Control and optimization of semi-passively actuated multibody systems

The controlled multibody systems are under the consideration. At the lecture special emphasis is put on the study of underactuated and overactuated systems having different type of actuators (external powered drives, unpowered spring-damper like drives, etc.). Several questions are addressed about the role of inherent dynamics, and how much multibody system should be governed by external powered drives and how much by the systems inherent dynamics. The lecture consists of the following parts: introduction to the subject in question; mathematical statement of the optimal control problems that are suitable for modelling of controlled motion and optimization of semi-passively controlled multibody systems with different degrees of actuation; description of the methodology and the numerical algorithms for solution of control and optimization problems for semi-passively actuated multibody systems. The solutions of several optimal control problems for different kind of semi-passively actuated multibody systems are presented. Namely, the energy-optimal control of planar semi-passively controlled three-link manipulator robot, the energy-optimal control of closed-loop chain semi-passively actuated SCARA-like robot; optimization of the hydraulic and pneumatic drives of the multibody system modelled the human locomotor apparatus with above-knee prostheses, and others. Future perspectives in area of control and optimization problems of the semi-passively actuated multibody systems are discussed

ROTEM and vitro reversal of warfarin with APCC

Background: Warfarin-treated patients with a prolonged Prothrombin Time (PT) can have a normal rotational thromboelastometry (ROTEM) clotting time (CT). A previous in vitro study found that activated prothrombin complex concentrates (APCC) could reverse an albumin-induced coagulopathy monitored with ROTEM, but that prothrombin complex concentrates (PCC) could not. The aim of this study was to investigate the ability of ROTEM to monitor the in vitro reversal of warfarin-induced coagulopathy using APCC and to define an APCC dose response.Method: During the routine control of PT in 27 patients treated with warfarin, one extra 4.5 ml test tube of citrated whole blood was retrieved. Two concentrations of tissue factor ROTEM tissue factor (TF) activating reagents were used: a standard ROTEM ExTEM and a diluted 1:19000 concentration. The effects of two separate doses of APCC added in vitro corresponding to in vivo doses of 50 IE or 100 IE/kg were then studied on the ROTEM.Results: The ROTEM EXTEM CT was prolonged beyond the upper normal range of 68 s in patients with PT &gt;3.0, with a correlation coefficient of 0.88 to PT. ROTEM with the ExTEM reagent alongside high and low doses of APCC resulted in a significant shortening of median CT, both compared to baseline (100 s) and after low (65 s) and high doses (57 s). This was most evident in patients with PT &gt;2.0. ROTEM signals of clot propagation to clot formation time (CFT) and α angle had the reverse pattern. There was no effect on maximal clot strength with APCC. With the diluted TF no CT shortening was found with APCC.Conclusion: A clear dose response of APCC added in vitro to correct the effects of warfarin on ROTEM EXTEM CT was verified. ROTEM CT should be tested with non-activated PCC for in vivo reversal of warfarin in patients along with verification of a normalised PT. Further studies are needed to verify if a ROTEM CT in the lower normal range of &lt;57-65 s, as found in our in vitro APCC-spiked warfarin blood, is safe for invasive procedures.</p