Episodic Learning with Control Lyapunov Functions for Uncertain Robotic Systems

Many modern nonlinear control methods aim to endow systems with guaranteed properties, such as stability or safety, and have been successfully applied to the domain of robotics. However, model uncertainty remains a persistent challenge, weakening theoretical guarantees and causing implementation failures on physical systems. This paper develops a machine learning framework centered around Control Lyapunov Functions (CLFs) to adapt to parametric uncertainty and unmodeled dynamics in general robotic systems. Our proposed method proceeds by iteratively updating estimates of Lyapunov function derivatives and improving controllers, ultimately yielding a stabilizing quadratic program model-based controller. We validate our approach on a planar Segway simulation, demonstrating substantial performance improvements by iteratively refining on a base model-free controller

Outcomes following repair of anomalous coronary artery from the pulmonary artery in infants: results from a procedure-based national database

BACKGROUND: Anomalous coronary artery from the pulmonary artery (ACAPA) is a very rare congenital anomaly that often occurs during infancy. Patients can present in a critical condition. METHODS: We analysed procedure-related data from a national audit database for the period 2000-2013. RESULTS: A total of 120 patients 30 days) were available in 102 patients and the mean follow-up time was 4.7 years. The 30-day overall mortality was 1.9%, higher for neonates (16.7% vs 1%, p=0.1) and after postoperative extracorporeal membrane oxygenation (ECMO) (20% vs 1%, p=0.09). At 10 years the survival estimate is 95.1%, freedom from coronary and mitral reintervention being 95.9% and 91.2%, respectively. Use of postoperative ECMO was a risk factor for long-term mortality (p<0.001). Risk factors for coronary reintervention were age under 30 days (p=0.06) and the need for postoperative ECMO (p=0.02). Age under 30 days (p=0.002) was a risk factor for mitral reintervention. CONCLUSIONS: To our knowledge this is the largest series to date. These preliminary national results show that early outcomes are good and medium-term attrition acceptable. Poor outcomes are correlated with early presentation, also with the need for postoperative circulatory support

Outcomes following aortic valve procedures in 201 complex congenital heart disease cases:results from the UK National Audit

OBJECTIVES: Some patients with complex congenital heart disease (cCHD) also require aortic valve (AoV) procedures. These cases are considered high risk but their outcome has not been well characterized. We aim to describe these scenarios in the current practice, and provide outcome data for counselling and decision-making. METHODS: This was a retrospective study using the UK National Congenital Heart Disease Audit data on cCHD patients undergoing aortic valve replacement, balloon dilation (balloon aortic valvuloplasty) or surgical repair (surgical aortic valve repair) between 2000 and 2012. Coarsened exact matching was used to pair cCHD with patients undergoing AoV procedures for isolated valve disease. RESULTS: A total of 201 patients with a varied spectrum of cCHD undergoing 242 procedures were included, median age 9.4 years (1 day–65 years). Procedure types were: balloon aortic valvuloplasty (n = 31, 13%), surgical aortic valve repair (n = 57, 24%) and aortic valve replacement (n = 154, 63%). Mortality at 30 days was higher in neonates (21.8% vs 5.3%, P = 0.02). Survival at 10 years was 83.1%, freedom from aortic valve replacement 83.8% and freedom from balloon aortic valvuloplasty/surgical aortic valve repair 86.3%. Neonatal age (P < 0.001), single ventricle (P = 0.08), concomitant Fontan/Glenn (P = 0.002) or aortic arch procedures (0.02) were associated with higher mortality. cCHD patients had lower survival at 30 days (93% vs 100%, P = 0.003) and at 10 years (86.4% vs 96.1%, P = 0.005) compared to matched isolated AoV disease patients. CONCLUSIONS: AoV procedures in cCHD can be performed with good results outside infancy, but with higher mortality than in isolated AoV disease. Neonates and patients with single ventricle defects, especially those undergoing concomitant Fontan/Glenn, have worse outcomes

A Control Lyapunov Perspective on Episodic Learning via Projection to State Stability

The goal of this paper is to understand the impact of learning on control synthesis from a Lyapunov function perspective. In particular, rather than consider uncertainties in the full system dynamics, we employ Control Lyapunov Functions (CLFs) as low-dimensional projections. To understand and characterize the uncertainty that these projected dynamics introduce in the system, we introduce a new notion: Projection to State Stability (PSS). PSS can be viewed as a variant of Input to State Stability defined on projected dynamics, and enables characterizing robustness of a CLF with respect to the data used to learn system uncertainties. We use PSS to bound uncertainty in affine control, and demonstrate that a practical episodic learning approach can use PSS to characterize uncertainty in the CLF for robust control synthesis

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East European countries have reported high prevalence of Arterial Hypertension (AHT). In order to investigate the data for Romania, we firstly performed a national survey-the Study for the Evaluation of Prevalence of Hypertension and Cardiovascular Risk in Adult Population in Romania (SEPHAR). A representative population was selected using stratified proportional sampling, including 2017 adult subjects, ≥18 years old. The general prevalence of AHT was 44,92%, higher in men (50,17%) than in women (41,11%) (P &lt; .0001) and predominant in rural areas (49,47%) in comparison to the urban ones (41,58%) (P &lt; .02). AHT awareness attended 44,26%, rising with age, significantly lower in men (34,58%) than in women (52,8%) (P &lt; .0006). We have found a 38,85% proportion of treated hypertensive persons, worse for men (30,11%) then for women (46,56%) (P &lt; .003). The rate of AHT control was 19,88%, with no significant differences between gender. In conclusion, we estimated for Romania a high prevalence of AHT, a level of awareness and treatment lower than in many European countries and a rate of treatment control at the inferior limit of the European average. Males, characterized by a higher prevalence of AHT, were also less aware and less treated than women

Living donor liver transplant in Romania – 116 cases experience

Centrul de Chirurgie Generală și Transplant Hepatic “Dan Setlacec”, Institutul Clinic Fundeni, Bucureşti, România, Al XII-lea Congres al Asociației Chirurgilor „Nicolae Anestiadi” din Republica Moldova cu participare internațională 23-25 septembrie 2015Introducere: Cererea pentru transplantul hepatic în Romania este în continuă creștere în timp ce penuria de donatori de organe persistă. Timpul lung de așteptare pentru un transplant de ficat şi disfuncţia hepatică progresivă aferentă așteptării a motivat multe familii să ia în considerare donarea de organe. Material și metode: În anul 2000 a fost realizat primul transplant hepatic ortotopic cu ficat întreg de către echipa I.Popescu et al. la Institutul Clinic Fundeni din Bucureşti, urmat de transplantul de ficat de la donator viu (LDLT) mai târziu în acelaşi an, ajungând în aprilie 2015 la un total de 116 de transplanturi cu ficat de la donator viu. LDLT a fost realizată cu hemificat drept la 78 pacienți, secțiune laterală stânga – la 26 pacienți, hemificat stâng – la 7 pacienți, hemificat stâng în bloc cu segmentul 1 – la 3 pacienți, şi dual graft – la 2 pacienți. Rezultate: Rata de morbidități majore a fost de 53,4% (62 pacienți), rata generală de retransplant a fost de 11,3% (13 pacienți). Rata de supraviețuire generală la 1-, 3-, şi 5 ani a fost de 88,8%, 82,5%, respectiv, 79,2%. Concluzii: Scopul nostru a fost de a reduce rata mortalității pe lista de așteptare prin scurtarea timpului de aşteptare pentru TH prin asigurarea grefelor necesare. Avantajele LDLT includ posibilitatea de a fi efectuate în regim programat şi cu un timp de aşteptare scurt pentru primitor, în timp ce indicaţiile de transplant pot fi extinse (ex: HCC în afara criteriilor Milano).Introduction: The request for Liver Transplant (LT) in Romania continues to increase while the donor pool size remains inadequate. The long waiting time for a liver transplant and the progressive liver dysfunction that occurs in this time has motivated many families to consider living donation. Material and methods: In 2000, the first successful LT (with whole graft) was carried out by I.Popescu et al. at Fundeni Clinical Institute in Bucharest, followed by the first living donor liver transplantation (LDLT) (successful) later the same year, reaching 116 living donors liver transplants by April 2015. LDLT was performed with right hemiliver in 78 pts, left lateral section in 26 pts, left hemiliver in 7 pts, left hemiliver with segment 1 in 3 pts, and dual graft LDLT in 2 pts: one received a right hemiliver and a left lateral section (17), and one received a left hemiliver and a left lateral section. Results: Major morbidity rates were 53.4% (62 pts) Overall retransplantation rate was 11.3% (13 pts). Long-term overall 1-, 3-, and 5- year estimated survival rates were 88.8%, 82.5%, and 79.2%, respective. Conclusions: Our main goal was to continuously reduce the drop-out rate on waiting list (due to mortality and morbidity) by shortening the waiting time for LT insured by providing the necessary grafts. Advantages of LDLT include the ability to be performed on an elective basis, with optimal timing and no waiting time for the recipient, while the indications for transplantation may be extended (i.e. HCC beyond Milan criteria)