Design of nonlinear controllers for active vehicle suspension with state constraints

Design of active vehicle suspension has tradeoffs between three main performance metrics (passenger comfort, suspension deflection and road holding ability). It has been known that each performance can be achieved by H _∞ controller and they can be gathered by LPV (Linear Parameter Varying) method. However, because the suspension deflection limit was not explicitly considered, this limit may be exceeded. In this paper, the authors propose a “reference shaping“ based method in order to improve the control performance. In this approach, a “virtual reference” signal is imposed to the system such that the suspension deflection is kept small. The effectiveness of the approach is examined by numerical simulations. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Pectoralis major tendon avulsion in association with a proximal humerus fracture

We report a very rare case of an avulsion of the pectoralis major tendon in association with a two-part proximal humerus fracture. Pectoralis major tendon avulsion was confirmed intraoperatively during open reduction and internal fixation of the humerus fracture. In retrospect, the preoperative radiographic finding of posterolateral and proximal displacement of the humeral shaft suggested an injury to the pectoralis major. Because others have reported that the best treatment of a pectoralis major tendon avulsion is surgical repair, we feel that it is important to suspect such an injury in a proximal humerus fracture when this anatomic displacement is present.     

MiR-10a in Pancreatic Juice as a Biomarker for Invasive Intraductal Papillary Mucinous Neoplasm by miRNA Sequencing

New biomarkers are needed to further stratify the risk of malignancy in intraductal papillary mucinous neoplasm (IPMN). Although microRNAs (miRNAs) are expected to be stable biomarkers, they can vary owing to a lack of definite internal controls. To identify universal biomarkers for invasive IPMN, we performed miRNA sequencing using tumor-normal paired samples. A total of 19 resected tissues and 13 pancreatic juice samples from 32 IPMN patients were analyzed for miRNA expression by next-generation sequencing with a two-step normalization of miRNA sequence data. The miRNAs involved in IPMN associated with invasive carcinoma were identified from this tissue analysis and further verified with the pancreatic juice samples. From the tumor-normal paired tissue analysis of the expression levels of 2792 miRNAs, 20 upregulated and 17 downregulated miRNAs were identified. In IPMN associated with invasive carcinoma (INV), miR-10a-5p and miR-221-3p were upregulated and miR-148a-3p was downregulated when compared with noninvasive IPMN. When these findings were further validated with pancreatic juice samples, miR-10a-5p was found to be elevated in INV (p = 0.002). Therefore, three differentially expressed miRNAs were identified in tissues with INV, and the expression of miR-10a-5p was also elevated in pancreatic juice samples with INV. MiR-10a-5p is a promising additional biomarker for invasive IPMN.     

Structural analysis of cellulose triacetate polymorphs by two-dimensional solid-state C-C and H-C correlation NMR spectroscopies

For the elucidation of the crystal structures of the two crystalline allomorphs of cellulose triacetate (CTA), namely CTA I and CTA II, two-dimensional (2D) solid-state through-bond ¹³C-¹³C and ¹H-¹³C correlations NMR techniques applied to the two crystalline allomorphs of CTA. As a result, the ¹³C and ¹H chemical shifts of the glucopyranose ring of CTA I and CTA II were completely assigned by the 2D NMR spectra of these allomorphs. On the 2D ¹³C-¹³C correlation spectrum of CTA II, two sets of the ¹³C-¹³C correlations from C1 to C6 were observed. This indicated that the CP/MAS ¹³C NMR spectrum of CTA II can be characterized by its overlapping of the ¹³C subspectra of two kinds of 2,3,6-triacetyl-anhydroglucopyranose units and that there are two magnetically non-equivalent sites in the unit cell of CTA II. In the case of CTA I, the numbers of respective ¹³C and ¹H shifts of CTA I agreed with the those of the glucopyranose residue in the allomorph, strongly suggesting that the asymmetric unit of CTA I is only one glucose residue. In addition, conformational differences in the exocyclic C5-C6 bonds between CTA I and CTA II were strongly suggested by the notable differences in the ¹H and ¹³C chemical shifts at the C6 sites of these allomorphs.     

Surface-state electrons on a hydrogen film. 1. Annealing of the film

We have investigated the surface of thin films (thickness 2 µm) of solid H₂ between 1.5 and 4.2 K by measuring the ac conductivity of surface-state electrons (SSE). The films were prepared on a glass substrate by quench condensation at 1.5 K and were therefore initially strongly disordered. In fact the surface of the virgin films before any heat treatment was so rough that no current due to SSE could be observed. Annealing the films decreased the surface roughness and gave rise to a thermal-activation-type temperature dependence of the SSE conductivity. By proper heat treatment up to 8 K the activation energy could be reduced to 10k _B.On leave from the Hyogo University of Teacher Education, Shimokume 942-1, Yashiro, 673-14, Japan.     

Robust control method for the inverted pendulum system with structured uncertainty caused by measurement error

In this article, we propose a design method for an inverted pendulum system with a structured uncertainty. We consider that such an uncertainty is caused by a measurement error in the rotation angle of the pendulum and effects on the system structure that cannot be included in the nominal elements. For the uncertain system obtained, we apply an integral tracking control and the guaranteed cost control to design a robust, stable, tracking control system. Finally, we show the effectiveness of our method through a numerical example.     

Bottom-up pyramid cellular acceptors with three-dimensional layers

In 1997, C.R. Dyer and A. Rosenfeld introduced an acceptor on a two-dimensional pattern (or tape), called the pyramid cellular acceptor, and demonstrated that many useful recognition tasks are executed by pyramid cellular acceptors in time proportional to the logarithm of the diameter of the input. They also introduced a bottom-up pyramid cellular acceptor which is a restricted version of the pyramid cellular acceptor, and proposed some interesting open problems of the bottom-up pyramid cellular acceptors. On the other hand, we think that the study of threedimensional automata has been meaningful as the computational model of three-dimensional information processing such as computer vision, robotics, and so forth. In this paper, we investigate about bottom-up pyramid cellular acceptors with three-dimensional layers, and show their some accepting powers. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Trajectory tuning for the tracking problem of the underactuated mechanical systems: application to the PVTOL aircraft

The Planer vertical take-off and landing (PVTOL) aircraft is a typical example of an underactuated mechanical system and has a nonminimum-phase nature. When considering output tracking control, the Input/Output (I/O) linearization method is not appropriate since the stability of the internal dynamics is not guaranteed. Hauser et al. regarded this system as a slightly nonminimum-phase system which approximates to a minimum-phase one. Their control scheme yielded good results when the coupling factor was small, but the results were not acceptable when the coupling factor increased. In this article, we propose two approaches to improve the control performance. First, we consider the approximation error of Hauser's scheme as uncertainty, and apply the Linear Quadratic Regulator (LQR) method, which possesses robustness against uncertainty, to determine the stabilizing feedback coefficients. Second, from the fact that the tracking error is unavoidable, we use the “virtual reference trajectory” to design the tracking control law, and optimize this trajectory to reduce the tracking error between the “actual reference trajectory” and the “resulting trajectory”. This optimization also improves the control performance by choosing a suitable performance index. By using our approach, we achieve better performance even if the coupling factor is increased. We show these results by numerical simulation. This work was presented, in part, at the Seventh International Symposium on Artificial Life and Robotics, Oita, Japan, January 16–18, 2002     

Stabilization of linear time-invariant systems with periodic communication constraints by output sample hold control

This article considers feedback control systems wherein the control loops are closed through a real-time network, and expresses the linear time-invariant system with the constraint in an input or output as a periodic discrete time system. It is shown that this system is stabilized by using output sample hold contol. This method has the merit that the capacity of a sensor-controller communication bus is small. This work was presented, in part, at the 8th International Symposium on Artificial Life and Robotics, Oita, Japan, January 24–26, 2003