Helicopter Flight Control System Research Articles

Modeling and control of helicopter flight control system with a controllable Semi-rotary fluid viscous damper

To improve the handling comfort of Helicopter Flight Control System (HFCS), an adaptive particle swarm optimization optimized variable universe fuzzy proportional-integral-derivative (APSO-VUFPID) strategy for damping force control is proposed. First of all, by the results of the controllable semi-rotary fluid viscous damper (CSFVD) mechanical tests, a hyperbolic tangent model is developed. Afterwards, an equivalent model of HFCS is established. In the next part, aiming at improving the vibration suppression performance of the joystick system, an APSO-VUFPID is proposed to generate the desired damping force in real-time. Finally, numerical simulation and experimental tests are carried out to verify the vibration reduction effect of the proposed APSO-VUFPID method with respect to passive, proportional-integral-derivative (PID), adaptive particle swarm optimization optimized proportional-integral-derivative (APSO-PID) and adaptive particle swarm optimization optimized fuzzy proportional-integral-derivative (APSO-FPID) methods. The results show that the hyperbolic tangent model can accurately describe the nonlinear mechanical characteristics of the CSFVD. Moreover, under the proposed APSO-VUFPID control method, the amplitude of acceleration and velocity of the joystick system are smaller than those obtained from passive, PID, APSO-PID and APSO-FPID methods. Therefore, the proposed APSO-VUFPID controller has better handling comfort compared to passive, PID, APSO-PID and APSO-FPID controllers and can be employed in real applications.

Simultaneous swept anhedral helicopter blade tip shape and control-system design

PurposeThis paper aims to offer a simultaneous design approach for helicopter having swept anhedral blade tip shape and helicopter flight control system (HFCS) to minimize controller cost.Design/methodology/approachBy considering previously stated offer, control-oriented models and a stochastic optimization method are applied to minimize controller cost of the HFCS.FindingsUsing simultaneous design approach for helicopters having blade tip swept and blade tip anhedral causes considerably less control effort than the helicopters not benefiting this related design approach.Practical implicationsSimultaneous design approach for helicopters having blade tip swept and blade tip anhedral is applicable to consider fuel economy.Originality/valueOne important novelty of this paper is using simultaneous approach for determining optimum shape of blade tip swept and anhedral. Another considerable novelty of this paper is also using a stochastic optimization method called simultaneous perturbation stochastic approximation for previously mentioned purpose. In this paper, it is also reached that using simultaneous design approach for swept anhedral helicopter blade tip shape and HFCS causes less control effort than the helicopters not using this approach. This leads to less fuel consumption and green environment.

CASE ANALYSIS ON FLIGHT CONTROL SYSTEM SIKORSKY S76 C++ FAILURE FROM YAW CONTROL ASPECT

Flight Control is a system that functions as a helicopter control center. Failure that occurs in flight control would certainly result inconvenience of the pilot in operating the helicopter, even the movement of the helicopter can out of control causing incident or accident. The continuity of the helicopter operation is affected by the maintenance system applied. One of mode moving system helicopter is yaw control, that could control the nose helicopter to move right and left. Fault Tree Diagram could described analytical technique, whereby an undesired state of the system is specified (usually a state that is critical from a safety or reliability standpoint). The system then analyzed in the context of its environment and operation to find the solution. Based on the analysis results of failures that occurred in the Sikorsky S76 C ++ helicopter flight control from yaw control aspect in the period of January 2015 to May 2018 with an average use of helicopter’s 2092.05 flight hours, there were 46 failures which caused by yaw control. Based on diagram, there were 4 basic events which caused unschedule maintenance on Sikorsky S76 C ++ helicopter flight control system because of yaw fail control, so that a replacement or repair was needed for the components that affected to the system failure.

Adaptive Learning-Based Observer With Dynamic Inversion for the Autonomous Flight of an Unmanned Helicopter

This article presents the development of an autonomous flight control system for a small-scale unmanned helicopter based on an online adaptive learning-based observer and model predictive control (MPC). The adaptive learning-based observer provides an approximate dynamic inversion for solving the coupled dynamic problem. The discrete-time MPC (DMPC) uses a prediction process to obtain a stable model. The Laguerre function, a state observer, and a recursive learning algorithm were integrated into DMPC, the core of the flight control system. Exponential data weighting was adopted to increase the stability of the designed flight control system. By integrating these approaches, an adaptive learning-based flight control system, which consists of the pitch, roll, yaw, and heave controllers, is presented to evaluate the stability and performance of the proposed autonomous flight control system of an unmanned helicopter. Moreover, an adaptive controller based on neural approximation for yaw motion is used to improve the performance of yawing control of the helicopter. In order to validate the feasibility of the proposed method, a hardware-in-the-loop simulation was performed in real time. The system included an embedded system, a self-developed users interface, and the X-plane flight simulator. The simulation results showed that the flight control system was able to maintain the position and the attitude of the helicopter in hover mode under the influence of wind gust and disturbance. The proposed method had better performance than a robust control system, in both ideal and disturbed environments.

헬리콥터 비행 제어시스템의 피드백 제어 이득 한계에 대한 로터 플랩 동역학의 영향성 분석

고-대역폭(High Bandwidth)의 헬리콥터 반응특성을 위한 높은 수준의 피드백 제어 게인의 사용은 로터 모드에 의해 항공기의 불안정성이 증가한다. 본 논문에서는 EC155B1 헬리콥터 모델링을 수행하고 이를 이용하여 롤 축의 각속도 및 자세 피드백 게인의 증가에 따른 항공기의 안정성을 분석하였다. 그리고 로터 플랩 모드에 의해 제한되는 롤 축 각속도 및 자세 피드백 제어 게인을 검토하였다. 또한 노이즈 제거 필터의 사용으로 비행 제어시스템의 위상지연이 증가 시 헬리콥터 안정성에 영향을 주는 피드백 제어 게인의 한계를 검토하였다.

Analysis of combined passively and actively morphing blade root chord length and blade taper for helicopter control

Purpose The purpose of this study is to examine the effect of passive and active morphing of blade root chord length and blade taper on the control effort of the flight control system (FCS) of a helicopter. Design/methodology/approach Physics-based helicopter models, which are functions of passive and active morphing, are created and applied in helicopter FCS design to determine the control effort. Findings Helicopters, having both passively and actively morphing blade root chord length and blade taper, experience less control effort than the ones having either only passively morphing blade root chord length or only blade taper or only actively morphing blade root chord length and blade taper. Practical implications Both passively and actively morphing blade root chord length and blade taper can be implemented for more economical autonomous helicopter flights. Originality/value Main novelty of our article is simultaneous application of passive and active morphing ideas on helicopter root chord length and blade taper. It is also proved in this study that using both passive and active morphing ideas on helicopter blade root chord and blade taper causes much less energy consumption than using either only passive morphing idea on helicopter blade root chord and blade taper or only active morphing idea on helicopter blade root chord and blade taper. This also reduces fuel consumption and also makes environment cleaner.

Research on unmanned aerial vehicle modeling and control based on intelligent algorithms

This article designs an automatic flight control system for an unmanned aerial vehicle helicopter. The differential evolution intelligent algorithm is used for a state-space model identification; the differential evolution method has an advantage of choosing initial point randomly. The accuracy of the identified model is verified by comparing the model-predicted responses with the responses collected during flight experiments. The reliability and efficiency of the differential evolution algorithm are demonstrated by the experimental results. A robust controller is designed based on the identified model for the unmanned aerial vehicle helicopter with two-loop control frame: the outer-loop is used to obtain the expected attitude angles through reference path and speed with guidance-based path-following control, and the inner-loop is used to control the attitude angles of helicopter tracking the expected ones with [Formula: see text] loop-shaping method. The greatest common right divisor method is used to choose the weighting matrix in loop shaping, in which the stability margin is larger and has a greater bandwidth of the unmanned aerial vehicle system. Finally, a space spiral curve trajectory tracking simulation is conducted to illustrate the efficiency of the proposed control systems, and the simulation results prove that the unmanned helicopter system achieves a top-level control performance.

A Special Kind of Sliding Mode Control for Nonlinear System With State Constraints

This paper presents a control strategy named auxiliary surfaces sliding mode control (AS-SMC) by using Positive Invariant Set (PIS) to control a class of continuous nonlinear systems with state constraints. The PIS can be regarded as a special kind of sliding surface, and its invariance ensures that the system state can satisfy the constraints in the convergence process. The stability analysis and a PIS theory proof are given. The control strategy is successfully tested in numerical simulations and even effectively applied to the coaxial unmanned helicopter flight control system on hardware in the loop (HIL) platform. The results verify the effectiveness of the proposed control strategy for the experimental set-up.

Rotor-state feedback control design to improve helicopter turbulence alleviation in hover

A helicopter flight control system with rotor-state feedback to improve turbulence alleviation in hover is presented. First, a flight dynamic model coupled with turbulence model is developed and validated. Then, an integrated control strategy with a rotor-state feedback control law is proposed based on the baseline control system. The feedback gains of body and rotor states are designed in synergy to improve turbulence alleviation in the interested frequency range of handling qualities. Subsequently, the effects of the rotor-state feedback gains on both the stability of rotor dynamics and helicopter turbulence alleviation are analyzed in detail. Finally, the effectiveness of the integrated control system is evaluated with linear analysis in frequency domain and nonlinear simulation in time domain. The results indicate that with the rotor-state feedback control law integrated into the control system, the helicopter turbulence alleviation in the interested frequency range is improved with less degradation in helicopter stability margins, and the roll and pitch rate responses of helicopter to turbulence, measured with Root-Mean-Square (RMS) values, are reduced by more than 50% and 35% respectively.

Survey on Flight Control Technology for Large-Scale Helicopter

A literature review of flight control technology is presented for large-scale helicopter. Challenges of large-scale helicopter flight control system (FCS) design are illustrated. Following this, various flight control methodologies are described with respect to their engineering implementation and theoretical developments, whose advantages and disadvantages are also analyzed. Then, the challenging research issues on flight control technology are identified, and future directions are highlighted.

Effect of the Simultaneous Variation in Blade Root Chord Length and Blade Taper on Helicopter Flight Control Effort

In this study, the effect of simultaneous variation in blade root chord length and blade taper on the control effort of helicopter flight control system (i.e., FCS) of a helicopter is investigated. Therefore, helicopter models (i.e., complex, control-oriented, and physics-based models) including the main physics and essential dynamics are used. The effect of simultaneous variation in the blade root chord length and blade taper (i.e., in both chordwise and lengthwise directions dependently) on the control effort of an FCS of a helicopter and also on the closed-loop responses is studied. Comparisons in terms of the control effort and peak values with and without variations in the blade root chord and blade taper changes are carried out. For helicopter FCS variance-constrained controllers, specific output variance-constrained controllers are beneficial.

Research on the Unmanned Aerial Vehicle Adaptive Control System based on Fuzzy Control and Chaos Mechanics

In this paper, we conduct research on the unmanned aerial vehicle adaptive control system based on fuzzy control and chaos mechanics. Four rotor aircraft is a kind of nonlinear systems with underactuated, strong coupling characteristic. Although in existing research, through the design of the control algorithm effectively inhibits both for flight control effect, but not fundamentally eliminate the effect of aircraft. Dynamic model of unmanned helicopter flight control system design is very approximate, need to gradually improve the modeling accuracy, so as to get the exact autonomous flight control, so you need to practice constantly required to modeling in the flight information, so the unmanned helicopter flight control system to have the ability to retrieve information modeling. This paper proposes the new idea on the issues that will be meaningful.

Control of a laboratory 3-DOF helicopter: Explicit model predictive approach

A helicopter flight control system is a typical multi-input, multi-output system with strong channel-coupling and nonlinear characteristics. This paper presents an explicit model predictive control (EMPC) for attitude regulation and tracking of a 3-Degree-of-Freedom (3-DOF) helicopter. A state-space representation of the system is established according to the characteristics of each degree-of-freedom motion. Multi-Parametric Quadratic Programming (MPQP) and online computation processes for explicit model predictive control and controller design for a 3-DOF helicopter are discussed. The controller design for set-point regulation and tracking time-varying reference signals of a 3-DOF helicopter are presented respectively. Numerical study of explicit model predictive control for attitude regulation and tracking of a 3-DOF helicopter are conducted. A hardware-in-the-loop experimental study of explicit model predictive control of a 3-DOF helicopter is made. To analyze the performances of an EMPC controlled helicopter system, an Active Mass Disturbance System and manual interference are considered in comparison with PID scheme. Numerical simulation and HIL experimental studies show that explicit model predictive control is valid and has satisfactory performance for a 3-DOF helicopter.

Impacts of safety on the design of light remotely-piloted helicopter flight control systems

This paper deals with the architecture definition and the safety assessment of flight control systems for light remotely-piloted helicopters for civil applications. The methods and tools to be used for these activities are standardised for conventional piloted aircraft, while they are currently a matter of discussion in case of light remotely-piloted systems flying into unsegregated airspaces. Certification concerns are particularly problematic for aerial systems weighing from 20 to 150kgf, since the airworthiness permission is granted by national authorities. The lack of specific requirements actually requires to analyse both the existing standards for military applications and the certification guidelines for civil systems, up to derive the adequate safety objectives. In this work, after a survey on applicable certification documents for the safety objectives definition, the most relevant functional failures of a light remotely-piloted helicopter are identified and analysed via Functional Hazard Assessment. Different architectures are then compared by means of Fault-Tree Analysis, highlighting the contributions to the safety level of the main elements of the flight control system (control computers, servoactuators, antenna) and providing basic guidelines on the required redundancy level.

Combined passive and active helicopter main rotor morphing for helicopter energy save

In this article, passive morphing and active morphing approaches are combined to save more helicopter flight control system (i.e., FCS) energy. For this purpose complex, physics-based, control-oriented nonlinear helicopter models are benefited. A specific variance-constrained control strategy, namely Output Variance-Constrained Control (i.e., OVC) is applied for helicopter FCS. Control energy savings using passive, active and combined morphing approaches are examined. Parameters of helicopter FCS and combined morphing helicopter design parameters are simultaneously optimized using a stochastic optimization method, namely simultaneous perturbation stochastic approximation (i.e., SPSA). To observe energy save, closed-loop analyses are done. Finally, robustness of combined morphing helicopter with respect to (w.r.t.) the modeling uncertainties is examined.

Helicopter Control Energy Reduction Using Moving Horizontal Tail.

Helicopter moving horizontal tail (i.e., MHT) strategy is applied in order to save helicopter flight control system (i.e., FCS) energy. For this intention complex, physics-based, control-oriented nonlinear helicopter models are used. Equations of MHT are integrated into these models and they are together linearized around straight level flight condition. A specific variance constrained control strategy, namely, output variance constrained Control (i.e., OVC) is utilized for helicopter FCS. Control energy savings due to this MHT idea with respect to a conventional helicopter are calculated. Parameters of helicopter FCS and dimensions of MHT are simultaneously optimized using a stochastic optimization method, namely, simultaneous perturbation stochastic approximation (i.e., SPSA). In order to observe improvement in behaviors of classical controls closed loop analyses are done.

Input-Shaping and Model-Following Control of a Helicopter Carrying a Suspended Load

When a heavy load is suspended from a helicopter, excessive load swing degrades helicopter control and can result in obstacle collisions. This work examines the benefits of combining input-shaping and model-following control to improve performance when carrying a suspended load. Model-following control architectures are used in modern helicopter flight control systems to make the helicopter respond like a prescribed model. On its own, model-following control is ineffective when carrying a suspended load because excessive load swing degrades tracking of the prescribed model dynamics and thus control of the helicopter. Therefore, reducing load swing improves tracking of the prescribed model and increases safety and productivity. Input shaping is a control technique that has been used to control vibration of flexible machines, such as robots, satellites, and cranes. By combining input shaping with model-following control, helicopter payload swing is reduced and tracking of the prescribed model is improved. The design of an attitude-command flight control system that combines input-shaping and model-following control is illustrated using dynamic models of a Sikorsky S-61 helicopter. Simulation results are shown for lateral and longitudinal repositioning movements. These results show that applying input shaping to simulated pilot commands greatly improves helicopter performance when carrying a suspended load.

Direct self-repairing control for a helicopter via quantum multi-model and disturbance observer

In this paper, a new direct self-repairing control scheme is developed for a helicopter flight control system with unknown actuator faults and external disturbance. The design of multi-model-based adaptive control is used to accommodate the faulty system under different fault conditions. By appropriate switching based on quantum information technique, the system can be converted to the best model and the corresponding controller. Asymptotic model following performance and system stability is guaranteed. A disturbance observer is introduced to observe the disturbance of the system, which can produce corresponding control signals according to the disturbance. The results including a numerical simulation and a semi-physical verification demonstrate the effectiveness of the proposed self-repairing control approach for the helicopter flight control system.

Flight Control Energy Saving via Helicopter Rotor Active Morphing

Helicopter main rotor active morphing is investigated to save helicopter flight control energy in the presence of constraints on outputs. For this purpose, the nonlinear equations of motion of the helicopter are linearized around straight level flight. Then, several main rotor active morphing scenarios such as blade radius, blade chord length, blade twist angle, and rotor angular speed variation are analyzed individually (i.e., each active morphing scenario is implemented one at a time). Output-variance-constrained control is used for helicopter flight control system design, and the control energy savings due to active morphing with respect to a conventional helicopter are evaluated. An extensive circumstance in which all active morphing concepts are implemented simultaneously is examined to obtain larger control energy savings. The possibility of using morphing controls for trimming is also considered, and stochastic optimization is used to solve the resulting simultaneous trimming and control design problem. Extensive analysis, including closed-loop system responses, is carried out for the most energy-efficient active morphing procedure. Comparisons with a helicopter designed using passive instead of active morphing are also performed. Finally, some robustness properties of the closed-loop system corresponding to the active morphing scenario are examined.

Investigation of Small Scale Helicopter Servo-Actuator Performance Using Frequency Sampling Filters

This paper addresses the performance of electric servo-actuators as part of a helicopter control linkage system. The development of a helicopter flight control system initially requires a non-linear model capable of accurately predicting the aircraft dynamics. The first step of this non-linear model represents the servo-actuator system, which transmits the pilots control inputs to the main rotor system. A series of system identification experiments were performed on a cyclic system servo-actuator under different operating conditions, and the servo-actuator step responses were estimated using a Frequency Sampling Filter. A performance comparison is made for a zero load bench test and the aircraft load condition in order to determine the most accurate representation of the servo-actuator dynamics for helicopter flight applications.