Browse Topic: Center of gravity (CG)

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Flight Test Evaluation of Center of Gravity Effects on a Coaxial Ultralight HelicopterF-0082-2026-02165/5/2026
This paper presents results of flight tests conducted on a coaxial ultralight helicopter. An automated flight test evaluation method is presented and exemplified through its application to steady horizontal flight. The results shown include pilot controls, helicopter attitude angles, power, thrust and torque distribution between the rotors, rotor harmonic thrust components, and teeter angles, along with their rotor harmonic components across varying flight speeds. This study focuses on the dependencies of these parameters on center of gravity position and sideslip angle.
Mindt, Maximilian, Gradkowski, Piotr, Matthia, Jonas, Mahlstedt, Dominik
Mitigation of Whirl-Flutter throughWind Tunnel Testing of a Hingeless-Hub Tiltrotor ModelSM-2026-VLADA-51931/27/2026
A 4.75-ft diameter hingeless hub proprotor model was wind tunnel tested up to the very high speeds of 205 knots, loosely corresponding to 480 knots full-scale, with parametric variations in blades, wing spar, and pylon center of gravity. Testing revealed that a gimballed-hub configuration that reached whirl flutter at 160 knots was completely stabilized when converted to a hingeless hub – using identical blades, span, and pylon. While the gimballed-hub model encountered whirl flutter at 160 knots, the hingeless-hub configuration remained stable throughout the entire test envelope up to 205 knots. The key conclusions are that a hingeless hub can eliminate whirl flutter, and that the most stable configuration is a swept-tip blade hingeless-hub rotor with the pylon center of gravity aft of the wing spar.
O'Brien, Nathan, Datta, Anubhav
Guidelines for Repair Process Evaluation of Fiber Reinforced Composite Bonded StructureAIR6292 (Current)11/26/2025
The SAE Aerospace Information Report (AIR) is intended to be used as a process verification guide for evaluating implementation of key factors in bonded repair of fiber reinforced composite structure in a repair shop environment. The guide will be used in conjunction with a regulatory approved and substantiated repair, and is intended to promote consistency and reliability.
AMS CACRC Commercial Aircraft Composite Repair Committee
Guidelines for Repair Process Evaluation of Aluminum Bonded StructureAIR6291A (Current)11/26/2025
This SAE Aerospace Information Report (AIR) is intended to be used as a process verification guide for evaluating implementation of key factors in repair of metal bond parts or assemblies in a repair shop environment. This guide is to be used in conjunction with a regulatory approved and substantiated repair, and is intended to promote consistency and reliability.
AMS CACRC Commercial Aircraft Composite Repair Committee
Arresting Hook Installation, Land-Based AircraftARP1538C (Current)11/11/2025
This SAE Aerospace Recommended Practice (ARP) covers the recommended criteria and performance requirements for the design and installation of land-based aircraft emergency and operational arresting hooks for use on runway arresting systems. Design criteria for fully operational hooks and for carrier-based aircraft hook installations are contained in specification MIL-A-18717.
A-5B Gears, Struts and Couplings CommitteeNEW
Gross Weight, CG Position, and Rotor Flapping Prediction for a Compound Helicopter using Machine LearningF-0080-2024-13285/7/2024
This study investigates the use of machine learning (ML) models to estimate the gross weight (GW), the longitudinal position of the center of gravity (CGx), and 1/rev cyclic flapping angles (Δ1c and Δ1s) of a compound helicopter with three redundant controls - main rotor RPM, collective propeller thrust, and stabilator angle. Neural Network (NN), Gaussian Process for Regression (GPR), and Support Vector Machine (SVM) algorithms are employed to develop estimation models using supervised training. The airspeed, redundant controls, main rotor controls, aircraft attitudes, and main rotor torque are selected as input variables (predictors) to the models due to their accessibility through the aircraft Health and Usage Monitoring System (HUMS). The dataset is split into low-speed and high-speed regimes to compare the prediction accuracy and training cost of separate regime models against a combined full-regime model. Separate airspeed regime GPR models showed superior performance in GW estimation, with higher accuracy and cost-effectiveness compared to a single full-regime model. For CG estimation, GPR again outperformed NN and SVM, although the maximum outlier errors increase significantly if a 95% confidence interval is considered. Finally, for 1/rev cyclic flapping angle predictions, SVM estimations, though not superior to GPR or NN, were acceptable and had a significantly lower computational cost. The study also examined the importance of predictors, highlighting that, on average, certain predictors like rotor RPM and rotor torque are less influential, but their removal degraded performance and had no cost benefit.
Halder, Anubhav, Makkar, Gaurav, Gandhi, Farhan
Recurrent Neural Network Model for On-Board Estimation of the Side-Slip Angle in a Four-Wheel Drive and Steering Vehicle15-17-01-00039/23/2023
Abstract A valuable quantity for analyzing the lateral dynamics of road vehicles is the side-slip angle, that is, the angle between the vehicle’s longitudinal axis and its speed direction. A reliable real-time side-slip angle value enables several features, such as stability controls, identification of understeer and oversteer conditions, estimation of lateral forces during cornering, or tire grip and wear estimation. Since the direct measurement of this variable can only be done with complex and expensive devices, it is worth trying to estimate it through virtual sensors based on mathematical models. This article illustrates a methodology for real-time on-board estimation of the side-slip angle through a machine learning model (SSE—side-slip estimator). It exploits a recurrent neural network trained and tested via on-road experimental data acquisition. In particular, the machine learning model only uses input signals from a standard road car sensor configuration. The model adaptability to different road conditions and tire wear levels has been verified through a sensitivity analysis and model testing on real-world data proves the robustness and accuracy of the proposed solution achieving a root mean square error (RMSE) of 0.18 deg and a maximum absolute error of 1.52 deg on the test dataset. The proposed model can be considered as a reliable and cheap potential solution for the real-time on-board side-slip angle estimation in serial cars.
Giuliacci, Tiziano Alberto, Ballesio, Stefano, Fainello, Marco, Mair, Ulrich, King, Julian
682 Guidance for Air Transport Service Bulletins (TEST POPST CT and APPSEARCH)ARINC682 (Current)9/21/2022
This document provides industry guidance to supplement ATA standards and airframe requirements, addressing gaps and vague areas to move suppliers/vendors and airframers toward a common standard for format and wording in Vendor Service Bulletins (VSB) for Air Transport components. This document supplements the VSB guidance of iSpec 2200, providing clarity of requirements and resulting in a common standard wording and format of VSBs from all suppliers on all aircraft types. The guidance in this document is intended to be applied to VSBs created and released subsequent to the release of the guidance document and will not require the retroactive update of VSBs released prior to the creation and release of the guidance.
AOC AIR-GROUND DATA AND MESSAGE EXCHANGE FORMATARINC633-4 (Current)11/30/2021
The purpose of ARNC 633 is to specify the format and exchange of Aeronautical Operational Control (AOC) communications. Examples of ARINC 633 AOC Structures/Messages include: Flight Plan, Load Planning (i.e., Weight and Balance and Cargo Planning Load Sheets), NOTAMs, Airport and Route Weather data, Minimum Equipment Lists (MEL) messages, etc. The standardization of AOC messages enable the development of applications shared by numerous airlines on different aircraft types. Benefits include improved dispatchability and reduce operator cost.
Airlines Electronic Engineering Committee
Steering Control Systems - Heavy TrucksJ2425_202111 (Current)11/9/2021
This SAE Recommended Practice describes a laboratory test procedure and requirements for evaluating the characteristics of heavy-truck steering control systems under simulated driver impact conditions, as well as driver entry/egress conditions. The test procedure employs a torso-shaped body block that is impacted against the steering wheel.
Truck Crashworthiness Committee
Design and Performance Criteria Aircraft Crash AxesAS5402A (Current)4/23/2021
This SAE Aerospace Standard (AS) provides design criteria and performance tests for crash axes intended for use by aircraft crew members to assist in evacuation, extrication, fire fighting, or other emergency activities.
S-9A Safety Equipment and Survival Systems Committee
Standard Test Method for Measuring Forces During Normal Impact of a Soft Projectile on a Rigid Flat SurfaceAS6940 (Current)3/23/2021
This document describes a method for measuring forces during an impact between a soft or frangible projectile and a relatively rigid flat normal surface. The document describes the hardware and instrumentation required, as well as the processing and data reduction required to compute force. In this test, a projectile impacts one end of a long cylindrical bar with flat ends, called a Hopkinson bar. The impact occurs on the centerline of the bar in the axial direction. The diameter of the cylindrical bar is large compared to the lateral dimension of the projectile so that, during and after the impact, the projectile material moves radially or backward, rather than extruding around the perimeter of the impact surface. The bar is instrumented with strain gages at some distance from the impacted end to measure the longitudinal strain in the bar. The bar must be sufficiently long so that the duration of the impact is less than the time it takes for the transient stress wave generated by the impact to travel to the end of the bar and back to the location of the strain gages. This test is intended for measuring the transient force generated by the projectile when it impacts the cylindrical bar. Projectile breakup pattern data may also be captured during this test. The projectile material is expected to be soft compared with the bar material. Impact stresses are expected to be small compared with the yield strength of the bar material so that all deformations in the bar are elastic. The values stated in either SI units or inch-pound units are considered separate standards. The values stated in each system may not be exactly equivalent; therefore, each system must be considered as independent. This standard does not address all of the safety concerns associated with its use. It is the responsibility of each user of this standard to ensure that any safety issues are properly addressed.
G-28 Simulants for Impact and Ingestion Testing Committee
Vehicle Transport Unit Load Device (ULD)ARP1554D (Current)11/30/2020
The tests are static in nature to minimize complexity and cost of required testing facilities. As far as practical, applied static loads should take into account the combined static and dynamic loads anticipated in service. It is intended that tests shall be non-destructive in nature and not result in damage unless ultimate load conditions are employed. Test equipment and methods of testing described are not meant to be restrictive. Alternate equivalent methods to accomplish the desired results may be employed. In selected cases, tests may be repeated under ultimate load conditions when required for substantiation of analytical data. If this becomes necessary, the parts deformed may be removed and replaced prior to the retest.
AGE-2 Air Cargo
Monitoring Gross Weight and Center of Gravity Position: A Review of the Challenges and Current Estimation ApproachesF-0076-2020-1627210/5/2020
Weight and balance activities are widely recognized and understood as important steps in the operation and maintenance of an aircraft to ensure safe and efficient flight. From the pilot's perspective, the operational limits and maneuverability of the aircraft are directly linked to the weight and balance of the aircraft. From a structural perspective, fatigue damage can vary significantly with center of gravity position and gross weight. In-flight center of gravity and gross weight estimation has been pursued for many years with varying success. One of the major challenges is the lack of data to verify an estimation model, since these parameters cannot be easily measured using sensors in flight. This paper reviews in detail the requirement and challenges of accurately monitoring center of gravity and gross weight. In addition, a survey of published work on the estimation of these values is provided. These efforts are divided into four categories: helicopter dynamic models, performance charts, state estimation, and machine learning methods.
Cheung, Catherine, To, Davis
Air Cargo Unit Load Devices - Performance Requirements and Test ParametersAS36100C (Current)9/29/2020
This SAE Aerospace Standard (AS) defines the minimum performance requirements and test parameters for air cargo unit load devices requiring approval of airworthiness for installation in an approved aircraft cargo compartment and restraint system that complies with the cargo restraint requirements of Title 14 CFR Part 25, except for the 9.0-g forward ultimate inertia force of § 25.561 (b)(3)(ii).
AGE-2 Air Cargo
History of Commercial Aircraft New Tire Qualification TestingAIR5651 (Current)9/18/2020
This SAE Aerospace Information Report (AIR) is intended to provide a historical account of testing methods used during the years for Commercial Aircraft New Tire certification.
A-5C Aircraft Tires Committee
Aircraft Asset Lifecycle and Digital Data Standards OverviewAIR7501 (Current)9/18/2020
This SAE Aerospace Information Report (AIR) reviews technical, operational, and maintenance data being exchanged between key stakeholders in aerospace asset lifecycle and data standards available for such exchanges. It identifies gaps and non-availability of data standards in certain areas. The scope of the current document is limited to aircraft operations, maintenance and disposal stages post-build phase, and does not include the detailed interactions during the aircraft build phase.
G-31 Electronic Transactions for Aerospace Committee
Flexure Testing of Hydraulic Tubing Joints and Fittings by Planar Resonant Vibration (Free-Free Beam)AIR1529B (Current)5/6/2020
This Aerospace Information Report (AIR) establishes flexure test procedures to determine and classify the fatigue strengths of reconnectable or permanent hydraulic tube joints. The procedure is intended for conducting flexure tests of fittings and joints for hydraulic tubing materials such as AMS 5561 steel, AMS 4944 titanium and MIL-T-7081 aluminum alloy, mounted as free-free resonant beams. Of particular advantage are the inherent simplicity of test setup, minimum restraint from a test fixture, low power requirements, short test duration, and ease of varying stress level.
G-3, Aerospace Couplings, Fittings, Hose, Tubing Assemblies
Aerospace - Passive Side Stick Unit General Requirements for Fly-by Wire Transport and BusinessARP6001B (Current)4/23/2020
This SAE Aerospace Recommended Practice (ARP) provides recommendations for design and test requirements for a generic “passive” side stick that could be used for fly-by wire transport and business aircraft. It addresses the following: The functions to be implemented The geometric and mechanical characteristics The mechanical and electrical interfaces The safety and certification requirements
A-6A3 Flight Control and Vehicle Management Systems Cmt
Fire Containment Cover - Operation and UseARP6905 (Current)4/23/2020
This SAE Aerospace Recommended Practice (ARP) provides guidelines for the effective operation and use of fire containment covers (FCCs). Technical Standard Orders (TSOs) C203 and C90e (and later revisions) incorporate AS6453, and provide the Minimum Performance Standards (MPS) for an FCC design. The net and pallet used with the FCC must be approved using the updated net and flammability requirements in TSO C90e and later revisions. However, fire containment performance also requires this equipment is properly used. Fire safety is compromised when FCCs are used in an inadequate manner.
AGE-2 Air Cargo
SUV Kinematics during a Steer-Induced Rollover Resolved Using Consumer-Grade Video, Laser Scans and Match-Moving Techniques2020-01-06424/14/2020
Rollover crashes are complex events that generate motions in all six degrees of freedom (6DOF). Directly quantifying the angular rotations from video can be difficult and vehicle orientation as a function of time is often not reported for staged rollover crashes. Our goal was to evaluate the ability of using a match-moving technique and consumer-grade video cameras to quantify the roll, pitch and yaw angles and angular velocities of a rollover crash. We staged a steer-induced rollover of an SUV at 106 km/h. The vehicle was fitted with tri-axial accelerometers and angular rate sensors, and five consumer-grade video cameras (2 on tripods, 2 on drones, 1 handheld, ~30 fps) captured the event. Roll, pitch and yaw angles were determined from the video using specialized software. We then compared the vehicle orientation angles from the video data to the integrated angular rate data measured by onboard sensors, and also compared the angular rates from the differentiated video data to the angular rates measured directly by the sensors. We found that both methods of measuring the 3D angles and angular rates generated similar results. The integrated sensor data drifted a maximum of 13° relative to the video-based angles, with RMS differences of ±2.7° or less when the drift was removed. The differentiated video data did not drift relative to the sensor data, with RMS differences of ±0.22 rad/s or less. These findings indicate that both methods generate similar results and are suitable for reconstructing rollovers. Given the drift we observed in the integrated sensor data, we recommend using angle measurements from the video to quantify the amount of drift in integrated sensor data if accurate knowledge of the vehicle’s orientation as a function of time is important.
Young, Cole R., King, David J., Siegmund, Gunter P.
New Integrated Vehicle Dynamics Control System Based on the Coordination of AFS, DYC, and ED for Improvements in Vehicle Handling and Stability10-04-02-00091/27/2020
An integrated vehicle dynamics control system aiming to improve vehicle handling and stability by coordinating active front steering (AFS), direct yaw control (DYC), and electric differential system is developed in this article. First, an electric differential system for electric vehicle, composed of two sets of bi-PMS, in-wheel motors connected in parallel and supplied by a single five-leg inverter, one on the front axle and one on the rear axle, is designed. However, each set is controlled by a proposed sliding mode backstepping control, which has replaced the hysteresis controllers in the conventional direct torque control (DTC), can obviously reduce the torque ripple, and provide better speed tracking performance using sliding mode speed controllers. Second, an integrated control system which coordinates AFS and DYC braking system is designed by using a stability index, based on stability domain in the phase plane portrait, and a gain scheduling parameter to improve vehicle steerability and maintain vehicle stability during extreme driving situations. Simulation results confirm the effectiveness of the proposed integrated vehicle dynamics control system and the overall improvements in vehicle handling and stability.
Aouadj, Norediene, Hartani, Kada, Fatiha, Mekri
A Recommended Method of Analytically Determining the Competence of Hydraulic Telescopic Cantilevered Crane BoomsJ1078_202001 (Historical)1/15/2020
This analysis applies to crane types as covered by ASME B30.5.
Cranes and Lifting Devices Committee
Design of the Control Surfaces for an Aircraft Destined to the Competition SAE BRAZIL AERODESIGN2019-36-02141/13/2020
This work aims to present a methodology for the design of conventional control surfaces for light aircraft. Based on renowned aeronautical engineering references and standards, the theoretical framework presents the concepts of calculation for each flight phase particularity for each control surface in addition to a database with intervals of surfaces and their respective deflections of various aircraft. The methodology used takes into account the suggested steps for the aircraft design, where the dimensions are present in the preliminary design, according to the characteristics intended in the conceptual stage to develop conventional control surfaces aiming at the simplicity of design and the optimal response of control. The use of MATLAB and CFD software for data calculation and iterations are essential for the correct observance and evaluation of the obtained results. A comparative table and graphs will be elaborated for better visualization of the efficiency and behavior of each dimensioned model aiming at the best levels of acceptability according to the norms used in the design of aircraft, observing their occurrence through flight analysis and direct feedback of the pilot. Finally, the optimally sized surface will be used.
Takano e Silva, Yoko Lucila, Kieling, Antonio Claudio, de Azevedo, Emile Diana Mendes, Vilaça, Neilson Luniere, Janzen, Renan Araújo, de Oliveira, Sanches Ismael
Numerical optimization of independent suspension hardpoint2019-36-01541/13/2020
The present work aims to use complex tools for the calculation of vehicle dynamics, using optimization analysis. The study was applied to a single seat off-road prototype that has independent suspension, Double A or WishBones type, both on the front and rear axles and whose main objective will be the analysis of the prototype suspension arms fixing points. A multi-body model was created by MotionView software and straight-line acceleration and deceleration analyzes were applied to obtain better longitudinal load transfer ratios for the axes, besides the force measurements for the arm connections during these events. After the creation of the multi-body model, some studies using optimization tools, through HyperStudy software, were performed in order to obtain the new positions of the attachment points in the chassis, achieving a better dynamic suspension design. The new points change the longitudinal load transfer design and generate controlled alteration between predefined parameters in the behavior of the camber and toe in angles resulting in a different suspension arm geometry. In addition, the new geometry also had a pickup analysis of forces for comparison between models. At the end of the study, the prototype model generated allows full comparison of the macro operation of the prototype, and allowing the developers to evaluate if this model is more efficient and robust than the previous one. The optimization tool allows to find important results that allow the studied competition prototype to gain competitive advantages contributing to achieve better results and a better design.
Alvim, Olavo Fava Furtado, Silveira, Marcio Eduardo
De-Orbit Device for SmallSatsTBMG-3570212/1/2019
To decrease de-orbit time and allow for higher-altitude orbits of small satellites, researchers at NASA and the University of Florida have developed a retractable drag device capable of modulating drag area while providing 3-axis stabilization. The device increases area without increasing mass, increasing the ability to control rotation and attitude in 12U, 15-kg CubeSats and other small satellites.
Evaluating Effects of Roll Stiffness Change at Front and Rear Axles on Vehicle Maneuverability and Stability2019-28-240611/21/2019
To cater the push towards “Vehicle Light Weighting”, both sprung and unsprung mass are being reduced. This results in reduced stiffness and thus has a profound undesirable effect on the overall vehicle handling. To understand the effect of different reduction ratios of sprung to unsprung mass; it is desired to understand how changes in stiffness affect the overall vehicle handling characteristics. Therefore, the study was conducted to experiment with different values of roll stiffness, at both front and rear axles and comparing the frequency response and phase change of Yaw Gain observed through a Pulse Input test. The present work is further correlated with subjective feedback to predict the shift in vehicle balance and handling characteristics.
Reuben, Eric Pranesh, Budhiraja, Raghav, N, Sreeraj, K, Rakesh, Singh, Amardeep
Research on Control Algorithm of Active Steering Control Based on the Driver Intention2019-01-506411/4/2019
Active steering technology can improve the operability of the driver by the involvement to the steering system. Driver is the major controller of the vehicle Therefore, the involvement of advanced technologies including the active steering technology shouldn’t interfere with the intention of the driver, and the driver should still have great control of the vehicle. The aim of this paper is to solve the problem of the driver’s control when the active steering system works to improve the flexibility of the low speed and the stability of the high speed, and the active steering model based on the driver’s steering intention is established. Through the CarSim simulation software, this paper adopts 9 parameters related to the vehicle steering of the DLC (Double Line Change). And PCA (Principal Component Analysis) algorithm, a tool of statistical analysis, is applied to select 4 parameters which can stand for the DLC from the 9 parameters, which makes the data processing easier. Through the 4 parameters, this model divide the driver’s steering intention into four categories (emergency steering, normal steering, turn left and turn right) having different weights of active steering angle by clustering analysis, which ensures the driver get better control to the vehicle than traditional active steering system at different steering conditions. Finally, the feasibility of this model is verified by the simulation results through the comparison with the curve of the ideal steering at DLC steering condition.
Zhang, Pengcheng, Zheng, Hongyu
A Comparative Study on ESC Drive and Brake Control Based on Hierarchical Structure for Four-Wheel Hub-Motor-Driven Vehicle2019-01-505111/4/2019
Electronic Stability Control (ESC) is an important measure to proactively guarantee vehicle safety. In this paper, the method of four-wheel hub-motor torque control is compared with the traditional single-wheel hydraulic brake control in ESC system. The control strategy adopts the hierarchical structure. In upper controller, the stability of the vehicle is identified by threshold method, the additional yaw moment control uses a way to get the moment including feedforward and feedback parts based on the linear quadratic regulator (LQR). The medium controller is tire slip rate control, in order to get the optimal target slip rate from the upper additional yaw moment, a method of quadratic programming to optimize the longitudinal force is proposed for each wheel. The inputs of tire state for the magic tire model is introduced so as to calculate the target slip rate from the target longitudinal force. The lower controller is wheel cylinder pressure control and motor torque control which is realized by Carsim ideal control. Finally, through Co-simulation of Carsim/Simulink in the condition of open steering wheel loop for Sine with Dwell Waveform and closed driver loop for Double Lane Change, the results show that, at high speed and with large and frequent steering wheel angle, restricted by the motor torque, the method of motor torque control is not as effective as hydraulic brake control, but have the same effects and better driver seating comfort and handing stability at middle or low speed. If the control torque range of motor at high speed can be improved or the AFS and SBW can be applied to the field of ESC in the future, the drive motor control can be further developed in the application of the hub-motor-driven vehicle.
Lin, Chen, Pei, Xiaofei, Guo, Xuexun
Axle Torque Distribution to Improve Vehicle Handling and Stability2019-01-503711/4/2019
The majority of the fully electric vehicles currently on the market have a basic drivetrain configuration, consisting of multiple electric motors, which promise considerable performance enhancements in terms of vehicle behavior and active safety. A significant advantage was achieving measurable benefits in terms of vehicle cornering response through controlling the individual drivetrains. This paper presents an axle torque distribution method to improve a 4WD vehicle steering performance. The method can automatically adjust the output drive torque of the front and rear motors of the vehicle to change the vehicle yaw rate before ESP intervention, and at the same time remain the driver torque demand unchanged. In this paper we present a feedback yaw rate controller. When the estimated yaw rate differs from the actual yaw rate with a pre-defined small threshold, a yaw rate control is active, the purpose of the controller is to reduce the vehicle understeer characteristic. The simulation and experimental test results shows that this proposed method can reduce the vehicle understeer characteristic and improve the vehicle handling and stability performance.
Wu, Aibin, Li, Chao, Zhao, Yongqiang, Cui, Jinlong
Performance Standard for Child Restraint Systems in Transport Category AirplanesAS5276/1 (Current)10/31/2019
This SAE Aerospace Standard (AS) defines minimum performance standards and related qualification criteria for add-on child restraint systems (CRS) which provide protection for small children in passenger seats of transport category airplanes. The AS is not intended to provide design criteria that could be met only by an aircraft-specific CRS. The goal of this standard is to achieve child-occupant protection by specifying a dynamic test method and evaluation criteria for the performance of CRS under emergency landing conditions.
Aircraft SEAT Committee
Setting Preload in Heavy-Duty Wheel BearingsJ2535_201910 (Current)10/7/2019
This SAE Recommended Practice applies to the four primary, large volume applications in the class 7-8 heavy-duty market place, as specified in SAE J1842: a “N” trailer axle b “R” powered rear axle c “FF / FG” nonpowered front axle d “P” trailer axle This document applies to on-highway applications. It is not applicable to those applications that exceed the GAWR ratings or the load line restrictions listed in columns “A,” “B,” and “C” of Table 1. Load lines are measured from the inboard bearing cup backface as shown in 3.4. This document establishes preload force values only. The methodology to obtain these force values must be determined by the fastener supplier and/or axle assembler. This document reviews the bearing system. It is NOT intended to prescribe (new or existing) axle and/or hub manufacturers’ ratings and/or specifications.
Truck and Bus Wheel Committee
Lightweight Exosuit Combines Robotics and Functional ApparelTBMG-3526310/1/2019
Between walking and running, human gaits can cover a wide range of speeds; for example, at low speeds, the metabolic rate of walking is lower than that of running in a slow jog. The opposite also is true: at high speeds, the metabolic cost of running is lower than that of speed-walking.
A Dictionary of Terms for the Dynamics and Handling of Single Track Vehicles (Motorcycles, Scooters, Mopeds, and Bicycles)J1451_201909 (Current)9/24/2019
Terminology within this document is limited to the dynamics and handling characteristics of single track, two-wheeled vehicles.
Motorcycle Technical Steering Committee
Stability of Wheel Tractors during Braking2019-01-21429/15/2019
The dynamic distribution of normal reactions between the axles of the wheeled tractor has a significant impact on the stability against skidding and the wheeled tractor braking effectiveness. At the same time, the clarification of the normal reactions distribution between the axles allows to choose more rational braking forces distribution between the axles. It is shown that the best way to ensure the highest braking efficiency is the braking mode when the rear wheels of the tractor are at the blocking limit. An assessment of the expediency of installing brake mechanisms on only one axle of the tractor was made. The increase of braking efficiency of wheeled tractors with all brake wheels provided that they ensure directional stability is considered. The laws of braking forces distribution between the axles of wheel tractors for different sequence of wheels locking are determined. Using the method of partial accelerations an improved method for estimating the effect of a brake system on the stability of wheeled tractor is proposed. The criterion in the form of angular acceleration in the road plane ώz, by the value and sign of which one we can estimate the operational stability of the brake mechanisms has obtained.
Podrigalo, Mikhail, Kholodov, Mykhailo, Klets, Dmytro, Dubinin, Yevhen, Savchenkov, Borys, Koryak, Alexander, Rudzinskyi, Volodymyr, Viktoriia, Zadorozhnia, Polianskyi, Oleksandr
Study on Vehicle Spin Tendency during Braking on Differential mu Surfaces in Four Wheeled Automobile Vehicle2019-01-21149/15/2019
A four-wheeled automobile during braking event in which left and right wheels of the vehicle are on different mu surfaces, has high chances of experiencing spin, which may lead to stability issues on vehicle. This paper intends to provide a mathematical approach to predict the deceleration at which vehicle will spin during braking in a differential mu surface, and determine the effect of influencing parameters on the extent of the vehicle spin tendency. This paper also provides a correlation between theoretical vs actual decelerations for vehicles to exhibit vehicle spin tendency. This paper helps in providing sufficient aid/tool for system designer to predetermine the vehicle spin at early level of system designs and make necessary amendments at initial stage of prototype development rather than late changes, to create a product which gives safe driving experience.
Nedunuri, Kartheek, K, Rajakumar, Lalasure, Santosh
Application of Optimal Control Method to Path Tracking Problem of Vehicle10-03-03-00148/26/2019
Path tracking is an essential stage for vehicle safety control. It is more newsworthy than ever in the automotive context and especially for autonomous vehicle. The study proposes an optimal control method for path tracking problem in inverse vehicle handling dynamics. The proposed method generates an expected trajectory which guarantees minimum clearance to the prescribed path by identifying the optimal steering torque input. Based on this purpose, the path tracking problem, which is treated as an optimal control problem, is then solved by local collocation method and mesh refinement. Finally, a real vehicle test is executed to verify the rationality of the proposed model and methodology. The results show that using control variables as a mesh refinement function can capture the dramatic changes in state variables, and the efficiency improvement is more significant as the number of the grid points increases. The study can help drivers easily identify safe lane-keeping trajectories and area.
Liu, Yingjie, Cui, Dawei
Additional Comparison of Iced Aerodynamic Measurements on a Swept Wing from Two Wind Tunnels2019-01-19866/10/2019
Artificial ice shapes of various geometric fidelity were tested on a wing model based on the Common Research Model. Low Reynolds number tests were conducted at Wichita State University’s Walter H. Beech Memorial Wind Tunnel utilizing an 8.9% scale model, and high Reynolds number tests were conducted at ONERA’s F1 wind tunnel utilizing a 13.3% scale model. Several identical geometrically-scaled ice shapes were tested at both facilities, and the results were compared at overlapping Reynolds and Mach numbers. This was to ensure that the results and trends observed at low Reynolds number could be applied and continued to high, near-flight Reynolds number. The data from Wichita State University and ONERA F1 agreed well at matched Reynolds and Mach numbers. The lift and pitching moment curves agreed very well for most configurations. This confirmed results from previous tests with other ice shapes that indicated the data from the low Reynolds number tests could be used to understand iced-swept-wing aerodynamics at high Reynolds number. This allows ice aerodynamics testing to be performed at low Reynolds number facilities with much lower operating costs and generate results that are applicable to flight Reynolds number.
Lee, Sam, Broeren, Andy, Woodard, Brian, Lum, Christopher, Smith, Timothy
Whirl Flutter Investigation of Hingeless ProprotorsF-0075-2019-145805/13/2019
Hingeless proprotor whirl flutter in cruise flight is investigated using comprehensive rotorcraft analysis codes CAM- RAD II and RCAS. Generic hingeless proprotor designs include conventional soft-inplane and stiff-inplane rotors operating at cruise tip speeds typical of existing tiltrotor systems, and a rotor which exhibits higher frequencies and operates at much lower cruise tip speed than existing rotor designs. The effects of blade elasticity, density, speed of sound, unsteady aerodynamics, and realistic airfoil tables on whirl flutter speed are examined. The US Army and NASA have been developing a new wind tunnel test system, TiltRotor Aeroelastic Stability Testbed (TRAST), and preliminary analysis for a notional TRAST hingeless rotor is also presented. The effects of precone, center of gravity, rotor rotational speed, and density on the TRAST whirl flutter stability are examined. CAMRAD II and RCAS show consistently excellent agreement with each other for wide variations of design variables and operating conditions.
Yeo, Hyeonsoo, Kreshock, Andrew
Design of Servo-Flap Helicopter Rotor Blades with Forward Swept WingtipsF-0075-2019-145375/13/2019
Helicopters with performance enhancing aft swept blade wingtips are used for both military and commercial purposes. Up until now, there are no research projects studying helicopter blades with forward swept wingtips. A forward swept blade wingtip generates significant amounts of nose-up aerodynamic pitching moments with respect to the blade feathering axis. For a conventional pitch-horn rotor, this type of control system cannot effectively produce large enough nose-down pitching moments to counteract the nose-up pitching moments generated by the swept portion of the blade. The main goal of this paper is to generate ample nose-down pitching moments via servo-flap aerodynamic action to overcome the swept blade's nose-up pitching moments while maintaining an adequate control safety margin for flight. These nosedown pitching moments depend on (i) the size of the servo-flap, (ii) the distance from the servo-flap pitch axis to blade feathering axis, and (iii) the servo-flap location with respect to the blade. There are three additional reasons for selecting a servo-flap rotor control as the primary control system when designing the blade with forward swept wingtips. (i) The overall blade chordwise center of gravity (c.g.) moves forward due to the forward swept wingtip, resulting in a lighter blade with less ballast weight. (ii) The required aerodynamic downloads on the flap is reduced in flight due to positive blade local angle of attacks generated by the blade's nose-up pitching moments. Positive servo-flap aerodynamics on the flap unloads the main rotor blade required lift and improves the blade flight performance. (iii) The feedback control system incorporated into the existing production blades is used to reduce the flap control requirements and to provide stability for the rotor system in flight. Several numerical examples are investigated to verify the potential blade design with forward swept effect.
Wei, Fu-Shang, Peters, David
Development of a Gun-Launched Rotary-Wing Micro Air VehicleF-0075-2019-144845/13/2019
This paper describes the development of a compact and re-configurable rotary-wing micro air vehicle (MAV) that is capable of sustained hover and could potentially be launched from a 40 mm grenade launcher in the future. Launching the vehicle as a projectile up to the point of operation could significantly improve the mission range for these energy constrained platforms. The MAV design used coaxial rotors with foldable blades, a thrust-vectoring mechanism for pitch and roll control, and a strict constraint on the outer diameter, which was relaxed to 52 mm for this study. Yaw control was accomplished by using a specialized counter-rotating motor that is composed of two independently controlled motors. Passive unfolding of the coaxial rotor blades utilizing centrifugal force was demonstrated. The vehicle attitude was stabilized in hover using a closed-loop proportional-derivative controller implemented on a 1.7 gram custom autopilot. Through systematic trimming and tuning of the feedback gains, the vehicle was able to achieve stable hover. When the vehicle was subjected to large impulsive pitch and roll perturbations, the feedback controller was able to successfully reject the disturbance and return the vehicle to a stable hover within a second. In parallel, an analogue of the flying vehicle or a "dummy" was built and launched using a pneumatic canon to understand the dynamics of the vehicle during the projectile phase without risking the actual flying vehicle. The launch demonstrated that with the right center of gravity location, the present vehicle configuration could be stable during the projectile flight even without fins.
Denton, Hunter, Kang, Hao, Hrishikeshavan, Vikram, Benedict, Moble
Effect of Ground Proximity on the Regressive Lag Mode during Ground Resonance : An Experimental StudyF-0075-2019-145775/13/2019
This paper studies aerodynamic effects of ground on regressive lag mode damping during ground resonance. The experimental investigation is performed on a scaled helicopter model built to simulate the ground resonance scenario. The study involves both stationary as well as dynamic (oscillating) ground conditions. Experiments are conducted by measuring lead-lag damping at different rotor speeds (in the ground resonance regime) for different collective inputs. Results show that ground and its dynamics have a significant effect on regressive lead-lag mode damping during ground resonance. NOTATION e Hinge offset h Distance between rotor hub center and pitch/roll axis Ib Lead-lag moment of inertia for blade kG Thrust augmentation factor Mb Mass of the blade R Rotor radius Rcg Center of gravity of blade Ω Rotor anglular speed θ0 Collective input of blade pitch IGE In ground effect IMU Inertial Measurement Unit MPM Matrix Pencil Method OGE Out of ground effect RLM Regressive lead-lag mode damping during ground resonance.
Nair, Salini, Ramachandran, Akshay, Pandey, Bittesh, Mohan, Ranjith, M, Rohith
Landing Gear Shock Absorption Testing of Civil AircraftARP5644 (Historical)4/17/2019
The intent of this document is to provide recommended practices for conducting shock absorption testing of civil aircraft landing gear equipped with oleo-pneumatic shock absorbers. The primary focus is for Part 25 aircraft, but differences for Part 23, 27, and 29 aircraft are provided where appropriate.
A-5B Gears, Struts and Couplings Committee NEW Name Goes Her
Has Electronic Stability Control Reduced Rollover Crashes?2019-01-10224/2/2019
Vehicle rollovers are one of the more severe crash modes in the US - accounting for 32% of all passenger vehicle occupant fatalities annually. One design enhancement to help prevent rollovers is Electronic Stability Control (ESC) which can reduce loss of control and thus has great promise to enhance vehicle safety. The objectives of this research were (1) to estimate the effectiveness of ESC in reducing the number of rollover crashes and (2) to identify cases in which ESC did not prevent the rollover to potentially advance additional ESC development. All passenger vehicles and light trucks and vans that experienced a rollover from 2006 to 2015 in the National Automotive Sampling System Crashworthiness Database System (NASS/CDS) were analyzed. Each rollover was assigned a crash scenario based on the crash type, pre-crash maneuver, and pre-crash events. The Insurance Institute for Highway Safety ESC availability database was matched to each NASS/CDS case vehicle by the vehicle make, model, and model year. ESC effectiveness was computed using the quasi-induced exposure method. From 2006-2015, control loss was a factor in 29.7% of the 1,339,407 vehicle rollovers. ESC was standard equipment in 177,644 of vehicles involved in these events. Our study estimated that ESC was effective in reducing the overall number of rollover crashes by 13.3%. ESC was more effective at reducing rollover crashes due to control loss with a reduction of 50.6%. ESC is particularly effective for high center of gravity vehicles such as light trucks, SUVs, and vans. Travelling too fast for the road conditions was the most common reason rollovers due to control loss were not prevented despite the presence of ESC.
Riexinger, Luke, Sherony, Rini, Gabler, Hampton
Robust Model Predictive Control for Path Tracking of Autonomous Vehicle2019-01-06934/2/2019
Path tracking is one of the critical technologies in the autonomous vehicle. Its performance may be seriously affected by disturbance resulting from unpredictable environment like changes in road friction coefficient and parameter uncertainty such as cornering stiffness and mass caused by errors of measurement. Besides, since the vehicle system consisting of many systems is an extremely complex nonlinear system, it is almost impossible for us to establish a precise model of a vehicle especially when it is moving. These inevitable factors influence the control accuracy and even threaten the stability and safety of the vehicle system. This paper proposed a promising solution to this problem, robust MPC (Model Predictive Control) combined with the optimal preview controller for path tracking problems of an autonomous vehicle. The state space model in tracking error variables of a passenger vehicle used for path tracking application is established. In order not to regard road curvature as additive disturbance, the error dynamics of the vehicle for a given road curvature is transformed to the error model deviating from the steady state trajectory. A reachable set of the error state is computed on-line based on bounded disturbance. The constraints of nominal state and input are obtained, which ensure state and input constraints are satisfied in presence of disturbances and uncertainties. Then the preview controller is proposed to improve the tracking performance. Simulation using a passenger vehicle is conducted on different road friction coefficient, mass uncertainty and road bank angles, respectively, which are all treated as additive disturbance. Simulation results show the effectiveness of the proposed framework under the test of double lane change.
Yu, Jiaxing, Guo, Xuexun, Pei, Xiaofei, Chen, Zhenfu, Zhu, Maolin, Gong, Bian
Development and Control of Four-Wheel Independent Driving and Modular Steering Electric Vehicles for Improved Maneuverability Limits2019-01-04594/2/2019
Electric vehicles are capable of more flexible drivetrain configurations, such that driving dynamics of each wheel could be controlled independently to increase its stability and maneuverability bounds. We hereby propose a configuration consisting of four wheel independent driving and front and rear axle modular steering. The vehicle implements drive-by-wire technology, which means the control program running on vehicle control computer will have direct control authority of the vehicle under normal driving conditions, based on inputs of higher level systems such as human drivers and autonomous driving programs. Both the torque allocation on four wheels and the steering allocation on axles are completely independent on the mechanical hardware level, thus the vehicle is able to harness adverse contact conditions with confidence. A slip-aware model-free control method for torque allocation and steering is proposed and inspected in the paper, with digital model of a modified SUV simulated for validation, and the vehicle responses with and without such controller are compared to elaborate its strengths. Such control method has more safety margin under close-to-limits driving conditions with presence of tire slip. The control method along with drive-by-wire features also enhance driving safety by correcting excessive inputs by human drivers. Additionally, a comprehensive index reflecting the stability and maneuverability of the vehicle is also introduced and based on which a model-based controller is designed and compared.
Yang, Haoguang, Liu, Chen, Shi, Jiongming, Zheng, Gangtie
Safety and Lateral Dynamics Improvement of a Race Car Using Active Rear Wing Control2019-01-06434/2/2019
As the forward speed of a car increases, the safety of the vehicle and the driver becomes a more significant concern. Active aerodynamic control can effectively enhance the lateral stability of high speed vehicles over tight cornering maneuvers. A split rear wing has been proposed. By means of manipulating the attack angles for the right and/or left parts of the split rear wing, a favorable yaw moment may be achieved to ensure the lateral stability of the vehicle. However, active control of the split rear wing has not been adequately explored. This paper proposes a novel active split rear wing, which can improve the lateral stability over tight cornering maneuvers, and will not degrade the longitudinal dynamics of the vehicle. A Linear Quadratic Regulator (LQR) based controller for the active split rear wing is designed using a linear vehicle model. In order to examine the performance of the active split rear wing, Numerical simulation is carried out using the LQR based controller and a yaw-plane vehicle model designed in MATLAB. The effectiveness of the proposed active split rear wing is demonstrated by the results derived from the numerical simulation.
Hammad, Mohammed, Qureshi, Khizar, He, Yuping
Inertia Tensor and Center of Gravity Measurement for Engines and Other Automotive Components2019-01-07014/2/2019
A machine has been developed to measure the complete inertia matrix; mass, center of gravity (CG) location, and all moments and products of inertia. Among other things these quantities are useful in studying engine vibrations, calculation of the torque roll axis, and in the placement of engine mounts. While the machine was developed primarily for engines it can be used for other objects of similar size and weight, and even smaller objects such as tires and wheels/rims. A key feature of the device is that the object, once placed on the test table, is never reoriented during the test cycle. This reduces the testing time to an hour or less, with the setup time being a few minutes to a few hours depending on the complexity of the shape of the object. Other inertia test methods can require up to five reorientations, separate CG measurement, and up to several days for a complete test. The device uses a system of pivots, springs, and three sensors to get the three moments and three products of inertia, plus the CG location. Object mass is measured separately on a scale. A stable pendulum arrangement is used to get the CG location, two moments and one product of inertia. A rotating plate with springs is used to get one moment of inertia, and a load cell is used to get two products of inertia. For typical passenger-vehicle engine-size objects accuracy is on the order of 2.5 mm for CG, 1% for moments of inertia, and 2% of the smallest moment for products of inertia. The three sensors used are an inclinometer, a load cell, and a rotary encoder. Custom software is used to record the measurements from the sensors. The software performs all calculations, guides the user through the test sequence, and checks for possible testing errors.
Andreatta, Dale A., Heydinger, Gary, Zagorski, Scott, Guenther, Dennis
A Novel Dual Nonlinear Observer for Vehicle System Roll Behavior with Lateral and Vertical Coupling2019-01-04324/2/2019
The study of vehicle coupling state estimation accuracy especially in observer-based vehicle chassis control for improving road handling and ride comfort is a challenging task for vehicle industry under various driving conditions. Due to a large amount of life safety arising from vehicle roll behavior, how to precisely acquire vehicle roll state and rapidly provide for the vehicle control system are of great concern. Simultaneously, uncertainty is unavoidable for various aspects of a vehicle system, e.g., varying sprung mass, moment of inertia and position of the center of gravity. To deal with the above issues, a novel dual observer approach, which combines adaptive Unscented Kalman Filter (AUKF) and Takagi-Sugeno (T-S), is proposed in this paper. A full-car nonlinear model is first established to describe vehicle lateral and vertical coupling roll behavior under various road excitation. Considering the variation of vehicle sprung mass in the movement process, an AUKF approach is adopted to identify the sprung mass by tuning various road classification process variances of the vehicle system in real time. Then, by combing the identification sprung mass via AUKF observer and nonlinear coupling dynamics of tire lateral force, modified T-S model-based observer is developed to estimate the vehicle coupling roll state. The stability conditions for proposed T-S observer are deduced using linear matrix inequalities (LMI). Finally, using a high-fidelity CarSim® software platform, the proposed dual observer approach is verified through a J-turn test, and simulations show that more accurate are obtained by comparing with the traditional T-S approach. The research achievements develop a reasonable algorithm to apply to the vehicle chassis control system.
Wang, Zhenfeng, Li, Fei, Qin, Yechen, Li, Dong, Ma, Gongbo, Ma, Jinyuan
Occupant Kinematics and Loading in Low Speed Lateral Impacts2019-01-10274/2/2019
Instrumented human subject and anthropomorphic test device (ATD) responses to low speed lateral impacts were investigated. A series of 12 lateral collisions at various impact angles were conducted, 6 near-side and 6 far-side, with each test using an ATD and one human subject. Two restrained female subjects were utilized, with one positioned in the driver seat and one in the left rear seat. Each subject was exposed to 3 near-side and 3 far-side impacts. The restrained ATD was utilized in both the driver and left rear seats, undergoing 3 near-side and 3 far-side impacts in each position. The vehicle center of gravity (CG) change in velocity (delta-V) ranged from 5.5 to 9.4 km/h (3.4 to 5.8 mph). Video analysis was used for quantification and comparison of the human and ATD motions and interactions with interior vehicle structures. Human head, thorax, and low back accelerations were analyzed. Peak human subject head resultant accelerations ranged from 0.9 to 36.8 g’s. Peak human subject thorax and low back lateral accelerations ranged from 1.0 to 17.1 g’s and 1.3 to 12.7 g’s, respectively. The ATD was instrumented with various sensors, including a tri-axial head accelerometer and 6-axis load cells in the upper neck, lower neck, and lumbar spine. Peak ATD head resultant accelerations ranged from 3.6 to 33.5 g’s. Peak ATD upper and lower neck compression ranged from -47.4 to -991.5 N and -52.1 to -740.6 N, respectively. Peak ATD lumbar compression ranged from -72.3 to -402.1 N. Cervical and lumbar shear loading and moments are also reported.
Furbish, Christopher, Welcher, Judson, Brink, Justin, Jones, Brian, Swinford, Scott, Anderson, Robert
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