1,721,011 research outputs found
Review of the Literature on Time-Optimal Control of Robotic Manipulators
No full textA task that robotic manipulators most frequently perform is motion between specified points in the working space. It is therefore important that these motions are efficient. The presence of the obstacles and other requirements of the task often require that the path is specified in advance. Robot actuators cannot generate unlimited forces/torques so it is reasonable to ask how to traverse the prespecified path in minimum time so that the limits on the actuator torques are not violated. It can be shown that the motion which requires least time to traverse a path requires at least one actuator to operate on the boundary (maximum or minimum). Furthermore, if the path is parameterized, the equations describing the robot dynamics can be rewritten as functions of the path parameter and its first and second derivatives. In general, the actuator bounds will be transformed into the bounds on the acceleration along the path. These bounds will be functions of the velocity and position. It is poss..
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Metrics and Connections for Rigid Body Kinematics
No full textThe set of rigid body motions forms the Lie group SE(3), the special Euclidean group in three dimensions. In this paper we investigate Riemannian metrics and affine connections on SE(3) that are suited for kinematic analysis and robot trajectory planning. In the first part of the paper, we study metrics whose geodesics are screw motions. We prove that no Riemannian metric can have such geodesics and we show that metrics whose geodesics are screw motions form a two-parameter family of semi-Riemannian metrics. In the second part of the paper we investigate affine connections which through the covariant derivative give the expression for the acceleration of a rigid body that agrees with the expression used in kinematics. We prove that there is a unique symmetric connection with this property. Further, we show that there is a family of Riemannian metrics that are compatible with such a connection. These metrics are products of the bi-invariant metric on the group of rotations and a positiv..
Energy-based 6-DOF penetration depth computation for penalty-based haptic rendering algorithms
No full textFinite state machine (FMS) addressable MEMS microrobots: a new paradigm for controlling large numbers of mems microrobots
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