1,355,969 research outputs found
A local-local planning algorithm for rolling objects
No full textIn this paper, we consider planning motions of objects of regular shape rolling on a plane among obstacles. Theoretical foundations and applications of this type of operations in robotic manipulation and locomotion have been discussed elsewhere. In this paper, we propose a novel algorithm that improves upon existing techniques in that: i) it is finitely computable and predictable (an upper bound on the computations necessary to reach a given goal within a tolerance can be given), and ii) it possesses a topological (local-local) property which enables obstacles and workspace limitations to be dealt with in an effective way
A Real-time Parametric Stiffness Observer for VSA devices
No full textWe consider the problem of estimating non-linear time-varying stiffness of a mechanical system based only on force and position measurements. A recent work presented a non-parametric stiffness observer, which converges to within an Uniformly Ultimately Bounded neighborhood of the real stiffness value. The method provides excellent results for applications where the system is persistently excited. In this paper, we provide a parametric identification method that complements the previous solution in that it can provide, after a sufficiently long learning period, a complete model of the nonlinear stiffness, which can be applied henceforth even in the absence of excitation. Convergence conditions for the proposed method are discussed. Simulation and experimental results are provided, illustrating the performance of the proposed algorithm
Decentralized Variable Structure Tracking for Systems with Time-Domain Dominance
No full textIn this paper, we consider the design of tracking controllers for linear MIMO systems described by an input-output model. The presence of known 'weak' interactions among SISO or MIMO subsystems may allow the designer to achieve objectives by using independent controllers of lower complexity than are necessary in general (control decentralization problem). Sufficient conditions for asymptotic tracking employing decentralized variable structure techniques are derived. The condition is shown to be closely related to (and in a sense, a time-domain counterpart of) dominance criteria used in frequency-domain techniques, as they have developed out of Rosenbrock's original diagonal dominance concept. The synthesis of a decentralized variable-structure controller for asymptotic tracking is illustrated for systems obeying some conditions on their nominal relative degrees
Dynamic Force/Torque Sensors: Theory and Experiment
No full textAlthough present-day force/torque (F/T) sensors are mostly designed and used as if they were quasi-static devices, if significant compliance and/or stringent requirements on measurements bandwidth are in order, a dynamic analysis of such sensors is necessary. In this paper we consider the optimal (in a worst-case sense) design of F/T sensors, based on distributed-parameter models of its compliance, and algorithms that can be used to obtain F/T measurements in real time with high bandwidth. Theoretical expectations are confirmed by experimental results
Toward a Society of Robots: Behavior, Misbehavior, and Security
No full textIn this article, we consider how a very large numbers of robots, differing in their bodies, sensing, and intelligence, may be made to coexist, communicate, and compete fairly toward achieving their individual goals, i.e., to build a society of robots. We discuss some characteristics that the rules defining acceptable social behaviors should possess. We consider threats that may be posed to such a society by the misbehaviors of some of its members, either due to faults or malice, and the possibility to detect and isolate them through cooperation of peers. The article presents examples of motion control protocols, for arbitrarily large groups of heterogeneous robots. We discuss intrusion detection algorithms, which allow detection of deviance from such rules, and algorithms to build a consensus view on the environment and on the integrity of peers, so as to improve the overall security of the society of robots.In this article, we consider how a very large numbers of robots, differing in their bodies, sensing, and intelligence, may be made to coexist, communicate, and compete fairly toward achieving their individual goals, i.e., to build a society of I robots. We discuss some characteristics that the rules defining acceptable social behaviors should possess. We consider threats that may be posed to such a society by the misbehaviors of some of its members, either due to faults or malice, and the possibility to detect and isolate them through cooperation of peers. The article presents examples of motion control protocols, for arbitrarily large groups of heterogeneous robots. We discuss intrusion detection algorithms, which allow detection of deviance from such rules, and algorithms to build a consensus view on the environment and on the integrity of peers, so as to improve the overall security of the society of robots
On the Robust Synthesis of Logical Consensus Algorithms for Distributed Intrusion Detection
No full textWe introduce a novel consensus mechanism by which the agents of a network can reach an agreement on the value of a shared logical vector function depending on binary input events. Based on results on the convergence of finite--state iteration systems, we provide a technique to design logical consensus systems that minimize the number of messages to be exchanged and the number of steps before consensus is reached, and that can tolerate a bounded number of failed or malicious agents. We provide sufficient joint conditions on the input visibility and the communication topology for the method's applicability. We describe the application of our method to two distributed network intrusion detection problems
Rolling Contacts and Dextrous Manipulation
No full textIn this paper we consider a particular technique for achieving dexterity in manipulation with robot hands, which intentionally exploits rolling contacts. We report in some detail on modelling rolling contacts, and provide a result on the analysis of controllability of rolling pairs of bodies, which serves as a theoretical basis for the exploitation of rolling for dexterity enhancement. We conclude by illustrating some aspects of the problem that could not be touched upon in the paper, and open problems that still remain to be solve
On the Robust Synthesis of Logical Consensus Algorithms for Distributed Intrusion Detection
No full textWe introduce a novel consensus mechanism by which the agents of a network can reach an agreement on the value of a shared logical vector function depending on binary input events. Based on results on the convergence of finite-state iteration systems, we provide a technique to design logical consensus systems that minimizing the number of messages to be exchanged and the number of steps before consensus is reached, and tolerating a bounded number of failed or malicious agents. We provide sufficient joint conditions on the input visibility and the communication topology for the method’s applicability. We describe the application of our method to two distributed network intrusion detection problems
Rolling Bodies with Regular Surface: Controllability Theory and Applications
No full textPairs of bodies with regular rigid surfaces rolling onto each other in space form a nonholonomic system of a rather general type, posing several interesting control problems of which not much is known. The nonholonomy of such systems can be exploited in practical devices, which is very useful in robotic applications. In order to achieve all potential benefits, a deeper understanding of these types of systems and more practical algorithms for planning and controlling their motions are necessary. In this paper, we study the controllability aspect of this problem, giving a complete description of the reachable manifold for general pairs of bodies, and a constructive controllability algorithm for planning rolling motions for dexterous robot hand
Steering Driftless Nonholonomic Systems by Control Quanta
No full textWe consider the problem of steering a class of nonholonomic systems, namely systems that are feedback equivalent to a strictly triangular form, which is considerably larger than other classes for which the steering problem, has been given closed form solutions in the literature. The proposed solution consists in the application of a finite concatenation of finite-support control actions chosen among a finite set, suitable selected in the input space, each resulting in a quantum change in the system state. The method results in a closed form algorithm which is exact up to an arbitrary toleranc
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