This paper presents a framework to compute stable contact interfaces for automatically designing customized jigs used in bone surgeries. Given the surface model of a bone represented by polygonal meshes, we find out a small region on the surface to be used as the interface of a customized jig so that it can be stably fixed on the bone under a directional clamping force. The variation of directions on the clamping force is allowed in our formulation. Moreover, the surface region serves as the interface of stable contact must also be disassemblable so that the jig and the bone can be separated after removing the clamping force. The analysis of stable contact is formulated on a Gaussian map by the common regions of half-spaces according to the motion restrictions. A flooding algorithm is proposed to determine those disassemblable and stable contact interfaces on the surface of a bone, where the contact surfaces are later converted into the solid model of a jig to be fabricated by additive manufacturing. Experimental tests are taken to verify the stable contact between a bone and the jig generated by our approach.

In this paper, we present a low-cost IMU-based system, Pedalvatar, which can capture the full-body motion of users in real-time. Unlike the prior approaches using the hip-joint as the root of forward kinematic model, a foot-rooted kinematic model is developed in this work. A state change mechanism has also been investigated to allow dynamically switching the root of kinematic trees between the left and the right foot. Benefitted from this, full-body motions can be well captured in our system as long as there is at least one static foot in the movement. The `floating' artifact of hip-joint rooted methods has been eliminated in our approach, and more complicated motions such as climbing stairs can be successfully captured in real-time. Comparing to those vision-based systems, this IMU-based system provides more flexibility on capturing outdoor motions that are important for many robotic applications.