Kenichi Yoshimoto

Robustness of power grasp

Power grasp is redefined as a type of grasp that its mechanism can resist passively against external forces without relying on feedback control of joint torques. A computational algorithm is invented to calculate the critical external force, a force which is requisite to move the grasped object in a definite direction. Virtual work is proposed as the quality measure of the robustness of power grasp. Because this measure is a scalar, it is convenient and suitable for the planning of power grasp. The effectiveness of the computational algorithm of critical external force and quality measure of robustness of power grasp is verified with a numerical example.<<ETX>>

Shape-memory-alloy active forceps for laparoscopic surgery

In laparoscopic surgery, forceps are stuck through trocars into the abdominal cavity, and dissect and grasp internal organs. Because of their straight shapes, the current forceps suffer from the narrow range of operation and limit the skill of surgeons. In this paper, we propose active forceps actuated by unconventional use of shape memory alloy. In developing active forceps, we utilize two properties of shape memory alloy, shape memory effect and super elasticity The forceps possess both stiffness for transmitting operation forces from surgeons and flexibility in changing their shapes.

Proposal of driver assistance system for recovering vehicle stability from unstable states by automatic steering

Recently, the direct yaw-moment control system, in which braking or driving torque is distributed appropriately to the tires on either side, has been put to practical use. Such systems are called VDC (vehicle dynamics control) or VSC (vehicle stability control), and are available on the market. These systems aim to present the vehicle from falling into an unstable state, and cannot bring a destabilized vehicle back a stable state. On the other hand, it is a well-known fact that an expert driver can recover a vehicle from an unstable to a stable state. This report proposes an assistance system that recovers vehicle stability from an unstable state by means of automatic steering. In the proposed system, when the vehicle is in an unstable state, steering is carried out automatically by an optimal regulator, and when the vehicle recovers, it returns control to the driver. The issue of how to return control from automatic to manual is of particular interest.

Development of high performance drive-recorders for measuring accidents and near misses in the real automobile world

Two types of drive-recorders were developed for recording data on automobile accidents and near misses. The first type was an accident drive-recorder (ADR) to record accident data only. The other type was a near miss and accident drive-recorder (NADR) to record both accident and near miss data. The ADR and NADR were each equipped with a CCD camera to obtain visual data on accidents and near misses from the drivers view. The recordable data items of the ADR and NADR included acceleration, angular velocity, video image, accident avoiding behavior and global position. In this paper, we introduce the design concepts, specifications and data recording methods of the drive-recorders, and report the results of their validation tests. ADR and NADR should provide more accurate data on accidents and near misses to assist in revising the safety regulations, improving the injury criteria and crash test procedures, and in developing new dummies.

Course tracking control algorithm using visual information

SUMMARY Automatic steering control algorithm has been proposed, which uses the motion of objects in a visual image (Optical Flow) obtained from an ITV camera looking ahead in the situation without forward vehicles. This algorithm is improved to be applicable to the situation in which the forward tracking course is invisible owing to the interfarence of the forward vehicles. The adjustment of the control parameters against the change in vehicle speed is confirmed by the computer simulation experiments.

Following performance evaluation of a mechanically coupled platoon

Coupling some trucks with the same destination is called a truck platoon system. The leading truck is driven manually and the following trucks are driven automatically by using sensors on the mechanical link. Mechanical links not only restrict the movability of the following trucks, but are also used for sensors. We evaluate the manipulability and the following performance on the linked platoon system. The relation between the measure of manipulability and the following performance is also explained. Finally, the optimized link formation is proposed in this paper.

An automatic steering control algorithm using optical flow

An automatic steering control algorithm is presented, which uses motion of objects in a visual image (Optical Flow) obtained from an ITV camera looking ahead. Computer simulation experiments are performed in order to evaluate the algorithm.

Experience and outlooks on our studies on robots

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Modelling of a driver's behaviour considering roll motion

Abstract This paper presents an anlysis of the control behaviour of a driver during curves and lane changes. We model the drivers behaviour taking the roll motion of the vehicle into consideration. Using this model with constraints on the roll angle, it is possible to model lane change maneuvers without specifying a path. The validity of the model is investigated through a comparison between computer simulation and experimentation using a driving simulator system.

Driver Models for a Vehicle Avoidance Maneuver in Cornering

This paper presents driver models for a vehicle avoidance maneuver in cornering. The models are based on a preview driver model which has either a compensation control or a pursuit control. The preview point is detected by a variation of the present radius which is equivalent to a third-order prediction model, including a centrifugal jerk. The unknown control gains in the models are determined by an optimization program based on a Legendre pseudospectral method. A second-order prediction model, commonly used in cornering analysis, is compared to numerical examples. For the compensation model, the Proportional-Integral (PI) control results in a steering angle with two distinct behavior clearly : 1) steady-state cornering due to the Integral (I) control and 2) transient response due to the Proportional (P) control. The pursuit control has a sufficient response when the steering angle for the steady-state cornering is provided via feed-forward control, even if the P control is used for the compensator.