Digital Controller for Active Aeroelastic Controls

摘要

A high-speed digital controller for aeroelastic controls was designed and made. The purpose was to minimize adverse phase lag which is inevitably produced by the CPU time of digital processing. The delay deteriorates control performances on rather rapid phenomena like aircraft flutter. With fix-point operation the controller realized 417 microseconds of throughput time including the A/D and D/A conversion. This corresponds to a high sampling rate of 2.4 kHz. The controller furnishes two channels, each of which can be implemented with up to the eighth order control laws allowing the coupling terms. Control laws can be loaded by changing coefficients for multiplication in its expansion form. These coefficients are calculated and transferred by a peripheral computer through the GP-IB busline. At the stage of D/A conversion, the number of bit-shifts associated with a scaling is made programmable to avoid overflow and to lessen inaccuracy due to the truncation error. A sample period is also selectable through the GP-IB busline. This period ranges from 1 millisecond to 500 microseconds. In the appendix, a program is presented for converting from the continuous transfer function in the Laplace domain to a discrete transfer function in the z-domain with the aid of Tustin's approximation.