Online contact point estimation for uncalibrated tool use

Abstract

One of the big challenges for robots working outside of traditional industrial settings is the ability to robustly and flexibly grasp and manipulate tools for various tasks. When a tool is interacting with another object during task execution, several problems arise: a tool can be partially or completely occluded from the robot's view, it can slip or shift in the robot's hand -thus, the robot may lose the information about the exact position of the tool in the hand. Thus, there is a need for online calibration and/or recalibration of the tool. In this paper, we present a model-free online tool-tip calibration method that uses force/torque measurements and an adaptive estimation scheme to estimate the point of contact between a tool and the environment. An adaptive force control component guarantees that interaction forces are limited even before the contact point estimate has converged. We also show how to simultaneously estimate the location and normal direction of the surface being touched by the tool-tip as the contact point is estimated. The stability of the the overall scheme and the convergence of the estimated parameters are theoretically proven and the performance is evaluated in experiments on a real robot.

Dexterous manipulation with compliant grasps and external contacts

“…We showed that, for scenarios where it is reasonable to assume that the grasping point of the end-effector offers some compliance around a rotational axis, the orientation of the grasped object is controllable independently of the end-effector orientation. This is a significant distinction from typical manipulation tasks where a perfectly rigid grasp is assumed [26]- [28].…”

SupraPeds: Smart staff design and terrain characterization

“…In hazardous environments where SupraPed operates, the terrain is complex with few flat surfaces. In such cases, surface normal estimation methods that require comparatively long surface travel [26] are not applicable. • The constraints in control are flexible.…”

“…Intrinsic tactile sensing methods [24] can be used to find the contact surface normal but require a 6DOF F/T sensor and staff tip with a sufficiently large, known convex shape. Methods using only end-effector position and force sensors have been developed to measure surface normal [25,26]. However, precise control of the end-effector is required, including sliding along the surface with a fixed orientation and force, which is difficult to achieve when manipulating a long staff.…”

Learning a tool's homogeneous transformation by tactile-based interaction

“…Bicchi [3] proposed a contact position estimation method in which a known fingertip interacts with an unknown object based on the soft finger contact model using measurement from an intrinsic force and torque sensor. Yiannis [10] extended this approach to not only estimate the translation but the contacted plane's normal direction. Intrinsic haptic based method has been widely used in learning a tip-shaped tool's offset.…”