Multi-application controls: Robust nonlinear multivariable aerospace controls applications

This viewgraph presentation describes the general methodology used to apply Honywell's Multi-Application Control (MACH) and the specific application to the F-18 High Angle-of-Attack Research Vehicle (HARV) including piloted simulation handling qualities evaluation. The general steps include insertion of modeling data for geometry and mass properties, aerodynamics, propulsion data and assumptions, requirements and specifications, e.g. definition of control variables, handling qualities, stability margins and statements for bandwidth, control power, priorities, position and rate limits. The specific steps include choice of independent variables for least squares fits to aerodynamic and propulsion data, modifications to the management of the controls with regard to integrator windup and actuation limiting and priorities, e.g. pitch priority over roll, and command limiting to prevent departures and/or undesirable inertial coupling or inability to recover to a stable trim condition. The HARV control problem is characterized by significant nonlinearities and multivariable interactions in the low speed, high angle-of-attack, high angular rate flight regime. Systematic approaches to the control of vehicle motions modeled with coupled nonlinear equations of motion have been developed. This paper will discuss the dynamic inversion approach which explicity accounts for nonlinearities in the control design. Multiple control effectors (including aerodynamic control surfaces and thrust vectoring control) and sensors are used to control the motions of the vehicles in several degrees-of-freedom. Several maneuvers will be used to illustrate performance of MACH in the high angle-of-attack flight regime. Analytical methods for assessing the robust performance of the multivariable control system in the presence of math modeling uncertainty, disturbances, and commands have reached a high level of maturity. The structured singular value (mu) frequency response methodology is presented as a method for analyzing robust performance and the mu-synthesis method will be presented as a method for synthesizing a robust control system. The paper concludes with the author's expectations regarding future applications of robust nonlinear multivariable controls

It is not how many votes you get, but also where you get them. Territorial determinants and institutional hurdles for the success of ethnic minority parties in post-communist countries

Electoral rules have long been held as important for the success of new political parties, but research has neglected the dimension of territory in this equation. This article argues that the territorial structure of social groups, in interaction with the electoral system, makes a crucial difference for the ability of new parties to enter parliament. In district-based electoral systems, social groups that are highly concentrated face much lower hurdles with an own party than groups that are spread throughout the country. The argument is tested on a novel database on ethnic minority groups from post-communist countries in Europe, including 123 minorities in 19 countries. To test hypotheses with complex interaction effects and binary variables, Qualitative Comparative Analysis appears as the most suitable method. After controlling for size and special minority-relevant provisions in the electoral systems, there is strong confirmation for the hypothesised effect