Ricardo Olanda

Towards an extensible simulator of real motion platforms

Abstract The limitations of a real motion platform will not normally be discovered until it is completely built and tested. Late identification of its limitations imposes the necessity of a redesign of the motion platform. This, in turn, incurs important and significant economic costs for the manufacturer. Note that any change in the original design of the motion platform requires an investment in resources, money and time in order to perform the re-design of the platform. The main contribution of this paper is to address this problem by creating a virtual motion platform (VMP). This virtual motion platform is a computer-based simulation of a real motion platform which produces the same outputs as the real platform when it receives the same inputs. The VMP has been designed to easily replace the real platform in order to avoid damage to the real system, avoid the potential for human injuries and reduce costs, among other advantages. The model is extensible, enabling the simulation of different kinds of real motion platforms in real-time. The VMP has been validated against a real system implementation. This prototype has been validated against two real motion platforms that we have in our labs: a T3R3 (6DoF) and a T1R2 (3DoF) platform. Extensive empirical tests have been performed and the results show that the VPM exhibits a deviation of less than 3% with respect to the real motion platform, which is a really reasonable result considering the complexity of the simulation. We have also demonstrated that our simulation is capable of running faster than real-time being able to perform batch simulations on many different design iterations.

Terrain data compression using wavelet-tiled pyramids for online 3D terrain visualization

Last years have witnessed the widespread use of online terrain visualization applications. However, the significant improvements achieved in sensing technologies have allowed an increasing size of the terrain databases. These increasing sizes represent a serious drawback when terrain data must be transmitted and rendered at interactive rates. In this paper, we propose a novel wavelet-tiled pyramid for compressing terrain data that replaces the traditional multiresolution pyramid usually used in wavelet compression schemes. The new wavelet-tiled pyramid modifies the wavelet analysis and synthesis processes, allowing an efficient transmission and reconstruction of terrain data in those applications based on multiresolution tiled pyramids. A comparative performance evaluation with the currently existing techniques shows that the proposed scheme obtains a better compression ratio of the terrain data, reducing the storage space and transmission bandwidth required, and achieving a better visual quality of the virtual terrain reconstructed after data decompression.

Motion Cueing Algorithms: A Review: Algorithms, Evaluation and Tuning

Robotic motion platforms are commonly used in motion-based vehicle simulation. However, the reproduction of realistic accelerations within a reduced workspace is a major challenge. Thus, high-level control strategies commonly referred to as motion cueing algorithms MCA are required to convert the simulated vehicle physical state into actual motion for the motion platform. This paper reviews the most important strategies for the generation of motion cues in simulators, listing the advantages and drawbacks of the different solutions. The motion cueing problem, a general scheme and the four most common approaches-classical washout, adaptive washout, optimal control and model predictive control-are presented. The existing surveys of the state-of-the-art on motion cueing are usually limited to list the MCA or to a particular vehicle application. In this work, a comprehensive vehicle-agnostic review is presented. Moreover, evaluation and tuning of MCA are also considered, classifying the different methods, and providing examples of each class.

Efficient coding of quadtree nodes

In this paper an alternative non-pointer quadtree node codification to manage geographical spatial data is presented. New codification is based on a variable sequence of z-ordered base four digits. Memory requirements of the new codification are lower than previous codifications, and in particular lower than FD codification, the most commonly used in linear quadtrees. Furthermore, z-ordering makes compatible new codification with most of the algorithms developed for FD.

Entertainment virtual reality system for simulation of spaceflights over the surface of the planet Mars

In recent years Virtual Reality technologies have enabled astronomers to recreate and explore three dimensional structures of the Universe for scientific purposes. Mars, due to its scientific interest,has been the focal point of numerous research projects using these technologies, however, none of these virtual reality tools have been developed specifically for entertainment purposes.The focus of this paper is to present MarsVR, as an entertainment research project that educates people on the topography and orography of the planet Mars from the perspective of popular science. Some projects have been designed MarsVR for entertainment purposes and include the latest advances in 3D real time applications. However, these applications have underestimated the relevant data necessary for simulating the planet Mars as an interactive virtual environment.

Visualization of Large Terrain Using Non-restricted Quadtree Triangulations

This paper presents a set of new techniques oriented towards the real-time visualization of large terrains. These techniques are mainly focused on semi-regular triangulations of non-restricted quadtree terrain representations. Despite the fact that the paper shows that triangulations based on non-restricted quadtrees are as simple and efficient as those based on restricted quadtrees, the new triangulations avoid discontinuity problems among the boundaries of different patches without the need for tree balancing and extra triangles addition. Another important feature of the proposed triangulation is that it incorporates an efficient method for building triangle strips and triangle fans for the efficient rendering of the final triangle mesh.

Improving hybrid distributed architectures for interactive terrain visualization

Interactive 3D terrain visualization plays an important role in multiple networked applications like virtual worlds visualization, multiplayer games or distributed simulators. Since the client/server architecture has obvious scalability limitations, different peer-to-peer schemes have been proposed as trade-off solutions that yield good robustness, availability and scalability for this kind of systems. In this paper, we propose a new hybrid distributed architecture that significantly improves the scalability and performance of the existing proposals. The proposed scheme redesigns the relationships between the different elements of a hybrid architecture, modifies the information shared by each client with its neighboring peers and varies the messages exchanged among them, providing a larger number of users with a fluid navigation experience over a large virtual terrain.

A new parallel pipeline for DNA methylation analysis of long reads datasets

BackgroundDNA methylation is an important mechanism of epigenetic regulation in development and disease. New generation sequencers allow genome-wide measurements of the methylation status by reading short stretches of the DNA sequence (Methyl-seq). Several software tools for methylation analysis have been proposed over recent years. However, the current trend is that the new sequencers and the ones expected for an upcoming future yield sequences of increasing length, making these software tools inefficient and obsolete.ResultsIn this paper, we propose a new software based on a strategy for methylation analysis of Methyl-seq sequencing data that requires much shorter execution times while yielding a better level of sensitivity, particularly for datasets composed of long reads. This strategy can be exported to other methylation, DNA and RNA analysis tools.ConclusionsThe developed software tool achieves execution times one order of magnitude shorter than the existing tools, while yielding equal sensitivity for short reads and even better sensitivity for long reads.

Tiling of the Wavelet Lowpass Subbands for Progressive Browsing of Images

This letter presents a new tiling scheme to achieve multiresolution and subregion image access as well as progressive retrieval, such as drill-down browsing and remote zooming/panning. This new scheme is based on the standard JPEG2000 algorithm. While JPEG2000 only divides the original image into tiles, the presented scheme divides each coarse version of the image into equal-sized tiles and reorders the wavelet coefficients in each of the steps of the analysis process. This new scheme avoids the problems associated with the traditional tiling, as used in JPEG2000, getting better lossy and lossless compression ratios, reducing disk or network latency, and improving the quality of the image

Non-interleaved quadtree node codification

The usual quadtree node non-pointer codification is based on interleaved binary representations of node coordinates, in such a way that every operation that concerns to the spatial position or to the specific orientation of the region represented by the node needs to undo this interleaving process. So, the computation time of such operations is linear with the node depth. In this paper an alternative codification is presented called “non-interleaved codification”. The new codification has a simpler management and a higher intuitiveness than current codifications that use the interleaving approach. The proposed codification is more efficient than previous ones for the following set of operations: generating the node codes from the spatial coordinates, recovering original coordinates from the node codes, and performing topological operations where explicit or implicit reference is made to node location, for instance, checking if two nodes are adjacent, evaluating distances between nodes, evaluating relative orientation, etc. The proposed codification performs all these operations in O (1) time, independently from the node depth.