Temperature dependent friction estimation: Application to lubricant health monitoring

In this work a method is presented to detect lubricant quality changes in mechanical transmissions. It is explored that the quality of the lubricant influences the friction parameters in fluid lubrication regime. An energy balance based fault detection method is proposed to detect slow changes in friction parameters. Since the properties of the lubricant depend on the temperature, the fault detector applies a temperature dependent friction model. A lubricant temperature estimator is also developed for the mechanical transmission, since in many applications the lubricant temperature is not measurable on-line. In the proposed approach the temperature of the lubricant is estimated based on the temperature of the housing, temperature of the environment, velocity and the identified parameters of the mechanical system. Experimental measurements are also presented to show the applicability of the proposed lubricant temperature observer and health monitoring algorithm.