Design and control of intelligent heterogeneous multi-configurable chained microrobotic modular systems

Abstract

The objective of this thesis is the “Design and Control of Intelligent Heterogeneous Multi-configurable Chained Microrobotic Modular Systems”. That is, the development of modular microrobots composed of different types of modules able to perform different types of movements (gaits), that can have different (chained) configurations depending on the task to perform. Heterogenous is the key word in this thesis. It is possible to find in literature many designs concerning modular robots, but almost all of them are homogenous: all are composed of the same modules except for some designs having two different modules but one of them passive. In this thesis, several active modules are proposed (rotation, support, extension, helicoidal, etc.) that can be combined and execute different gaits. The original idea was to make the robots as smaller as possible, reaching in the end a final diameter of 27mm. Although they are not really microrobots, they are in the mesoscale (from hundreds of microns to tens of centimeters) and in literature they are called for simplicity minirobots or microrobots. Several modules have been developed: the rotation module (indeed it is a double rotation module, but for simplicity it is called rotation module) v1 and v2, the helicoidal module v1 and v2, the support module v1, v1.1 and v2, the extension module v1 and v2, the camera module v1 and v2, the contact module (it is included in the camera module v2) and the battery module. Some others are still in the design or conceptual phase, but they can be simulated. They are the SMA-based module (there is already a prototype), the traveler module (in the design phase) and the sensor module (in a conceptual phase). All modules have been designed with the idea to miniaturized them in the future, and so both the electronic and the embedded control programs are as simple as possible (maintaining the planned functionality). Parallel to the construction of the modules a simulator has been developed to provide a very efficient way of prototyping and verification of control algorithms, hardware design, and exploring system deployment scenarios. It is built upon an existing open source implementation of rigid body dynamics, the Open Dynamics Engine (ODE). Simulated modules have been designed as simple as possible (using simple primitives) to make simulation fluid, but trying to reflect as much as possible its real physic conditions and parameters, its electronics and communication buses, and the software embedded in the modules. The simulator has been validated using the information gathered from real modules experiments and this has helped to adjust the parameters of the simulator to have an accurate model. Although the first idea was to develop the microrobot for pipe inspection, the expe¬rience acquired with the first prototypes causes to realize that locomotion systems used inside pipes could also be suitable outside them, and that the prototypes and the control architecture were useful in open spaces. In this way, research was extended to open spaces and the ego-positioning system was added. The EGO-positioning system is a method that allows all individual robots of a swarm to know their own positions and orientations based in the projection of sequences of coded images composed of horizontal and vertical stripes over photodiodes placed on the robots. This concept can also be applied to the modules in order for them to know their position and orientation, and to send commands to all of them at the same time. To manage all of this a control architecture based on behaviors has been developed. Since the modules cannot have a big processor, a central control is included in the ar-chitecture to take the high level control. The central control has a model-based subpart and another part based on behaviors. The embedded control in the modules is entirely behavior-based. Between this two there is an heterogenous agent (layer) that allows the central control to treat all modules