LMI-based observer design on a power-split continuously variable transmission for off-road vehicles

Power-split continuously variable transmissions (CVTs) represent a promising technology to improve the fuel economy of high-power off-road vehicles such as construction and agricultural machines. Power-split CVTs are capable of keeping the combustion engine running within the optimal range in terms of fuel economy and performance. There are characterized by the combination of a traditional mechanical transmission and a continuously-variable transmission. A CVT power-split design for high-power vehicles combines the advantages of pure hydrostatic drives at low speeds with the high efficiency of power split drives at higher speeds. This guarantees smooth variations of the transmission-ratio with high efficiency and also high power density, maximum tractive force at low speeds. The full automatic control of power-split CVTs require a large number of measurable values. To ensure the reliability and safety of powertrains at least a two-channel redundant system for the measuring channels is required. In this paper, a general model-based approach for analytical redundancy based on Takagi-Sugeno (T-S) fuzzy observers by using LMI-based conditions for the design process is developed. It has been shown by simulation studies and experimental results that this approach can be used to reconstruct a selection of measurable values such as the hydrostatic pressure under varying load conditions and transmission modes.