Active control optimization techniques
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Rudisill, C. S.↗
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Application of active controls technology to aircraft bide smoothing systems
A critical review of past efforts in the design and testing of ride smoothing and gust alleviation systems is presented. Design trade offs involving sensor types, choice of feedback loops, human comfort, and aircraft handling-qualities criteria are discussed. Synthesis of a system designed to employ direct-lift and side-force producing surfaces is reported. Two STOL aircraft and an executive transport are considered. Theoretically predicted system performance is compared with hybrid simulation and flight test data. Pilot opinion rating, pilot workload, and passenger comfort rating data for the basic and augmented aircraft are included.
Lapins, M.↗
Computer program system for dynamic simulation and stability analysis of passive and actively controlled spacecraft. Volume 1. Theory
A theoretical development and associated digital computer program system is presented. The dynamic system (spacecraft) is modeled as an assembly of rigid and/or flexible bodies not necessarily in a topological tree configuration. The computer program system may be used to investigate total system dynamic characteristics including interaction effects between rigid and/or flexible bodies, control systems, and a wide range of environmental loadings. Additionally, the program system may be used for design of attitude control systems and for evaluation of total dynamic system performance including time domain response and frequency domain stability analyses. Volume 1 presents the theoretical developments including a description of the physical system, the equations of dynamic equilibrium, discussion of kinematics and system topology, a complete treatment of momentum wheel coupling, and a discussion of gravity gradient and environmental effects. Volume 2, is a program users' guide and includes a description of the overall digital program code, individual subroutines and a description of required program input and generated program output. Volume 3 presents the results of selected demonstration problems that illustrate all program system capabilities.
Bodley, C. S.↗
Computer program system for dynamic simulation and stability analysis of passive and actively controlled spacecraft. Volume 2: Program user's guide
For abstract, see N76-25319.
Bodley, C. S.↗
Computer program system for dynamic simulation and stability analysis of passive and actively controlled spacecraft. Volume 3: Demonstration problems
For abstract, see N76-25319.
Bodley, C. S.↗
Use of active control technology to improve ride qualities of large transport aircraft
Analyses, construction and flight testing of two systems: Beta-vane and Modal Suppression Augmentation System (MSAS), which were developed to suppress gust induced lateral accelerations of large aircraft, are described. The 747 transport was used as the test vehicle. The purpose of the Beta-vane system is to reduce acceleration levels at the dutch roll frequency whereas the function of the MSAS system is to reduce accelerations due to flexible body motions caused by turbulence. Data from flight test, with both systems engaged shows a 50 to 70 percent reduction in lateral aft body acceleration levels. Furthermore, it is suggested that present day techniques used for developing dynamic equations of motion in the flexible mode region are limited.
Cohen, G. C.↗
Recent advances in aerodynamic energy concept for flutter suppression and gust alleviation using active controls
Control laws are derived, by using realizable transfer functions, which permit relaxation of the stability requirements of the aerodynamic energy concept. The resulting aerodynamic eigenvalues indicate that both the trailing edge and the leading edge-trailing edge control systems can be made more effective. These control laws permit the introduction of aerodynamic damping and stiffness terms in accordance with the requirements of any specific system. Flutter suppression and gust alleviation problems can now be treated by either a trailing edge control system or by a leading edge-trailing edge control system by using the aerodynamic energy concept. Results are applicable to a wide class of aircraft operating at subsonic Mach numbers.
Nissim, E.↗
Application of the aerodynamic energy concept to the selection of transfer functions for flutter suppression and gust alleviation using active controls
Changes are introduced in the aerodynamic energy approach which lead to an increase in the effectiveness of both the trailing-edge (TE) and the leading-edge (LE)-TE control systems. Control laws are determined, using realizable transfer functions, which permit the introduction of aerodynamic damping and stiffness terms in accordance with the requirements of any specific system. It is shown that flutter suppression and gust alleviation problems can successfully be treated either by a TE or by a LE-TE control system. The results obtained are applicable to a very wide class of aircraft operating within the subsonic Mach number range.
Nissim, E.↗
Active control of potential of the geosynchronous satellites ATS-5 and ATS-6
The ATS-6 geosynchronous satellite carries two cesium ion thrusters as part of the technology experiment package. Their effectiveness in controlling the spacecraft potential was shown during normal operation of the thrusters. Auroral particle detectors were used to estimate spacecraft potential, amount of cesium propellant backflow to the spacecraft, and electron signature of the thruster. Operation of the thruster clamps the spacecraft to about -10 v in the presence of a wide range of ambient particle flux. Some positive ions from the thruster are returned to the spacecraft during this period. The plasma bridge neutralizer of the thruster is also effective in controlling the spacecraft potential. Laboratory simulation tests of the ATS-5 ion thruster thermionic emitter neutralizer showed that negative differential charging on the spacecraft surface probably prevents the emitter from completely discharging the spacecraft in flight.
Goldstein, R.↗
Summary of the two year NASA program for active control of ATS-5/6 environmental charging
Experiments conducted on the ATS 5 and ATS 6 which have demonstrated the feasibility of modifying or clamping the environmentally induced potential of these spacecraft are described. The results of these experiments indicate that a thermionic electron source is capable of replacing photo-emitted electrons during eclipse. However, the utility of this type of device is limited if its emission is suppressed by local electric fields. On the other hand, it is shown that a plasma source will not only serve as a substitute for photo-emitted electrons but will also suppress differential charging of isolated elements of the spacecraft which would tend to suppress electron emission. This later device is therefore capable of clamping the potential of a spacecraft without special considerations of its coupling to the ambient plasma.
Bartlett, R. O.↗
Design maneuver loads for an airplane with an active control system
This paper discusses the results of utilizing a maneuver load control (MLC) system to provide relief from the loads induced by an increase in wing span on a long range version of the Lockheed L-1011 TriStar. The MLC system deflects the outboard aileron symmetrically, in response to accelerometer signals, to redistribute wing airloads during maneuvers. The process of establishing the MLC system requirements, which involves determining the effects on wing loads of the extended wing span and extended aileron, is discussed. Effects of the MLC system and the extended span on the wing loads for symmetric and asymmetric design maneuvers are reviewed. Flight test results are compared with analytical load predictions. Some potential impacts on design requirements due to finite in-flight availability of the MLC system are illustrated.
Ramsey, H. D.↗
Preliminary investigations into the active control of large space structures: Solution of the Timoshenko beam equations by the method of characteristics
An algorithm was developed and incorporated into a computer program for solving the damped, Timoshenko beam equations with free-free boundary conditions and prescribed initial data. A number of special cases are considered and, where appropriate, comparisons are made with known results.
Tweed, J.↗
Impact of longitudinal flying qualities upon the design of a transport with active controls
Direct constrained parameter optimization was used to optimally size a medium range transport for minimum direct operating cost. Several stability and control constraints were varied to study the sensitivity of the configuration to specifying the unaugmented flying qualities of transports designed with relaxed static stability. Additionally, a number of handling quality related design constants were studied with respect to their impact to the design.
Sliwa, S. M.↗
Magnetic Bearing With Active Control
Magnetic shaft bearing employs electromagnets energized by signals related to shaft position and velocity. Electromagnets are arranged in orthogonal pairs. Axial and rotational shaft motions are accomodated, and lateral motions are restrained. Axial motion can also be restrained. Self-regulating bearing includes velocity and position control.
Goldowsky, M.↗
High frequency drive mechanism for an active controls systems aircraft control surface
The mechanism was successfully utilized on a wind tunnel model tested in the transonic blow down tunnel. The mechanism is also applicable to a flying aircraft. Several interrelated mechanical subsystems were utilized, including a low inertia antibacklash drive mechanism for high frequency oscillation and a compact antibacklash drive mechanism for conversion of rotary motion to linear motion.
Smith, H. E.↗
Active control of space structures: Proof of concept experiment
Modern control theory easily works with multiple input/multiple output systems. Two types of systems which fall into this category are flexible systems, where many measurements and several actuators are necessary to provide control over bending behavior, and articulated systems which consist of several rigid bodies connected together by pivoting connections. In this latter case, multiple controls are implemented as torquers at the joints.
Breakwell, J. A.↗
Comparison of analytical and wind-tunnel results for flutter and gust response of a transport wing with active controls
Two flutter suppression control laws wre designed and tested on a low speed aeroelastic model of a DC-10 derivative wing. Both control laws demontrated increases in flutter speed in excess of 25 percent above the passive wing flutter speed. In addition, one of the control laws was effective in reducing loads due to turbulence generated in the wind tunnel. The effect of variations in gain and phase on the closed-loop performance was measured and is compared with predictions. In general, both flutter and gust response predictions agree reasonably well with experimental data.
Abel, I.↗
System data communication structures for active-control transport aircraft, volume 1
Candidate data communication techniques are identified, including dedicated links, local buses, broadcast buses, multiplex buses, and mesh networks. The design methodology for mesh networks is then discussed, including network topology and node architecture. Several concepts of power distribution are reviewed, including current limiting and mesh networks for power. The technology issues of packaging, transmission media, and lightning are addressed, and, finally, the analysis tools developed to aid in the communication design process are described. There are special tools to analyze the reliability and connectivity of networks and more general reliability analysis tools for all types of systems.
Hopkins, A. L.↗