Abstract: To exactly track the ride height of bus and satisfy the control demand of air suspension, a height tracking circuit based on the inductance sensor is designed. The inductance of sensor and the designed tracking circuit are jointly controlled by the single chip for the inductance charge-discharge, and the single chip calculates the time constant of different inductance to indirectly obtain the real-time bus height. Temperature compensation and components of low temperature-drift property are adopted to fit the ambient temperature change of the bus. Additionally, a special filtering software is developed to track the dynamic ride height exactly and simultaneously. According to the test results, the height tracking system comes to be stable soon, and the change of ride height is about 1 mm; the relative error is about 1.9% and the max value of tracking error is less than 5 mm when the ambient temperature rises from 30 ℃ to 80 ℃. So, the designed tracking circuit can ensure the veracity of ride height control.

Key words: Bus, Electronically controlled air suspension(ECAS), Ride height, Tracking circuit, Contourlet transform, Shape from shading, Three dimensional defect detection