Adaptive Control Of A Differential Drive Mobile Robot For Tracking External Geometrical Features Using Fuzzy Reasoning And Reinforcement Learning Techniques

103 σ.Η πλοήγηση αυτόνομων ρομπότ σε άγνωστο περιβάλλον, αποτελεί ένα πολυδιάστατο πρόβλημα, που κατατάσσεται στη μηχανική συστημάτων λόγω των διαφορετικών επιστημονικών πεδίων που απαιτεί. Έναν ιδιαίτερο τομέα έρευνας, αποτελεί η Μηχανική Μάθηση, μια και αποτελεί τo μέσο για τη διαχείριση δεδομένων και τη δημιουργία αυτόνομων συμπεριφορών. Στη διπλωματική αυτή εργασία, εξετάζεται, η κίνηση ρομπότ διαφορικής οδήγησης σε άγνωστο περιβάλλον, εφαρμόζοντας Ασαφή Ενισχυτική Μάθηση, για την περίπτωση ακολούθησης τοίχου. Γίνεται κινηματική ανάλυση για τα ρομπότ διαφορικής οδήγησης, παρουσιάζεται η μέθοδος της Γενικής Αντίληψης και το θεωρητικό υπόβαθρο για την Ασαφή Λογική, την Ενισχυτική Μάθηση και την Ασαφή Ενισχυτική Μάθηση. Στο κομμάτι υλοποίησης, παρουσιάζεται το ρομπότ Khepera 3, στο οποίο εφαρμόστηκε η Ασαφής Ενισχυτική Μάθηση και μελετάται η συμπεριφορά των αισθητήρων του. Μελετάται επίσης η συμπεριφορά των αισθητήρων ενός πραγματικού ρομπότ Khepera 2. Ακολουθεί υλοποίηση Ασαφούς Ελέγχου και αριθμητικά αποτελέσματα, τόσο για την περίπτωση πραγματικού ρομπότ Khepera 2 όσο και για το ρομπότ Khepera 3 σε περιβάλλον εξομοίωσης. Τέλος υλοποιείται Ασαφής Ενισχυτική Μάθηση και εφαρμόζεται στο ρομπότ Khepera 3, σε περιβάλλον εξομοίωσης, όπου και παρουσιάζονται τα αριθμητικά αποτελέσματα και τα τελικά συμπεράσματα.Navigation of autonomous robots in unknown environments is a multidimensional problem, that can be classified as a systems engineering problem, due to the different scientific fields it requires. A specific field of research is Machine Learning, it being the medium for data management and creation of autonomous behaviors. This Diploma Thesis examines the movement of differential drive robots, in unknown environments, by applying the Fuzzy Reinforcement Learning method, for the wall following case. After a kinematic analysis of differential drive robots, the General Perception concept is presented, followed by the theoretical background for Fuzzy Logic, Reinforcement Learning and Fuzzy Reinforcement Learning. In the implementation part, a brief presentation of the Khepera 3 differential drive robot, is made, since it was the platform on which Fuzzy Reinforcement Learning was applied. Sensor behavior is presented for both the Khepera 3 and a real Khepera 2. An implementation of Fuzzy Control is made for a real Khepera 2 robot as well as a simulated Khepera 3 robot and results are presented. An implementation of Fuzzy Reinfocement Learning for a simulated Khepera 3 robot is made, with results and conclusions.Κωνσταντίνος Ε. Δογέα

Model to predict major complications following liver resection for HCC in patients with metabolic syndrome

Background: Metabolic syndrome (MS) is rapidly growing as risk factor for HCC. Liver resection for HCC in patients with MS is associated with increased postoperative risks. There are no data on factors associated with postoperative complications. Aims: The aim was to identify risk factors and develop and validate a model for postoperative major morbidity after liver resection for HCC in patients with MS, using a large multicentric Western cohort. Materials and methods: The univariable logistic regression analysis was applied to select predictive factors for 90 days major morbidity. The model was built on the multivariable regression and presented as a nomogram. Performance was evaluated by internal validation through the bootstrap method. The predictive discrimination was assessed through the concordance index. Results: A total of 1087 patients were gathered from 24 centers between 2001 and 2021. Four hundred and eighty-four patients (45.2%) were obese. Most liver resections were performed using an open approach (59.1%), and 743 (68.3%) underwent minor hepatectomies. Three hundred and seventy-six patients (34.6%) developed postoperative complications, with 13.8% major morbidity and 2.9% mortality rates. Seven hundred and thirteen patients had complete data and were included in the prediction model. The model identified obesity, diabetes, ischemic heart disease, portal hypertension, open approach, major hepatectomy, and changes in the nontumoral parenchyma as risk factors for major morbidity. The model demonstrated an AUC of 72.8% (95% CI: 67.2%-78.2%) (https://childb.shinyapps.io/NomogramMajorMorbidity90days/). Conclusions: Patients undergoing liver resection for HCC and MS are at high risk of postoperative major complications and death. Careful patient selection, considering baseline characteristics, liver function, and type of surgery, is key to achieving optimal outcomes

Comparison between the difficulty of laparoscopic limited liver resections of tumors located in segment 7 versus segment 8: An international multicenter propensity-score matched study

Background: Presently, according to different difficulty scoring systems, there is no difference in complexity estimation of laparoscopic liver resection (LLR) of segments 7 and 8. However, there is no published data supporting this assumption. To date, no studies have compared the outcomes of laparoscopic parenchyma-sparing resection of the liver segments 7 and 8. Methods: A post hoc analysis of patients undergoing LLR of segments 7 and 8 in 46 centers between 2004 and 2020 was performed. 1:1 Propensity score matching (PSM) was used to compare isolated LLR of segments 7 and 8. Subset analyses were also performed to compare atypical resections and segmentectomies of 7 and 8. Results: A total of 2411 patients were identified, and 1691 patients met the inclusion criteria. Comparison after PSM between the entire cohort of segment 7 and segment 8 resections revealed inferior results for segment 7 resection in terms of increased blood loss, blood transfusions, and conversions to open surgery. Subset analyses of only atypical resections similarly demonstrated poorer outcomes for segment 7 in terms of increased blood loss, operation time, blood transfusions, and conversions to open surgery. Conversely, a subgroup analysis of segmentectomies after PSM found better outcomes for segment 7 in terms of a shorter operation time and hospital stay. Conclusion: Differences in the outcomes of segments 7 and 8 resections suggest a greater difficulty of laparoscopic atypical resection of segment 7 compared to segment 8, and greater difficulty of segmentectomy 8 compared to segmentectomy 7

Impact of body mass index on perioperative outcomes of laparoscopic major hepatectomies

Background: Data on the effect of body mass index on laparoscopic liver resections are conflicting. We performed this study to investigate the association between body mass index and postoperative outcomes after laparoscopic major hepatectomies. Methods: This is a retrospective review of 4,348 laparoscopic major hepatectomies at 58 centers between 2005 and 2021, of which 3,383 met the study inclusion criteria. Concomitant major operations, vascular resections, and previous liver resections were excluded. Associations between body mass index and perioperative outcomes were analyzed using restricted cubic splines. Modeled effect sizes were visually rendered and summarized. Results: A total of 1,810 patients (53.5%) had normal weight, whereas 1,057 (31.2%) were overweight and 392 (11.6%) were obese. One hundred and twenty-four patients (3.6%) were underweight. Most perioperative outcomes showed a linear worsening trend with increasing body mass index. There was a statistically significant increase in open conversion rate (16.3%, 10.8%, 9.2%, and 5.6%, P <.001), longer operation time (320 vs 305 vs 300 and 266 minutes, P <.001), increasing blood loss (300 vs 300 vs 295 vs 250 mL, P =.022), and higher postoperative morbidity (33.4% vs 26.3% vs 25.0% vs 25.0%, P =.009) in obese, overweight, normal weight, and underweight patients, respectively (P <.001). However, postoperative major morbidity demonstrated a “U”-shaped association with body mass index, whereby the highest major morbidity rates were observed in underweight and obese patients. Conclusion: Laparoscopic major hepatectomy was associated with poorer outcomes with increasing body mass index for most perioperative outcome measures

Impact of liver cirrhosis and portal hypertension on minimally invasive limited liver resection for primary liver malignancies in the posterosuperior segments: An international multicenter study

Introduction: To assess the impact of cirrhosis and portal hypertension (PHT) on technical difficulty and outcomes of minimally invasive liver resection (MILR) in the posterosuperior segments. Methods: This is a post-hoc analysis of patients with primary malignancy who underwent laparoscopic and robotic wedge resection and segmentectomy in the posterosuperior segments between 2004 and 2019 in 60 centers. Surrogates of difficulty (i.e, open conversion rate, operation time, blood loss, blood transfusion, and use of the Pringle maneuver) and outcomes were compared before and after propensity-score matching (PSM) and coarsened exact matching (CEM). Results: Of the 1954 patients studied, 1290 (66%) had cirrhosis. Among the cirrhotic patients, 310 (24%) had PHT. After PSM, patients with cirrhosis had higher intraoperative blood transfusion (14% vs. 9.3%; p = 0.027) and overall morbidity rates (20% vs. 14.5%; p = 0.023) than those without cirrhosis. After coarsened exact matching (CEM), patients with cirrhosis tended to have higher intraoperative blood transfusion rate (12.1% vs. 6.7%; p = 0.059) and have higher overall morbidity rate (22.8% vs. 12.5%; p = 0.007) than those without cirrhosis. After PSM, Pringle maneuver was more frequently applied in cirrhotic patients with PHT (62.2% vs. 52.4%; p = 0.045) than those without PHT. Conclusion: MILR in the posterosuperior segments in cirrhotic patients is associated with higher intraoperative blood transfusion and postoperative morbidity. This parameter should be utilized in the difficulty assessment of MILR

Impact of neoadjuvant chemotherapy on the difficulty and outcomes of laparoscopic and robotic major liver resections for colorectal liver metastases: A propensity-score and coarsened exact-matched controlled study

Background: Minimal invasive liver resections are a safe alternative to open surgery. Different scoring systems considering different risks factors have been developed to predict the risks associated with these procedures, especially challenging major liver resections (MLR). However, the impact of neoadjuvant chemotherapy (NAT) on the difficulty of minimally invasive MLRs remains poorly investigated. Methods: Patients who underwent laparoscopic and robotic MLRs for colorectal liver metastases (CRLM) performed across 57 centers between January 2005 to December 2021 were included in this analysis. Patients who did or did not receive NAT were matched based on 1:1 coarsened exact and 1:2 propensity-score matching. Pre- and post-matching comparisons were performed. Results: In total, the data of 5189 patients were reviewed. Of these, 1411 procedures were performed for CRLM, and 1061 cases met the inclusion criteria. After excluding 27 cases with missing data on NAT, 1034 patients (NAT: n = 641; non-NAT: n = 393) were included. Before matching, baseline characteristics were vastly different. Before matching, the morbidity rate was significantly higher in the NAT-group (33.2% vs. 27.2%, p-value = 0.043). No significant differences were seen in perioperative outcomes after the coarsened exact matching. After the propensity-score matching, statistically significant higher blood loss (mean, 300 (SD 128–596) vs. 250 (SD 100–400) ml, p-value = 0.047) but shorter hospital stay (mean, 6 [4-8] vs. 6 [5-9] days, p-value = 0.043) were found in the NAT-group. Conclusion: The current study demonstrated that NAT had minimal impact on the difficulty and outcomes of minimally-invasive MLR for CRLM