Reconfigurable Flight Control Design for combat flying wing with multiple control

surface

Akhil S

S7 ME

Roll no 10

GECBH

Contents

• Introduction

• Aircraft description

• Analysis

• Principle and implementation

• Simulation

• Conclusion

Introduction

Aircraft control surface failures – 3 types

Lock-in-place (LIP)

Loss-of-effectiveness (LOE)

Float

When these failures occurs, they will affect

• Control capability of the Aircraft• Endanger flight safety

Aircraft Description

Inboard elevons (IEs) and Outboard elevons (OEs)

Position limit : -300 to 300

Split drag rudders (SDRs) and Spoiler slot deflectors (SSDs)

Position limit : 00 to 600

Flight attitude control system

Elevons and drag rudders

ElevonsElevons are aircraft control surfaces that combine the functions of the elevator (used for pitch control) and the aileron (used for roll control)

Drag RuddersA rudder is a device used to steer. On an aircraft the rudder is used primarily to counter adverse yaw and p-factor and is not the primary control used to turn the airplane

Adverse yaw and p-factor

• Adverse yaw : Natural and undesirable tendency for an aircraft to yaw in the opposite direction of a roll.

P-factor(asymmetric blade effect) : It is an aerodynamic phenomenon experienced by a moving propeller, that is responsible for asymmetrical relocation of the propeller's center of thrust when aircraft is at a high angle of attack

Elevator Control System (Primary)

• Drive or climb

• Rotate around lateral

axis

• Forward and aft. Action

• Push / pull rod or cable

Aileron control system

• Prevent side slip, skid

• Bangking / rolling

• Differential mechanism

• Greater up than down

Rudder control system

A rudder is a device used to steer. On an aircraft the rudder is used primarily to counter adverse yaw and p-factor and is not the primary control used to turn the airplane

Analysis of Flight Control Reconfiguration Characteristics and Capability

• In conventional configuration

Roll control Aileron Pitch control Elevator Yaw control Rudder

What happens when any of these fails ?

Need for Reconfiguration(Redundancy design)

1. When Aileron fails ?

Differential deflection of elevator achieves reconfiguration

2. When elevator fails ?

Symmetric deflection of aileron can provide pitching thereby control capability

3. When rudder fails ?

Fulfill yaw control only rolling

How combat flying differs from other conventional Aircrafts

Contrast of attainable moment subsets (right SSD in failure)

Principle and Implementation of Flight Control Reconfiguration

• Flight control reconfiguration approaches

• Implement of flight control reconfiguration based on control allocation

• Principle of control allocation

• Adjust strategies of control reconfiguration

Flight control reconfiguration approaches

multiple mode switch

pseudo inverse Eigen structure assignment

adaptive control

sliding mode control

control allocation

Implementation of flight control reconfiguration based on control allocation

Principle of control allocation

Based certain optimization calculations to allocate 3-axis control

So when no failures condition is considered, it will be as

Adjust strategies of control reconfiguration

It was made on an assumption – Control surface failure detection system can work well

When the kth control surface has a

1. LIP failure

Strategies cont…

2. LOE failure

3. Float failure

Allocation results after the right SDR is subjected to three typical failures

Stimulation and Analysis

• Taking LIP failure for example to stimulate flight control reconfiguration

• Due to LIP failure makes 3-axis control capabilities decrease more

Numerical Stimulation

• Six degree of freedom non linear dynamic model• Initial flight condition is a horizontal flight at 4000m• Speed is taken as 204 m/s• Roll angle = 250

• Pitch angle = 300

• Yaw angle = -300

• Stimulation step time = 0.02s

Time histories of attitude angles

Time histories of normal control surfaces

Conclusion

1) Having different reconfiguration characteristics as compared with the conventional aircraft, the combat flying wing is fitted with multiple control surfaces, and has redundant control surfaces in three axes. Therefore, it has basic conditions to reconfigure.

2) The flight control reconfiguration approach based on control allocation does not need to modify the dynamic inversion flight control law of the aircraft, just via appropriately modifying the control allocation block, and then it can comparatively effectively realize the reconfigurable design during control surface failures. So it is suitable for the modular design of the complicate flight control system for the flying wing.

3) Despite the presence of control surface failures, the combat flying wing using this flight control reconfiguration approach can still guarantee its flight safety, and can comparatively better perform some flight missions with certain amplitude

Questions ???

References

• Reconfigurable Flight Control Design for Combat Flying Wing withMultiple Control Surfaces by WANG Lei, WANG Lixin

• Wikipedia

THANK YOU