Energy-efficient operation of industrial robots

Beim Erwerb eines Industrieroboters werden heutzutage nicht mehr nur klassische Faktoren wie die minimal erreichbare Taktzeit und die Anschaffungskosten als Kaufkriterien betrachtet, sondern auch der Leistungs- und Energiebedarf des Roboters sowie die laufenden Kosten über dessen gesamte Lebensdauer (TCO: Total Cost of Ownership). Konzepte zur Steigerung der Energieeffizienz von Industrierobotern sind somit sowohl aus ökologischer als auch aus ökonomischer Sicht erstrebenswert. Die Verbesserungsansätze lassen sich in zwei Kategorien unterteilen: Bei den hardwareseitigen Ansätzen wird eine Effizienzsteigerung durch Anpassung der verwendeten mechanischen und elektrischen Komponenten und/oder durch hardwarebezogene Erweiterung des Systems, zum Beispiel in Form von Energiespeichern, angestrebt. Die zweite Kategorie bilden Ansätze zur Optimierung der Software, bei denen die Ersparnisse durch energieeffizientere Bahnplanungsalgorithmen und Ablaufsteuerungen erzielt werden sollen. Die folgenden Untersuchungen fokussieren sich dabei auf die zweite Kategorie. Im Rahmen der vorliegenden Arbeit werden softwarebasierte Ansätze zum energieeffizienten Betrieb von Industrierobotern unter möglichst praxisnahen Bedingungen vorgestellt und auf zwei Roboter verschiedener Traglastklassen angewendet. Als Szenarien werden unterschiedliche industrietypische Applikationen wie zum Beispiel Pick-and-Place- und Schweißaufgaben untersucht. Die Bahnen der Ausgangsszenarien, die als Referenz zur Bewertung des Einsparpotentials dienen, werden direkt auf einer modernen, kommerziellen Robotersteuerung geplant, sodass diese dem Stand der Technik entsprechen. Es wird ein Modell erstellt, das den Leistungs- und Energiebedarf des betrachteten Roboters in Abhängigkeit von der durchgeführten Bewegung wiedergibt. Das Modell wird für beide Roboter am Prüfstand validiert. Die vorgestellten Verfahren zum energieeffizienten Betrieb von Industrierobotern lassen sich im Wesentlichen anhand der Freiheitsgrade des Ausgangsszenarios klassifizieren: Im ersten Fall werden zeitlich veränderliche Bewegungen mit fest vorgegebener Geometrie untersucht. Anschließend werden für Aufgaben mit veränderlicher Bahngeometrie zwei Verfahren zur Bestimmung einer energieoptimalen Bahngeometrie unter Verwendung nichtlinearer Optimierungsverfahren präsentiert. Im dritten Fall wird das Einsparpotential durch Änderung der relativen Lage des Roboters zum Werkstück aufgezeigt. Für jedes Verfahren werden die Bedingungen zur Umsetzung in der Praxis sowie die Ursachen und Einflussfaktoren für die erreichbaren Ersparnisse diskutiert

Prognostic value of cardiovascular biomarkers in the population

Importance: Identification of individuals at high risk for atherosclerotic cardiovascular disease within the population is important to inform primary prevention strategies.ObjectiveTo evaluate the prognostic value of routinely available cardiovascular biomarkers when added to established risk factors.Design, Setting, and Participants: Individual-level analysis including data on cardiovascular biomarkers from 28 general population–based cohorts from 12 countries and 4 continents with assessments by participant age. The median follow-up was 11.8 years.ExposureMeasurement of high-sensitivity cardiac troponin I, high-sensitivity cardiac troponin T, N-terminal pro-B-type natriuretic peptide, B-type natriuretic peptide, or high-sensitivity C-reactive protein.Main Outcomes and Measures: The primary outcome was incident atherosclerotic cardiovascular disease, which included all fatal and nonfatal events. The secondary outcomes were all-cause mortality, heart failure, ischemic stroke, and myocardial infarction. Subdistribution hazard ratios (HRs) for the association of biomarkers and outcomes were calculated after adjustment for established risk factors. The additional predictive value of the biomarkers was assessed using the C statistic and reclassification analyses.ResultsThe analyses included 164 054 individuals (median age, 53.1 years [IQR, 42.7-62.9 years] and 52.4% were women). There were 17 211 incident atherosclerotic cardiovascular disease events. All biomarkers were significantly associated with incident atherosclerotic cardiovascular disease (subdistribution HR per 1-SD change, 1.13 [95% CI, 1.11-1.16] for high-sensitivity cardiac troponin I; 1.18 [95% CI, 1.12-1.23] for high-sensitivity cardiac troponin T; 1.21 [95% CI, 1.18-1.24] for N-terminal pro-B-type natriuretic peptide; 1.14 [95% CI, 1.08-1.22] for B-type natriuretic peptide; and 1.14 [95% CI, 1.12-1.16] for high-sensitivity C-reactive protein) and all secondary outcomes. The addition of each single biomarker to a model that included established risk factors improved the C statistic. For 10-year incident atherosclerotic cardiovascular disease in younger people (aged <65 years), the combination of high-sensitivity cardiac troponin I, N-terminal pro-B-type natriuretic peptide, and high-sensitivity C-reactive protein resulted in a C statistic improvement from 0.812 (95% CI, 0.8021-0.8208) to 0.8194 (95% CI, 0.8089-0.8277). The combination of these biomarkers also improved reclassification compared with the conventional model. Improvements in risk prediction were most pronounced for the secondary outcomes of heart failure and all-cause mortality. The incremental value of biomarkers was greater in people aged 65 years or older vs younger people.Conclusions and Relevance: Cardiovascular biomarkers were strongly associated with fatal and nonfatal cardiovascular events and mortality. The addition of biomarkers to established risk factors led to only a small improvement in risk prediction metrics for atherosclerotic cardiovascular disease, but was more favorable for heart failure and mortality

Micro/nano acoustofluidics: materials, phenomena, design, devices, and applications

Acoustic actuation of fluids at small scales may finally enable a comprehensive lab-on-a-chip revolution in microfluidics, overcoming long-standing difficulties in fluid and particle manipulation on-chip. In this comprehensive review, we examine the fundamentals of piezoelectricity, piezoelectric materials, and transducers; revisit the basics of acoustofluidics; and give the reader a detailed look at recent technological advances and current scientific discussions in the discipline. Recent achievements are placed in the context of classic reports for the actuation of fluid and particles via acoustic waves, both within sessile drops and closed channels. Other aspects of micro/nano acoustofluidics are examined: atomization, translation, mixing, jetting, and particle manipulation in the context of sessile drops and fluid mixing and pumping, particle manipulation, and formation of droplets in the context of closed channels, plus the most recent results at the nanoscale. These achievements will enable applications across the disciplines of chemistry, biology, medicine, energy, manufacturing, and we suspect a number of others yet unimagined. Basic design concepts and illustrative applications are highlighted in each section, with an emphasis on lab-on-a-chip applications

Health-status outcomes with invasive or conservative care in coronary disease

BACKGROUND In the ISCHEMIA trial, an invasive strategy with angiographic assessment and revascularization did not reduce clinical events among patients with stable ischemic heart disease and moderate or severe ischemia. A secondary objective of the trial was to assess angina-related health status among these patients. METHODS We assessed angina-related symptoms, function, and quality of life with the Seattle Angina Questionnaire (SAQ) at randomization, at months 1.5, 3, and 6, and every 6 months thereafter in participants who had been randomly assigned to an invasive treatment strategy (2295 participants) or a conservative strategy (2322). Mixed-effects cumulative probability models within a Bayesian framework were used to estimate differences between the treatment groups. The primary outcome of this health-status analysis was the SAQ summary score (scores range from 0 to 100, with higher scores indicating better health status). All analyses were performed in the overall population and according to baseline angina frequency. RESULTS At baseline, 35% of patients reported having no angina in the previous month. SAQ summary scores increased in both treatment groups, with increases at 3, 12, and 36 months that were 4.1 points (95% credible interval, 3.2 to 5.0), 4.2 points (95% credible interval, 3.3 to 5.1), and 2.9 points (95% credible interval, 2.2 to 3.7) higher with the invasive strategy than with the conservative strategy. Differences were larger among participants who had more frequent angina at baseline (8.5 vs. 0.1 points at 3 months and 5.3 vs. 1.2 points at 36 months among participants with daily or weekly angina as compared with no angina). CONCLUSIONS In the overall trial population with moderate or severe ischemia, which included 35% of participants without angina at baseline, patients randomly assigned to the invasive strategy had greater improvement in angina-related health status than those assigned to the conservative strategy. The modest mean differences favoring the invasive strategy in the overall group reflected minimal differences among asymptomatic patients and larger differences among patients who had had angina at baseline

Initial invasive or conservative strategy for stable coronary disease

BACKGROUND Among patients with stable coronary disease and moderate or severe ischemia, whether clinical outcomes are better in those who receive an invasive intervention plus medical therapy than in those who receive medical therapy alone is uncertain. METHODS We randomly assigned 5179 patients with moderate or severe ischemia to an initial invasive strategy (angiography and revascularization when feasible) and medical therapy or to an initial conservative strategy of medical therapy alone and angiography if medical therapy failed. The primary outcome was a composite of death from cardiovascular causes, myocardial infarction, or hospitalization for unstable angina, heart failure, or resuscitated cardiac arrest. A key secondary outcome was death from cardiovascular causes or myocardial infarction. RESULTS Over a median of 3.2 years, 318 primary outcome events occurred in the invasive-strategy group and 352 occurred in the conservative-strategy group. At 6 months, the cumulative event rate was 5.3% in the invasive-strategy group and 3.4% in the conservative-strategy group (difference, 1.9 percentage points; 95% confidence interval [CI], 0.8 to 3.0); at 5 years, the cumulative event rate was 16.4% and 18.2%, respectively (difference, 121.8 percentage points; 95% CI, 124.7 to 1.0). Results were similar with respect to the key secondary outcome. The incidence of the primary outcome was sensitive to the definition of myocardial infarction; a secondary analysis yielded more procedural myocardial infarctions of uncertain clinical importance. There were 145 deaths in the invasive-strategy group and 144 deaths in the conservative-strategy group (hazard ratio, 1.05; 95% CI, 0.83 to 1.32). CONCLUSIONS Among patients with stable coronary disease and moderate or severe ischemia, we did not find evidence that an initial invasive strategy, as compared with an initial conservative strategy, reduced the risk of ischemic cardiovascular events or death from any cause over a median of 3.2 years. The trial findings were sensitive to the definition of myocardial infarction that was used