Abstract-Computer vision researchers have proved the feasibility of camera self-calibration -the estimation of a camera's internal parameters from an image sequence without any known scene structure. Various self-calibration algorithms have been published. Nevertheless, all of the recent sequential approaches to 3D structure and motion estimation from image sequences which have arisen in robotics and aim at real-time operation (often classed as visual SLAM or visual odometry) have relied on pre-calibrated cameras and have not attempted online calibration.In this paper, we present a sequential filtering algorithm for simultaneous estimation of 3D scene estimation, camera trajectory and full camera calibration from a sequence of fixed but unknown calibration. This calibration comprises the standard projective parameters of focal length and principal point along with two radial distortion coefficients. To deal with the large non-linearities introduced by the unknown calibration parameters, we use a Sum of Gaussians (SOG) filter rather than the simpler Extended Kalman Filter (EKF).To our knowledge, this is the first sequential Bayesian autocalibration algorithm which achieves complete fixed camera calibration using as input only a sequence of uncalibrated monocular images. The approach is validated with experimental results using natural images, including a demonstration of loop closing for a sequence with unknown camera calibration.

250 word max) Aim: Individuals who require manual wheelchairs after stroke are typically taught to ambulate with compensatory propulsion (i.e. using their nonparetic arm and foot), risking disuse of the paretic arm. We investigated whether stroke survivors can instead ambulate in a bimanual, leverdriven wheelchair that requires the paretic arm to contribute half the propulsive input.Methods: Seventeen individuals with chronic stroke and severe hemiparesis (upper extremity Fugl-Meyer scores between 10 and 24) participated across two experiments. In the first experiment participants (n=12) ambulated in straight paths. In the second experiment participants (n=12) also performed turns, using an improved version of the wheelchair that incorporated handbrakes.Twelve unimpaired controls also completed the second experiment. Motion capture and EMG were used to compare biomechanics between groups.Results: Altogether, 15 of 17 participants with stroke could ambulate 30 m in straight paths, and 9 of 12 could turn 1800° entirely under the power of their paretic arm. Participants with stroke exhibited largely healthy biomechanics, with minimal shoulder hiking/leaning or trunk inclination.Their arm muscle EMG patterns were similar to those used by unimpaired participants, excepting delayed elbow extensor activation.Conclusions: Individuals with severe arm impairment in the chronic stage of stroke retain sufficient strength and coordination with their paretic arm to maneuver bimanual, lever-driven wheelchairs. We suggest bimanual, lever driven propulsion should be explored in stroke rehabilitation practice as an alternative to compensatory wheelchair propulsion, as it has the potential to exercise healthy movement synergies, which may in turn help drive use-dependent motor recovery.

The results show the feasibility of neuromusculoskeletal model self-calibration. This study will contribute to a better understanding of the generalization of muscle models for subject-specific rehabilitation therapies. Moreover, this work is very promising for rehabilitation devices such as electromyography-driven exoskeletons or prostheses.

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Rehabilitation exercises cause fatigue because tasks are repetitive. Therefore, inevitable human motion performance changes occur during the therapy. Although traditionally fatigue is considered an event that occurs in the musculoskeletal level, this paper studies whether fatigue can be regarded as context that influences lower-dimensional motor control organization and coordination at neural level. Non Negative Factorization Matrix (NNFM) and Detrended Fluctuations Analysis (DFA) are the tools used to analyze the changes in the coordination of motor function when someone is affected by fatigue. The study establishes that synergies remain fairly stable with the onset of fatigue, but the fatigue affects the dynamical coordination understood as a cognitive process. These results have been validated with 9 healthy subjects for three representative exercises for upper limb: biceps, triceps and deltoid.