Additive manufacturing of metallic components – Process, structure and properties

http://cats-fs.rpi.edu/~wenj/ECSE446S06/astrom_friction.pdf

Friction Models and Friction Compensation

: This thesis applies neural network feature selection techniques to multivariate time series data to improve prediction of a target time series. Two approaches to feature selection are used. First, a subset enumeration method is used to determine which financial indicators are most useful for aiding in prediction of the S&P 500 futures daily price. The candidate indicators evaluated include RSI, Stochastics and several moving averages. Results indicate that the Stochastics and RSI indicators result in better prediction results than the moving averages. The second approach to feature selection is calculation of individual saliency metrics. A new decision boundary-based individual saliency metric, and a classifier independent saliency metric are developed and tested. Ruck's saliency metric, the decision boundary based saliency metric, and the classifier independent saliency metric are compared for a data set consisting of the RSI and Stochastics indicators as well as delayed closing price values. The decision based metric and the Ruck metric results are similar, but the classifier independent metric agrees with neither of the other metrics. The nine most salient features, determined by the decision boundary based metric, are used to train a neural network and the results are presented and compared to other published results. (AN)

/pdf/nonlinear-time-series-analysis-1j3a35n4y3.pdf

Nonlinear Time Series Analysis.

Past, present and future of nonlinear system identification in structural dynamics

This review comprises a detailed survey of ongoing methodologies for soft actuators, highlighting approaches suitable for nanometer- to centimeter-scale robotic applications. Soft robots present a special design challenge in that their actuation and sensing mechanisms are often highly integrated with the robot body and overall functionality. When less than a centimeter, they belong to an even more special subcategory of robots or devices, in that they often lack on-board power, sensing, computation, and control. Soft, active materials are particularly well suited for this task, with a wide range of stimulants and a number of impressive examples, demonstrating large deformations, high motion complexities, and varied multifunctionality. Recent research includes both the development of new materials and composites, as well as novel implementations leveraging the unique properties of soft materials.

Soft Actuators for Small-Scale Robotics.

An integrated friction model structure with improved presliding behaviour for accurate friction compensation

Presents a dynamical friction model structure which allows accurate modeling both in the sliding and the presliding regimes. Transition between these two regimes is accomplished without a switching function. The model incorporates a hysteresis function with nonlocal memory and arbitrary transition curves. These last aspects prove essential for modeling presliding friction that is encountered in real physical situations. The model as a whole can also handle the Stribeck effect and stick-slip behavior as has been demonstrated by validation on a KUKA IR 361 robot. In this sense, this model can be considered as more complete in comparison with others found in the literature. The general friction model allows modeling of individual friction systems through the identification of a set of parameters that determine the complete behavior of the system. In this way, the model structure has been used to identify the friction behavior of a linear slide as well as that of the above mentioned KUKA robot. The results of the latter identification have been consequently used for feedforward friction compensation to obtain the most accurate tracking.

/pdf/an-integrated-friction-model-structure-with-improved-2sr9uw8hq5.pdf

An integrated friction model structure with improved presliding behavior for accurate friction compensation

A novel, multistate friction model is presented, which is obtained from the Maxwell-slip model by replacing the usual Coulomb law at slip by a rate-state law. The form of the latter state equations is arrived at by comparison with a recently developed generic friction model as well as limiting behavior cases. The model is particularly suitable for quick simulation and control purposes, being both easy to implement and of high fidelity. This communication situates the model, by outlining its development background and structure, and highlights its basic characteristics.

The generalized Maxwell-slip model: a novel model for friction Simulation and compensation

This note presents a modification of the integrated friction model structure proposed by Swevers et al. (2000), called the Leuven model. The Leuven model structure allows accurate modeling both in the presliding and the sliding regimes without the use of a switching function. The model incorporates a hysteresis function with nonlocal memory and arbitrary transition curves. This note presents two modifications of the Leuven model. A first modification overcomes a recently detected shortcoming of the original Leuven model: a discontinuity in the friction force which occurs during certain transitions in presliding. A second modification, using the general Maxwell slip model to implement the hysteresis force, eliminates the problem of stack overflow, which can occur with the implementation of the hysteresis force.

Farid Al-Bender

Papers

An integrated friction model structure with improved presliding behaviour for accurate friction compensation

An integrated friction model structure with improved presliding behavior for accurate friction compensation

The generalized Maxwell-slip model: a novel model for friction Simulation and compensation

Technical Note: modification of the Leuven integrated friction model structure

Modification of the Leuven integrated friction model structure