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Advances in Flight Control Systems Part 11

Tham khảo tài liệu 'advances in flight control systems part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Acceleration-based 3D Flight Control for UAVs Strategy and Longitudinal Design 187 for the NMP nature of the system to be considered negligible. This rule implies that the system poles must lie within a circle of radius Z0 3 in the s-plane. Thus an upper bound is placed on the natural frequency of the system if its NMP nature is to be ignored. 6.3 Frequency bounds on the normal specific acceleration controller Given the results of the previous two subsections the upper bound on the natural frequency of the normal specific acceleration controller becomes n 7 L k - In V Iy 3 55 where the typically negligible offset in the zero positions in equation 45 has been ignored. Adhering to this upper bound will allow the NMP nature of the system to be ignored and will thus ensure both practically feasible dynamic inversion of the flight path angle coupling and no large sensitivity function peaks Goodwin et al. 2001 in the closed loop system. Note that given the physical meaning of the characteristic lengths defined in equations 41 through 43 the approximate zero positions and thus upper frequency bound can easily be determined by hand for a specific aircraft. It is important to note that the upper bound applies to both the open loop and closed loop normal specific acceleration dynamics. If the open loop poles violate the condition of equation 55 then moving them through control application to within the acceptable frequency region will require taking into account the effect of the system zeros. Thus for an aircraft to be eligible for the normal specific acceleration controller of the next subsection its open loop normal dynamics poles must at least satisfy the bound of equation 55 . If they do not then an aircraft specific normal specific acceleration controller would have to be designed. However most aircraft tend to satisfy this bound in the open loop because open loop poles outside the frequency bound of equation 55 would yield an aircraft with poor natural flying .