Observer-based estimation of pressure signals in hydrostatic transmissions

Hydrostatic transmissions, also called hydrostatic gears, have been widely used in mobile working machines and off-road vehicles such as construction and agricultural machines. This kind of transmission offers important advantages like continuously variable transmission with high power density, maximum tractive force at low speeds and reversing without changing gear. The automatic electronic control of hydrostatic transmissions, which depend on a number of measurable values, has become more common in industrial practice. To ensure the reliability and safety at least a two-channel redundant system for the measuring channels is required. In this paper, a general model-based approach using a Takagi-Sugeno (T-S) fuzzy observer for analytical redundancy of the oil pressure measuring process in hydrostatic transmissions is developed. It has been shown by experimental results that this approach can be used to estimate the pressure values under varying load conditions and different driving situations.