Control Anticipation Parameter Research Articles

High-Speed Rotorcraft Pitch Axis Response Type Investigation

This paper presents a systematic investigation of high-speed rotorcraft pitch-axis response types, command models, and handling qualities specifications. The investigation was done using two future vertical lift-relevant rotorcraft configurations—a lift offset coaxial helicopter with a pusher propeller and a tiltrotor. Five response types were investigated, consisting of a pitch rate-command/attitude-hold response type typically used for rotorcraft, a pitch rate-command/attitude-hold response type using a higher-order command model based on the conventional airplane pitch rate transfer function, a normal acceleration command/angle-of-attack hold response type, a flight path rate command/flight path hold response type, and a "blended" flight path rate command response type which varies the command model bandwidth based on stick input size. Designs of varying levels of pitch attitude bandwidth, flight path bandwidth, control anticipation parameter, and pitch attitude dropback were evaluated in a piloted simulation experiment conducted at the Penn State Flight Simulator facility using two high-speed mission task elements. The results of the piloted simulation suggest that both the pitch attitude bandwidth and the pitch attitude dropback requirements must be met for Level 1 handling qualities. A set of recommended specifications and associated updated level boundaries is provided in the Appendix.

Research on a Passenger Aircraft Flight Control System Gain Scheduler Design

This paper employs the mathematical model of a passenger aircraft for the purpose of designing longitudinal flight control law to satisfy handling qualities assessment. Aircraft Rate Command Attitude Hold (RCAH) controllers are designed at the specific equilibrium points in the flight envelope by means of a state space pole placement design procedure. The handling qualities assessment of the aircraft is presented, based on which the gain scheduler is designed. The existing criteria are employed to assess the handling qualities of the aircraft augmented by the gain scheduler, including the Control Anticipation Parameter (CAP) and Neal and Smith. The augmented aircraft performs satisfactorily and meets the requirement of handling qualities.

On the Handling Qualities of Two Flying Wing Aircraft Configurations

The coupling of the longitudinal and lateral stability modes of an aeroplane is considered in two cases: (i) weak coupling, when the changes in the frequency and damping of the phugoid, short period, dutch roll, and helical modes are small, i.e., the square of the deviation is negligible compared to the square of the uncoupled value; (ii) strong coupling, when the coupled values may differ significantly from the uncoupled values. This allows a comparison of three values for the frequency and damping of each mode: (i) exact, i.e., fully coupled; (ii) with the approximation of weak coupling; (iii) with the assumption of decoupling. The comparison of these three values allows an assessment of the importance of coupling effects. The method is applied to two flying wing designs, concerning all modes in a total of eighteen flight conditions. It turns out that lateral-longitudinal coupling is small in all cases, and thus classical handling qualities criteria can be applied. The handling qualities are considered for all modes, namely the phugoid, short period, dutch roll, spiral, and roll modes. Additional focus is given to the pitch axis, considering the control anticipation parameter (CAP). The latter relates to the two kinds of manouever points, where damping vanishes, that are calculated for minimum speed, take-off, and initial and final cruise conditions. The conclusion compares two flying wings designs (the “long narrow” and “short wide” fuselage concepts) not only from the point of view of flight stability, but also from other viewpoints.

Evaluation of Unmanned Aircraft Flying/Handling Qualities Using a Stitched Learjet Model

Over the past 20 years, unmanned aircraft have taken over military missions that were deemed to be too “dull, dirty, or dangerous” for manned aircraft. The urgent demand for aircraft that can execute these missions has resulted in a “build-fly-fix-fly” development mentality. Currently, documents that specify flying and handling quality requirements for manned aircraft, such as MIL-STD-1797, list those requirements as “TBD” for unmanned aircraft. In an effort to develop metrics that can be used to quantify the handling qualities of unmanned aircraft and expand the database that can be used to develop handling quality requirements, an analysis was performed using a Simulink model of the Calspan LJ-25D Variable Stability System aircraft at the United States Test Pilot School. Two maneuvers were simulated: 1) a climbing spiral, and 2) a precision offset landing. These maneuvers were chosen to evaluate the maneuver performance and workload, as measured by control surface activity, while varying stability and control parameters. The data were used to identify trends between the stability and control parameters and the resulting workload and maneuver performance metrics. Thumbprint plots were generated to identify Level 1, Level 2, and Level 3 flying qualities and were compared to similar MIL-STD-1797 plots. Results point to using a combination of classical aircraft literal factors, such as the short-period damping and control anticipation parameter, with newly developed metrics, employing norm and Thiel’s inequality coefficient (), to assess the maneuver performance and workload of the aircraft and flight controller during a maneuver.

Match Characteristics of Design Parameters of Longitudinal Flying Qualities and Pitch Agility

Modern high-performance fighter design should meet the requirements of both flying qualities and flight agility. In this paper, the influence of flying qualities design parameters on flight agility was analyzed and the match laws of Level 1 flying qualities and satisfied flight agility was summarized. The longitudinal match law indicates that Control Anticipation Parameter(CAP) is the main effect factor of initial pitch acceleration and Equivalent Frequency(ωsp) and Damping Ratio(ξsp) affect the stability of the aircraft after loading. With the descending of Control Anticipation Parameter(CAP), the range formed by ωsp and ξsp shrinks and finally comes to a point.

Augmented-Stability Controller Design for a UAV’s Longitudinal Motion

With the purpose of overcoming the defect that unmanned air vehicles (UAVs) are easily disturbed by air current and tend to be unstable, an augmented-stability controller was developed for a certain UAV’s longitudinal motion. According to requirements of short-period damping ratio and control anticipation parameter (CAP) in flight quality specifications of GJB185-86 and C*, linear quadratic regulator (LQR) theory was used in the augmented-stability controller’s design. The simulation results show that the augmented-stability controller not only improves the UAV’s stability and dynamic characteristics but also enhances the UAV’s robustness.

Robust Flight Controller Design That Takes Into Account Handling Quality

Ar obust flight controller design method, which satisfies handling quality requirements, is shown. The expanded control anticipation parameter is introduced as a new handling quality criterion to treat high-order dynamics. The relations to the C∗ criterion and equivalent systems are shown. The proposed criterion is formulated as a linear matrix inequality, and a robust flight controller that satisfies handling-quality requirements can be designed numerically. In addition, a cost index with a time-weighting function that evaluates several time response features is introduced into controller design. An example that illustrates flight controller design of Multi-Purpose Aviation Laboratory airplane is presented, and flight testing is performed.

Supersonic transport aircraft longitudinal flight control law design

AbstractModern civil transport aircraft utilise increasingly complex command and stability augmentation systems to restore stability, optimise aerodynamic performance and provide the pilot with the optimum handling qualities. Provided it has sufficient control power a second generation fly-by-wire supersonic transport aircraft should be capable of exhibiting similarly desirable low-speed handling qualities. However, successful flight control law design requires identification of the ideal command response type for a particular phase of flight, a set of valid handling quality design criteria and piloted simulation evaluation tasks and metrics. A non-linear mathematical model of the European supersonic transport aircraft has been synthesized on the final approach to land. Specific handling quality design criteria have been proposed to enable the non-linear dynamic inversion flight control laws to be designed, with piloted simulation used for validation. A pitch rate command system, with dynamics matched to the aircraft’s flight path response, will consistently provide Level 1 handling qualities. Nevertheless, pre-filtering the pilot’s input to provide a second order pitch rate response, using the author’s suggested revised constraints on the control anticipation parameter will generate the best handling qualities during the terminal phase of flight. The resulting pre-filter can be easily applied to non-linear dynamic inversion inner loop controllers and has simple and flight proven sensor requirements.

縦運動の飛行性を考慮した飛行制御系の設計

The controller design method taking account of flying quality is proposed. Where it is assumed that pilot determines flying quality by CAP (control anticipation parameter). Because CAP condition is formulated in LMI forms, flying quality requirement can be introduced into controller design easily. When the LMIs have a solution, flying quality of closed-loop system is guaranteed. Flying quality condition is combined with robust stability condition and verified by numerical example.

A generic control anticipation parameter for aircraft handling qualities evaluation

AbstractThe established control anticipation parameter longitudinal handling qualities criterion is based on the assumption that the short term dynamic response of the aeroplane is classical, or second-order-like. Modern fly-by-wire aircraft often have longitudinal short term dynamics which are not second-order-like and to which it is difficult to apply the criterion. This paper presents a proposed generic control anticipation parameter which is a modified version of the control anticipation parameter and which may be applicable to both unaugmented and augmented aircraft of all types. The appropriateness of the modified criterion was illustrated by designing a number of command and stability augmentation control laws, constrained to meet the criterion, for application to a medium weight fly-by-wire civil transport aircraft. The handling characteristics conferred by the control laws were assessed in a series of flight simulator trials, the results of which are briefly presented.

The definition of short-period flying qualities characteristics via equivalent systems

The high-order transfer functions representing the longitudinal dynamics of augmented aircraft were matched in the frequency domain with firstover second-order short-period models. Matching of the pitch rate to pilot input transfer function is shown to yield excellent time history matches. However, the resulting numerator term, La, takes on very large unrealistic values. The effect of simultaneously matching pitch rate and normal acceleration to restrict the variation of La is demonstrated. A control anticipation parameter is recommended to provide correlation between the highand low-order system descriptions and the specification requirements.

A Unifying Framework for Longitudinal Flying Qualities Criteria

The objective of this paper is to interpret existing flying qualities criteria in a multivariable format based upon state vectors and matrices of stability and control derivatives. State-space methods are shown to be entirely compatible with conventional flying qualities analysis. Furthermore, they lead to a definition of the well-known control anticipation parameter that has potential utility in the evaluation of higher-order aircraft/control systems.