Uncalibrated eye-to-hand visual servoing using inverse fuzzy models

(c) 2007 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.A new uncalibrated eye-to-hand visual servoing based on inverse fuzzy modeling is proposed in this paper. In classical visual servoing, the Jacobian plays a decisive role in the convergence of the controller, as its analytical model depends on the selected image features. This Jacobian must also be inverted online. Fuzzy modeling is applied to obtain an inverse model of the mapping between image feature variations and joint velocities. This approach is independent from the robot's kinematic model or camera calibration and also avoids the necessity of inverting the Jacobian online. An inverse model is identified for the robot workspace, using measurement data of a robotic manipulator. This inverse model is directly used as a controller. The inverse fuzzy control scheme is applied to a robotic manipulator performing visual servoing for random positioning in the robot workspace. The obtained experimental results show the effectiveness of the proposed control scheme. The fuzzy controller can position the robotic manipulator at any point in the workspace with better accuracy than the classic visual servoing approach.info:eu-repo/semantics/publishedVersio

Alternating versus synchronous ventilation of left and right lungs in piglets

Objective: We tested whether alternating ventilation (AV) of each lung (i.e. with a phase difference of half a ventilatory cycle) would decrease central venous pressure and so increase cardiac output when compared with simultaneous ventilation (SV) of both lungs. Theory: If, during AV, the inflated lung expands partly via compression of the opposite lung, mean lung volume will be smaller during AV than SV. As a consequence, mean intrathoracic pressure (as cited in the literature), and therefore, central venous pressure will be smaller. Design: The experiments were performed in seven anaesthetized and paralyzed piglets using a double-piston ventilator. Minute ventilation was the same during AV and SV. Starting at SV, we alternated three times between AV and SV for periods of 10 min. Results: During AV, central venous pressure was decreased by 0.7 mmHg and cardiac output was increased by 10±4.4% (mean, ±SD) compared with SV. AV also resulted in increased arterial pressure. During one-sided inflation with closed outlet of the opposite lung, a pressure rise occurred in the opposite lung, indicating compression. Conclusion: The higher cardiac output during AV than SV can be explained by the fact that central venous pressure is lower during AV. This lower central venous pressure is very probably due to the lower mean intrathoracic pressure caused by compression of the opposite lung during unilateral inflation

Effects of endotoxin infusion on mean systemic filling pressure and flow resistance to venous return

Mean systemic filling pressure (Psf) is an indicator of the filling state of the systemic circulation. Cardiac output (Q′) is related linearly to the difference between Psf and central venous pressure (Pcv), according to:Q′ = (Psf -Pcv)/Rsf, where Rsf is the flow resistance downstream from the sites where blood pressure is equal to Psf In 16 anaesthetized pigs we evaluated Psf, Rsf and Q′ during baseline conditions, continuous endotoxin infusion and after subsequent fluid loading. Psf and Rsf were determined from simultaneous measurements of Q′ and Pcv at seven levels of lung inflation. The following results were obtained. Psf was 8.1 ±1.8 mm Hg (mean ± SD) during baseline conditions, increased after endotoxin infusion to 9.9 ± 3.2 mm Hg (P = 0.04) and remained the same after infusion of 18 ml · kg-1 of Ringer's lactate. Rsf increased from 0.34 ± 0.07 to 0.80 ± 0.34 mm Hg · ml-1 · s by endotoxin and decreased after fluid infusion to 0.58 ± 0.14. Q′ changed inversely proportional to Rsf (P = 0.001). Rsf changes were highly correlated with the changes in total systemic flow resistance (RS) (P < 0.001). Endotoxin caused haemoconcentration and a decrease in plasma volume. The stability of Psf during endotoxin infusion and after volume loading indicate that the stressed volume was well maintained and changes in blood volume are compensated by changes in nonstressed volume. The increase in Rsf can be attributed to arteriolar vasoconstriction, venous vasoconstriction and haemoconcentration

Tidal variation of pulmonary blood flow and blood volume in piglets during mechanical ventilation during hyper-, normo- and hypovolaemia

Effects of changes in blood volume on changes in pulmonary blood flow and pulmonary blood volume during the ventilatory cycle during mechanical ventilation with a positive end-expiratory pressure of 2 cm H2O were determined in six pentobarbital anaesthetized, curarized pigs weighing about 10 kg. Haemodynamic variables were analysed for each cardiac cycle in eight ventilatory cycles in four consecutive series under hyper-, normo- and hypovolaemic conditions. Cardiac output was highest in hypervolaemia. Compared with normo- and hypovolaemia, it decreased less during inflation, due to a smaller rise in central venous pressure and presumably a larger filling state of the venous system. The smaller decrease in right ventricular output in hypervolaemia coincided with a larger fall in transmural central venous pressure (right ventricular filling pressure), due to right ventricular action at a higher, less steep part of its function curve. The difference between right ventricular-output (electromagnetic flow measurement) and left ventricular-output (pulse contour) indicated changes in pulmonary blood volume. In hypervolaemia less blood shifted from the pulmonary circulation into the systemic system during inflation than in normo- and hypovolaemia. This difference can be explained by two mechanisms namely, the smaller fall in input into the pulmonary vascular beds and a smaller pulmonary vascular volume decrease as a result of transmural pressure fall at a steeper part of the pressure-volume curve

Psoas major cross-sectional area: A potential marker of cardiorespiratory fitness

Background and Aim: Cardiorespiratory fitness is an important marker for overall health that significantly correlates with obesity-associated morbidities and mortality. Maximal oxygen uptake (VO2max) recorded during an incremental exercise test is the gold standard assessment for aerobic fitness. However, its cost, chronic illness, and frailty often preclude its application. The cross-sectional area (CSA) of the abdominal psoas major muscle is a predictor of sarcopenia and surgery outcomes and represents a promising biomarker for cardiorespiratory health. Therefore, in the present study, we have planned to assess the relationship between psoas major CSA, anthropometry, and body composition in a UK-based cohort of 210 men and women. Methods: Body mass (kg), height (cm), waist circumference (cm), VO2max, and blood pressure were measured in each participant. The CSA of psoas major, rectus abdominus, and another abdominal muscle of the core muscle group were assessed. Results: Following adjustment for height, psoas major CSA was found to be a significant predictor of percentage body fat (P = 0.02) in men, and body mass index (BMI) in both men (P = 0.015) and women (P = 0.004). We found psoas major CSA correlated more strongly with VO2max (r = 0.74, P < 0.01) than any other study outcome, including age and BMI. Conclusion: Psoas major muscle CSA represents an accurate, reproducible, and time-efficient surrogate for cardiorespiratory fitness and body composition

Mitral valve contour extraction using active contour models

To perform mitral valve contour extraction a software application is presented to support the surgeon in the implant size decision. The system is based on the application, to mitral valve surgery images, of active contour models. First, current repair surgery to mitral valve disease is discussed. Active contour models are presented and using different implementation approaches a comparison was done. The algorithms proposed by Kass, Amini, Cohen, Eviatar and Shah (Greedy algorithm) were implemented in test environment. The implementation to be used in the software application, is the one due to Kass with a few modifications related to Cohen’s approach. During surgery, the system needs to be calibrated and the active contour initialised. These processes are supported by a colour segmentation technique, tested with real images, using fuzzy sets. Real open-heart surgery images have been used to test the system developed

Determination of the mean cross-sectional area of the thoracic aorta using a double indicator dilution technique

A double indicator dilution technique for determining the mean cross-sectional area (CSA) of a blood vessel in vivo is presented. Analogous to the thermodilution method, dilution of hypertonic saline was measured by an electrical conductance technique. Because the change in conductance rather than absolute conductance was used to calculate CSA, pulsatile changes in shear rate of blood and conductance of surrounding tissues had no effect on the data. To calculate CSA from an ion mass balance, cardiac output was needed and estimated from the thermodilution curve using the same 'cold' (hypertonic) saline injection. The mean CSA, obtained from this double indicator dilution method (CSA(GD)), was compared with the CSA obtained from the intravascular ultrasound method (IVUS) in 44 paired observations in six piglets. The regression line is close to the line of identity (CSA(GD) = -1.83 + 1.06 · CSA(IVUS), r = 0.96). The difference between both CSAs was independent of the diameter of the vessel, on average -0.99 mm2 ± 2.64 mm2 (mean CSA(GD) = 46.84 ± 8.21 mm2, mean CSA(IVUS) = 47.82 ± 9.08 mm2) and not significant. The results show that the double indicator dilution method is a reliable technique for estimating the CSA of blood vessels in vivo

Laparoscopic radical 'no-touch' left pancreatosplenectomy for pancreatic ductal adenocarcinoma: technique and results

Background Laparoscopic left pancreatectomy has been well described for benign pancreatic lesions, but its role in pancreatic adenocarcinoma remains open to debate. We report our results adopting a laparoscopic technique that obeys established oncologic principles of open distal pancreatosplenectomy. Methods This is a post hoc analysis of a prospectively kept database of 135 consecutive patients undergoing laparoscopic left pancreatectomy, performed across two sites in the UK and the Netherlands (07/2007–07/2015 Southampton and 10/2013–07/2015 Amsterdam). Primary outcomes were resection margin and lymph node retrieval. Secondary endpoints were other perioperative outcomes, including post-operative pancreatic fistula. Definition of radical resection was distance tumour to resection margin &gt;1 mm. All patients underwent ‘laparoscopic radical left pancreatosplenectomy’ (LRLP) which involves ‘hanging’ the pancreas including Gerota’s fascia, followed by clockwise dissection, including formal lymphadenectomy. Results LRLP for pancreatic adenocarcinoma was performed in 25 patients. Seven of the 25 patients (28 %) had extended resections, including the adrenal gland (n = 3), duodenojejunal flexure (n = 2) or transverse mesocolon (n = 3). Mean age was 68 years (54–81). Conversion rate was 0 %, mean operative time 240 min and mean blood loss 340 ml. Median intensive/high care and hospital stay were 1 and 5 days, respectively. Clavien–Dindo score 3+ complication rate was 12 % and ISGPF grade B/C pancreatic fistula rate 28 %; 90-day (or in-hospital) mortality was 0 %. The pancreatic resection margin was clear in all patients, and the posterior margin was involved (&lt;1 mm) in 6 patients, meaning an overall R0 resection rate of 76 %. No resection margin was microscopically involved. Median nodal sample was 15 nodes (3–26). With an average follow-up of 17.2 months, 1-year survival was 88 %. Conclusions A standardised laparoscopic approach to pancreatic adenocarcinoma in the left pancreas can be adopted safely. Our study shows that these results can be reproduced across multiple sites using the same technique

Correction for respiration artifact in pulmonary blood pressure signals of ventilated patients

Objective. To develop an algorithm that corrects pulmonary artery pressure signals of ventilated patients for the respiration artifact. The algorithm should test the validity of the pulmonary pressure signal and differentiate between the cyclic respiration artifact and true measurement artifacts. Methods. The shape of each pulmonary pressure beat is described by eight characteristic features, including mean pressure value and the systolic and diastolic timing and pressure values. The features are corrected for the respiration artifact by fitting them in a least-squares sense on the first and second harmonica of the ventilator frequency. The corrected features are used by a signal validation algorithm, which adds a validity flag to each pressure beat. The validation algorithm rejects pressure beats with sudden changes in their shape but adapts itself when the changes persist. Results. The performance of the correction and validation technique was evaluated using pulmonary artery pressure signals of 30 patients who were scheduled for open heart surgery. The algorithm correctly recognized as invalid data those pressure signals disturbed by coagulation, surgical manipulations, or flushes of the pressure line. The algorithm marked on average 77 ± 11 % of the pulmonary pressure beats as valid. Conclusions. The validation algorithm marked sufficient pressure beats as valid to update a trend display every 5 sec. The correction algorithm enabled the validation algorithm to differentiate between true measurement artifacts and the respiration artifact