Hierarchical control strategies for multi-mode steering system of emergency rescue vehicle

It is difficult for the traditional emergency rescue vehicles (ERVs) to pass through narrow and complicated areas quickly, which leads to the ERVs missing the best time to rescue disasters seriously. How to improve the trafficability and mobility of vehicles effectively in narrow and complex areas has become an urgent technical demand for the ERVs. In this context, this paper proposes a multi-mode steering system to realize four steering modes of the ERVs. A fire rescue prototype vehicle is developed, and its multi-mode steering system is designed in detail. The hierarchical control strategies of the multi-mode steering system consist of the upper controller and the lower controller. The upper controller is responsible for assigning the steering angles of four wheels of the ERVs based on the Ackerman principle. The lower controller is used to control the ERVs to turn four wheels independently based on the electro-hydraulic fractional order PID (FOPID) control strategy, and then the parameters of the FOPID controller are optimized by the adaptive clonal selection algorithm. The multi-mode steering system proposed was tested on the homemade fire rescue prototype vehicle. The numerical simulations and experiments were conducted to verify the effectiveness of the proposed multi-mode steering system.