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

Modeling and experimental validation of the influence of robot temperature on its energy consumption

This paper presents an approach to significantly improve modeling accuracy for the power and energy demands of industrial robots. This is achieved by taking the temperature dependency of the joint's viscuous friction parameters into account. While the connection is commonly known, it is usually neglected in state-of-the-art energy consumption models for industrial robots. This paper shows that a consideration of temperature-dependent friction provides significant improvement of energy modeling accuracy. The approach is validated on a test rig with a KUKA KR 16 robotic manipulator. Measurements show that the grid energy consumption modeling error can be reduced from up to 45% to approx. 5% over the whole spectrum of operating temperatures

Specifying and Synthesizing Energy-Efficient Production System Controllers that Exploit Braking Energy Recuperation

Reducing the energy consumption is a major concern in industrial production systems. One approach is recuperating the braking energy of robot axes. Ideally, their acceleration and deceleration phases should be synchronized so that the braking energy of one axis can be reused directly to accelerate another. This requires a detailed alignment of the axes' trajectories, but also a careful design of the overall discrete control. Finding an optimal control strategy manually, however, is difficult, as also many functional and safety requirements must be considered. We therefore propose an automated methodology that consists of three parts: (1) A scenario-based language to flexibly specify the discrete production system behavior, (2) an automated procedure to synthesize optimal control strategies from such specifications, including PLC code generation, and (3) a procedure for the detailed trajectory optimization. We describe the methodology, focusing on parts (1) and (2) in this paper, and present tool support and evaluation results

Implications of Introducing High-Sensitivity Cardiac Troponin T Into Clinical Practice Data From the SWEDEHEART Registry

AbstractBackgroundCardiac troponin is the preferred biomarker for diagnosing myocardial infarction (MI).ObjectivesThe aim of this study was to examine the implications of introducing high-sensitivity cardiac troponin T (hs-cTnT) into clinical practice and to define at what hs-cTnT level risk starts to increase.MethodsWe analyzed data from 48,594 patients admitted because of symptoms suggesting an acute coronary syndrome and who were entered into a large national registry. Patients were divided into Group 1, those with hs-cTnT <6 ng/l; Group 2, those with hs-cTnT 6 to 13 ng/l; Group 3, those with hs-cTnT 14 to 49 ng/l (i.e., a group in which most patients would have had a negative cardiac troponin T with older assays); and Group 4, those with hs-cTnT ≥50 ng/l.ResultsThere were 5,790 (11.9%), 6,491 (13.4%), 10,476 (21.6%), and 25,837 (53.2%) patients in Groups 1, 2, 3, and 4, respectively. In Groups 1 to 4, the proportions with MI were 2.2%, 2.6%, 18.2%, and 81.2%. There was a stepwise increase in the proportion of patients with significant coronary stenoses, left ventricular systolic dysfunction, and death during follow-up. When dividing patients into 20 groups according to hs-cTnT level, the adjusted mortality started to increase at an hs-cTnT level of 14 ng/l.ConclusionsIntroducing hs-cTnT into clinical practice has led to the recognition of a large proportion of patients with minor cardiac troponin increases (14 to 49 ng/l), the majority of whom do not have MI. Although a heterogeneous group, these patients remain at high risk, and the adjusted mortality rate started to increase at the level of the 99th percentile in healthy controls

Increased proinflammatory endothelial response to S100A8/A9 after preactivation through advanced glycation end products

BACKGROUND: Atherosclerosis is an inflammatory disease in which a perpetuated activation of NFkappaB via the RAGE (receptor for advanced glycation end products)-MAPK signalling pathway may play an important pathogenetic role. As recently S100 proteins have been identified as ligands of RAGE, we sought to determine the effects of the proinflammatory heterodimer of S100A8/S100A9 on the RAGE-NFkappaB mediated induction of proinflammatory gene expression. METHODS: Human umbilical vein endothelial cells (HUVEC) were preincubated for 72 h with AGE-albumin or unmodified albumin for control, whereas AGE-albumin induction resulted in an upregulation of RAGE. Following this preactivation, cells were stimulated for 48 h with heterodimeric human recombinant S100A8/S100A9. RESULTS: Heterodimeric S100A8/S100A9 enhanced secretion of IL-6, ICAM-1, VCAM-1 and MCP1 in AGE-albumin pretreated HUVEC in a dose dependent manner. These effects could not be detected after stimulation with the homodimeric proteins S100A8, S100A9, S100A1 and S100B. The effects of heterodimeric S100A8/S100A9 were reduced by inhibition of the MAP-kinase pathways ERK1/2 and p38 by PD 98059 and SB 203580, respectively. CONCLUSION: The heterodimeric S100A8/S100A9 might therefore play a hitherto unknown role in triggering atherosclerosis in diabetes and renal failure, pathophysiological entities associated with a high AGE burden. Thus, blocking heterodimeric S100A8/S100A9 might represent a novel therapeutic modality in treating atherosclerosis

Sex differences in investigations and outcomes among patients with type 2 myocardial infarction

Objectives: Type 2 myocardial infarction (MI) is a heterogenous condition and whether there are differences between women and men is unknown. We evaluated sex differences in clinical characteristics, investigations and outcomes in patients with type 2 MI. Methods: In the Swedish Web based system for Enhancement and Development of Evidence based care in Heart disease Evaluated According to Recommended Therapies (SWEDEHEART) registry, we compared patients admitted to coronary care units with a diagnosis of type 1 or type 2 MI. Sex-stratified Cox regression models evaluated the association with all-cause death in men and women separately. Results: We included 57 264 (median age 73 years, 65% men) and 6485 (median age 78 years, 50% men) patients with type 1 and type 2 MI, respectively. No differences were observed in the proportion of men and women with type 2 MI who underwent echocardiography and coronary angiography, but women were less likely than men to have left ventricular (LV) impairment and obstructive coronary artery disease (CAD). Compared with type 1 MI, patients with type 2 MI had higher risk of death regardless of sex (men: adjusted HR 1.55 (95% CI 1.44 to 1.67); women: adjusted HR 1.34 (95% CI 1.24 to 1.45)). In those with type 2 MI, the risk of death was lower for women than men (adjusted HR 0.85 (95% CI 0.76 to 0.92) (men, reference)). Conclusions: Type 2 MI occurred in men and women equally and we found no evidence of sex bias in the selection of patients for cardiac investigations. Patients with type 2 MI had worse outcomes, but women were less likely to have obstructive CAD or severe LV impairment and were more likely to survive than men

Revisiting the obesity paradox in heart failure:Per cent body fat as predictor of biomarkers and outcome

Aims - Obesity defined by body mass index (BMI) is characterized by better prognosis and lower plasma N-terminal pro-B-type natriuretic peptide (NT-proBNP) in heart failure. We assessed whether another anthropometric measure, per cent body fat (PBF), reveals different associations with outcome and heart failure biomarkers (NT-proBNP, high-sensitivity troponin T (hs-TnT), soluble suppression of tumorigenesis-2 (sST2)). Methods - In an individual patient dataset, BMI was calculated as weight (kg)/height (m)2, and PBF through the Jackson–Pollock and Gallagher equations. Results - Out of 6468 patients (median 68 years, 78% men, 76% ischaemic heart failure, 90% reduced ejection fraction), 24% died over 2.2 years (1.5–2.9), 17% from cardiovascular death. Median PBF was 26.9% (22.4–33.0%) with the Jackson–Pollock equation, and 28.0% (23.8–33.5%) with the Gallagher equation, with an extremely strong correlation (r = 0.996, p 2, third PBF tertile), hs-TnT and sST2, but not NT-proBNP, independently predicted outcome. Conclusion - In parallel with increasing BMI or PBF there is an improvement in patient prognosis and a decrease in NT-proBNP, but not hs-TnT or sST2. hs-TnT or sST2 are stronger predictors of outcome than NT-proBNP among obese patients

NT-proBNP for Risk Prediction in Heart Failure:Identification of Optimal Cutoffs Across Body Mass Index Categories

OBJECTIVES The goal of this study was to assess the predictive power of N-terminal pro–B-type natriuretic peptide (NT-proBNP) and the decision cutoffs in heart failure (HF) across body mass index (BMI) categories. BACKGROUND  Concentrations of NT-proBNP predict outcome in HF. Although the influence of BMI to reduce levels of NT-proBNP is known, the impact of obesity on prognostic value remains uncertain. METHODS Individual data from the BIOS (Biomarkers In Heart Failure Outpatient Study) consortium were analyzed. Patients with stable HF were classified as underweight (BMI = 40 kg/m(2)) obese. The prognostic rote of NT-proBNP was tested for the endpoints of all-cause and cardiac death. RESULTS The study population included 12,763 patients (mean age 66 +/- 12 years; 25% women; mean left ventricular ejection fraction 33% 113%). Most patients were overweight (n = 5,176), followed by normal weight (n = 4,299), mildly obese (n = 2,157), moderately obese (n = 612), severely obese (n = 314), and underweight (n = 205). NT-proBNP inversely correlated with BMI (beta = -0.174 for 1 kg/m(2); P < 0.001). Adding NT-proBNP to clinical models improved risk prediction across BMI categories, with the exception of severely obese patients. The best cutoffs of NT-proBNP for 5-year all-cause death prediction were lower as BMI increased (3,785 ng/L, 2,193 ng/L, 1,554 ng/L, 1,045 ng/L, 755 ng/L, and 879 ng/L, for underweight, normal weight, overweight, and mildly, moderately, and severely obese patients, respectively) and were higher in women than in men. CONCLUSIONS NT-proBNP maintains its independent prognostic value up to 40 kg/m(2) BMI, and tower optimal risk-prediction cutoffs are observed in overweight and obese patients