Control of the Underactuated Inertia Wheel Inverted Pendulum for Stable Limit Cycle Generation

This paper deals with a control approach dedicated to stable limit cycle generation for underactuated mechanical systems. The proposed approach is based on partial nonlinear feedback linearization and dynamic control for optimal periodic reference trajectories tracking. The computation of the reference trajectories is performed in order to optimize the behavior of the whole dynamics of the system and especially its zero dynamics at the end of each cycle. Simulation results as well as experiments show the performance and the efficiency of the proposed control scheme.     

Management Issues of a Mobile Agent-Based Service Environment

This paper introduces the concepts of a servicemanagement system for mobile agent-based services. Incontrast to several other approaches in whichagent-based applications are used to handletraditional network or service managementaspects, this paper describes a way to manage thedistributed agent environment itself. The proposedapproach was designed and developed by using OSI SystemsManagement concepts as a starting point, which are modified andadjusted in order to fulfill the new requirementsassociated with the mobile agent paradigm. However, thispaper does not cover integration or co-existence of the introduced agent management system (AMS)and traditional OSI management systems. Instead, theentire AMS environment is based on mobile agenttechnology. At present, this approach is validated inthe context of the European research project MobileAgent Environments in Intelligent Networks(MARINE).     

Acquisition of a symbolic manipulation task model by attention point analysis

As a way of automatic programming of robot behavior, a method for building a symbolic manipulation task model from a demonstration is proposed. The feature of this model is that it explicitly stores the information about the essential parts of a task, i.e. interaction between a hand and an environmental object, or interaction between a grasped object and a target object. Thus, even in different environments, this method reproduces robot motion as similar as possible to that of humans to complete the task while changing the motion during non-essential parts to adapt to the current environment. To automatically determine the essential parts, a method called attention point analysis is proposed; this method searches for the nature of a task using multiple sensors and estimates the parameters to represent the task. A humanoid robot is used to verify the reproduced robot motion based on the generated task model.     

Object Category Acquisition by Dynamic Touch

The acquisition of object categories which underlie the human lexicon is a prerequisite for domestic robots to communicate with users in a human-like manner. The theory of J. J. Gibson inspires the approach to obtain shared categories through interaction with the shared environment, where explorative behaviors of infants play the role of obtaining distinctive features of objects to shape their categories. Although several existing studies have reproduced the exploratory behaviors of infants by robots to investigate their roles in acquiring such categories, those active categorization methods utilized static touches and the recognition tended to fail by changes of contact conditions. This paper introduces another possible approach to object categorization — object category acquisition by dynamic touch. Dynamic touch (e.g., shaking) provides the agent with the information of the whole object to enable quick and robust recognition. The amplitude spectrum of auditory data which humans obtain during shaking is found to be an effective feature for identifying the object categories of differing dynamics, e.g., rigid objects, paper materials and bottles of water, even though the objects within each category vary in size, shape, amount and contact conditions. Experimental results are given to show the validity of the proposed method and future issues are discussed.     

Polymer surface modification with monofunctional groups of variable types and densities

- The retention of chemical structure and functional groups during pulsed plasma polymerization was used for producing adhesion-promoting plasma polymer layers with high concentrations of exclusively one kind of functional groups, such as OH, NH2, or COOH. The maximum content of functional groups was 31 OH using allyl alcohol, 18 NH2 using allylamine, or 24 COOH per 100 C atoms using acrylic acid. To vary the density of functional groups, chemical co-polymerization with ethylene as 'chain-extending' co-monomer, or butadiene as 'chemical crosslinker' was initiated in the pulsed plasma. The composition of these co-polymers was investigated by XPS and IR spectroscopy. The concentrations of functional groups were measured by derivatizing with fluorine-containing reagents and using XPS. A set of plasma parameters was found to be a good compromise between a high number of functional groups and complete insolubility in water, ethanol or THF,which is needed for further chemical processing. Here, these monotype-functionalized surfaces were used in metal-polymer systems as adhesion-promoting interlayers to examine the influence of type and density of functional groups on adhesion. As expected, COOH- and OH-group-terminated interlayers showed maximum peel strengths to evaporated aluminium layers. The adhesion increased linearly with the number of OH groups to a maximum at about 27 OH per 100 C atoms. Higher concentrations of OH groups did not increase the peel strength further.     

Access Protocols for Cellular High-Speed Data Services

In this contribution, novel access techniquesfor the future cellular information networks areproposed. To facilitate a fast deployment, the suggestedaccess techniques have been implemented over well-known technological platforms, namely DECT (DigitalEnhanced Cordless Telecommunications) containing aFDM/TDMA (Frequency Division Multiplex/Time DivisionMultiple Access) structure. Two situations areconsidered: i) no limits in the use of the all carriers atterminal (ideal case) and ii) maximum number ofcontiguous/simultaneous carriers at terminal (realisticcase). First, to grant a quick access channel, a random access mechanism with reservation is proposed.It is called contention-TDMA (C-TDMA). Next, in order tostudy the feasibility of better collision resolutionalgorithms for C-TDMA, a centralized approach called Centralized C-TDMA Demand Assignment(CC-TDMA-DA) has also been studied. For the ideal case,numerical results indicate that C-TDMA and CC-TDMA-DAyield similar throughput values in typical cellular scenarios. Also, CC-TDMA-DA tends to bepreferable for traffic sources with long messages andweak delay constraints, while C-TDMA performs better forbursty traffic sources with hard time requirements. Additional numerical results for the realisticcase have demonstrated that system performancedeteriorates little with respect to the ideal case interms of collisions, delays and throughputfigures.     

Performance of a Reversible Hierarchical Cellular System

In order to provide mobile worldwidecommunication services, cellular systems can be based ona multilayered, multisized cells architecturecharacterized by the use of different technologies.Satellites can cover lightly populated areas, as well asthose areas where other means cannot be used (like thesea); fixed base stations, with different transmissionpowers and thus different cell sizes, can cover relatively highly populated areas. As a result,a given area could simultaneously be served by more thanone Base Station, and the structure of such a systemmust be carefully designed. A Hierarchical Architecture(HA) scheme is a possible solution. HA is based on amultilevel cell configuration: microcells (or evenindoor picocells) cover more densely populated areas andare given the majority of the traffic load as they are able to operate with very highcapacity, while overlaying macrocells (or satellitarcells) provide a group of overflow channels.Occasionally, when microcells are not able to satisfychannel requests, the overflow channels are consumed.HA schemes are divided in two categories: ReversibleHierarchical (RH) and Non Reversible (NRH). Thedifference is given by the handover directions between cells allowed. In a RH handover, attemptsbetween macrocells and microcells occur in bothdirections. This paper compares RH and NRH schemes bymeans of an analytical model based on birth-deathprocesses. The main performance indexes and the controloverhead are shown.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

High-Order Sliding Modes for a Robot Driven by Pneumatic Artificial Rubber Muscles

It is known that classical sliding mode control generates chatter which is undesirable. One way to reduce this chatter is the use of high-order sliding mode (HOSM) control. The HOSM control techniques are applied to the first 2 d.o.f. of a robot actuated by pneumatic artificial rubber muscles (PARMs). The PARMs are arranged in opposite pairs (antagonistic configuration). The objective is to show that without the use of the equivalent control, it is still possible to control the robot by the use of HOSM and at the same time reduce the chatter. Experimental results are presented and comparison between two second-order sliding controls established.     

Robot phonotaxis in the wild: a biologically inspired approach to outdoor sound localization

Cricket phonotaxis (sound localization behavior) was implemented on an autonomous outdoor robot platform inspired by cockroach locomotion. This required the integration of a novel robot morphology (Whegs) with a biologically based auditory processing circuit and neural control system, as well as interfacing this to a new tracking device and software architecture for running robot experiments. In repeated tests, the robot is shown to be capable of tracking towards a simulated male cricket song over natural terrain. Range fractionation and gain control were added to the auditory control circuit in order to deal with the substantial change in amplitude of the signal as the robot approached the outdoor sound stimulus. We also discuss issues related to acoustic interference from motor noise, the need for a motor feedback mechanism to better regulate the drive signal and plans for future work incorporating additional sensory systems on this platform.