Takahito Yamashita

Input shaping control to suppress sloshing on liquid container transfer using multi-joint robot arm

Transfer of container filled with liquid may generate sloshing, considered an undesirable effect in many systems. This research explores the use of input shaping technique to suppress sloshing on transfer of liquid container using multi-joint robot arm. By input shaping principle, acceleration command is shaped using two impulses in such a way to cancel each others response. Position trajectory is then translated as joint angles trajectory, which is then fed to Mitsubishi PA10-7C robot arm. Simple pendulum model with damping element is applied to analyze sloshing phenomena. Experimental results show that the employed input shaping technique reduces sloshing during and after container transfer.

Integrated trajectory planning and sloshing suppression for three-dimensional motion of liquid container transfer robot arm

For liquid transfer system in three-dimensional space, the use of multijoint robot arm provides much flexibility. To realize quick point-to-point motion with minimal sloshing in such system, we propose an integrated framework of trajectory planning and sloshing suppression. The robot motion is decomposed into translational motion of the robot wrist and rotational motion of the robot hand to ensure the upright orientation of the liquid container. The trajectory planning for the translational motion is based on cubic spline optimization with free via points that produces smooth trajectory in joint space while it still allows obstacle avoidance in task space. Input shaping technique is applied in the task space to suppress the motion induced sloshing, which is modeled as spherical pendulum with moving support. It has been found through simulations and experiments that the proposed approach is effective in generating quick motion with low amount of sloshing.

Vibration Control of Semiconductor Wafer Transfer Robot by Building an Integrated Tool of Parameter Identification and Input Shaping

Abstract High speed operation of industrial transfer robot arm generates residual vibration, which in many cases may limit productivity of the factory. In this paper, we use input shaping approach to reduce the residual vibration. The approach needs value of natural frequency and damping ratio to be identified in advance. We present an integrated tool of parameter identification and vibration control for higher modes vibration systems, as an easy and effective tool to help industrial people to analyze and solve the vibration problem. A semiconductor wafer transfer robot arm is used as an application case. Experiments have been carried out, and the results showed significant reduction in settling time as well as total movement time of the robot arm.

A robot-mediated information guide system.

This paper describes a robot-mediated information guide system that introduces audio-visual information to users interactively. The developed information guide system is composed of a touch panel interface, a mediator robot and backyard control systems. The touch panel interface functions to display audio-visual contents, while the mediator robot attracts people to this guide system and help users operation. Many robots in literature are equipped with interactive audio-visual interface, however in most cases the audio-visual interface is a front end of the robot for presentation. We propose a new communication framework in which the robot behaves as a mediator to make a bridge between users and audio-visual interface by generating speeches and gestures. We hypothesize that entrainment of the mediator robot with users and contents could promote users immersion in the contents. We conducted experiments with the proposed information guide system to examine the effect of robot mediation in a realistic interaction scenario that actually guides city sites for visitors. The developed information guide system was demonstrated in the science museum of the city in May 2014 and will be used for public events in future.

Safeness of a robot arm using ultrasonic motors with high responsiveness and backdrivability

We propose a robot arm using ultrasonic motors and demonstrate its characteristics such as high responsiveness and backdrivability, which are important characteristics in the view of the safety. The high responsiveness allows the robots to avoid collision against any objects and backdrivability makes the robots have compliance to unexpected actions of people. In this paper, we clarify the responsiveness and backdrivability of the ultrasonic motors experimentally. For the demonstration, we build a prototype robot arm having three joints which are all directly coupled to the output axis of the ultrasonic motors. In the experiments, the robot showed the responsiveness less than a few milliseconds, torque control such as if torsion spring model, and the backdrivability as a free joint. We discuss the safety control strategy using these characteristics..