Computer-aided design of classical linear compensators with application to aerospace

A new Matlab function based on a versatile compensator design approach is developed.This function allows design of lead-lag, PID, proportional plus rate feedback, proportional-integral plus rate feedback, and nth order linear compensators.The primary inputs to this function are the plant transfer function and the desired closedloop behavior in terms of an nth order transfer function.The output is the particular compensator parameters.The unified design approach is primarily based on minimizing a mean-squared error type objective function.This minimization gives the compensator parameters in terms of a set of linear simultaneous algebraic equations.This solution method requires the user to input such parameters as the lower and upper limits of frequency range of interest;such parameters are automatically determined by the use of numerical optimization.The design method and the associated software are demonstrated by solving a flexible satellite problem, and the results are compared with those obtained by two other methods reported in the open literatures.

Classical biological control program for the mealybug Oracella acuta in Guangdong Province, China

The mealybug Oracella acuta, native to the southeastern US, was accidentally introduced into slash pine plantations in Guangdong Province in China in 1988. A classical biological control program was initiated in 1995, and the parasitoids Allotropa oracellae, Acerophaus coccois, and Zarhopalus debarri were imported from the US. A total of 19 972 parasitized mealybugs were shipped to China from 1996-2004, from which 15 430 wasps emerged, 12 933 of which were the three target species. Efforts to establish a mass-rearing program for the parasitoids in China failed. Five field release sites were established, and 6 020 parasitoids were released. Only 118 individuals of the three imported species were collected during establishment checks, although several wasps were collected 1-2 years after the last parasitoid release. Over 2 000 Anagyrus dactylopii, a cosmopolitan parasitoid, emerged from the parasitized mealybugs collected, a majority from the Taishan area near the site of the original introduction ofO. acuta. To date the imported parasitoids have failed to establish, and natural enemies have not noticeably reduced mealybug populations.

Exact Boundary Controllability on a Tree-Like Network of Nonlinear Planar Timoshenko Beams

This paper concerns a system of equations describing the vibrations of a planar network of nonlinear Timoshenko beams. The authors derive the equations and appropriate nodal conditions, determine equilibrium solutions and, using the methods of quasilinear hyperbolic systems, prove that for tree-like networks the natural initial-boundary value problem admits semi-global classical solutions in the sense of Li [Li, T. T., Controllability and Observability for Quasilinear Hyperbolic Systems, AIMS Ser. Appl. Math., vol 3,American Institute of Mathematical Sciences and Higher Education Press, 2010] existing in a neighborhood of the equilibrium solution. The authors then prove the local exact controllability of such networks near such equilibrium configurations in a certain specified time interval depending on the speed of propagation in the individual beams.