Massage therapy is crucial in the field of physical activities and sports to recover muscle fatigue and reduce stress. However, the physical workload on massage therapists is demanding, and the number of therapists is limited. To solve these problems, a massage robot that can move with human-like flexibility and delicacy was develop using a five-fingered robotic hand that mimicking a human hand. Moreover, the aim of this research is to develop a method of online estimation of a user's fatigue based on the muscle hardness in order to evaluate the effect of massaging from tactile information of the robot hand finger-tips to perform appropriate treatment. In this paper, we constructed a system about to measure muscle hardness based on reaction forces and measuring changes in muscle hardness and subjective fatigue over time before and after exercise. Then, the experiment of measuring muscle fatigue was conducted. As a result, the correlation coefficient between changes in muscle hardness and subjective fatigue highly correlated with five of the seven experimental participants. The result suggests the possibility that changes in the reaction force of muscles can be used as a measure for muscle fatigue recovery.

Unmanned Aerial vehicles (UAVs) are now a regular feature of modern society which are highly needed for the rescue mission and collecting information at unreachable places. But while the current generation of UAVs are undoubtedly useful, people around the world are increasingly talking of the need for smaller, more agile systems that can be easily transported and operated in narrow places. This leads to the development of Micro Aerial Vehicles (MAVs). However, miniaturizing MAVs is very challenging because various problems still remain unsolved. Among those, miniaturizing actuator and rotor blade are the most common. Hence, in this paper, we describe the development and trial production of micro ultrasonic actuator and micro rotor blade for the development of the smallest MAV in the world.

To prioritize miniaturization, the actuators of micro robot hands are placed far from the end effectors, but such mechanisms restrict controllability and dexterity. We propose a miniature robot finger driven by a new micro linear ultrasonic motor as a key component for micro robot hands. It enables dexterous and multiple motions for micro hands used in limited spaces. In this paper, we build a new micro linear ultrasonic motor involving a cuboid stator with a side length of approximately 2 mm, making it one of the smallest linear motors. The micro linear ultrasonic motor prototype shows an output torque of approximately 7.75 mN at low voltage operation, which is sufficient force to handle tiny objects. The miniature finger, a closed-loop six-bar-linkage mechanism, is built by micro fabrication and connected to the motor prototype. The first demonstration of the miniature finger is shown under a high-speed camera with a high power lens.

Typical continuum robots, such as pneumatic and tendon-driven robots, have a restricted section length and require a large external component for pulleys and a compressor, making them unsuitable for locomotion. This paper presents a new mobile continuum robot design with virtually unlimited extensible sections. A driving unit, which has a mechanism similar to the rack-and-pinion, consists of three DC motors with gears, each of which moves each flexible tube. The rotation of the motor translates the flexible tube, which has a helical groove on the surface that meshes with the gear. The long flexible tube provides a large traveling distance as long as it does not buckle. The elongation and bending motion of each section may be controlled during operation by varying the speed of each flexible tube. This design not only allows the expansion of the robot to otherwise unreachable work areas but also improves the locomotion velocity by generating a large traveling distance of the flexible tubes. The most important point in this paper is to use multiple driving units for locomotion. Since all the driving units can be mounted on the same tubes, by increasing the number of them, the robot can take various forms without expanding its diameter. A preliminary prototype was built, and its crawling locomotion performance was tested using two operating sequences. The results indicate that earthworm-like locomotion can be achieved with good performance by elongating the sections even when the ground is slippery. The proposed design can be easily be rebuilt by anyone with access to a basic 3D printer.

We present a flexible ultrasonic motor that generates linear motion as a novel soft actuator. This motor is comprised of a single cube stator with a through-hole, and a flexible coil spring inserted into the hole. The coil spring, which has a diameter of 10 mm and length of 200 mm, is translated by a vibration generated in the stator. A preload between the stator and the coil spring is important for improving the motor performance. The coil spring inserted into the stator hole generates the preload by expanding in a radial direction. We build a prototype flexible ultrasonic motor, and examine its basic performance parameters such as thrust force, velocity, response time, resolution and flexibility. To demonstrate flexibility, we show the stable thrust force and velocity even when the coil spring is bent to a bending radius of 15 mm.

We propose an eye robot system with master-slave control using operator-gaze tracking data, which can produce a high response level such as that of the human eyes. The operators can move a remote robot camera by only moving their eye (master) in front of an eye tracking apparatus and obtain visual information of the environment surrounding the robot's eye (slave). The use of ultrasonic motors has enabled the high responsiveness of the robot eye and the compactness of the robot body. Our graphical user interface (GUI) makes the operation intuitive. We evaluate the robot system from modeling the ultrasonic motor model to the usability of GUI. Finally, the proposed robot system's usability compares well with that of the joystick typically used to operate robots.

This paper demonstrates that singular configuration of a two-link robot arm is advantageous in doing the task of pulling or lifting up a heavy object with small joint torques. As a result of numerical optimization, the initial configuration that minimizes the joint torques necessary for the task is close to the singular configuration where the arm is stretched out. The singular configuration has the dynamic feature that the joint angle vector can be accelerated in a certain direction almost independently of the mass of the object. Then, the joint torques can generate large kinetic energy efficiently at the singular configuration, and the energy can be utilized to pull or lift up the object. The experimental results show that the dynamic feature is practically useful, even when a feedback control is applied in order to make the object follow a planned trajectory.

This paper evaluates the dynamic and kinematic properties of a prismatic mechanism and shows its capabilities in performing home manipulation tasks when integrated into a robotic arm. Our design is motivated from the observation that human hand motions often follow a linear trajectory when manipulating everyday objects. We present the mechanical design for a light-weight, energy-efficient robot named PRISM that emphasizes translational motion. By simulating the dynamics equations and comparing the structure of commonly used anthropomorphic arms and our proposed arm, we verify that translational motion is more energy efficient with PRISM, and the robot can maneuver itself in narrower places. Through simulation experiments using state of the art manipulation planning algorithms, we analyze the success rates of PRISM and an anthropomorphic robot arm in performing basic tasks. The simulation experiments center on pick-and-place tasks in cluttered kitchen scenes. We show a real-world prototype of PRISM and perform several manipulation experiments with it.

We propose a singularity-based mechanism (SBM) to exploit the singular configuration that improves the angular acceleration instead of constraining the movement. The tradeoff between the responsiveness and the range of motion is achieved by varying a length of linkage in the SBM. In this paper, we clarify the responsiveness of the SBM using the dynamics analysis. For the demonstration, we build an experimental SBM system with the high responsiveness, a practical range of motion, and a size comparable to a human arm. In the experiment, the effectiveness of the SBM is shown in a vertical lifting task. The characteristic of the SBM that generates a large acceleration at start is similar to the human arm moved by a muscle. The similarity between the SBM and the human arm is analyzed in terms of the static torque.

This paper discusses the advantages of singular configurations of a two-link robot arm in achieving tasks of pulling or lifting a heavy object. Optimal base location and arm motion for minimizing the joint torques are examined by numerical simulations, and the base location where the robot arm is near a singular configuration at the start time of task is optimal. It is shown analytically that joint torques can supply energy to the system composed of the robot arm and the object efficiently near singular configurations of the arm. The energy supply rates at two singular configurations are derived based on the equations of motion of the system.

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°.

This paper presents a study on the optimal base location and arm motion of a mobile manipulator for door opening task. Numerical simulation results show that the base location where the manipulability of the two-link arm is almost degenerated at the start and end points of door opening is optimal.We show by analysis that the location has an advantage in supplying kinetic energy to the door by using torques at the joints of arm. In order to represent properly the arm motion near a singular point of manipulability, the rotational motion of the door is parameterized by piecewise fifth order polynomials of time, and the parameters of polynomials are optimized to minimize the joint torques.

We present a micro ultrasonic motor having rotary and linear motions (rotary-linear motor) suitable for endovascular diagnosis and surgery. The rotary-linear motor is miniaturized to the size needed to function in a blood vessel. The stator prototype is a cube of side 3.5 mm, and the main body is fabricated as a single metallic cube with a through-hole. Four piezoelectric elements are bonded to the sides of the stator. When AC voltage at each resonant frequency is applied to the piezoelectric elements, the circumference of the stator generates elliptical motions at each natural frequency. We can obtain the output from a shaft inserted through the hole. We developed the first prototype of the stator using the finite element method (FEM), and experimentally determined the output of the rotary-linear motor. In the rotary sense, approximately 260 rpm and 0.1 mNm were attained at a resonant frequency of 270 kHz, and in the linear sense about 50 mm/s and 0.01 mN was attained at 306 kHz by driving the system at applied voltages of 42 Vrms.

This paper presents the development of rotary and linear piezoelectric actuator (rotary-linear motor) for a surgical manipulator with MRI compatibility. The stator of the rotary-linear motor is fabricated as a single metallic cube with a through-hole and shaft is inserted to the through-hole. Four piezoelectric elements are bonded to the sides of the stator. When AC voltage at each resonant frequency is applied to the piezoelectric elements, the shaft can move to the rotary and linear directions. There are several control inputs such as the voltage, the frequency, and the phase difference of two AC voltages to control the motor. We have measured the characteristics of the control inputs. As the result, the control characteristics of voltages were linear and were better than those of the frequency and phase difference. On the other hand, the MRI compatibility test was conducted in 0.3 Tesla MRI. MRI image shows the practical quality of the image in the case of that the motor is placed at the center of the imaging volume of MRI while the motor is not driven.

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.