Minimum Base Attitude Disturbance Planning for a Space Robot During Target Capture

2018 ◽  
Vol 10 (5) ◽  
Author(s):  
Jingchen Hu ◽  
Tianshu Wang
Keyword(s):  
Angular Velocity ◽  
Analytical Formula ◽  
Space Robot ◽  
Velocity Change ◽  
Constant Multiple ◽  
Planar Space ◽  
Target Capture ◽  
Spatial Operator ◽  
Impact Phase ◽  
The Impact

This paper presents a method to minimize the base attitude disturbance of a space robot during target capture. First, a general dynamic model of a free-floating space robot capturing a target is established using spatial operator Algebra, and a simple analytical formula for the base angular velocity change during the impact phase is obtained. Compared with the former models proposed in the literature, this model has a simpler form, a wider range of applications, and O(n) computation complexity. Second, based on the orthogonal projection matrix lemma, we propose the generalized mass Jacobian matrix (GMJM) and find that the base angular velocity change is a constant multiple of the component which the impact impulse projects to the column space of the GMJM. Third, a new concept, the base attitude disturbance ellipsoid (BADE), is proposed to express the relationship between the base attitude disturbance and the impact direction. The impact direction satisfying the minimum base attitude disturbance can be straightforwardly obtained from the BADE. In particular, for a planar space robot, we draw the useful conclusion that the impact direction unchanged base attitude must exist. Furthermore, the average axial length of the BADE is used as a measurement to illustrate the average base attitude disturbance under impact impulses from different directions. With this measurement, the desired pre-impact configuration with minimum average base attitude disturbance can be easily determined. The validity and the efficiency of this method are verified using a three-link planar space robot and a 7DOF space robot.

Pre-Impact Configuration Designing of a Robot Manipulator for Impact Minimization

2017 ◽  
Vol 9 (3) ◽  
Author(s):  
Jingchen Hu ◽  
Tianshu Wang
Keyword(s):  
Impact Force ◽  
Robot Manipulator ◽  
Analytical Formula ◽  
Joint Space ◽  
Collision Problem ◽  
Spatial Operator ◽  
Inertia Ellipsoid ◽  
The Impact ◽  
Maximum Minimum ◽  
Simple Analytical Formula

This paper studies the collision problem of a robot manipulator and presents a method to minimize the impact force by pre-impact configuration designing. First, a general dynamic model of a robot manipulator capturing a target is established by spatial operator algebra (SOA) and a simple analytical formula of the impact force is obtained. Compared with former models proposed in literatures, this model has simpler form, wider range of applications, O(n) computation complexity, and the system Jacobian matrix can be provided as a production of the configuration matrix and the joint matrix. Second, this work utilizes the impulse ellipsoid to analyze the influence of the pre-impact configuration and the impact direction on the impact force. To illustrate the inertia message of each body in the joint space, a new concept of inertia quasi-ellipsoid (IQE) is introduced. We find that the impulse ellipsoid is constituted of the inertia ellipsoids of the robot manipulator and the target, while each inertia ellipsoid is composed of a series of inertia quasi-ellipsoids. When all inertia quasi-ellipsoids exhibit maximum (minimum) coupling, the impulse ellipsoid should be the flattest (roundest). Finally, this paper provides the analytical expression of the impulse ellipsoid, and the eigenvalues and eigenvectors are used as measurements to illustrate the size and direction of the impulse ellipsoid. With this measurement, the desired pre-impact configuration and the impact direction with minimum impact force can be easily solved. The validity and efficiency of this method are verified by a PUMA robot and a spatial robot.

Oblique Impact Analysis of a Golf Ball

2014 ◽  
Vol 566 ◽  
pp. 443-448 ◽  
Author(s):  
Kazuo Arakawa
Keyword(s):  
Angular Velocity ◽  
High Speed ◽  
Impact Analysis ◽  
Video Camera ◽  
Oblique Impact ◽  
Golf Ball ◽  
Normal Velocity ◽  
Velocity Change ◽  
High Speed Video Camera ◽  
The Impact

The oblique impact of a golf ball with a rigid steel target was studied using a high-speed video camera. The video images during the impact were employed to measure the compressional displacement of the ball normal to the target and to determine the normal velocity and acceleration of the ball as a function of time. The rotation angle of the ball was also measured to evaluate the angular velocity during the impact. The results showed that the angular velocity increased and then decreased during the impact. To study the velocity change, we introduced an analytical model and suggested that the ball deformation can play an important role to understand the friction effect during the impact.

scholarly journals Sensitivity of Ultrasonic Coda Wave Interferometry to Material Damage—Observations from a Virtual Concrete Lab

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4033
Author(s):  
Claudia Finger ◽  
Leslie Saydak ◽  
Giao Vu ◽  
Jithender J. Timothy ◽  
Günther Meschke ◽  
...  
Keyword(s):  
Elastic Moduli ◽  
Concrete Specimen ◽  
Coda Wave ◽  
Velocity Change ◽  
Damage Scenarios ◽  
Different Types ◽  
Source Signal ◽  
The Impact ◽  
Structural Scale ◽  
Coda Wave Interferometry

Ultrasonic measurements are used in civil engineering for structural health monitoring of concrete infrastructures. The late portion of the ultrasonic wavefield, the coda, is sensitive to small changes in the elastic moduli of the material. Coda Wave Interferometry (CWI) correlates these small changes in the coda with the wavefield recorded in intact, or unperturbed, concrete specimen to reveal the amount of velocity change that occurred. CWI has the potential to detect localized damages and global velocity reductions alike. In this study, the sensitivity of CWI to different types of concrete mesostructures and their damage levels is investigated numerically. Realistic numerical concrete models of concrete specimen are generated, and damage evolution is simulated using the discrete element method. In the virtual concrete lab, the simulated ultrasonic wavefield is propagated from one transducer using a realistic source signal and recorded at a second transducer. Different damage scenarios reveal a different slope in the decorrelation of waveforms with the observed reduction in velocities in the material. Finally, the impact and possible generalizations of the findings are discussed, and recommendations are given for a potential application of CWI in concrete at structural scale.

scholarly journals Time-jerk optimal trajectory planning of hydraulic robotic excavator

2021 ◽  
Vol 13 (7) ◽  
pp. 168781402110346
Author(s):  
Yunyue Zhang ◽  
Zhiyi Sun ◽  
Qianlai Sun ◽  
Yin Wang ◽  
Xiaosong Li ◽  
...  
Keyword(s):  
Angular Velocity ◽  
Trajectory Planning ◽  
Optimal Trajectory ◽  
High Efficiency ◽  
Optimal Solution ◽  
Optimal Time ◽  
Target Point ◽  
Robotic Excavator ◽  
The Impact ◽  
Optimal Trajectory Planning

Due to the fact that intelligent algorithms such as Particle Swarm Optimization (PSO) and Differential Evolution (DE) are susceptible to local optima and the efficiency of solving an optimal solution is low when solving the optimal trajectory, this paper uses the Sequential Quadratic Programming (SQP) algorithm for the optimal trajectory planning of a hydraulic robotic excavator. To achieve high efficiency and stationarity during the operation of the hydraulic robotic excavator, the trade-off between the time and jerk is considered. Cubic splines were used to interpolate in joint space, and the optimal time-jerk trajectory was obtained using the SQP with joint angular velocity, angular acceleration, and jerk as constraints. The optimal angle curves of each joint were obtained, and the optimal time-jerk trajectory planning of the excavator was realized. Experimental results show that the SQP method under the same weight is more efficient in solving the optimal solution and the optimal excavating trajectory is smoother, and each joint can reach the target point with smaller angular velocity, and acceleration change, which avoids the impact of each joint during operation and conserves working time. Finally, the excavator autonomous operation becomes more stable and efficient.

scholarly journals The Effects of Repetitive Drop Jumps on Impact Phase Joint Kinematics and Kinetics

2011 ◽  
Vol 27 (2) ◽  
pp. 108-115 ◽  
Author(s):  
Joshua T. Weinhandl ◽  
Jeremy D. Smith ◽  
Eric L. Dugan
Keyword(s):  
Energy Absorption ◽  
Plantar Flexion ◽  
Knee Extension ◽  
Joint Kinematics ◽  
Knee Extensors ◽  
Initial Contact ◽  
Drop Jumps ◽  
Impact Phase ◽  
The Impact ◽  
Kinematics And Kinetics

The purpose of the study was to investigate the effects of fatigue on lower extremity joint kinematics, and kinetics during repetitive drop jumps. Twelve recreationally active males (n= 6) and females (n= 6) (nine used for analysis) performed repetitive drop jumps until they could no longer reach 80% of their initial drop jump height. Kinematic and kinetic variables were assessed during the impact phase (100 ms) of all jumps. Fatigued landings were performed with increased knee extension, and ankle plantar flexion at initial contact, as well as increased ankle range of motion during the impact phase. Fatigue also resulted in increased peak ankle power absorption and increased energy absorption at the ankle. This was accompanied by an approximately equal reduction in energy absorption at the knee. While the knee extensors were the muscle group primarily responsible for absorbing the impact, individuals compensated for increased knee extension when fatigued by an increased use of the ankle plantar flexors to help absorb the forces during impact. Thus, as fatigue set in and individuals landed with more extended lower extremities, they adopted a landing strategy that shifted a greater burden to the ankle for absorbing the kinetic energy of the impact.

scholarly journals Hydrodynamic Ram Effect Caused by Debris Hypervelocity Impact on Satellite Tank

2019 ◽  
Vol 9 (20) ◽  
pp. 4200 ◽  
Author(s):  
Beilei Zhao ◽  
Jiguang Zhao ◽  
Cunyan Cui ◽  
Yongsheng Duan
Keyword(s):  
Shock Wave ◽  
Angular Velocity ◽  
Hypervelocity Impact ◽  
Filling Ratio ◽  
Maximum Diameter ◽  
Residual Velocity ◽  
Hydrodynamic Ram ◽  
Ram Effect ◽  
The Impact ◽  
Bulge Height

To study the hydrodynamic ram effect caused by the debris hypervelocity impact on the satellite tank, a numerical simulation of the spherical debris impacting the satellite tank at the velocity of 7000 m/s was carried out based on ANSYS/LS-DYNA software. The attenuation law of debris velocity, the propagation process of the shock wave and the deformation of the tank walls were investigated. The influences of the liquid-filling ratio, the magnitude, and direction of angular velocity on the hydrodynamic ram effect were analyzed. Results show that the debris velocity decreased rapidly and the residual velocity was 263 m/s when the debris passed through the tank. The shock wave was hemispherical, and the pressure of shock wave was the smallest at the element with an angle of 90° to the impact line. The maximum diameter of the front perforation was larger than that of the back perforation and the bulge height on the front wall was smaller than that on the back wall. With the decrease of the liquid-filling ratio, the diameter of the perforations and bulge height decreased. When the debris impacted the satellite tank with the angular velocity in the x direction, the debris trajectory did not deflect. When the debris impacted the satellite tank with the angular velocities in the y and z direction, the debris trajectory deflected to the negative direction of the z axis and y axis, respectively. The magnitude of the angular velocity affects the residual velocity of debris and the diameter of perforations.

scholarly journals Research on the specific movement of the head in tennis strokes

2020 ◽  
Vol 28 (80) ◽  
pp. 16-19
Author(s):  
Manuel Fernández López
Keyword(s):  
Tennis Player ◽  
Effective Technique ◽  
The Gaze ◽  
Impact Phase ◽  
Player Performance ◽  
The Impact

Technique is one of the aspects that has the most relevant influence on tennis player performance. Searching for more efficient and effective technique, by means of the application of biomechanical laws, is a constant among coaches and researchers. This article deals with a very concrete subject in tennis technique: the position of the head during the impact phase of tennis strokes. Biomechanical aspects of the strokes will also be considered, as well as other relevant aspects such as fixing the gaze during the stroke and the stretching-shortening cycle.

A passive dynamic walking model with Coulomb friction at the hip joint

Robotica ◽  
2013 ◽  
Vol 31 (8) ◽  
pp. 1221-1227 ◽  
Author(s):  
Wenhao Guo ◽  
Tianshu Wang ◽  
Qi Wang
Keyword(s):  
Hip Joint ◽  
Coulomb Friction ◽  
Basins Of Attraction ◽  
Swing Phase ◽  
Dynamic Equations ◽  
Two Dimensional ◽  
Dynamic Walking ◽  
Passive Dynamic Walking ◽  
Impact Phase ◽  
The Impact

SUMMARYThis paper presents a modified passive dynamic walking model with hip friction. We add Coulomb friction to the hip joint of a two-dimensional straight-legged passive dynamic walker. The walking map is divided into two parts – the swing phase and the impact phase. Coulomb friction and impact make the model's dynamic equations nonlinear and non-smooth, and a numerical algorithm is given to deal with this model. We study the effects of hip friction on gait and obtain basins of attraction of different coefficients of friction.

On the Importance of the Tax System in Marginal Cost of Funds Calculations

2011 ◽  
Vol 11 (1) ◽  
Author(s):  
Mickael Beaud
Keyword(s):  
General Equilibrium ◽  
Marginal Cost ◽  
Analytical Formula ◽  
Value Added ◽  
Tax Revenue ◽  
Empirical Estimates ◽  
Analytical Formulas ◽  
The Impact ◽  
Labor Income Taxation ◽  
Marginal Cost Of Funds

Abstract Several papers have attempted to derive computable analytical formulas for the Marginal Cost of Funds (MCF). However, this literature is often cast in the pure labor supply general equilibrium model, which is not completely consistent with real tax systems where Labor Income Taxation (LIT) is not the only instrument used by governments. Hence, we explicitly introduce Value-Added Taxation (VAT) on consumption goods in the conventional model, and we derive an analytical formula for the MCF which does incorporate general equilibrium interactions between the different tax bases. Then, we illustrate how much this matter for empirical estimates of MCF using French data. Our numerical example suggests that, when computing MCF for a LIT reform, taking account of the impact of LIT reform on tax revenue from VAT can make a great deal of difference, typically increasing MCF and accounting for around 0.2 to 0.8 of estimates. In addition, MCF is then really less likely to be less than one than in the conventional framework.

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