Research On Teleoperation Through Large Time Delay And On Virtual Reality

Teleoperation through large time delay (T3D) is one of the key techniques in the field of space robot. One of the core problems in T3D is how to maintain the stability and to promote the transparency of the teleoperation system,on the condition of large time delay and limited bandwidth in the communication link between the operator control station on the earth and the robot workstation in space. This paper presents two basic points to cope with this problem. First,the impact of large time delay in the servo-control loop is avoided through the local automation of the telerobot,therefore,the stability is maintained. Second,the transparency is promoted by developing the advanced human-computer interface based on Virtual Reality (VR). Collision detection is one of the key techniques in the application of VR,which usually presents as the bottleneck of the computing performance in complex virtual environment. With the background of telescience experiment application,this paper concentrates on the research of accelerated algorithm for N-Body collision detection. The main contents in this paper include three aspects:framework for T3D system,teleprogramming,and accelerated collision detection methods.To develop a flexible coordination mechanism between the human operator and the machine,a Petri Nets based unified system framework for T3D is proposed,which,follows the concept of supervisory control,and covers the main aspects of the system,such as task modeling,task coordination,and task supervision. Under this framework,the task modeling methods based on Petri Nets are studied. An action-level task modeling method for free move is proposed,which is based on a method of key point extraction from the trajectory. A hierarchical task modeling method is proposed,which constructs the hierarchical model through the transition-refinement according to the Petri Nets system model of the subtasks. A task coordination method is proposed,which,according to the Predicates Transition Nets representation of the task space,through state recognization and action recognization,transacts the continuous actions of the operator to a series of instructions for the telerobot.In this paper,several key techniques relative to teleprogramming are studied,including:predective display through virtual environment,automatic program generation,and error corrtection of the virtual environment. A teleprogramming based experimental T3D system is developed. The typical peg-in-hole experiment is conducted,and T3D is simulated by artificial delay setup. The system is succeeded in the part-mating task,which proves the validity of the teleprogramming system for high-precision task.In this paper,a set of accelerated collision detection algorithms based on space subdivision are developed. One accelerated N-Body collision detection algorithm based on uniform spacial subdivision,called USSCD,is proposed. The performance of USSCD is compared with the well known algorithm,ICOLLIDE,through a series of experiments. Theresults show that,when the objects are evenly distributed,and the number of objects islarge,the performance of USSCD is better than that of ICOLLIDE. In this paper,a class of non-uniform spacial subdivision method is proposed,which is composed of two steps:first,the space is coarsely subdivided non-uniformly,based on the distribution density of the objects,then,every subspace is uniformly subdivided. A projection based non-uniform spacial subdivision method is proposed,in which the distribution density is measured by the histgram of the objects projection on three coordination axis,and the space is subdivided through a 'region-grown' algorithm. An adaptive space subdivision method based on clustering is proposed,which completes space subdivision through two steps:first the objects are classified through a new local-density based clustering algorithm,then the space is subdivided according to the clustering.