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Project Information
We were involved with Bowman Power Systems from November 2001 until December 2002. We were responsible for specifying,
designing, coding and testing software for a Combined Heat and Power (CHP) product.
The product comprised a number of distributed processors (Hitachi H8S series), communicating via a CAN bus. The electronics
controlled a high speed gas turbine engine, which drove an 80kW electrical generator. The exhaust gas provided a source of heat for
a boiler.
The areas of responsibility included designing the overall software architecture, detailed design and coding of the lower level
service layers for all of the boards in the system and the design and coding of application layer software for three of the
controller boards. The implemented software operated in conjunction with a third party start inverter and the high voltage power
electronics side of the product, which were both controlled via the CAN bus.
The low level software designed provided display management, serial protocols, real-time clock services, non-volatile storage
management, event logging and I/O services. All services were designed to ensure the application layer required no knowledge of
the underlying hardware or the lower level processes.
The engine controller application comprised a number of nested state machines, which used the services provided by the lower layers.
The highest software level was the CHP application, which controlled all aspects of running the overall product. The CHP layer
controlled the engine application, which was responsible for all aspects of starting, running and stopping the engine. The engine
layer used the start inverter application to spin the engine under electrical power during the starting phase.
The user display controller application was responsible for presenting the user with information about the state of the product and
for allowing a number of settings to be controlled. It also featured an engineering diagnostics serial port that allowed any CAN bus
register in the system to be accessed. Using this feature, the system could be probed, calibrated and configured.
The remote interface controller application was responsible for receiving external control commands and for sending them to the CHP
application. A pair of MODBUS protocol ports allowed system data and statistics to be gathered. The application converted received
commands into CAN requests, allowing information from a variety of system resources to be obtained.
The electronics featured many safety features and interlocks to prevent catastrophic failure in the event of a sensor malfunction or
other system problem. The embedded software was designed to monitor the state of all of the system boards, together with all critical
parameters in real time, so that it could immediately bring the engine to a controlled stop in the event of a fault being detected.
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