Development of control laws for a flight test maneuver autopilot

Abstract

An autopilot can be used to provide precise control to meet the demanding requirements of flight research maneuvers with high-performance aircraft. This paper presents the development of control laws within the con- text of flight test maneuver requirements. The control laws are developed using eigensystem assignment and command-generator tracking. The eigenvalues and eigenvectors are chosen to provide the necessary handling qualities, while the command-generator tracking enables the tracking of a specified state during the maneuver. The effectiveness of the control laws is illustrated by their application to an F-15 aircraft to ensure acceptable aircraft performance during a maneuver. ONVENTIONAL piloting techniques are often inade- quate to meet the demanding requirements of flight research maneuvers with high-performance aircraft. These maneuvers often require precise control of onset rates in ex- treme flight conditions. Thus the pilot may be trying to con- trol an aircraft at high kngles of attack and high g's while at- tempting to increase normal acceleration at a prescribed rate through a maneuver specified at the very limits of accuracy of the cockpit instruments; A new flight-test technique1 was developed at the Dryderi Flight Research Facility of the NASA Ames Research Center (Ames-Dryden) to aid the pilot during these maneuvers. The essence of this technique is the application of an autopilot to provide precise control during the required flight-test maneuvers. The flight-test maneuver autopilot (FTMAP) is designed to provide precise, repeatable ebntrol of a high- performance aircraft during certain prescribed maneuvers so that a large quantity of data can be obtained in a minimum of flight time. The FTMAP can be used for Various maneuvers * including straight-and-level flight, level accelerations and decelera- tions, pushover pullups, excess:thrust windup turns, thrust- limited turns, and the rockinghorse maneuvers. Each of these maneuvers involves tracking certain states of the air- craft and holding certain states within prescribed values, as well as placing constraints on the derivatives of the states (for example, the excess-thrust windup turn is performed at coh$tant altitude and Mach number, with angle of attack in- creasing at a specified rate to achieve the final angle of attack). This paper discusses the development of the FTMAP con- trol laws within the context of flight test maneuver re- quirements. The FTMAP control laws are developed using the eigensystem assignment2 and command generator track- ing.3 The feedback gain obtained from eigensystem assign- ment ensures the desirable performance of the aircraft. The