Ryutaro Futakuchi

A Novel Thin Concentrator Photovoltaic With Microsolar Cells Directly Attached to a Lens Array

We propose a novel concept of thin and compact CPV modules in which submillimeter solar cells are directly attached to lens arrays without secondary optics or an extra heat sink. With this small cell size, the optical path length of the module can be brought down to one-twentieth that of conventional CPV modules. To achieve precise alignment of the microsolar cells at the lens focal points, we have developed a fluidic self-assembly technique that utilizes surface tension. This novel CPV module with triple junction microsolar cells demonstrated an efficiency of 34.7% under sunlight in the particular measured condition.

High-efficiency thin and compact concentrator photovoltaics using micro-solar cells with via-holes sandwiched between thin lens-array and circuit board

We have developed a compact concentrator photovoltaic (CPV) module that comprises micro-solar cells with an area of ≈0.6 × 0.6 mm2 sandwiched between a 20-mm-thick lens array and a 1-mm-thick circuit board with no air gap. To establish electrical connections between the circuit board and the micro-solar cells, we developed a micro-solar cell with positive and negative electrodes on the lower face of the cell. In this study, we demonstrated the photovoltaic performance of the micro-solar cell closely approaches that of the standard solar cell measuring ≈5 × 5 mm2 commonly used in conventional CPVs under concentrated illumination. Our study showed that the negative effect on PV performance of perimeter carrier recombination in the micro-solar cell was insignificant under concentrated illumination. Finally, we assembled our micro-solar cells into a CPV module and achieved the module energy conversion efficiency of 34.7% under outdoor solar illumination.

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.

High-efficiency Thin and Compact Concentrator Photovoltaics with Micro-solar Cells Directly Attached to Lens Array

We propose a thin and compact concentrator photovoltaic (CPV) module, about 20mm in thickness, one tenth thinner than those of conventional CPVs, to enlarge CPV application scenarios, and achieved an energy conversion efficiency of 34.7%.

A biomimetic strategy for designing easily-installable CPV tracking system with high wind resistivity

Due to its higher photovoltaic efficiency, CPV has the advantage of needing a smaller panel footprint than fixed PV systems. This characteristic makes it ideal for use as an independent power supply in remote locations where transportation and site procurement present a challenge. The overall system needs to be compact and light without sacrificing weather resistance. Skilled personnel are scarce in remote areas, so easy setup and maintenance are also important. We have developed two techniques based on the notion of bio-mimicry. One is machine learning to counteract errors in installation position without the need for human intervention, and the other is a three-dimensional panel structure that cuts the wind load by up to 20%. We describe our experimental results gained in field tests.