scholarly journals Effects of Asymmetries on the Dynamics of Motorized Momentum Exchange Tether and Payloads Injection Precision

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Naiming Qi ◽  
Yong Yang ◽  
Jun Zhao ◽  
Qilong Sun ◽  
Wenhui Zhang
Keyword(s):  
Pitch Angle ◽  
Gravity Gradient ◽  
Momentum Exchange ◽  
Coupling Analysis ◽  
Space Tether ◽  
Error Dynamic ◽  
The Difference ◽  
Error Dynamics ◽  
Yaw Angle ◽  
Exchange Principle

This paper presents the error dynamic model of motorized momentum exchange tether (MMET) based on the momentum exchange principle of space tether. The error dynamics are caused by the structural bias of the differences in tethers’ length and the difference in payloads’ mass. After that, the coupling analysis between orbit and attitude is presented. It is shown that, with increasing the differences in tethers’ length and payloads’ mass, the COM deviation of the MMET increases linearly. The numerical simulations of the MMET by considering the structural asymmetries are presented; the results show that the asymmetries have tiny influences on the orbit of the chief satellite by decreasing the apogee, which will change the instantaneous velocity at the apogee and affect the payload injection precision. What is more, the structural asymmetries have effects on the attitude elements (including the pitch angle and yaw angle); however, the effects could be weakened by the external torque. The structural asymmetries and gravity gradient torque have composite effects on the angular velocity of the propulsion tether.

scholarly journals Trajectory/Path-Following Controller Based on Nonlinear Jerk-Level Error Dynamics

2020 ◽  
Vol 10 (23) ◽  
pp. 8760
Author(s):  
Patrick Piprek ◽  
Michael M. Marb ◽  
Pranav Bhardwaj ◽  
Florian Holzapfel
Keyword(s):  
Equations Of Motion ◽  
Path Following ◽  
Control Law ◽  
Nonlinear Error ◽  
Error Dynamic ◽  
The Difference ◽  
Error Dynamics ◽  
And Performance ◽  
Traditional Approaches ◽  
Path Deviation

This study proposes a novel, nonlinear trajectory/path-following controller based on jerk-level error dynamics. Therefore, at first the nonlinear acceleration-based kinematic equations of motion of a dynamic system are differentiated with respect to time to obtain a representation connecting the translation jerk with the (specific) force derivative. Furthermore, the path deviation, i.e., the difference between the planned and the actual path, is formulated as nonlinear error dynamics based on the jerk error. Combining the derived equations of motion with the nonlinear error dynamics as well as employing nonlinear dynamic inversion, a control law can be derived that provides force derivative commands, which may be commanded to an inner loop for trajectory control. This command ensures an increased smoothness and faster reaction time compared to traditional approaches based on a force directly. Furthermore, the nonlinear parts in the error dynamic are feedforward components that improve the general performance due to their physical connection with the real dynamics. The validity and performance of the proposed trajectory/path-following controller are shown in an aircraft-related application example.

Multiscale Mutual Mode Entropy Based Coupling Analysis of Alpha Rhythm Electroencephalogram

2014 ◽  
Vol 574 ◽  
pp. 718-722
Author(s):  
Ning Ji ◽  
Jun Tan ◽  
An Shan Pei ◽  
Jia Fei Dai ◽  
Jun Wang
Keyword(s):  
Time Series ◽  
Clinical Evaluation ◽  
Brain Function ◽  
Alpha Rhythm ◽  
Physiological Status ◽  
Noise Resistance ◽  
Middle Aged ◽  
Coupling Analysis ◽  
Scale Change ◽  
The Difference

This paper presents the Multiscale Mutual Mode Entropy algorithm to quantify the coupling degree between two alpha rhythm EEG time series which are simultaneously acquired. The results show that in the process of scale change, the young and middle-aged differ from each other in terms of the coupling degree of alpha rhythm EEG and the difference grow clear gradually. So the Multiscale Mutual Mode Entropy can be used to analyze the coupling information of time series under different physiological status, and it also has good noise resistance. Besides, as an indicator of measuring brain function, in the future it can also come to the aid of clinical evaluation of brain function.

scholarly journals Analisis stabilitas tegangan pengisian baterai terhadap putaran kincir angin pada pembangkit listrik tenaga angin

JURNAL ELTEK ◽  
2020 ◽  
Vol 18 (1) ◽  
pp. 57
Author(s):  
Mira Esculenta Martawati
Keyword(s):  
Wind Power ◽  
Output Power ◽  
Pitch Angle ◽  
Alternative Energy ◽  
Power Plants ◽  
P Value ◽  
Wind Power Plants ◽  
The Difference ◽  
Market Needs ◽  
Turbine Speed

Pembangkit energi alternatif Saat ini semakin meningkat dikarenakan  berkaitan dengan semakin banyaknya kebutuhan pasar akan energi. Ada beberapa pembangkit energi alternatif yang sudah mulai dibangun antara lain pembangkit listrik tenaga angin. Pada umumnya pembangkit listrik tenaga angin didirikan di daerah pesisir pantai atau di daerah yang  miliki yang menghasilkan banyak angin. Dalam membangun pembangkit listrik tenaga angin dibutuhkan banyak perhitungan yang matang supaya didapatkan desain  yang sesederhana mungkin dengan biaya yang seminim mungkin akan tetapi dapat menghasilkan daya yang maksimal, sehingga dapat mengurangi pemborosan energi dan dapat memanfaatkan tenaga angin yang tersedia pada alam sekitarnya semaksimal mungkin dan dapat dimanfaatkan oleh masyarakat sekitar. Pembuatan simulasi turbin angin dapat dilakukan dengan menggunakan simulasi simulink pada matlab. Hasil dari simulasi dan analisa data adalah terdapat perbedaan  pengaruh antara variasi pitch angle dan kecepatan turbin terhadap daya keluaran dan nilai tegangan , karena nilai  p-value < 0,05 dan membuktikan bahwa H0 dinyatakan ditolak. Hasil dari penelitian ini menunjukkan bahwa semakin besar pitch angle maka kecepatan turbin terhadap daya keluaran dan tegangan yang dihasilkan juga akan semakin besar   Alternative energy generation is increasing as it relates to the growing number of energy market needs. There are several alternative energy plants that have begun to be built, such as wind power plants. In general, wind power plants are established in coastal areas or in areas that have produced a lot of wind. In building wind power plants needed a lot of mature calculations so that the design is as simple as possible with a minimal cost possible but can produce maximum power, so as to reduce energy waste and can utilize the wind power available in the surrounding nature as much as possible and can be utilized by the surrounding community. The manufacture of simulation of wind turbine can be done using simulink simulation in MATLAB. The result of the simulation and data analysis is the difference in influence between the variation of pitch angle and the speed of the turbine to the output power and the voltage value, due to the P-value value of < 0.05 and proving that the H0 declared rejected. The result of this study shows that the greater the pitch angle then the turbine speed to the output power and the resulting voltage will also be greater

scholarly journals A peduncle detection method of tomato for autonomous harvesting

2021 ◽  
Author(s):  
Jiacheng Rong ◽  
Guanglin Dai ◽  
Pengbo Wang
Keyword(s):  
Pose Estimation ◽  
Pitch Angle ◽  
Detection Method ◽  
Geometric Model ◽  
Average Error ◽  
Long Distance ◽  
End Effector ◽  
Key Points ◽  
Yaw Angle ◽  
Cutting Point

AbstractFor automating the harvesting of bunches of tomatoes in a greenhouse, the end-effector needs to reach the exact cutting point and adaptively adjust the pose of peduncles. In this paper, a method is proposed for peduncle cutting point localization and pose estimation. Images captured in real time at a fixed long-distance are detected using the YOLOv4-Tiny detector with a precision of 92.7% and a detection speed of 0.0091 s per frame, then the YOLACT +  + Network with mAP of 73.1 and a time speed of 0.109 s per frame is used to segment the close-up distance. The segmented peduncle mask is fitted to the curve using least squares and three key points on the curve are found. Finally, a geometric model is established to estimate the pose of the peduncle with an average error of 4.98° in yaw angle and 4.75° in pitch angle over the 30 sets of tests.

scholarly journals Dynamic Analysis and Security Characteristics of Carrier-Based Aircraft Arresting in Yaw Condition

2020 ◽  
Vol 10 (4) ◽  
pp. 1253
Author(s):  
Yiming Peng ◽  
Pengpeng Xie ◽  
Xiaohui Wei ◽  
Hong Nie
Keyword(s):  
Negative Impact ◽  
Early Stage ◽  
Dynamic Properties ◽  
Wave Model ◽  
The United States ◽  
Us Military ◽  
Load Fluctuation ◽  
Kink Wave ◽  
The Difference ◽  
Yaw Angle

In order to research the safety characteristics of carrier-based aircraft in yaw arrest, a complete dynamic model of the arresting system of a certain type of aircraft was developed to understand more about its dynamic properties. Based on the discrete kink-wave model, a simulation of centering arrest was conducted. The simulation results were compared with experimental data from the United States (US) military standards, demonstrating that the basic changing laws are almost the same. On the basis of centering arrest, a simulation of yaw arrest was carried out. The results show that in yaw state, the difference in the lengths of the arresting cables on either side of the hook is smaller in the early stage after the hook hangs on the rope, which leads to little influence on load fluctuation produced by the kink-wave. With the increase in arresting distance, the difference in the lengths of the arresting cables on either side becomes larger, resulting in a situation in which the cable tension on the departure side will gradually become greater than that on the opposite side. In this situation, yaw landing has a negative impact on the characteristics of arresting safety, and the excessive yaw angle causes the aircraft to rush out of the safe landing area.

scholarly journals Cone Algorithm of Spinning Vehicles under Dynamic Coning Environment

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Shuang-biao Zhang ◽  
Xing-cheng Li ◽  
Zhong Su
Keyword(s):  
Pitch Angle ◽  
Euler Angle ◽  
Roll Angle ◽  
Angle Error ◽  
Attitude Error ◽  
Spinning Process ◽  
Cone Algorithm ◽  
Definition Of ◽  
Yaw Angle ◽  
The Relationship

Due to the fact that attitude error of vehicles has an intense trend of divergence when vehicles undergo worsening coning environment, in this paper, the model of dynamic coning environment is derived firstly. Then, through investigation of the effect on Euler attitude algorithm for the equivalency of traditional attitude algorithm, it is found that attitude error is actually the roll angle error including drifting error and oscillating error, which is induced directly by dynamic coning environment and further affects the pitch angle and yaw angle through transferring. Based on definition of the cone frame and cone attitude, a cone algorithm is proposed by rotation relationship to calculate cone attitude, and the relationship between cone attitude and Euler attitude of spinning vehicle is established. Through numerical simulations with different conditions of dynamic coning environment, it is shown that the induced error of Euler attitude fluctuates by the variation of precession and nutation, especially by that of nutation, and the oscillating frequency of roll angle error is twice that of pitch angle error and yaw angle error. In addition, the rotation angle is more competent to describe the spinning process of vehicles under coning environment than Euler angle gamma, and the real pitch angle and yaw angle are calculated finally.

Processing gravity gradient data

Geophysics ◽  
2011 ◽  
Vol 76 (2) ◽  
pp. I33-I47 ◽  
Author(s):  
Gary Barnes ◽  
John Lumley
Keyword(s):  
Measurement Data ◽  
Gravity Gradient ◽  
Common Source ◽  
Common Component ◽  
Equivalent Source ◽  
Commercial Practice ◽  
Useful Signal ◽  
Geologic Model ◽  
The Difference ◽  
Using Data

As the demand for high-resolution gravity gradient data increases and surveys are undertaken over larger areas, new challenges for data processing have emerged. In the case of full-tensor gradiometry, the processor is faced with multiple derivative measurements of the gravity field with useful signal content down to a few hundred meters’ wavelength. Ideally, all measurement data should be processed together in a joint scheme to exploit the fact that all components derive from a common source. We have investigated two methods used in commercial practice to process airborne full-tensor gravity gradient data; the methods result in enhanced, noise-reduced estimates of the tensor. The first is based around Fourier operators that perform integration and differentiation in the spatial frequency domain. By transforming the tensor measurements to a common component, the data can be combined in a way that reduces noise. The second method is based on the equivalent-source technique, where all measurements are inverted into a single density distribution. This technique incorporates a model that accommodates low-order drift in the measurements, thereby making the inversion less susceptible to correlated time-domain noise. A leveling stage is therefore not required in processing. In our work, using data generated from a geologic model along with noise and survey patterns taken from a real survey, we have analyzed the difference between the processed data and the known signal to show that, when considering the Gzz component, the modified equivalent-source processing method can reduce the noise level by a factor of 2.4. The technique has proven useful for processing data from airborne gradiometer surveys over mountainous terrain where the flight lines tend to be flown at vastly differing heights.

Computation of Hoisting Forces on Wind Turbine Blades Using Computation Fluid Dynamics

2013 ◽  
Vol 446-447 ◽  
pp. 452-457 ◽  
Author(s):  
Yong Wang ◽  
De Tian ◽  
Wei He
Keyword(s):  
Fluid Dynamics ◽  
Wind Turbine ◽  
Pitch Angle ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Azimuth Angle ◽  
Wind Turbine Blades ◽  
Mesh Model ◽  
Cfd Method ◽  
Yaw Angle

The hoisting forces on a 38.5m wind turbine blade in multiple positions are computed using the computational fluid dynamics (CFD) method. The computation model is constructed with the steady wind conditions, blade mesh model and the blade positions which are determined by the blade pitch angle, azimuth angle and rotor yaw angle. The maximal and minimal hoisting forces in three-dimensional coordinates are found and the corresponding pitch angle, azimuth angle and yaw angle are obtained. The change of the hoisting forces on wind turbine blades is analyzed. Suggestions are given to decrease the hoisting forces of the blade in open wind environment.

Penetration Efficiency as a Function of Target Obliquity and Projectile Pitch

2013 ◽  
Vol 80 (3) ◽  
Author(s):  
Charles E., Jr. Anderson ◽  
Thilo Behner ◽  
Volker Hohler
Keyword(s):  
Pitch Angle ◽  
Asymmetric Behavior ◽  
Empirical Relations ◽  
Penetration Data ◽  
D 20 ◽  
Yaw Angle ◽  
Good Agreement ◽  
Blunt Nose

The influence of pitch (vertical yaw) angle on the penetration reduction of rod projectiles into oblique targets has been investigated for tungsten sinter alloy rods with a blunt nose and L/D = 20. Semi-infinite RHA targets with an obliquity of 30 deg, 45 deg, and 60 deg were impacted at 1650 m/s. The pitch angles were varied between ±90 deg. The strong asymmetric behavior of the target crater is dependent on whether the pitch is positive or negative relative to the obliquity of the target. The experiments provide a good overview of the penetration characteristics of long rods for the whole pitch angle range. The penetration data are described by empirical relations that show good agreement with the experiments.

Envelope oriented singularity robust steering law of control moment gyros for spacecraft attitude maneuver

2018 ◽  
Vol 41 (4) ◽  
pp. 954-962 ◽  
Author(s):  
Yanning Guo ◽  
Pengyu Wang ◽  
Guangfu Ma ◽  
Liangyue Wang
Keyword(s):  
Angular Momentum ◽  
Open Loop ◽  
Spacecraft Attitude ◽  
Momentum Exchange ◽  
Control Moment ◽  
Attitude Error ◽  
Attitude Maneuver ◽  
Steering Law ◽  
The Difference ◽  
Control Moment Gyro

The problem of steering pyramid control moment gyro (CMG) cluster for fast spacecraft attitude maneuver along eigenaxis is investigated. A novel steering law is proposed to continuously attempt to reduce the difference between the current gimbal angle and the desired one corresponding to the angular momentum envelop of the CMG cluster. The proposed steering law can be decomposed into two parts: the first one is a singularity robust term to keep maneuverability and produce control torque, and the other is a null motion term to rearrange the gimbal angles toward momentum envelope. By involving this steering law, it is expected to possess both rapid angular momentum exchange and singularity avoidance ability. In addition, by introducing a new limit vector on attitude error, classical cascade-saturation control algorithm is revised to guarantee spacecraft eigenaxis rotation. Both open-loop steering law test and closed-loop attitude maneuver simulations are performed to evaluate the efficacy of the proposed methods.

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