Ahstract- In this study, we propose a development and formation control of a passive mobile robot equipped only with servo brakes and no motors. The developed passive mobile robot can move forward by utilizing an external pulling force, and steers itself by controlling the servo brakes attached to each wheel. Systems composed of multiple mobile robots are very effective at exploring vast areas. However the coordination and simultaneous control of several robots utilizing simple information is a difficult task. Therefore we propose a leader follower architecture composed of multiple passive follower robots tethered to one active leader. In this paper, we first introduce the developed passive mobile robot. Then, we analyze the fundamental control method of this passive mobile robot from the perspective of the feasible braking control region, which considers the slip of the passive robot and the limitation of the external pulling force from the active leader. Lastly, a control law for the servo brakes attached to each wheel is proposed, followed by a feasibility study to determine whether the passive followers can stay in formation by controlling the servo brakes with the proposed control law.

We are going to develop an ultra-small nutrients analyzer, a compact 3D-monitor (shape, color, etc.), and an ultra-light environment sensor (light intensity, temperature, humidity, CO2, etc.), which can be installed near plants. Accordingly, plant growth estimation technologies based on micro-fluidic circuit model simulating plant vascular system are being developed. The model will be frequently corrected by using updated data given by those sensors. Furthermore, by making use of the estimation technologies, we try to find out suitable cultivation condition for producing plants having aimed characters. In this paper, in order to develop plant growth estimation technologies, we propose a method to analyze the growth of lettuce leaves and roots by image analysis based on visible and thermography thermal imagers captured by cameras in real time and non-destructive leaf and root growth in lettuce hydroponic culture.