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Background Minimally invasive surgery procedures, including stereotactic catheter aspiration and clearance of intracerebral hemorrhage (ICH) with recombinant tissue plasminogen activator hold a promise to improve outcome of supratentorial brain hemorrhage, a morbid and disabling type of stroke. A recently completed Phase III randomized trial showed improved mortality but was neutral on the primary outcome (modified Rankin scale score 0 to 3 at 1 yr). Objective To assess surgical performance and its impact on the extent of ICH evacuation and functional outcomes. Methods Univariate and multivariate models were used to assess the extent of hematoma evacuation efficacy in relation to mRS 0 to 3 outcome and postulated factors related to patient, disease, and protocol adherence in the surgical arm (n = 242) of the MISTIE trial. Results Greater ICH reduction has a higher likelihood of achieving mRS of 0 to 3 with a minimum evacuation threshold of ≤15 mL end of treatment ICH volume or ≥70% volume reduction when controlling for disease severity factors. Mortality benefit was achieved at ≤30 mL end of treatment ICH volume, or >53% volume reduction. Initial hematoma volume, history of hypertension, irregular-shaped hematoma, number of alteplase doses given, surgical protocol deviations, and catheter manipulation problems were significant factors in failing to achieve ≤15 mL goal evacuation. Greater surgeon/site experiences were associated with avoiding poor hematoma evacuation. Conclusion This is the first surgical trial reporting thresholds for reduction of ICH volume correlating with improved mortality and functional outcomes. To realize the benefit of surgery, protocol objectives, surgeon education, technical enhancements, and case selection should be focused on this goal.

Acute stroke due to supratentorial intracerebral haemorrhage is associated with high morbidity and mortality. Open craniotomy haematoma evacuation has not been found to have any benefit in large randomised trials. We assessed whether minimally invasive catheter evacuation followed by thrombolysis (MISTIE), with the aim of decreasing clot size to 15 mL or less, would improve functional outcome in patients with intracerebral haemorrhage. MISTIE III was an open-label, blinded endpoint, phase 3 trial done at 78 hospitals in the USA, Canada, Europe, Australia, and Asia. We enrolled patients aged 18 years or older with spontaneous, non-traumatic, supratentorial intracerebral haemorrhage of 30 mL or more. We used a computer-generated number sequence with a block size of four or six to centrally randomise patients to image-guided MISTIE treatment (1·0 mg alteplase every 8 h for up to nine doses) or standard medical care. Primary outcome was good functional outcome, defined as the proportion of patients who achieved a modified Rankin Scale (mRS) score of 0-3 at 365 days, adjusted for group differences in prespecified baseline covariates (stability intracerebral haemorrhage size, age, Glasgow Coma Scale, stability intraventricular haemorrhage size, and clot location). Analysis of the primary efficacy outcome was done in the modified intention-to-treat (mITT) population, which included all eligible, randomly assigned patients who were exposed to treatment. All randomly assigned patients were included in the safety analysis. This study is registered with ClinicalTrials.gov, number NCT01827046. Between Dec 30, 2013, and Aug 15, 2017, 506 patients were randomly allocated: 255 (50%) to the MISTIE group and 251 (50%) to standard medical care. 499 patients (n=250 in the MISTIE group; n=249 in the standard medical care group) received treatment and were included in the mITT analysis set. The mITT primary adjusted efficacy analysis estimated that 45% of patients in the MISTIE group and 41% patients in the standard medical care group had achieved an mRS score of 0-3 at 365 days (adjusted risk difference 4% [95% CI -4 to 12]; p=0·33). Sensitivity analyses of 365-day mRS using generalised ordered logistic regression models adjusted for baseline variables showed that the estimated odds ratios comparing MISTIE with standard medical care for mRS scores higher than 5 versus 5 or less, higher than 4 versus 4 or less, higher than 3 versus 3 or less, and higher than 2 versus 2 or less were 0·60 (p=0·03), 0·84 (p=0·42), 0·87 (p=0·49), and 0·82 (p=0·44), respectively. At 7 days, two (1%) of 255 patients in the MISTIE group and ten (4%) of 251 patients in the standard medical care group had died (p=0·02) and at 30 days, 24 (9%) patients in the MISTIE group and 37 (15%) patients in the standard medical care group had died (p=0·07). The number of patients with symptomatic bleeding and brain bacterial infections was similar between the MISTIE and standard medical care groups (six [2%] of 255 patients vs three [1%] of 251 patients; p=0·33 for symptomatic bleeding; two [1%] of 255 patients vs 0 [0%] of 251 patients; p=0·16 for brain bacterial infections). At 30 days, 76 (30%) of 255 patients in the MISTIE group and 84 (33%) of 251 patients in the standard medical care group had one or more serious adverse event, and the difference in number of serious adverse events between the groups was statistically significant (p=0·012). For moderate to large intracerebral haemorrhage, MISTIE did not improve the proportion of patients who achieved a good response 365 days after intracerebral haemorrhage. The procedure was safely adopted by our sample of surgeons. National Institute of Neurological Disorders and Stroke and Genentech. [Abstract copyright: Copyright © 2019 Elsevier Ltd. All rights reserved.]

In this paper a real-time seam tracking algorithm is proposed that can cope with the accuracy demands of robotic laser welding. A trajectory-based control architecture is presented, which had to be developed for this seam tracking algorithm. Cartesian locations (position and orientation) are added to the robot trajectory during the robot motion. In this way, sensor information obtained during the robot motion is used to generate the robot trajectory while moving. Experiments have been performed to prove the tracking capabilities of the seam tracking algorithm.

In this study, a modeling approach is developed to examine laminar flow effects on the rotordynamic behavior of high-speed mini rotating machinery with a moderate flow confinement. The existing research work mostly focuses on the flow-induced forces in small gap systems, such as bearings and seals, in which the flow is mostly laminar and inertia effects are ignored. In other studies, medium gap systems are analyzed, taking the inertia effects into consideration, but the surrounding flow is considered as turbulent. However, in high speed mini rotating machinery, the large clearances and the high speeds make the inertia effects significant, even in the laminar flow regime. In the current study, the flow-induced forces resulting from the surrounding fluid are analyzed and these models are combined with the structural finite element (FE) models for determining the rotordynamic behavior. The structure is analyzed with finite elements based on Timoshenko beam theory. Flow-induced forces, which include inertia effects, are implemented into the structure as added mass-stiffness-damping at each node in the fluid confinement. The shear stress is modeled with empirical and analytical friction coefficients, and the stability, critical speeds, and vibration response of the rotor is investigated for different friction models. In order to validate the developed modeling approach, experiments were conducted on a specially designed setup at different support properties. By comparing the experiments with the theoretical models, the applicability of the different friction models are examined. It was found that the dynamic behavior is estimated better with empirical friction models compared to using the analytical friction models.

Recently, there have been numerous research projects on the development of minirotating machines. These machines mostly operate at speeds above the first critical speed and have special levitation systems. Besides, the multiphysical effects become significant in small scale. Therefore, advanced modeling approaches should be developed and innovative experimental rigs with the foregoing requirements should be constructed in order to test the developed techniques. In the current study, the design of an experimental setup for testing the multiphysical effects has been outlined. First, the previously developed multiphysical models (Dikmen, E., van der Hoogt, P., de Boer, A., and Aarts, R., 2010, “Influence of Multiphysical Effects on the Dynamics of High Speed Minirotors—Part I: Theory,” J. Vibr. Acoust., 132, p. 031010; Dikmen, E., van der Hoogt, P., de Boer, A., and Aarts, R., 2010, “Influence of Multiphysical Effects on the Dynamics of High Speed Minirotors—Part II: Results,” J. Vibr. Acoust., 132, p. 031011) for the analysis of small scale rotors are described briefly for background information. Second, an analysis of the effect of the rotor parameters (diameter, length, rotation speed, etc.) on the dynamics of the rotor under multiphysical effects is presented. Afterward the design process which includes the design decisions based on these results, the availability, simplicity, and applicability of each component is presented in detail. Finally, the experimental results have been presented and the efficiency of the design has been evaluated. In summary, the design requirements for an experimental setup for testing multiphysical effects on minirotors have been analyzed. The design procedure and evaluation of the design have been presented.

In this study the temperature increase and heat dissipation in the air gap of a cylindrical mini rotor stator system has been analyzed. A simple thermal model based on lumped parameter thermal networks has been developed. With this model the temperature dependent air properties for the fluid-rotor interaction models have been calculated. Next the complete system has also been modeled by using computational fluid dynamics (CFD) with Ansys-CFX and Ansys. The results have been compared and the capability of the thermal networks method to calculate the temperature of the air between the rotor and stator of a high speed micro rotor has been discussed.

In this study, a flexible rotor with variable support stiffness has been analyzed. Simple support models consisting of mass, spring systems are extracted from modal analysis of the isolated support and by applying static loads to the finite element model of the supports. The derived equivalent models of the supports are then implemented in the finite element based structural model which predicts the dynamic behavior of the rotor. Finally experimental modal analysis of the rotor is performed with different support stiffnesses. The experimental and theoretical results have been compared and different support modeling approaches have been examined.

A finite element based method is presented for evaluation of linearized dynamic equations of flexible mechanisms about a nominal trajectory. The coefficient matrices of the linearized equations of motion are evaluated as explicit analytical expressions involving mixed sets of generalized co-ordinates of the mechanism with rigid links and deformation mode co-ordinates that characterize deformation of flexible link elements. This task is accomplished by employing the general framework of the geometric transfer function formalism. The proposed method is general in nature and can be applied to spatial mechanisms and manipulators having revolute and prismatic joints. The method also permits investigation of the dynamics of flexible rotors and spinning shafts. Application of the theory is illustrated through a detailed model development of a four-bar mechanism and the analysis of bending vibrations of two single link mechanisms in which the link is considered as a rotating flexible arm or as an unsymmetrical rotating shaft, respectively. The algorithm for the calculation of the matrix coefficients is directly emenable to numerical computation and has been incorporated into the linearization module of the computer program SPACAR.

A finite element - based method is presented for analyzing the dynamic behavior of flexible manipulators, including the effects of the manipulator's control system. The method involves a nonlinear finite-element formulation in which both links and joints are considered as specific finite elements. The governing equations of motion are formulated in terms of two sets of coordinates, namely generalized coordinates of the manipulator with rigid links and deformation mode coordinates that characterize deformation of the links. The method also permits generation of locally linearized models about a nominal trajectory. The numerical performance of the presented finite element method is demonstrated by analyzing the closed-loop behav ior of a flexible three-degree-of-freedom manipulator in which the position of the end effector is to be sensed. On the basis of the linearized system description, controllability is discussed in terms of the modal representations of the system. Uncontrollable manipulator configurations have been indi cated for bending vibrations of the out-of-plane motion of the manipulator. Fast and precise closed-loop tip position control has been obtained for the in-plane motion with a bandwidth that is three times the bandwidth achieved with actuator joint feedback. However, no significant increase in the bandwidth has been obtained for the out-of-plane motion. The improve ment for the latter motion is strongly limited by the nonmini mum phase behavior.

This paper presents a realistic dynamic simulation of the closed-loop tip motion of a rigid-link manipulator with joint friction. The results from two simulation techniques are compared with experimental results. A six-axis industrial Strobot is modelled. The LuGre friction model is used to account both for the sliding and pre-sliding regime. The manipulation task implies transferring a laser spot along a straight line with a trapezoidal velocity profile. Firstly, a non-linear finite element method is used to formulate the dynamic equations of the manipulator mechanism. In a closed-loop simulation the driving torques are generated by the control system. The computed trajectory tracking errors agree well with the experimental results. Unfortunately, the simulation is very time- consuming due to the small time step of the discrete-time controller. Secondly, a perturbation method has been applied. In this method the perturbed motion of the manipulator is modelled as a first-order perturbation of the nominal manipulator motion. Friction torques at the actuator joints are introduced at the stage of perturbed dynamics. A substantial reduction of the computer time is achieved without loss of accuracy.

This paper deals with modelling and identification of flexible-joint robot models that can be used for dynamic simulation and model based control of industrial robots. A nonlinear finite element based method is used to derive the dynamic equations of motion in a form suitable for both simulation and identification. The latter requires that the equations of motion are linear in the dynamic parameters. For accurate simulations of the robot tip motion the model should describe the relevant dynamic properties such as joint friction and flexibilities. Both the drive and the joint flexibilities are included in the model. Joint friction is described by means of a static friction model, including Coulomb and viscous friction components. The dynamic parameters describing mass, inertia, stiffness, damping and friction properties are obtained from a least squares solution of an over determined linear system assembled from closed loop identification experiments. In the identification experiment the robot moves along a prescribed trajectory while all joint angles, flexible deformations and driving torques are recorded. In order to excite joint vibrations during the identification feed forward torques at frequencies above the bandwidth of the control system are superposed on the joint torques. The applicability of the method is demonstrated in a numerical study of a four link industrial robot.

Robotic laser welding imposes high demands on the used manipulator as high accuracies (down to 0.1 mm) have to be reached at high velocities (up to 250 mm/s). To meet these specifications with industrial robots, a sensor measuring at the robot tip needs to be applied.

This paper deals with the modelling and identification of a six axes industrial Sta¨ubli RX90 robot. A non-linear finite element method is used to generate the dynamic equations of motion in a form suitable for both simulation and identification. The latter requires that the equations of motion are linear in the inertia parameters. Joint friction is described by a friction model that describes the friction behaviour in the full velocity range necessary for identification. Experimental parameter identification by means of linear least squares techniques showed to be very suited for identification of the unknown parameters, provided that the problem is properly scaled and that the influence of disturbances is sufficiently analysed and managed. An analysis of the least squares problem by means of a singular value decomposition is preferred as it not only solves the problem of rank deficiency, but it also can correctly deal with measurement noise and unmodelled dynamics.

Full penetration of a weld is an important quality demand in many laser welding applications. Furthermore for economical reasons the highest possible production speed is preferred. To achieve both goals simultaneously, process settings close to partial penetration should be applied. Consequently the risk of losing full penetration increases due to external disturbances or gradual changes in process parameters.In this work a feedback controller is described which is able to search for and operate at the highest possible welding speed given a certain maximum available laser power while at the same time full penetration is maintained. The signal from an optical detector which is placed inside the Nd:YAG laser source is used as a feedback signal. The ability of this detector to monitor the transition from a fully penetrated keyhole to a partially penetrated keyhole weld has been used to design a ‘switching’ controller. In a first feedback control loop the laser power is used as an actuator to operate near the edge of partial penetration. The fast response of this controller can cope with sudden disturbances. A second feedback loop maximizes the welding speed utilizing all available laser power.Full penetration of a weld is an important quality demand in many laser welding applications. Furthermore for economical reasons the highest possible production speed is preferred. To achieve both goals simultaneously, process settings close to partial penetration should be applied. Consequently the risk of losing full penetration increases due to external disturbances or gradual changes in process parameters.In this work a feedback controller is described which is able to search for and operate at the highest possible welding speed given a certain maximum available laser power while at the same time full penetration is maintained. The signal from an optical detector which is placed inside the Nd:YAG laser source is used as a feedback signal. The ability of this detector to monitor the transition from a fully penetrated keyhole to a partially penetrated keyhole weld has been used to design a ‘switching’ controller. I...

This paper presents a trajectory generator, which generates a smooth robot trajectory in real-time. The trajectory generator is based on cubic interpolation, where Cartesian locations (position and orientation) can be added on-the-fly during the robot motion. This way sensor information obtained during the robot motion can be used to generate the robot trajectory. A general control architecture called trajectory-based control is presented in combination with this trajectory generator. Experiments have been carried out which show the capabilities of the trajectory generator to provide a smooth trajectory for the robot joint motion controller.