Digital Control for Engine Bleed Air

As modern control systems become more demanding and complex and the optimum control algorithm becomes more elusive, it becomes obvious that the versatility of control algorithm construction and modification in software is far superior to analog circuit implementations. A digital microprocessor based electronic control system has been developed for temperature control of engine bleed air on the B-1B bomber. The Engine Bleed Air Control System (EBACS) provides pressurized, temperature controlled air to various subsystems on the aircraft. This paper addresses the unique approach used in controlling a bleed air system having major gain variations (over 500 to 1) and major system-element time-constant variations (over 5 to 1) within the flight envelope, while still maintaining specified response times and stability margins.