Optimal Acceleration Procedure from Launch to Maximum Speed in High-Speed Dynamic Soaring

2020 ◽  
Author(s):  
Gottfried P. Sachs
Keyword(s):  
High Speed ◽  
Maximum Speed ◽  
Dynamic Soaring

scholarly journals Performance Enhancement by Wing Sweep for High-Speed Dynamic Soaring

Aerospace ◽  
2021 ◽  
Vol 8 (8) ◽  
pp. 229
Author(s):  
Gottfried Sachs ◽  
Benedikt Grüter ◽  
Haichao Hong
Keyword(s):  
High Speed ◽  
Degrees Of Freedom ◽  
Performance Enhancement ◽  
Aerodynamic Characteristics ◽  
Progressive Increase ◽  
Maximum Speed ◽  
Horizontal Shear ◽  
Dynamic Soaring ◽  
Speed Performance ◽  
Wing Sweep

Dynamic soaring is a flight mode that uniquely enables high speeds without an engine. This is possible in a horizontal shear wind that comprises a thin layer and a large wind speed. It is shown that the speeds reachable by modern gliders approach the upper subsonic Mach number region where compressibility effects become significant, with the result that the compressibility-related drag rise yields a limitation for the achievable maximum speed. To overcome this limitation, wing sweep is considered an appropriate means. The effect of wing sweep on the relevant aerodynamic characteristics for glider type wings is addressed. A 3-degrees-of-freedom dynamics model and an energy-based model of the vehicle are developed in order to solve the maximum-speed problem with regard to the effect of the compressibility-related drag rise. Analytic solutions are derived so that generally valid results are achieved concerning the effects of wing sweep on the speed performance. Thus, it is shown that the maximum speed achievable with swept wing configurations can be increased. The improvement is small for sweep angles up to around 15 deg and shows a progressive increase thereafter. As a result, wing sweep has potential for enhancing the maximum-speed performance in high-speed dynamic soaring.

scholarly journals Trajectory Optimization and Analytic Solutions for High-Speed Dynamic Soaring

Aerospace ◽  
2020 ◽  
Vol 7 (4) ◽  
pp. 47
Author(s):  
Gottfried Sachs ◽  
Benedikt Grüter
Keyword(s):  
Mach Number ◽  
Vehicle Dynamics ◽  
Trajectory Optimization ◽  
High Speed ◽  
Analytic Solutions ◽  
Flight Mechanics ◽  
Maximum Speed ◽  
Dynamic Soaring ◽  
Mechanics Model ◽  
Flight Mode

Dynamic soaring is a non-powered flight mode that enables extremely high speeds by extracting energy from thin shear wind layers. Trajectory optimization is applied to construct solutions of the maximum speed achievable with dynamic soaring and to determine characteristic properties of that flight mode, using appropriate models of the vehicle dynamics and the shear wind layer. Furthermore, an energy-based flight mechanics model of high-speed dynamic soaring is developed, with reference made to trajectory optimization. With this model, analytic solutions for high-speed dynamic soaring are derived. The key factors for the maximum speed performance are identified and their effects are determined. Furthermore, analytic solutions for other, non-performance quantities of significance for high-speed dynamic soaring are derived. The analytic solutions virtually agree with the results achieved with the trajectory optimization using the vehicle dynamics model. This is considered a validation of the energy-based model yielding analytic solutions. The analytical solutions are also valid for the high subsonic Mach number region involving significant compressibility effects. This is of importance for future developments in high-speed dynamic soaring, as modern gliders are now capable of reaching that Mach number region.

scholarly journals Specific Absolute Velocity Thresholds during Male Basketball Games Using Local Positional System; Differences between Age Categories

2021 ◽  
Vol 11 (10) ◽  
pp. 4390
Author(s):  
Carlos Sosa ◽  
Alberto Lorenzo ◽  
Juan Trapero ◽  
Carlos Ribas ◽  
Enrique Alonso ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Real Time ◽  
Effect Size ◽  
High Speed ◽  
Maximum Speed ◽  
Large Effect Size ◽  
Moderate Effect Size ◽  
Positional System ◽  
Moderate Effect ◽  
Distance Zone

The aim of this study was (I) to establish absolute specific velocity thresholds during basketball games using local positional system (LPS) and (II) to compare the speed profiles between various levels of competitions. The variables recorded were total distance (TD); meters per minute (m·min); real time (min); maximum speed (Km h−1), distance (m), percentage distance, and percentage duration invested in four speed zones (standing–walking; jogging; running; and high-speed running). Mean and standard deviation (±SD) were calculated, and a separate one-way analysis of variance was undertaken to identify differences between competitions. TD (3188.84 ± 808.37 m) is covered by standing–walking (43.51%), jogging (36.58%), running (14.68%), and sprinting (5.23%) activities. Overall, 75.22% of the time is invested standing–walking, jogging (18.43%), running (4.77%), and sprinting (1.89%). M·min (large effect size), % duration zone 2 (moderate effect size); distance zone 4 (large effect size), and % distance zone 4 (very large effect size) are significantly higher during junior than senior. However, % distance zone 1 (large effect size) and % duration zone 1 (large effect size) were largely higher during senior competition. The findings of this study reveal that most of the distance and play time is spent during walking and standing activities. In addition, the proportion of time spent at elevated intensities is higher during junior than in senior competition.

High-Speed End Milling Using a Feedforward Control Architecture

1996 ◽  
Vol 118 (2) ◽  
pp. 178-187 ◽  
Author(s):  
E. D. Tung ◽  
M. Tomizuka ◽  
Y. Urushisaki
Keyword(s):  
High Speed ◽  
Feedforward Control ◽  
End Milling ◽  
Phase Error ◽  
Cutting Speed ◽  
Frequency Domain Analysis ◽  
Maximum Speed ◽  
Drive Control ◽  
Machining Errors ◽  
Feedforward Controller

Experiments are performed for end milling aluminum at 15,000 RPM spindle speed (1,508 m/min cutting speed) and up to 3 m/min table feedrate using an experimental machine tool control system. A digital feedforward controller for feed drive control incorporates the Zero Phase Error Tracking Controller (ZPETC) and feedforward friction compensation. The controller achieves near-perfect (±3 μm) tracking over a 26 mm trajectory with a maximum speed of 2 m/min. The maximum contouring error for a 26 mm diameter circle at this speed is less than 4 μm. Tracking and contouring experiments are conducted for table feedrates as high as 10 m/min. Frequency domain analysis demonstrates that the feedforward controller achieves a bandwidth of 10 Hz without phase distortion. In a direct comparison of accuracy, the machining errors in specimens produced by the experimental controller were up to 20 times smaller than the errors in specimens machined by an industrial CNC.

Interface Features of the DDR SDRAM Memory Test Diagnostic Device

2021 ◽  
Vol 26 (3-4) ◽  
pp. 282-290
Author(s):  
S.V. Volobuev ◽  
◽  
V.G. Ryabtsev ◽  
Keyword(s):  
Data Transmission ◽  
High Speed ◽  
Maximum Speed ◽  
Diagnostic Device ◽  
Semiconductor Memory ◽  
Storage Devices ◽  
Memory Modules ◽  
Electronic Elements ◽  
Synchronization Scheme ◽  
Test Diagnostics

The I/О synchronization scheme plays an important role in achieving maximum speed and reliability of data transmission during memory operation. This paper presents the interface architecture of the DDR SDRAM test diagnostic device. It was demonstrated that the proposed interface components provide the formation of a bidirectional synchro signal for gating written and read data when performing test diagnostics of chips and DDR SDRAM memory devices. Compared to traditional methods, the proposed interface components were made on integrated electronic elements, which reduced the size and power consumption. It has been established that the use of a multiphase synchronization system to implement the interface eliminated the use of delay lines, the disadvantages of which are large dimensions and the complexity of changing the delay time. The interface components under consideration are intended for use in test diagnostics devices that have a multiprocessor structure, which increases the speed of forming test actions and reference reactions. The performed functional modeling and debugging of strobe signal generators confirmed the feasibility of the designs. The proposed interface of the test diagnostics device allows performing test diagnostics of modern high-speed chips and semiconductor memory modules at the operating frequency, which increases the reliability of the results obtained. Interface components can be used by manufacturers of test diagnostics tools for modern high-speed storage devices.

scholarly journals Numerical Study of Longitudinal Inter-Distance and Operational Characteristics for High-Speed Capsular Train Systems

Vehicles ◽  
2022 ◽  
Vol 4 (1) ◽  
pp. 30-41
Author(s):  
Bruce W. Jo
Keyword(s):  
Error Rate ◽  
High Speed ◽  
Position Control ◽  
Numerical Study ◽  
Design Parameters ◽  
Maximum Speed ◽  
Integer Number ◽  
Vehicle Speed ◽  
Start Time ◽  
Distance Control

High-speed capsular vehicles are firstly suggested as an idea by Elon Musk of Tesla Company. Unlike conventional high-speed trains, capsular vehicles are individual vessels carrying passengers and freight with the expected maximum speed of near 1200 [km/h] in a near-vacuum tunnel. More individual vehicle speed, dispatch, and position control in the operational aspect are expected over connected trains. This numerical study and investigation evaluate and analyze inter-distance control and their characteristics for high-speed capsular vehicles and their operational aspects. Among many aspects of operation, the inter-distance of multiple vehicles is critical toward passenger/freight flow rate and infrastructural investment. In this paper, the system’s equation, equation of the motion, and various characteristics of the system are introduced, and in particular control design parameters for inter-distance control and actuation are numerically shown. As a conclusion, (1) Inter-distance between vehicles is a function of error rate and second car start time, the magnitude range is determined by second car start time, (2) Inter-distance fluctuation rate is a function of error rate and second car start time, however; it can be minimized by choosing the correct second car start time, and (3) If the second car start time is chosen an integer number of push-down cycle time at specific velocity error rate, the inter-distance fluctuation can be zero.

scholarly journals Modal Kinematic Analysis of a Parallel Kinematic Robot with Low-Stiffness Transmissions

Robotics ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 132
Author(s):  
Paolo Righettini ◽  
Roberto Strada ◽  
Filippo Cortinovis
Keyword(s):  
High Speed ◽  
Parallel Robots ◽  
Maximum Speed ◽  
Kinematic Structure ◽  
End Effector ◽  
New Approach ◽  
Working Space ◽  
Modes Of Vibration ◽  
Parallel Kinematic ◽  
Actuated Joints

Several industrial robotic applications that require high speed or high stiffness-to-inertia ratios use parallel kinematic robots. In the cases where the critical point of the application is the speed, the compliance of the main mechanical transmissions placed between the actuators and the parallel kinematic structure can be significantly higher than that of the parallel kinematic structure itself. This paper deals with this kind of system, where the overall performance depends on the maximum speed and on the dynamic behavior. Our research proposes a new approach for the investigation of the modes of vibration of the end-effector placed on the robot structure for a system where the transmission’s compliance is not negligible in relation to the flexibility of the parallel kinematic structure. The approach considers the kinematic and dynamic coupling due to the parallel kinematic structure, the system’s mass distribution and the transmission’s stiffness. In the literature, several papers deal with the dynamic vibration analysis of parallel robots. Some of these also consider the transmissions between the motors and the actuated joints. However, these works mainly deal with the modal analysis of the robot’s mechanical structure or the displacement analysis of the transmission’s effects on the positioning error of the end-effector. The discussion of the proposed approach takes into consideration a linear delta robot. The results show that the system’s natural frequencies and the directions of the end-effector’s modal displacements strongly depend on its position in the working space.

The Mechanism of Rapid Running in the Ghost Crab, Ocypode Ceratophthalma

1973 ◽  
Vol 58 (2) ◽  
pp. 327-349 ◽  
Author(s):  
MALCOLM BURROWS ◽  
GRAHAM HOYLE
Keyword(s):  
High Speed ◽  
Effective Length ◽  
Maximum Speed ◽  
Ghost Crab ◽  
High Speeds ◽  
Intact Crab ◽  
Leg Movements

1. Ocypode ceratophthalma has a maximum speed of 2.1 m/sec when running on a measured track with a base of hard-packed sand. Speed increases linearly with the width of the carapace up to a certain size, beyond which larger crabs run slower than smaller ones. 2. The crab does not run at these high speeds by making extremely rapid movements as these data seemed to require. The highest frequency of leg movements observed was 20 Hz. 3. Electromyographs of muscles used in running, made from the freely running, intact crab, showed asymmetry in the motoneurone discharges. Extensors and flexors in the meropodites of legs on the leading side frequently showed only a maintained tonus and could not have contributed to the running movements. Those on the trailing side showed alternation synchronous with stepping. 4. It is concluded that the crab mainly pushes itself along rather than using a push-pull combination. 5. Three pairs of legs are commonly used in running. Legs 2 and 4 of one side move together with leg 3 of the opposite side and provide a tripod of support. At the highest speeds only legs 2 and 3 of one side are used to provide thrust alternately. 6. The high speed is achieved by the crab leaping through the air as it steps, thereby increasing the effective length of the steps.

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