Multi-attribute auctions with different types of attributes: Enacting properties in multi-attribute auctions

Multi-attribute auctions allow agents to sell and purchase goods and services taking into account more attributes than just price (e.g. service time, tolerances, qualities, etc.). In this paper we analyze attributes involved during the auction process and propose to classify them between verifiable attributes, unverifiable attributes and auctioneer provided attributes. According to this classification we present VMA2, a new Vickrey-based reverse multi-attribute auction mechanism, which takes into account the different types of attributes involved in the auction and allows the auction customization in order to suit the auctioneer needs. On the one hand, the use of auctioneer provided attributes enables the inclusion of different auction concepts, such as social welfare, trust or robustness whilst, on the other hand, the use of verifiable attributes guarantee truthful bidding. The paper exemplifies the behavior of VMA2 describing how an egalitarian allocation can be achieved. The mechanism is then tested in a simulated manufacturing environment and compared with other existing auction allocation methods.     

An interactive approach for multi-attribute auctions

Auction processes are commonly employed in many environments. With rapid advances in Internet and computing technologies, electronic auctions have become very popular. People sell and buy a wide range of goods and services online. There is a growing need for the proper management of online auctions and for providing support to parties involved. In this paper, we develop an interactive approach supporting both the buyer and the bidders in a multi-attribute, single-item, multi-round, reverse auction environment. We demonstrate the algorithm on a number of problems.     

An experimental investigation into the effects of information revelation in multi-attribute reverse auctions

Bid-takers in multi-attribute reverse auctions (MRA) are typically confronted with a myriad of information revelation options and must make decisions on which pieces of information to reveal to bidders and which ones to conceal. This study explores how the choice of different types and combinations of information can affect bidding behaviour and bidder perceptions in MRA. The results of a computer-based laboratory experiment suggest that by reducing the level of information asymmetry and using certain combinations of information a bid-taker can reduce bidder drop-out and spur the submission of high quality bids, i.e. bids that yield high levels of utility for the bid-taker.     

Computer viruses: Theory and experiments

This paper introduces “computer viruses” and examines their potential for causing widespread damage to computer systems. Basic theoretical results are presented, and the infeasibility of viral defense in large classes of systems is shown. Defensive schemes are presented and several experiments are described.     

Occlusion filling in stereo: Theory and experiments

A number of stereo matching algorithms have been developed in the last few years, which also have successfully detected occlusions in stereo images. These algorithms typically fall short of a systematic study of occlusions; they predominantly emphasize matching and regard occlusion filling as a secondary operation. Filling occlusions, however, is useful in many applications such as image-based rendering where 3D models are desired to be as complete as possible. In this paper, we study occlusions in a systematic way and propose two algorithms to fill occlusions reliably by applying statistical modeling, visibility constraints, and scene constraints. We introduce a probabilistic, model-based filling order of the occluded points to maintain consistency in filling. Furthermore, we show how an ambiguity in the interpolation of the disparity value of an occluded point can safely be avoided using color homogeneity when the point’s neighborhood consists of multiple scene surfaces. We perform a comparative study and show that statistically, the new algorithms deliver good quality results compared to existing algorithms.     

Sensor-based collision avoidance: Theory and experiments

A new on-line control strategy for sensor-based collision avoidance of manipulators and supporting experimental results are presented in this article. This control strategy is based on nullification of virtual forces applied to the end-effector by a hypothetical spring-plus-damper attached to the object's surface. In the proposed approach, the real-time arm control software continuously monitors the object distance measured by the arm-mounted proximity sensors. When this distance is less than a preset threshold, the collision avoidance control action is initiated to inhibit motion toward the object and thus prevent collision. This is accomplished by employing an outer feedback loop to perturb the end-effector nominal motion trajectory in real-time based on the sensory data. The perturbation is generated by a proportional-plus-integral (PI) collision avoidance controller acting on the difference between the sensed distance and the preset threshold. This approach is computationally very fast, requires minimal modification to the existing manipulator positioning system, and provides the manipulator with an on-line collision avoidance capability to react autonomously and intelligently. A dexterous RRC robotic arm is instrumented with infrared proximity sensors and is operated under the proposed collision avoidance strategy. Experimental results are presented to demonstrate end-effector collision avoidance both with an approaching object and while reaching inside a constricted opening. © 1996 John Wiley & Sons, Inc.     

Underactuated ship tracking control: Theory and experiments

We consider complete state tracking feedback control of a ship having two controls, namely surge force and yaw moment. The ship model has similarities with chained form systems but cannot directly be transformed in chained form. In particular, the model has a drift vector field as opposed to the drift-free chained form systems. It is shown here that methods developed for tracking control of chained form systems still can be used for developing a tracking control law for the ship. Through a coordinate transformation the model is put in a triangular-like form which makes it possible to use integrator backstepping to develop a tracking control law. The control law steers both the position variables and the course angle of the ship, providing exponential stability of the reference trajectory. Experimental results are presented where the control law is implemented for tracking control of a model of an offshore supply vessel, scale 1:70. In the experiments the ship converges exponentially to a neighbourhood of the reference trajectory, and stays close with errors depending on factors as unmodelled dynamics, parameter uncertainty, measurement noise, thruster saturation, waves, currents and position measurement failures.     

Theory and experiments in SmartNav rover navigation

This paper describes theoretical and experimental results using the SmartNav rule-free fuzzy rover navigation system. SmartNav divides the terrain perceived by the rover into a number of circular sectors, and evaluates each sector using goal and safety preference factors to differentiate between preferred and unpreferred terrain sectors. The goal-preference factor is used to make sector evaluation based on the sector orientation relative to the designated goal position. The safety-preference factors are used to make sector evaluations on the basis of the sector local and regional terrain hazards. Three methods are developed to blend the three sector evaluations in order to find the effective preference factor for each sector. Two sector selection methods are then described in which the sector preference factors are used to find the heading command for the rover. The rover speed command is also computed based on the goal distance and safety-preference factor of the chosen sector. The above navigation steps are continuously repeated throughout the rover motion. Experimental results are presented to demonstrate the navigational capabilities of SmartNav using a commercial Pioneer 2AT rover traversing a simulated Martian terrain at the JPL Mini Mars Yard.

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Adaptive tracking control of manipulators: Theory and experiments

This paper considers the trajectory tracking problem for uncertain robot manipulators and proposes two adaptive controllers as solutions to this problem. The first controller is derived under the assumption that the manipulator state is measurable, while the second strategy is developed for those applications in which only position measurements are available. The adaptive schemes are very general and computationally efficient since they do not require knowledge of either the mathematical model or the parameter values of the manipulator dynamics, and are implemented without calculation of the robot inverse dynamics or inverse kinematic transformation. It is shown that the control strategies ensure uniform boundedness of all signals in the presence of bounded disturbances, and that the ultimate size of the tracking errors can be made arbitrarily small. Experimental results are presented for a PUMA 560 manipulator and demonstrate that accurate and robust trajectory tracking can be achieved by using the proposed controllers.     

Autonomous airship path following control: Theory and experiments

A novel path following control method related to the planar and spatial motions for an underactuated autonomous airship is presented. First, the trajectory linearisation control (TLC) theory is briefly described and the dynamic model of the airship is introduced. Then, based on the model, a path following strategy that integrates the guidance-based path following principle and the TLC theory is deduced. The designed control system possesses a cascaded structure composed of a guidance loop, an attitude kinematics loop and a dynamics control loop. Stability analysis shows that the controlled closed-loop system is asymptotically stable. Finally, experimental flight results for the airship following typical paths are illustrated to verify the effectiveness of the proposed approach.     

Query optimization using restructured views: Theory and experiments

We study optimization of relational queries using materialized views, where views may be regular or restructured. In a restructured view, some data from the base table(s) are represented as metadata—that is, schema information, such as table and attribute names—or vice versa.     

Out-of-Order Execution in Sequentially Consistent Shared-Memory Systems:Theory and Experiments

Traditional implementation of sequential consistency in shared-memory systems requires memory accesses to be globally performed in program order.Based on an event ordering model for correct executions in shared-memory systems,this paper proposes and proves that out-of-order execution does not influence the correctness of an execution providing certain condition is met.Simulation results show that out-of-order execution proposed in this paper is an effective way to improve the performance of a sequentially consistent shared-memory system.     

Control of a planar space robot: Theory and experiments

In this paper the attitude control problem of planar space robot is addressed and new feedback control scheme is proposed. Since control laws are synthesized via theory of geometric phase, the proposed control laws contain smooth functions of states and time. The usefulness and validity of this control scheme can be demonstrated by hardware experiments. In experiments to simulate the space environment prototype of the planar space robot is floated by air on the horizontal plane. Experimental results show that the proposed smooth time-varying control laws stabilize the attitude of the planar space robot sufficiently.     

Output synchronization control of ship replenishment operations: Theory and experiments

A leader–follower synchronization output feedback control scheme is presented for the ship replenishment problem where only positions are measured. No mathematical model of the leader ship is required, and the control scheme relies on nonlinear observers to estimate velocity and acceleration of all ships to realize the feedback control law. The scheme yields semi-global uniform ultimate boundedness of the closed-loop errors. The bound is a function of the main ship acceleration, and under the assumption of zero main ship acceleration the closed-loop errors are semi-globally exponentially converging. The results are verified through experiments on a model-scale ship.     

Non-linear control of advanced direct drive robots: Theory and experiments

Direct drive robots are widely used to perform high precision positioning, and advanced control algorithms are applied to attain the desired performance. Small direct drive manipulators are widely used in aerospace, biotechnology, instrumentation, medicine, micro manufacturing, high-density integrated circuits and VLSI fabrication, etc. This paper studies non-linear modelling, analysis and control of direct drive robots to guarantee the desired level of performance. We are particularly interested in the physical laws to model mechanical-electromagnetic phenomena and effects, and the integration of electric motors is a key factor to design high performance direct drive robots. The non-linear mathematical model, found using the Lagrange equations of motion, is applied in non-linear analysis and design. The design method is described and validated. The design concept uses the Hamilton-Jacobi and Lyapunov theories to synthesize robust tracking controllers. It is illustrated that minimizing a non-quadratic performance functional, a bounded control law is analytically designed using necessary conditions for optimality. The sufficient conditions for robust stability are examined using the criteria imposed on positive-definite return functions. Results indicate that the reported method allows one to guarantee robust accurate tracking and disturbance attenuation. A two-degree-of-freedom prototype of direct drive manipulator is described, and the achieved performance is documented and discussed.     

Bid evaluation in combinatorial auctions: optimization and learning

In combinatorial auctions bidders can post bids on groups of items. The problem of selecting the winning bids, called Winner Determination Problem, is NP‐hard. In this paper, we consider an interesting variant of this problem, called Bid Evaluation Problem (BEP), where items are services and are subject to precedence constraints and temporal windows. The BEP has many practical applications, such as, for instance, in transportation routes auctions and in take off and landing time slot allocation problems. We have developed a number of optimization algorithms based on Constraint Programming, on Integer Programming and on the combination of the two techniques. We first show that all algorithms proposed outperform the only commercial system for solving BEP instances called Multi AGent Negotiation Testbed, a more general tool for agent negotiation. Then, we evaluate the developed algorithms and use the decision tree machine learning technique for finding a relation between the instance structure and the solving algorithm and providing an automatic algorithm selection procedure. We show that we can achieve an accuracy of 90% in predicting the best algorithm given the instance to be solved with a significant time saving w.r.t. a single solving technique or a costless, but less accurate, prediction technique. Copyright © 2009 John Wiley & Sons, Ltd.     

SM-Chord:自维护的多属性Chord

针对Chord不支持多属性查找,通过分析结构化覆盖网络Chord,提出了SM-Chord.该系统充分利用各个节点的自身性能来维护自己的资源,以资源的多个属性值构成Chord环,从而使该系统既可以支持多属性查找,又可以减少资源重新部署带来的带宽消耗.仿真试验结果表明,SM-Chord在保持Chord查找成功率的同时,能够通过负载分担提高系统的负载平衡能力,并且降低了系统的带宽消耗.     

Impact stabilizing controller for hydraulic actuators with friction: Theory and experiments

Stabilizing manipulators during the transition from free to constraint motion is an important issue in contact task control design. This paper documents the development, theoretical analysis and experimental evaluation of a Lyapunov-based control scheme to regulate the impacts of a hydraulic actuator that comes in contact with a nonmoving environment. Upon sensing a nonzero force, the controller positions the actuator at the location where the force was first sensed, exerting minimal force on the environment. The scheme does not require continuous measurement of force or velocity during the short period of impacts, making it very useful for practical cases. Furthermore, no knowledge of the impact dynamics, friction effects, servovalve dynamics, or hydraulic parameters is required for control action. Stability of the control scheme is verified via analytical analyses. Due to the discontinuous friction model and the discontinuous nature of the proposed control law, the control system is nonsmooth. The existence, continuation and uniqueness of Filippov's solution to the system are, therefore, investigated. The extension of LaSalle's invariance principle to nonsmooth systems is next employed to prove that all the solution trajectories converge to the equilibria. The controller is finally tested experimentally to verify its practicality and effectiveness in collisions with hard and soft environments and with various approach velocities.     

Periodic motions of the Pendubot via virtual holonomic constraints: Theory and experiments

This paper presents a new control strategy for an underactuated two-link robot, called the Pendubot. The goal is to create stable oscillations of the outer link of the Pendubot, which is not directly actuated. We exploit a recently proposed feedback control design strategy, based on motion planning via virtual holonomic constraints. This strategy is shown to be useful for design of regulators for achieving: stable oscillatory motions, a closed-loop-design-based swing-up, and propeller motions. The theoretical results are verified via successful experimental implementation.