Robustness assessment for flight control system of an oceanographic unmanned aerial vehicle

A post-design robustness assessment for the longitudinal flight control system of an oceanographic unmanned aerial vehicle （UAV） is presented in this paper. Two novel systematic approaches of generating the linear fractional transformation （LFT） model directly from nonlinear equations are proposed for this particular robustness analysis problem. The closed-loop system combined with each controller is used to determine combinations of aerodynamic parameters that result in worst-case performance. Classical simultaneous gain and phase margin stability metrics currently used in the aerospace industry are introduced for the certification of robustness of this uncertain multivariable system. The results show that the control system remains stable and achieves desired performance for all possible parameter variations over a specified range in both frequency domain and time domain.

PM Diagram of the Transfer Function and Its Use in the Design of Controllers

This paper presents an enhanced Root Locus diagram that consists of the representation of the phase and the magnitude of the transfer function G（s） of a system. The magnitude is represented in decibels and the phase is represented by colors. It also presents how to use it to calculate different kinds of controllers. An important characteristic of this diagram is that permits to read the phase and the gain margins directly and the imaginary axis cut represents the Bode diagram. It is also possible to put the grid with damping ratio ξ and frequency ωn.

Consensus control and feedback graph co-design for MIMO discrete-time multi-agent systems

This paper studies consensus control for multi-input/multi-output(MIMO)discrete-time multi-agent systems(MASs).It makes use of the novel idea of resource allocation in designing both the communication graph and feedback controller.The weakest consensusability condition is obtained for MASs over both directed and undirected graphs,which extends the existing results to MIMO discrete-time MASs.Explicit synthesis procedures are also developed.Our work demonstrates the importance of the graph and controller co-design based on resource allocation for MIMO discrete-time MASs.

Analysis and Design of Scaling Optimal GPM-PID Control with Application to Liquid Level Control

In this paper, a new analysis and design method for proportional-integrative-derivative （PID） tuning is proposed based on controller scaling analysis. Integral of time absolute error （ITAE） index is minimized for specified gain and phase margins （GPM） constraints, so that the transient performance and robustness are both satisfied. The requirements on gain and phase margins are ingeniously formulated by real part constraints （RPC） and imaginary part constraints （IPC）. This set of new constraints is simply related with three parameters and decoupling of the remaining four unknowns, including three controller parameters and the gain margin, in the nonlinear and coupled characteristic equation simultaneously. The formulas of the optimal GPM-PID are derived based on controller scaling analysis. Finally, this method is applied to liquid level control of coke fractionation tower, which demonstrate that the proposed method provides better disturbance rejection and robust tracking performance than some commonly used PID tuning methods.