Kazuteru Tobita

A rotary encoder based on magneto-optical storage

A new kind of the rotary encoder based on the magneto-optical (MO) storage is proposed. Using the MO methods, a small high-precision high-response rotary encoder can be realized. High precision is achieved by a two-stage process in which the code disk is firstly written using the direct transfer recording, and then rewritten using the corrections based on the measured errors. The systems for writing to, reading from, and evaluating the MO encoder are developed, with the optimal MO encoder reading and writing parameters determined experimentally. A trial MO encoder with a resolution of 9000 pulses/revolutions is created directly from a reference encoder, delivering an accuracy of approximately 2.8 in. The maximum resolution and response frequencies achieved are 18000 p/r and 400 kHz. After the corrected transfer recording, accuracies of 1.3 in at a resolution of 2250 p/r and 1.7 in at 9000 p/r are achieved.

Hemispherical net-structure proximity sensor detecting azimuth and elevation for guide dog robot

We have developed a net-structure proximity sensor that detects the azimuth and elevation to a nearby object. This information can be used by robots to avoid obstacles or to respond to human behavior. We propose detection principles where the azimuth is detected by arranging two one-dimensional net-structure proximity sensors along orthogonal axes, and the elevation is detected by arranging two one-dimensional net-structure proximity sensors in a stacked ring. We also experimentally demonstrate the feasibility of these detection principles. The experimental result shows the sensor can detect azimuth at all peripheral angles and elevation from side to top up.

A guidance robot for the visually impaired: System description and velocity reference generation

This paper presents a guidance robot for the visually impaired along with generation of velocity reference signals. The guidance robot has an interface grip with a force sensor on the top. The robot can be operated intuitively through the interface grip, and at the same time, the position and the behavior of the robot can be provided to the user. An underactuated mobile mechanism is used. It can be moved in X and Y directions and is unconstrained in turning direction. The rotation center of the robot is determined by the users position. Environmental sensors are equipped for avoiding obstacles and hazards. In addition, the robot has redundant anti-falling systems for safety. The systems work independently from the environmental sensors. The robot is lightweight, foldable, and easy to carry. A versatile time-optimal reference generation algorithm is proposed for the robots velocity reference. The algorithm can set the bounds for the acceleration, jerk, and snap. Moreover, initial conditions and final conditions of the velocity, acceleration, and jerk can be specified. The switching surfaces are obtained with these parameters in the three-dimensional phase space, which allows the determination of the snap command for easy motion pattern generation. These parameters are changeable online.