Multi-contact representation for a force-reflecting manipulating simulator: preliminary experiments

In the present work, we propose an active tactile exploration framework to obtain a surface model of an unknown object utilizing multiple contacts simultaneously. To incorporate these multiple contacts, the exploration strategy is based on the differential entropy of the underlying Gaussian process implicit surface model, which formalizes the exploration with multiple contacts within an information theoretic context and additionally allows for nonmyopic multi-step planning. In contrast to many previous approaches, the robot continuously slides along the surface with its end-effectors to gather the tactile stimuli, instead of touching it at discrete locations. This is realized by closely integrating the surface model into the compliant controller framework. Furthermore, we extend our recently proposed sliding based tactile exploration approach to handle non-convex objects. In the experiments, it is shown that multiple contacts simultaneously leads to a more efficient exploration of complex, non-convex objects, not only in terms of time, but also with respect to the total moved distance of all end-effectors. Finally, we demonstrate our methodology with a real PR2 robot that explores an object with both of its arms.

Error analysis in calculation and interpretation of AFM tip-surface interaction forces

Parallel processing system -Harray-

The aging population brings the problem of healthcare and dyskinesia. The lack of mobility extremely affects stroke patient's activities of daily living (ADL) and decreases their quality of life. To assist these mobility-limited people, a robotic walker is designed to facilitate gait rehabilitation training. The aim of this paper is to present the implementation of a novel motion control method to assist disabled people based on their motion intention. The kinematic framework of the robotic walker is outlined. We propose an intention recognition algorithm based on the interactive force signal. A novel motion control method combined with T-S fuzzy controller and PD controller is proposed. The motion controller can recognize the intention of the user through the interactive force, which allows the user to move or turn around as usual, instead of using their hands to control the walker. Preliminary experiments with healthy individuals and simulated patients are carried out to verify the effectiveness of the algorithm. The results show that the proposed motion control approach can recognize the user's intention, is easy to control and has a higher precision than the traditional proportional-integral-derivative controller. The results show that users could achieve the task with acceptable error, which indicates the potential of the proposed control method for gait training.

Feedback of the interaction force of the forceps tool within the abdominal environment can improve the performance of the surgical operation. Unfortunately, force amplitude is often too small to perceive. Moreover, the interaction force is quite complex such that it hides the essence of the important reaction force of the intended action. Yet it has been observed that the surgeon often needs to concentrate on the reaction force in specific directions, in accordance with his intended action. Automatic force feedback augmentation has been proposed to solve the stated problems. First, the forceps action is determined in real time from the force and motion pattern. The reaction force is then amplified naturally according to the identified forceps action. As a result, only the simple but significant reaction force patterns are emphasized. Complex behavior of the reaction force, which may distract or deteriorate the intended action, is attenuated. Preliminary experiments have been conducted to verify the advantages of the proposed method.

This paper describes a real-time robotic system. It runs on a heterogeneous multiprocessor system and the system communicates with the robot via RS232 link or infrared link. The multiprocessing system is a IBM personal computer and a i860 add-on card. There are several tasks required for a high performance real-time robotics system: (1) An efficient decision-making task to fulfil the real-time requirement such as supervision, coordination and local control of the robot (2) A real-time graphics task to display the robot's location and its environment (3) A real-time alerting task to alert the system software to perform efficient recovery when the robot is not in its controlling environment (4) Other nonreal-time tasks such as auditing and scheduling (5) Tasks for communication between the robot and the host. In this paper, a multiprocessing distributed system is designed such that the tasks 1 to 4 is handled on the IBM, and the graphics display system is handled by the i860 because of its extremely good graphics performance. The software and hardware design for the system to have a good real-time performance is also discussed. >

Using 1995 results from the NASA Parallel Benchmarks, this paper compares the sustained performance (as opposed to peak performance) and cost per unit of sustained performance for state-of-the-art Parallel processing systems that use Micro-Processors (MPP) versus those that use Custom-designed Processors (PVP). This comparison shows that MPPs approach, but seldom surpass, PCPs with respect to either metric. This paper also discusses the merits and demerits of “clusters” of workstation. Ironically, recently introduced low-cost, parallel systems can also be viewed as “virtual workstation clusters” that offer comparable, if not superior, capabilities. Finally, this paper explores the question of whether it will be economically feasible for computer manufacturers to continue building PVPs, or are MPPs the only economically viable option for building parallel systems?

In this research, spin-transport properties of the B24N24 molecule, when it is connected through a single and multiple atom contacts to two ferromagnetic electrodes have been investigated using the Landauer formula and the non-equilibrium Green’s function. The results show that the current has a stepwise behavior against the bias voltage; the off state of the B24N24 molecule occurs at low voltages, independent of the type of contact. The characteristic of the current in terms of the gate voltage is dependent on the contact type in usage, and generally less for single contact configurations as compared to those seen in multiple contact configurations. In the case of contacting one atom of the B24N24 molecule to electrodes, the B24N24 has conduction property, while in multiple contacts it shows property of a semiconductor. The Tunneling Magnetic Resistance (TMR) contained three peaks no matter of the contact type, and whose maxima for single and 4-atom (about 42%) and for 8-atom (about 37%) all occurred at zero bias voltage. The maxima of TMR for 6-atom arrangement went up at the bias voltages − 1.2 V and + 1.2 V, about 53%. And, last but not the least, the TMR maxima change locations as the voltage increases.

A multiprocessor system is a computer with two or more central processing units (CPUs) with each one sharing the common main memory as well as the peripherals. Multiprocessor system is either homogeneous or heterogeneous system. A homogeneous system is a cluster of processors joined to a high speed network for accomplishing the required task; also it is defined as parallel computing system. Homogeneous is a technique of parallel computing system. A heterogeneous system can be defined as the interconnection of a number of processors, having dissimilar computational speed. Load balance is a method of distributing work between the processors fairly in order to get optimal response time, resource utilization, and throughput. Load balancing is either static or dynamic. In static load balancing, work is distributed among all processors before the execution of the algorithm. In dynamic load balancing, work is distributed among all processors during execution of the algorithm. So problems arise when it cannot statistically divide the tasks among the processors. To use multiprocessor systems efficiently, several load balancing algorithms have been adopted widely. This paper proposes an efficient load balance algorithm which addresses common overheads that may decrease the efficiency of a multiprocessor system. Such overheads are synchronization, data communication, response time, and throughput.

The task of handling nonrigid one-dimensional objects by a robot manipulation system is investigated. Especially, approaches to calculate motions with specific behavior in point contacts between the object and environment are regarded. For single point contacts, motions based on generalized rotations solving the direct and inverse manipulation problem are investigated. The latter problem is additionally tackled by simple rotation and translation motions. For double and multiple point contacts, motions based on splines are suggested. In experimental results with steel springs, the predicted and measured effect for each approach are compared.

This paper proposes a parallel processing system -Harray- for scientific computations. Data flow computers are expected to obtain the high performance because they can extract parallelism fully from a program. However, they have many problems, such as the difficulty of controlling the sequence of execution. The -Harray- system is an array processor which adapts two levels of control mechanism; data flow execution in each processor and control flow between processors, in order to take full advantage of both mechanisms. A task which is assigned to a processor is called a “macro-block”. Three types of macro-blocking and three types of activation schemes for the macro-block which initiates its execution are introduced in order to attain the high performance. Moreover, a hardware synchronization mechanism is used to reduce synchronization overhead and to gain the liner speedup of the -Harray- system.In this paper, the system architecture of the -Harray- system and its performance evaluation by software simulation are presented.

This chapter reviews the existing theories of Van der Waals interactions between macroscopic bodies. An essential advantage of the microscopic approach is its simplicity, which is realized by means of the assumption of additivity of pair interactions. A large portion of the chapter deals with examination of different procedures for the determination, from spectral data, of the quantities required for the calculation of Van der Waals energies or forces of interaction, such as dielectric permeabilities or molecular polarizabilities. Common to all these terms is that the average energy and free energy of interaction are negative, i.e., attractive, and vary with the inverse sixth power of intermolecular distance. The extension of Lifshitz theory to the derivation of expressions for forces or free energies of interaction between bodies in other geometries seemed a formidable task. A knowledge of these quantities or functions thereof is required for the calculation of intermolecular forces.

In order to speedup image processing in embedded environment, we construct a parallel processing system of images. The parallel processing system includes a parallel hardware, a new defined language for parallel image processing and a set of software tools. From the view of high performance, low power dissipation and the characteristics of image processing, we construct a SIMD coprocessor as an image processing accelerator. Using a RISC host processor manages the whole system. The SIMD processor is scalable. We also define a new language which is extended from standard C. A new data type and a new keyword kernel are added to the language to explicitly describe parallelism. For the new hardware and language of parallel image processing, we also research software tools for this parallel system. The software tools maps programs to code that runs on the new hardware. For example develop a scheduler to transfer stream data between memories and register files. From the analysis we found that the parallel image processing system can not only match image applications' characteristics but also easy to implement by using VLSI technology. With new language and software tools supporting, an embedded real-time parallel image processing system becomes available for programmers.

When parallelizing complex multimedia processing on multiple processors, the stochastic timing behavior should be carefully studied. Although there are already many papers on the performance analysis of stochastic parallel system, they are not targeted on multimedia processing. In this paper, first we study H.264/AVC encoder (running on x86) and QSDPCM encoder (running on TI TMS32C62) to characterize important aspects of the stochastic timing behavior in complex multimedia processing applications. It is shown that the variation and correlation are indeed very significant. In order to make systematic analysis feasible, we apply Stochastic Timed Marked Graph (STMG) as a formal model to capture essential timing related behaviors of parallel multimedia processing systems. Then, we show how the local timing variations and correlations interact and propagate to the global timing behavior; from this we conclude general parallelization guidelines. Furthermore, we develop an analytical performance estimation technique to derive the probability distribution of timing behavior for parallel multimedia processing systems that have correlated stochastic timing behaviors inside. The estimation technique is based on principal component analysis and approximations.

In an advanced micro-lithographic system, it is of critical importance that components are resiliently isolated from external vibrations. A passive/active electromagnetic device is a feasible solution to perform such vibration isolation. Within this device, passive permanent magnets provide the gravity compensation and active electromagnets accurate positioning. The focus of this article is on permanent magnet modeling, since a precise model is inevitable to achieve the high accuracy required for such application. This article describes a study on interaction force along three degrees of freedom (DoF) between permanent magnets having an unaligned magnetization direction for use in a permanent-magnet based suspension application. Feasibility of finite element modeling (FEM) and analytical modelling for such structures is discussed, implemented and verified with measurements.