Dynamic Collision Detection Using Swept Solids

1986 ◽  
Vol 108 (4) ◽  
pp. 549-555 ◽  
Author(s):  
M. A. Ganter ◽  
J. J. Uicker

The detection of collisions in an environment composed of two three-dimensional bodies traversing independent general three-dimensional trajectories is accomplished through the use of swept solids and solid modeling techniques. A swept solid represents the space volumetrically swept out by the motion of a given body along a given trajectory. A swept solid is created for each of the bodies in the given environment. Using the swept solids created for each body, calculations (solid modeling boolean intersections) can be performed to determine if these swept solids intersect. If the original bodies will collide while traversing their given trajectories, then their swept solids will statically interfere. Further, an object comprising the volume of the intersection can be created if the bodies do, in fact, interfere. This object can be thought of as the “volume of interference.” Enhancements to this technique provide for the formation of swept solids using relative motion. Through these enhancements, only one swept solid need be created since the absolute motions can be converted to motion of one body relative to another body. Therefore, intersection calculations may be performed between one relative swept solid and the original body.

Perception ◽  
1993 ◽  
Vol 22 (12) ◽  
pp. 1441-1465 ◽  
Author(s):  
Jeffrey C Liter ◽  
Myron L Braunstein ◽  
Donald D Hoffman

Five experiments were conducted to examine constraints used to interpret structure-from-motion displays. Theoretically, two orthographic views of four or more points in rigid motion yield a one-parameter family of rigid three-dimensional (3-D) interpretations. Additional views yield a unique rigid interpretation. Subjects viewed two-view and thirty-view displays of five-point objects in apparent motion. The subjects selected the best 3-D interpretation from a set of 89 compatible alternatives (experiments 1–3) or judged depth directly (experiment 4). In both cases the judged depth increased when relative image motion increased, even when the increased motion was due to increased simulation rotation. Subjects also judged rotation to be greater when either simulated depth or simulated rotation increased (experiment 4). The results are consistent with a heuristic analysis in which perceived depth is determined by relative motion.


1993 ◽  
Vol 115 (1) ◽  
pp. 121-127 ◽  
Author(s):  
E. Bonataki ◽  
P. Chaviaropoulos ◽  
K. D. Papailiou

The calculation of the blade shape, when the desired velocity distribution is imposed, has been the object of numerous investigations in the past. The object of this paper is to present a new method suitable for the design of turbomachinery stator and rotor blade sections, lying on an arbitrary axisymmetric stream-surface with varying streamtube width. The flow is considered irrotational in the absolute frame of reference and compressible. The given data are the streamtube geometry, the number of blades, the inlet flow conditions and the suction and pressure side velocity distributions as functions of the normalized arc-length. The output of the computation is the blade shape that satisfies the above data. The method solves an elliptic type partial differential equation for the velocity modulus with Dirichlet and periodic type boundary conditions on the (potential function, stream function)-plane (Φ, Ψ). The flow angle field is subsequently calculated solving an ordinary differential equation along the iso-Φ or iso-Ψ lines. The blade coordinates are, finally, computed by numerical integration. A set of closure conditions has been developed and discussed in the paper. The method is validated on several test cases and a discussion is held concerning its application and limitations.


Author(s):  
Liu Dian-Kui ◽  
Ji Le-Jian

The flow within a centrifugal rotor has strong characteristics of three-dimensional effect. A procedure called “stream-surface coordinates iteration” for the calculation of complete three dimensional flow in turbo-machinery is first described. Splitter blade techniques have been used in many rotors, especially in centrifugal compressors and pumps with high flow capacity. The difficulty of the calculation of the flow field for this type of rotor lies on that the mass flow ratio between the two sub-channels is unknown for the given total flow capacity. In the second part of this paper, an assumption about how to determine this mass flow ratio and a procedure to calculate the complete three-dimensional flow are presented. Finally, some design criteria about the splitter blades are put forward. Experimental data from two centrifugal pump impellers equipped with different splitter blades are also given to demonstrate the availability of the present calculation method.


2017 ◽  
Vol 38 (2) ◽  
pp. 808-816 ◽  
Author(s):  
Salam Rahmatalla ◽  
Jonathan DeShaw ◽  
Khalid Barazanji

This work investigates the effect of the contact surfaces on the biomechanical response of supine humans during whole-body vibration and shocks. Twelve participants were exposed to three-dimensional random vibration and shocks and were tested with two types of contact surfaces: (i) litter only, and (ii) litter with spinal board. The two configurations were tested with and without body straps to secure the supine human. The addition of the spinal board reduced the involuntary motion of the supine humans in most directions. There were significant reductions in the relative vertical accelerations at the neck and torso areas, especially during shocks ( p < 0.01). The inclusion of body straps with the spinal board was more effective in reducing the relative motion in most directions when shocks were presented. This study shows that the ergonomic design of the human transport system and the underlying contacting surfaces should be studied during dynamic transport environments.


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