Hidekazu Kajiwara

Skill assist and power assist for periodic motions by using semi-active assist mechanism with energy control

This paper describes a skill assist method based on an energy control that employs a semi-active assist mechanism. For this mechanism, we have developed a soft and flexible power assist device that consists of elastic materials and a small DC motor. The assist force is the elastic force of the elastic materials, and this force is controlled by adjusting the length of the elastic materials by means of the DC motor. In our previous study, we confirmed that this mechanism has high power assist effectiveness. In this study, we consider correction of user motion correction by the semi-active assist mechanism in order to provide skill assist. We consider the motion to be an energy state and control the motion through energy control.

Application and performance evaluation of a lifting device with alternating rotation hoist

There exist vertical long ropes that need periodical inspection for infrastructure maintenance. Development of lifting devices along with the ropes is demanded for steady observation at human-unreachable positions. The lifting device based on alternating rotation hoist has been proposed for carrying inspection devices to the target level. This research realizes an automatic movement of the lifting device by computer control for the improvement of speed and accuracy. Furthermore, a new frame which is equipped with the inspection device is developed for saving weight and keeping balance. Through experiments, performances of the new frame and control system are evaluated from the aspects of speed, accuracy, weight and balance. The results show that the newly developed frame has advantages in weight and speed. The inclination of frame and ascender is measured. The error values are calculated to analyze the accuracy. And the developed control system can control frame effectively.

Study on spherical stator for multidegree-of-freedom ultrasonic motor

A multidegree-of-freedom ultrasonic motor (MDOF-USM) has excellent features such as high torque at a low speed and a self-holding force, compared with other types of MDOF motor. Therefore, the MDOF-USM has been considered for applications in robot joints, multidimensional systems, and spacecraft. In previous research, the MDOF-USM consisting of a spherical rotor and a stator vibrator of various shapes has been mainly studied. In contrast, the MDOF-USM consisting of a spherical stator and a rotor of various shapes is proposed in this paper. The excitation methods for vibration modes and mode rotation using piezoelectric plates and multilayered piezoelectric actuators were examined. Furthermore, a stator support method that does not significantly affect the vibration of the sphere was devised. From the results of experiments using the fabricated prototype stator, the generation of vibration mode and mode rotation were confirmed. Therefore, the possibility of the realization of the MDOF-USM using a spherical stator was indicated.

Analysis of power assist effect during skill assist for periodic motions under use of semi-active assist mechanisms

This paper describes an analysis of the power assist and the skill assist effects of a semi-active assist mechanism based on an energy control. For this mechanism, we have developed a soft and flexible power assist device that consists of an elastic material and a small direct current motor. The assist force is then the elastic force, which is controlled by adjusting the length of the elastic material by means of the motor. The skill assist is based on a motion correction method of periodic motions that was developed in a previous study. The control method can provide both power assist and skill assist affects. In this study, we analyze the adequacy of the power assist when simultaneously applying the skill assist.

Smart suit for horse trainers-power and skill assist based on semi-active assist and energy control

This paper describes semi-active assist control in the form of a smart suit for horse trainers. We have developed a soft and flexible power assist device named ”smart suit” for reducing users physical fatigue. The smart suit is a semi-active and flexible power assist devices. The semi-active assist mechanism consisting of elastic materials and a small DC motor is our original technology. The assist force is gained by the elastic force of elastic materials, and it is controlled by adjusting the length of the elastic materials by using DC motor. In this study, we applied the smart suit to horse trainers for reducing their physical fatigue in horse training to prevent their injuries. Moreover we aim developing an assist force control method based on the energy control for considering not only the power assist but the skill assit. In this paper, we confirm the energy control has the effectiveness of the power assist in the situation without the skill assist.

Residual correction method for fast calculation of arctangent in embedded systems

This study proposes a technique for approximating high-cost calculations at low cost in embedded systems. Fast calculation of arctangent (as given by atan2) was developed by the proposed technique. Relative to the atan2 standard library function, the resulting approximation is 20 times as fast and requires only one-third the memory.

Hopping Height Control of Hopping Robot by Periodic Input Control

In this paper, we deal with hopping height control problem for a hopping robot by periodic input control. In our previous research, we proposed periodic input control which can control the energy of a system by modulating the amplitude or phase of periodic input, and controlled periodic motion of various systems (such as pendulum or quasi passive walking robot). But periodic motions of these systems which we dealt were sinusoidal, and their motion cycles were almost constant. In this research, we apply periodic input control to a hopping robot whose motion is nonsinusoidal and motion cycle changes significantly depending on hopping height. First, we analyze the timing in which energy of a robot is efficiently excited by periodic input. Next, we design energy control law for hopping height control based on periodic input control. Finally, we show efficiency of our method in experiments.