Browse Topic: Roll
To facilitate the development and application of bulb-flat titanium alloys in aerospace and automotive industries, this study selects TC4 as the research material and employs finite element simulation software to simulate the hot rolling process of TC4 bulb flat titanium. The temperature field, strain field, and metal flow velocity in each rolling pass are analyzed, and rolling experiments are conducted after optimizing the roll pass system. The results indicate that during the rolling process of TC4 bulb flat titanium, the head undergoes relatively smaller deformation, resulting in a slower temperature decrease, whereas the waist experiences greater deformation and a faster temperature drop. A significant temperature difference exists between the core and surface, which can be mitigated by appropriately increasing the roll temperature to reduce heat transfer. Prior to the K4 pass, the billet temperature drops to a level that may affect rolling performance, necessitating furnace reheating. Strain increases progressively with each rolling pass, with higher values observed at the waist compared to the head. A gradual strain transition occurs at the interface between the head and waist. Furthermore, the irregular design of the roll pass leads to a considerable difference in metal flow velocity between the upper and lower surfaces. During the K1 pass rolling, this imbalance can cause the guide guard to be displaced upward and result in roll wrapping. Without altering the roll diameter, shifting the entire roll pass system toward the side with higher metal flow velocity effectively reduces the linear velocity and prevents these issues, ensuring stable billet rolling. Rolling experiments successfully produced the final TC4 bulb flat titanium, thereby validating the feasibility of the optimized roll pass system and the rationality of the selected rolling parameters. It provides the possibility for its development and application in fields such as aircraft and automobiles.
This paper proposes a nonlinear and robust State-Dependent Riccati Equation (SDRE) combined with H∞ control architecture for brake- by-wire systems, specifically designed to handle severe tire-road friction variations and μ-split scenarios. The primary objective is to maximize deceleration capabilities while rigorously maintaining yaw stability, trajectory tracking, and passenger comfort through jerk limitation. Situated within the domain of active safety, this research addresses robustness against real-world uncertainties by utilizing a high-fidelity 14-degree-of-freedom vehicle model that accounts for longitudinal, lateral, and yaw dynamics, suspension-induced pitch and roll effects, and nonlinear tire behavior with explicit load transfer. To ensure near-optimal slip tracking under variable surface conditions, the system employs online friction estimation via Extended and Unscented Kalman Filters (EKF/UKF) fusing wheel and IMU data to adaptively adjust slip targets. The control strategy is bifurcated: the SDRE component manages dominant nonlinearities through state-dependent gains to prevent wheel lock-up, while the H∞ component provides robust disturbance rejection against parametric uncertainties such as mass variations and sensor noise. Control efforts are distributed via a Quadratic Programming (QP) torque allocator featuring anti-windup mechanisms and explicit saturation handling to compensate for lateral drift during μ-split braking. Validation is conducted through a Model- in-the-Loop (MIL) to Software-in-the-Loop (SIL) pipeline using scenarios including wet surfaces and panic braking. Simulation results demonstrate enhanced yaw stability and controlled deceleration profiles compared to conventional baselines, ensuring computational feasibility for automotive Electronic Control Units (ECUs).
Cu-Fe alloys exhibit excellent performance, and increasing Fe content reduces costs. However, high-Fe Cu-Fe alloys exhibit limited formability at room temperature, while warm rolling improves their processability. This research investigates the effect of rolling temperature on the microstructural transformations and texture development in the Cu-10Fe alloys. The experimental result is that during cold rolling, the morphology of Fe phases is mainly fibrous. With the rolling temperature rising, the microstructural morphology of Fe phases becomes globular / elliptical. The difference is that with the increase in rolling temperature, the average grain size of the Cu-10Fe alloy first decreases and then increases. The matrix microstructure remains dominated by deformed grains, with significant recovery observed at 500 °C. The Fe-phase microstructure primarily consists of substructured grains, and dynamic recovery intensifies with rising temperature. During cold rolling, high dislocation density and localized strain heterogeneity lead to dispersed texture orientations and low strength. In contrast, warm rolling promotes dislocation climb and dynamic recovery, triggering partial recrystallization. This reduces randomly oriented grains, enhances the strength and continuity of specific textures, and establishes a more concentrated texture distribution. This forms a structure with fine recrystallized grains embedded within deformed grains, exhibiting slightly lower strength than cold-rolled samples but better elongation. These findings reveal the crucial role of deformation temperature in controlling microstructure transformation and texture evolution, especially by regulating the recovery and recrystallization behaviors of Cu-10Fe alloys. The above results hope to provide some theoretical and experimental basis for a new approach to improve processing technologies for new Cu-Fe-based composites.
The canard configuration has been widely adopted in short-range missiles. However, its main drawbacks include difficulties in roll control and a limited angle-of-attack (AoA) range. Compared to conventional canard missiles, the addition of a pair of control surfaces (referred to as “aileron”) behind the canard control surfaces achieves decoupling between the roll channel and pitch-yaw channel. To investigate the influence of ailerons on the aerodynamic characteristics of canard configuration missiles, numerical simulations were conducted for two typical flow conditions: subsonic (Mach 0.5) and supersonic (Mach2.0). The results show that the introduction of ailerons increases the normal force of missiles, causes the center of pressure to shift forward, and reduces the static stability of missiles, thus enhancing their maneuverability. When the ailerons control the roll channel, the effectiveness of the rolling moment remains consistent over the entire AoA range without adverse effects. However, when the canards control the pitch channel, the interference caused by the deflection of the canards on the ailerons leads to increased lift and generates additional nose-up pitching moments, which reduces the pitching moment effectiveness of the missile.
Hybrid bearings, which pair traditional bearing-steel raceways with ceramic rolling elements, can offer improved performance over full-metal bearings, particularly in aerospace applications. Because rolling-element bearings are critical components, effective condition monitoring is essential to prevent in-flight failures and support proactive maintenance strategies. Wear-debris monitoring is widely used in these applications to detect and diagnose bearing fault modes. To compare degradation behavior and monitoring signatures, bearing life tests were conducted on hybrid and full-metal bearings under matched Hertzian stress conditions. The results showed that differences in degradation curves between the two bearing types were small relative to the overall variability in bearing life. Additionally, hybrid bearings that develop rolling-element pitting were observed to progress toward raceway spall formation. This paper was presented at ERF Forum 51 but has been updated with new findings addressing questions over the effect of impact energy on the degradation rate between hybrid and full-metal bearings.
This paper utilizes a combined experimental and modeling approach to investigate techniques for improving the forward-flight roll-control authority of a Quadrotor Biplane Tailsitter (QBiT). QBiT is a mechanically simple, efficient hover/cruise aircraft whose roll authority in forward flight is traditionally limited by differential propeller-torque-based control. The two roll-control enhancement techniques investigated are propeller canting and the use of ailerons. A 2-kg instrumented QBiT platform was developed and flight tested to collect high-fidelity flight data across multiple flight regimes including hover, transition, cruise, and coordinated turns. A flight dynamics model was developed and validated using wind tunnel measurements and flight-test data. Flight tests showed that the cant-only configuration exhibited limited roll authority during coordinated turns due to motor control saturation, whereas the cant-plus-aileron configuration provided improved roll performance. Using test data from forward-flight roll excitation maneuvers, roll-control authority was evaluated both in the time domain and frequency-domain. The results showed that adding ailerons increased forward-flight roll-control authority by about 2.3 times from analyzing the flight data and by up to 2.6 times based on the flight dynamics simulations.
Full state feedback offers theoretically guaranteed multi-axis stability, making it superior to conventional PID controllers. There is however one drawback, a full state controller has a mathematical difficulty if the B matrix is not square and thus not invertible. This is the case for helicopters with 6 degrees of freedom and 4 inceptors. Variations of linear quadratic regulators are a work around, however complexity dramatically increases. Best would be a direct solution to the original problem. This is the breakthrough result of this paper. This paper documents an approach which removes the analysis roadblock by partitioning the 6 x 6 system "A" matrix into two groups of 4 x 4 matrices. The 4x4 matrices are individually stabilized with full state gain matrices. One matrix is designated “Driver Matrix” which provides actuator commands. The other matrix is designated "Reference Matrix" which provides references. The two matrices are coupled together by requiring that the driver matrix follow references generated by the reference matrix. With each matrix individually stabilized, the coupled combination is also stabilized. Computation of flight dynamics states (u, v, w, p, q, r) is shared between the matrices. Initial results are very encouraging, showing an originally sluggish, heavy lift helicopter having now concise decoupled responses to pitch and roll commands. Stability derivatives are recomputed during flight allowing coverage over the whole flight envelope. A handling qualities task has been defined to relocate a 40 ft standard seaborne container directed by a pilot in a ground control station. Cooper Harper ratings of this task have demonstrated favorable Level 1 handling qualities if use is made of an automated lateral repositioning command.
This study investigates the dynamics and associated vibratory loads of an underactuated swashplate-less rotor and its impact on the flight dynamics of a small-scale helicopter powered by this rotor via a combined experimental and computational approach. Unlike prescribing cyclic pitch using a swashplate, here the pitch is a response to the 1/rev cyclic rotor speed input. This is enabled on the current two-bladed rotor using a skewed lag hinge that utilizes the cyclic speed variation to produce lagging motion and subsequently pitching the blades in a cyclic fashion (ƍ4 coupling) for generating the pitch and roll control moments. One of the key dynamic characteristics that distinguishes this rotor from a conventional swashplate-controlled rotor is that the two blades have dissimilar pitch and flap responses leading to high fixed-frame vibratory loads. Results show that a large 1/rev vertical shear force is transferred to the fuselage resulting in half-peak-to-peak loads of +/−0.67g. The flap responses of the two blades being out of phase caused a net inertial force, which was the dominant contributor to the vibratory vertical shear force. Upon removal of the flap hinge, the vertical shear force was reduced by almost 85% while increasing the control moment authority by 50%. The inertial moment about the rotor axis generated by cyclic lagging nearly balances the moment due to the angular acceleration (Ω ) of the rotor, which significantly reduced the dynamic torque requirement from the motor.
This paper describes the characteristics of the Leonardo Advanced Tiltrotor Aircraft (ATA) concept, focusing on the relationship between goals, targeted improvements and enabling design features. The paper shows the design drivers such as performance, operational capabilities, and maneuverability and it describes how the attributes of the concept originated, showing trade-off and compromises approached during the genesis of the concept. The design drivers are translated into areas of interests, including download, drag, aerodynamic efficiency, rolling and yawing inertia, detectability, maintainability and engine retrofit ability. Finally, these areas are linked to the physical features of the concept, showing how they have been selected and combined to achieve the best overall benefit at platform level.
This study presents a comprehensive analysis of single-rotor failure tolerance for a classical octocopter configuration, examining both hover and forward flight at the best range speed. Using a state-of-the-art eVTOL comprehensive analysis to retrim the octocopter post-failure, the redistribution of rotor thrust, torque, and power following individual rotor failures was quantified, along with resulting aircraft-level power penalties. In hover, orthogonal rotors to the failed rotor provide primary lift compensation, the opposing rotor operates mostly unchanged, and the four opposite spinning rotors primarily provide pitch/roll moment compensation. This results in a total aircraft level power increase of approximately 10.4%, roughly half that of comparable hexacopters. In forward flight, at best range cruise speed, load redistributions were again calculated for various individual rotor failures. In the worst case, a maximum individual rotor torque increase of 62% and power increase of 108% was observed, while total aircraft power requirements increased between 7-12%. These results demonstrate the fault-tolerant capabilities of octocopters and provide practical guidance for propulsion system sizing, energy management, and failure-case assessment on classical octocopters.
This study presents an integrated vehicle dynamics framework combining a 12-degree-of-freedom full vehicle model with advanced control strategies to enhance both ride comfort and handling stability. Unlike simplified models, it incorporates linear and nonlinear tire characteristics to simulate real-world dynamic behavior with higher accuracy. An active roll control system using rear suspension actuators is developed to mitigate excessive body roll and yaw instability during cornering and maneuvers. A co-simulation environment is established by coupling MATLAB/Simulink-based control algorithms with high-fidelity multibody dynamics modeled in ADAMS Car, enabling precise, real-time interaction between control logic and vehicle response. The model is calibrated and validated against data from an instrumented test vehicle, ensuring practical relevance. Simulation results show significant reductions in roll angle, yaw rate deviation, and lateral acceleration, highlighting the effectiveness of the proposed approach. Overall, the framework offers a scalable and robust foundation for developing adaptive stability control systems in modern four-wheeled vehicles
Vehicles with a high center of gravity (CG) and moderate wheel track, like compact Sport Utility Vehicles (SUVs), have a relatively low Static Stability Factor (SSF) and thus are inherently less stable and more susceptible to rollover crashes. Moreover, to be more maneuverable in highly populated urban areas, a smaller Turning Circle Diameter (TCD) is necessary. Here, Variable Gear Ratio (VGR) steering systems have major benefits over traditional Constant Gear Ratio (CGR) systems in terms of enhancing both roll stability and agility. To adapt VGR steering systems to a particular vehicle dynamic, Full Vehicle (FV) and Driver-in-the-Loop (DIL) simulations are utilized. Using this method, exact calibration is possible according to realistic driving conditions so that the VGR steering C-factor curve is properly tuned for optimal handling in on-center, off-centre, and transitional areas of the Steering Wheel Angle (SWA). Primary performance measures—e.g., SWA gradients at different lateral accelerations and C-factor changes for different SWA ranges—are examined in the DIL environment to maintain a natural feel during steering. In addition, DIL simulation allows a check on cycloidal curve character, manufacturing asymmetry, and its effect on total drive performance.
Specialized robots that can both fly and drive typically touch down on land before attempting to transform and drive away. But when the landing terrain is rough, these robots sometimes get stuck and are unable to continue operating. Now a team of Caltech engineers has developed a real-life Transformer that has the “brains” to morph in midair, allowing the dronelike robot to smoothly roll away and begin its ground operations without pause. The increased agility and robustness of such robots could be particularly useful for commercial delivery systems and robotic explorers.
In this work, a vision-based solution is developed to address the challenge of landing on a ship deck with precision and accuracy. For an autonomous landing, it is important to have a fast and accurate pose estimation system along with a reliable control strategy. This research uses fractal ArUCo markers instead of multiple separate markers to allow smooth pose estimation at different heights. Pose estimates are further improved using an Extended Kalman Filter, and a tracking algorithm then uses these estimates to guide the landing. A four degree-of-freedom (roll, pitch, heave and sway) simulator platform was built and used to validate the algorithm. The accuracy of the vision system is compared against that of a motion capture system. Real-world experiments were performed on different quadrotors to demonstrate tracking and landing on the platform with sway, roll, and pitch motions. The results show that the system is efficient and reliable in achieving safe and successful landings. The proposed landing system is concluded to be applicable for landings on the deck of the ship under sea-state 4.
This paper investigates the use of multi-modal cueing through full-body haptic feedback to enhance pilot-vehicle system (PVS) performance, reduce mental workload (MWL), and increase situational awareness (SA) in both good and degraded visual environments (GVE/DVE). Piloted simulations were conducted using an H-60-like flight dynamics model in a virtual reality (VR) motion-based simulator, evaluating two ADS-33-like mission task elements (MTEs) – precision hover and slalom – under visual-only and combined visual and haptic feedback conditions in both GVE and DVE. The H-60 flight dynamics were augmented with a dynamic inversion (DI)- based stability augmentation system (SAS), implementing rate-command/attitude hold (RCAH) response type on the roll, pitch, and yaw axes and altitude hold response type on the vertical axis. The SAS was designed to achieve Level 1 handling qualities per ADS-33 standards. The full-body haptic cueing strategy leveraged an outer-loop DI control law, which provided vibrotactile feedback to cue desired roll, pitch, and yaw attitudes to the pilot. Roll cues were delivered via tactors mounted on the upper arms, pitch cues via tactors on the chest and back, and yaw cues via tactors on the calves. Eight test subjects participated in the piloted simulations, including three U.S. Navy test pilots and five subjects with different flying experiences. Results indicated that haptic feedback significantly improved hover performance, reducing MWL and enhancing SA, particularly in DVE. However, in the slalom task, predefined haptic guidance misaligned with pilots’ individual control strategies, leading to performance degradation. This finding highlights the need for pilot-specific adaptive haptic feedback to mitigate inconsistencies in dynamic maneuvering tasks.
In the last years, new rotorcraft configurations have increased the attention among industries, through which the tiltrotor one due to its capability of combining both rotorcraft and aircraft advantages. However, there are situations where the vertical take-off mode could be enhanced in hard environmental and flight conditions. Therefore, to address this challenge, this work aims to develop a methodology to characterize a roll take-off model for a general tiltrotor configuration in such situations. By combining the integration of the equation of motion and geometrical assumptions, the runway distance is determined for an acceptable range of nacelle tilting angles. The process is developed by meeting the requirements defined by the regulations, combining the aircraft certification standards (CS23 and CS25) with the available tiltrotor certification basis from the FAA project #TC3419RC-R. Following the Nominal application, a sensitivity analysis is carried out, which studies the main effects on the results by varying one variable at a time in terms of weight, wing-loading, and disk-loading.
It might look like a roll of chicken wire, but this tiny cylinder of carbon atoms — too small to see with the naked eye — could one day be used for making electronic devices ranging from night vision goggles and motion detectors to more efficient solar cells, thanks to techniques developed by researchers at Duke University.
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