Browse Topic: Vehicle acceleration
This paper presents a meshless large eddy simulation approach for rotorcraft wake prediction, using a vortex particle method accelerated on GPUs. The solver couples a rotor model with a vortex particle wake model, employing the Fast Multipole Method for computational efficiency and implementing viscous diffusion through Particle Strength Exchange and Core Spreading Methods. GPU acceleration achieves speed-ups of up to 10x compared to CPU execution. The solver’s predictions are validated against experimental data, showing excellent agreement. Effects of time step size, numerical integration schemes, viscous models, and particle overlap factors on simulation accuracy and computational cost are systematically analyzed. This GPU-based vortex particle framework provides a fast, accurate, and scalable tool for rotorcraft wake simulations.
The transition phase of eVTOL aircraft poses a challenge in balancing energy efficiency and stability. This study presents the development and evaluation of an automatic flight control system for eVTOL transition phases, focusing on minimizing energy consumption while ensuring robust performance. The control architecture implements a hybrid response type combining Translational Rate Command below 5 knots and Acceleration Command Speed Hold above 5 knots, with control allocation dynamically adjusted based on airspeed and rotor shaft angle. Stability analysis reveals surge mode instability at high shaft angles due to negative speed stability derivatives, stabilized through carefully tuned feedback control. The system demonstrates Level 1 handling qualities against bandwidth, quickness, and disturbance rejection criteria when evaluated against MIL-DTL-32742 and MIL-STD-1797B standards. Simulation results verify the control system's ability to maintain precise acceleration/deceleration rates and attitude control while ensuring passenger comfort through limited pitch excursions. The control strategy achieves minimum energy transitions by locking rotor shaft angles to optimal schedules while avoiding excessive hub moments. Flight test maneuvers developed specifically for conversion phases confirm the system's capability to execute efficient transitions within defined performance boundaries. This research establishes a framework for certifiable eVTOL flight control systems that balance energy efficiency with robust performance across diverse flight regimes.
ABSTRACT Shipboard operations present a unique set of challenges to the pilot-vehicle system. This work addresses problems specific to piloted rotorcraft in the simulated shipboard environment, namely cueing and ship motion, and represents the completion of a three-year effort focused on fixed-base, pilot-in-the-loop rotorcraft flight simulations. Instructors from the United States Naval Test Pilot School, with extensive operational and test experience, participated in the study. Two cueing sets, one for the approach task and another for the hover task, were developed in order to provide intuitive guidance of cyclic and collective inputs. Data were gathered for each task with the cueing system both on and off. The evaluation criteria used to determine the usefulness of the provided cueing were based on pilot workload assessment, profile performance and inceptor activity. The approach task cueing provides the pilot with a preset approach profile defined by altitude and airspeed cueing, while the hover task cueing provides the pilot with a top-down view of helicopter position over the landing spot and a representation of the vehicle’s acceleration vector. Different control response types were assessed, as well as different ship motion intensities. Both tasks show that use of the developed cues allows pilots to achieve greater precision with less overall workload when compared to task performance without cueing available.
ABSTRACT Updates to the military rotorcraft handling qualities specification are currently being considered that address the high-speed flight regime envisioned for the Future Vertical Lift (FVL) platform of the US Army. The US Army's National Rotorcraft Technology Center (NRTC) project "Rotorcraft Handling Qualities Requirements for Future Configurations and Missions" was a U.S. Government and Industry co-funded three-year research project. A project team that features industry and academia have developed and evaluated a set of Mission Task Elements (MTEs) that are defined to address rotorcraft high-speed handling qualities. The High Speed Acceleration/Deceleration MTE was designed to provide suitable coverage in ADS-33 for handling qualities in Low/High Speed Transitional flight regimes (e.g. rotor-borne to wing-borne flight). The MTE objectives, descriptions, and performance criteria were developed via a series of piloted simulation sessions at each of the four teams' simulation facility. Formal evaluations were then conducted by US Army and contractor test pilots at the four simulator facilities, each featuring a unique high-speed platform, including two tiltrotor configurations, an X2 Technology compound helicopter, and a generic winged compound helicopter. To enhance the MTE evaluation process, baseline control law (CLAW) configurations were varied to achieve different handling qualities levels. Quantitative measures based on task performance and qualitative measures based on pilot ratings, comments and debrief questionnaires were used to assess MTE effectiveness. The piloted simulation results demonstrated that the High Speed Acceleration/ Deceleration MTE provided a suitable and effective means to evaluate Transitional handling qualities between low and high speed flight, although some refinements may still be warranted.
This paper describes development and testing of a low-cost device mounted on in the pilot seat of a rotorcraft simulator with the aim of improving the perceived realism of the flight. The device acting vertically from the bottom of the seat is used to communicate changes of acceleration in the vertical direction corresponding to heave movement of the simulated aircraft. A bespoke flight simulator system was developed, featuring modular design and virtual reality (VR) visualisation to enable comparative testing with a full motion system. Objective analyses have shown similarities between the two motion cueing configurations when contrasted with only using visual cues.
ABSTRACT
Aeromechanics analysis is performed using the comprehensive analysis code RCAS (Rotorcraft Comprehensive Analysis System) to study the transient conversion maneuver of a tiltrotor. The analytical model is based on the XV-15 research tiltrotor aircraft in size and dynamic characteristics. A generic (not representative of XV-15) tiltrotor control system is developed to simulate conversion maneuver. Hover and cruise performance of the present XV-15 analytical model is validated against available test data. The conversion calculation begins with a trim analysis at hover, which is followed by the conversion maneuver. During the maneuver analysis, the pilot control model is activated to fly the aircraft following a desired airspeed profile and minimum altitude change. Time histories of vehicle dynamics, rotor controls, rotor flapping, rotor performance and blade structural loads are investigated for various transient conversion maneuvers. The aircraft acceleration during the transient maneuver has a significant influence on the rotor performance and loads.
Since it was first adopted in 1987, Aeronautical Design Standard ADS-33 has been through four major revisions, and the Mission Task Elements (MTEs) used to qualitatively assess aircraft handling qualities have been expanded to cover scout, attack, utility, and cargo missions. However, even the current version of ADS-33 (ADS-33E-PRF) focuses on the hover/low-speed flight regime with limited coverage of high speed (140-150 kts) and conventional rotorcraft configurations. The ADS-33E MTEs are based on legacy vehicles and were developed at an early stage of rotorcraft fly-by-wire technology. The U.S. Army National Rotorcraft Technology Center recently completed a multi-year project to develop MTEs for future high-speed configurations and missions using a series of simulation studies. This paper documents a flight test assessment of two high-speed MTEs—Break Turn and High-Speed Acceleration/Deceleration—using a UH-60M Black Hawk. The MTEs were deemed suitable for assessing high speed handling qualities of the UH-60M. The results of the flight test provided recommended updates to the task descriptions and course cueing requirements, and helped validate the desired and adequate task performance tolerance.
ABSTRACT This article describes an approach to learning gearbox operating conditions, defined by torque, rotational speed, and power, from acceleration data. Learning operating conditions paves the way to learning gearbox state-of-health because health indicators have to be normalized with respect to operating conditions to avoid false alarms. Moreover, because operational data is vastly larger than data associated with faults, representation learning is easier (and often only possible) from the operational data. The article compares two different solutions, one based on a multi-layer perceptron and the other on a recurrent network using the first four statistical moments as input features. The decision process, including heuristics and domain knowledge, used for selection of the network topology is described in detail. Models were found most effective in estimating the mechanical power transmitted through the gearbox and provided improvements over the second moment (RMS) alone.
Items per page:
50
1 – 50 of 432