Optimal design of mechanisms with applications to haptic interfaces 

The goal of this research project is the design and control of a high fidelity haptic interface.

We have proposed a coarse-fine approach to the electromechanical design, with the device handle being actuated in parallel by six fine-motion voice-coil actuators transported over a large volume by a coarse-motion stage. Because the handle has a low mass and is actuated in parallel, the device would have high resolution and frequency response. The large motion range is provided by the coarse-motion stage. We showed that, by coupling the handle to the coarse-motion stage via a compliant transmission, the device handle will also be able to exert large forces, and will not be limited by the poor static performance of the voice-coil actuators. For the coarse-stage design, several parallel coarse-motion platforms were examined from a workspace point of view. A novel twin-pantograph manipulator with all but one of the drive motors in the base was proposed for its simplicity and large non-singular workspace.  [Stocco and Salcudean '96].

Recently, we have developed general mini-max  algorithms applicable to worst-case mechanism performance optimization over a given workspace [Stocco, Salcudean and Sassani '98], as well as scaling techniques appropriate for such designs [Stocco, Salcudean and Sassani '98]. These algorithms have been applied to optimize the proposed coarse-stage parameters (link lengths and base-hinges locations), as well as to the design of a single stage five-degree-of-freedom twin pantograph haptic interface, shown below.

Twin-pantograph haptic interface.