Rodney G. Roberts

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When a manipulator suuers a joint failure, its performance can be signiicantly affected. If the failed joint is locked, the resulting manipulator Jacobian is given by the original Jacobian, except that the column associated with the failed joint is removed. The rank of the resulting Jacobian then determines if the manipulator still has the ability to(More)
We study the uncertainties in parton distributions, determined in global fits to deep inelastic and related hard scattering data, due to so-called theoretical errors. Amongst these, we include potential errors due to the change of perturbative order (NLO→ NNLO), ln(1/x) and ln(1 − x) effects, absorptive corrections and higher-twist contributions. We(More)
We perform a global parton analysis of deep inelastic and related hard-scattering data, including O(αQED) corrections to the parton evolution. Although the quality of the fit is essentially unchanged, there are two important physical consequences. First, the different DGLAP evolution of u and d type quarks introduces isospin violation, i.e. u 6= d, which is(More)
We propose a more physical parameterization of the gluon distribution for global parton analyses of deep inelastic and related hard scattering data. In the new parameterization the gluon distribution at large x in the MS-scheme is driven by the valence quarks, which naturally produces a shoulder-like form at high x, and hence produces a better description(More)
In this paper, the authors examine the problem of designing nominal manipulator Jacobians that are optimally fault tolerant to one or more joint failures. Optimality is defined here in terms of the worst-case relative manipulability index. While this approach is applicable to both serial and parallel mechanisms, it is especially applicable to parallel(More)
We use all the available new precise data for deep inelastic and related hard scattering processes to perform NLO global parton analyses. These new data allow an improved determination of partons and, in particular, the inclusion of the recent measurements of the structure functions at HERA and of the inclusive jets at the Tevatron help to determine the(More)
In environments that are remote and hazardous, tasks such as repairing and maintaining a robot manipulator can be extremely difficult and costly. Under such conditions, the operational reliability of a robotic system is very important and motivates the problem of designing optimally fault-tolerant manipulators. One solution to increasing the fault tolerance(More)