Experimental and Simulation-based Investigation of a Velocity Controller Extension on a Ball Screw System

The background of this contribution is the enhancement of the achievable accuracy of servo-screw-presses. Therefore, the paper is concerned with the improvement of the dynamic precision for direct driven servo axes which is still restricted by structural vibrations. For this purpose, a ball screw test rig was analyzed for which the standard cascade control structure was extended by an additional velocity feedback. This structural extension has the potential to improve the controller performance significantly due to a better damping of low frequent vibrations. Furthermore, a parametric dynamic model for the control structure was derived to investigate the effects of the controller extension. For this analysis, the influences of the used tuning factors and filters is discussed in the frequency domain based on bode plots. The results of these cognitions are transferred to the time domain and illustrated by step responses. In addition, an evaluation by the criterion of the IAE （integral of absolute error） and the Prony analysis is carried out. Finally, the results are experimentally verified at the ball screw test rig. The paper closes with the conclusions.

Automatic Commissioning and Vibration Damping of Servo Drives with Flexible Load

Commissioning of P/PI-cascade controlled servo axes with flexible load can be quite time consuming, if the step response based setup procedures are applied for the velocity controller as indicated by the automation systems manufacturers. Based on the drive frequency response, suitable rules of thumb with optimum velocity control damping performance are derived in this contribution that turned out to be very efficient in several dozen machine tool servo axis applications of different industrial partners in Switzerland and southern Germany. Anyway, single feedback loop velocity control sometimes provides insufficient damping of structural vibrations, especially for high dynamic machine tools or robots. The axis performance can be improved significantly by state space control extensions that are meanwhile available for commercial machine tool control systems. This contribution explains the state space control extension application with effective commissioning rules of thumb for typical machine tool axes as well as robot joint drives. The achievable benefit is elucidated by exemplary machine tool axes.

MATTER-ELEMENT MODELING OF PARALLEL STRUCTURE AND APPLICATION ABOUT EXTENSION PID CONTROL SYSTEM

This article describes in detail a new method via the extension predictable algorithm of the matter-element model of parallel structure tuning the parameters of the extension PID controller. In comparison with fuzzy and extension PID controllers, the proposed extension PID predictable controller shows higher control gains when system states are away from equilibrium, and retains a lower profile of control signals at the same time. Consequently, better control performance is achieved. Through the proposed tuning formula, the weighting factors of an extension-logic predictable controller can be systematically selected according to the control plant. An experimental example through industrial field data and site engineers＇ experience demonstrates the superior performance of the proposed controller over the fuzzy controller.

Connexin 30 controls the extension of astrocytic processes into the synaptic cleft through an unconventional non-channel function

Neurons and glial cells, particularly astrocytes, are the two main cell populations in the central nervous system. While it is established that brain functions primarily rely on neuronal activity, an active contribution of astrocytes to information processing is only starting to be considered. There is growing evidence that astrocytes, as part of the tripartite synapse, participate in this challenge by receiving and integrating neuronal signals and, in turn, by sending signals that target neurons[1]. The involvement of astrocytes in information processing has mainly been studied at the level of the single astrocyte, often missing the role of astrocyte networks in this process.

Cloud authorization： exploring techniques and approach towards effective access control framework

Despite the various attractive features that Cloud has to offer, the rate of Cloud migration is rather slow, pri- marily due to the serious security and privacy issues that exist in the paradigm. One of the main problems in this regard is that of authorization in the Cloud environment, which is the focus of our research. In this paper, we present a systematic analysis of the existing authorization solutions in Cloud and evaluate their effectiveness against well-established industrial standards that conform to the unique access control require- ments in the domain. Our analysis can benefit organizations by helping them decide the best authorization technique for deployment in Cloud; a case study along with simulation re- sults is also presented to illustrate the procedure of using our qualitative analysis for the selection of an appropriate tech- nique, as per Cloud consumer requirements. From the results of this evaluation, we derive the general shortcomings of the extant access control techniques that are keeping them from providing successful authorization and, therefore, widely adopted by the Cloud community. To that end, we enumer- ate the features an ideal access control mechanisms for the Cloud should have, and combine them to suggest the ultimate solution to this major security challenge - access control as a service （ACaaS） for the software as a service （SaaS） layer. We conclude that a meticulous research is needed to incorpo- rate the identified authorization features into a generic ACaaS framework that should be adequate for providing high level of extensibility and security by integrating multiple accesscontrol models.

A Cross-Domain Access Control Model Based on Trust Measurement

Based on trust measurement, a new cross-domain access control model is proposed to improve the security performance of the cross-domain access control processes. This model integrates the trust management and trusted platform measurement, defines several concepts （user trust degree, platform configuration integrity and intra/inter-domain trust degree） and calculates them with users＇ uniform identity authentication and historical access behavior analysis. Then this model expands the extensible access control markup language （XACML） model by adding inside trust manager point （ITMP） and outside trust manager point （OTMP）, and describes the architectures and workflows of ITMP and OTMP in details. The experimental results show that this model can achieve more fine-grained access control, implement dynamic authorization in a simple way, and improve the security degrees of the cross-domain access control.