Real Time Estimator to Perform Targeted Biopsies With a Free-Wrist Robot Despite Large Deformations of the Insertion Orifice

In the context of keyhole surgery, and more particularly of uterine biopsy, the fine automatic movements of a surgical instrument held by a robot with 3 active DOF’s require an exact knowledge of the point of rotation of the instrument. However, this center of rotation is not fixed and moves during an examination. This paper deals with a new method of detecting and updating the interaction matrix linking the movements of the robot with the surgical instrument. This is based on the method of updating the Jacobian matrix which is named the “Broyden method”. It is able to take into account body tissue deformations in real time in order to improve the pointing task for automatic movements of a surgical instrument in an unknown environment.

Intermittent Control as a Model of Mouse Movements

We present Intermittent Control (IC) models as a candidate framework for modelling human input movements in Human–Computer Interaction (HCI). IC differs from continuous control in that users are not assumed to use feedback to adjust their movements continuously, but only when the difference between the observed pointer position and predicted pointer positions becomes large. We use a parameter optimisation approach to identify the parameters of an intermittent controller from experimental data, where users performed one-dimensional mouse movements in a reciprocal pointing task. Compared to previous published work with continuous control models, based on the Kullback–Leibler divergence from the experimental observations, IC is better able to generatively reproduce the distinctive dynamical features and variability of the pointing task across participants and over repeated tasks. IC is compatible with current physiological and psychological theory and provides insight into the source of variability in HCI tasks.

Development of a Cost-effective Biomechanical System for the Assessment of Kinematic and Kinetic Parameters in Soccer Players During a Lower Limb Pointing Task

PurposeThe main aim of the present study was to describe the development of a non-commercial biomechanical system designed for the simultaneous measurement of kinematic and kinetic parameters during a lower limb pointing task. The task was performed by two groups of soccer players (10 novices and 10 experts, aged 16-19 years) and the differences between the two groups, in terms of these parameters, were also assessed. MethodsThe calibration procedure of the combined system is presented in this paper. The system measured the Centre of Pressure (CoP) and body Center of Mass (CoM) displacements, kicking duration and the acceleration of the kicking leg. ResultsThe margin of error found for kinematic and kinetic calibration was less than 1%. Furthermore, the expert players presented decreased CoP and CoM displacements and kicking duration and acceleration of the kicking leg compared to the novices. ConclusionThe combined system provides an effective method for the simultaneous measurement of kinematic and kinetic parameters associated with kicking and may contribute to the development of intervention studies for the improvement of balance and kicking performance in sports.

Sex-specific Effects of Localized Muscle Fatigue on Upper Body Kinematics During a Repetitive Pointing Task

BackgroundFemales are reported to have a higher risk of musculoskeletal disorders than males. Among risk factors for musculoskeletal disorders, the mechanism of muscle fatigue remains unclear. Especially how females and males adapt to localized fatigue is poorly understood. The purpose of the study was to examine the sex-specific effects of fatigue location on shoulder, elbow and spinal joint angles, and angular variabilities during a repetitive pointing task.MethodsSeven males and ten females performed a standing repetitive pointing task when they were non-fatigued (NF), elbow-fatigued (EF), shoulder-fatigued (SF) and trunk-fatigued (TF), while trunk and upper body tridimensional kinematic data was recorded. Joint angles and angular variabilities of shoulder, elbow, upper thorax, lower thorax, and lumbar were calculated. ResultsResults showed that shoulder angles changed the most after EF in males, but after SF in females. The similarities between sexes were that SF increased the variabilities at upper (lateral flexion: 0.15° greater than NF, rotation: 0.26° greater than all other conditions) and lower thorax (lateral flexion: 0.13° greater than NF, rotation: averagely 0.1° greater than all other condition) in both sexes. TF altered upper thorax variability (0.36° smaller than SF), lower thorax angle (lateral flexion: 3.00° greater than NF, rotation: 1.68° greater than SF), and lumbar angle (averagely 1.8° smaller than all other conditions) in both sexes. However, females had greater lower thorax angle (lateral flexion: 8.3° greater, p=0.005) as well as greater upper (rotation: 0.53° greater, p=0.006) and lower thorax (rotation: 0.5° greater, p=0.007; flexion: 0.6° greater, p=0.014) angular variabilities.ConclusionsThe overall greater lower and upper thorax angular variabilities suggested a more unstable spinal movement pattern in females. The kinematic differences between sexes highlighted a few sex differences in adapting the localized muscle fatigue.

A Kinematic Evaluation of Linear and Parabolic Pointing in Virtual Reality

We present the results of a study investigating the influence of task and effector constraints on the kinematics of pointing movements performed in immersive virtual environments. We compared the effect of target width, as a task constraint, to the effect of movement distance, as an effector constraint, in terms of overall effect on movement time in a pointing task. We also compared a linear ray-cast pointing technique to a parabolic pointing technique to understand how interaction style may be understood in the context of task and effector constraints. The effect of target width as an information constraint on pointing performance was amplified in VR. Pointing technique acted as an effector constraint, with linear ray-cast pointing resulting in faster performance than parabolic pointers.

Author Correction: TDCS effects on pointing task learning in young and old adults

An amendment to this paper has been published and can be accessed via a link at the top of the paper.