Heikki N. Koivo

Contact Micromanipulation—Survey of Strategies

This paper surveys contact micromanipulation strategies that are developed to tackle the microscale-related phenomena in microassembly. Strategies are divided according to how they take account of adhesion forces. Micromanipulation refers to handling of objects that have dimensions below hundreds of micrometers with handling accuracy down to submicrometers. The line between micro- and nanomanipulation is not definite but typically the object size in nanomanipulation is considered to reach from atomic and molecular scale to hundreds of nanometers. In contact micromanipulation, the tool physically touches the manipulated objects during handling. Scaling-effect-induced adhesion forces severely complicate micromanipulation when compared to conventional macromanipulation. At microscale, the most important adhesive forces are van der Waals force, electrostatic force, and capillary force. Adhesion forces are also the reason behind the fairly low level of automation in microassembly systems. Improved success rate of micromanipulation operations requires that the special features of microscale phenomena be taken into consideration.

Sigmoid-basis nonlinear power-control algorithm for mobile radio systems

Convergence speed and distributiveness are important properties of a power-control algorithm in order to evaluate its potential for use in cellular radio systems. Most of the power-control algorithms in literature are derived from numerical linear algebra or linear control theory and, consequently, are in linear form. This paper, on the other hand, proposes a (sigmoid-basis) nonlinear power-control algorithm that is fully distributed and first order. The algorithm is obtained by discretization of the differential equation forms of the algorithm shown to be stable in the case of a feasible system. It is shown to be quadratically convergent in the neighborhood of its fixed point. We carried out computational experiments on a code-division multiple-access system. The results indicate that our algorithm significantly enhances the convergence speed of power control in an estimation error-free scenario and is more robust against estimation errors as compared with the linear distributed power-control algorithm of Foschini and Miljanic as a reference algorithm. The proposed algorithm was also verified with an advanced dynamic system simulator.

Multiobjective Distributed Power Control Algorithm for CDMA Wireless Communication Systems

Although power control has been explored since the early 1990s, there still remains the need for further research. Most of the algorithms so far consider either the problem of minimizing the sum of transmitted power under quality of service (QoS) constraints given in terms of minimum signal-to-interference-plus-noise ratio (SINR) in a static channel or the problem of mitigating fast fading in a single dynamic link. In this paper, we suggest a new approach to the power control by treating the QoS requirement as another objective for the power control and a fully distributed method for solving the multiobjective power optimization problem. The obtained solution is parameterized so that a tradeoff can be made between power consumption and QoS. In the limit case, when only QoS is weighted, the algorithm reduces to the well-known distributed power control algorithm (IEEE Trans. Commun., vol. 42, no. 2/3/4, pt. 1, Feb./Mar./Apr. 1994). In the other limit, the algorithm reduces to transmission with fixed minimum power. The convergence properties of the proposed algorithm are studied both theoretically and with numerical simulations. Although we only consider SINR and power sum, our algorithm could be easily modified to take other objectives, such as throughput, into account

Localization Services for Online Common Operational Picture and Situation Awareness

Many operations, be they military, police, rescue, or other field operations, require localization services and online situation awareness to make them effective. Questions such as how many people are inside a building and their locations are essential. In this paper, an online localization and situation awareness system is presented, called Mobile Urban Situation Awareness System (MUSAS), for gathering and maintaining localization information, to form a common operational picture. The MUSAS provides multiple localization services, as well as visualization of other sensor data, in a common frame of reference. The information and common operational picture of the system is conveyed to all parties involved in the operation, the field team, and people in the command post. In this paper, a general system architecture for enabling localization based situation awareness is designed and the MUSAS system solution is presented. The developed subsystem components and forming of the common operational picture are summarized, and the future potential of the system for various scenarios is discussed. In the demonstration, the MUSAS is deployed to an unknown building, in an ad hoc fashion, to provide situation awareness in an urban indoor military operation.

Applications of Multi-Objective Optimization Techniques in Radio Resource Scheduling of Cellular Communication Systems

Novel objectives such as very low outage, high capacity, and high throughput are major challenging problems in radio resource management of mobile communication systems. More specifically, in radio resource scheduling (RRS), the aim is how to optimize available resources such as transmission power and data rate to achieve certain targeted objectives. Conventional RRS algorithms are based on optimizing one objective while keeping others as constraints. This paper proposes a novel distributed RRS algorithm based on analytic multi-objective optimization. The proposed algorithm relaxes the constraints and jointly optimizes all the required objectives. Infinity set of optimal solutions, called Pareto optimal, is obtained. Each solution in the set is optimal in a specific sense. The decision maker selects the required solution that fulfills the network requirements and conditions. Some of the conventional RRS algorithms are special cases of our multi-objective based algorithm. Detailed mathematical analysis of the proposed algorithm is given. Simulation results show the behavior of the proposed algorithm as well as its advantages over conventional algorithms.

Structural Health Monitoring in Wireless Sensor Networks by the Embedded Goertzel Algorithm

Structural health monitoring aims to provide an accurate diagnosis of the condition of civil infrastructures during their life-span by analyzing data collected by sensors. To this purpose, detection and localization of damages are fundamental tasks. This paper introduces a wireless sensor network for structural damage detection and localization in which the sensor nodes, in order to estimate the energies of specific frequency bands, process the acceleration data locally in real-time using the Goertzel algorithm. The nodes then share their results inside the network and exploit them to compute transmissibility functions, which can be exploited as damage indicators and for correctly localizing damages within the monitored structure. The use of the embedded Goertzel algorithm prevents the nodes from transmitting large volumes of acceleration data to the sink node for off-line analysis, reducing the latency and increasing the life time of the cyber-physical system by 80 % and 52 %, respectively. The tests performed on a truss structure confirm the capability of the distributed approach in correctly detecting and localizing structural damages.

Proportional power control algorithm for time varying link gains in cellular radio systems

Thus far, most of the power control (PC) algorithms derived from numerical algebra envisage a system where the link gains are fixed, and the PC command can take any value in the real field. These two assumptions are quite unrealistic in actual communication systems, since link gains are time varying and PC commands must be sent over capacity limited channels. Most of the power control algorithms derived from control theory, on the other hand, analyze the PC problem from the point of view of one link. In this paper, we propose a fully distributed and nonlinearly proportional PC algorithm for time-varying link gain environments that can possibly be implemented also as a 1-bit increase/decrease PC command, and analyze it from system point of view. We construct a simple direct bridge between the link gain changes and the parameters of the proposed algorithm. It is shown that the proposed algorithm drives the carrier-to-interference+noise+ratio (CIR) to an interval in time-changing link gain environments. Simulation results for urban speeds show that the proposed algorithm is more robust against link gain changes as compared to the linear distributed PC algorithm of Foschini and Miljanic as a reference algorithm. The proposed algorithm was also verified with an advanced dynamic system simulator.

Simulating adhesion forces between arbitrarily shaped objects in micro/nano-handling operations

This paper describes a numerical method for estimating adhesion forces that are present in different microworld handling operations under a scanning electron microscope (SEM). Emphasis is put on the calculation of van der Waals force, although the results can be generalized in a straightforward manner to cover also electrostatic force. The interacting objects can have arbitrary shapes and arbitrary alignments relative to each other. Using surface formulation instead of volume formulation the accuracy of the estimation is enhanced and the computational complexity is reduced. Surface formulation also enables the division of the surfaces into separate regions. This guarantees better accuracy in the computations and makes it possible to use only part of the surfaces in the force computations.

Variable structure power control algorithm in mobile radio systems

In this paper, we apply well-known variable structure systems control theory to power control problem in mobile radio systems. The aim is to make the power control operation insensitive to unknown changes in the link gains. Some of well-known distributed power control algorithms (Foschini and Miljanic algorithm, fixed step, etc) are obtained as special cases of the proposed algorithm. Simulation results suggest that the proposed algorithm is relatively fast and robust. The algorithm is also verified with an advanced dynamic system simulator

Evaluation of adhesion forces between arbitrary objects for micromanipulation

This paper describes a numerical method to estimate adhesion forces that are present in different handling operations in the micro- and nanoworld. Emphasis is on the calculation of the van der Waals force, although the results can be generalized in a straightforward manner to also cover the electrostatic force. The presented method enables force calculation between objects that have arbitrary shapes and material properties together with arbitrary alignments relative to each other. The estimation accuracy is enhanced and the computational complexity is reduced by using surface formulation of the force instead of conventional volume formulation. The surface formulation also enables division of the surfaces into separate regions. This guarantees better accuracy in the computations and makes it possible to use only partial surfaces in the force evaluation.