Dexterity in human hand is connected with the fingertip rolling ability. In this work we consider rolling motion of spherical robotic fingertips as one of the control objectives together with the set point position control and force trajectory tracking. The generation of a rolling motion trajectory is proposed and a control solution is designed which achieves prescribed transient and steady state tracking behavior. The proposed control law is structurally and computationally simple and does not utilize the dynamics of the robot model or its approximation. A simulation of a five degrees of freedom robot show excellent contact rolling performance even at cases of adverse friction conditions while alternative controllers lead to contact sliding. Experiments with a KUKA LWR4 + are performed to validate the proposed method. 相似文献
One of the biggest challenges in engineering design and manufacturing environments is the effective capture of and decoding
of tacit knowledge. Fundamental to Life Cycle Engineering is the capture of engineering information and knowledge created
at all stages of the product development process, from conceptual design through to product support and disposal. Consider
this—the amount of vital information and knowledge lost when key design personnel retire—hence the need to capture meta-cognitive
task-related strategies, particularly to support knowledge reuse and training. Many methods have been tried and tested with
the successful few found to be very time consuming and expensive to implement and carry out; consequently, there is a need
to investigate alternative paradigms for knowledge and information capture. This paper reports on a current industrial case
study on knowledge capture methods employed by industrial partners in the design and manufacture of a variety of electro-mechanical
products. The results suggest the need for new kinds and forms of knowledge capture methods and representation, particularly
those associated with individual design engineering tasks. Following the findings, the paper presents a knowledge capture
methodology for automatic real-time logging, capture and post-processing of design data from a virtual reality design system.
Task-based design experiments were carried out with industrial partners to demonstrate the effective, unobtrusive and automatic
capture and representation of various forms of design knowledge and information. Qualitative and quantitative evaluation of
knowledge representations were also performed to determine which method was most effective at conveying design knowledge and
information for other engineers. 相似文献
Sea lamprey, Petromyzon marinus, rely heavily on chemical cues that mediate their life history events, such as migration and reproduction. Here, we describe petromyzone A–C (1–3), three novel bile alcohols that are highly oxidized and sulfated, isolated from water conditioned with spermiated male sea lamprey. Structures of these compounds were unequivocally established by spectroscopic analyses and by comparison with spectra of known compounds. Electro-olfactogram recordings showed that 1 at 10?11 M was stimulatory to the adult sea lamprey olfactory epithelium, while 2 and 3 were stimulatory at 10?13 M. Behavioral assays indicated that 1 is attractive, 2 is not attractive or repulsive, and 3 is repulsive to ovulated female sea lamprey. The results suggest that 1 and 2 may be putative pheromones that mediate chemical communication in sea lamprey. The identification of these three components enhances our understanding of the structures and functions of sex pheromone components in this species and may provide useful behavioral manipulation tools for the integrated management of sea lamprey, a destructive invader in the Laurentian Great Lakes. 相似文献
Multimedia Tools and Applications - Product image search aims to retrieve similar product images based on a query image. While deep learning based features work well in retrieving images of the... 相似文献
Key integrity checking is a necessary process in practical quantum key distribution (QKD) to check whether there is any error bit escaped from the previous error correction procedure. The traditional single-hash method may become a bottleneck in high-speed QKD since it has to discard all the key bits even if just one error bit exists. In this paper, we propose an improved scheme using combinatorial group testing (CGT) based on strong selective family design to verify key integrity in fine granularity and consequently improve the total efficiency of key generation after the error correction procedure. Code shortening technique and parallel computing are also applied to enhance the scheme’s flexibility and to accelerate the computation. Experimental results show that the scheme can identify the rare error bits precisely and thus avoid dropping the great majority of correct bits, while the overhead is reasonable. For a $2^{20}$-bit key, the disclosed information for public comparison is 800 bits (about 0.076 % of the key bits), reducing 256 bits when compared with the previous CGT scheme. Besides, with an Intel® quad-cores CPU at 3.40 GHz and 8 GB RAM, the computational times are 3.0 and 6.3 ms for hashing and decoding, respectively, which are reasonable in real applications and will not cause significant latency in practical QKD systems. 相似文献
This paper is using a fuzzy classification system for human reliability analysis in order to calculate the probability of erroneous actions according to CREAM in specific contexts e.g. maintenance tasks, in-field actions or control room operations in the running of a chemical plant. The complexities of such a system as well as the appropriate actions that have to be taken into consideration by the developers are analysed in detail. CREAM methodology has been selected among the most known and used methods for Human Reliability Analysis not only for being well-structured and precise, but also because it fits better in the general structure of the fuzzy logic. The first results from the application of the model are very promising and in accordance with CREAM. The numerical values produced by the model can be further used in the ‘classical’ risk assessment methods, such as event trees and fault trees, in order to calculate the overall occurrence frequency of a particular hazardous event. This is a pilot application that demonstrates the successful ‘translation’ of CREAM into a fuzzy logic model. However, the same model could be extended to cover also other industrial fields, like aviation technology and maritime transports. 相似文献
Incorporation of rigid nanoparticles is the most effective means of improving polymer properties. Montmorillonite (MMT) and multi-walled carbon nanotubes (MWCNTs) are legendary in this field for their individual exceptional properties. A synergistic phenomenon is induced between these two particles when they are simultaneously incorporated into polymers. At a definite nanofillers concentration, called the percolation threshold, there is a sudden change in nanocomposite properties due to the formation of a 3D-structured network of the nanoparticles within the matrix. In this work, the properties of poly(lactic acid) (PLA) nanocomposites filled with different fractions of MMT/MWCNTs hybrid (0.5–2.0 wt%) were analyzed. In particular, the percolation threshold of the MMT/MWCNTs hybrid was uniquely identified by differential scanning calorimetry, thermogravimetric analysis and dynamic mechanical thermal analysis. The structural studies by X-ray diffraction and Fourier-transform infrared spectroscopy were also associated with the percolation threshold of MMT/MWCNTs in PLA. At 1.0 wt% MMT/MWCNTs concentration, the complete exfoliation of the particles was maintained, and the thermal characteristics such as glass transition, crystallization and melting temperatures reached their plateau at this hybrid concentration. Moreover, the thermal degradation and viscoelastic parameters showed their peak values at this critical point, which is correlated with the formation of the percolation threshold within the matrix. The morphological studies confirmed the homogeneous dispersion of MMT/MWCNTs in PLA up to a concentration of 1.0 wt%. At 2.0 wt% MMT/MWCNTs, few aggregations occurred in the PLA-based composite, confirming that the percolation threshold was formed at a lower concentration of MMT/MWCNTs nanoparticles.
To efficiently design new adsorption systems, industrial scale fixed beds are often scaled down to bench-top experiments and/or modeled using computational fluid dynamics (CFD). While there has been considerable work exploring adsorption of volatile organics onto activated carbon fixed beds in the literature, this article attempts to reckon with the high variability of adsorption capacities observed at small scales and improve small-scale experiments for industrial scale reactor design. This study integrates experimental results with CFD simulations, which can explicitly model system heterogeneities and their influence on adsorption by resolving local packing densities and flow paths. Activated carbon physical properties were determined through surface area analysis, proximate analysis, and toluene adsorption (measured via mass spectroscopy). Variability in the small-scale systems was not attributed to surface area or carbon content, as is often stated, but instead was due to local packing density variations and the heterogeneity of particle size distributions. 相似文献