Abstract In this paper dealing with the problem of stable grasping of a rigid and rectangular object with two robotic fingers with soft tips, we consider the case of rolling fingertips under a soft contact motion model which leads to... more
Abstract In this paper dealing with the problem of stable grasping of a rigid and rectangular object with two robotic fingers with soft tips, we consider the case of rolling fingertips under a soft contact motion model which leads to non-holonomic constraints even for the planar case while ...
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SUMMARY There is a large gap between reality and grasp models that are currently available because of the static analysis that characterizes these approaches. This work attempts to fill this need by proposing a control law that, starting... more
SUMMARY There is a large gap between reality and grasp models that are currently available because of the static analysis that characterizes these approaches. This work attempts to fill this need by proposing a control law that, starting from an initial contact state which does not necessarily correspond to an equilibrium, achieves dynamically a stable grasp and a relative finger orientation in the case of pinching an object with arbitrary shape via rolling soft fingertips. Controlling relative finger orientation may improve grasping force manipulability and allow the appropriate shaping of the composite object consisted of the distal links and the object, for facilitating subsequent tasks. The proposed controller utilizes only finger proprioceptive measurements and is not based on the system model. Simulation and experimental results demonstrate the performance of the proposed controller with objects of different shapes.
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This work proposes a kinematic control method for human-robot handshake motions achieving fast motion synchronization given a preset internal robot handshake motion and a compliance level that reflects the robot's level of... more
This work proposes a kinematic control method for human-robot handshake motions achieving fast motion synchronization given a preset internal robot handshake motion and a compliance level that reflects the robot's level of passiveness. The proposed method combines a non-linear dynamic system having an attractive limit cycle with an admittance controller and an adaptation mechanism so that interaction forces are minimized and a consensus oscillation is achieved between the engaging participants. The proposed method is validated by experimenting with a KUKA LWR4+ 7dof arm under various scenarios.
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ABSTRACT A robot hand-over control scheme is proposed achieving human-like haptic interaction during object load transfer from a giver to a receiver hand for the planar case. It is assumed that the object has parallel surfaces and unknown... more
ABSTRACT A robot hand-over control scheme is proposed achieving human-like haptic interaction during object load transfer from a giver to a receiver hand for the planar case. It is assumed that the object has parallel surfaces and unknown mass. The giver initiates the hand-over process while the receiver estimates the transferred object mass adapting its grip force accordingly in a three stage process. The control laws are based on a dynamically stable grasp controller which is modified for the hand-over task. A stable load transfer is securely achieved as shown by the theoretical analysis and illustrated by the simulation results.
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ABSTRACT In this paper a simple tracking controller for a variable stiffness joint is proposed. System dynamics is considered unknown. The controller guarantees link and stiffness motor position performance specifications that have been... more
ABSTRACT In this paper a simple tracking controller for a variable stiffness joint is proposed. System dynamics is considered unknown. The controller guarantees link and stiffness motor position performance specifications that have been apriori set, utilizing full state feedback. Simulation results on the previously published CompAct-VSA joint validate the efficiency of the proposed control approach.
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ABSTRACT This paper proposes a controller for the stable grasp of an arbitrary-shaped object on the horizontal plane by two robotic fingers with rigid hemispherical fingertips. The controller stabilizes the grasp with optimal force angles... more
ABSTRACT This paper proposes a controller for the stable grasp of an arbitrary-shaped object on the horizontal plane by two robotic fingers with rigid hemispherical fingertips. The controller stabilizes the grasp with optimal force angles and desired finger shaping determined through the choice of a control constant without requiring the utilization of any contact information regarding contact locations and contact angles or any estimates of them. Simulation results demonstrate the performance of the proposed controller and show its clear advantages with respect to other known control schemes.
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In this paper, we study two soft spherical fingertips grasping a rigid polygonal object as a kinematically constrained system. We assume that the contact locations of the soft fingertips are not fixed on the object but are able to move... more
In this paper, we study two soft spherical fingertips grasping a rigid polygonal object as a kinematically constrained system. We assume that the contact locations of the soft fingertips are not fixed on the object but are able to move due to rolling constraints. A contact motion model is proposed for soft-rolling fingertips based on previously reported experimental findings on the rolling distance for a variety of soft materials. The equilibrium conditions are derived from the system dynamics and depend on the deformation and on the kind of soft material with regard to the fingertip’s rolling distance characteristics. Also, a discussion on contact forces and a grasp analysis at object’s equilibrium is made. It is shown that using the model of point contact with friction in soft-rolling contacts is not adequate for describing the real system with fingertips of low or medium stiffness characteristics. In general, the equilibrium conditions of the three contacted bodies (soft fingerti...
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IEEE/ASME TRANSACTIONS ON MECHATRONICS (ISSN 1083-4435) is published quarterly by The Institute of Electrical and Electronics Engineers, Inc. Responsibility for the contents rests upon the authors and not the IEEE, the Society/Council, or... more
IEEE/ASME TRANSACTIONS ON MECHATRONICS (ISSN 1083-4435) is published quarterly by The Institute of Electrical and Electronics Engineers, Inc. Responsibility for the contents rests upon the authors and not the IEEE, the Society/Council, or its members. IEEE Corporate Office: 3 Park Avenue, 17th Floor, New York, NY 10016-5997. IEEE Operations Center: 445 Hoes Lane, PO Box 1331, Piscataway, NJ 08855-1331. NJ Telephone:+ 1 732 981 0060. Price/Publication Information: Individual copies: IEEE/ASME members $10.00 ( ...
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Pmceedinp of the 2004 IEEE Internaliorul C onhnnu on RobDtic~ & A mion New Ot!aans, IA Aprll2004 Equilibrium Conditions of a Rigid Object Grasped ... John Fasoulas and Zoe Doulgeri jfasoula@egnatia.ee.auth.gr,... more
Pmceedinp of the 2004 IEEE Internaliorul C onhnnu on RobDtic~ & A mion New Ot!aans, IA Aprll2004 Equilibrium Conditions of a Rigid Object Grasped ... John Fasoulas and Zoe Doulgeri jfasoula@egnatia.ee.auth.gr, doulgeri@vergina.eng.auth.gr Department of Electrical and ...
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Abstract Precise programming of robots for industrial tasks is inflexible to variations and time-consuming. Teaching a kinematic behavior by demonstration and encoding it with dynamical systems that are robust with respect to... more
Abstract Precise programming of robots for industrial tasks is inflexible to variations and time-consuming. Teaching a kinematic behavior by demonstration and encoding it with dynamical systems that are robust with respect to perturbations, is proposed in order to address this issue. Given a kinematic behavior encoded by Dynamic Movement Primitives (DMP), this work proposes a passive control scheme for assisting kinesthetic modifications of the learned behavior in task variations. It employs the utilization of penetrable spherical Virtual Fixtures (VFs) around the DMP’s virtual evolution that follows the teacher’s motion. The controller enables the user to haptically ‘inspect’ the spatial properties of the learned behavior in SE(3) and significantly modify it at any required segment, while facilitating the following of already learned segments. A demonstration within the VFs could signify that the kinematic behavior is taught correctly and could lead to autonomous execution, with the DMP generating the newly learned reference commands. The proposed control scheme is theoretically proved to be passive and experimentally validated with a KUKA LWR4+ robot. Results are compared with the case of using a gravity compensated robot agnostic of the previously learned task. It is shown that the time duration of teaching and the user’s cognitive load are reduced.
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A web-based virtual robot task simulator has been developed and used in the teaching of robotics through lab demonstrations and a set of lab assignments. The simulator allows a high degree of real time interaction with a virtual robot... more
A web-based virtual robot task simulator has been developed and used in the teaching of robotics through lab demonstrations and a set of lab assignments. The simulator allows a high degree of real time interaction with a virtual robot that can be commanded to perform a number of pick and place operations on virtual objects replicating an existing industrial robot manipulator. A unique characteristic of the system is that, apart from using high level robot motion commands like the real robot, it allows a simplified graphical input of target positions and orientations to define a gripper path. It also encourages interaction and collaborative problem solving. Empirical evidence shows that the effectiveness of the learning program is increased by the enhanced motivation and interest of the students and through their improved learning capabilities.
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The problem of robot force and position trajectory tracking is revisited in the case of an uncertain mapping of a surface into the robot space; then, although it is possible to define the desired trajectories with respect to the... more
The problem of robot force and position trajectory tracking is revisited in the case of an uncertain mapping of a surface into the robot space; then, although it is possible to define the desired trajectories with respect to the constraint surface, the lack of knowledge of the constraint direction in the robot space, means that the position and force control
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... Ianais Loizidis and Zoe Doulgeri Dept. of Electrical and Computer Engi~ieering, Aristotle University of Thessaloniki, 54006 Thessaloniki, Greece. ... which holds for at least the following choice of H : H =Vc where c =(pl+p2)/2 and... more
... Ianais Loizidis and Zoe Doulgeri Dept. of Electrical and Computer Engi~ieering, Aristotle University of Thessaloniki, 54006 Thessaloniki, Greece. ... which holds for at least the following choice of H : H =Vc where c =(pl+p2)/2 and pl,, p2 the max and, min eigenvalues of H. ...
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ABSTRACT In robot constrained motion problems with frictional contacts, uncertainties on the contacted surface slope distort control targets and affect the control system performance. The surface normal direction cosines are in this case... more
ABSTRACT In robot constrained motion problems with frictional contacts, uncertainties on the contacted surface slope distort control targets and affect the control system performance. The surface normal direction cosines are in this case uncertain parameters that are involved in both the control law and the control targets. This work proposes an adaptive controller that achieves the desired goal given a persistently excited tip velocity magnitude on the surface by achieving the convergence of the estimated direction parameters to their actual values. The controller requires measurements of total force and joint variables. A simulation example for a 6 d.o.f. robot is used to illustrate the theoretical results.
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ABSTRACT In this paper a novel type of tracking controller for flexible joint robots is proposed. Joint elasticity is considered unknown and may be time varying. Robot and motor dynamics are also considered unknown. The controller... more
ABSTRACT In this paper a novel type of tracking controller for flexible joint robots is proposed. Joint elasticity is considered unknown and may be time varying. Robot and motor dynamics are also considered unknown. The controller guarantees link position performance specifications that have been a-priori set utilizing full state feedback. Simulation on a two link flexible joint robot validate the efficiency of the proposed control approach.
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In this work, we consider the force and position trajectory tracking for a robot manipulator in compliant contact with a surface in the presence of unknown stiffness and dynamic friction. A novel neuro-adaptive controller is proposed that... more
In this work, we consider the force and position trajectory tracking for a robot manipulator in compliant contact with a surface in the presence of unknown stiffness and dynamic friction. A novel neuro-adaptive controller is proposed that exploits the approximation capabilities of the linear in the weights neural networks and the uniform ultimate boundedness of force and position error is
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ABSTRACT A prescribed performance regulator for the generalized position of the robot arm endpoint in the task space is proposed. The control input which incorporates a transformed error guarantees a prescribed performance regarding the... more
ABSTRACT A prescribed performance regulator for the generalized position of the robot arm endpoint in the task space is proposed. The control input which incorporates a transformed error guarantees a prescribed performance regarding the response of the endpoint generalized position error. The use of two different forms of this transformed error will be presented and compared. Mathematical proof of the controller's success in fulfilling the desired goals is given. A simulation of a three degrees of freedom robot is used to confirm the theoretical findings for both cases of the transformed error.