2-Step Drop Impact Analysis of a Miniature Mobile Haptic Actuator Considering High Strain Rate and Damping Effects.

In recent times, the haptic actuators have been providing users with tactile feedback via vibration for a realistic experience. The vibration spring must be designed thin and small to use a haptic actuator in a smart device. Therefore, considerable interests have been exhibited with respect to the impact characteristics of these springs. However, these springs have been difficult to analyze due to their small size. In this study, drop impact experiments and analyses were performed to examine the damages of the mechanical spring in a miniature haptic actuator. Finally, an analytical model with high strain rate and damping effects was constructed to analyze the impact characteristics.

Design and verification of a novel hollow vibrating module for laser machining.

If a vibration module is added on laser machining system, the quality of surface finish and aspect ratio on metals can be significantly enhanced. In this study, a single mobility model of vibrating laser along the path of laser beam was put forward. In order to realize the desired unidirectional motion, a resonance type vibration module with optical lens was designed and manufactured. This cylindrical module was composed of curved-beam flexure elements. The cylindrical coordinate system was established to describe the relationship of a curved-beam flexure element's motion and deformation. In addition, the stiffness matrix of the curved-beam element was obtained. Finite element method and dynamical modeling were provided to analyze the resonance frequency and the displacement of the motion. The feasibility of the design was demonstrated with the help of experiments on frequency response. Experimental results show good agreement with theoretical analysis and simulation predictions.

Design of voice coil motor dynamic focusing unit for a laser scanner.

Laser scanning systems have been used for material processing tasks such as welding, cutting, marking, and drilling. However, applications have been limited by the small range of motion and slow speed of the focusing unit, which carries the focusing optics. To overcome these limitations, a dynamic focusing system with a long travel range and high speed is needed. In this study, a dynamic focusing unit for a laser scanning system with a voice coil motor (VCM) mechanism is proposed to enable fast speed and a wide focusing range. The VCM has finer precision and higher speed than conventional step motors and a longer travel range than earlier lead zirconium titanate actuators. The system has a hollow configuration to provide a laser beam path. This also makes it compact and transmission-free and gives it low inertia. The VCM's magnetics are modeled using a permeance model. Its design parameters are determined by optimization using the Broyden-Fletcher-Goldfarb-Shanno method and a sequential quadratic programming algorithm. After the VCM is designed, the dynamic focusing unit is fabricated and assembled. The permeance model is verified by a magnetic finite element method simulation tool, Maxwell 2D and 3D, and by measurement data from a gauss meter. The performance is verified experimentally. The results show a resolution of 0.2 µm and travel range of 16 mm. These are better than those of conventional focusing systems; therefore, this focusing unit can be applied to laser scanning systems for good machining capability.

Note: Design of a novel ultraprecision in-plane XYθ positioning stage.

This paper presents the design, fabrication, and experimental results of a novel ultraprecision in-plane XYθ positioning stage with kinematic decoupling between translational motion and rotational motion components. Two translational motions are guided by four cymbal mechanisms that have both motion guide and motion amplifier. Four leaf springs guide a rotational motion amplified by a Scott-Russell linkage mechanism. The proposed stage has advantages such as an in-plane symmetrical configuration as well as ease of design and control by serial kinematics. The experimental results demonstrate that the stage has a translational full motion range of 58 µm and a rotational full motion range of 1.05 mrad. The crosstalk experimental results show good agreement with the theoretical prediction of the decoupling between translational motion and rotational motion.

A new magnetic bearing using Halbach magnet arrays for a magnetic levitation stage.

Next-generation lithography requires a high precision stage, which is compatible with a high vacuum condition. A magnetic levitation stage with six degrees-of-freedom is considered state-of-the-art technology for a high vacuum condition. The noncontact characteristic of magnetic levitation enables high precision positioning as well as no particle generation. To position the stage against gravity, z-directional electromagnetic levitation mechanisms are widely used. However, if electromagnetic actuators for levitation are used, heat is inevitably generated, which deforms the structures and degrades accuracy of the stage. Thus, a gravity compensator is required. In this paper, we propose a new magnetic bearing using Halbach magnet arrays for a magnetic levitation stage. The novel Halbach magnetic bearing exerts a force four times larger than a conventional magnetic bearing with the same volume. We also discuss the complementary characteristics of the two magnetic bearings. By modifying the height of the center magnet in a Halbach magnetic bearing, a performance compromise between levitating force density and force uniformity is obtained. The Halbach linear active magnetic bearing can be a good solution for magnetic levitation stages because of its large and uniform levitation force.

Development of compact high precision two degree of freedom XY piezoelectric stepping positioner.

In this article, a linear piezoelectric stepping positioner developed by Kang et al. [Rev. Sci. Instrum. 78, 075112 (2007)] is extended to have a two degree of freedom XY linear motion and it is experimentally evaluated. A resolution less than 10 nm, a speed of over 0.5 mm/s, push forces of 17.9 and 19.5, and stiffnesses of 6.54 and 5.90 N/microm are attained while maintaining a compact size of 96x96x39 mm3 and the required power consumption of 102.74 W.

Development of compact high precision linear piezoelectric stepping positioner with nanometer accuracy and large travel range.

Many application areas such as semiconductor manufacture, precision optics alignment, and microbiological cell manipulation require ultraprecision positioning systems with a high positioning resolution and large motion range. This article describes the development of a compact high precision linear piezoelectric stepping positioner for precision alignment of optical elements. The positioner is designed to have a compact and symmetric structure, high positioning resolution, large motion range, high force density, adequate dynamic range, and power-off hold. The positioner is fabricated according to these specifications and performance evaluation tests are carried out. A resolution of 10 nm, speed of 1 mms, push force of 25 N, and stiffness of 10.4 N/microm are attained while maintaining a compact size of 32x42x60 mm(3). The required power consumption is 52.33 W. The test results confirm that the developed positioner could be successfully applied to the precision alignment of optical elements.

Hepatic arterial infusion alternating with systemic chemotherapy in patients with non-resectable hepatic metastases from colorectal cancer.

BACKGROUND AND AIM: Hepatic arterial infusion (HAI) chemotherapy has a number of limitations, including a low rate of complete response and frequent extrahepatic recurrence, in colorectal cancer patients with non-resectable hepatic metastases. METHODS: Twenty-nine colorectal cancer patients with non-resectable hepatic metastases were consecutively enrolled for HAI alternating with systemic chemotherapy (HA + SC group). The protocol comprised six cycles of alternating HAI (5-FU + leucovorin for 14 days, and mitomycin C on the first day) and systemic chemotherapy (5-FU + leucovorin). Colorectal cancer patients with two or more hepatic metastases treated using hepatic resection and systemic chemotherapy (HR + SC group) were selected as a comparative group. RESULTS: Within the HA + SC group, complete response was achieved in eight patients (28%), whereas 13 patients (45%) showed progressive disease. Six of the eight patients with complete response lived for more than 38 months. Extrahepatic recurrences were more frequent in the HR + SC group than the HA + SC group (47 vs 21%, P = 0.024). The two groups did not differ with respect to overall and hepatic progression-free survival (P = 0.947 and 0.444, respectively), displaying median +/- SE values of 38 +/- 7 and 20 +/- 3 months in the HA + SC group, and 39 +/- 9 and 33 +/- 14 months in the HR + SC group, respectively. One patient in each group experienced toxic hepatitis, and sclerosing cholangitis occurred in one patient of the HA + SC group. Other complications were mostly grade 1 or 2. CONCLUSIONS: HAI alternating with systemic chemotherapy led to a promising response and hepatic progression-free survival, possibly reducing extrahepatic recurrence in colorectal cancer patients with non-resectable liver metastases.