Research on a combined proportional guidance method with the terminal point pointing to the predicted encounter point

2021 ◽  
Author(s):  
Wenqi Yang ◽  
Jianhua Lu ◽  
Xu Jiang ◽  
Fei Li
Keyword(s):  
Terminal Point

scholarly journals A Theoretical Analysis of Relations between Pressure Changes along Xylem Vessels and Propagation of Variation Potential in Higher Plants

Plants ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 372
Author(s):  
Ekaterina Sukhova ◽  
Elena Akinchits ◽  
Sergey V. Gudkov ◽  
Roman Y. Pishchalnikov ◽  
Vladimir Vodeneev ◽  
...  
Keyword(s):  
Higher Plants ◽  
Initial Point ◽  
Electrical Signal ◽  
Terminal Point ◽  
Hydraulic Pressure ◽  
Long Distance ◽  
Variation Potential ◽  
Damaged Zone ◽  
Pressure Dynamics ◽  
The Impact

Variation potential (VP) is an important long-distance electrical signal in higher plants that is induced by local damages, influences numerous physiological processes, and participates in plant adaptation to stressors. The transmission of increased hydraulic pressure through xylem vessels is the probable mechanism of VP propagation in plants; however, the rates of the pressure transmission and VP propagation can strongly vary. We analyzed this problem on the basis of a simple mathematical model of the pressure distribution along a xylem vessel, which was approximated by a tube with a pressure gradient. It is assumed that the VP is initiated if the integral over pressure is more than a threshold one, taking into account that the pressure is transiently increased in the initial point of the tube and is kept constant in the terminal point. It was shown that this simple model can well describe the parameters of VP propagation in higher plants, including the increase in time before VP initiation and the decrease in the rate of VP propagation with an increase in the distance from the zone of damage. Considering three types of the pressure dynamics, our model predicts that the velocity of VP propagation can be stimulated by an increase in the length of a plant shoot and also depends on pressure dynamics in the damaged zone. Our results theoretically support the hypothesis about the impact of pressure variations in xylem vessels on VP propagation.

Minimum Energy Control of a Unicycle Model Robot

2021 ◽  
Author(s):  
Youngjin Kim ◽  
Tarunraj Singh
Keyword(s):  
Optimal Control ◽  
Minimum Energy ◽  
Kinematic Model ◽  
Elliptic Functions ◽  
Terminal Point ◽  
Jacobi Elliptic Functions ◽  
Differential Drive ◽  
Terminal Constraints ◽  
Differential Drive Robot ◽  
Point To Point

Abstract Point-to-point path planning for a kinematic model of a differential-drive wheeled mobile robot (WMR) with the goal of minimizing input energy is the focus of this work. An optimal control problem is formulated to determine the necessary conditions for optimality and the resulting two point boundary value problem is solved in closed form using Jacobi elliptic functions. The resulting nonlinear programming problem is solved for two variables and the results are compared to the traditional shooting method to illustrate that the Jacobi elliptic functions parameterize the exact profile of the optimal trajectory. A set of terminal constraints which lie on a circle in the first quadrant are used to generate a set of optimal solutions. It is noted that for maneuvers where the angle of the vector connecting the initial and terminal point is greater than a threshold, which is a function of the radius of the terminal constraint circle, the robot initially moves into the third quadrant before terminating in the first quadrant. The minimum energy solution is compared to two other optimal control formulations: (1) an extension of the Dubins vehicle model where the constant linear velocity of the robot is optimized for and (2) a simple turn and move solution, both of whose optimal paths lie entirely in the first quadrant. Experimental results are used to validate the optimal trajectories of the differential-drive robot.

Waypoint Constrained Multi-Phase Optimal Guidance of Spacecraft for Soft Lunar Landing

2019 ◽  
Vol 07 (02) ◽  
pp. 83-104 ◽  
Author(s):  
Kapil Sachan ◽  
Radhakant Padhi
Keyword(s):  
Selection Procedure ◽  
Landing Site ◽  
Terminal Point ◽  
Computationally Efficient ◽  
Soft Landing ◽  
Hard Constraints ◽  
Optimal Guidance ◽  
Safety Constraints ◽  
Multi Phase ◽  
Time Selection

A waypoint constrained multi-phase nonlinear optimal guidance scheme is presented in this paper for the soft landing of a spacecraft on the Lunar surface by using the recently developed computationally efficient Generalized Model Predictive Static Programming (G-MPSP). The proposed guidance ensures that the spacecraft passes through two waypoints, which is a strong requirement to facilitate proper landing site detection by the on-board camera for mission safety. Constraints that are required at the waypoints as well as at the terminal point include position, velocity, and attitude of the spacecraft. In addition to successfully meeting these hard constraints, the G-MPSP guidance also minimizes the fuel consumption, which is a very good advantage. An optimal final time selection procedure is also presented in this paper to facilitate minimization of fuel requirement to the best extent possible. Extensive simulation studies have been carried out with various perturbations to illustrate the effectiveness of the algorithm. Finally, processor-in-loop simulation has been carried out, which demonstrates the feasibility of on-board implementation of the proposed guidance.

Bolt Strength in Sectional Body Construction of Valves

2019 ◽  
Author(s):  
Bhaskar Shitolé
Keyword(s):  
Rigid Bodies ◽  
Bolted Joints ◽  
Terminal Point ◽  
Piping System ◽  
Valve Body ◽  
Section Modulus ◽  
Creep Characteristics ◽  
Body Construction ◽  
Minimum Requirements ◽  
Body Joints

Abstract ASME B16.34-2017 Section 6.4.2 provides requirements for valves with bolted body joints and threaded body joints. The section states that valves with bodies of sectional construction such that bolted or threaded body joints are subject to piping mechanical loads in addition to the pressure rating for which the valve is designed, shall satisfy the following requirements. For bolted joints, the requirement is a simple formula where the product of pressure rating class designation and ratio of area bounded by the effective outside periphery of a gasket or O-ring or other seal-effective periphery and total effective bolt tensile stress area are less than a certain constant. For bolts of strength less than 137.9 MPa, the value of constant reduces as a multiple of 50.76 times the bolt tensile strength in MPa required or provided in a sectional construction. Section 6.4.3 cautions that the minimum requirements of ASME B16.34 may fall short in scenarios due to valve design, special gaskets, high temperature service, creep characteristics etc. This paper reviews and studies this ASME B16.34 requirement which was triggered by failure of a valve with section body construction in the field. Traditionally valves have been considered as rigid bodies when analyzing a piping system for stresses, support loads, terminal point loads and deflections. The rigid modelling assumes the strength of the valve is much higher than an equivalent straight length of pipe. Some computer programs have a provision that permits modeling the valve as a multiple like 3- or 4-times pipe section modulus. This paper compares the strength of piping and valves based on inherent valve body thickness, body sectional bolting provided and strength of the equivalent piping flanges. The paper makes conclusions for the user to be aware of so that pre-emptive actions can be taken when using valves with sectional body construction.

scholarly journals On the Performance of Linear Decreasing Inertia Weight Particle Swarm Optimization for Global Optimization

2013 ◽  
Vol 2013 ◽  
pp. 1-12 ◽  
Author(s):  
Martins Akugbe Arasomwan ◽  
Aderemi Oluyinka Adewumi
Keyword(s):  
Global Optimization ◽  
Particle Swarm Optimization ◽  
Optimization Problems ◽  
Particle Swarm ◽  
Pso Algorithm ◽  
Search Space ◽  
Terminal Point ◽  
Simulation Experiments ◽  
Swarm Optimization ◽  
Inertia Weight

Linear decreasing inertia weight (LDIW) strategy was introduced to improve on the performance of the original particle swarm optimization (PSO). However, linear decreasing inertia weight PSO (LDIW-PSO) algorithm is known to have the shortcoming of premature convergence in solving complex (multipeak) optimization problems due to lack of enough momentum for particles to do exploitation as the algorithm approaches its terminal point. Researchers have tried to address this shortcoming by modifying LDIW-PSO or proposing new PSO variants. Some of these variants have been claimed to outperform LDIW-PSO. The major goal of this paper is to experimentally establish the fact that LDIW-PSO is very much efficient if its parameters are properly set. First, an experiment was conducted to acquire a percentage value of the search space limits to compute the particle velocity limits in LDIW-PSO based on commonly used benchmark global optimization problems. Second, using the experimentally obtained values, five well-known benchmark optimization problems were used to show the outstanding performance of LDIW-PSO over some of its competitors which have in the past claimed superiority over it. Two other recent PSO variants with different inertia weight strategies were also compared with LDIW-PSO with the latter outperforming both in the simulation experiments conducted.

High-Precision Positioning and Speed Smooth Transition Control Algorithm for Terminal Point of Micro-Line Segment

2011 ◽  
Vol 305 ◽  
pp. 19-24
Author(s):  
Zhui Liang Huang ◽  
Shu Wen Lin ◽  
Dao Ying Jiang
Keyword(s):  
Motion Control ◽  
High Precision ◽  
Line Segment ◽  
Control Algorithm ◽  
Smooth Transition ◽  
Terminal Point ◽  
Precision Positioning ◽  
Line Segments ◽  
Transition Control ◽  
Joint Point

In allusion to the problem of data sampling interpolation error which exists in continuous micro-line segments interpolation algorithm with acceleration /deceleration control, this paper proposes a high-precision positioning and speed smooth transition control algorithm for terminal point of micro-line segment. The linear acceleration/deceleration mode was taken as an example to derive a motion control algorithm, which can eliminate the rounding error of the interpolation with fine adjusting the reserved parameters of acceleration /deceleration process when micro-line segment starting point and terminal point velocity are not zero. Simulation analysis and experiments of motion control shows that the algorithm greatly improves the control accuracy of the joint point position of micro-line segments, achieves the continuous smooth transition at the feed speed of the joint point of adjacent line segments and the uniformity of the velocity in specific line segment.

A Comparison of Direct and Indirect Input Devices in a Volumetric Interactive Virtual Environment Workspace

1998 ◽  
Vol 42 (21) ◽  
pp. 1516-1520
Author(s):  
Robert G. Eggleston ◽  
William P. Janson ◽  
Kenneth A. Aldrich
Keyword(s):  
Virtual Environment ◽  
Degrees Of Freedom ◽  
Descriptive Analysis ◽  
External Input ◽  
Terminal Point ◽  
Input Device ◽  
Input Devices ◽  
Aimed Movement ◽  
Direct Input ◽  
The Impact

The purpose of this study was to evaluate the impact of two different types of input devices on psychomotor performance in a “full” 3D (volumetric) virtual environment. Three subjects used both a direct input device (hand-held stylus) and an indirect input device (6 degree of freedom, fixed mounted force device) to accomplish aimed movement to a target located in one of eight depth planes. Directness was characterized in terms of action space and perception space coincidence and natural kinematic arm-hand movements. Different instructions were used to place different demands on coordination of movement. Aim point performance was evaluated in terms of aiming speed and accuracy, and steadiness at the terminal point. A descriptive analysis showed consistently better performance on all measures with the direct device. A statistical analysis confirmed these trends, although significance often was not always achieved due to limited experimental power. In general, the results suggest an advantage for the direct input device in the range of 30% to 73% across target locations, depending on type of performance measured. The data are discussed in terms of action and perception space coincidence and the coordination of the multiple degrees of freedom property of external input devices.

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