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IECON '87: Industrial applications of control and simulation; Proceedings of the 1987 International Conference on Industrial Electronics, Control, and Instrumentation, Cambridge, MA, Nov. 3, 4, 1987

Recent advances in control-system design and simulation are discussed in reviews and reports. Among the topics considered are fast algorithms for generating near-optimal binary decision programs, trajectory control of robot manipulators with compensation of load effects via a six-axis force sensor, matrix integrators for real-time simulation, a high-level control language for an autonomous land vehicle, and a practical engineering design method for stable model-reference adaptive systems. Also addressed are the identification and control of flexible-limb robots with unknown loads, adaptive control and robust adaptive control for manipulators with feedforward compensation, adaptive pole-placement controllers with predictive action, variable-structure strategies for motion control, and digital signal-processor-based variable-structure controls.

Hartley, Tom T.↗

Stability and performance tradeoffs in bi-lateral telemanipulation

Kinesthetic force feedback provides measurable increase in remote manipulation system performance. Intensive computation time requirements or operation under conditions of time delay can cause serious stability problems in control-system design. Here, a simplified linear analysis of this stability problem is presented for the forward-flow generalized architecture, applying the hybrid two-port representation to express the loop gain of the traditional master-slave architecture, which can be subjected to similar analysis. The hybrid two-port representation is also used to express the effects on the fidelity of manipulation or feel of one design approach used to stabilize the forward-flow architecture. The results suggest that, when local force feedback at the slave side is used to reduce manipulator stability problems, a price is paid in terms of telemanipulation fidelity.

Hannaford, Blake↗

Modeling and control design of a wind tunnel model support

The 12-Foot Pressure Wind Tunnel at Ames Research Center is being restored. A major part of the restoration is the complete redesign of the aircraft model supports and their associated control systems. An accurate trajectory control servo system capable of positioning a model (with no measurable overshoot) is needed. Extremely small errors in scaled-model pitch angle can increase airline fuel costs for the final aircraft configuration by millions of dollars. In order to make a mechanism sufficiently accurate in pitch, a detailed structural and control-system model must be created and then simulated on a digital computer. The model must contain linear representations of the mechanical system, including masses, springs, and damping in order to determine system modes. Electrical components, both analog and digital, linear and nonlinear must also be simulated. The model of the entire closed-loop system must then be tuned to control the modes of the flexible model-support structure. The development of a system model, the control modal analysis, and the control-system design are discussed.

Howe, David A.↗

Integrated flight/propulsion control for supersonic STOVL aircraft

A technology program to investigate integrated flight/propulsion control-system design for STOVL fighter aircraft is described. Integrated control systems being developed by U.S. industry for specific STOVL concepts are discussed. Attention is given to NASA involvement in the definition of control concepts, design-methods and flying-qualities criteria, and the evaluation of these concepts and criteria in analytical design studies, in ground-based experiments, and in flight on the Harrier V/STOL research aircraft. Initial fixed-base simulation experiments conducted for two STOVL fighter concepts are discussed. These simulations defined acceptable transition flight envelopes, determined control power used during transition and hover, and provided evaluations of the integration of the flight and propulsion controls to achieve good flying qualities throughout the low-speed flight envelope.

Franklin, James A.↗

Structural interaction with control systems

A monograph which assesses the state of the art of space vehicle design and development is presented. The monograph presents criteria and recommended practices for determining the structural data and a mathematical structural model of the vehicle needed for accurate prediction of structure and control-system interaction; for design to minimize undesirable interactions between the structure and the control system; and for determining techniques to achieve the maximum desirable interactions and associated structural design benefits. All space vehicles are treated, including launch vehicles, spacecraft, and entry vehicles. Important structural characteristics which affect the structural model used for structural and control-system interaction analysis are given.

Noll, R. B.↗

Improved approximations for control augmented structural synthesis

A methodology for control-augmented structural synthesis is presented for structure-control systems which can be modeled as an assemblage of beam, truss, and nonstructural mass elements augmented by a noncollocated direct output feedback control system. Truss areas, beam cross sectional dimensions, nonstructural masses and rotary inertias, and controller position and velocity gains are treated simultaneously as design variables. The structural mass and a control-system performance index can be minimized simultaneously, with design constraints placed on static stresses and displacements, dynamic harmonic displacements and forces, structural frequencies, and closed-loop eigenvalues and damping ratios. Intermediate design-variable and response-quantity concepts are used to generate new approximations for displacements and actuator forces under harmonic dynamic loads and for system complex eigenvalues. This improves the overall efficiency of the procedure by reducing the number of complete analyses required for convergence. Numerical results which illustrate the effectiveness of the method are given.

Thomas, H. L.↗

The Effects of Longitudinal Control-System Dynamics on Pilot Opinion and Response Characteristics as Determined from Flight Tests and from Ground Simulator Studies

The results of a fixed-base simulator study of the effects of variable longitudinal control-system dynamics on pilot opinion are presented and compared with flight-test data. The control-system variables considered in this investigation included stick force per g, time constant, and dead-band, or stabilizer breakout force. In general, the fairly good correlation between flight and simulator results for two pilots demonstrates the validity of fixed-base simulator studies which are designed to complement and supplement flight studies and serve as a guide in control-system preliminary design. However, in the investigation of certain problem areas (e.g., sensitive control-system configurations associated with pilot- induced oscillations in flight), fixed-base simulator results did not predict the occurrence of an instability, although the pilots noted the system was extremely sensitive and unsatisfactory. If it is desired to predict pilot-induced-oscillation tendencies, tests in moving-base simulators may be required. It was found possible to represent the human pilot by a linear pilot analog for the tracking task assumed in the present study. The criterion used to adjust the pilot analog was the root-mean-square tracking error of one of the human pilots on the fixed-base simulator. Matching the tracking error of the pilot analog to that of the human pilot gave an approximation to the variation of human-pilot behavior over a range of control-system dynamics. Results of the pilot-analog study indicated that both for optimized control-system dynamics (for poor airplane dynamics) and for a region of good airplane dynamics, the pilot response characteristics are approximately the same.

Sadoff, Melvin↗

Analysis of space shuttle orbiter entry dynamics from Mach 10 to Mach 2.5 with the November 1976 flight control system

A six-degree-of-freedom simulation analysis was performed for the space shuttle orbiter entry from Mach 10 to Mach 2.5 with realistic off-nominal conditions using the flight control system referred to as the November 1976 Integrated Digital Autopilot. The off-nominal conditions included: (1) aerodynamic uncertainties in extrapolating from wind tunnel of flight characteristics, (2) error in deriving angle of attack from onboard instrumentation, (3) failure of two of the four reaction control-system thrusters on each side (design specification), and (4) lateral center-of-gravity offset. Many combinations of these off-nominal conditions resulted in a loss of the orbiter. Control-system modifications were identified to prevent this possibility.

Powell, R. W.↗

Effects of Control-Feel Configuration on Airplane Longitudinal Control Response

A general study of longitudinal control feel was made with a transonic fighter-type airplane equipped with a control-feel system which 4 was adjustable in flight. The control-feel system provided a feel component with individual gain control in proportion to each of five quantities: stick deflection, stick rate, airplane normal acceleration, pitching acceleration, and pitching velocity. A number of feel configurations were investigated in flight and analytically. These feel configurations had feel components in various amounts from various combinations of these five sources. The results contained herein are all for an airplane center-of-gravity position at approximately 25 percent of the mean aerodynamic chord, a Mach number of 0.85, and an altitude of 28,000 feet. Results are presented as time histories, as plots of the variation of peak force per g with input duration, and as frequency-response plots. A number of frequency-response plots are included to illustrate the effects of choice of feel sources and gains. The results illustrate the desirability of balancing a normal-acceleration feel component with a pitching-acceleration feel component. Pitching-velocity feel is shown to be useful for shaping control-system frequency response. The results suggest the desirability of designing a control-feel system to a large extent by means of frequency-response analysis in order to keep the shapes of the frequency-response curves within desirable limits.

Crane, Harold L.↗

Pointing and control of planetary spacecraft - The next 20 years

Four basic categories of spacecraft pointing and control systems are discussed: (1) spin stabilized, (2) dual spin, (3) three-axis, and (4) momentum bias. Goals, mission requirements, and payloads should be considered for selection of control systems. A set of representative requirements, including life and environmental, vehicle/payload orientation and accuracy requirements, and control-system operational and functional requirements are discussed. Attention is given to design constraints imposed by the system selection. It is noted that sensitivity of any system design to increasing accuracy and flexibility in science-mission reprogramming will be major cost factors.

Mcglinchey, L. F.↗

From natural language to control signals: a conceptual framework for semantic channel finding in complex experimental infrastructure

Modern experimental platforms such as particle accelerators, fusion devices, telescopes, and industrial process control systems expose tens to hundreds of thousands of control and diagnostic channels, accumulated over decades of hardware evolution. Operators and AI systems alike depend on informal expert knowledge, inconsistent naming conventions, and scattered documentation to locate the signals required for monitoring, troubleshooting, and automated control, creating a persistent bottleneck for reliability, scalability, and emerging language-model-driven interfaces. We formalize semantic channel finding, the task of mapping natural-language intent to concrete control-system signals, as a general problem in complex experimental infrastructure, and introduce a four-paradigm conceptual framework to guide architecture selection based on facility-specific data regimes. The paradigms span (i) direct in-context lookup over small, curated channel dictionaries, (ii) constrained hierarchical navigation through structured trees, (iii) interactive agent exploration using iterative reasoning and tool-based database queries, and (iv) ontology-grounded semantic search that decouples channel meaning from facility-specific naming conventions. We demonstrate the practical feasibility of each paradigm through proof-of-concept implementations at four operational facilities spanning two orders of magnitude in scale: from compact free-electron lasers to large synchrotron light sources, operating under diverse control-system architectures ranging from clean hierarchical naming schemes to legacy environments with decades of heterogeneous conventions. Where evaluated against expert-curated operational queries, these instantiations achieve 90%–97% accuracy, validating the framework’s applicability across real-world deployment scenarios. To accelerate adoption across the broader scientific and industrial control-system community, we release open-source, plug-and-play implementations of all three interactive paradigms-direct lookup, hierarchical navigation, and middle-layer exploration-within the Osprey framework, together with tools for channel database generation, interactive testing, and minimal-configuration deployment. This work establishes semantic channel finding as a foundational capability for human-centric and agentic AI interfaces at large-scale facilities, providing both a systematic framework for architecture design and practical resources to enable adoption without building custom infrastructure from scratch.

channel finding↗

Frequency-response identification of XV-15 tilt-rotor aircraft dynamics

The timely design and development of the next generation of tilt-rotor aircraft (JVX) depend heavily on the in-depth understanding of existing XV-15 dynamics and the availability of fully validated simulation models. Previous studies have considered aircraft and simulation trim characteristics, but analyses of basic flight vehicle dynamics were limited to qualitative pilot evaluation. The present study has the following objectives: documentation and evaluation of XV-15 bare-airframe dynamics; comparison of aircraft and simulation responses; and development of a validated transfer-function description of the XV-15 needed for future studies. A nonparametric frequency-response approach is used which does not depend on assumed model order or structure. Transfer-function representations are subsequently derived which fit the frequency responses in the bandwidth of greatest concern for piloted handling-qualities and control-system applications.

Tischler, Mark B.↗

Space Shuttle separate-surface control-system study

A control system concept is presented that produces proportional control of yaw moment for the space shuttle from early entry to Mach 2 with only software modifications of the vehicle. It uses separate deflections of the inboard and outboard elevon surfaces and is evaluated, by determining the maximum static yawing moment available by considering the deflection limits of the elevon surfaces. A proportional moment slightly in excess of that produced by the most effective reaction control system (RCS) jet for yaw control can be obtained. In addition to the static moment study, a control law is designed which is intended to produce desired flying qualities.

Brown, L. W.↗

Ultrareliable, fault-tolerant control systems: A conceptual description

An Ultrareliable, Fault-Tolerant, Control-System (UFTCS) concept is described using a systems design philosophy which allows development of system structures containing virtually no common elements. Common elements limit achievable system reliability and can cause catastrophic loss of fault-tolerant system function. The UFTCS concept provides the means for removing common system elements by permitting the elements of the system to operate as independent, uncoupled entities. Multiple versions of the application program are run on dissimilar hardware. Fault tolerance is achieved through the use of static redundancy management.

Webster, L. D.↗

Simulation evaluation of the control system command monitoring concept for the NASA V/STOL research aircraft (VSRA)

A control-system monitoring concept is described that has the potential of rapidly detecting computer command failures (hardware or software) in fly-by-wire control systems. The concept has been successfully tested on the NASA Vertical/Short Takeoff and Landing Research Aircraft (VSRA) in the Ames Research Center's Vertical Motion Simulator. The test was particularly stringent, since the VSRA is required to operate in a hazardous environment. The fidelity of the aircraft model used in the simulation was verified by flying both the simulated and actual aircraft in a precision hover task using specially designed targets.

Schroeder, J. A.↗

Fiber optics for controls

The challenge of those involved in control-system hardware development is to accommodate an ever-increasing complexity in aircraft control, while limiting the size and weight of the components and improving system reliability. A technology that displays promise towards this end is the area of fiber optics for controls. The primary advantages of employing optical fibers, passive optical sensors, and optically controlled actuators are weight and volume reduction, immunity from electromagnetic effects, superior bandwidth capabilities, and freedom from short circuits and sparking contacts. Since 1975, NASA Lewis has performed in-house, contract, and grant research in fiber optic sensors, high-temperature electro-optic switches, and fly-by-light control-system architecture. Passive optical sensor development is an essential yet challenging area of work and has therefore received much attention during this period. A major effort to develop fly-by-light control-system technology, known as the Fiber-Optic Control System Integration (FOCSI) program, was initiated in 1985 as a cooperative effort between NASA and DOD. Phase 1 of FOCSI, completed in 1986, was aimed at the design of a fiber-optic integrated propulsion/flight control system. Phase 2, yet to be initiated, will provide subcomponent and system development, and a system engine test. In addition to a summary of the benefits of fiber optics, the FOCSI program, sensor advances, and future directions in the NASA Lewis program will be discussed.

Seng, Gary T.↗

Integrated tools for control-system analysis

The basic functions embedded within a user friendly software package (MATRIXx) are used to provide a high level systems approach to the analysis of linear control systems. Various control system analysis configurations are assembled automatically to minimize the amount of work by the user. Interactive decision making is incorporated via menu options and at selected points, such as in the plotting section, by inputting data. There are five evaluations such as the singular value robustness test, singular value loop transfer frequency response, Bode frequency response, steady-state covariance analysis, and closed-loop eigenvalues. Another section describes time response simulations. A time response for random white noise disturbance is available. The configurations and key equations used for each type of analysis, the restrictions that apply, the type of data required, and an example problem are described. One approach for integrating the design and analysis tools is also presented.

Ostroff, Aaron J.↗