and Resources
Calibration equipment: high-precision torque standard machine (accuracy ≥ 0.05%), laser tachometer.
Data analysis software: MATLAB/Simulink (dynamic modeling), LabVIEW (real-time monitoring).
Standard specifications: Refer to ISO 16802 (dynamometer calibration) and GB/T 18385 (electric vehicle testing).
By systematically executing the above steps, testing errors can be significantly reduced to within ± 1%. If the problem persists, it is recommended to contact the equipment manufacturer for in-depth diagnosis or return to the factory for repair.