scholarly journals Center-point steering analysis of tracked omni-vehicles based on skid conditions

2021 ◽  
Vol 12 (1) ◽  
pp. 511-527
Author(s):  
Yuan Fang ◽  
Yunan Zhang ◽  
Yinghui Shang ◽  
Tao Huang ◽  
Mengfei Yan
Keyword(s):  
Angular Velocity ◽  
Numerical Solution ◽  
Structural Parameters ◽  
Correction Model ◽  
Velocity Reduction ◽  
Center Point ◽  
Reduction Coefficient ◽  
Virtual Prototypes ◽  
Lateral Offset ◽  
Typical Layout

Abstract. Existing center-point steering models of a tracked omni-vehicle seldom consider the skid of the track (roller) grounding section, which is inconsistent with the actual steering process. In this study, for the three typical layout types, rectangular, hybrid, and centripetal, the steady center-point steering motion of a tracked omni-vehicle under skid conditions is analyzed and a correction model is investigated. The numerical solution of the absolute lateral offset of the steering pole is obtained, and the influences of various structural parameters on the numerical solution are discussed. The steering angular velocity reduction coefficient is calculated, and the angular velocity of vehicles is corrected. The simulation of center-point steering motion is carried out on eight virtual prototypes, and the center-point steering motion experiment is carried out on three physical prototypes. The results show that the established correction model is more in line with the steering reality of the tracked omni-vehicle, and it can play a role in correcting the center-point steering angular velocity.

Study on the Newly Developed 3-Dimensional Base Isolation System Using a Velocity Reduction Mechanism

2004 ◽  
Author(s):  
Tomohiro Ito ◽  
Katsuhisa Fujita ◽  
Takeshi Ohkubo
Keyword(s):  
Natural Frequency ◽  
High Performance ◽  
Base Isolation ◽  
Structural Parameters ◽  
Active Components ◽  
Isolation System ◽  
Velocity Reduction ◽  
Base Isolation System ◽  
Rocking Motion ◽  
Isolation Systems

Due to the Hyogo-ken Nambu Earthquake in 1995 and the huge earthquakes which are considered to occur in near future, the raise in the seismic design criteria in the horizontal and vertical excitations has been investigated. According to these trends, many base isolation structures have been developed and constructed. However, the most of these structures are limited to the horizontal base isolation. Therefore, the development of the effective 3-dimentional base isolation system becomes more and more important. The conventional 3-dimentional base isolation systems proposed up to now are insufficient in reducing the vertical natural frequency, otherwise are very complex due to facilitation of the active components. In this study, the dynamic characteristics of a high performance 3-dimentional base isolation system newly developed by the authors are reported. This system employs a velocity reduction system using a gear mechanics which can reduce the vertical natural frequency less than 1Hz while that of the conventional system is around 3Hz. And also this employs friction dampers to suppress the large displacement. Further, this system is facilitated with a rocking-suppression system which can effectively suppress the rocking motion inevitable for 3-dimentional base isolation. The response acceleration, displacement and rocking motion are evaluated by numerical simulations in varying the friction force, the predominant frequency of seismic input waves, the eccentricity of the upper structural mass, etc.. As the results, it is shown that the base isolation system developed here has very effective base isolation characteristics and the rocking suppression effects. And the optimization of the structural parameters is also discussed.

scholarly journals Pressure Effect of the Vibrational and Thermodynamic Properties of Chalcopyrite-Type Compound AgGaS2: A First-Principles Investigation

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2370 ◽  
Author(s):  
Jianhui Yang ◽  
Qiang Fan ◽  
You Yu ◽  
Weibin Zhang
Keyword(s):  
Thermal Conductivity ◽  
Thermodynamic Properties ◽  
First Principles ◽  
Structural Parameters ◽  
Structural Phase ◽  
First Principles Calculation ◽  
Optical Phonons ◽  
Phonon Modes ◽  
Type Compound ◽  
Center Point

To explore the structural, vibrational, and thermodynamic properties of the chalcopyrite-type compound AgGaS2 under pressure, we applied hydrostatic pressure to the relaxed compound based on the first principles calculation and quasi-harmonic approximation. The structural parameters, including lattice constants and bond lengths decrease monotonically with the increasing pressure. The phonon dispersion curves under various pressures reveal the structural phase transition of chalcopyrite-type compound AgGaS2 at about 4 GPa. The intrinsic mechanism of thermal conductivity for the chalcopyrite-type compound AgGaS2 has been shown with phonon anharmonicity. The frequencies of the optical phonons at the center point Γ of the first Brillouin zone were calculated with the longitudinal optical–transverse optical (LO–TO) splitting mode. The dependence of the frequencies of the optical phonons on the pressure provides the information for the Raman spectroscopic study under high pressure. The pressure dependence of the Grüneisen parameters indicates that the instability of chalcopyrite-type compound AgGaS2 is associated with the softening of the acoustic phonon modes at around the center point Γ. The thermal conductivity for chalcopyrite-type compound AgGaS2 could be reduced by applying external pressure. The various thermodynamic properties, such as the Helmholtz free energy, entropy, and heat capacity, at different temperatures and pressures were discussed and analyzed based on the phonon properties.

scholarly journals Research on the Optimization the Structural Parameters of Mechanical Treadmill

2015 ◽  
Vol 9 (1) ◽  
pp. 938-943
Author(s):  
Linzhen Wu
Keyword(s):  
Angular Velocity ◽  
Optimization Model ◽  
Kinematic Analysis ◽  
Optimization Design ◽  
Structural Parameters ◽  
Angular Displacement ◽  
Angular Acceleration ◽  
Simulation Software ◽  
Mechanical Transmission ◽  
Amplitude Variation

This paper proposed a three-dimensional model of treadmill, structural diagram of mechanical transmission, structural optimization model and kinematic analysis model, deriving the values of connecting rods as 0.425 m, 1.673 m and 0.662 m by solving the optimization model. It further conducts a kinematic analysis on treadmill using this set of parameters and kinematic simulation software “Motion”, providing simulation curves of angular displacement, angular velocity and angular acceleration of the main moving parts such as the connecting rods, pedals and handrail handles. The simulation curves indicate that when the rotation speed of the wheels is 10 r/min, the connecting rods, pedals and handrail handles move smoothly and change almost sinusoidally; the displacement of handles ranges in-700∼200 mm, the speed ranges in-400∼400 mm/s, the acceleration ranges in -400∼500 mm/s2, the angular change of pedals is -5°∼30°, the amplitude variation of angular velocity is <25°/s and the amplitude variation of angular acceleration is <28°/s2. The above mentioned calculated prospects of the treadmill provide some reference for carrying out a quick optimization design of the treadmill.

Study on Simulation and Performance of Open-Type Screw Discharging Structure

2013 ◽  
Vol 387 ◽  
pp. 337-340
Author(s):  
You Xiang Li ◽  
Shu Guang Gong ◽  
Hai Shan Lu
Keyword(s):  
Angular Velocity ◽  
Discrete Element Method ◽  
Structural Parameters ◽  
Great Influence ◽  
Reference Value ◽  
Screw Conveyor ◽  
Discharge Performance ◽  
Open Type ◽  
Operation Parameters ◽  
And Performance

Compared with the closed screw conveyor, the discharging performance of open-type screw structure has a certain degree of uncertainty. The design of open-type screw structure is firstly presented in this paper. A novel open-type screw discharging structure is developed on the base of the requirement of industry, and structural parameters and operation parameters of screw are given. Based on the discrete element method, the simulation model of spiral discharging performance is built. The influence of the angular velocity of on open-type screw discharging performance is discussed. The analysis results show that the angular velocity of screw has a great influence on the discharge performance in the condition that other parameters remain unchanged. The presented method has an important guiding role and theoretical reference value to design of open-type screw discharging structure.

scholarly journals Checking the correct operation of main measuring instruments on the flight model and prototype of AIST small spacecraft

2018 ◽  
Vol 234 ◽  
pp. 01007 ◽  
Author(s):  
Andry Sedelnikov ◽  
Ekaterina Khnyryova ◽  
Tatiana Ivashova
Keyword(s):  
Angular Velocity ◽  
Measuring Equipment ◽  
Orbital Motion ◽  
Measuring Instruments ◽  
Control Laws ◽  
Correct Operation ◽  
Small Spacecraft ◽  
Velocity Reduction ◽  
First Case ◽  
Flight Model

Flight model and prototype of AIST small spacecraft were launched in 2013 and 2014 respectively. They were used for carrying out various scientific researches, as well as testing the operation of AIST series small spacecrafts. They were operated in an uncontrolled flight and did not have a fullyfeatured orbital motion control system. However, it has been possible to reduce the angular velocity by magnetorquers. To obtain the control laws, the angular velocity of small spacecraft was estimated by means of magnetometer sensors. On the flight model of AIST small spacecraft, the angular velocity reduction mode was used twice. In the first case, the angular velocity was reduced, in the second case, it did not change significantly. On the prototype of AIST small spacecraft, the angular velocity reduction mode was used three times. In all three cases, a significant increase in the angular velocity of small spacecraft rotation was observed. The paper describes a test for checking the magnetometer sensors correct operation. Based on this test, conclusions about the measuring equipment correct operation are made. Ineffective control of the angular velocity of small spacecraft rotation is most likely due to failure to take account of impact of scientific and supporting equipment on the measuring instruments.

scholarly journals SCREW DESCENT, ANALYTICAL DESCRIPTION OF WHICH INCLUDES THE EQUATION OF PARTICLE MOVEMENT ON AN INCLINED PLANE

2021 ◽  
pp. 89-98
Author(s):  
Tatiana Volina
Keyword(s):  
Angular Velocity ◽  
Structural Parameters ◽  
Analytical Description ◽  
Constant Angular Velocity ◽  
Particle Movement ◽  
Inclined Plane ◽  
Material Particle ◽  
Angle Of Friction ◽  
The Coefficient Of Friction ◽  
The Difference

To study the modes of particle movement depending on the constructive parameters of the surface, it is important to have analytical dependencies of this movement. An analytical description of the movement of a load on the example of a material particle on the surface of a gravitational descent formed by a screw conoid and a coaxial vertical limiting cylinder was developed in the article. It makes it possible to find the constructive parameters of the descent, which will provide the required speed of the transportation. If the surface of the confining cylinder is absolutely smooth, then the movement of the particle along such a descent will be uniformly accelerated or equally slowed down depending on the value of the angle of inclination of the plane, that is, similar to movement along an inclined plane. If the angle of inclination of the plane is equal to the angle of friction, then the particle will move with a constant angular velocity of rotation, then one can find the linear velocity, which will also be constant. The value of this speed will be equal to the initial one. If the angle of inclination of the plane is equal to the angle of friction, but the coefficient of friction is not equal to zero, then the particle will be decelerated due to the action of the friction force of the particle on the surface of the cylinder. This is the difference from descent along an inclined plane, along which the particle in this case will move at a constant speed. In the general case, when the angle of ascent of the helix is ​​greater than the angle of friction, the driving force and the force of friction on the surface of the conoid and on the surface of the cylinder are balanced with each other and the angular velocity of rotation of the particle becomes constant. Consequently, it is possible to provide the required speed of transportation of the material at various ratios of the structural parameters of the surface with known coefficients of friction. To reduce the overall dimensions of the screw descent, it is necessary to reduce the radius of the limiting cylinder; however, with this limitation, the weight of loads should be taken into account.

Zonal and tesseral harmonic perturbations of an artificial satellite

1966 ◽  
Vol 25 ◽  
pp. 323-325 ◽  
Author(s):  
B. Garfinkel
Keyword(s):  
Angular Velocity ◽  
Spherical Harmonics ◽  
Artificial Satellite ◽  
Compact Form ◽  
Earth’S Rotation ◽  
Earth's Rotation ◽  
Secular Variations ◽  
Tesseral Harmonics

The paper extends the known solution of the Main Problem to include the effects of the higher spherical harmonics of the geopotential. The von Zeipel method is used to calculate the secular variations of orderJmand the long-periodic variations of ordersJm/J2andnJm,λ/ω. HereJmandJm,λare the coefficients of the zonal and the tesseral harmonics respectively, withJm,0=Jm, andωis the angular velocity of the Earth's rotation. With the aid of the theory of spherical harmonics the results are expressed in a most compact form.

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