1,025 research outputs found
Experimental Validation of Contact Dynamics for In-Hand Manipulation
This paper evaluates state-of-the-art contact models at predicting the
motions and forces involved in simple in-hand robotic manipulations. In
particular it focuses on three primitive actions --linear sliding, pivoting,
and rolling-- that involve contacts between a gripper, a rigid object, and
their environment. The evaluation is done through thousands of controlled
experiments designed to capture the motion of object and gripper, and all
contact forces and torques at 250Hz. We demonstrate that a contact modeling
approach based on Coulomb's friction law and maximum energy principle is
effective at reasoning about interaction to first order, but limited for making
accurate predictions. We attribute the major limitations to 1) the
non-uniqueness of force resolution inherent to grasps with multiple hard
contacts of complex geometries, 2) unmodeled dynamics due to contact
compliance, and 3) unmodeled geometries dueto manufacturing defects.Comment: International Symposium on Experimental Robotics, ISER 2016, Tokyo,
Japa
Prehensile Pushing: In-hand Manipulation with Push-Primitives
This paper explores the manipulation of a grasped object by pushing it against its environment. Relying on precise arm motions and detailed models of frictional contact, prehensile pushing enables dexterous manipulation with simple manipulators, such as those currently available in industrial settings, and those likely affordable by service and field robots. This paper is concerned with the mechanics of the forceful interaction between a gripper, a grasped object, and its environment. In particular, we describe the quasi-dynamic motion of an object held by a set of point, line, or planar rigid frictional contacts and forced by an external pusher (the environment). Our model predicts the force required by the external pusher to “break” the equilibrium of the grasp and estimates the instantaneous motion of the object in the grasp. It also captures interesting behaviors such as the constraining effect of line or planar contacts and the guiding effect of the pusher’s motion on the objects’s motion. We evaluate the algorithm with three primitive prehensile pushing actions—straight sliding, pivoting, and rolling—with the potential to combine into a broader in-hand manipulation capability.National Science Foundation (U.S.). National Robotics Initiative (Award NSF-IIS-1427050)Karl Chang Innovation Fund Awar
Dexterous Manipulation Graphs
We propose the Dexterous Manipulation Graph as a tool to address in-hand
manipulation and reposition an object inside a robot's end-effector. This graph
is used to plan a sequence of manipulation primitives so to bring the object to
the desired end pose. This sequence of primitives is translated into motions of
the robot to move the object held by the end-effector. We use a dual arm robot
with parallel grippers to test our method on a real system and show successful
planning and execution of in-hand manipulation
A two-phase gripper to reorient and grasp
This paper introduces the design of novel two-phase fingers to passively reorient objects while picking them up. Two-phase refers to a change in the finger-object contact geometry, from a free spinning point contact to a firm multipoint contact, as the gripping force increases. We exploit the two phases to passively reorient prismatic objects from a horizontal resting pose to an upright secure grasp. This problem is particularly relevant to industrial assembly applications where parts often are presented lying on trays or conveyor belts and need to be assembled vertically. Each two-phase finger is composed of a small hard contact point attached to an elastic strip mounted over a V-groove cavity. When grasped between two parallel fingers with low gripping force, the object pivots about the axis between the contact points on the strips, and aligns upright with gravity. A subsequent increase in the gripping force makes the elastic strips recede into the cavities letting the part seat in the V-grooves to secure the grasp. The design is compatible with any type of parallel-jaw gripper, and can be reconfigured to specific objects by changing the geometry of the cavity. The two-phase gripper provides robots with the capability to accurately position and manipulate parts, reducing the need for dedicated part feeders or time-demanding regrasp procedures.National Science Foundation (U.S.). National Robotics Initiative (NSF-IIS-1427050
Visual Tactile Sensor Based Force Estimation for Position-Force Teleoperation
Vision-based tactile sensors have gained extensive attention in the robotics
community. The sensors are highly expected to be capable of extracting contact
information i.e. haptic information during in-hand manipulation. This nature of
tactile sensors makes them a perfect match for haptic feedback applications. In
this paper, we propose a contact force estimation method using the vision-based
tactile sensor DIGIT, and apply it to a position-force teleoperation
architecture for force feedback. The force estimation is done by building a
depth map for DIGIT gel surface deformation measurement and applying a
regression algorithm on estimated depth data and ground truth force data to get
the depth-force relationship. The experiment is performed by constructing a
grasping force feedback system with a haptic device as a leader robot and a
parallel robot gripper as a follower robot, where the DIGIT sensor is attached
to the tip of the robot gripper to estimate the contact force. The preliminary
results show the capability of using the low-cost vision-based sensor for force
feedback applications.Comment: IEEE CBS 202
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