Research On Safety Mechanism Of Internet-Based Multi-Robot Teleoperation System

With the development of the operational requests of human being in space, deep sea and nuclear area, teleoperation technology takes more important functions and becames one of the important research aspects in robot field. MOMR(multi-operator multi-robot) system has the merit of distribution and stronger operational capability, and using the Internet as a carrier of real time data transmitting improves some new characters such that publicity,distribution and equipment sharing. So it is one of the important research directions of how to overcome disadvantageous effects on system structure and network characteristics to realize MOMR teleoperation safely. And it can provide necessary theory basis and technology support for the application of robot technology in all areas by researching on the Internet teleoperation technology.For the evaluation to system safety, safety effects of the system as the basis of realizing safety planning and control are analysed first. Safety effects are analysed based on FTA (Fault Tree Analysis) and using the minimal cut sets depicts the combination of basic events about system dangerous states and attains the target of description of the relationship between critical fault and dangerous factors. Synthesis of the factors indicate that safety characters is a set of action modes which is decided by the aspects of intelligent concerning of operators, virtual environment, network interaction and safety planning which are the key of system safety mechanism.System safety mechanism depicts the structure and the relationship of the safety functional components, which can guarantee system safety. Based on the analysis of the factors which can effect safety mechanism, layered safety mechanism based on interactive monitoring layer in master place, network monitoring layer and real time monitoring layer in slave place is proposed. Safety control based on virtual guide model, collaborative discussion and virtual collision detection is realized in master place; distributed network platform is realized in network monitoring layer and safety control performance is promoted by network collaborative module. A robot can avoid danger based on real time collision avoidance and emergency state disposal method in slave place. Meanwhile, modular and distributed system safety information control is realized through the interaction of information and statements among the layers. For the abnormity in network transmiting process will influence on the interactive ability among the objects in network, even the system safety, a distributed network interactive platform is established based on Java RMI and CORBA IIOP technology to improve the interaction of network transmission, control, and system safety level. With the specification of CORBA, methods of real time thread pool and data distribution is proposed to increase the real time of CORBA platform. Network transmitting modal based on RMI-IIOP protocol is designed and network distributed virtual environment is built with Java-CORBA to improve the tele-interaction performance among the network objects by Java3D modeling technology.For the lackage of the levels of robot intelligence, design of virtual guide(VG) in the paper provides good accessory tools and a protective method to human's intelligence for system safety. By introducing VG concept, the general description and definition of VG model is given first. Then detective VG model oriented safety mechanism is established to realize time delay and collision detection. Three control modes with VG are proposed to help operators plan robot's motion in master place.Safe coordination in shared workspace of multirobot can increase task ability of robots in complex environment, and propose higher demands on the safety. Depending on the strategy of multirobot safety planning, in slave place improved potential field method based on speed and location of a robot is designed to realize real time safety planning. According to feedback information of robot location and the given safety critical area,, after collision points is detected in a shared space, safety motion planning is finished using improved potential field method as the guard under the condition of the planning failure in master place.The safety of MOMR teleoperation system is tested by three experiments. First multirobot loosely coordinated motion is designed to test the local safety planning algorithem of multirobot in a shared workspace. Then the safety of robots motion planned in VG based VE is tested by multirobot moving blocks experiment. In the last, dangerous medical environment oriented standard sample-test experiment is designed to test the efficiency of safety mechanism in teleoperation system...