Research on Position Keeping and Path Following Strategy for the Under-Actuated Waved Glider

2020 ◽  
Author(s):  
Peng Wang ◽  
Xinliang Tian ◽  
Xiantao Zhang ◽  
Daoyong Wang ◽  
Xiaoxian Guo
Keyword(s):  
Mathematical Model ◽  
Surface Waves ◽  
Path Following ◽  
Degree Of Freedom ◽  
Environmental Disturbances ◽  
Autonomous Surface Vehicle ◽  
Wave Glider

Abstract Wave glider is a novel autonomous surface vehicle that uses energy from surface waves for propulsion. However, because it is inherently under-actuated, multi-variable and strong coupled, it is challenging to control the wave glider accurately under the environmental disturbances. In this study, a novel robust position keeping guidance strategy and an advanced path following approach for the under-actuated wave glider based on restricted circle are firstly developed. Furthermore, an 8-DOFs (Degree-of-Freedom) mathematical model for the under-actuated wave glider is adopted, and the position keeping and path following tasks of the wave glider are conducted in simulation. The results demonstrate that the under-actuated wave glider is able to accomplish the position keeping and path following tasks with the proposed strategies.

Relationship between the Steady-Handling Characteristics of Automobiles and Their Stability

1973 ◽  
Vol 15 (5) ◽  
pp. 326-328 ◽  
Author(s):  
R. S. Sharp
Keyword(s):  
Mathematical Model ◽  
Steady State ◽  
Degree Of Freedom ◽  
Nonlinear Region ◽  
Handling Characteristics ◽  
Yield Information ◽  
Turning Motion ◽  
The Stability ◽  
Three Degree Of Freedom

Analyses of the steady-state handling behaviour of an automobile and the stability of its steady-turning motion, based on a three degree of freedom mathematical model, are used to show that the steady behaviour and the stability are related similarly in the nonlinear region as in the well documented linear one. It is concluded that analysis and measurement of the steady behaviour will yield information on the stability of automobiles.

Optimal Design of a Six-Bar Linkage for an Anthropomorphic Three-Jointed Finger Mechanism

1992 ◽  
Author(s):  
Jichuan Zhang ◽  
Gongliang Guo ◽  
William A. Gruver
Keyword(s):  
Mathematical Model ◽  
Nonlinear Programming ◽  
Optimal Design ◽  
Transmission Efficiency ◽  
Degree Of Freedom ◽  
Optimal Parameters ◽  
Joint Friction ◽  
Robotic Devices ◽  
End Effectors ◽  
Human Finger

Abstract We treat the design of a three-jointed, anthropomorphic, finger mechanism for prostheses and robotic end-effectors. Based on the study of configurations for the human finger, we propose a six-bar linkage with one degree of freedom for the finger mechanism. A model of the fingertip displacement of the mechanism is derived by a vector analysis approach. We study the effects of joint friction on the transmission efficiency. By measuring the joint positions of a human finger, we develop a mathematical model of the pinching and holding configurations for the human finger. Optimal parameters for the finger mechanism are obtained by nonlinear programming based on motion posture, locus, transmission efficiency, and weight subject to geometric and bionic constraints. Simulations indicate that the mechanism is useful in a variety of prosthetic and robotic devices.

scholarly journals Wave Glider Observations of Surface Waves During Three Tropical Cyclones in the South China Sea

Water ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1331 ◽  
Author(s):  
Di Tian ◽  
Han Zhang ◽  
Wenyan Zhang ◽  
Feng Zhou ◽  
Xiujun Sun ◽  
...  
Keyword(s):  
Surface Wave ◽  
South China Sea ◽  
Surface Waves ◽  
Tropical Cyclones ◽  
South China ◽  
Tangential Direction ◽  
China Sea ◽  
Wave Forecast ◽  
Wave Glider ◽  
The Right

Surface waves induced by tropical cyclones (TCs) play an important role in the air–sea interaction, yet are seldom observed. In the 2017 summer, a wave glider in the northern South China Sea successfully acquired the surface wave parameters when three TCs (Hato, Pakhar, and Mawar) passed though successively. During the three TCs, surface wave period increased from 4–6 s to ~8–10 s and surface wave height increased from 0–1 m to 3–8 m. The number of wave crests observed in a time interval of 1024 s decreased from 100–150 to 60–75. The sea surface roughness, a key factor in determining the momentum transfer between air and sea, increased rapidly during Hato, Pakhar, and Mawar. Surface waves rotated clockwise (anti-clockwise) on the right (left) side of the TC track, and generally propagated to the right side of the local cyclonic tangential direction relative to the TC center. The azimuthal dependence of the wave propagation direction is close to sinusoidal in a region within 50–600 km. The intersection angle between surface wave direction and the local cyclonic tangential direction is generally smallest in the right-rear quadrant of the TC and tends to be largest in the left-rear quadrant. This new set of glider wave observational data proves to be useful for assessing wave forecast products and for improvements in corresponding parameterization schemes.

The Effect of Gravity and Rotor Configuration on Dry Friction Whip and Safe Rotor/Stator Clearance

2019 ◽  
Author(s):  
Rajiv Kumar Vashisht
Keyword(s):  
Mathematical Model ◽  
Fault Diagnosis ◽  
Dry Friction ◽  
Rotating Machinery ◽  
Degree Of Freedom ◽  
System Response ◽  
Rich Variety ◽  
Wide Range ◽  
Clearance Level ◽  
High Degree

Abstract A mathematical model is developed for a real rotor/stator system with high degrees-of-freedoms, multiple disks, flexible bearing supports and couplings. The safe clearance level for coasting up of the rotor is calculated for a general high degree-of-freedom rotor/stator system. The harmful phenomena of dry friction whip, which is generally observable for simple 2 degree-of-freedom Jeffcott rotors in the absence of gravity only, can be proved to exist (in real rotor/stator systems) even in the presence of gravity for a wide range of clearance levels. In case of Jeffcott rotors, by fixing the clearance and increasing the rotor spin frequency, the response of the system follows the pattern: No rub - Forward Annular Rub (FAR) - Partial Forward Whirl (PFW) - Partial Backward Whirl (PBW) - dry whip (WHIP). In case of a real rotor/stator system, at certain frequencies, the system directly jumps to dry whip. The simulated results show a rich variety of system dynamics including FAR, PFW and WHIP in case of vertical rotors where the effect of gravity is neglected. For horizontal rotors, under the effect of gravity, the system response contains multi-harmonics, chaotic responses and multi-period vibrations. Based on these responses, a robust fault diagnosis strategy can be designed to identify the rubbing action in rotating machinery.

Mathematical Model of Worm-like Motion Systems with Finite and Infinite Degree of Freedom

Romansy 14 ◽  
2002 ◽  
pp. 507-515 ◽  
Author(s):  
Klaus Zimmermann ◽  
Igor Zeidis ◽  
Joachim Steigenberger
Keyword(s):  
Mathematical Model ◽  
Degree Of Freedom ◽  
Infinite Degree

Measurements of Directional Wave Spectra and Wind Stress from a Wave Glider Autonomous Surface Vehicle

2018 ◽  
Vol 35 (2) ◽  
pp. 347-363 ◽  
Author(s):  
Jim Thomson ◽  
James B. Girton ◽  
Rajesh Jha ◽  
Andrew Trapani
Keyword(s):  
Wind Stress ◽  
Reference Data ◽  
Full Range ◽  
Bulk Wave ◽  
Frequency Spectra ◽  
Low Frequencies ◽  
Wind Speeds ◽  
Autonomous Surface Vehicle ◽  
Ultrasonic Anemometer ◽  
Wave Glider

AbstractMethods for measuring waves and winds from a Wave Glider autonomous surface vehicle (ASV) are described and evaluated. The wave method utilizes the frequency spectra of orbital velocities measured by GPS, and the wind stress method utilizes the frequency spectra of turbulent wind fluctuations measured by an ultrasonic anemometer. Both methods evaluate contaminations from vehicle motion. The methods were evaluated with 68 days of data over a full range of open ocean conditions, in which wave heights varied from 1 to 8 m and wind speeds varied from 1 to 17 m s−1. Reference data were collected using additional sensors on board the vehicle. For the waves method, several additional datasets are included that use independently moored Datawell Waverider buoys as reference data. Bulk wave parameters are determined within 5% error with biases of less than 5%. Wind stress is determined within 4% error with 1% bias. Wave directional spectra also compare well, although the Wave Glider results have more spread at low frequencies.

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