Modeling of needle insertion forces for robot-assisted percutaneous therapy

Force information from needle insertions was measured and modeled for use in robot-assisted percutaneous therapies. Data was collected on bovine livers using the Johns Hopkins University Steady Hand Robot, and modeled in three parts: force due to capsule stiffness, friction, and cutting. Capsule stiffness is modeled by a nonlinear spring model, friction by a modified Karnopp model, and cutting by the remaining forces, which appear to be constant for a given tissue sample. During robot-assisted procedures, real-time force data can be compared to these models to control puncture of interior structures.