Profession: Student

Number of times previously entering contest: 1

Inspired by: Reconfigurable robots consist of many modules which are able to change the way they are connected. As a result, these robots have the capability of adopting different configurations to match various tasks and suit complex environments. For mobile robots, the reconfiguration is a very powerful ability in some tasks which are difficult for a fixed-shape robot and during which robots have to confront unstructured environments e.g. navigation in rugged terrain. The basic requirement for this kind of robotic system is the extraordinary motion capabilities. In recent years considerable progress has been made in the field of reconfigurable modular robotic systems, which usually comprise three or more rigid segments that are connected by special joints. One group of the reconfigurable robots featuring in interconnected joint modules realizes the locomotion by virtue of the structure transform performed by the cooperative movements and docking/undocking actions of the modules. Because the modules in these robots are not able to move independently and the possible structures of the robot are limited, these kinds of robots are not suitable for the field tasks. The other kind of reconfigurable robots being composed of independently movable modules is more suitable for the field environment. However, in complex field terrain, the fact that the existing reconfigurable mobile robots can only assume limited configurations due to relatively simple posture-adjusting is a ubiquitous deficiency. The project presented here aims at developing a reconfigurable mobile multi-robot platform made highly flexible and robust by its three-DOF posture-adjusting ability. The key object of the project is to develop a new posture-adjusting mechanism featuring in compact structure, large workspace and powerful driving ability. As a secondary object, the project has developed an effective connecting mechanism aligned to flat terrain and synthesized it with the posture-adjusting mechanism.

The locomotion abilities of the system are expected to be as follows:
1. The single robots in the system have an independent omni-directional locomotion ability equivalent to that of a normal outdoor mobile robot.
2. Due to the posture-adjusting mechanism, which enables the robots to drive very well and to operate in a large workspace, the robots can adjust the posture of their partners.
3. The connecting mechanism tolerating large posture deviation in flat terrain can link two robots in a locked connection and transit large forces and torques between them.
4. Compared with a single robot, the connected robots are able to perform more demanding locomotion activities, such as stepping over high obstacles, crossing wide grooves, passing through narrow barriers and self-recovering from invalid postures and other actions which are impossible for a single robot.

In the past decade, there has been some work on modularity in robotics the goal of making more versatile, easily adaptable manipulator arms. More recently there has been some work on adding reconfigurability to modular robotic systems. Again, the goal was to make even more versatile autonomous robot systems.

In this project, I wish to explore the versatility of reconfigurable modular robotic systems, the initial goal being to determine how versatile such a system can be. To make the problem manageable, the application domain was restricted to statically stable locomotion. To study versatility in a chosen domain, we must examine that domain in general. While there has been work on specific means of statically stable locomotion, a generalized study of locomotion has had little attention. The end result of this report is the creation of a taxonomy of the different kinds locomotion possible, and the design, construction and analysis of a robot that can achieve them. To reach the above targets, a novel reconfigurable mobile robot system based on a serial and parallel active spherical mechanism and a conic self-aligning connecting mechanism has been developed. This system is composed of three robot modules which are able to not only move independently, but also to connect to form a chain-structured group capable of reconfiguration. On flat terrain, each module can corporate with each other by exchanging information to keep up its high efficiency; while on rugged terrain, the modules can actively adopt a reconfigurable chain structure to cope with the cragged landforms which will be a nightmare for a single. In this project, after giving an overview, the discussion focuses on some special locomotion capabilities of it. Then the related kinematics analysis of the serial and parallel mechanism is discussed thoroughly as well as the theory of the connecting mechanism. Based on the discussion, the mechanical is introduced in detail.