Bond graph simulation of error propagation in position estimation of a hydraulic cylinder using low cost accelerometers

The indirect calculation from acceleration of transversal displacement of the piston inside the body of a double effect linear hydraulic cylinder during its operating cycle is assessed. Currently an extensive effort exists in the improvement of the mechanical and electronic design of the highly sophisticated MEMS accelerometers. Nevertheless, the predictable presence of measurement errors in the current commercial accelerometers is the main origin of velocity and displacement measurement deviations during integration of the acceleration. A bond graph numerical simulation model of the electromechanical system has been developed in order to forecast the effect of several measurement errors in the use of low cost two axes accelerometers. The level of influence is assessed using quality indicators and visual signal evaluation, for both simulations and experimental results. The obtained displacements results are highly influenced by the diverse dynamic characteristics of each measuring axis. The small measuring errors of a simulated extremely high performance sensor generate only moderate effects in longitudinal displacement but deep deviations in the reconstruction of piston transversal movements. The bias error has been identified as the source of the higher deviations of displacement results; although, its consequences can be easily corrected.Peer ReviewedPostprint (published version

Experimental study of 3D movement in cushioning of hydraulic cylinder

A double acting cylinder operation has been fully monitored in its key functional parameters, focused on characterization of end-of-stroke cushioning and starting phases. Being the cylinder performance reliant in the piston constructive geometry, the number and location of piston circumferential grooves is a significant parameter affecting the internal cushioning system performance. An eddy current displacement sensor assembled in the piston allows assessment of piston radial displacement inside the cylinder tube, which is directly related with the studied operating phases. Due to such 3D displacements, the piston becomes as an active and self-adjusting element along the functional cycle of the cylinder. Mechanical joints orientation and operating pressure are also relevant parameters affecting piston radial displacement and, thus, the cushioning and starting performance. Computational Fluid Dynamics (CFD) results confirm the observed functional role of the perimeter grooves; the flow and pressure distributions, where develops a significant radial force, are also in accordance with the registered radial displacement.Peer ReviewedPostprint (published version

GeroMAG: in-house prototype of an innovative sealed, compact and non-shaft-driven gerotor pump with magnetically-driving outer rotor

The technology of gerotor pumps is progressing towards cutting-edge applications in emerging sectors, which are more demanding for pump performance. Moreover, recent environmental standards are heading towards leakage-free and noiseless hydraulic systems. Hence, in order to respond to these demands, this study, which will be referred to as the GeroMAG concept, aims to make a leap from the standard gerotor pump technology: a sealed, compact, non-shaft-driven gerotor pump with a magnetically-driving outer rotor. The GeroMAG pump is conceived as a variable-flow pump to accomplish a standard volumetric flow rate at low rotational speed with satisfactory volumetric efficiency. By following the authors’ methodology based on a catalogue of best-practice rules, a custom trochoidal gear set is designed. Then, two main technological challenges are encountered: how to generate the rotational movement of the driving outer rotor and how to produce the guide of rotation of the gear set once there is no drive shaft. To confront them, a quiet magnet brushless motor powers the driving outer rotor through pole pieces placed in its external sideway and the rotational movement is guided by the inner edgewise pads carved on it. Subsequently, GeroMAG pump architecture, prototype, housing, methodology, materials and manufacture will be presented. As a principal conclusion, the GeroMAG proof of concept and pump prototype are feasible, which is corroborated by experimental results and performance indexes.Peer ReviewedPostprint (published version

Magnet-sleeve-sealed mini trochoidal-gear pump prototype with polymer composite gear

The trochoidal-gear technology has been growing in groundbreaking fields. Forthcoming applications are demanding to this technology a step forward in the conceiving stage of positive displacement machines. The compendium of the qualities and the inherent characteristics of trochoidal-gear technology, especially towards the gerotor pump, together with scale/size factor and magnetic-driven transmission has led to the idea of a magnet-sleeve-sealed variable flow mini trochoidal-gear pump. From its original concept, to the last phase of the design development, the proof of concept, this new product will intend to overcome problems such as noise, vibration, maintenance, materials, and dimensions. The paper aims to show the technological path followed from the concept, design, and model, to the manufacture of the first prototype, where the theoretical and numerical approaches are not always directly reflected in the prototype performance results. Early in the design process, from a standard-commercial sintered metal mini trochoidal-gear unit, fundamental characteristics and dimensional limitations have been evaluated becoming the strategic parameters that led to its configuration. The main technical challenge to confront is being sealed with non-exterior driveshaft, ensuring that the whole interior is filled and wetted with working fluid and helping the hydrodynamic film formation, the pumping effect, and the heat dissipation. Subsequently, the mini pump architecture, embodiment, methodology, materials, and manufacture are presented. The trend of applications of polymer composite materials and their benefits wanted to be examined with this new mini pump prototype, and a pure polyoxymethylene mini trochoidal-gear set has been designed and manufactured. Finally, both the sintered and the polymer trochoidal-gear units have been experimentally tested in an in-house full-instrumented mini test bench. Although the main goal of the presented work is the development of a new mini trochoidal-gear pump prototype rather than a numerical study, the results have been compared with numerical simulation. Subsequently, the prototype of the mini trochoidal-gear pump is a feasible proof of concept supported by functional indexes and the experimental results.Peer ReviewedPostprint (published version

Computational fluid dynamics and particle image velocimetry assisted design tools for a new generation of trochoidal gear pumps

Trochoidal gear pumps produce significant flow pulsations that result in pressure pulsations, which interact with the system where they are connected, shortening the life of both the pump and circuit components. And this behaviour is not acceptable for the demands of its current applications. The complicated aspects of the operation of a gerotor pump make computational fluid dynamics the proper tool for modeling and simulating its flow characteristics. Regarding the numerical simulation, a three-dimensional with deforming mesh Computational Fluid Dynamics (CFD) model is presented. The model includes the effects of the manufacturing tolerance and the leakage inside the pump. A new boundary condition is created for the simulation of the solid contact in the interteeth radial clearance. The experimental study of the pump is carried out by means of Time-Resolved Particle Image Velocimetry (TRPIV), and results are qualitatively evaluated thanks to the numerical simulation results. TRPIV is proved to be a feasible alternative to obtain the instantaneous flow of the pump in a direct mode. Thus, a new methodology involving CFD and TRPIV is presented, which allows the obtaining of the instantaneous flow of the pump in a direct mode without altering its behaviour significantly.Peer ReviewedPostprint (published version

Comprehensive description of clinical characteristics of a large systemic Lupus Erythematosus Cohort from the Spanish Rheumatology Society Lupus Registry (RELESSER) with emphasis on complete versus incomplete lupus differences

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by multiple organ involvement and pronounced racial and ethnic heterogeneity. The aims of the present work were (1) to describe the cumulative clinical characteristics of those patients included in the Spanish Rheumatology Society SLE Registry (RELESSER), focusing on the differences between patients who fulfilled the 1997 ACR-SLE criteria versus those with less than 4 criteria (hereafter designated as incomplete SLE (iSLE)) and (2) to compare SLE patient characteristics with those documented in other multicentric SLE registries. RELESSER is a multicenter hospital-based registry, with a collection of data from a large, representative sample of adult patients with SLE (1997 ACR criteria) seen at Spanish rheumatology departments. The registry includes demographic data, comprehensive descriptions of clinical manifestations, as well as information about disease activity and severity, cumulative damage, comorbidities, treatments and mortality, using variables with highly standardized definitions. A total of 4.024 SLE patients (91% with ≥4 ACR criteria) were included. Ninety percent were women with a mean age at diagnosis of 35.4 years and a median duration of disease of 11.0 years. As expected, most SLE manifestations were more frequent in SLE patients than in iSLE ones and every one of the ACR criteria was also associated with SLE condition; this was particularly true of malar rash, oral ulcers and renal disorder. The analysis-adjusted by gender, age at diagnosis, and disease duration-revealed that higher disease activity, damage and SLE severity index are associated with SLE [OR: 1.14; 95% CI: 1.08-1.20 (P < 0.001); 1.29; 95% CI: 1.15-1.44 (P < 0.001); and 2.10; 95% CI: 1.83-2.42 (P < 0.001), respectively]. These results support the hypothesis that iSLE behaves as a relative stable and mild disease. SLE patients from the RELESSER register do not appear to differ substantially from other Caucasian populations and although activity [median SELENA-SLEDA: 2 (IQ: 0-4)], damage [median SLICC/ACR/DI: 1 (IQ: 0-2)], and severity [median KATZ index: 2 (IQ: 1-3)] scores were low, 1 of every 4 deaths was due to SLE activity. RELESSER represents the largest European SLE registry established to date, providing comprehensive, reliable and updated information on SLE in the southern European population

Omecamtiv mecarbil in chronic heart failure with reduced ejection fraction, GALACTIC‐HF: baseline characteristics and comparison with contemporary clinical trials

Aims: The safety and efficacy of the novel selective cardiac myosin activator, omecamtiv mecarbil, in patients with heart failure with reduced ejection fraction (HFrEF) is tested in the Global Approach to Lowering Adverse Cardiac outcomes Through Improving Contractility in Heart Failure (GALACTIC‐HF) trial. Here we describe the baseline characteristics of participants in GALACTIC‐HF and how these compare with other contemporary trials. Methods and Results: Adults with established HFrEF, New York Heart Association functional class (NYHA) ≥ II, EF ≤35%, elevated natriuretic peptides and either current hospitalization for HF or history of hospitalization/ emergency department visit for HF within a year were randomized to either placebo or omecamtiv mecarbil (pharmacokinetic‐guided dosing: 25, 37.5 or 50 mg bid). 8256 patients [male (79%), non‐white (22%), mean age 65 years] were enrolled with a mean EF 27%, ischemic etiology in 54%, NYHA II 53% and III/IV 47%, and median NT‐proBNP 1971 pg/mL. HF therapies at baseline were among the most effectively employed in contemporary HF trials. GALACTIC‐HF randomized patients representative of recent HF registries and trials with substantial numbers of patients also having characteristics understudied in previous trials including more from North America (n = 1386), enrolled as inpatients (n = 2084), systolic blood pressure &lt; 100 mmHg (n = 1127), estimated glomerular filtration rate &lt; 30 mL/min/1.73 m2 (n = 528), and treated with sacubitril‐valsartan at baseline (n = 1594). Conclusions: GALACTIC‐HF enrolled a well‐treated, high‐risk population from both inpatient and outpatient settings, which will provide a definitive evaluation of the efficacy and safety of this novel therapy, as well as informing its potential future implementation