Donald D. Nelson

Haptic manipulation of virtual mechanisms from mechanical CAD designs

A haptic display system is presented for manipulating virtual mechanisms derived from a mechanical CAD design. Links are designed and assembled into mechanisms using Utahs Alpha-1 CAD system, and are then manipulated with a Sarcos Dextrous Arm Master. Based on the mechanisms kinematics and the virtual grasp, the motion of the master is divided into motion of the mechanism and constraint violation. The operator experiences the dynamic forces from the mechanism plus constraint forces.

Painting textures with a haptic interface

We present a method for painting texture maps directly onto trimmed NURBS models using a haptic interface. The haptic interface enables an artist to use a natural painting style while creating a texture. It avoids the traditional difficulty of mapping between the 2D texture space and the 3D model space by using parametric information available from our haptic tracing algorithm. The system maps user movement in 3D to movement in the 2D texture space and adaptively resizes the paintbrush in texture space to create a uniform stroke on the model.

Optimization-based virtual surface contact manipulation at force control rates

Previous interactive works have used springs, heuristics, and dynamics for surface placement applications. We present an analytical technique for kilohertz rate manipulation of CAD models with virtual surface and trimming constraints. The optimization approach allows best placement and sensitivity analysis for mechanical design objectives and parametric domain objectives. Such objectives are not readily incorporated into previous interactive methods. Force feedback is rendered to the user using previously developed haptics principles.

Interactive Mechanical Design Variation for Haptics and CAD

A fast design variation technique for mechanical systems is presented. It is used to interactively optimize mechanical characteristics while “self‐assembling” or satisfying large systems of mechanical constraints. The high speed method is central to providing inverse dynamics force feedback in haptics and control applications. Performance advantages with the use of augmented coordinates for inverse dynamics of closed loop topologies are also noted. The interaction framework allows manipulation of complex assemblies while maintaining kinematically admissible configurations though linkage and joint limit constraints. Furthermore, design variables such as link length can be treated as free variables and optimized to meet design criteria such as assembly dexterity. Assemblies with flexible bodies fit naturally within this framework. Thus, the contribution of this paper is the advancement of techniques in augmented coordinates for the kinematic and force feedback interaction with virtual mechanical assembly design optimization at force control rates.