This paper presents a project that aims at fabricating a biologically inspired robotic fish. The robotic fish is designed to be capable of propelling itself through oscillations of a flexible caudal fin, like a real underwater fish. In this paper, we describe the design features that underlie the operation of the robotic fish. These features include a unique actuator referred to as electrostatic film motor and a light and flexible power transmission system. The electrostatic film motor is made of two pieces of flexible printed circuit film and can be utilized as a new-type artificial muscle. The power transmission system permits reciprocating power to be converted to periodic oscillations and distributed to the caudal fin. Based on several design considerations inspired by biological concepts, we propose several open-loop swimming control strategies for the constructed robotic fish to accomplish fish-like motion (i.e., cruising, turning, and diving). Experiments of Seidengyo I, the first prototype of our electrostatic fish family, are carried out to confirm the validity of the original design and control. We further design Seidengyo II to improve on Seidengyo I and show the results of the experiments.

This paper presents a project that aims at constructing a biologically inspired fish-like robot. The robot is designed to be capable of propelling itself through oscillations of a flexible caudal fin, like a real underwater fish. In particular, the caudal fin is driven by a mechanism actuated by a unique actuator called electrostatic film motor. In this paper, the dynamics of the electrostatic film motor are briefly introduced so as to well understand its characteristics and behavior. Based on the theoretical analysis and several design considerations inspired by biological concepts, we realize the fish-like robot actuated by an electrostatic film motor and propose swimming control methods for it. Experiments are carried out to confirm the validity of the original design and control. The current robot achieves fish-like maneuvering and approximate velocity of 0.018 m/s in dielectric liquid.

In this paper we present the system design and analysis of a quadruped robot, Rush, that we have constructed to study autonomous and efficient running on flat and rough terrain. The Rush robot is a compact, kneed, four legged machine with only one actuator per compliant leg. We have proposed a novel control strategy for the quadruped robot in consideration of several engineering limitations on sensory feedback. Several simulation studies have already been performed to confirm the validity of the control strategy in our previous reports. Here, the results obtained from experiments with Rush are found to agree with the simulation results. The work reported in this paper may help improve our understanding of energy efficient running locomotion and the simple control required to autonomously stabilize it on flat or rough terrain.

We report on the design and stability analysis of a simple quadruped running controller that can autonomously generate steady running with good energy efficiency and suppress such disturbances as irregularities of terrain. The self-stabilization property of the mechanical system is the inspirational source for our idea. We propose an original Delayed Feedback Control (DFC) approach based on measurements of the stance phase period obtained from contact sensors. Here, the DFC approach will not only stabilize running locomotion around the fixed point, but also result in transition from the stand state to the steady bounding running. Finally, we show several simulation results on different terrain (e.g., flat and step) to characterize the performance of the proposed controller. MPEG footage of simulations can be seen at: http://www.kimura.is.uec.ac.jp/running

In this paper, we employed a conservative spring-loaded two-segment legged model to test the effect of passive dynamics on running stability. By numerical return map studies, we investigated system stability and discovered that passive generation of a large variety of cyclic jumping motion on the legged model is possible. The results of this study indicated that the dynamics of suitable mechanical system could significantly alone improve the stability of legged running and suggest that swing phase dynamics may play an important role in adjustment of forward velocity and apex height. Moreover, we used the spring-loaded two segment legged model as a template to construct a simplified model of our Tekken I quadruped robot on numerical simulation. Using the constructed simulator to investigate the quadruped robot system stability, we proposed a simple control method for quadrupedal bounding and verified its effectiveness. In addition, our studies relating to passive dynamics of quadruped robot might help to understand the reliable stability and remarkable maneuverability on our experimental robot.

This paper presents a new neural system and mechanical system for quadruped robots with compliant legs, a spring mechanism located at the ankle joint. PD-controller at hip and knee joints constructs the virtual spring-damper system as the visco-elasticity model of a muscle. The neural system model consists of a CPG (Central Pattern Generator) and reflexes. A CPG changes the own active phase based on sensory information. The desired angle and P-gain of each joint in the virtual spring-damper system is switched based on the phase signal of the CPG. The pitching motion of the body is entrained into the CPG as a sensory feedback. Therefore, adaptive running can be generated. Some experimental results of running on terrain of low degrees of irregularity are used to verify the effectiveness of the designed neuro-mechanical system.