Calculation of achievable robot joint accelerations based on a new robot forward dynamics algorithm

Abstract An algorithm that calculates the feasible robot joints’ accelerations based on a new forward dynamics algorithm while considering the actuators’ force/torque saturations and achieves a realistic simulation of robot movements is given in this paper. While the most used forward dynamics algorithm in the literature, Walker and Orin’s Method 1, calculates robot forward dynamics by executing Recursive Newton-Euler Algorithm (RNEA) n + 1 times, where n is the number of degrees-of-freedom (DoFs), algorithm used here solves forward dynamics using the modified RNEA (mRNEA) only once. Owing to that, this algorithm is very efficient. Furthermore, the computational complexity of the algorithm is even more significant when used for robot simulation as it does not require calculating joint torques as inputs for forward dynamics, unlike other methods. Another benefit of the proposed method is the ease of development and implementation for a specific robot. The proposed mRNEA and its application within the forward dynamics algorithm are demonstrated using a serial 4-DoF spatial disorientation trainer as an example

Modelovanje i upravljanje manipulatora u sistemima za trenažu pilota savremenih borbenih aviona

Vidaković, J., Lazarević, M., Kvrgic, V., Modelovanje i upravljanje manipulatora u sistemima za trenažu pilota savremenih borbenih aviona, Monografija, LOLA INSTUTU

Practical Approaches for Robot Dynamic Model Implementation for Control and Simulation Purposes

A robot dynamic model is time variable, highly non-linear and characterized by coupling effects among the robot joints. Consequently, a derivation and implementation of a robot dynamic model, which is used for purposes of control, simulation, and mechanical design, often represents a challenging task. The last couple of decades saw a great amount of research with the aim to achieve better ease of use (development) and computational efficiency of robot dynamic algorithms. Recently, general-purpose robot modeler/simulator software that enables numerical calculation of robot inverse dynamics problem for user-developed robot model and input joint trajectories are being increasingly used by a wider range of robot developers for robot control purposes. In this study, two different practical approaches to account for robot dynamics for purposes of robot control, trajectory generation, mechanical design and simulation, are discussed. The first approach includes an efficient solution for forward dynamics using a novel modified recursive Newton–Euler algorithm, which is used for simulation, mechanical design, and trajectory generation. The second approach is based on modern software tools usage, for the purposes of simulation and control. Both strategies for implementation of robot dynamic model are based on developed 3D models of robots in CAD software and 3D modelers. Applied approaches are demonstrated in three different case studies. Discussion on the benefits of the presented approaches is given

Intraoperative transfusion practices in Europe

BACKGROUND: Transfusion of allogeneic blood influences outcome after surgery. Despite widespread availability of transfusion guidelines, transfusion practices might vary among physicians, departments, hospitals and countries. Our aim was to determine the amount of packed red blood cells (pRBC) and blood products transfused intraoperatively, and to describe factors determining transfusion throughout Europe. METHODS: We did a prospective observational cohort study enrolling 5803 patients in 126 European centres that received at least one pRBC unit intraoperatively, during a continuous three month period in 2013. RESULTS: The overall intraoperative transfusion rate was 1.8%; 59% of transfusions were at least partially initiated as a result of a physiological transfusion trigger- mostly because of hypotension (55.4%) and/or tachycardia (30.7%). Haemoglobin (Hb)- based transfusion trigger alone initiated only 8.5% of transfusions. The Hb concentration [mean (sd)] just before transfusion was 8.1 (1.7) g dl(-1) and increased to 9.8 (1.8) g dl(-1) after transfusion. The mean number of intraoperatively transfused pRBC units was 2.5 (2.7) units (median 2). CONCLUSION: Although European Society of Anaesthesiology transfusion guidelines are moderately implemented in Europe with respect to Hb threshold for transfusion (7-9 g dl(-1)), there is still an urgent need for further educational efforts that focus on the number of pRBC units to be transfused at this threshold. CLINICAL TRIAL REGISTRATION: NCT 01604083

Intraoperative transfusion practices and perioperative outcome in the European elderly: A secondary analysis of the observational ETPOS study

The demographic development suggests a dramatic growth in the number of elderly patients undergoing surgery in Europe. Most red blood cell transfusions (RBCT) are administered to older people, but little is known about perioperative transfusion practices in this population. In this secondary analysis of the prospective observational multicentre European Transfusion Practice and Outcome Study (ETPOS), we specifically evaluated intraoperative transfusion practices and the related outcomes of 3149 patients aged 65 years and older. Enrolled patients underwent elective surgery in 123 European hospitals, received at least one RBCT intraoperatively and were followed up for 30 days maximum. The mean haemoglobin value at the beginning of surgery was 108 (21) g/l, 84 (15) g/l before transfusion and 101 (16) g/l at the end of surgery. A median of 2 [1–2] units of RBCT were administered. Mostly, more than one transfusion trigger was present, with physiological triggers being preeminent. We revealed a descriptive association between each intraoperatively administered RBCT and mortality and discharge respectively, within the first 10 postoperative days but not thereafter. In our unadjusted model the hazard ratio (HR) for mortality was 1.11 (95% CI: 1.08–1.15) and the HR for discharge was 0.78 (95% CI: 0.74–0.83). After adjustment for several variables, such as age, preoperative haemoglobin and blood loss, the HR for mortality was 1.10 (95% CI: 1.05–1.15) and HR for discharge was 0.82 (95% CI: 0.78–0.87). Preoperative anaemia in European elderly surgical patients is undertreated. Various triggers seem to support the decision for RBCT. A closer monitoring of elderly patients receiving intraoperative RBCT for the first 10 postoperative days might be justifiable. Further research on the causal relationship between RBCT and outcomes and on optimal transfusion strategies in the elderly population is warranted. A thorough analysis of different time periods within the first 30 postoperative days is recommended