Fujio Ikeda

A proposal of right and left turning mechanism for quasi-passive walking robot

Passive walking robots are originally suggested to be walking down shallow slopes without any actuators and controllers. Most researches of passive bipedal robots have only be focused on walking on a straight line, although one of the important issues of walking robots is to move ahead for a target direction as they desired. The purpose of this paper is to develop direction control mechanism for an upper body driven quasi-passive 3D walking robot which can turn right and left on a flat surface. A walking gait of our 3D robot has a rolling motion from side to side of both legs on a frontal plane which synchronizes a pitching motion of a swing foot on a sagittal plane. Switching directions are made by a yawing motion mechanism which is attached on a hip joint above each leg. This mechanism makes use of yawing motion of the stance leg.

Evaluation of Posture Memory Retentivity using Coached Humanoid Robot

Sports training with conventional feedback devices, such as mirror and video, has some problems. For example, it is difficult to accurately grasp all joint angles for target skill, and to gaze and to have interest at each joint angle. To settle such problems, we have proposed a new training method using a coached humanoid robot to reproduce participants motion based on measured position data by motion capture system. The proposed method shows a superior training effort, since the robot is used not only for a feedback device and also for an avatar of self-coaching. As a basic analysis of the proposed method, this paper investigates posture memory retentivity, which is one of the important factors that influence the success of the proposed method, instead of motion for target skill. From experimental result, it can be seen that the training with the coached humanoid robot shows superior posture memory retentivity compared to the other two feedback device conditions, such as no feedback and mirror.

Identification for Input Sound Pressure Level in Hammering Test Based on Adjoint Variable and Finite Element Methods

In this study, we present the inverse analysis for identification of hammering signal in non-destructive hammering test. The performance function is defined by square sum of residual between the obtained and the computed sound pressure. Here, the problem is to find the input sound pressure so as to minimize the performance function. The formulation for this problem is carried out by the adjoint variable method, and the numerical simulation of the sound pressure propagation is carried out based on the wave equation and the finite element method. As a result of numerical experiments of forward analysis sets to correcting wave of sound pressure in input point of inverse analysis.

A study of a steering system algorithm for pleasure boats based on stability analysis of a human-machine system model

Maritime accidents of small ships continue to increase in number. One of the major factors is poor manoeuvrability of the Manual Hydraulic Steering Mechanism (MHSM) in common use. The manoeuvrability can be improved by using the Electronic Control Steering Mechanism (ECSM). This paper conducts stability analyses of a pleasure boat controlled by human models in view of path following on a target course, in order to establish design guidelines for the ECSM. First, to analyse the stability region, the research derives the linear approximated model in a planar global coordinate system. Then, several human models are assumed to develop closed-loop human-machine controlled systems. These human models include basic proportional, derivative, integral and time-delay actions. The stability analysis simulations for those human-machine systems are carried out. The results show that the stability region tends to spread as a ships velocity increases in the case of the basic proportional human model. The derivative action and time-delay action of human models are effective in spreading the stability region in their respective ranges of frontal gazing points.

Energy-Saving Mechanism of Active Vibration Isolation Stand for Transporting the Injured Using Pleasure Boats

This paper presents an energy-saving mechanism for an active vibration isolation stand for transporting the injured using pleasure boats. The basic strategy of saving energy consumption of the actuator is to lower the natural frequency of the active vibration isolation stand. The proposed mechanism contains two components that help to reduce the natural frequency. One is a tri-linear spring mechanism, which provides both a high degree of stiffness to support the weight of the injured, and a low degree of stiffness in equilibrium. The other component is a rotational inertia mechanism, which can increase the apparent sprung mass in the translation motion.Copyright

Evaluation of errors in reduced order modeling

The purpose of the paper is to make a comparison between the equation errors and the output errors which are used as criteria for measuring modeling errors in system identification. In many practical situations real systems have high system orders which are often unknown, and reduced order models are used for estimating the parameters of the systems. In such a case there inevitably exists a modeling error due to the reduction of orders. The modeling error is usually evaluated by the equation error and the output error. The paper analyzes a relationship between these two errors in the case of an ARX model, and consequently derives that the variance of the output error is no less than that of the equation error. It also examines how the systems characteristics affect these two errors. For this purpose, it attempts to describe the estimated model parameters by the system parameters. The result shows that when the system poles are near the unit circle, which means a marginal stability of the system, the variance of the output error takes the maximum value.