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A graphics process unit (GPU) based approach that generates collision-free and orientation-smooth tool paths for five-axis NC finishing machining of complicated shapes is presented. A new GPU-based method is proposed to compute accessibility cones of cutter location (CL) points for a ball-end cutter and tool orientations are then optimised in the accessibility cones. Three steps in the approach are GPU-based accessibility computation, feasibility map and orientation optimisation. Unlike the existing visibility concept, the diameters of both tools and tool-holders are taken into consideration and the actual accessibility cone is computed directly and efficiently based on occlusion query functionality of the graphics hardware. Next, a feasibility map is used to select feasible orientations due to the limits of collision avoidance and the machine tool. Finally, tool orientations are globally optimised to generate an orientation-smooth tool path. The proposed algorithms allow an acceptable computing time and hardware requirement to generate collision-free and orientation-smooth tool paths for complicated shapes. Examples show the efficiency of computing accessibility cones. The finishing tool paths for machining an impeller are generated as examples and cutting experiments confirm the validity of the proposed approach. [ABSTRACT FROM AUTHOR]

In this paper, a hierarchical cylinders method is proposed to resolve penetration of yarns. The performance of the hierarchical cylinders method is accelerated by applying a spatial subdivision algorithm. The spatial subdivision algorithm refines the detected regions according to the properties of weft knitted fabric, which greatly reduce the calculation of collision detection. Based on the cuboid particle system, penalty contact forces act on the yarns with problematic penetration. Experimental results demonstrate that the proposed algorithm and method are efficient for weft knitted fabric simulation. [ABSTRACT FROM AUTHOR]

The performance of virtual machine tools and virtual robot arms relies on the use of efficient and precise collision detection methods. This study proposes an octree-based collision detection method, called the ‘shared triangles extended octrees’, applied on virtual machine tools and virtual robot arms. The proposed scheme combines the high computational efficiency of the octree test and the high numerical accuracy of an analytical surface boundaries intersection test. In the proposed algorithm, the overlapping voxels between neighbouring geometries in the virtual mechanisms are identified using octrees, and the intersections of the triangles within these voxels are then checked. It works efficiently, with rapid generation of deformed geometry by shared triangles without using decomposition. The proposed collision detection scheme is implemented on virtual machine tools and the virtual robot arms in a virtual manufacturing cell. The virtual machine tools and virtual robot arms are composed of component trees, which describe the kinematic relation between components. The necessity to check for collisions between each component is indicated by a Boolean matrix. The pairs of components selected by the Boolean matrix are checked using the proposed shared triangles extended octree method. The proposed collision detection method is an efficient tool for verifying the manipulation of CNC machine tools and robot arms and is of great help to CAD/CAM engineers and manufacturing engineers and operators of machine tools and robot arms. [ABSTRACT FROM AUTHOR]

We present a stable and efficient simulator for deformable objects with collisions and contacts. For stability, an optimization derived from the implicit time integrator is solved in each timestep under the inequality constraints coming from collisions. To achieve fast convergence, we extend the MPRGP based solver from handling box constraints only to handling general linear constraints and prove its convergence. This generalization introduces a cost of solving dense linear systems in each step, but these systems can be reduced into diagonal ones for efficiency without affecting the general stability via pruning redundant collisions. Our solver is an order of magnitude faster, especially for elastic objects under large deformation compared with iterative constraint anticipation method (ICA), a typical method for stability. The efficiency, robustness and stability are further verified by our results. [ABSTRACT FROM AUTHOR]

This paper presents a numerical model developed specifically for ultrasonic shot peening (USP). It allows simulating the shot dynamics (trajectories in the chamber and impacts on the peened sample) in industrial configurations. The model supports complex 3D geometries, rotating parts and employs efficient collision detection algorithms for short computation times. The aim is to improve peening chamber designs and the choice of process parameters. The algorithm and main assumptions are presented. Numerical studies are then conducted to determine the performances of the model, in terms of computation time. Finally, a case study on a spur gear tests the model in an industrial configuration and shows a high correlation between the numerical results and experimental data. [ABSTRACT FROM AUTHOR]

The triangle-to-triangle intersection test is the most basic component of collision detection. And our algorithm, which firstly computes the line segment between triangle A and the plane of triangle B and uses a new method to detect the intersection between this line and triangle B, can reduce about 10% of time on average, compared with the previous fastest algorithm. Our new method divides the plane of triangle B into four quarter planes by two edges of B, and detects intersection depending on the location of the two endpoints of the segment. After using some techniques like avoiding division and projecting the segment and triangle B on XY, YZ, or ZX plane, the total number of arithmetic operations is reduced to at most 87, which is less than any existing algorithms. [ABSTRACT FROM AUTHOR]

Recently a lot of research effort has been focused on Wireless Sensor Networks (WSNs) due to their various applications. Over the last few years, several techniques have been proposed for investigating the power consumption which represents one of the most challenges and main concerns in designing WSNs. Power consumption of nodes in WSNs has a great effect on the lifetime of network nodes which are difficult to replace or recharge. In this context, this paper represents a receiver approach for alleviating power consumption of WSNs. Unlike other power consumption techniques, instead of decoding every received signal at the receiver which consume too much power our approach studies the histograms of the transmitted signals from sensors in order to detect collisions, so the receiver can determine when the transmitted signals can be decoded without wasting precious power decoding transmitted signals suffering from collisions. Based on a set of algorithm metrics, thresholds and scenarios, our approach shows reduction in power consumption. We use MATLAB to show our power consumption performance gains. [ABSTRACT FROM AUTHOR]

Abstract: Five-axis CNC machine tools are more and more popular in machining area, because of their ability to machine parts with complex geometries efficiently as well as achieve higher dimensional accuracy. Since two additional rotational axes are introduced in five-axis machines, there are difficult geometric problems that need to be solved in order to take full advantages of five-axis machining, and the most complex problems are collision detection and avoidance. Due to its widespread importance, a lot of researches have been carried out to solve the collision detection and avoidance problems. These include the surface properties analysis based method, convex hull based method, -space based method, accessibility based method, bounding volume and space partition method, distance calculation (vector) based method, rolling ball method, radial projection method, graphic-assisted method, and sweep plane approach. This paper aims at providing a state of the art review on algorithms for collision detection and avoidance in five-axis NC machining. In addition, a comparison of algorithms for collision detection and avoidance is considered. [Copyright &y& Elsevier]

We present a GPU-based streaming algorithm to perform high-resolution and accurate cloth simulation. We map all the components of cloth simulation pipeline, including time integration, collision detection, collision response, and velocity updating to GPU-based kernels and data structures. Our algorithm perform intra-object and inter-object collisions, handles contacts and friction, and is able to accurately simulate folds and wrinkles. We describe the streaming pipeline and address many issues in terms of obtaining high throughput on many-core GPUs. In practice, our algorithm can perform high-fidelity simulation on a cloth mesh with 2M triangles using 3GB of GPU memory. We highlight the parallel performance of our algorithm on three different generations of GPUs. On a high-end NVIDIA Tesla K20c, we observe up to two orders of magnitude performance improvement as compared to a single-threaded CPU-based algorithm, and about one order of magnitude improvement over a 16-core CPU-based parallel implementation. [ABSTRACT FROM AUTHOR]

We present a novel radial-view-based culling method for continuous self-collision detection (CSCD) of skeletal models. Our method targets closed triangular meshes used to represent the surface of a model. It can be easily integrated with bounding volume hierarchies (BVHs) and used as the first stage for culling non-colliding triangle pairs. A mesh is decomposed into clusters with respect to a set of observer primitives (i.e., observer points and line segments) on the skeleton of the mesh so that each cluster is associated with an observer primitive. One BVH is then built for each cluster. At the runtime stage, a radial view test is performed from the observer primitive of each cluster to check its collision state. Every pair of clusters is also checked for collisions. We evaluated our method on various models and compared its performance with prior methods. Experimental results show that our method reduces the number of the bounding volume overlapping tests and the number of potentially colliding triangle pairs, thereby improving the overall process of CSCD. [ABSTRACT FROM AUTHOR]

Industrial and service robots often physically interact with humans, and thus, human safety during these interactions becomes significantly important. Several solutions have been proposed to guarantee human safety, and one of the most practical, efficient solutions is the collision detection using generalized momentum and joint torque sensors. This method allows a robot to detect a collision and react to it as soon as possible to minimize the impact. However, the conventional collision detection methods cannot distinguish between intended contacts and unexpected collisions, and thus they cannot be used during certain tasks such as teaching and playback or force control. In this paper, we propose a novel collision detection algorithm which can distinguish intended contacts and unexpected collisions. In most cases, the external force during a collision shows a noticeably faster rate of change than that during an intended contact, and using this difference, the proposed observer can distinguish one from the other. Several experiments were conducted to show that the proposed algorithm can effectively distinguish intended contacts and unexpected collisions. [ABSTRACT FROM PUBLISHER]

The major contributions of this paper are as follows: (1) the Gilbert-Johnson-Keerthi (GJK) algorithm is a collisions detector algorithm, a modified Gilbert-Johnson-Keerthi algorithm is presented, the proposed GJK algorithm uses a different distance, (2) some examples of GJK algorithm are presented, in the last example, the GJK distance algorithm is used to detect the collisions of a camera with its environment inside of a warehouse, the camera cannot cross any part of the structure of the warehouse, the camera needs to go around the structure, when the camera touches the structure, the camera goes to the right or to the left, (3) the time used in a cycle of work of the transelevator robotic arm is presented, it can be extended to other kind of robotic arms, (4) some examples of the time used in a cycle of work are presented, in the least example, the algorithm is used to control the time needed for the transelevator to go from one place to other one, (5) this paper presents a new trajectory planning algorithm which divides the trajectory in n periods, when n is equal to 2, the proposed algorithm is the same as other algorithms, but for n higher than 2, the proposed algorithm gives other optional trajectories, so the proposed algorithm lets the designer to take a better trajectory than with the previous algorithms, (6) some examples of the proposed trajectories planning algorithm are presented, in the least example, the proposed trajectory planning algorithm is used to control the movements of a transelevator inside of a warehouse. [ABSTRACT FROM AUTHOR]

We present a novel trajectory computation algorithm to smooth piecewise linear collision-free trajectories computed by sample-based motion planners. Our approach uses cubic B-splines to generate trajectories that are C2 almost everywhere, except on a few isolated points. The algorithm performs local spline refinement to compute smooth, collision-free trajectories and it works well even in environments with narrow passages. We also present a fast and reliable algorithm for collision checking between a robot and the environment along the B-spline trajectories. We highlight the performance of our algorithm on complex benchmarks, including path computation for rigid and articulated models in cluttered environments. [ABSTRACT FROM PUBLISHER]

Collision detection is an important component in simulation applications which are based on virtual geographic information system (VGIS). In this paper, an effective collision detection algorithm for multiple objects in VGIS, VGIS-COLLIDE, is presented. The algorithm firstly integrates existing quadtree, which is the global hierarchical structure of VGIS, with axis-aligned bounding box of object to perform the broad-phase of collision detection. After that, exact collision detection between two objects which have passed the broad-phase of collision detection is performed. The algorithm makes no assumption about input primitives or object's motion and is directly applicable to all triangulated models. It can be applicable to both rigid and deformable objects without preprocessing. The performance of the algorithm has been demonstrated in several environments consisting of a high number of objects with hundreds of thousands of triangles. [ABSTRACT FROM AUTHOR]

Continuous Collision Detection (CCD) has been widely accepted as the common tool to detect collision between dynamic collisions of rigid and deformable models, especially for use as an accurate collision method. Performing a computationally intensive technique for detecting between two configurations that focuses on accuracy always slows detection as compared to discrete collision detection (DCD). CCD algorithms focus on the motions toward objects regarding any interpolation as long as it can be detected before it can penetrate the object. While DCD requires backtracking after collision has been detected, CCD does not suffer the same problems as DCD. CCD also avoids the tunnelling problem that exists in DCD algorithms where penetration always occurs to the object (missed the collision). This paper will provide current and future research of CCD algorithms, which eventually will become the framework of our CCD algorithm technique for our research. [ABSTRACT FROM AUTHOR]

We present an accurate and efficient algorithm for continuous collision detection between two moving ellipsoids under rational Euclidean or affine motion. We start with a highly optimized implementation of interference testing between two stationary ellipsoids based on an algebraic condition described in terms of the signs of roots of the characteristic equation of two ellipsoids. Then, we derive a time-dependent characteristic equation for two moving ellipsoids, which enables us to develop an efficient algorithm for computing the time intervals in which two moving ellipsoids collide. The effectiveness of our approach is demonstrated with practical examples. [ABSTRACT FROM AUTHOR]

A new algorithm based on the sweep plane approach for global collision detection for five-axis NC machining is presented. This algorithm takes into account not only collisions between the tool and workpiece, but also collisions between the other parts of the CNC machine, especially the change of the workpiece geometry is included in the detection process. The workpiece and machine bodies are firstly approximated by an octree of bounding spheres. Collision detection is conducted between these spheres. If there is any interference between these bounding spheres, their subspheres are further tested. The subdivision process is recursively performed until the resolution reaches the desired precision level. If there is no interference between the spheres, there is no need to subdivide any more. When the interference is detected between the spheres in the last octree level, the slices within these colliding spheres are further checked by using the sweep plane algorithm to determine whether the enclosed objects really collide with each other. In the sweep plane algorithm, most of the slices of the moving bodies stay parallel and their collisions are detected by checking the interference between these parallel slices using 2D polygon clipping. Whereas, if the slices are not parallel to the reference slicing direction (due to the rotary axes), the interference detection is conducted by examining overlaps of the projections of these slices on the three perpendicular planes , and . The accuracy of the algorithm can be adjusted by changing the distance between the sweep planes. The algorithm can be applied to any five-axis CNC machines. [Copyright &y& Elsevier]

We present a simple and efficient approach for continuous collision detection of deforming triangles based on conservative advancement. The efficiency of our approach is due to a sequence of simple collision-free conditions for deforming triangles. In our experiment, we show that our CCD algorithm achieves 2-30 times performance improvement over existing algorithms for triangle primitives. [ABSTRACT FROM PUBLISHER]