Proportional electro-hydraulic valves: from analogue to digital control

Proportional electro-hydraulic valves are ubiquitous as flow actuators in hydraulic systems. Flow regulation is the result of the accurate positioning of a spool driven by a solenoid and a position sensor, usually a Linear Variable Differential Transformer. The overall control consists of two hierarchical loops: the inner loop is the solenoid current regulator with a closed-loop bandwidth close to 1 kHz. A model-based digital regulator of this kind has been presented elsewhere: requirements and performance are here reminded. The outer loop is a position tracking control, in charge of an accurate positioning of the spool with respect to the valve openings. The paper addresses the outer loop and concentrates on the conversion of an existing industrial analogue controller into a digital one. The analogue controller is a nonlinear proportional, integrative and derivative controller including a second-order derivative, and is capable of recovering a dead-band hysteresis. The digital conversion provides the necessary position derivatives through a state predictor, in order to withstand the 5-kHz Nyquist limit of the power supplier. As such it departs from traditional conversions dating back to more than ten years ago. The digital control law is fed by the state predictions and repeats the analogue control law with some improvements. Preliminary experiments prove that the conversion repeats and improves analogue performance. Some flaws of the resulting digital controller are outlined and discussed in view of a model-based conversion.

Occurrence of multiple metal-resistance in bacterial isolates associated with transgenic white poplars ( Populus alba L.)

The occurrence of multiple metal-resistance was assessed in two bacterial collections, named Herbicide Resistant Bacteria (HRB) and Nuclease-Producing Bacteria (NPB) respectively, consisting of 15 and 11 isolates obtained from a loamy sand cultivated with transgenic white poplars (Populus alba L., cv 'Vilafranca') engineered for herbicide resistance. A third collection of 11 bacterial isolates, named Leaf-Associated Bacteria (LAB), obtained from the leaves of transgenic white poplars expressing theStSy gene for resveratrol production and from untransformed plants was evaluated. Resistance to Cd, Co, Cu, Pb and Zn was tested. As for the HRB collection, nine different phenotypes were monitored, which included tetra-, tri- and double-resistance. Tri- and double-metal resistance occurred also within the NPB and LAB collections. In both cases five different phenotypes were recovered. An additional investigation was carried out on the HRB-1c isolate, resistant to Cd, Co, Pb and Zn, which was previously demonstrated to produce indoleacetic acid, a plant-growth-promoting trait. Colorimetric assays, performed on the cell-depleted medium of HRB-1c liquid cultures grown in presence of heavy metals, confirmed that this trait was not affected. A 19-kb plasmid, possibly involved in the maintenance of the multiple metal-resistant phenotype, was detected in the HRB-1c cells

Digital current regulator for proportional electro-hydraulic valves featuring unknown disturbance rejection

Solenoid current regulation is well-known and standard in any proportional electro-hydraulic valve. The goal is to provide a wide-band transfer function from the reference to the measured current, thus making the solenoid a fast and ideal force actuator within the limits of the power supplier. The supplier is usually a Pulse Width Modulation (PWM) amplifier fixing the voltage bound and the Nyquist frequency of the regulator. Typical analogue regulators include three main terms: a feedforward channel, a proportional feedback channel and the electromotive force compensation. The latter compensation may be also accomplished by integrative feedback. Here the problem is faced through a model-based design (Embedded Model Control), on the basis of a wide-band embedded model of the solenoid which includes the effect of eddy currents. To this end model parameters must be identified. The embedded model includes a stochastic disturbance dynamics capable of estimating and correcting the electromotive contribution together with the model parametric uncertainty, variability and state dependence. The embedded model which is fed by the measured current and the supplied voltage becomes a state predictor of the controllable and disturbance dynamics. The control law combines a reference generator, state feedback and disturbance rejection to dispatch the PWM with the appropriate duty cycle. Modeling, identification and control design are outlined together with experimental result. Comparison with an existing analogue regulator is also provided

Proportional electro-hydraulic valves: from analogue to digital control

Proportional electro-hydraulic valves are ubiquitous as flow actuators in hydraulic systems. Flow regulation is the result of the accurate positioning of a spool driven by a solenoid and a position sensor, usually a Linear Variable Differential Transformer. The overall control consists of two hierarchical loops: the inner loop is the solenoid current regulator with a closed-loop bandwidth close to 1 kHz. A model-based digital regulator of this kind has been presented elsewhere: requirements and performance are here reminded. The outer loop is a position tracking control, in charge of an accurate positioning of the spool with respect to the valve openings. The paper addresses the outer loop and concentrates on the conversion of an existing industrial analogue controller into a digital one. The analogue controller is a nonlinear proportional, integrative and derivative controller including a second-order derivative, and is capable of recovering a dead-band hysteresis. The digital conversion provides the necessary position derivatives through a state predictor, in order to withstand the 5-kHz Nyquist limit of the power supplier. As such it departs from traditional conversions dating back to more than ten years ago. The digital control law is fed by the state predictions and repeats the analogue control law with some improvements. Preliminary experiments prove that the conversion repeats and improves analogue performance. Some flaws of the resulting digital controller are outlined and discussed in view of a model-based conversion.

Red cell distribution width and chronic heart failure: prognostic role beyond echocardiographic parameters.

Aim. Red cell distribution width (RDW) is a measure of anisocytosis. Higher values are robustly associated to adverse outcome in several conditions, including chronic heart failure (HF). The present study aimed to compared its prognostic role with that of echocardiographic parameters in this kind of patients. Methods. 232 stable and optimally treated chronic HF patients were enrolled. We excluded subjects suffering from valvular diseases or atrial fibrillation. They underwent blood sampling and echocardiographic examination. The primary endpoint of the study was cardiovascular death and/or HF hospitalization in the first year after enrolment. Results. 49 patients reached the primary endpoint. RDW best cut-off at ROC curve was 14.45%. Univariate analysis associated mitral regurgitation grade, left ventricular ejection fraction (LVEF), posterior wall thickness (PWT), LV mass index, and RDW&gt;14.45% to the primary endpoint. Multivariate regression analysis showed that LVEF, PWT, and RDW&gt;14.45% predict the primary endpoint. Area under ROC curve was 0.808 for LVEF, 0.762 for NYHA class, and 0.761 for RDW. Conclusion. In chronic HF patients RDW is a better predictor of adverse outcome than several echocardiographic parameters associated to outcome itself (LV mass index, mitral regurgitation grade), predicts prognosis even adjusting for those parameters, age and NYHA class, and is associated to several echocardiographic measurements. In conclusion, RDW can expand our tool bag in order to better follow-up these patients.</p

Left ventricular function in rheumatoid arthritis during anti-TNF-α treatment: a speckle tracking prospective echocardiographic study

Aim. Rheumatoid arthritis (RA) shows a high risk for cardiovascular disease, including heart failure. Although TNF-α has been implicated in the pathogenesis of myocardial remodelling, TNF-α inhibition did not show any efficacy in patients with advanced heart failure and should be contraindicated in RA with cardiac complications. We aimed to assess global left ventricular (LV) systolic function using global longitudinal strain (GLS) as a measure of myocardial deformation, in a group of RA patients before and during anti-TNF-α treatment. Methods. 13 patients (female:male 7:6) affected by RA were prospectively followed for one year during anti TNF-α treatment. Every subject underwent echocardiography before starting anti-TNF-α drugs and after one year of treatment, to evaluate LV ejection fraction (EF), telediastolic diameter, telediastolic volume and global longitudinal strain (GLS) that was calculated using 2D speckle tracking as the mean GLS from three standard apical views (2, 3 and 4 -chambers). The patients showed a mean age of 43 years at RA onset (SD: 13) and a mean follow-up of 7.3 years (SD: 4.8). Steroid and methotrexate were used in 84.6% and 100%, respectively, in association with etanercept (6 cases), adalimumab (4 cases) and infliximab (3 cases). Results. Patients globally showed a normal EF before and after one year of treatment (mean: 65% and 65.7%, respectively). GLS did not differ before or after anti-TNF-α treatment (mean: -15.8% and -16.7%, respectively). Conclusion. Anti-TNF-α treatment did not significantly modify myocardial contractility after 12 months. </p

A drastic complex atheromatous aorta. A case report

Aortic atherosclerosis is the most common disease of the aorta. More than 50% of the plaques thicker than 4 mm are located along the descending aorta. The complex morphology of the plaque, such as ulceration or the presence of thrombi, is associated with increased embolic risk. The increasing use of transesophageal echocardiogram has enhanced the recognition of aortic atheromas. We describe a case of a male patient with complex atherosclerotic disease involving the coronary vessels and descending aortic tract with some embolic complications

Cardiopoietic cell therapy for advanced ischemic heart failure: results at 39 weeks of the prospective, randomized, double blind, sham-controlled CHART-1 clinical trial

Cardiopoietic cells, produced through cardiogenic conditioning of patients' mesenchymal stem cells, have shown preliminary efficacy. The Congestive Heart Failure Cardiopoietic Regenerative Therapy (CHART-1) trial aimed to validate cardiopoiesis-based biotherapy in a larger heart failure cohort

Digital current regulator for proportional electro-hydraulic valves featuring unknown disturbance rejection

Solenoid current regulation is well-known and standard in any proportional electro-hydraulic valve. The goal is to provide a wide-band transfer function from the reference to the measured current, thus making the solenoid a fast and ideal force actuator within the limits of the power supplier. The supplier is usually a Pulse Width Modulation (PWM) amplifier fixing the voltage bound and the Nyquist frequency of the regulator. Typical analogue regulators include three main terms: a feedforward channel, a proportional feedback channel and the electromotive force compensation. The latter compensation may be also accomplished by integrative feedback. Here the problem is faced through a model-based design (Embedded Model Control), on the basis of a wide-band embedded model of the solenoid which includes the effect of eddy currents. To this end model parameters must be identified. The embedded model includes a stochastic disturbance dynamics capable of estimating and correcting the electromotive contribution together with the model parametric uncertainty, variability and state dependence. The embedded model which is fed by the measured current and the supplied voltage becomes a state predictor of the controllable and disturbance dynamics. The control law combines a reference generator, state feedback and disturbance rejection to dispatch the PWM with the appropriate duty cycle. Modeling, identification and control design are outlined together with experimental result. Comparison with an existing analogue regulator is also provide

Leaf-associated bacteria from transgenic white poplar producing resveratrol-like compounds: isolation, molecular characterization and evaluation of oxidative stress tolerance

The aim of this study was the isolation and characterization of the culturable bacteria inhabiting the leaves of transgenic white poplars (Populus alba L. ‘Villafranca’) engineered with the StSy gene for the production of resveratrollike compounds. Resveratrol glucosides are available in small amounts from natural sources or by expensive chemical synthesis procedures. An alternative approach for the large-scale production of these relevant pharmaceuticals is the use of transgenic plants as bioreactors, although the occurrence of novel molecules in plants growing under field conditions might interfere, to some extent, with the associated microbial population. Both epiphytes and endophytes were isolated from the leaves of 2 StSy transgenic lines producing resveratrol glucosides and from an untransformed plant line grown in a greenhouse. Eleven isolates were recovered and classified as members of the genus Bacillus by 16S rDNA-based analysis. In addition, 2 isolates were classified as members of the Curtobacterium and Kocuria genera, respectively. Tolerance to hydrogen peroxide, UV-C, and paraquat was evaluated, as were the swimming and swarming motility of the leaf-associated bacteria. Interestingly, the isolates recovered from transgenic tissues showed the ability to withstand oxidative stress compared with isolates recovered from the untransformed poplar line. In vitro bioassays showed that trans-resveratrol inhibited both the swarming and swimming motilities in all the tested bacteria. The effects of trans-resveratrol on flagellin production, required for motility, were also investigated by immunoblot analysis