Motion Navigation And Force Feedback For Robotic Teleoperation Based On Virtual Fixtures

Robotic teleoperation systems have been applied widely in scientific researches and industries. The in-depth research into robotic teleoperation is helpful to improve the transparency and facility of the telemanipulation systems. This dissertation focus on the position mapping and force mapping methods between masters and slaves, robotics motion navigation based on virtual fixtures and teleoperation system design when integrated with virtual environments.The position and force mapping methods between the master and slave have a direct impact on the feasibility, transparency and stability of the teleoperation systems. In order to maximally cover the workspace of the slave with the master motion, this dissertation proposes a workspace drift control strategy based on haptic assistance to extend the motion mapping range of the master. For improving the adaptability of teleoperation systems to different environments, a force mapping methods based on environment stiffness estimation is also proposed, by which the system automatically adjusts the parameters of the force mapping function based on the estimated environment stiffness. When the estimated value is less than predefined stiffness threshold, the environment is identified as soft environment and non-linear force-mapping method is adopted to enhance operator's perception to environment stiffness differences.In order to assist the operator complete a teleoperation task more precisely and conveniently, this dissertation defines five different virtual fixture basic constraints and the calculation method for their guidance direction is also proposed. For different motion patterns of the operator, virtual fixture guidance paths are generated to provide navigation for the slave. In order to reduce the errors of guidance direction calculation, an active compliance control strategy for virtual fixture guidance path is proposed.Virtual fixture constraint force reduces the transparency of the teleoperation system. To address this issue, a bilateral control scheme based on force feedback within virtual fixture constraint direction is proposed, in which the constraint force exerted by the master on the operator hand only exists in virtual fixture constraint direction, therefore the transparency of the teleoperation system is improved. This control scheme is implemented by MATLAB/Simulink and the simulation shows that it has a desirable steady-hand characteristic and a noticeable improvement in transparency besides the ability of guiding the slave robot along a desired path.A robotic teleoperation system integrated with a virtual environment is also developed. Virtual models of the slave and environments are created in master side to assist the operator in executing a task. The position commands sending to slave side are simulated in the virtual environments to verify their feasibilities. The interactive forces between slave and real environments are estimated, and the states of the virtual robot are updated in virtual environments. With no time delays between the operator and the virtual environment, real-time and stable vision and force feedback is produced.