Task-level Dexterous Manipulation with Multifingered Hand Under Modeling Uncertainties

This article presents an approach to efficiently control grippers/multifingered hands for dexterous manipulation according to a task, i.e. a predefined trajectory in the object space. The object motion is decomposed using a basis of predefined object motions equivalent to object-level coordinates couplings and leading to the definition of the task-level space. In the proposed approach, the decomposition of the motion in the task space is associated with a robust control design based on Linear Matrix Inequalities (LMIs) and Bilinear Matrix Inequalities (BMI). Eigenvalue placement ensures the robustness of the system to geometric uncertainties and eigenvector placement decouples the system according to task specifications. A practical evaluation of the proposed control strategy is provided with a two-fingers and six-DoFs robotic system manipulating an object in the horizontal plane. Results show a better trajectory tracking and the robustness of the control law according to geometric uncertainties and the manipulation of various objects.

Origami Folding by Multifingered Hands with Motion Primitives

Origami, a traditional Japanese art, is an example of superior handwork produced by human hands. Achieving such extreme dexterity is one of the goals of robotic technology. In the work described in this paper, we developed a new general-purpose robot system with sufficient capabilities for performing Origami. We decomposed the complex folding motions into simple primitives and generated the overall motion as a combination of these primitives. Also, to measure the paper deformation in real-time, we built an estimator using a physical simulator and a depth camera. As a result, our experimental system achieved consecutive valley folds and a squash fold.

Workspace of Multifingered Hands Using Monte Carlo Method

Multifingered hands have the capability of dexterous manipulation of grasped objects and thus significantly increase the capabilities of a robot equipped with multifingered hands. Inspired by a multijointed human finger and the hand, we propose a six degree-of-freedom (DOF) model of a three-fingered robotic hand as a parallel manipulator. Two kinds of contact, namely point contact with friction and rolling without slipping between the fingertips and the grasped object, are considered. The point contact with friction is modeled as a three DOF spherical joint, and for rolling without slipping, we use the resultant nonholonomic constraints between the grasped object and the fingers. With realistic limits on the joints in the fingers and dimensions of finger segments, we obtain the well-conditioned manipulation workspace of the parallel manipulator using a Monte Carlo-based method. Additionally, we present two new general results—it is shown that maximum position and orientation workspace is obtained when the cross-sectional area of the grasped object is approximately equal to the area of the palm of the hand and when rolling without slipping is ensured the size of the well-conditioned workspace is significantly larger (∼1.2–1.5 times). We also present representative experiments of manipulation by a human hand and show that the experimental results are in reasonable agreement with those obtained from simulations.

Dimensional Synthesis of Wristed Binary Hands

The kinematic synthesis applied to tree topologies is a tool for the design of multifingered robotic hands, for a simultaneous task of all fingertips. Even though traditionally wrists and hands have been designed separately, the wrist usually being part of the robot manipulator arm, it makes sense to consider the wrist as a part of the hand, as many grasping and manipulation actions are a coordinated action of wrist and fingers. The manipulation capabilities of robotic hands may also be enhanced by considering more than one splitting stage, as opposed to the single-palm traditional hand. In this work, we present the dimensional synthesis for a family of multifingered hands, the binary hands, which have a 2R wrist and several splitting stages, each of them spanning two branches consisting of a revolute joint for each edge. For these topologies, it is proved that a three-position task can be defined for each fingertip, regardless of the number of fingers. One example is presented to show the possible design strategies and uses for this family of hands.