An apparatus and method for process control that extracts information from a process for developing a model of the process that is used to design system control. The apparatus includes means for selecting a process model form that has two or more selectable parameters. The apparatus also includes means for deliberately disturbing a process that is in open-loop operation and that is in a substantially settled state and further includes means for measuring the process response. The apparatus selects parameters for the process model form according to a function of the measured process response. In this way a complete model of the process is identified. The apparatus self-tunes by directly calculating new control parameters according to a function of the identified open-loop process model and a preselected target behavior.

Self-tuning controller that extracts process model characteristics

A required time of arrival (RTA) control system (200, 220, 240) is disclosed for use with an aircraft on-board computer system (100). The control system (200, 220, 240) is adapted to provide data for controlling aircraft flight in a manner so as to meet time of arrival constraints at selected waypoints. The control system (200, 220, 240) includes means (212) for determining a time error between an estimated time of arrival and a designated RTA. A cost index predictor (216) is utilized to determine an estimated cost index parameter for meeting time of arrival constraints, while maintaining relative minimum fuel consumption. A flight profile predictor (202) is adapted to generate requisite target air speed data based on the estimated cost index parameter. In one embodiment, the system (240) includes determination of a time window based on maximum and minimum permissible cost index and speed limiting parameters. Dead-band control of the time error is also provided for maintaining stability and reducing throttle activity.

Required time of arrival (RTA) control system

The instant invention provides a system and method for controlling the flight of an aircraft to meet an RTA. The system comprises a speed profile generator (144) that communicates with a trajectory generator (122) to produce a speed profile signal (120) that enables the aircraft to reach waypoint substantially at a predetermined time. In the system of the instant invention, the speed profile generator (144) receives a nominal speed command signal (212), a time error signal (136) and a sensitivity signal (130). Based o these inputs, the speed profile generator (144) produces a sped profile signal (120). The trajectory generator (122) receives the speed profile signal (120) and a required time of arrival signal (142). Based on these signals, the trajectory generator (122) produces a time error signal (136) and a sensitivity signal (130). This sensitivity signal (130) represents the sensitivity of the time error signal (136) to changes in the speed profile signal (120).

Aircraft control system for reaching a waypoint at a required time of arrival

The generation of optimal trajectories from cruise altitude to 10,000 ft for a typical commercial jet transport shows that the optimal absorption of delay in arrival time requires speed reduction in conjunction with altitude excursion (the latter not attempted before). Multiple regression methods are used to develop drag and fuel flow models which are smoother and more compact than those of any previous investigation. The concept of optimal cruise descent is introduced and optimal results are compared with suboptimal strategies of constant Mach number/Calibrated Airspeed (CAS) descent and constant flight path angle descent. Finally, wind effects are analyzed, and the cost of delay as a function of wind condition is presented, followed by the effects of wind on the constant flight path angle descent.

Four-dimensional fuel-optimal guidance in the presence of winds

An information storing device and an information processing device having a memory for registering a plurality of working modes at recording/reproduction and a switching circuit for selecting one of the plurality of working modes, which select the optimum working mode automatically or by an instruction of an operator according to power supply capacity of a device of higher rank to effect recording/reproduction.

Information storing device and method for controlling same to record/reproduce information by selecting one of working modes

An output vector produced by a plant in response to an input vector is filtered by a plurality of bandpass filters, each filter having a different pass band. A filtered output vector from each filter is provided as input to a separate adaptive feedback controller, and feedback vectors produced by the separate controllers are summed to provide the input vector to the plant. Each adaptive feedback controller continuously identifies an open-loop transfer function of the plant characterizing a particular frequency band of plant operation, and continuously adjusts its own open-loop transfer function so that the poles of the closed-loop transfer function of the plant for that particular frequency mode of operation are assigned to constant stable values despite changes in the open-loop transfer function of the plant.

Decentralized cautious adaptive control system

This paper presents an application of adaptive control to flutter suppression for an aircraft flying in turbulence. The adaptive control law is integrated with a nominal constant gain controller and furnishes the equivalent of a 180° phase margin at the flutter frequency. The design approach blends the classical, linear quadratic Gaussian and adaptive synthesis techniques so that each contributes at its point of strength to achieve a robust control law with good performance characteristics. It is shown that the adaptive controller stabilizes the flutter in the face of arbitrary initial parameter estimates, unmodeled stochastic inputs and significant level of spillover dynamics. The results presented in this paper are very encouraging and motivates continuing work in the field.

Adaptive Flutter Suppression in the Presence of Turbulence

Aircraft flying conventional descents and approaches into high density terminal areas often waste fuel. Such is also the case whenever they are delayed while awaiting approach clearance. Simulation results have shown that in heavy traffic, time-controlled (4-D) guidance in the aircraft will be necessary to realize the full potential of fuel conservative procedures. This paper focuses on the analysis of the 4-D guidance problem in the longitudinal plane. Singular Perturbation Theory is applied to reduce the computational burden of solving the resulting optimal control problem.

Development of 4-D Time-Controlled Guidance Laws using Singular Perturbation Methodology

The design requirements on airborne equipment which controls an aircraft so it arrives at an assigned time are mainly driven by the need for satisfactory control during descent. Assuming open-loop control during a typical descent, the final altitude and arrival time errors due to unforecast winds and temperatures aloft are determined. The fuel required for closed-loop control to reduce these errors is given. Equations of motion, suitable for on-board nominal descent trajectory computation using descent area forecasts, are derived, including the effects of winds and temperatures. A sample descent trajectory, obtained by integrating these equations with an actual forecast, is given. The design of descent controllers using feedback of errors relative to the nominal trajectory is treated. The arrival time errors and fuel usage of such controllers for different gain choices and unforecast winds and temperatures are evaluated by simulation.

Abhijit J. M. Chakravarty

Papers

Decentralized cautious adaptive control system

Adaptive Flutter Suppression in the Presence of Turbulence

Development of 4-D Time-Controlled Guidance Laws using Singular Perturbation Methodology

Time-Controlled Aircraft Guidance in Uncertain Winds and Temperatures