Shigeki Toyama

Design of the TUAT/Karlsruhe humanoid hand

The increasing demand for robotic applications in dynamic unstructured environments is motivating the need for dextrous end-effectors which can cope with the wide variety of tasks and objects encountered in these environments. The human hand is a very complex grasping tool that can handle objects of different sizes and shapes. Many research activities have been carried out to develop artificial robot hands with capabilities similar to the human hand. In this paper the mechanism and design of a new humanoid-type hand (called TUAT/Karlsruhe Humanoid Hand) with human-like manipulation abilities is discussed. The new hand is designed for the humanoid robot ARMAR which has to work autonomously or interactively in cooperation with humans and for an artificial lightweight arm for handicapped persons. The arm is developed as close as possible to the human arm and is driven by spherical ultrasonic motors. The ideal end-effector for such an artificial arm or a humanoid would be able to use the tools and objects that a person uses when working in the same environment. Therefore a new hand is designed for anatomical consistency with the human hand. This includes the number of fingers and the placement and motion of the thumb, the proportions of the link lengths and the shape of the palm. It can also perform most part of human grasping types. The TUAT/Karlsruhe Humanoid Hand possesses 20 DOF and is driven by one actuator which can be placed into or around the hand.

Multi degree of freedom spherical ultrasonic motor

This paper presents a multidegree of freedom spherical ultrasonic motor. As a prototypical spherical ultrasonic motor, we have successfully developed two kinds of spherical ultrasonic motor with two degree of freedom. Each type has good controllability; the motor can drive a spherical rotor about an arbitrary axis; the maximum speed is 30 rpm; the maximum output torque is 0.7 kg cm; the maximum positioning error is 0.3 mm. It is expected to be applied to not only robotic manipulators actuator but also assembling machine, laser cutting and many fields.

Development of spherical ultrasonic motor as a camera actuator for pipe inspection robot

We present a pipe inspection robot using a newly developed spherical ultrasonic motor (SUSM) as a camera actuator. The novel SUSM has improved the range of movement compared to previous SUSMs, and the robot can point a camera in any direction. In this study, we determined a method for controlling the rotational direction and strategic control from the kinematics and characteristics of ultrasonic motors. The rotational directions were defined by the phase differences of the applied voltages, and the rotational speeds were changed with the frequencies. Additionally, we developed a very small position sensing system using rotary potentiometers. In the control experiment performed using the sensing system, the SUSM showed the returnability to the default position from several specified points, within an accuracy of 1°.

Control method of a spherical ultrasonic motor

In this paper, we propose a control method for controlling an arbitrary orientation of a rotor of a spherical ultrasonic motor (SUSM) by using a magnetized rotor and Hall devices. The arbitrary orientation of the magnetized rotor is determined by detecting the output voltage of the magnetic pole axis measured by Hall devices embedded in the center of each stator. The sensing method offers a size reduction for the entire structure as well as giving the rotor room to move in a wider range, since there is no restriction from geometry constraints of sensor devices, such as rotary encoders or potentiometers. We describe a method for detecting the arbitrary orientation of the magnetized rotor and the magnetization method of the rotor. The experimental results show that the magnetic field generated around the rotor is equally distributed, and confirm the validity of the proposed control method.

Design and implementation of spherical ultrasonic motor

We present a mechanical design and implementation of spherical ultrasonic motor (SUSM) that is an actuator with multiple rotational degrees of freedom (multi-DOF). The motor is constructed of 3 annular stators and a spherical rotor and is much smaller and simpler than conventional multi-DOF mechanisms such as gimbals using servomotors. We designed a novel SUSM using experimental data from a single annular stator and a finite element method. The SUSM using a spherical rotor of diameter 20 mm without any reduction gear has demonstrated advantages of high responsiveness, good accuracy, and high torque at low speed. The dynamic implementation of SUSM was consistent with the driving model of SUSM based on a friction drive.

Development of a Spherical Ultrasonic Motor with an Attitude Sensing System using Optical Fibers

We present a spherical ultrasonic motor (SUSM) and an attitude sensing system using optical fibers for the SUSM. The SUSM is constructed from three ring-shaped stators and a spherical rotor, and has three degrees of freedom (DOF). It has good responsiveness, high positioning accuracy, and strong magnetic field compatibility. In the attitude sensing system, a flat mirror is built in the spherical rotor. Light is emitted to the mirror, and the reflection is caught by optical fibers. The light intensities captured by the optical fibers are processed by a neural network and are converted to attitude information for the spherical rotor. We describe a system comprising the SUSM and the attitude sensing system with its design derived from mechanics and optics. The prototype SUSM is 26mm in diameter and was actuated by the attitude sensing system. Position errors with respect to x and y axes are less than 0.5deg.

Development of Wearable-Agri-Robot ∼mechanism for agricultural work∼

Recently, It has become a rapidly aging society. Coupled with a decrease in the number of farmers, this has becomes a serious problem in agriculture. Agricultural work includes a great deal of heavy work and special work postures, imposing a large physical strain on farmers. Therefore, we developed the Wearable Agri-Robot, which was designed as an exoskeletal mechanism to assist in the wearers work. This study evaluates the degree of freedom realized by forcusing on the range of motion of the joints. Using this method, we evaluated the articular structure of the Wearable Agri-Robot. We investigated the possibility of using it to assist in agricultural work by analyzing the motion required for thie type of work. In this work, we narrowed down the intended operations to the harvesting of Japanese radishes, and validated the effect of the Wearable Agri-Robot on the wearer using myoelectric potential measurement. As a result, it was ascertained that wearing the Wearable Agri-Robot could alleviate the burden on wearer by assisting with agricultural work.

Rotary-linear piezoelectric microactuator with a cubic stator of side length 3.5 mm

We report a miniature rotary-linear piezoelectric actuator with a single cubic stator of side length 3.5 mm which can generate rotary motion around the center axis and linear motion in the axial direction. The stator is fabricated as a single metallic cube of side length 3.5 mm with a 2.5-mm diameter through-hole and four piezoelectric elements bonded to the sides of the stator. The simplicity makes the actuator compact without any special manufacturing. In the design for miniaturization, the modal analysis using the finite element method indicates the natural frequency of the stator from the side length 14 mm to 3.5 mm. In the experiments, rotary motion of 24 rad/s and 2.5 μNm were obtained at a resonant frequency of 280 kHz, and linear motion of 80 mm/s and 2.6 mN was observed at 305 kHz by driving the system at an applied voltage of 42 Vrms.

Rotary-linear piezoelectric actuator using a single stator

We report a piezoelectric actuator having a single stator with rotary and linear motions (RLPA). The stator is fabricated as a single metallic cube with a through-hole. The surface of the inner circle of the hole generates elliptical motions at each natural frequency, transferring the energy to an output shaft, when AC voltages at the appropriate resonant frequency are applied to the piezoelectric elements. This study clarifies the principle of rotary and linear motions and uses finite element methods (FEM) to show how the elliptical motions are generated. Modal analysis illustrated the shapes of the vibration modes and the natural frequencies, and the shape of the stator was designed accordingly. A dynamic analysis of the stator showed the generation of elliptical motion in the directions of the rotary and linear motions. The prototype RLPA was successfully actuated at the resonant frequencies, consistent with the dynamic analysis. The speed of the rotary and linear motions was obtained.

Mobile robot path planning using vision and olfaction to search for a gas source

A new approach to search for a gas/odor source using a mobile robot is presented. When the presence of gas is detected, the robot turns in the direction of the airflow that carries the gas, and looks for any suspicious object. Path planning is performed using a potential field method. Unlike the classical obstacle avoidance techniques, a Mexican-hat shaped potential field is formed around the visually detected object. Consequently, the robot is guided along the perimeter of the object to sniff out the location of the gas leak. Experimental results are presented to demonstrate the validity of the proposed algorithm