Enhanced emulation techniques for aircraft systems

The increasing electrical load demand on on-board (aircraft, marine, automotive, commercial vehicles and rail) power networks, together with the proposed embedded electrical generators introduces new challenges including the potential for engine-generator-electrical system interactions. Accurately emulating such systems is essential to enable the identification and mitigation of such interactions to ensure reliable, robust operation. In this thesis, an advanced emulation method which cancels the natural drive system dynamics using system identification is proposed, designed, simulated and demonstrated experimentally to show its performance in emulating a wide range of aircraft mechanical systems using a commercial electrical drive system. The thesis firstly examines the performance of the existing emulator system hardware, which consists of an electrical drive, real-time control platform and inline speed and torque sensors, to identify aspects of the drive behaviour which may impose a limit on the range or the accuracy of the systems being emulated. Two features of the experimental data were identified which may compromise the ability of the emulator system to emulate mechanical sources, the first is an 89ms time delay between the reference speed and the measured speed, and the second is the relatively low, 60rad/s, bandwidth of the speed controller with a significant resonant peak at approximately, 40rad/s, which significantly limit the range of frequencies which can successfully be emulated. Existing time delay compensation techniques were analysed and simulated using an experimentally validated simulation model, offering only a modest reduction in time delay. An advanced natural drive system dynamics compensator method is proposed to cancel the speed control loop characteristics and so extend the emulation bandwidth of the electrical drive-based emulator system without the need for any hardware changes or knowledge of the drive system parameters. This compensator is designed by applying parameter system identification to experimental data from the emulator drive system speed step response, and then modified to incorporate the effects of field weakening and load variations. The effectiveness of the proposed emulation approach is demonstrated by simulation and experimental emulation of a wide range of mechanical systems, with a focus on aerospace applications, including gas engine dynamics and the associated mechanical transmission effects due to a compliant drivetrain and backlash effects. The proposed emulation method is not limited to a specific mechanical system model, and is particularly suitable for the emulation of the high-speed and high-power mechanical systems.