Tube Cable Micro Swimming Robot Online Positioning Technology

Now micro robots have shown broad prospect of application in biomedicine, aeronautics and astronautics, military affairs, as they have low inertia, high resonance, short response time. To accomplish detection and maintaining, micro robot must have it's own close loop control system, the ability of location is critical. Because of micro robots' own characteristics, on line non-contact location to wireless in-pipe micro swimming robot remains an unsolved problem. In this paper, a new locating method for in-pipe micro swimming robot is developed.Firstly, the in-pipe micro robots are introduced, the research situation and main research contents and correlation technology are analyzed. Secondly, some robot location technology and sensors are compared and analyzed, some theory problems are researched deeply, such as ultrasonic location principle, structure design of micro robot, the attenuation compensation of returned ultrasonic, location algorithm of ultrasonic. Thirdly, the whole structure design and characteristics of the ultrasonic location system are introduced, the research value and difficulties are explained. Finally, the development of the location system of the in-pipe wireless micro swimming robots are discussed. The main difficulties are dealt as follows: (1) In order to decrease the influence from power and driver circuit, the electrical source of the digital circuit and analog circuit are isolated, and the driver and receiver circuits were isolated too. (2) In order to keep the stability of the ultrasonic signal, we have designed automatic gain compensation system, it is realized in FPGA and don't use the ports and process time of CPU. (3) To decrease the waste of system resource in useless signal, we have designed available data estimation module, it determines to start or end a collection by the shape of returned ultrasonic. (4) We use FPGA to design data collection circuits, so the costs are reduced, reliability is improved and the system is easy to upgraded and developed. In addition, cache using double dual ports RAM is used to save process time and other resource of CPU, we use LPC2106 cored by ARM as CPU. (5) A new location algorithm combining the time of flight method and phase detection method is used in this paper to discriminate 213.6ns time-intervals, the error contributed by location algorithm is 0.317mm in water.After debugging and improving, the results of experiment and measuring show that the system works stably and reliably, the system can achieve a location precision of 0.394mm in water. The error analysis and precision calculation show that this method is feasible.