Motion Planning Algorithms for a Rolling Sphere With Limited Contact Area

The paper deals with the motion planning problem for a rolling sphere with limited contact area. The system under consideration is represented by a hemispherical object that can roll without slipping or spinning on the plane. Under the constraints imposed on the size of the contact area, the construction of motion can be regarded as a problem of parallel parking in a finite number of movement steps. A motion strategy, realizing the movement steps by tracing generalized figure eights on the hemisphere, is introduced. Two different algorithms for this motion strategy, the circle-based and the generalized Viviani-curve-based ones, are proposed. The convergence of the algorithms is analyzed, and the computational feasibility of these algorithms is verified under simulation.     

ADAPTIVE CONTROL DESIGN FOR NONLINEARLY PARAMETERIZED SYSTEMS WITH A TRIANGULAR STRUCTURE

A novel adaptive backstepping design for a class of nonlinearly parameterized systems with a triangular structure is proposed. Under the Lipschitz condition with respect to unknown parameters of the system, an effective adaptive controller is designed without the requirement on the compactness of the unknown parametric set. Especially, the proposed adaptive control enables the advantage of “tuning function concept”, which results in only one estimation law for the unknown parameters. Our simulation with induction motor model particularly shows the viability of the obtained results.     

D.C. optimization approach to robust control: Feasibility problems

The feasibility problem for constant scaling in output feedback control is considered. This is an inherently difficult problem since the set of feasible solutions is non-convex and may be disconnected. Nevertheless, we show that this problem can be reduced to the global minimization of a concave function over a convex set, or alternatively, to the global minimization of a convex program with an additional reverse convex constraint. Thus this feasibility problem belongs to the realm of d.c. optimization, a new field which has recently emerged as an active promising research direction in nonconvex global optimization. By exploiting the specific d.c. structure of the problem, several algorithms are proposed which at every iteration require solving only either convex or linear subproblems. Analogous algorithms with new characterizations are proposed for the bilinear matrix inequality (BMI) feasibility problem.     

Exchange-biased soft underlayers for perpendicular recording

We inserted NiFe/CoFe/antiferromagnetic-MnIr/CoFe layers between two CoTaZr soft layers to enhance the exchange-bias field (H/sub eb/) and then evaluated the effect of this lamination on the spike noise and recording characteristics of CoCrPt-SiOx media with an exchange-biased soft magnetic underlayer (SUL). The two CoTaZr layers were exchange-biased radially throughout the disk, and a higher H/sub eb/ was obtained for the upper CoTaZr layer. By using the laminated SUL, spike noise was suppressed even when the total thickness of the CoTaZr layers was increased to 300 nm. Although the medium had a high H/sub c/ of 7.0 kOe, a fairly good overwrite and signal-to-noise ratio were obtained. As another application of exchange biasing, we also examined the possibility of combining exchange biasing and antiparallel-coupled (APC) soft layers; i.e., a pinned APC SUL. An exchange-bias field from the pinning layers to the lower CoTaZr layer and an exchange-coupled field between the two CoTaZr layers were successfully applied. The medium with the pinned APC SUL showed no spike noise throughout the disk, and wide-area adjacent track erasure was effectively suppressed.     

Effect of a new rifamycin derivative, rifalazil, on liver microsomal enzyme induction in rat and dog

1. The effect of a new rifamycin derivative, rifalazil (KRM-1648), on liver microsomal enzyme induction was studied in rat and dog with repeated oral administration of the compound. Relative liver weight, cytochrome b5 and P450 contents, enzyme activities of NADPH-cytochrome c reductase, aniline hydroxylase, p-nitroanisole O-demethylase, aminopyrine N-demethylase, and erythromycin N-demethylase were measured. 2. In rat, rifalazil treatment at 300 mg/kg/day for 10 days increased cytochrome b5 content but it did not affect liver weight, P450 content or enzyme activities. In contrast, rifampicin and rifabutin increased relative liver weights, cytochrome contents and enzyme activities under similar conditions. 3. In dog, rifalazil did not affect any parameters at 30 or 300 mg/kg/day for 13 weeks. 4. These findings indicate that rifalazil is not an enzyme inducer in rat and dog. This property differs from other rifamycin derivatives such as rifampicin and rifabutin.     

On the irreducibility condition in the structural controllability theorem

It is known that the structural system (A,B) is structurally controllable if and only if the corresponding matrix [A B] is generically full rank and irreducible. In this paper it is shown that the irreducibility condition alone implies that every nonzero mode of (A,B) is generically controllable. This result provides an easy proof to the structural controllability theorem stated above. In addition, it is shown that the basic structure of the Jordan canonical form of (A,B) remains unaffected, in the generic sense, under the variation of the free parameters of (A,B).     

Analysis of interaction tracks in a stacked film track detector

In a previous paper we presented a method to analyze the data in a stacked film track detector and obtained a nuclear charge distribution for the incident heavy charged particles in cosmic rays.In the course of the analysis, several events of nuclear interaction were found. The present paper presents a method to analyze these interaction tracks by using the results of previous analysis for ordinary (non-interacting) tracks.     

Selectivity of metal cations and lithium isotopes on ion exchangers in the hydrogen form prepared by thermal treatment of NH4Zr2(PO4)3

NH₄Zr₂(PO₄)₃ with different particle sizes and different specific surface areas were obtained by controlling the preparation conditions. HZr₂(PO₄)₃, cation exchangers in the hydrogen form, were prepared by the thermal treatment of NH₄Zr₂(PO₄)₃ in the temperature range of 400 to 700°C and their ion exchange properties were investigated with the main focus on the selectivity for group I and II metal ions and lithium isotopes. Irrespective of the temperature of the thermal treatment, HZr₂(PO₄)₃ showed especially high affinity toward the lithium ion, high affinity toward the sodium ion and had little selectivity for the rubidium and cerium ions from the group I metal ions, and showed no specific affinity toward any of group II metal ions. HZr₂(PO₄)₃ were isotopically ⁶Li-specific in any conditions examined. The ⁶Li-to-⁷Li isotopic separation factor was nearly independent of temperature of the thermal treatment. It depended, however, on the pH of lithium ion-containing solution used as the solution phase in an ion exchange experiment. This pH dependence of the lithium isotope separation effect was due to the appearance of the LiZr₂(PO₄)₃ phase and/or the hydration number of the lithium ion in the ion exchanger phase.     

Molecular orbital simulations on electron-induced degradation of perfluoropolyethers with several types of segments

Semi-empirical molecular orbital simulations on electron-induced degradation of perfluoropolyethers (PFPEs) with several types of segments, such as methylene oxide, ethylene oxide, ethylene oxide-methylene oxide, linear and branched propylene oxide, were carried out. The calculated heat of formation indicated that the anion radical states of these species had lower energy levels compared to neutral states. The paper postulates that electron attachment to PFPE easily occurs on electron-rich surfaces. The anion radical was supposed to decompose to an anion and a neutral radical, while the cation radical was expected to degrade to a cation and a neutral radical. The formation of carbonyl difluoride was simulated in the case of the decomposition of perfluoropropylene oxide cation radical.     

Planning-Space Shift Motion Generation: Variable-space Motion Planning Toward Flexible Extension of Body Schema

To improve the flexibility of robotic learning, it is important to realize an ability to generate a hierarchical structure. This paper proposes a learning framework which can dynamically change the planning space depending on the structure of tasks. Synchronous motion information is utilized to generate ??modes?? and hierarchical structure of the controller is constructed based on the modes. This enables efficient planning and control in low-dimensional planning space, though the dimension of the total state space is in general very high. Three types of object manipulation tasks are tested as applications, where an object is found and used as a tool (or as a part of the body) to extend the ability of the robot. The proposed framework is expected to be a basic learning model to account for body schema acquisition including tool affordances.