Reflex movements for a virtual human: a biology inspired approach

This paper presents the results of a method to produce autonomous animation of virtual humans. In particular, the proposed methodology is focused on the autonomous synthesis of nonvoluntary gestures such as reflexes and subtle movements which provide a noticeable impression of realism and naturalness. The final goal of this technique is to produce virtual humans with a more spontaneous, non preprogrammed behaviour. For the moment, the technique is applied to the synthesis of reflex movements of the arm, in reaction to thermic stimuli. Nevertheless, a general architecture is outline

Contact and HiL interaction in multibody based machinery simulators

[Abstract] Multibody simulators allow to predict and evaluate the motion of machines and mechanisms under the action of the user and the interaction with the simulated environment. Interactive simulators guided by a human or a piece of hardware must be efficient enough to compute the state of the system in real time. ?erefore, employing fast and sufficiently accurate techniques is a must. In this work, generic tools for the implementation of this kind of simulators are provided. Efficient multibody formulations are reviewed for implementing real-time simulators. ?e index-3 Augmented Lagrange formulation with projections of velocities and accelerations is selected, due to its efficiency and stability. ?e integration of the equations of motion follows the Generalized-a method, which provides high-frequency dissipation, and can be unconditionally stable and secondorder accurate if suitable integrator parameters are chosen. Contact modeling and detection is essential for computing the interaction among the mechanisms and the simulated environment. Normal and tangential contact force models are presented. For the normal contact, a Hertz-type Hunt- Crossley model is chosen. ?e tangential force model is based on Coulomb’s law, and includes stiction and viscous friction effects. Both models were compared with the output of the Bowden-Leben stick-slip experiment. A real-time, simplified terrain model featuring digging forces for excavator simulators is also discussed. Several techniques are shown for detecting colliding bodies at run-time. ?e collision detection process is divided into two stages. ?e first one is a broad range and coarse grained process, where potentially colliding pairs of objects are discovered. Spatial and hierarchical division techniques as Octrees, BSP-trees and Directed Acyclic Graphs are presented for this purpose. In the second stage, fine-detailed contact properties are computed from each pair of bodies. Several models are presented for testing object enclosing volumes or more complex surfaces discretized as triangular meshes. State-of-the-art, Commercial Off ?e Shelf hardware devices are presented as the physical foundation of a simulator. Industrial-quality controllers, projection screens and audio devices are reviewed for this purpose. ?e implementation details for the use of those devices are also considered. Network communication procedures between the simulator and monitoring nodes are discussed, too. Finally, a particular implementation of all the techniques described in previous chapters is presented in the form of an interactive excavator simulator, which features all the degrees of freedom of the machine, and is able to perform earthmoving operations in a realistic environment. Monitoring capabilities are also available, and any training session can be defined by user scripts. ?e techniques described in this document constitute a generic and efficient compendium of algorithms that are well-fi?ed for medium or low-end computational systems, as desktop or even laptop computers

Reaching volumes generated by means of octal trees and Cartesian constraints

We present a system to analyze the reachability of the human body. The inverse kinematics technique is employed to find which regions of space are reachable using a certain reach strategy. This information is stored in a data structure called volume approximation tree (VATree). This tree has proven itself to be an appropriate data structure for two reasons: it provides an efficient representation of the reachable volumes and it reduces the number of inverse kinematics simulations necessary for its construction. Once the VATrees are constructed for the different reach strategies, that information can be used to determine in real time which strategy is most suitable for a given reach tas

Universal Design Manikin: Integrative Simulation and Visualization Techniques

This research demonstrates methods for integrating simulation and visualization techniques with the current tools used in design work-flows. The techniques are applied to human factors with a concentration on disabilities. A tool named Universal Design Manikin is developed. The tool integrates a virtual manikin and wheelchair with a coresponding graphical user interface. The research covers factors from a human scale of reach abilitiy to a large scale of building navigation. The research presents an opportunity for seamless collaboration between scientists and designers by integrating joint analysis tools with design tools. Methods for simulation and visualization of reach, vision, navigation, and spatial zones are presented.Master of ScienceArchitecture and Urban PlanningUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/95705/1/Schwartz_Masters.pd

Scalable Algorithms for Parallel Tree-based Adaptive Mesh Refinement with General Element Types

In this thesis, we develop, discuss and implement algorithms for scalable parallel tree-based adaptive mesh refinement (AMR) using space-filling curves (SFCs). We create an AMR software that works independently of the used element type, such as for example lines, triangles, tetrahedra, quadrilaterals, hexahedra, and prisms. For triangular and tetrahedral elements (simplices) with red-refinement (1:4 in 2D, 1:8 in 3D), we develop a new SFC, the tetrahedral Morton space-filling curve (TM-SFC). Its construction is similar to the Morton index for quadrilaterals/hexa- hedra, as it is also based on bitwise interleaving the coordinates of a certain vertex of the simplex, the anchor node. Additionally, we interleave with a new piece of information, the so called type. For these simplices, we develop element local algorithms such as constructing the parent, children, or face-neighbors of a simplex, and show that most of them are constant-time operations independent of the refinement level. With SFC based partitioning it is possible that the mesh elements that are parti- tioned to one process do not form a face-connected domain. We prove the following upper bounds for the number of face-connected components of segments of the TM-SFC: With a maximum refine- ment level of L, the number of face-connected components is bounded by 2(L − 1) in 2D and 2L + 1 in 3D. Additionally, we perform a numerical investigation of the distribution of lengths of SFC segments. Furthermore, we develop a new approach to partition and repartition a coarse (input) mesh among the processes. Compared to previous methods it optimizes for fine mesh load-balance and reduces the parallel communication of coarse mesh data. We discuss the coarse mesh repartitioning algorithm and demonstrate that our method repartitions a coarse mesh of 371e9 trees on 917,504 processes (405,000 trees per process) on the Juqueen supercomputer in 1.2 seconds. We develop an AMR concept that works independently of the element type; achieving this independence by strictly distinguishing between functions that oper- ate on the whole mesh (high-level) and functions that locally operate on a single element or a small set of elements (low-level). We discuss a new approach to generate and manage ghost elements that fits into our element-type independent approach. We define and describe the necessary low-level algorithms. Our main idea is the computation of tree-to-tree face-neighbors of an element via the explicit construction of the element's face as a lower dimensional element. In order to optimize the runtime of this method we enhance the algorithm with a top-down search method from Isaac, Burstedde, Wilcox, and Ghattas, and demonstrate how it speeds up the computation by factors of 10 to 20 achieving runtimes comparable to state-of-the art implementations with fixed element types. With the ghost algorithm we build a straight-forward ripple version of the 2:1 balance algorithm. This is not an optimized version but it serves as a feasibility study for our element-type independent approach. We implement all algorithms that we develop in this thesis in the new AMR library t8code. Our modular approach allows us to reuse existing software, which we demonstrate by using the library p4est for quadrilateral and hexahedral elements. In a concurrent Bachelor's thesis by David Knapp (INS, Bonn) the necessary low-level algorithms for prisms were developed. With t8code we demonstrate that we can create, adapt, (re-)partition, and balance meshes, as well as create and manage a ghost layer. In various tests we show excellent strong and weak scaling behavior of our algorithms on up to 917,504 parallel processes on the Juqueen and Mira supercomputers using up to 858e9 mesh elements. We conclude this thesis by demonstrating how an application can be coupled with the AMR routines. We implement a finite volume based advection solver using t8code and show applications with triangular, quadrilateral, tetrahedral, and hexahedral elements, as well as 2D and 3D hybrid meshes, the latter consisting of tetrahedra, hexahedra, and prisms. Overall, we develop and demonstrate a new simplicial SFC and create a fast and scalable tree-based AMR software that offers a flexibility and generality that was previously not available

Mobile Robots Navigation

Mobile robots navigation includes different interrelated activities: (i) perception, as obtaining and interpreting sensory information; (ii) exploration, as the strategy that guides the robot to select the next direction to go; (iii) mapping, involving the construction of a spatial representation by using the sensory information perceived; (iv) localization, as the strategy to estimate the robot position within the spatial map; (v) path planning, as the strategy to find a path towards a goal location being optimal or not; and (vi) path execution, where motor actions are determined and adapted to environmental changes. The book addresses those activities by integrating results from the research work of several authors all over the world. Research cases are documented in 32 chapters organized within 7 categories next described

Sonar three-dimensional image formation for underwater vehicular collision avoidance

The last ten years have shown a marked increase in research into Autonomous Underwater Vehicles. A key component of this research is the ability to “look” ahead of the vehicle\u27s projected path and translate active sonar returns into three-dimensional (3-D) computer data structures used to navigate and avoid obstacles. This need to avoid obstacles is also common to other underwater vehicles including submersibles. Of special interest to this research is the “Occupancy Grid Framework.” This technique divides the forward looking sonar field into cells. These cells can be maintained either in spherical or cartesian coordinate systems. This research demonstrates a method of maintaining an array-type data structure based on the cartesian coordinates of returned sonar echoes. A volume of array elements are colored to reflect the probability of potential obstacles. Also, between sweeps of a scanning sonar transducer array, the locations of these volumes of probability are both rotated and translated inside the data structure as the vehicle turns and/or moves forward. ard. This research is different from prior research in two respects. First, rotation and translation of target probability spheres, located in a 3-D array, are accomplished by rotating and translating the sphere centers rather than the actual voxels comprising the spheres. In this way, probability spheres are continuously being removed, and regenerated at new locations inside the data structure. This relocation can be done in real-time as the vehicle moves. Secondly, this research shows a method of pre-processing real-time data for increased speed using a series of two microcontrollers located between the sonar transceiver and the host computer, where the data is processed. Programs used in this system consist of both assembly language programs for the microcontrollers, and a C language program for the host computer. These programs demonstrate a software approach which can be used as a basis for future research