Path Curve Research Articles

Nonlinear Optimization Method for Transmission Error of Hypoid Gear Machined by the Duplex Helical Method

In this study, synchronous cutting of concave and convex surfaces for hypoid gear was achieved using a duplex helical method. Precise, nonlinear optimization of the transmission error driven by machine tool parameters was performed to reduce the vibration noise of the gear pair. First, the transmission error curve and contact path of the tooth surface of the initial pinion were solved using tooth contact analysis. Second, according to the preset parabolic transmission error curve, the initial gear was used to generate the target pinion, which coincided with the contact path of the initial pinion. Finally, a deviation correction model of the discrete points, corresponding to the contact paths on the concave and convex surfaces of the target and initial pinions, was established. This model was solved using the Levenberg–Marquard algorithm with the trust region strategy, to obtain optimized machine tool parameters. Synchronous optimization of the transmission errors of concave and convex surfaces of the pinion was achieved by correcting the deviations of the contact points. The effectiveness of the proposed method was verified by a numerical example and by performing a contact area rolling test.

Performing the Kick During Walking for RoboCup 3D Soccer Simulation League Using Reinforcement Learning Algorithm

Nowadays, humanoid soccer serves as a benchmark for artificial intelligence and robotic problems. The factors such as the kicking speed and the number of kicks by robot soccer players are the most significant aims that the participating teams are pursued in the RoboCup 3D Soccer Simulation League. The proposed method presents a kicking strategy during walking for humanoid soccer robots. Achieving an accurate and powerful kicking while robots are moving requires a dynamic optimization of the speed and motion parameters of the robot. In this paper, a curved motion path has been designed based on the robot position relative to the ball and the goal. Ultimately, the robot will be able to kick at the goal by walking along this curve path. The speed and angle of the walking robot are set towards the ball with regard to the robots curved motion path. After the final step of the robot, the accurate and effective adjustment of these two parameters ensures that the robot is located in the ideal position to perform the perfect kick. Due to the noise and walking condition of the robot, it is essential that the speed and angle of motion to be measured more accurately. For this purpose, we use a reinforcement learning model to adjust the robots step size and so does achieve the optimal value of two abovementioned parameters. Using reinforcement learning, robot would learn to pursue an optimal policy to correctly kick towards designated points. Therefore, the proposed method is a model-free and based on dynamic programming. The experiments reveal that the proposed method has significantly improved the team overall performance and robots ability to kick. Our proposed method has been 9.32% successful on average and outperformed the UTAustinVilla agent in terms of goal-scoring time in a non-opponent simulator.

Study of error compensations and sensitivity analysis for 6-Dof serial robot

PurposeThe purpose of this paper is to improve the positioning accuracy of 6-Dof serial robot by the way of error compensation and sensitivity analysis.Design/methodology/approachIn this paper, the Denavit–Hartenberg matrix is used to construct the kinematics models of the robot; the effects from individual joint and several joints on the end effector are estimated by simulation. Then, an error model based on joint clearance is proposed so that the positioning accuracy at any position of joints can be predicted for compensation. Through the simulation of the curve path, the validity of the error compensation model is verified. Finally, the experimental results show that the error compensation method can improve the positioning accuracy of a two joint exoskeleton robot by nearly 76.46%.FindingsThrough the analysis of joint error sensitivity, it is found that the first three joints, especially joint 2, contribute a lot to the positioning accuracy of the robot, which provides guidance for the accuracy allocation of the robot. In addition, this paper creatively puts forward the error model based on joint clearance, and the error compensation method which decouples the positioning accuracy into joint errors.Originality/valueIt provides a new idea for error modeling and error compensation of 6-Dof serial robot. Combining sensitivity analysis results with error compensation can effectively improve the positioning accuracy of the robot, and provide convenience for welding robot and other robots that need high positioning accuracy.

FIXED POINT CHAOS AND FOLD/FOLD BURSTING OF A CLASS OF DUFFING SYSTEMS AND THE MECHANISM ANALYSIS

In this paper, a class of bistable Duffing type system with two slow variables under new materials is explored. The system is simulated by time history diagram, phase diagram and bifurcation diagram, then the dynamic mechanism of the system under different parameters is analyzed theoretically. Firstly, this manuscript describes that when the amplitude parameter value is greater than 1, the system may exhibit fixed point chaos and explains the reason of fixed point chaos. Secondly, this manuscript introduces the phenomenon of Fold/Fold bursting in parameter space which is caused by the movement of the system from one side of the saddle-node surface to the other side. We also call it saddle-node bursting. In fact, when the system passes through the saddle-node surface, the number of equilibrium points changes. Then this manuscript uses the path of longitudinal parabolic to explain the mechanism of Fold/Fold bursting. And it is found that regardless of the value of constant coefficient term and amplitude, as long as a certain relationship is satisfied, there will always be Fold/Fold bursting. Next this manuscript uses the linear path to discuss the influence of newly added constant coefficient term. It is found that the position where the path intersects the saddle-node surface will affect the symmetry of the bursting, and the span of the path will affect the magnitude of the bursting oscillation. Finally, this manuscript uses the multiple inflection curve path to discuss the phenomenon when two incentive terms have specific relation. When $n=3$, the change of the constant coefficient term will make the system show Fold/Fold bursting with different times, and the maximum can reach triple bursting. Moreover, it is found that if you can find a path that can be divided into $n$ segments, and each segment will have an intersection with the saddle surface, then $n$ times Fold/Fold bursting will occur.

Geodesic Loewner paths with varying boundary conditions.

Equations of the Loewner class subject to non-constant boundary conditions along the real axis are formulated and solved giving the geodesic paths of slits growing in the upper half complex plane. The problem is motivated by Laplacian growth in which the slits represent thin fingers growing in a diffusion field. A single finger follows a curved path determined by the forcing function appearing in Loewner's equation. This function is found by solving an ordinary differential equation whose terms depend on curvature properties of the streamlines of the diffusive field in the conformally mapped 'mathematical' plane. The effect of boundary conditions specifying either piecewise constant values of the field variable along the real axis, or a dipole placed on the real axis, reveal a range of behaviours for the growing slit. These include regions along the real axis from which no slit growth is possible, regions where paths grow to infinity, or regions where paths curve back toward the real axis terminating in finite time. Symmetric pairs of paths subject to the piecewise constant boundary condition along the real axis are also computed, demonstrating that paths which grow to infinity evolve asymptotically toward an angle of bifurcation of π/5.

Tool Path Optimization for Robotic Surface Machining by Using Sampling-Based Motion Planning Algorithms

Abstract This paper develops a tool path optimization method for robotic surface machining by sampling-based motion planning algorithms. In the surface machining process, the tool-tip position needs to strictly follow the tool path curve and the posture of the tool axis should be limited in a certain range. But the industrial robot has at least six degrees-of-freedom (Dof) and has redundant Dofs for surface machining. Therefore, the tool motion of surface machining can be optimized using the redundant Dofs considering the tool path constraints and limits of the tool axis orientation. Due to the complexity of the problem, the sampling-based motion planning method has been chosen to find the solution, which randomly explores the configuration space of the robot and generates a discrete path of valid robot state. During the solving process, the joint space of the robot is chosen as the configuration space of the problem and the constraints for the tool-tip following requirements are in the operation space. Combined with general collision checking, the limited region of the tool axis vector is used to verify the state’s validity of the configuration space. In the optimization process, the sum of the path length of each joint of the robot is set as the optimization objective. The algorithm is developed based on the open motion planning library (OMPL), which contains the state-of-the-art sampling-based motion planners. Finally, two examples are used to demonstrate the effiectiveness and optimality of the method.

An Improved A* Algorithm Applying to Path Planning of Games

Pathfinding is the core issues in the artificial intelligence field of games, and how to establish an effective method of pathfinding is still focused on. A* algorithm is the most widespread type of game pathfinding at present but the problems still exist such as the curve path and the time-consuming. Based on the analysis and research of traditional A* algorithm, this paper proposes an A* algorithm based on region search. Firstly, the algorithm divides the game map into several connected regions where the role can move freely and without barriers. Then the algorithm uses region search instead of node search. It reduces the search path and the search time. According to the portal between regions, the optimal feasible path is extracted from the region paths. It can effectively solve the zigzag path problem. Experimental simulation results show that the algorithm has shorter search time and can generate smoother path and meet the real-time and real experience requirements of pathfinding in the game.

On the motion of a damped rigid body near resonances under the influence of harmonically external force and moments

This paper presents the motion of a harmonically excited dynamical system with three degrees of freedom (3-DOF) in which it consists of a connected rigid body with a damped spring pendulum whose suspension point moves in a Lissajous curve path. Multiple scales method is utilized to obtain the asymptotic solutions of the equations of motion up to third approximation. Some types of resonances and the conditions of solvability for the steady state solutions have been clarified in light of the achieved modulation equations. The temporal representation of the achieved solutions and resonance curves are presented in some plots to show the good effect of the distinct parameters on the dynamical motion of the investigated system. The numerical solutions of the governing system of motion are gained utilizing the Runge–Kutta method from fourth order. The comparison between these solutions and the analytical ones reflects the good accuracy of the analytical solutions and the used perturbation techniques.

Tourniquet fixing prior to knot tying reduces forces during aortic valve replacement: experimental results from 18 surgeons.

To increase the safety of aortic valve replacement, we developed the 'Caput medusae' method, where the prosthesis is prefixed with circumferential tourniquets prior to knot tying. We assumed that an even distribution of forces may help reduce tissue damage. To confirm this theoretically, we compared forces between knots and tourniquets. The experimental set-up included a device with movable acrylic plates, a mounted valve and a set of sutures. Traction forces were measured with a luggage scale. Two different tourniquets were compared individually and as bundles of 15. Force-path curves were generated. Knotting and tourniquet forces of 18 staff surgeons were then compared. Both modalities were measured 10 times on 2 days, resulting in 40 observations per surgeon, or 360 observations per modality. Polyvinyl chloride tourniquets were stiffer than silicone, expressed by a 1.5- to 1.7-fold higher regression-line slope. Fifteen simultaneous tubes produced force increments 7.9-8.9 times higher than their single counterparts. Overall knotting force was 13.64 ± 5.76 vs tourniquet 1.08 ± 0.48 N. Male surgeons' knotting forces were higher compared to female staff (14.76 ± 6.01 vs 10.73 ± 3.74 N; P < 0.001) while tourniquet forces did not differ (1.09 ± 0.47 vs 1.05 ± 0.49 N; P = 0.459). Dedicated valve surgeons (n = 10) tightened the tourniquets more strongly than inexperienced surgeons (1.20 ± 0.52 vs 0.94 ± 0.37 N; P < 0.001); knotting was similar. Multivariable analysis confirmed only valve experience as a predictor of tourniquet strength (experienced surgeons exerted higher force). Tourniquets exert less force on the tissue than knots. When distributed over the circumference, they can reduce local tension and avoid potential paravalvular leakage. Complete or partial use of tourniquets may thus be an additional option to enhance surgical safety.

Rigid-Flexible Coupling Dynamics Simulation of Wedge Press

In this paper, according to the installation and replacement process of disc single edge hob, the automatic disassembly process of the press wedge of hob is selected as the main object for analysis and research, and a press wedge disassembly device is proposed based on the mechanical design theory, and its structure design and simulation analysis are carried out. First of all, through the understanding of the development and research status of tool change technology at home and abroad, the structure of tool box and the disassembly process of disc hob are analyzed. The disassembly process is divided into three steps, and the expected path curve is obtained by cubic spline interpolation. Secondly, a kind of wedge removal device is proposed and designed. The design scheme is divided into two parts: wedge clamping mechanism and path guiding mechanism. The functional requirements and mechanism realization methods are discussed respectively. The wedge clamping mechanism realizes the clamping power by transforming the traditional three claw chuck, and the path guiding mechanism adopts the two degree of freedom mechanical arm to realize the wedge pressing along the expected curve path In order to verify its feasibility and rationality, the nx10.0 software is used to build the three-dimensional assembly model of the wedge removal device. Then, the trajectory planning simulation of the two degree of freedom manipulator is carried out, the manipulator model is established by using Matlab / Robotics toolbox, and the correctness of the kinematic equation is verified by comparative solution; the workspace of the manipulator is obtained by Monte Carlo simulation, and the correctness of the theoretical working area of the manipulator is verified by comparison; the method of quintic polynomial and cubic spline interpolation is adopted Methods the multi node trajectory planning of the manipulator joint was carried out, and the displacement, velocity and acceleration curves of the two joints of the manipulator were calculated based on the intermediate data points of the expected path, which verified the good motion stability of the manipulator. Finally, the virtual prototype model of the wedge removal device is established by the joint simulation method of Adams and ANSYS, and the rigid flexible coupling dynamic simulation analysis is carried out to simulate the movement track of the wedge in the removal process, which is basically consistent with the expected path curve, which verifies the feasibility of the removal device; the stress distribution of the connecting rod is evaluated and analyzed to verify that the connecting rod can meet the material requirements Material strength requirements.

A Time-Varying Lookahead Distance of ILOS Path Following for Unmanned Surface Vehicle

This paper is concerned with the path following control for an unmanned surface vessel subject to unknown dynamics and external disturbance. Firstly, an integral Line-of-Sight navigation strategy based on a fuzzy strategy to optimize lookahead distance to achieve faster convergence speed is proposed. Then a novel adaptive course control law based on trajectory linearization control technology is proposed, which is combined with the integral Line-of-Sight navigation strategy to form a complete unmanned surface vessel path following strategy. From the author's point of view, this is the first time that trajectory linearization control technology has been applied to the path following scheme by controlling the course. At the same time, in order to improve the robustness of the path following system, the unknown dynamics, external disturbance, and error in the system are compensated by neural network minimum learning parameter method with less computational complexity and a robust term, respectively. Furthermore, hyperbolic tangent function, Nussbaum function, and neural shunting model are introduced into the design of control law to solve the potential input saturation problem. Finally, the numerical simulation experiments of straight line and curve path following are given to prove the feasibility and universality of the whole set of path following scheme.

Smooth Path Planning of Ackerman Chassis Robot based on Improved ant Colony Algorithm

In the domain of robotics and autonomous driving, the automatic path planning of vehicle collision-free motion is an essential task on the navigation level. It is found that the traditional path planning algorithm and the ployline path cannot fully meet the driving requirements of Ackerman chassis robot. In order to solve the autonomous navigation problem of Ackerman chassis mobile robot in structured environment, this paper presents a new improved algorithm. The method of configuration space can introduce the robot's own structural size parameters into the algorithm. Through convex polygon detection method, the local U-shaped area in the map is transformed into a closed area. The essence of these two strategies is to preprocess the map. The initial pheromone distribution is no longer globally uniform, but is distributed according to the terrain. The volatilization factor of pheromone is changed from static constant to dynamic one, which is combined with Poisson distribution law. This strategy makes the improved pheromone distribution law not only avoid the randomness and blindness in the initial stage of the algorithm, but also ensure the ant colony's exploration behavior and guiding role in the middle stage of the algorithm. Path smoothing is also a challenging task. This algorithm optimizes the path step by step by improving the evaluation function, removing redundant nodes and 2-turning algorithm. Thus, a collision free smooth path suitable for Ackerman robot is obtained. This paper combines a variety of algorithm improvement strategies, not only improving the performance of ant colony algorithm path exploration, but also planning a smooth curve path suitable rather than polyline for Ackerman mobile robot tracking. The algorithm is coded and simulated by MATLAB, and the feasibility and effectiveness of the algorithm are verified. This will provide an important basis for the subsequent algorithm migration and lay the foundation for the path tracking control of the Ackermann chassis robot.

Delayed Bilateral Teleoperation of the Speed and Turn Angle of a Bipedal Robot

SUMMARYThis paper proposes a shared control scheme which aims to achieve a stable control of the speed and turn of a bipedal robot during a delayed bilateral teleoperation. The strategy allows to get a delay-dependent damping value that must be injected to assure a bounded response of the hybrid system, while simultaneously, the human operator receives a force feedback that help him to decrease the synchronism error. Furthermore, a test where a human operator handles the walking of a simulated bipedal robot, to follow a curve path in front of varying time delay, is performed and analyzed.

Understanding spatial-temporal evolution of renewable energy technology innovation in China: Evidence from convergence analysis

This paper constructs a knowledge-stock indicator to explore the trend of renewable energy technology innovation (RETI) levels across China's provinces during 1997–2015. First, the spatial-temporal evolution is analyzed. Second, the convergence characteristics and patterns are identified through the nonlinear time-varying factor model and the relative transition path curves. Third, the drivers of convergence behaviors are examined. The results are as follows: (i) China's RETI experienced a spurt of development. Its spatial pattern has changed significantly, and the average annual growth rate has also shown spatial differences; (ii) China's provincial RETI level was not converged as a whole during the sample period, but exhibited club convergence characteristics. The 30 provinces eventually converged to three clubs with large differences in average RETI level and annual growth rate; (iii) the provinces with a more optimized industrial structure, a greater R&D investment intensity, and a higher environmental regulation intensity tended to converge to the club with a higher innovation level and growth rate.

Planar Path Following Control for Wave Glider and Experimental Study

Qi, Z.; Wang, B.; Qin, Y.; Shi, J., and Zhai, J., 2020. Planar path following control for wave glider and experimental study. In: Zheng, C.W.; Wang, Q.; Zhan, C., and Yang, S.B. (eds.), Air-Sea Interaction and Coastal Environments of the Maritime and Polar Silk Roads. Journal of Coastal Research, Special Issue No. 99, pp. 16-20. Coconut Creek (Florida), ISSN 0749-0208.This paper addresses a path following problem of Wave Glider along a predefined path in horizontal plane. The path following controller designing is challenging since Wave Glider is weak maneuvering, underactuated, inaccuracy mathematical model and large environmental disturbances. First, a planar curve path tracking error model is established in the Serret-Frenet coordinate frame. Based on the LOS guidance law and the virtual target method, a planar guidance controller for underactuated Wave Glider is presented to ensure the stability of the path following. And then, according to the classic feedback linearization PID controller and fuzzy controller, a fuzzy adaptive PID controller is developed. Fuzzy controller is used to achieve PID controller parameters online adaptive adjust, in order to improve the robustness of the control system under the influence of environmental disturbances and inaccuracy modeling parameters. Furthermore, analyzing the typical application scenarios of Wave Glider, we set two simulation path in horizontal plane named polyline path and circular path. Numerical simulation results illustrate the proposed control design is effective to deal with planar following problem of Wave Glider. Two sea trails show that the controller can achieve the path following task, however, the speed of Wave Glider is directly related to the accuracy of the path following.

Integral vector field control for three-dimensional path following of autonomous underwater vehicle

A new control method for autonomous underwater vehicle (AUV) is developed to achieve three-dimensional (3D) path following under ocean current disturbances when AUV lacks lateral and vertical driving forces. To make the control system more convenient for practical application and reduce the energy consumption of AUV, the controller is designed with relative velocities. To avoid the singularity problem of curve path following, the Serret–Frenet frame is introduced as virtual target and the error model is defined. The adaptive law of the virtual target and an integral vector field (IVF) guidance law are designed in the kinematic controller. The back-stepping method and adaptive dynamical sliding mode control (BADSMC) technology are applied in the design of dynamic controller. The Lyapunov theory and nonlinear cascade system theory are applied to prove the closed-loop stability. Finally, the performances of the IVF + BADSMC and ILOS + PID algorithm are compared through simulation. Simulation results demonstrate that the proposed controller can realize the path following of AUV under disturbances of ocean current and can improve the following quality.

Effect Range of the Material Constraint in Different Strength Mismatched Laboratory Specimens

Different strength mismatched laboratory specimens that contain the compact tension (CT), single edge-notched tensile (SENT), and central-cracked tension (CCT) specimens with various specimen geometries, loading configurations, and initial cracks were selected to investigate the effect range of the material constraint systematically. The results showed that the effect range of material constraint exists in all the strength mismatched specimens and structures. The numerical value of the effect range is influenced by the geometry constraint. The high geometry constraint reduces the effect range of material constraint. When a material is located outside the effect range of material constraint, the fracture resistance curves and crack propagation paths of the specimens and structures are no longer influenced by the mechanical properties of the material. In addition, an interaction exists between the geometry constraint and material constraint. The high geometry constraint strengthens the effect of material constraint, whereas the fracture resistance curve and crack propagation path are insensitive to the material constraint under the low geometry constraint. The results in this study may provide scientific support for the structure integrity assessment and the design of strength mismatched structures.

Five-Axis Freeform Surface Color Printing Technology Based on Offset Curve Path Planning Method

Great progress has been made in 2D color printing with inkjet technology, and mature related products have come out, but there still exists great developmental space in 3D color printing. Therefore, a new path planning method based on the offset curve for 3D inkjet technology is proposed in this paper. Offset curves are generated on a freeform surface with geodesic equidistance, and then points for color printing are generated along the offset curves. In this paper, the principle of color printing technology with a 5-axis platform and the offset curve path planning (OCPP) method are presented. In addition, comparisons between the OCPP and adaptive filling algorithm based on the section method (AFSM) have been implemented. The OCPP significantly increased the rate of the theoretical filling area from 0.89 to 0.99 on a freeform surface.

3D Curve Generation Using Spherical Polar Piecewise Interpolation in CAD and CAM

In this paper a newly 3D path planning approach and curve generation for design and manufacturing efficiency is considered. The 3D path is generated by a combination of piecewise interpolating curves - along a given number of via-points - created via a spherical coordinate system specified by the polar angles, radial distances and the associated azimuthal angles. Each piecewise interpolating curve is constructed using Hermite polar interpolation in the projective polar plane and the rotating azimuthal plane. To verify the proposed approach, numerical simulations for the generation of a helix design, a 4 and 6 leaf design and a trajectory planning of a picking robot arm are conducted.

ANALYSIS OF CONSTRUCTION MANAGEMENT MAIN ROAD IN THE CISUMDAWU STA.21+200 – STA.22+825 TOLL ROAD PROJECT

Construction management is an attempt to use limited resources efficiently, effectively and timly in completing a project that has been palnned. There are 3 kinds of basic functions of construction management including planning, implementation, and control. Of three of these activities to control the resources on aproject that includes worker, equipment, material, money, and method.The research method used was qualitative research, as a way of collecting data on the study is how the study of the literature, interviews and direct observation in field. And this method is a method that is done to get a foundation theory in analyzing data, namely the analysis calculation of the volume of material, analysis of labor, analysis tool, method, method of Bar Chart S Curve and Critical Path Method.The location of the studies reviewed were Main Road in the Cisumdawu STA.21+200 – STA.22+825 Toll Road Project , located on Pamatutan Hamlet Mulyasari – Pasir Hamlet Margamukti, Sumedang. The results of this research is the budget plan costs  completed the construction of Main Road in the Cisumdawu STA.21+200 – STA.22+825 Toll Road Project till the final stage more or less cost is Rp. 121.488.578.000 and analysis of the Critical Path Method (CPM) estimated completion of the Main Road in the Cisumdawu STA.21+200 – STA.22+825 Toll Road Project takes 58 weeks (406 days).Keywords: Construction Management, Bar Chart, S Curve, Critical Path Method.Â