Takahiro Endo

This paper presents a leader-follower control method in which swarm robots, consisting of multiple autonomous and distributed units, cooperate to transport a circular object. Unlike previous approaches that require all robots to possess global information about the object and the goal or to communicate with one another, our method requires only a single leader robot to possess global knowledge and uses no inter-robot communication. Each follower robot operates in a fully distributed manner, autonomously determining its motion based solely on local information obtained within its sensing range. The followers contribute to the transportation task by pushing the object toward the leader while preserving the connectivity of the group. As a result, even robots with limited capabilities can collectively perform the transportation task based on local information. The method is structured into five phases. A mathematical analysis is provided to demonstrate that each phase achieves its intended purpose, ensuring that the object’s velocity vector successfully aligns with the direction toward the leader. The effectiveness of the proposed approach is validated through both dynamic simulations and real-world robotic experiments, which confirm that the object is successfully moved toward the leader.

This paper addresses the vibration suppression of a flexible arm modeled by a hybrid PDE-ODE model. Flexible arms, known for their speed, efficiency, and safety, are commonly modeled with the Euler–Bernoulli beam. However, this study uses the Timoshenko beam model for improved accuracy, accounting for shear and rotational inertia, making it applicable to more scenarios. A novel finite-time boundary controller is proposed to suppress vibrations within finite time, where the finite-time control is not previously proposed for the Timoshenko arm modeled by the hybrid PDE-ODE model. In particular, the proposed controller simplifies implementation by utilizing boundary sensing and actuation. The paper proves the finite-time stability of the system and validates the controller through numerical simulations. This work offers a practical and innovative solution for efficient vibration suppression in flexible arms.

This paper presents a method to enhance the haptic sensation of the fingertip by applying a vibrotactile noise to the wrist, an application of stochastic resonance. This sensation is known to improve when a sufficiently large noise is propagated to the fingertip. However, it is reduced when a large noise that humans can perceive is applied to the wrist. Therefore, this paper uses band-limited noise consisting of frequencies necessary to activate specific mechanoreceptors required for specific tasks. This allows us to apply a sufficiently large but still imperceptible noise to the wrist. On the basis of this procedure, we propose a method of improving the haptic sensation of the fingertip. Further, we conduct experiments to confirm the validity of the proposed method.

We investigated the ability of two fingers to discriminate stiffness with stochastic resonance. It is known that the haptic perception at the fingertip improves when vibrotactile noise propagates to the fingertip, which is a phenomenon called the stochastic resonance. The improvement in the haptic sensation of a fingertip depends on the intensity of the noise propagating to the fingertip. An improvement in the haptic sensation of multiple fingertips does not require multiple noise sources, such as vibrators, to be attached to multiple fingertips; i.e., even a single vibrator can propagate noise to multiple fingers. In this study, we focus on stiffness discrimination as a task using multiple fingers, in which the thumb and index finger are used to touch an object and perceive its stiffness. Subsequently, we demonstrate that the stiffness perception is improved by propagating sufficiently intense noise to the thumb and index finger using only a single vibrator. The findings indicate the possibility of improving the haptic sensation at multiple fingertips using one vibrator.

This paper discusses a method to enhance fingertip tactile sensitivity by applying a vibrotactile noise at the wrist. This is an application of stochastic resonance to the field of haptics. We consider that the tactile sensitivity of the fingertip improves when a sufficiently large noise is propagated to it from the wrist. However, fingertip tactile sensitivity decreases when a large noise that humans can perceive is applied to the wrist. Therefore, in this paper, we cool the wrist skin to reduce the wrist's tactile sensitivity to noise. This allows us to apply noise that is large, but still imperceptible, at the wrist and thus to propagate it to the fingertip. On the basis of these procedures, we propose a method to enhance fingertip tactile sensitivity. Further, we carry out several experiments and confirm that the proposed method improves fingertip tactile sensitivity.

This paper proposes a decentralized navigation method with collision avoidance for a robotic swarm whose individuals possess heterogeneous abilities, such as sensing range and maximum speed. In this method, each agent distributedly constructs and maintains a local directed connection with another agent using only local information, which is relative distance. Moreover, all agents always maintain some distance from other agents to avoid collision. As a result, one leader robot can guide an entire swarm of robots to their destination, and the other robots can follow the leader while maintaining connectivity and not colliding with others. We prove the above mathematically, and we demonstrate the validity of the proposed method by numerical simulation and experimentation. GRAPHICAL ABSTRACT