Generation of efficient and user-friendly queries for helper robots to detect target objects

We are developing a helper robot that carries out tasks ordered by users through speech. The robot needs a vision system to recognize the objects appearing in the orders. However, conventional vision systems cannot recognize objects in complex scenes. They may find many objects and cannot determine which is the target. This paper proposes a method of using a conversation with the user to solve this problem. The robot asks a question to which the user can easily answer and whose answer can efficiently reduce the number of candidate objects. It considers the characteristics of features used for object identification such as the ease for humans to specify them by word, generating a user-friendly and efficient sequence of questions. Experimental results show that the robot can detect target objects by asking the questions generated by the method.     

Classical thermodynamic approach to void nucleation in irradiated materials

Abstract

One of the major problems in building a future fusion power station is the development of suitable structural materials. These materials will be exposed to high energy neutron bombardment, with consequent changes in their mechanical properties – embrittlement, hardening and swelling, for example. A missing link in modelling these effects is an effective treatment of the nucleation of voids under irradiation. These voids are initially stabilised by transmutation helium but, once formed, grow by vacancy accumulation. In this paper, a quasi-chemical model is developed to calculate the entropy of a steel/helium system. Although a substantial contribution from quasi-chemical effects might be expected, the steady state concentrations of dissolved helium are found to be too low for such effects to manifest. The steady state concentration of dissolved helium is low in absolute terms, but the resulting supersaturation is very high, making it reasonable to assume that all available nucleation sites are instantaneously activated.     

Online Walking Pattern Generation and Its Application to a Biped Humanoid Robot — KHR-3 (HUBO)

The authors propose a simple on-line method for generating a walking pattern for the biped humanoid robot KHR-3 (HUBO). The problem of realizing a walking action in humanoid robots involves two components: generation of the basic walking pattern and the compensation required to maintain the robot's balance. Dynamic walking can be realized by incorporating the real-time stabilizing control algorithm developed for KHR-1, KHR-2 and KHR-3. The walking pattern of KHR-3 has four modes: forward/backward, left/right, curved walking and turning around. In the previous pattern generation of the KHR series, the step time and stride of the robot were fixed, and the walking modes, step time and action of stride without stopping could not be changed. Hence, the flexibility of the walking pattern of the robot needed to be upgraded. The walking pattern in this paper allows variation in the walking mode, step time and stride for each step. The pattern uses a simple mathematical form of trajectory curves, specifically the sine, cosine, linear and third-order polynomial curves, and the superposition of these curves is used to minimize the complexity and burden of the computation. The authors used a third-order polynomial to generate the trajectory of the robot's pelvis. With the aid of a simplified zero-moment point (ZMP) equation, the pelvis trajectories have a direct relationship with the ZMP trajectories. An effective means of generating the trajectories is introduced, and the scheme is verified experimentally under various walking conditions that take into account the step time and stride. The experimental platform, which has human-like features and movement, is briefly introduced here. With a simple kinematical structure and distributed control hardware architecture, the platform was designed to consume relatively low levels of energy. Moreover, the scheme for generating the trajectory is realized for variations to flexible walking.     

Stress Generated on Aluminum During Anodization as a Function of Current Density and pH

Anodic oxidation is accompanied by stressgeneration during the growth of the oxide. The presentstudy focuses on the stress-generation mechanism onaluminum as a function of the applied current density in acidic solutions of sulfuric acid ofdifferent strengths giving variable pH. Abeam-deflection technique was utilized for thedetermination of the magnitude and direction of stressesgenerated during the anodic oxidation process. Generally,thickness of the oxide determines whether the stress iscompressive or tensile in nature. The results have beeninterpreted in terms of the formation and annihilation of anion (O^2-) and cation(Al³⁺) vacancies. A reduction in thealuminum-ion vacancy concentration (V Al ³ ) results in a compressive stressdeflection, whereas tensile-stress deflection isintroduced by an increase in the oxygen vacancy(Vo²⁺) concentration. The mechanism isfurther elucidated by current-density jump/dropexperiments. The results show that stress in this caseis affected by the dissolution of the oxide at the oxide-electrolyteinterface.     

Workspace Generation for Multifingered Manipulation

In this paper, we propose a novel numerical approach and algorithm to compute and visualize the workspace of a multifingered hand manipulating an object. Based on feasibility analysis of grasps, the proposed approach uses an optimization technique to first compute discretely the position boundary of the grasped object and then calculate the rotation ranges of the object at specified positions within the boundary. In other words, workspace generation with the approach is fulfilled by obtaining reachable boundaries of the grasped object in the sense of both position and orientation, and the discrete boundary points are computed by a series of optimization models. Unlike in workspace generation of other robotic systems where only geometric and kinematic parameters of the robots are considered, all factors including geometric, kinematic and force-related factors that affect the workspace of a hand–object system can be taken into account in our approach to generate the workspace of multifingered manipulation. Since various constraints can be integrated into the optimization models, our method is general and complete, with adaptability to various grasps and manipulations. Workspace generation with the approach in both planar and spatial cases are illustrated with examples. The approach provides an effective and general solution to the long-term open and challenging problem of workspace generation of multifingered manipulation. Part of the work has been published in the Proceedings of IEEE/RSJ IROS2008 and IEEE/ASME AIM2008.     

Friction welding – critical assessment of literature

Abstract

Friction welding is now well established as a means of joining many different types of materials, because it has proved itself to be a reliable and economical way of producing high quality welds. The present paper introduces different friction welding processes, their advantages and shortcomings. The history of friction welding and typical applications are also reviewed. In the context of friction welding, a number of subjects, such as frictional behaviour, joining mechanism, interface temperature and heat generation, still exist, where different concepts for explanation of the physical mechanisms have been proposed by different investigators. To clarify some inconsistencies in the interpretation of the friction welding process, a thorough review and critical assessment of the literature associated with this process is attempted.     

Modelling heat flow around tool probe in friction stir welding

Abstract

The objective of the present paper is to investigate the effect of including the tool probe in the numerical modelling of three-dimensional heat flow in friction stir welding (FSW). The heat flow close to the probe/matrix interface is investigated. In the models presented, the heat is forced to flow around the 'probe hole'. In this manner, the material flow through the probe region, which often characterises other thermal models of FSW, is avoided. This necessitates controlling the convective heat flow by prescribing the velocity field in the narrow shear layer at the tool/matrix interface. As a consequence the sliding, sticking, or partial sliding/sticking condition can be modelled. Six cases are established, which are represented by three stages of refinement of the heat source model, combined with two different contact conditions, i.e. full sliding and full sticking.     

Optical generation,detection and non-destructive testing applications of terahertz waves

Optoelectronic terahertz generation and detection play a key role in the applications of non-destructive testing,which involves different areas such as physics,...     

Implementation of omnidirectional crawl for a quadruped robot

As a reptile animal crawls in a cluttered environment, so a quadruped robot should be able to crawl on an irregular ground profile with its static stability by adopting the straightgoing and standstill-turning free gaits. The generalized and explicit formulations for the automatic generation of straight-going gaits and various standstill-turning gaits are presented in this paper. The maximized stride for the straight-going gait and the maximum turning angle for the turning gait of a quadruped robot named TITAN-VIII in a gait cycle are discussed by considering the robot's mechanism constraints and the irregularities of the ground profile. The control algorithm, including control of the joint positions of the robot, is described to implement the desired walking path of the quadruped robot. The effectiveness of the proposed method is demonstrated through experimental result.