Zu Guang Zhang

Electrostatically Actuated Robotic Fish: Design and Control for High-Mobility Open-Loop Swimming

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.

Autonomously generating efficient running of a quadruped robot using delayed feedback control

We report on the design and stability analysis of a simple quadruped running controller that can autonomously generate steady running of a quadruped with good energy efficiency and suppress such disturbances as irregularities of terrain. In this paper, we first consider the fixed point of quasi-passive running based on a sagittal plane model of a quadruped robot. Next, we regard friction and collision as disturbances around the fixed point of quasi-passive running, and propose an original control method to suppress these disturbances. Since it is difficult to accurately measure the total energy of the system in a practical application, we use a delayed feedback control (DFC) method based on the stance phase period measured by contact sensors on the robots feet with practical accuracy. The DFC method not only stabilizes running around a fixed point, but also results in the transition from standing to steady running and stabilization in running up a small step. The effectiveness of the proposed control method is validated by simulations. MPEG footage of these simulations can be viewed at: http://www.kimura.is.uec.ac.jp/running.

Rush: A simple and autonomous quadruped running robot

Abstract In this paper, the system design and analysis of a quadruped robot, Rush, are presented. The quadruped robot was fabricated to study autonomous and efficient running on flat and rough terrain. It is a compact, kneed, four-legged machine with only one actuator per compliant leg. A novel control strategy for the quadruped robot has been proposed 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 the previous reports. In this paper, the results obtained from experiments with Rush are found to agree with the simulation results. The reported work may help improve the understanding of energy-efficient running locomotion and the simple control required to autonomously stabilize it on flat or rough terrain.

Design and Control of a Fish-like Robot Using an Electrostatic Motor

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.

Adaptive Running of a Quadruped Robot Using Delayed Feedback Control

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

Adaptive Running of a Quadruped Robot Using Forced Vibration and Synchronization

In this paper we regard legged locomotion (e.g., running) as adaptive vibration, which is capable of adapting to changes in internal parameters and in the external environment. We propose control concepts for such adaptive running in general, and present a theoretical study of the bounding locomotion of a quadruped robot according to the proposed control concepts. In our control method, a forced vibratory system with a synchronization function is constructed by using a rhythm generator and a torque generator. The states of both generators are modified by delayed feedback control (DFC) using a stance phase period measured by contact sensors. Such sensory feedback to both generators makes the system adaptive to changes in the physical parameters and also adaptive to changes in terrain. The effectiveness of the proposed method was confirmed by simulations using a quadruped robot with an active hip joint and a passive knee joint in each leg. MPEG footage of these simulations can be seen at: http://www.kimura.is.uec.ac.jp/running.

Development of a Magnetostrictive Linear Motor for Microrobots Using Fe-Ga (Galfenol) Alloys

This paper presents a unique magnetostrictive linear motor using Fe-Ga (Galfenol) alloys. The actuator is driven by a novel self-propelling mechanism that takes advantage of friction and inertial force. We describe in detail the driving principle and simply analyze it. We also present several experimental results regarding the performance of the fabricated magnetostrictive linear motor and verify the validity of the design of the actuator by these experimental results.

Stable quadrupedal running based spring-loaded two-segment legged on a model

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.

Primary Analysis of Frequency Characteristics in a Miniature Self-Propelling Device Using Fe-Ga Alloys ( Galfenol )

The present paper describes the theoretical analyses, design and experimental verification of a magnetostrictive actuating device, the locomotion of which is inspired by the motion of the smooth impact drive mechanism reported previously by a number of researches of our group. The proposed device is different from the reported device driven by a piezoelectric actuator. The proposed device is actuated by a micro magnetostrictive actuator constructed using an iron-gallium alloy. The proposed magnetostrictive actuating device is an interesting linear-moving mechanism and takes advantage of impact forces coupled with friction forces to achieve a long stroke with fine position resolution. The results of experiments indicate that the maximum speed of the prototype is approximately 1.0 mm/s at a current of 300 mA with a frequency of 4 kHz.

Towards Realization of Adaptive Running of a Quadruped Robot Using Delayed Feedback Control

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.