Nonlinear control of non-minimum phase hypersonic vehicle models

Abstract

Longitudinal rigid-body models of air-breathing hypersonic vehicle dynamics are characterized by exponentially unstable zero-dynamics when longitudinal velocity and flightpath angle (FPA) are selected as regulated output. To enable application of stable dynamic inversion methods (and their adaptive counterparts), previous studies have considered the addition of a canard control surface to eliminate the occurrence of the unstable zero; however, the addition of a canard may negatively impact the design of the thermal protection system. In this paper, we present a methodology for robust nonlinear control of the rigid-body longitudinal hypersonic vehicle dynamics which employs only the elevator as aerodynamic control surface. The method reposes upon a nonlinear transformation of the equations-of-motion into the interconnection of systems in so-called feedback and feed-forward forms that allows the combination of high-gain and low-amplitude feedback, achieved through the use of saturated functions. Simulation results using the flexible vehicle model are presented to illustrate the effectiveness of the method.

Output feedback control of hypersonic vehicles based on neural network and high gain observer

“…Nonlinear control design are also common in the flight control design for hypersonic vehicles in recent years. For a more in depth review of control approaches for hypersonic vehicles, the reader is referred to [5][6][7].…”

Sequential Loop Closure Based Adaptive Autopilot Design for a Hypersonic Vehicle

“…The inner-loop error dynamics in (17) and outer-loop error dynamics in (28) can be combined as follows…”

“…In Reference [16] the nonminimum phase dynamics typically associated with the transfer function from an aircraft's elevator input to the altitude were overcome by the addition of a canard, which would be practically impossible to implement on a hypersonic vehicle. In Reference [17] a canard is no longer used, and the resulting unstable zero dynamics associated with regulating flight path angle using the elevator input are overcome using a non-adaptive dynamic inversion controller with a low gain outer loop and saturation functions. Reference [18] uses an adaptive dynamic inversion inner-loop control law, with a parameter identification algorithm which requires the state derivative be measurable.…”

Lyapunov-Based Exponential Tracking Control of a Hypersonic Aircraft with Aerothermoelastic Effects

“…Another adaptive approach [15] was recently developed with the addition of a guidance law that maintains the fuel ratio within its choking limits. While adaptive control and guidance control strategies for a HSV are investigated [13][14][15], neither addresses the case in which dynamics include unknown and unmodeled disturbances. There remains a need for a continuous controller, which is capable of achieving exponential tracking for a HSV dynamic model containing aerothermoelastic effects and unmodeled disturbances (i.e., nonvanishing disturbances that do not satisfy the linear in the parameters assumption).…”

“…A robust setpoint regulation controller [12] is designed to yield asymptotic regulation in the presence of parametric and structural uncertainty in a linear-parameterizable HSV system. An adaptive controller [13] was designed to handle (linear in the parameters) modeling uncertainties, actuator failures, and nonminimum phase dynamics [14] for a HSV with elevator and fuel ratio inputs. Another adaptive approach [15] was recently developed with the addition of a guidance law that maintains the fuel ratio within its choking limits.…”