Development of Air Supply Controller for FCV Based on Model-Based Development Approach

In Toyota’s 2nd generation FCV, an electric turbo-type air compressor has been adopted for downsizing and cost reduction. Automotive Fuel Cell applications present several challenges for implementing a turbo-type air compressor. When operating a fuel cell in high-temperature or high-altitude locations, the FC stack must be pressurized to prevent dry-up. The flow rate vs pressure conditions that the FC must pass through or in some cases operate at are typically within the surge region of a turbo-type air compressor. Additionally, Toyota requires quick air transient response (< 1 sec) for power generation, energy management, and FC dry-up prevention. If the turbo-type air compressor is not precisely controlled during quick transients, it can easily enter the surge region. To solve the above issues, we developed a new air supply controller which can avoid compressor surge by controlling 3 variables, ‘FC stack air flowrate’, ‘FC stack air pressure’, and ‘FC stack air Bypass’ independently with high accuracy. The controller was designed using a model-based development approach. At first, the physical characteristics of the air systems compressor, valves, pipes, and FC stack were modeled and integrated into a system level simulation that can run real-time on-board the vehicle Engine Control Unit (ECU). Next, the feedforward and feedback (PI) control were developed by implementing inverse models of the air system component equations. We confirmed that this control development approach could achieve Toyota’s air supply control performance requirements and prevent turbo-type air compressor surge.