Tool-based haptic interaction with dynamic physical simulations using Lorentz magnetic levitation

For my robotics dissertation I have designed and built a high-performance six degree-of-freedom magnetic levitation haptic interface device and integrated it with graphically displayed realtime three-dimensional simulated dynamic physical environments.; An ideal haptic interface would enable simulated objects to be sensed and manipulated in the same manner as real physical objects, at the same level of detail and responsiveness that the user is capable of sensing. To approach this level of performance requires stiff lightweight moving parts, powerful and responsive actuators, high resolution sensors, and a fast control system.; In tool-based haptic interaction, the user feels and interacts with the simulated environment through a rigid tool rather than directly with the hand and fingers. Tool-based tasks such as pushing, screwing, probing, and insertion can all be simulated with the new device. Lorentz levitation technology is well suited to tool-based haptic interaction because it provides motion and force feedback in 6 DOF with high control bandwidths and sensitivity due to non-contact actuation and position sensing and only one moving part. The range of the new magnetic levitation haptic interface is 25 mm in translation and 15--20 degrees in rotation to accommodate fingertip motions for fine haptic tasks. The device has a closed-loop position bandwidth of at least 100 Hz in each DOF, a maximum stiffness of 25.0 N/mm, and a position resolution of 5--10 um.; Detailed surface texture and friction effects have also been emulated using the new haptic interface device. Virtual coupling and intermediate representation methods were developed and implemented to provide realistic and stable haptic interaction with simulations using the haptic device and to maintain consistency between the fast device controller and the slower updates of the physical simulation. Additional user interface features such as rate control and variable scaling and offsets have been implemented to enable the user to move the virtual tool easily over arbitrarily large distances and rotations in the simulated environment using the limited motion range of the haptic device. The effectiveness of the haptic interface system has been demonstrated with interactive simulations of sample tasks.