Research On Teleoperation System Based On Master Device And Virtual Environment

Due to the delayed network communication,the information between both ends of teleoperation cannot be synchronous consistently,especially for space robot operations,where serious problems may occur such as instability and degraded performance.Compared with traditional delay control methods,virtual environment technology is currently the most effective method that can completely solve the network delay problem.Using the computer graphics and image processing,it establishes a virtual environment at the master site,which can have a real-time interaction with the operator locally,avoiding the communication delay radically.For the key technologies in virtual environment,this article introduces the mechanical structure and kinematics model of the master device firstly.Emphasizing on the tactile feedback function,an accurate dynamic model is established based on the principle of virtual work,where the friction and invariant parameters are estimated based on Lu Gre model and kinestate.Then,a virtual interactive model is established at the master site by using Open Inventor graphics library.The slave image and its feature points are acquired by the means of image processing,which is transmitted to the master for virtual-fussion.The overlaping between real image and vitual graphics is a powerful action to correct the offset of vitual environment.Moreover,a novel continuous switched contact model is proposed in this paper to express the complex slave environment.And a RLS algorithm combining both forgetting factor and self-perturbing function is designed to estimate the four model's parameters.Thus,the contact force can be predicted in real time at the master site according to the identified parameters and current kinestates.Finally,a complete teleoperation control system is established with its corresponding hardware and software control schemes for the master device and slave robot respectively.The functions include position collecting and force feedback of master device,servo control,image processing and force calculation of the slave robot,and the socket communication between the both ends.In order to verify the validity of the virtual model and local contact model,a specific task operating environment was set up in this paper where the slave robot is controled by master device to contact with different materials.The results show that the simulation model follows the movement of the master device in real time,which compensates for the delayed position.The identified parameters are in agreement with the actual properties of contact materials,which verifies the environmental adaptability of the CSCM model.What's more,the error of prediction force is small enough to replace the slave contact force,insuring the real-time haptic feedback at the master site.In conclusion,the virtual environment cleverly avoids the delay between the master and slave site,improving both the stability and transparency,enhancing the task operation performance of the system.