In this paper, statics analysis is made for our proposed robotic catapults based on the closed elastica as a robotic element for generating motions with impulsive acceleration. The proposed robotic catapults are just bended elastic strips whose two ends are fixed to two rotational joints. By only driving rotational joints back and forth gradually in order to achieve snap-through buckling actively, we can easily obtain repeated impulsive motions of the elastic strip. However, the characteristic as the robotic element has not been clarified enough because the structure contains an elastic strip with large deformation. Ou r statics analysis for planar deformable type catapults shows as follows. From theoretical analysis, the shape of the elastic strip is stiffness independent and the actuator torque necessary to drive the rotational joint is proportional to the stiffness of the elastic strip. From numerical simulations, the proposed catapults have the structure that suppress the driving torque necessary to store elastic energy. Using these results, we can indicate a design guidelines for compact and powerful mobile robots moving briskly.
A passive walker can walk down shallow slope. This gait, which results from the interaction between the nonlinear dynamic system and the environment, is really a physical phenomenon in itself. Though the passive walking is energy efficient and has natural gait like human being, it is fragile. It is extremely difficult for a walker with knees to walk for several steps and achieve high success rate in the real world. The passive walker is a sort of hybrid system and can exhibit a stable limit cycle. Therefore, a global stability around the fixed point is essential for achieving robust walking. We focus on the stability mechanism of fixed point. In this paper, first, a global stabilization principle is mathematically established. Based on this principle, a simple mechanism making the inter-leg angle at heel-strike constant was adopted in the developed walker. Finally, the improvement of robustness is confirmed by a dynamical walking experiment.
This paper describes a theory and experimental results concerning a passive aerial acrobat robot without electric power. As the robot performs hand-to-hand on its flying trapeze, it utilizes no electricity but simply draws power from the mechanical potential energy of its swings. The robot, holding onto the trapeze, overcomes the rotation moment by aid of a counterbalance that is on the opposite side of the swing and the robot begins to move. When the counterbalance is set on the frame of the swing at offsetting distance, a large rotation moment is generated, even when the robot gets to the most inferior point. As the result, the robot rises at an accelerated rate through the bottom point. When the robot reaches up to the height of the next swing, the hand of the robot slips from the handrail and the robot is released from the swing. At that time, the robot's arms extend forward by a spring installed inside the body of the robot, and the robot can catch hold of the handrail of the next swing. The angle of the handrail is adjusted to stabilize movement. It was confirmed from the experiment that the robot was able to transfer continuously throughout a set of the swings.
To structure environment in informative way through the sensor network with distributed RFID tags is a promissing approach to an autonomous intelligent robot working in an ordinary environment for daily human life. This paper proposes methods to integrate the data from sensors into online database of the environment and to provide a robot with realtime information of the dynamically changing situation of its surroundings. Based on the analysis of sensor functions and data requirement from the robot, we have designed and implemented a data management system. In the experiments, decision and action of the robots in a task context have been successfully achieved by using the data provided through the data management system.
This paper describes a method of cooperative strategy which enables a wheelchair and a wheeled robot to climb a step by a simple link mechanism which connects between them. We perform a numerical calculation to clarify the combination of two supporting positions of the connecting link that connects the two vehicles which enable them to climb a step and is stable at the same time. We conclude from the result of the simulation that it is necessary to change the link positions to climb a step safely. We ascertain the effectiveness of this method by means of experiments.
Tactile sensors are required for various robots. In humanoid robots, softness is an important feature for physical damage prevention and for interacting with the human. Moreover, if the sensor is made of stretchable material, the sensor is unbreakable and can be put on curved surfaces and joints easily. This paper proposes a novel tactile sensor which is flexible and stretchable because it is made of soft material. The sensor utilizes static electricity and electrostatic induction phenomenon, and can detect some touch conditions. Detail of principle and basic characteristics of the proposed sensor are reported in the paper. Experiments show that the sensor output depends on touch area, touch velocity, and material of touch objects. However, the sensor does not depend on touch weight. Moreover, an experiment shows that even if the proposed sensor is stretched, it performs as the tactile sensor.