Path Generation Process Research Articles

Data model-based toolpath generation techniques for CNC milling machines

Introduction: With the development of computer technology and data modeling, the use of point cloud models to generate tool paths is particularly important for improving productivity and accuracy.Methods: This study proposes a new method that first preprocesses the point cloud data using four-point denoising and octree methods to improve processing efficiency. Subsequently, roughing tool paths were analyzed using the layer slicing method and finishing paths using the residual height method.Results and Discussion: The experimental results show that the layer slicing method has a minimum error close to 10% on the roughing path generation and the computation time is reduced to 35 s, while the residual height method has an error rate of 10.17% on the finishing path and the computation time is only 11.82 s, which reflects a high trajectory smoothness and accuracy. The above results show that the study not only optimizes the tool path generation process and improves the machining efficiency and accuracy, but also demonstrates the potential application of point cloud models in the machining of complex parts.Conclusion: The novel tool roughing and finishing methods provide more reliable path planning for actual machining operations, and future research will be devoted to further improving the performance of the data processing algorithms and exploring more efficient path planning strategies to facilitate automated production.

PAARGAMAN: Passenger Demand Provoked (On-The-Fly) Routing Of Intelligent Public Transport Vehicle with Dynamic Route Updation, Generation, and Suggestion

Demand-based public bus service meets the need of passengers with less money, time, and resources by reducing the number of private vehicles on the road. In contrast, dynamic real-time demand-based routing faces challenges like elevated travel time due to the requested assignment based on the paths and vehicle availability. Hence, this research introduces a novel framework named Passenger Influence Bus Service-Intelligent Public Transport System (PIBS-IPTS) for efficient routing of available vehicles based on the demand of passengers. For this, optimal paths are elected from the known routes of the general vehicle through the Cuckoo Search (CS) optimization algorithm. Then efficient route prediction is employed by the Artificial Neural Network (ANN) for passenger flow. Here, the unavailability of the passenger request, such as source location or Destination locations, or the unavailability of both locations is updated while employing the path generation process. The path generation process ensures the reduction of request drops generated by the passenger, which elevates the usage of the general bus service. Here, for the optimal selection of routes from the identified routing paths, a multi-objective function based on traffic density, route condition, and route mobility is employed for the selection of a near-optimal global solution. The method’s performance is analyzed using MAE, RMSE, and MAPE and obtained the best values of 0.69, 0.72, and 0.74, respectively.

Tool Path Optimization for Complex Cavity Milling Based on Reinforcement Learning Approach

In the machining of parts, tool paths for complex cavity milling often have different generation options, as opposed to simple machining features. The different tool path generation options influence the machining time and cost of the part during the machining process. Decision makers prefer tool path solutions that have fewer blanking lengths, which means that the machining process is more efficient. Therefore, in order to reduce costs and increase efficiency, it is necessary to carefully design the tool path generation for the features to be machined on the part, especially for complex cavity milling features. However, solutions to the problem of optimal design of tool paths for complex cavity milling features have not been well developed in current research work. In this paper, we present a systematic solution for complex cavity milling tool path generation based on reinforcement learning. First, a grid converter is executed for converting the 3D geometry of the cavity milling feature into a matrix of planar grid points recognisable by the program, set according to the cutting parameters. Afterwards, the tool path generation process is refined and modelled as a Markov decision process. Ultimately, a tool path generation solution combining the A* algorithm with the Q-learning algorithm is executed. The agent iterates through trial and error to construct an optimal tool path for a given cavity milling task. Three case experiments demonstrate the feasibility of the proposed approach. The superiority of the reinforcement learning-based approach in terms of solution speed and solution quality is further demonstrated by comparing the proposed approach with the evolutionary computational techniques currently popular in research for solving tool path optimisation design problems.

Mobile parallel manipulator consisting of two nonholonomic carts and their path planning

Mobile manipulators are widely used to transport and manipulate objects in industrial settings. In this paper, we propose a mobile manipulator that consists of a parallel mechanism and two two-wheel-drive carts. The planar motions of the carts are transmitted to a platform through three screw pairs of the parallel mechanism, allowing the pose of the platform to be controlled by only four motors. Kinematic analysis for such a two-cart mobile manipulator gives a Jacobian matrix, reveals the effects of nonholonomic constraints, and demonstrates that the yaw angle of the platform must be limited to avoid singular and failure configurations, and that the pitch angle is quite sensitive to uncertainties. Based on these analysis results, we present a custom path planning method for the carts. This method provides a non-optimal but easily realizable path planning algorithm with low computational cost, since the complex constraint conditions of this two-cart mobile manipulator have little influence on the proposed path generation process. The path planning process consists of four steps. We describe the motions of the carts in each step and establish a path tracking control system for the carts. Some simulations are conducted to show the motions of the carts, investigate the changes in the pose of the platform, and quantitatively evaluate the sensitivity of the platform’s pitch angle. Moreover, we construct an experimental prototype and conduct experiments to verify the validity and usefulness of the proposed mechanism and path planning method.

Two-Stage Sector Partition Path Planning Method for Automated Fiber Placement on Complex Surfaces

Automated fiber placement (AFP) is an advanced composite manufacturing technology which is widely used in the production of complex shaped aircraft components. However, on the surface with large curvature, the fiber compaction performance is poor, and the direction deviation and the geodesic curvature of the path increase sharply with the offset distance, resulting in various placement defects. To solve this problem, the influence of the surface curvature on the path performance is studied, and a two-stage sector partition path planning method for AFP on complex surface is proposed in this paper. The constraints of the direction deviation, turning radius and the compaction state of the fiber are comprehensively considered in this method. By analyzing the compaction feature, the distance between the roller and the surface is used to evaluate the compaction condition and an initial partition criterion is established according to the normal curvature of the surface along the roller axis. Then, the quantitative relationship between path performance and offset distance is derived, and the precise sector is determined under the constraints of placement direction and turning radius. The path performance constraints are fully considered in the path generation process, so the iterative process of evaluation–modification is effectively avoided. Simulations and experiments are then carried out on the winglet surface and the results show that compared with the parallel method, the proposed method can significantly improve the direction deviation, turning radius and compaction quality of the placement paths at the cost of gaps/overlaps. Satisfactory placement paths can be obtained with reasonable constraints on the complex surface.

Consideration of different travel strategies and choice set sizes in transit path choice modelling

Path choice modelling is typically conducted by considering a subset of paths, not the universal set of all feasible paths as this is computationally challenging. This study proposes a two-stage modelling approach. In the first stage, it develops a new probabilistic importance sampling protocol by using fuzzy logic. In the second stage, it tested different structures of the discrete choice models, where different strategy attributes are considered along with the traditional variables. The results prove that the new sampling protocol performs better than traditional sampling protocol. Again, the inclusion of the strategy attributes proves to yield better prediction. The results of the study recommend considering different strategy attributes in the path generation process as well as in the transit assignment models. The study also discusses the effect of the choice set size on the model performance. Household travel survey data of south-east Queensland, Australia is used to develop the models.

Tool Path Generation for Multi-Degree-of-Freedom Fast Tool Servo Diamond Turning of Optical Freeform Surfaces

Fast tool servo diamond turning is one of the most important techniques for machining optical freeform surfaces. The tool path has a significant effect on roughness, waviness and profile errors. However, the mapping mechanism between the tool path and the surface form error is not precisely expressed. The paper presents a novel approach for modelling and simulation of the tool path generation in fast tool servo diamond turning. The approach, by analyzing scallop-height, linearization error and tool nose radius compensation, models the tool path generation process. The effects and characteristic of an optimized tool path are investigated through simulations. Experiments have been carried out to show that the model is feasible.

Preflight Contingency Planning Approach for Fixed Wing UAVs with Engine Failure in the Presence of Winds.

Preflight contingency planning that utilizes wind forecast in path planning can be highly beneficial to unmanned aerial vehicles (UAV) operators in preventing a possible mishap of the UAV. This especially becomes more important if the UAV has an engine failure resulting in the loss of all its thrust. Wind becomes a significant factor in determining reachability of the emergency landing site in a contingency like this. The preflight contingency plans can guide the UAV operators about how to glide the aircraft to the designated emergency landing site to make a safe landing. The need for a preflight or in-flight contingency plan is even more obvious in the case of a communication loss between the UAV operator and UAV since the UAV will then need to make the forced landing autonomously without the operator. In this paper, we introduce a preflight contingency planning approach that automates the forced landing path generation process for UAVs with engine failure. The contingency path generation aims true reachability to the emergency landing site by including the final approach part of the path in forecast wind conditions. In the contingency path generation, no-fly zones that could be in the area are accounted for and the contingency flight paths do not pass through them. If no plans can be found that fulfill reachability in the presence of no-fly zones, only then, as a last resort, the no-fly zone avoidance rule is relaxed. The contingency path generation utilizes hourly forecast wind data from National Oceanic and Atmospheric Administration for the geographical area of interest and time of the flight. Different from past works, we use trochoidal paths instead of Dubins curves and incorporate wind as a parameter in the contingency path design.

Roaming Path Generation Algorithm and Optimization Based On Bezier Curve

Camera roaming plays an extremely important role in constructing various roaming scenarios for virtual systems. However, the existing path (camera) roaming algorithm has the disadvantages of excessive human participation in the roaming path generation process, unpredictable roaming effect, unsmart camera conversion, and mismatched roaming camera and commentary. Therefore, a convenient and automatic path roaming algorithm is proposed. At the same time, the intelligent conversion of the camera is implemented. Based on this, optimization is performed to enable smart matching between the camera and the commentary audio and narration text. First, the key model in the roaming scene is marked to obtain its spatial position; Then the Bessel curve generation principle is studied, and Bessel splines are fitted to the key points according to the mathematical model of the Bezier curve； And then the camera movement is invoked，and the function implements roaming. Finally, the algorithm is optimized to achieve intelligent matching of voice subtitles and pictures. In this way, the automation and intelligence of the roaming path are realized.

An integrated approach of reverse engineering aided remanufacturing process for worn components

Abstract The worn mechanical components/parts arrived in the remanufacturing system exhibit highly uncontrolled variabilities in failure conditions as well as structures and shape complexities. With the aid of reverse engineering (RE) technologies, a quick and accurate acquisition of the damaged areas of the worn part is attainable and thereby facilitates remanufacturing operations necessary to bring the parts back to like-new conditions. In this paper, a reverse engineering based approach is proposed to aid the remanufacturing processes of worn parts. The proposed approach integrates 3D surface data collection, nominal model reconstruction, fine registration, extraction of additive/subtractive repair, tool path generation and actual machining process, seeking to improve the reliability and efficiency of manual repair process. For nominal model reconstruction, a Prominent Cross-Section algorithm embedded with curvature constraint is proposed to automatically identify the boundary of the part's damaged area and thereby eliminate the defective point clouds from the reconstruction process. With the nominal reconstruction model and the 3D model of the worn part, a modified ICP algorithm integrating curvature and distance constraints is proposed to achieve a best-fit position of the two models by automatically identifying and eliminating the unreliable corresponding pairs through iterations. The proposed approach is demonstrated through remanufacturing of two different mechanical components and is approved to be efficient and effective.

Tool path generation on doubly-curved free-form surfaces

ABSTRACTIn the industries of automobiles and aerospace, the use of carbon fiber has grown exponentially over the years due to its high specific mechanical properties. However, the existing processes for the placement of these fibers within these industries remain either restrictive to the doubly-curved free-formed surfaces required or economically unfeasible in respect to the larger scaled components desired. This paper presents a tool path generation process which will produce non-collisional pathing for the automated placement of uniform fibers on scalable doubly-curved free-formed surfaces. To begin this process, a high detail model of the component part is given and analyzed for optimizing the placement of both the part and the KUKA robot. We account for variable fiber placement angles based on design specifications of the part. The process will begin with a given three-dimensional rendering of the component model which will be transformed into a readable Robotic Scripting Language (RSL) file that the...

Autonomous Manufacturing of Composite Parts by a Multi-Robot System

This work considers an autonomous multi-robot pick-and-place process for the manufacturing of aerospace structures, which consists of the steps picking, transfer, dropping and post-drop treatment. Autonomous production is achieved by combining computer vision assisted gripping, automated transfer path generation and generic process execution in one system. Test scenario is an airplane skin demonstrator made of tailored carbon fiber multiaxial fabrics that are placed in a half-shell shaped jig of approximately 4 m in diameter by two cooperating robots mounted on a common linear axis.

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.

A generic uniform scallop tool path generation method for five-axis machining of freeform surface

In this paper, a generic uniform scallop tool path generation method for five-axis machining is presented. Unlike the conventional methods which are based on the local surface geometry assumptions, this method is inspired by cutting simulation. Initially, the designed surface is planted with dense grasses. If a cutter is put onto the surface, the affected grasses will be cut short. All the affected grasses form a grass ring on the surface. When the cutter moves along the previous tool path, the envelope of the grass rings will form a machining band. Based on the machining band, cutter contact points can be found on the surface to ensure that the cutting edge touches exactly on the side of the band. These cutter contact points are fitted to construct the next tool path. In this way, all the tool paths can be generated recursively. An optimization is also developed to improve the computing efficiency of the path generation process. The proposed uniform scallop tool path generation method is generic. It can be popularized to (1) any kind of end mill with various sizes, (2) any kind of parametric surface and (3) directional- or contour-parallel tool path topologies. Another salient feature of this method is that it is free of local surface geometry assumptions, so the obtained tool paths are more precise. The proposed method is implemented and evaluated with several freeform surface examples. The feasibility of the method is also verified by actual cutting experiment.

A robust 2D point-sequence curve offset algorithm with multiple islands for contour-parallel tool path

An offset algorithm is important to the contour-parallel tool path generation process. Usually, it is necessary to offset with islands. In this paper a new offset algorithm for a 2D point-sequence curve (PS-curve) with multiple islands is presented. The algorithm consists of three sub-processes, the islands bridging process, the raw offset curve generation and the global invalid loops removal. The input of the algorithm is a set of PS-curves, in which one of them is the outer profile and the others are islands. The bridging process bridges all the islands to the outer profile with the Delaunay triangulation method, forming a single linked PS-curve. With the fact that local problems are caused by intersections of adjacent bisectors, the concept of stuck circle is proposed. Based on stuck circle, local problems are fixed by updating the original profile with the proposed basic rule and append rule, so that a raw offset curve can be generated. The last process first reports all the self-intersections on the raw offset PS-curve, and then a procedure called tree analysis puts all the self-intersections into a tree. All the points between the nodes in even depth and its immediate children are collected using the collecting rule. The collected points form the valid loops, which is the output of the proposed algorithm. Each sub-process can be complete in near linear time, so the whole algorithm has a near linear time complexity. This can be proved by the examples tested in the paper.

Applying Branch-and-Bound Technique to Route Choice Set Generation

An algorithm to solve explicitly the path enumeration problem is proposed. This algorithm is based on the branch-and-bound technique and belongs to the class of deterministic methods along with existing approaches that combine heuristic or randomization procedures with shortest-path search. The branch-and-bound algorithm is formulated, and a methodology is designed for the application of deterministic approaches to a real case study. Path sets generated with different methods are compared for behavioral consistency, namely, the ability to reproduce actual routes chosen by individuals driving habitually from home to work. Choice set compositions for modeling purposes are determined for the consistency of the path generation process with the observed behavior. Further, model estimates and performance for different route choice specifications are examined for both path set compositions. Results suggest that the proposed branch-and-bound algorithm generates realistic and heterogeneous routes, reproduces better the observed behavior of the interviewed drivers, and produces a good choice set for route choice model estimation and performance comparison.

Applying Branch-and-Bound Technique to Route Choice Set Generation

An algorithm to solve explicitly the path enumeration problem is proposed. This algorithm is based on the branch-and-bound technique and belongs to the class of deterministic methods along with existing approaches that combine heuristic or randomization procedures with shortest-path search. The branch-and-bound algorithm is formulated, and a methodology is designed for the application of deterministic approaches to a real case study. Path sets generated with different methods are compared for behavioral consistency, namely, the ability to reproduce actual routes chosen by individuals driving habitually from home to work. Choice set compositions for modeling purposes are determined for the consistency of the path generation process with the observed behavior. Further, model estimates and performance for different route choice specifications are examined for both path set compositions. Results suggest that the proposed branch-and-bound algorithm generates realistic and heterogeneous routes, reproduces better the observed behavior of the interviewed drivers, and produces a good choice set for route choice model estimation and performance comparison.

The implementation of adaptive isoplanar tool path generation for the machining of free-form surfaces

Machining of steep regions is an important research topic in the machining of free-form surfaces. A new tool path generation algorithm to adaptively machine free-form surfaces has been recently developed. However, similarly to many newly emerged methods, so far it has not been used in industry because no commercial platform is currently available and the user-developed system is not robust enough for industrial applications. To solve this problem, this paper presents a new implementation method by integrating it in a commercial CAD/CAM system (Pro/Engineer). With this strategy, other than conducts detailed computations for parameters, such as scallop heights and forward steps, or designing the non-cutting functions such as engaging and retracting methods, which are routines in every tool path generation process, the implementation utilizes existing tool path generation templates in Pro/E to generate the required tool paths. This makes the tool path generation process easier and the tool paths generated more practicable because the integration is relieved of the time-consuming routine calculation and the entire cutting and non-cutting functions in the commercial system are transparent to users. Based on the API of Pro/E, the new tool path generation method was successfully implemented and cutting tests were conducted. Not losing generality, the implementation could also be conducted in other commercial systems as similar templates are available in these systems as well.

Laser scanning path generation considering photopolymer solidification in micro-stereolithography

It is essential to automate the scanning path generation process to effectively implement the micro-stereolithography. However, a scanning path that is generated based only on a 3D CAD model introduces dimensional inaccuracies. In micro-stereolithography, the photopolymer solidification is affected by fabrication conditions, such as the optical properties (laser power, laser scanning speed, laser scanning pitch focusing condition, etc.) and material properties of the photopolymer. Thus, the photopolymer solidification phenomena must be considered when generating a laser scanning path. In this paper, a scanning path generation algorithm that uses 3D CAD data and considers the photopolymer solidification phenomena is proposed to improve the dimensional accuracy in micro-stereolithography. Multi-line photopolymer solidification experiments were performed for various laser scanning conditions to examine the photopolymer solidification phenomena. From these experiments, linear relations between the solidification length (width) and scanning length (width) were acquired and stored in a database. Subsequently, these data were utilized to compensate the scanning path of the laser beam. In addition, experiments for determining the layer thickness in the z-direction were performed and these results were also used in the scanning path generation algorithm.

Systematic Approach to Contour-Parallel Tool Path Generation of 2.5-D Pocket with Islands

AbstractIn this study, the systematic integration of a complicated tool path generation process is performed. As a key concept, the Offset Loop Entity (OLE) is devised to be the unique object of every procedure. Upon the OLE approach, the tool path generation proceeds hierarchically on classified levels being engaged by the devised process flow. Throughout the entire path generation process, the procedure is conserved upon various pocketing conditions. The OLE is shifting from an offset curve segment, to an offset loop, to multiple offset loops, then to tool trajectory loops. The OLE enables the proposed approach to possess three distinctive features: simplicity, applicability, and robustness. The prototype system is implemented and evaluated with actual pocket machining. The results verify that the devised method is robust enough to achieve the optimal tool path under any pocket configuration with no burden treating specific occasions.