Modelling and parameter identification of friction coefficient for brake pair on urban rail vehicle

ABSTRACT

The uncertainty of friction coefficient brings error to braking control and force calculation on urban rail vehicle. A dynamic friction model using exponential function was developed. The undetermined parameters under different operating conditions were identified by using nonlinear least square method, based on the test data from a full-scale braking test rig. The coefficient $\gamma$ reflects the decreasing rate of the friction coefficient with the increasing velocity. The parameter $\alpha$ relates to the asymptote of friction coefficient. The term $\alpha +\beta$ reflects the static friction coefficient. The estimated errors of the parameters are within 10⁻⁴-10⁻². During the steady braking stage, the calculated curves are in good agreement with the measured ones, and their squared errors are within 10^–5. The parameter $\gamma$ under wet condition is bigger than that under dry condition, while $\alpha$ is smaller than that under dry condition. The term $\alpha +\beta$ is close to the measured static friction coefficient.

KEYWORDS:

• Urban rail vehicle
• brake pair
• friction coefficient
• parameter identification
• nonlinear least square
• rig test

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Ministry of Science and Technology of China [National Natural Science Foundation of China Grant No.U1534205]; [National Major Project of Scientific and Technical Supporting Programs of China during the 12th Five-year Plan Period Grant No.2015BAG13B01-11].