Yuko Tsusaka

Development of standing-up motion assist robot to realize physiotherapist skill for muscle strength maintenance

This paper proposes a method for standing up that utilizes a patients own power to their fullest extent while allowing the person to stand up easily. Analyzing the skills of physiotherapists, we extracted two skills that we believe allowed them to assist patients in standing up by themselves: (1) promoting a forward-bending posture by making it easier to arch their backs and antevert the pelvis, and (2) providing balance so the patient does not fall down. In order to implement these skills, we propose (1) an inbuilt passive joint using a body holder to hold the patients upper body which reinforces a natural forward-bending posture, and (2) a horizontal position and vertical force assist control system which guides position control in the horizontal direction and assists with exerting force through force control in the vertical direction. We conducted experiments using linear stage system to assist with standing-up motion and confirmed that it promoted a comfortable and natural forward-bending posture through the inbuilt passive joint. Moreover, we compared standing-up motion using a control system that controls both vertical and horizontal positions with the proposed method, which guides the horizontal direction while assisting with vertical force. We found that in the position control system, when the patient performs the standing-up motion, they stand up at a predetermined constant velocity regardless of the force applied to the robot. On the other hand, the proposed method varied velocity in response to the force the patient applied to the robot. In other words, when velocity increases, the robots motion changes to apply more lifting force, and when velocity decreases, the robots motion changes to apply less lifting force. In other words, we confirmed that the system uses the patients remaining body power while assisting with standing-up motion.

Analysis of velocity's influence on forces and muscular activity in the context of sit-to-stand motion assisted by an elderly care robot

The sit-to-stand movement is an apparently simple yet fundamental activity of daily life. Failure of performing this movement strongly impacts the quality of life of an increasing number of elderly people. Much research thus focuses on assisting this motion. The time necessary for rising up from a sit position is very short for healthy subjects, in the order of few seconds. Using similar speeds for the assisted motion would create safety concerns, hence slower speeds are usually employed. In this paper we experimentally investigate the effects of this speed reduction. We detail the relationship among robots speed, forces acting on the robots user and muscular activation. From the results of this analysis we derive indications on the speeds appropriate for assisting the sit-to-stand movement.

Target object color-based force feedback compensation control in master-slave systems

Visual color information is thought to affect human perception. This study proposes a master-slave system that performs force feedback compensation control based on the color of the target object. In this system, the ratio between forces exerted during tasks performed on dark and bright objects is used as a compensatory gain in the feedback force. The system is designed to maintain task consistency by ensuring a constant magnitude of force exerted during a task, even when the color of the target object varies. Basic experiments demonstrated that operators exert different forces on objects of the same weight but different color; in particular, the brightness of an achromatic object affects human perception of the force applied to it. In verification experiments, the difference between the force exerted on same-weight bright and dark colored objects by a master-slave system with no color-based compensation control was 2.24 N. Implementing the proposed control system, this difference was improved to 0.61 N. Therefore, this system can potentially ensure consistent work during tasks involving target objects of different colors.

Vascular load reduction control based on operator's skill for catheter insertion

This paper proposes a method for vascular load reduction control that operates in regard to the load on contact points of catheter and blood vessels in catheter insertion. We make an extracorporeal estimation of the load on the contact points, and perform control with a robot arm to reduce the estimated load. We aim to reduce the vascular load through extracting and vibrating action as actually applied by operators. In order to confirm the effectiveness of the proposed method, we conduct an evaluation experiment where a wire is inserted in a tube that simulates a blood vessel. As a result of the experiment we were able to estimate the force on the contact points with an accuracy of an estimation error of 9.1%. Moreover, through vibration control we were able to reduce the load to below 0.1[N] for places where there was an overload of more than 0.5[N]. For vibration control, the experiment also enabled us to derive an effective parameter adjustment method to remove obstructions.

Teaching data characteristics for direct teaching using a robot with a dual-shell structure

In this paper, a robot with a dual-shell structure is proposed to improve operability using direct teaching. The dual-shell structure separates the robot arm actuator from the gripper for the operator. Hence, during the teaching process, the robot arm is able to track the motion of the operator and the operability within the arms movable range can be improved. Furthermore, by inserting an elastic body into the robots dual-shell structure, operation with an adequate viscosity for the operator can be achieved. To assess the effectiveness of this structure, an evaluation system is constructed based on a dual-shell structure robot with an elastic body inserted, for the skilled task of inserting flexible printed circuits. In the evaluation experiments, it was found that the teaching time is approximately 1500 msec shorter with the elastic body, and no matter which teaching data is used, the flexible printed circuit is inserted successfully.