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Bohg J.,Systems In Motion | Morales A.,Jaume I University | Asfour T.,Karlsruhe Institute of Technology | Kragic D.,KTH Royal Institute of Technology
IEEE Transactions on Robotics

We review the work on data-driven grasp synthesis and the methodologies for sampling and ranking candidate grasps. We divide the approaches into three groups based on whether they synthesize grasps for known, familiar, or unknown objects. This structure allows us to identify common object representations and perceptual processes that facilitate the employed data-driven grasp synthesis technique. In the case of known objects, we concentrate on the approaches that are based on object recognition and pose estimation. In the case of familiar objects, the techniques use some form of a similarity matching to a set of previously encountered objects. Finally, for the approaches dealing with unknown objects, the core part is the extraction of specific features that are indicative of good grasps. Our survey provides an overview of the different methodologies and discusses open problems in the area of robot grasping. We also draw a parallel to the classical approaches that rely on analytic formulations. © 2013 IEEE. Source

Leitch J.,University of Oxford | Stebbins J.,Nuffield Orthopaedic Center | Paolini G.,Systems In Motion | Zavatsky A.B.,University of Oxford
Gait and Posture

This paper presents a comparison of four different methods of identifying the times of foot-strike and toe-off during running based on gait marker trajectories. The event times predicted by the methods were compared to those identified using a force plate for both over-ground and treadmill running. The effect of using different threshold values for the detection of gait events using force plate data was also investigated, and as a result, all assessments of event detection accuracy were based on a cut-off value of 10. N. The most accurate method of foot-strike detection depended on whether the runner landed with a rear- or a mid-foot strike. For rear-foot-strike running, the best method of identifying foot-strike used the vertical acceleration profile of the posterior heel distal marker and the vertical position profile of the hallux marker. For mid-foot-strike running, the best method of identifying foot-strike used the vertical velocity profile of the mean positions of the posterior heel distal marker and a marker midway between the second and third metatarsal heads. The most accurate method of identifying toe-off did not depend on type of foot-strike and was based on the vertical acceleration and position profiles of the hallux marker. © 2010 Elsevier B.V. Source

Kabus S.,Systems In Motion | Pedersen C.B.W.,FE DESIGN
Journal of Tribology

The internal load distribution in rolling bearings has a high impact on the bearing fatigue life. This study presents a method to optimize roller bearing housing design in order to maximize the bearing fatigue life by ensuring an optimal internal load distribution. An FE-model of a cylindrical roller bearing utilizing nonlinear springs in the roller modeling is presented, which is capable of simulating the bearing load distribution efficiently. The optimal load distribution is achieved by specifying the desired internal load distribution as design constraints in a topology optimization of the bearing housing design. The superiority of the method is clearly demonstrated through case studies involving a cylindrical roller bearing, where it is shown that the fatigue life is increased and the bearing housing mass and roller contact misalignment is reduced. © 2012 American Society of Mechanical Engineers. Source

Kabus S.,Systems In Motion | Hansen M.R.,University of Agder | Mouritsen O.,University of Aalborg
Journal of Tribology

The accuracy of the fatigue life calculations in rolling bearing simulations is highly dependent on the precision of the roller-raceway contact simulations. Several different methods exist to simulate these pressure distributions and in time domain bearing simulations, where many contacts need evaluation, the simple and time efficient methods are more popular, yielding erroneous life estimates. This paper presents a new six degree of freedom frictionless quasi-static time domain cylindrical roller bearing model that uses high precision elastic half-space theory to simulate the contact pressures. The potentially higher computational demand using the advanced contact calculations is addressed by preprocessing a series of contacts at different centerline approaches and roller tilt angles, which are used for interpolating contact results during time domain simulations. It is demonstrated that this new model allows for simulation of bearing misalignments, roller centrifugal forces, and flange contact induced roller tilt moments, and that the effect of these conditions is directly evaluated in a detailed fatigue life analysis. Finally, the stiffness of the bearing model is validated against existing experimental data with good correlation. © 2012 American Society of Mechanical Engineers. Source

Systems In Motion | Date: 2013-12-03

A motion simulation system includes actuators having a planetary gearbox engaged with and driven by a servomotor engaged with a crank. A connector rod has a proximal end engaged with the crank of each actuator, and a distal end engaged with a top plate configured to attach to a platform assembly. A control system is operable with each electric servo motor of each actuator for delivering control for providing a simulated motion to the top plate. Control data is sent to the servomotors using a msec data send and receive rate, with internal processing within the nano-second range. Such update rates coupled with a real time, dynamically responsive motion controller results in a desirably smooth and accurate simulator motion. The control system includes a washout filter for transforming input forces and rotational movements. One to six degrees of freedom systems having smooth performance with high payload capability are provided.

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