Principle Of Conservation Of Angular Momentum Research Articles

Corrigendum to “Robust stabilization control of live working robot under wind load based on angular momentum conservation principle”

Corrigendum to “Robust stabilization control of live working robot under wind load based on angular momentum conservation principle”

Robust stabilization control of live working robot under wind load based on angular momentum conservation principle

In respond to the problem that the live working robot is easy to be affected by wind load in the process of field high altitude operation, which result in robot body rolling with poor stability and low operation efficiency, a robot momentum wheel balance control method under wind load action based on the principle of angular momentum conservation has been proposed in this paper. The moment generated by the rotation of the momentum wheel is used to offset the wind load moment so as to realize the robot online balance control. Through the analysis of the influence mechanism for the live working robot on the wind load, the coupling relationship model of three kinds typical parameters namely, wind force, robot rolling angle, and momentum wheel drive moment have been established. Based on the virtual prototype size of the live working robot, the physical model of the momentum wheel device is established and the dynamic model of robot balance system under the wind load is established by Lagrange method. Finally, the disturbance environment of the robot under the wind load action in ADAMS and MATLAB-SIMULINK software, a fuzzy PID controller has been adopt to control the robot online in real time wind load. Compared with computational torque control and gravity compensation control, the simulation result show that the momentum wheel balance can reduce the rolling angle under the wind load and keep the robot in a balance posture with strong robustness. The research of this paper has important theoretical significance and practical application value for promoting the practical application of robot in actual wind load operation environment.

Point stabilization of nonholonomic spherical mobile robot using nonlinear model predictive control

Control of nonholonomic spherical mobile robot is a generalization of the classical ball-plate problem which is still challenging in robotic researches. In this paper, point stabilization of a nonholonomic spherical mobile robot actuated by two internal rotors is investigated. Since every kinematic trajectory is not always dynamically realizable for the spherical robot driven by two actuators, the mathematical model of the robot is derived based on the angular momentum conservation principle. The controllability of the robot is evaluated based on the obtained model and the uncontrollable configurations as well as their geometrical meaning are specified. To simultaneous control of position and orientation of the robot, a nonlinear model predictive control (NMPC) is developed for the first time and the stability analysis is performed through using Lyapunov stability theorem. The performance of the designed control system is assessed through computer simulations in different test conditions. The simulation results show the significant performance of the proposed NMPC in stabilization of the spherical shell from every initial configuration to every desired position and orientation even in the uncontrollable region. Considering additive bounded noises, the robust stabilization of the nonholonomic spherical robot by the NMPC is also assessed in simulations. A spherical mobile robot driven by two perpendicular rotors is investigated.The equations of motion are derived using angular momentum conservation principle.The controllability of the model is analyzed and its uncontrollable configurations are specified.A NMPC is designed to control the position and orientation of the spherical shell simultaneously.The stability of designed controller is proven and its performance is evaluated.

Stability of equilibria points for a dumbbell satellite when the central body is oblate spheroid

The main aim of the present work is to study the positions of the equilibria points and their stability in the frame work of satellite approximation. The significant implication is that the motion around these points is unstable in the linear sense. The principle of angular momentum conservation is used as a tool to reduce the degree of freedom of the dynamical systems of equations. The positions of the relative equilibria are explicitly found as well as necessary and sufficient conditions for stable motion in the linear sense are stated.

Dynamic modeling and trajectory planning for a mobile spherical robot with a 3Dof inner mechanism

A spherical robot consists of a spherical shell and an inner mechanism. In this paper, a new inner mechanism with three independent actuators is presented. The robot motion is based on angular momentum conservation principle and the system is nonholonomic. The kinematic and dynamic equations of the whole system are derived by using Euler parameters and Kane's method. The singularity does not occur in the equations of inverse dynamic because of using Euler parameters instead of Euler angles. By adding one degree of freedom to the inner mechanism, the trajectory planning of the mobile spherical robot is possible for every desired trajectory. The trajectory planning is done for linear and circular arc trajectories. The robot starts its motion from first point with zero velocity to the end point on the desired trajectory and stops at the end point. The computer simulation of robot motion is done. The comparison of the numerical solution with computer simulation shows good agreement.

Bivelocity hydrodynamics. Diffuse mass flux vs. diffuse volume flux

An intimate physical connection exists between a fluid’s mass and its volume, with the density ρ serving as a proportionality factor relating these two extensive thermodynamic properties when the fluid is homogeneous. This linkage has led to the erroneous belief among many researchers that a fluid’s diffusive (dissipative) mass flux and its diffusive volume flux counterpart, both occurring in inhomogeneous fluids undergoing transport are, in fact, synonymous. However, the existence of a truly dissipative mass flux (that is, a mass flux that is physically dissipative) has recently and convincingly been shown to be a physical impossibility [H.C. Öttinger, H. Struchtrup, M. Liu, On the impossibility of a dissipative contribution to the mass flux in hydrodynamics, Phys. Rev. E 80 (2009) 056303], owing, among other things, to its violation of the principle of angular momentum conservation. Unfortunately, as a consequence of the erroneous belief in the equality of the diffuse volume and mass fluxes (sans an algebraic sign), this has led many researchers to wrongly conclude that a diffuse volume flux is equally impossible. As a consequence, owing to the fundamental role played by the diffuse volume flux in the theory of bivelocity hydrodynamics [H. Brenner, Beyond Navier–Stokes, Int. J. Eng. Sci. 54 (2012) 67–98], many researchers have been led to falsely dismiss, without due consideration, the possibility of bivelocity hydrodynamics constituting a potentially viable physical theory, which it is believed to be. The present paper corrects this misconception by using a simple concrete example involving an isothermal rotating rigid-body fluid motion to clearly confirm that whereas a diffuse mass flux is indeed impossible, this fact does not exclude the possible existence of a diffuse volume flux and, concomitantly, the possibility that bivelocity hydrodynamics is indeed a potentially viable branch of fluid mechanics.

Pointing control of spacecraft using two SGCMGs via LPV control theory

In this paper, we consider a pointing control of a spacecraft using two single-gimbal control moment gyros (SGCMGs). Our pointing control problem is to make the line-of-sight of a camera or an antenna that is fixed on a body axis aim along a desired direction. To solve this problem, we first state the control objective for the pointing control through the angular momentum conservation principle. Then, we develop a gain-scheduled (GS) controller via linear parameter-varying (LPV) control theory. Finally, the feasibility of the proposed control method is shown by a numerical simulation.

Optimized Configuration for the Upper Body with a Bisecting Hip Mechanism in Passive Dynamic Walking

Biped passive dynamic walking is a promising idea towards the goal of humanoid robotics further after the proposal of the upper body in these years. In this paper, we deduce the dynamic robot model with the upper body based on bisecting hip, in which the section of the swing phase is performed by Lagrange method, while the section of the collision phase is completed in terms of the principle of angular momentum conservation. The analysis of the global stability and the local stability are combined with each other, based on which the configurations of parameters with different mass and size of the upper body are discussed. Finally the optimized configuration of the model is obtained after the simulation in Adams environment. Results verify that the model with an upper body exhibits an extraordinary stability and robustness under circumstances of either a single disturbance or random disturbances.

The first mathematical models of dynamic meteorology: The Berlin prize contest of 1746

Carbon dioxide is one greenhouse gas, which is responsible for the anthropogenic induced climate change. Above all, urban agglomerations like the German Ruhrgebiet are a potential CO 2 -source due to the usage of fossil energy sources. For example, in the city of Essen, Germany (North Rhine-Westphalia; 51°28'N. 7°0'E; 580,000 inhabitants; area = 210 km 2 ) the urban carbon dioxide was determined by taking 50 survey tests with the aid of the mobile laboratory from the Dept. of Applied Climatology, University of Duisburg-Essen, Campus Essen, Germany. These measurements were taken along a route of 63 kilometers. The purpose of this study was to analyze the relationship between urban CO 2 concentration levels and temporal variables (e.g., air temperature, atmospheric stability) and invariable influencing factors (e.g., surface configuration) within the urban canopy layer. The results are based on a one-year period of data collection (December 2002-November 2003) with additional data collection in 2004 and 2005. This study proves how the urban CO 2 concentration is influenced by spatial variations as well as diurnal and seasonal meteorological conditions. Thus, approximately more than 70 % of the near surface urban CO 2 is mostly affected by traffic density and atmospheric stability. In addition, it is proven that CO and NO can help to verify the dependence on CO 2 of the traffic density. Thus, the appearance of CO 2 shows a close interdependence between CO (R 2 day time = 0.57) and NO (R 2 day time = 0.69). Other factors that were identified and analyzed include air temperature (9 %), relative humidity (6 %), the urban vegetation (5 %), or the surface configuration (4 %). However, these factors contributed only slightly in terms of explaining the impact of diurnal or seasonal urban CO 2 pattern. Hence, it is clear that there should be mobile survey tests for at least one year while considering the urban types of land use. Otherwise, it is not possible to represent the seasonal and spatial variations of the near surface urban CO 2 .

Spacecraft Line-of-Sight Control Using a Single Variable-Speed Control Moment Gyro

Complete attitude control of a spacecraft is not possible with only one single-gimbal variable-speed control moment gyro due to the conservation of angular momentum. However, partial attitude control without violating the angular momentum conservation principle is still possible. In this paper feedback controllers using only one single-gimbal variable-speed control moment gyro are presented that drive all three components of the angular velocity of a rigid spacecraft to zero, while at the same time a spacecraft body-axis points along an arbitrary inertial direction. To solve this problem, we first introduce a pair of angles to parametrize all feasible final spacecraft orientations at rest without violating the angular momentum constraint Based on this parametrization, an LQR control law is designed to locally achieve the control objective. Afterwards, a multistage control law is proposed to achieve the same control objective for large initial conditions.

Simple numerical method of computing the probabilities of angular momentum J ν occurring among possible vectors J Resulting from n angular momentum j μ summation (μ=1−n)

Arelatively simple numerical method of summing angular momentum vectors with maintaining space quantization rules of each summed angular momentum has been presented. The method enables the calculation of the values of probability (pjμ) of finding a definite angular momentum Jμ among all vectors J being the results of quantum summation of n angular momentum vectors jμ(μ=1-n. It may be used, e.g., in the calculations of angular momentum of many-particle states. The significance of the paper is connected with the possibility of taking into account, in a simple way, the angular momentum conservation principle for a system which consists of an arbitrary number of excitons.

Angular momentum conservation (a freshman experiment)

A simple turntable and a simple spring gun mounted on it demonstrate the angular momentum conservation principle by providing independent measurements of the angular momenta of the turntable, and of a metal ball, projected horizontally—and tangentially—from the spring gun.

Product rotational distributions and specific opacity functions for the reaction Ba +HI → BaI (v=0,4,8,12,16,18) +H

The reaction Ba+HI→BaI(v)+H was studied under beam-gas, single-collision conditions with an average center-of-mass collision energy of 13 kJ mol−1. BaI (v) rotational distributions were recorded for v=0, 4, 8, 12, 16, and 18 by means of selectively detected laser-induced fluorescence of the BaI C 2Π–X 2Σ+ band system. Each rotational distribution exhibits a maximum toward its high energy end and the range of rotational states becomes narrower as product vibration increases. Because the kinematic constraint causes almost all reagent orbital angular momentum to appear in product rotation, the principle of angular momentum conservation provides the means for determining specific opacity functions from the rotational distributions and the reagent relative velocity distribution. The specific opacity functions are narrow functions of the impact parameter. The peak values decrease smoothly from approximately 4.5 Å for v=0 to 1.5 Å for v=18, indicating a strong correlation between impact parameter and product vibrational state such that Ba+HI collisions with small impact parameter produce BaI with large vibrational excitation.

A note on the relationship between the magnetization vector diffusion and the angular momentum conservation principle

The problem of the derivation of the diffusion term in the magnetization vector equation is analyzed on the basis of the angular momentum conservation principle in a local thermodynamic theory.