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Icra2015 interactive presentation - Evaluation of Finger Configuration for Partial Caging
- 1. Evaluation of Finger Configuration for Partial Caging *Satoshi Makita (NIT, SaseboCollege, Japan) Kazuyuki Nagata (AIST, Japan) The 2015 IEEE Int. Conf. on Robotics and Automation, 29/May/2015, Grasping II
- 2. Partial Caging? Incomplete confinement • Caging: a geometrical capturing by robots in position-controlled. • The captured object can escape from the hand, but it is difficult. • Taking advantage for robot hands with mechanical restriction. Objective • To determine robot configuration that prevent the object well from escaping (Complete) Caging Partial Caging Evaluation of Finger Configuration for Partial Caging
- 3. Summary Evaluating efficient configuration of robot hand • For capturing objects and confining them geometrically Evaluation indexes: • Difficulty of escaping from the hand • Ease of entering the hand Results • Suitable finger posture is present Which hand posture is suitable? Fish trap Evaluation of Finger Configuration for Partial Caging
- 4. Evaluation indexes Assumption • Two-fingered planar hand Elapsed time • How long time does it take to escape? • How long time does it take to enter? Evaluation of Finger Configuration for Partial Caging
- 5. Evaluation results (index score) = The time to escape from the hand The time to enter the hand 0 1 2 3 4 5 6 7 -80 -60 -40 -20 0 20 40 60 80 escapingtime/enteringtime angle of the gate [deg] r=0.01Lp r=0.05Lp r=0.1Lp Suitable Fingertip angle Evaluation of Finger Configuration for Partial Caging
- 6. More results • Changing the size of the object • Changing the angle of the fingertips • Changing the width between fingertips Let’s discuss at the display #1 Evaluation of Finger Configuration for Partial Caging
- 7. Evaluation of Finger Configuration for Partial Caging / *S. Makita (NIT, Sasebo Coll., Japan) and K. Nagata (AIST, Japan) Summary Evaluating efficient configuration of robot hand • For capturing objects and confining them geometrically (without any force sensing and control) Evaluation indexes: • Difficulty of escaping from the hand (DoEs) • Ease of entering the hand (EoEn) Assumption • Two-fingered planar hand Simulation Results • DoEs decreases corresponding to the width between the fingertips • EoEn seldom changes at a certain range of angle of the fingertips Which hand posture is good for confinement? Fish trap Partial caging = Incomplete confinement • Caging: a geometrical capturing by robots even in position- controlled. • The captured object can escape from the hand, but it is difficult. =The object can enter the hand. • Available for robot hands with mechanical restriction. Advantages of using Geometrical Features • Easier strategies to grasp objects (e.g. ring-shape) • As fault-tolerance system when grasp contacts break (Complete) Caging Partial Caging 0 50 100 150 200 250 300 350 400 450 500 -80 -60 -40 -20 0 20 40 60 80 timeuntiltheobjectescaped[s] angle of the gate [deg] r=0.01Lp r=0.05Lp r=0.1Lp Simulation result: Ease of entering 0 50 100 150 200 250 300 350 400 -80 -60 -40 -20 0 20 40 60 80 timeuntiltheobjectentered[s] the angle of the gate [deg] r=0.01Lp r=0.05Lp r=0.1Lp Simulation result: Partial caging quality 0 1 2 3 4 5 6 7 -80 -60 -40 -20 0 20 40 60 80 escapingtime/enteringtime angle of the gate [deg] r=0.01Lp r=0.05Lp r=0.1Lp Simulation result: Difficulty of escaping The difficulty of escaping increasing corresponding to the width of the fingertips The difficulty of entering increases corresponding to the width of the fingertips, except the smaller angle of the fingertips than 10 [deg] Changing the index score corresponding to the width of the fingertips, and there exists a peak of the index score from 10 to 20 [deg]
- 8. Evaluation of Finger Configuration for PartialCaging / *S. Makita (NIT, Sasebo Coll., Japan) and K. Nagata (AIST, Japan) Related Works Using Geometrical Features • Grasping a flat-shaped object by lateral pinching [Kosuge BioRob 2008] • Grasping Objects with Holes [Pokorny ICRA2013] • Gravity caging [Jiang ICRA2012] • Complete caging • 2D by planar fingertips: [Rimon IJRR 1999] and more • 3D by multifingered hand [Diankov Humanoids2008] Partial caging • Evaluating the quality of partial caging by probabilistic approaches [Makapunyo et al. ICRA2013] Our research focuses on • Partial caging by a multifingered hand • Evaluating quality of partial caging depending on the posture of the hand Gravity Partial caging The constrained object can escape form incomplete surrounding = It can enter the semi-closed region Fish trap Anisotropy of constraint Is it possible to acquire an ability of grasping without any finger control? Motivation of applying partial caging • To take advantage of geometrical constraint • To apply caging grasps to robot hands with mechanical restriction • To explorer the ability of confining an object without any control feedback Simulation results • Changing angle of the fingertips • Discussion on effect of the angle to facilitate the object to escape ●：Initial position of object ●：Fingers ●：Locus of moving object
- 9. Evaluation of Finger Configuration for PartialCaging / *S. Makita (NIT, Sasebo Coll., Japan) and K. Nagata (AIST, Japan) Evaluation settings The robot hand • Looks like a semi-closed box with a door • The planar robot hand is manipulated randomly by a 2 DOF manipulator Evaluation indexes: • Difficulty of escaping from the hand (DoEs) • Ease of entering the hand (EoEn) Simulation settings • The average elapsed time is calculated from 5,000 times • The gate (fingertips) is closing when the angle is positive, and vise versa Difficulty of escaping Ease of Entering Robot hand Gate setting Simulation Result ●：Initial position of object ●：Fingers,Walls ●：Locus of moving object Partial caging • Caging: a geometrical capturing by robots even in position-controlled. • The captured object can escape from the hand, but it is difficult. =The object can enter the hand. • Available for robot hands with mechanical restriction. Advantages of using Geometrical Features • Easier strategies to grasp objects (e.g. ring- shape) • As fault-tolerance system when grasp contacts break
- 10. Evaluation of Finger Configuration for PartialCaging / *S. Makita (NIT, Sasebo Coll., Japan) and K. Nagata (AIST, Japan) Two factors affecting the evaluation scores Retention of the object and getting over the gate • The object tends to stay at the foot of the fingertip when the angle of the fingertip is negative Width of the goal (gap between fingertips) • The width of goal entrance decreases according to the angle of the fingertips
Editor's Notes
- In this research, we focus on evaluation of robot hand configuration for a geometric strategy to capture an object. (We investigated which posture of the hand is suitable to confine the object without any finger motion.)
- (I explain you what is partial caging. Partial caging can be defined as an incomplete confinement by robots. As some of you know, caging is a geometrical capturing strategy by robots, where position-controlled robots surround the object. The geometrical constraint has some advantages for robotic manipulation as supplement of force closure grasp, but complete caging is sometimes difficult for robot hands to achieve due to mechanical limitation. Thus, we consider PARTIAL caging to take advantages of geometrical constraints for such robot hands, (as incomplete confinement.) m
- (This is a summary of our presentation.) We evaluate efficient configuration of robot hand for capturing. For example, seeing these figure, a circular object is partially confined in the planar hand, and it can move inside the hand. And then, we’d like to know which hand posture is suitable for confinement without any finger motion, that is, when the robot hand is (assumed to be) in position-controlled. This situation is similar to fish traps, (which has a tapered gate and a fish can pass through here. According to the character of the fish, a certain direction of passing facilitate fishes to enter the opening. On the other hand, the opposite direction makes it difficult for fishes to escape from the trap passing through the gap. It suggests that robot hands like fish traps could acquire such ability to make objects almost inescapable without any control and sensing. We propose two scores as evaluation indexes: one is difficulty of escaping from the hand. It has been already presented in other previous works on caging and partial caging. And another is ease of entering the semi-closed region. As a results, we can find that a suitable finger posture is present. that represents how easy does the object in free movement enter inside the robot hand through the gap of the fingers.
- As an introduction of partial caging, we consider a two-fingered planar robot hand like that. The evaluation index can be defined as the elapsed time to escape from the semi-closed confinement. (And we introduce two index scores: one denotes the time that the object elapses to escape from the hand,) and another is elapsed time to enter the hand from a certain limited region drawn by the dots line.
- The evaluation score of partial caging quality can be defined as this division. We tried 5,000 times simulations for each hand posture and evaluated how difficult the object can pass through the gap. As a results, fingertip angle with about 10 deg like that figure is suitable to snap and capture the object. These two scores lead an evaluation index for partial caging. When the score is high, the form of the robot hand is assumed to be suitable to capture the object and prevent it from escaping even without any control feedback.
- We have more results with changing the parameters of the simulation. We’d like to discuss with you on the concept of partial caging by robot hands and our results.