Classical grasp quality metrics assume one deterministic friction coefficient and therefore cannot assess whether a grasp maintains force closure across plausible friction values. We present FIRMGrasp, a family of grasp quality metrics that incorporates friction uncertainty through Conditional Value-at-Risk (CVaR). At confidence level
β, we evaluate the force-closure margin at the mean of the adverse friction tail. This evaluation defines the risk-adjusted margin
ε(β), the inscribed-ball radius of the corresponding grasp wrench space. We prove that
ε(β) varies monotonically with
β, remains differentiable in the grasp parameters, and certifies that any grasp with
ε(β)>0 achieves force closure with probability at least
β. Across 1,599 LEAP Hand and Allegro Hand grasps,
ε(β) identifies friction-sensitive grasps that receive high nominal Ferrari-Canny scores, and 53% of the nominally force-closed grasps lose closure in the adverse friction tail. The nominal margin ranks a successful grasp above a failed grasp with probabilities of only 0.53 in the shake test and 0.67 in the pick test, whereas
ε(β) achieves 0.63 and 0.78. At an adverse friction coefficient of 0.2, 70% of grasps with positive
ε(β) withstand a simulated lift and lateral pull, compared with 25% of grasps with positive nominal margin and nonpositive
ε(β). We also synthesize grasps with positive
ε(β) for the RealHand L6 and LEAP Hand, both of which retain the object during adverse-friction lifts. In MuJoCo trials with the RealHand L6, 95% of grasps that establish contact and have positive
ε(β) retain the object at the same adverse friction coefficient.
Clinton Enwerem, John S. Baras, Calin Belta