Tsugito Maruyama

A real-time processor for the Hough transform

The Hough transform method for recognition can cope effectively with noisy backgrounds and gaps in boundaries. However, long computation time and large memory requirements have prevented it from being used in real-time applications. An architecture devised to solve those problems, with a focus on detecting straight lines, is presented. Examples are given of the use of an experimental hardware model for automatic inspection and measurement of objects in factories and laboratories. It took less than one second from picture input to straight line parameter reproduction for these examples. >

Micro-G emulation system using constant-tension suspension for a space manipulator

A hardware system for emulating microgravity for an on-the-ground space manipulator is described. The manipulator is suspended by wires, kept vertical by the suspension arms controlled to follow the manipulators motion. The manipulator base is supported by a six-degree-of-freedom mechanism, with which free floating is emulated based on the numerical integration of the dynamic and kinematic equations for the manipulator. The gravitational force acting on the manipulator is thus canceled by the combination of the contact force on the base and the upward tensile forces through the wires. Optimizing the manipulators suspension keeps the values of individual tensions acting on it constant, whatever the manipulators attitude. Experiments show that the suspension system is sensitive enough to emulate the vertical free-floating motion of a suspended object, and can be tuned to initiate a microgravity environment of at least 0.01 g under restricted conditions.<<ETX>>

Efficient collision detection using fast distance-calculation algorithms for convex and non-convex objects

This paper describes a practical and efficient collision detection algorithm for non-convex objects in R/sup 3/. The algorithm is based on two other distance calculation algorithms: one is for convex polyhedra and the other is for non-convex polyhedra. The applied algorithm is switched between convex and non-convex, according to the distance between the objects. The closest points between the objects are followed continuously in time and can be calculated by searching for the nearest neighbors of the previous closest points. This feature greatly improves the distance calculation speed and makes it possible, for instance, to pick and move an object with a mouse, interactively getting the distance between the object and other objects. The algorithm is implemented in C++, and embedded in a series of C++ class libraries for a graphic simulation system-which the authors have named ContactScope.

An analysis of disk flutter in hard disk drives in an aerodynamic simulation

We performed a numerical simulation using a three-disk model with shrouds to evaluate the effect of air flows in the axial direction in a hard disk drive. And to clarify the relationships between disk surface pressure and disk flutter that have been a matter of conjecture, we performed a response analysis using the unsteady hydrodynamic force that was obtained as the excitation force by our numerical simulation.

Ground-Based Simulation of Space Manipulators Using Test Bed with Suspension System

An experimental system simulating dynamic behavior of space manipulators is constructed for the purpose of technological demonstration of space robots and evaluation of their dynamic features. The system consists of a space robot with dual manipulators, a suspension system, and a control system. The manipulators are hung by wires at each joint of the manipulators to cancel the effect of the ground gravitational force. The tension of the wires is controlled to be constant to simulate on the ground the dynamic behavior of the manipulators in space. Dynamics of the two-link manipulators is analyzed experimentally employing the present ground facility through inspection of their dynamic features in space. The motion of the manipulator is restricted to a vertical plane as the first step of study. The outline of the experimental system is also briefly introduced. The results of the numerical simulation and the experiments show sufficient capability of the on-ground simulation to study dynamic behavior of the manipulator in space.

Unsteady analysis and experimental verification of the aerodynamic vibration mechanism of HDD arms

The authors investigate the flow structure in 3.5-in hard disk drives with a rotation speed of 10033 rpm, especially the unsteady flow around actuator arms with and without a weight-saving hole, and clarify the unsteady flow in detail. In the method of approach utilized in this investigation, they used: 1) a direct numerical simulation of the Navier-Stokes equations to analyze the flow field; 2) a laser Doppler velocimeter to measure the velocity field; and 3) a laser Doppler vibrometer to monitor unsteady displacement of the actuator arm. The authors find a three-dimensional spiral vortex in the wake region of the arm and the flow spilled from the weight-saving hole. These flows can be considered to be an excitation source for the actuator arm. The power spectrum of the arm torque generated by calculated wind disturbance agrees with that of measured wind disturbance. This verifies the existence of the predicted vortices and the flow spilled from the weight-saving hole.

Patterned media fabricated by lithography and argon-ion milling

Using continuous film prepared by lower gas sputtering, a dot array with a more stable single domain was achieved. The requirements for magnetic properties of patterned media were different from that of perpendicular continuous-film media. The switching field distribution in dot arrays depends on fluctuation in dot size. The smallest size of dot arrays, fabricated by most simple method as lithography and ion-milling, is 50 nm.

Satellite berthing experiment with a two-armed space robot

To study autonomous control of a space robot, the authors developed their Advanced Space Robot Testbed with Redundant Arms (ASTRA). Berthing a satellite moving in space is a difficult and dangerous task when done manually. This paper describes a robot which berthed a mockup satellite moving and rotating in zero gravity. Features of the robot include autonomous approach to a moving target satellite using visual satellite motion estimation, using real-time visual tracking control to track satellite handles with two robot arms, and grasping the satellite handles with minimum mechanical shock using a flexible wrist mechanism and impedance control. The authors ran their satellite berthing experiment on the ASTRA to check its performance.<<ETX>>

Localization and obstacle detection for robots for carrying food trays

This paper discusses a practical system which, when incorporated in an autonomous mobile robot moving indoors, can determine the position of the robot and detect obstacles so that the robot can navigate appropriately. We have developed new real-time, reliable techniques using correlation operations to achieve vision-based localization and obstacle detection. These techniques include a landmark detection technique that assures stable detection even under variable brightness and an obstacle measurement technique that combines obstacle region segmentation with stereo vision. Our experiments have proven that these techniques can make the necessary measurements in 100 ms, assure stable measurement in environments of varying brightness, and are sufficient for mobile robots.

Aerodynamic vibration mechanism of HDD arms predicted by unsteady numerical simulations

With increases in recording density and higher rotation speeds, the aerodynamic aspect of hard disk drives (HDDs) is now quite significant. We studied the internal airflow of HDDs using a direct numerical simulation. We simulated two cases: the first had an arm with no weight-saving hole (no-hole case), while the second had an arm with a weight-saving hole (hole case). We observed periodic vortices (Karman type) for which the frequency was about 4 kHz in the downstream of the arm in both cases. The scale of the vortex in the hole case was larger than that in the no-hole case. In the hole case, the spectrum of the arm torque had sharp peaks that would directly affect the head positioning accuracy. Moreover, we found that there was no remarkable peak in the no-hole case.