Paths Generated Research Articles

Congestion avoiding heuristic path generation for the proactive route guidance

The benefits in reducing traffic congestion of system optimum with respect to user equilibrium traffic assignments are well-known. Recently a linear programming based approach was proposed that aims at achieving a compromise between the system perspective, namely eliminating congestion, and the user perspective, that is minimizing individual travel times. The approach, called proactive route guidance, assigns to users paths that increase the travel times by at most a given percentage, called Maximum allowed travel inconvenience. The approach requires the enumeration of all feasible paths that may be memory and time consuming, especially when large networks and/or high values of the Maximum allowed travel inconvenience are considered. In this paper a heuristic is presented to generate a subset of all feasible paths that is based on the iterative search of improving paths. Computational experiments show that the number of paths generated by the heuristic is smaller with respect to the complete set by one or two orders of magnitude on small instances and by higher orders of magnitude when the size of the instances increases. On instances with 150 nodes, where the complete enumeration takes an acceptable computational time, the results show that the quality of the heuristic solutions is very close to that of the optimal ones.

Single arm robotic garment folding path generation

We address the accurate single arm robotic garment folding. The folding capability is influenced mostly by the folding path which is performed by the robotic arm. This paper presents a new method for the folding path generation based on the static equilibrium of forces. The existing approach based on a similar principle confirmed to be accurate for one-dimensional strips only. We generalize the method to two-dimensional shapes by modeling the garment as an elastic shell. The path generated by our method prevents the garment from slipping while folding on a low friction surface. We demonstrate the accuracy of this approach by comparing our paths (a) with the existing method when one-dimensional strips of different materials were modeled, and (b) experimentally with real robotic folding.

Tool path generation algorithm based on covariant field theory and cost functional optimization and its applications in blade machining

In order to improve the quality of the tool path, different machining requirements have to be considered in the tool path generation process. The traditional tool path generation methods only consider one or a few requirements and ignore the others due to the lack of comprehensive mathematic framework. Tool path generated in this way normally is not fully optimized since different requirements could compete or even conflict with each other. Targeting at this issue, this paper presents a unified mathematic framework based on field theory to generate tool path for both planar and freeform surface, where the three most important factors in NC machining, i.e., the smoothness, evenness, and machining efficiency of tool path can be considered. In the proposed framework, a field-based cost functional and a gradient-field-based inequality constraint functional is established, so as to convert the multi-objective tool path computation into a functional minimization problem with inequality constraints. Then, a finite element method (FEM)-based numerical method is proposed to solve the multi-variable nonlinear optimization problem. After that, two smooth tool path generation methods are proposed with taking the step-over as constraint. To further improve the machining efficiency, this paper also provides a hybrid method that combines zigzag and spiral pattern tool path. Experiments on blade machining and simulation show that the proposed method can produce smooth tool paths, while the machining efficiency can be improved at the same time. In addition to the above advantages, the proposed mathematical framework is extensible by incorporating different machining requirements into it, making it possible to generate tool path when multi-objective is considered.

Polygonal model based cutter location data generation with offset error compensation

Purpose As manufacturing technology has developed, digital models from advanced measuring devices have been widely used in manufacturing sectors. To speed up the production cycle and reduce extra errors introduced in surface reconstruction processes, directly machining digital models in the polygonal stereolithographyformat has been considered as an effective approach in rapid digital manufacturing. In machining processes, Cutter Location (CL) data for numerical control (NC) machining is generated usually from an offset model. This model is created by offsetting each vertex of the original model along its vertex vector. However, this method has the drawback of overcut to the offset model. The purpose of this paper is to solve the overcut problem through an error compensation algorithm to the vertex offset model. Design/methodology/approach Based on the analysis of the vertex offset method and the offset model generated, the authors developed and implemented an error compensation method to correct the offset models and generated the accurate CL data for the subsequent machining process. This error compensation method is verified through three polygonal models and the tool paths generated were used for a real part machining. Findings Based on the analysis of the vertex offset method and the offset model generated, the authors developed an error compensation method to correct the offset models and generated the accurate CL data for the subsequent machining process. The developed error compensation algorithm can effectively solve the overcut drawback of the vertex offset method. Research limitations/implications The error compensation method to the vertex offset model is used for generating the CL data with the using of a ball-end cutter. Practical implications On the study of CL data generation for a STL model, most of the current studies are focused on the determination of the offset vectors of the vertexes. The offset distance is usually fixed to the radius of the cutter used. Thus, the overcut problem to the offset model is inevitable and has not been much studied. The authors propose an effective approach to compensate the insufficient distance of the offset vertex and solve the overcut problem. Social implications The directly tool paths generation from a STL model can reduce the error of surface reconstruction and speed up the machining progress. Originality/value The authors investigate the overcut problem occurred in vertex offset for CL data generation and present a new error compensation algorithm for generating the CL data that can effectively solve the overcut problem.

Five-axis finishing tool path generation for a mesh blade based on linear morphing cone

Abstract Blisk is an essential component in aero engines. To maintain good aero-dynamic performance, one critical machining requirement for blades on blisk is that the generated five-axis tool path should be boundary-conformed. For a blade discretely modeled as a point cloud or mesh, most existing popular tool path generation methods are unable to meet this requirement. To address this issue, a novel five-axis tool path generation method for a discretized blade on blisk is presented in this paper. An idea called Linear Morphing Cone (LMC) is first proposed, which sets the boundary of the blade as the constraint. Based on this LMC, a CC curve generation and expansion method is then proposed with the specified machining accuracy upheld. Using the proposed tool path generation method, experiments on discretized blades are carried out, whose results show that the generated tool paths are both uniform and boundary-conformed. Highlights Five-axis finishing tool path based on Linear Morphing Cone (LMC) is presented. The method is implemented on a mesh model. Tool path generated from the proposed method is boundary-conforming. Boundaries of the machining region can be arbitrarily assigned. Experiments are carried out on two mesh blades.

Online Path Planner For Autonomous Mobile Robots By Combining Laplace Potential Method And Graph Theory

In order to generate a path for obstacle avoidance, the Laplace potential method has been proposed. This method requires a great deal of calculat ion amount for generating potential. It is difficult to apply this method for the robot that operates in unknown environments because calculation costs for the method must be smaller. In this paper, the authors propose a new method which has small amount of calculation by combining the graph theory and the Laplace potential method. The simulat ion shows several results. First, the end point of the path generated by the proposed method is in the goal coordinate correctly. Second, the calculation time to generate path is smaller than the Laplace potential method. The authors remark that the success rate of path generation and the reduction amount of computational time are in the trade-off.

A Surface Parameter-Based Method for Accurate and Efficient Tool Path Generation

Along with the increasing need for multi-axis and multi-tasking machining tools for the machining of complex free surfaces, the importance of CAM applications related to the accuracy of the free surfaces has increased dramatically. The machining accuracy and surface integrity of a product depends not only on the performance of the machining tool itself but also on the tool path generated by CAM. At present, there is a trade off between numerical calculation errors and cost in CAM. There is no calculation method that satisfies both sides. Of particular importance is the fact that the cost increases exponentially with the rank of the free surface. Therefore, this paper proposes a new method of generating tool paths efficiently; it generates tool paths directly from 2-dimensional parametric space by using the parametric surface defined as a polynomial. We confirm that this method can reduce the cost and that the tool path can be generated by means of a simple calculation process, without considering singular points. Moreover, since commercial CAM kernels cannot accommodate to our method, we design and implement a new CAM kernel that can access the parametric surface directly in order to develop this method.

Automatic Generation of Data Flow Test Paths using a Genetic Algorithm

testing a program involves generating all paths through the program, and finding a set of program inputs that will execute every path. Since it is impossible to cover all paths in a program, path testing can be relaxed by selecting a subset of all executable paths that fulfill a certain path selection criterion and finding test data to cover it. The automatic generation of such test paths leads to more test coverage paths thus resulting in efficient and effective testing strategy. This paper presents a structural-oriented technique that uses a genetic algorithm (GA) for automatic generation of a set of test paths that cover the all-uses criterion. In the case of programs that have loops, the proposed technique generates paths according to the ZOT-subset criterion, which requires paths that traverse loops zero, one and two times. The proposed GA uses a binary vector as a chromosome to represent the edges in the DD-graph of the program under test. The set of paths generated by the proposed GA can be passed to a test data generation tool to find program inputs that will execute them. Experiments have been carried out to evaluate the effectiveness of the proposed GA compared to the random test path generation technique.

A topological-free method for three-axis tool path planning for generalized radiused end milled cutting of a triangular mesh surface

A tool path generation method for a sculptured surface defined by a triangular mesh is presented. Existing tool methods require extensive computer processing power mainly because surface topology for triangular meshes is not provided. The three-axis tool path planning method presented in this paper for generalized radius end mills avoids this problem (and does not need topological information) by offsetting each triangular facet individually. Offsetting a single triangle results in many more triangles, many of which are redundant, increasing the time required for data handling in subsequent steps. To avoid the large number of triangles, the proposed method creates a bounding space to which the offset surface is limited. Applying the boundary space limits the size of the offset surface resulting in a reduction in the number of triangular surfaces generated. The offset surface generation may still result in unwanted intersecting triangles. The tool path planning strategy addresses this issue by applying hidden-surface removal algorithms. Simulation and machining tests are used to validate the tool paths generated using this method.

A new approach to generating arc length parameterized NURBS tool paths for efficient three-axis machining of smooth, accurate sculptured surfaces

With the development of a new function of computer numerical control controllers, nonuniform rational B-spline (NURBS) interpolation, NURBS tool path generation for sculptured surface machining is under extensive research. The common procedures of the current NURBS tool path planning methods are as follows: first, to find a group of cutter contact points on a sculptured surface; second, to calculate their corresponding cutter locations (CLs); then, to fit a NURBS tool path to the CLs within a prescribed tolerance; and finally, to inspect the tool path for possible gouge by the tool and delete the invalid path segments, if any. However, the NURBS tool path has the following problems: (a) although it passes through the discrete CLs of the theoretical CL path, the deviation along the two paths could be larger than the tolerance; (b) its parameter is not the arc length of the path; and (c) it is difficult to detect gouge along the NURBS path and to remove the invalid segments from it. Consequently, NURBS tool paths generated with the current methods of commercial computer-aided design/computer-aided manufacturing (CAD/CAM) software cannot be used to make smooth and accurate surfaces. To address these problems, this work proposes a new approach to generating arc length parameterized NURBS tool paths with high accuracy in terms of the theoretical CL paths and without gouge and interference. Two practical examples in this work clearly demonstrate the feasibility of this approach and the advantages of the generated NURBS tool paths. Therefore, this approach can be implemented into the CAD/CAM software to promote NURBS machining in industry.

Generation of Geometric Measurement Collision-Free Path for Curved Part

Collision between the contact probe and the measuring part will occur easily when conducting geometric measurement of the curved parts with complex surface shape. To solve the security problem of geometric measurement, a generation method of collision-free measurement path was proposed. First, collision check was simplified into the calculation of line-surface intersection. Meanwhile, we used bounding box method and triangulation method as auxiliary tools. Then, when dealing with collision avoidance, we utilized bounding box in parametric directions to avoid collisions caused by neighboring surfaces. In addition, we used parameter extreme points to avoid collisions caused by the measuring surface itself. At last, path simulation of a complex curved part verifies the security of the path generated by means of the method proposed in this paper.

Efficient Method for Tool Path Generation Based on Region Intersection for Complex Mesh Surface Machining

The machining efficiency of conventional section plane method is low for complex mesh surface machining. An efficient method for tool path generation based on region intersection is proposed. The mesh surface is first divided into a series of intersection regions, then vertex curvatures in perpendicular directions of tool paths are estimated by local fitting method, and variable tool path intervals are computed according to the curvatures, scallop height and cutter radius, finally redundant cutter location points are removed according to machining precision. Experiment results indicate that tool paths generated by proposed method are avail to promote machining efficiency of complex mesh surface machining.

Novel path generation algorithm for high-speed pocket milling

A novel tool path generation algorithm is presented for high-speed pocket milling. A spiral fashion polyline is obtained by linear interpolation which is offset from the pocket boundary. The control points are then inserted into the polyline under exponential regularisation. Finally, the smooth tool path is generated via B-spline curve fitting. The tool path generated through this method can be directly used by the machine controller with a NURBS interpolation function, which avoids the time-consuming computation of dividing them into many short line segments. Compared with conventional methods of direction-parallel and contour-parallel path generation, the tool paths obtained by this algorithm have less cutting force fluctuation because they are Cncontinuous, smooth and have no direction jump. The engineering applications proved that the presented method can not only save machining time over the conventional algorithm, but also can avoid solving time-consuming scalar elliptic partial differential equations which are needed by existing spiral tool path generation method.

Machining of complex-shaped parts with guidance curves

Nowadays, high-speed machining is usually used for production of hardened material parts with complex shapes such as dies and molds. In such parts, tool paths generated for bottom machining feature with the conventional parallel plane strategy induced many feed rate reductions, especially when boundaries of the feature have a lot of curvatures and are not parallel. Several machining experiments on hardened material lead to the conclusion that a tool path implying stable cutting conditions might guarantee a better part surface integrity. To ensure this stability, the shape machined must be decomposed when conventional strategies are not suitable. In this paper, an experimental approach based on high-speed performance simulation is conducted on a master bottom machining feature in order to highlight the influence of the curvatures towards a suitable decomposition of machining area. The decomposition is achieved through the construction of intermediate curves between the closed boundaries of the feature. These intermediate curves are used as guidance curve for the tool paths generation with an alternative machining strategy called “guidance curve strategy”. For the construction of intermediate curves, key parameters reflecting the influence of their proximity with each closed boundary and the influence of the curvatures of this latter are introduced. Based on the results, a method for defining guidance curves in four steps is proposed.

A novel motion generation strategy for robotic tooth brushing simulator

PurposeThe purpose of this paper is to develop a robotic tooth brushing simulator mimicking realistic tooth brushing motions, thereby facilitating greater understanding of the generation of realistic tooth brushing motion for optimal design of toothbrushes.Design/methodology/approachTooth brushing motions were measured via a motion capture system. Different motion patterns of brushing were analysed. A series of elliptical motion segments were generated by interpolating ellipse‐like trajectories. Furthermore, a path generation algorithm for brushing simulation was proposed. A path planning system incorporating robot motion control was developed to simulate realistic tooth brushing. The generality and efficiency of the proposed algorithm was demonstrated through simulation and experimental results.FindingsThe interpolation of ellipse‐like trajectories can generate elliptical motion segments. Furthermore, realistic tooth brushing can be achieved by integrating the elliptical motion segments into the path generated from the surfaces of teeth. The brushing simulator demonstrated good reproducibility of clinically standardized tooth brushing.Practical implicationsA robotic toothbrush assessment system is a potential application to the robotic tooth brushing simulator by incorporating control of brushing variables, including brushing pressure, speed and temperature.Originality/valueThis study demonstrates the feasibility of using robotic simulation techniques towards improved realistic human tooth brushing motions simulation for optimal design of tooth brushes.

Optimal test sequence generation using firefly algorithm

Software testing is an important but complex part of software development life cycle. The optimization of the software testing process is a major challenge, and the generation of the independent test paths remains unsatisfactory. In this paper, we present an approach based on metaheuristic firefly algorithm to generate optimal test paths. In order to optimize the test case paths, we use a modified firefly algorithm by defining appropriate objective function and introducing guidance matrix in traversing the graph. Our simulations and comparison show that the test paths generated are critical and optimal paths.

Isoscallop of Self-Adaptive Tool Orientation with Toroidal Cutter under Optimum Orientation of MCPs

End-milling of free-form surfaces on 5-sxis NC tools is a complex problem which has been studied by a large number of research scientists. When end-milling non-convex surfaces, there is a risk of interference between the tool and the surface. This paper presents a new approach to generate gouging-free tool path for constant scallop-height machining using 5-axis toroidal milling. Based on second-order approximations of the machined strip width, we present locally optimal cutting positions for cutting directions. The largest machined strip width of iso-scallop and the corresponding gouging-avoidance tool orientation are calculated. In the cutter path generation procedures, the master cutter paths have been chosen from the minimum curvature loci of the surface. The tool path generated by this method are also compared with that of the long edge of surface as the MCP, the results of simulation show that the method can yield a reduction in line segments of tool path . Velocity curve and acceleration curve are smoother.

Multiple path generation by a flexible four-bar mechanism using ionic polymer metal composite

This article presents a novel design of a flexible four-bar crank–rocker mechanism using ionic polymer metal composite for generating multiple paths, which can be applied in microassembly. In order to control the deflection of links and the resultant path, active ionic polymer metal composite patches are fixed on the coupler and are actuated by a voltage (0–3 V direct current). The main focus of this article is to determine the number, size, and location of the ionic polymer metal composite patches to be used on the coupler to get a desired path. A dynamic model of the mechanism is made in ADAMS software and the design parameters are identified. A mathematical model of ionic polymer metal composite patch is developed through experiments to achieve the bending moment relationship with voltage, and this is used while simulating its behaviors. The simulation results show that the proposed mechanism can generate multiple paths, using different voltages for ionic polymer metal composite activation. The proposed mechanism is then fabricated, and experiments are carried out to compare the experimental and simulation results. It is proved that the proposed new mechanism is superior to earlier designs of four bars using ionic polymer metal composite, and the paths generated can more effectively be controlled.

Constant scallop-height tool path generation for three-axis discrete data points machining

This paper presents a new approach for the determination of constant scallop-height tool paths in the machining of discrete data points using three-axis ball-end milling. Compared with the existing approaches for surfaces, this approach avoids offsetting data points, which is complex and time consuming. This paper firstly creates the local coordinate system centered at each CL point of the current path to calculate the corresponding scallop point and then the similar local coordinate system is created at each scallop point to calculate the wanted CL point of the next tool path. The tool paths generated by the approach keep the scallop-height constant and meet the step error requirement. The experiment result indicates that the approach is feasible and efficient and the overall tool path length can be reduced significantly compared with the iso-planar method.

A Path Planning Approach for Wedge/Aspheric Lens Element Grinding Based on Space Coordinate Transformation

Wedge/aspheric lens element is a combination of wedge prism and aspheric lens as a single piece component forming a decentred lens, which plays an important role in the fields of liquid crystal projection display, laser fusion, high-energy laser, satellite optical system and large astronomical telescope, etc. Wedge/aspheric lens element are primarily manufactured by CNC machining, especially 3-axis CNC grinding. This paper presents a facile tool path generation approach based on space coordinate transformation. The proposed method can be used to improve and automate three-axis Wedge/aspheric lens element machining for CAD/CAM systems. As part of the validation process, the tool paths generated are analyzed to compare with the desired part.