Junzhi Yu

Parameter Optimization of Simplified Propulsive Model for Biomimetic Robot Fish

This paper is concerned with the parameter optimization for a simplified propulsive model of biomimetic robot fish propelled by a multiple linked mechanism. Taking account of both theoretic hydrodynamic issues and practical problems in engineering realization, the optimal link-length ratio is numerically calculated by an improved constrained cyclic variable method. The result is successfully applied to the 4-linked robot fish developed in our laboratory. The comparative experiments on forward swimming speed of the robot fish before and after parameter optimization verify the effectiveness of our method.

Leader-Following Formation Control of Multiple Mobile Robots

This paper presents a framework for controlling groups of autonomous mobile robots to achieve predetermined formations based on leader-following approach. A three-level hybrid control architecture is proposed to implement both centralized and decentralized cooperative control. Under such architecture, we decompose the global-level formation control problem of N robots into decentralized control problems between N-1 followers and their designated leader. In the leader-follower control level, two basic controllers are proposed to make the following robot keep relative position with respect to the leader and avoid collisions in the presence of obstacles. Then, graph theory is introduced to formalize specified formation patterns in a simple but effective way, and two types of switching between these formations are also proposed. Numerical simulations and physical robot experiments show the effectiveness of our approach

Adaptive task assignment for multiple mobile robots via swarm intelligence approach

This paper describes an adaptive task assignment method for a team of fully distributed mobile robots with initially identical functionalities in unknown task environments. A hierarchical assignment architecture is established for each individual robot. In the higher hierarchy, we employ a simple self-reinforcement learning model inspired by the behavior of social insects to differentiate the initially identical robots into specialists of different task types, resulting in stable and flexible division of labor; on the other hand, in dealing with the cooperation problem of the robots engaged in the same type of task, Ant System algorithm is adopted to organize low-level task assignment. To avoid using a centralized component, a local blackboard communication mechanism is utilized for knowledge sharing. The proposed method allows the robot team members to adapt themselves to the unknown dynamic environments, respond flexibly to the environmental perturbations and robustly to the modifications in the team arising from mechanical failure. The effectiveness of the presented method is validated in two different task domains: a cooperative concurrent foraging task and a cooperative collection task.

A framework for biomimetic robot fish's design and its realization

This paper is concerned with the design and motion control of a radio-controlled, multi-link and free-swimming biomimetic robot fish based on an improved kinematic propulsive model. The performance of the robot fish is determined by the fishs both morphological parameters and kinematic parameters. By ichthyologic theories of propulsion, a framework taking into consideration of both mechatronic constraints in physical realization and feasibility of control methods is presented, where multiple linked robot fish propelled by a flexible posterior body and an oscillating tail fin can be easily developed. The motion control of robot fish is decomposed into speed control, orientation control and submerging/ascending control. The speed of the swimming fish can be adjusted by changing oscillating frequency, oscillating amplitude and the length of oscillatory part, respectively, and its orientation is tuned by different joints deflections. The up-down motion is realized by a pectoral mechanism. Our robot fish prototypes verify that the presented scheme is effective in design and implementation.

A tracking controller for motion coordination of multiple mobile robots

This paper presents a new method for controlling a group of nonholonomic mobile robots to achieve predetermined formations without using global knowledge. Based on the dynamic leader-follower model, a reactive tracking controller is proposed to make each following robot maintain a desired pose to its leader, and the stability property of this controller is discussed using Lyapunov theory. By employing such controllers, the N-robot formation control problem can be decomposed into decentralized tracking problems between N-l followers and designated leaders. Additionally, graph theory is introduced to formalize general formation patterns in a simple but effective way and two types of switching between these formations are also proposed. Numerical simulations and physical robots experiments show the effectiveness of our approach.

Dynamic modeling and experimental validation of biomimetic robotic fish

This paper presents a dynamic model of robotic fish which synthesizes both the carangiform and anguilliform swimming modes. The designed robotic fish is divided into three parts: stiff anterior body, flexible rear body, and an oscillating lunate caudal fin. We use unsteady flow theory to analyze the motion of the anterior part and the links, and adopt basic airfoil theory for the caudal fin. By summing up the longitudinal force, lateral force and yaw moment on each propulsive component, the kinematic and dynamic equations of the swimming robotic fish can be derived. The desired propulsive characteristics including forward velocity, sway velocity, angular speed, motion trajectory as well as propulsive efficiency can then be obtained via solving ordinary differential equation. Comparisons between simulation results and real experiments are then conducted and discussed. A good agreement on dynamic characteristics demonstrates the validity of the proposed model

Optimized design and implementation of biomimetic robotic dolphin

This paper describes an overall design procedure for a free-swimming, radio-controlled, multi-link biomimetic robotic dolphin mimicking dorsoventral movement. The swimming performance of the robotic dolphin is determined by its morphological parameters and kinematic parameters. The thrust is produced by the up-down-motioned fluke, and the turning is achieved by its left-right-sided body deflecting. A 4-link, 550 mm-long robotic dolphin prototype is successfully developed in our laboratory and its basic motion abilities are measured and some data are analyzed which show some promising performance in aquatic environment

Design Framework and Motion Control for Biomimetic Robot Fish

This paper deals with the design and 3D motion control of a radio-controlled, multi-link and free-swimming biomimetic robot fish based on an improved kinematic propulsive model. The performance of the robot fish is determined by the fishs both morphological parameters and kinematic parameters. By ichthyologic theories of propulsion, a design framework taking into consideration of both mechatronic constraints in physical realization and feasibility of control methods is presented, where multiple linked robot fish propelled by a flexible posterior body and an oscillating tail fin can be easily developed. The 3D motion control of robot fish is decomposed into speed control, orientation control and submerging/ascending control. The speed of the swimming fish can be adjusted by changing oscillating frequency, oscillating amplitude and the length of oscillatory part, respectively, and its orientation is tuned by different joints deflections. The up-down motion is realized by a pectoral mechanism. The experimental results on designed prototypes verify that the presented scheme is effective in design and implementation

Construction and control of biomimetic robotic dolphin

This paper is concerned with the design, construction, and control of a biomimetic robotic dolphin equipped with mechanical flippers, based on a simplified engineered propulsive model. The robotic dolphin is modeled as a three-segment organism composed of rigid anterior body, flexible rear body, and an oscillating fluke. The dorsoventral movement of the tail produces the thrust, and bending of the body in the horizontal plane enables turning maneuvers. A dual-microcontroller structure is proposed to drive the oscillating multi-link rear body and the mechanical flippers. Swimming performance of the prototype robotic dolphin is tested, and the results confirm the effectiveness of the dolphin-like movement in propulsion and maneuvering

An adaptive task assignment method for multiple mobile robots via swarm intelligence approach

This paper describes an adaptive task assignment method for a team of fully distributed mobile robots with initially identical functionalities in unknown environments. The method is applicable for mediate- to large-scaled robot groups and tasks. A hierarchical architecture for task assignment is established for each individual robot. In the higher hierarchy, the self-reinforcement learning model inspired by the behaviors of social insects is employed to differentiate the initially identical robots into different kinds of high-level task specialists; while in the lower hierarchy, ant system algorithm is adopted to organize low-level task assignment. To avoid using a centralized component, local blackboard communication mechanism is utilized for knowledge sharing. The proposed method allows the robot team members to adapt themselves to the unknown dynamic environments, respond flexibly to the environment perturbations and robustly to the modifications in the team arising from mechanical failure. Simulations of a cooperative collection task validate the effectiveness of the presented method.