A new nonlinear guidance logic, that has demonstrated superior performance in guiding unmanned air vehicles (UAVs) on curved trajectories, is presented. The logic approximates a proportional-derivative controller when following a straight line path, but the logic also contains an element of anticipatory control enabling tight tracking when following curved paths. The method uses inertial speed in the computation of commanded lateral acceleration and adds adaptive capability to the change of vehicle speed due to external disturbances, such as wind. Flight tests using two small UAVs showed that each aircraft was controlled to within 1.6 meters RMS when following circular paths. The logic was ultimately used for air rendezvous of the two aircraft, bringing them in close proximity to within 12 meters of separation, with 1.4 meters RMS relative position errors.
stability of the discrete, homogeneous, linear, minimum variance estimation formulas is investigated. ditions for uniform asymptotic stability in the large are derived. The conditions, if satisfied, also imply stochastic controllability and observability of the plant.
Sufficient con-
Abstract-Many firms expend a great amount of effort to increase the customer value of their product development (PD) processes. Yet, in PD, determining how and when value is added is problematic. The goal of a PD process is to produce a product "recipe" that satisfies requirements. Design work is done both to specify the recipe in increasing detail and to verify that it does in fact conform to requirements. As design work proceeds, certainty increases surrounding the ability of the evolving product design (including its production process) to be the final product recipe (i.e., technical performance risk decreases). The goal of this paper is to advance the theory and practice of evaluating progress and added customer value in PD. The paper proposes that making progress and adding customer value in PD equate with producing useful information that reduces performance risk. The paper also contributes a methodology-the risk value method-that integrates current approaches such as technical performance measure tracking charts and risk reduction profiles. The methods are demonstrated with an industrial example of an uninhabited combat aerial vehicle.Index Terms-Lean, performance measurement, product development, project management, risk management, systems engineering, value stream.
The paper explains how an important opportunity exists to pro-actively integrate suppliers at an early stage in the concept exploration and definition stages of product development. Research suggests that the concept of architectural innovation can be extended so that product features are matched with the associated specialized technical skills of partners in the development team.In addition to the establishment of integrated product teams, key enablers include: long-term commitment to suppliers; co-location; joint responsibility for design and configuration control; seamless information flow; and retaining flexibility in the definition of system configuration. Important contributing factors include: supplier-capability-enhancing investments; target costing; and incentive mechanisms. To promote innovative outcomes in military and government programmes, attention is drawn to the importance of governments championing closely-knit customer-supplier relationships.Firms can build enduring competitive strength by leveraging the specialized knowledge bases of their supplier networks. Two case-studies provide lessons to improve current approaches to the creation of long-term partnerships, or strategic alliances, with suppliers.
795establish initial convergence, the primary control system was engaged and a series of inputs was applied to demonstrate the performance of the adaptation logic. The pilot was not given an indication of angle of bank during the r u n , This resulted in a rolling supersonic dive ( M = 1.03). The altitude transition during the run was from 20 OOO to So00 ft. As in the longitudinal case, the performance of the adaptive system can be observed during the time intervals when the system is engaged. The uniformity of the roll rate response during engagement can be observed by comparing the steady-state roll rate at 20, 60, 80, and 1 0 0 s. Note the variability of the steady-state roll rate during time intervals where the primary control system is not engaged (e.%. at 5, 40, and 120 s). Note also that the surface commands required to realize the uniform roll rate responses vary considerably during the run. During the run, inputs were also made in rudder to examine the dutch roll adaptation characteristics. The dutch roll mode is observed to maintain a 0.7 damping ratio by examining the sideslip angle response to rudder inputs at times of 30,63, 83, and 110 s. These can be compared with the unaugmented responses at 10 and 50 s.
IV. CONCLUSIONSThis paper describes the moving window adaptive control concept whch has been developed as a candidate for flight test on the NASA FI-DFBW aircraft. Included are studies of the effects of auxiliary dither inputs to aid identification, data base size, measurement noise, and other design considerations. Results were presented indating the performance of the system in a nonlinear six-degee-of-freedom simulation of an F-8C aircraft. This study has shown that when there is sufficient motion of the aircraft, the adaptive algorithm converges to a h e a r mathematical model of the aircraft. Furthermore, it was shown that once these parameters have passed specified convergence criteria they may be used in an algebraic calculation of feedback and feedforward gains which satisfy certain flying quality requirements. Extensive simulation studies must be made before the moving window parameter adaptive control system can be recommended for flight test; however, results presented here indicate that the system is promising and should be evaluated further. One item requiring further evaluation and possible modification is the suitability of the mode of operation of the process without dither. REFERENCES J. R. Elliott, "NASA's advanced control law program for the F-8 digital fly-by-wire J. L. Picon. "Design of a digital adaptive control system for atmospheric reentry aircraft" this issue, pp. 753-757.
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