This paper deals with force-reflecting control design for teleoperation of bilateral robots under unknown constant time delay. The proposed impedance teleoperator control is based on integral sliding ...mode approaches, avoiding undesirable chattering effect. With the aim of implementing the proposed controller and taking into account that only position measurement is available, a Nonlinear Observer based on Super Twisting Algorithm is proposed to estimate velocity and acceleration in the slave side of the teleoperation system. Furthermore, owing to the finite-time convergence properties of the observer, the proposed control scheme guarantees robust tracking under unknown constant time delay. Experimental results illustrate the effectiveness of the proposed scheme.
A novel adaptive super-twisting control algorithm, for Unmanned Surface Vehicles (USV) tracking control is presented. The proposed adaptive law is obtained using a Lyapunov approach, to analyze the ...system closed-loop stability. Furthermore, several conditions are given to guarantee robustness in presence of unknown bounded disturbances/uncertainties, chattering mitigation and the finite-time convergence. This adaptive control strategy has the advantage that the controller gains, which are in terms of a single control parameter, requires adjusting a small number of parameters compared with other adaptive strategies, moreover and its dynamics is smooth, improving the controller performance. To assess the proposed control methodology effectiveness, a trajectory tracking control is designed and implemented on an unmanned surface vehicle under the action of bounded unknown uncertainties and external perturbations. Numerical simulations and experimental results conducted with a vessel prototype demonstrate the performance and advantages under payload variations and external environmental conditions. Finally, a comparative study between the proposed approach with other adaptive super-twisting works has been conducted.
•A novel adaptive gain is designed for the super-twisting controller, reducing the number of tuning parameters.•A trajectory tracking control for an unmanned surface vehicle under perturbations validates the proposed method.•Reduced parameters of the adaptive gain provides a smooth rate of change and does not require sliding mode detector.•Experimental results demonstrates the performance and feasibility of the proposed adaptive super twisting controller.
The bark beetles of the genus Dendroctonus feed on phloem that is a nitrogen-limited source. Nitrogen fixation and nitrogen recycling may compensate or alleviate such a limitation, and ...beetle-associated bacteria capable of such processes were identified. Raoultella terrigena, a diazotrophic bacteria present in the gut of Dendroctonus rhizophagus and D. valens, exhibited high acetylene reduction activity in vitro with different carbon sources, and its nifH and nifD genes were sequenced. Bacteria able to recycle uric acid were Pseudomonas fluorescens DVL3A that used it as carbon and nitrogen source, Serratia proteomaculans 2A CDF and Rahnella aquatilis 6-DR that used uric acid as sole nitrogen source. Also, this is the first report about the uric acid content in whole eggs, larvae, and adults (male and female) samples of the red turpentine beetle (Dendroctonus valens). Our results suggest that the gut bacteria of these bark beetles could contribute to insect N balance.
Intracranial pial arteriovenous fistulas, also known as nongalenic fistulas, are rare vascular malformations affecting predominantly the pediatric population. Hydrocephalus is an unusual presentation ...in which the exact pathophysiology is not fully understood. The aim of treatment in these cases is occlusion of the fistula prior to considering ventricular shunting. Here, the authors describe the hydrodynamic considerations of the paravascular pathway and the resolution of hydrocephalus with endovascular treatment of the fistula.
The effect of extrusion cooking on bioactive compounds in third-generation snacks (TGSE) and microwave-expanded snacks (MWSE) prepared using black bean, blue maize, and chard (FBCS) was evaluated. ...FBCS was extruded at different moisture contents (MC; 22.2–35.7%), extrusion temperatures (ET; 102–142 °C), and screw speeds (SP; 96–171 rpm). Total anthocyanin content (TAC), contents of individual anthocyanins, viz., cyanidin-3-glucoside, malvidin-3-glucoside, pelargonidin-3-glucoside, pelargonidin-3-5-diglucoside, and delphinidin-3-glucoside chloride, total phenolic content (TPC), antioxidant activity (AA), and color parameters were determined. TAC and individual anthocyanin levels increased with the reduction in ET. ET and MC affected the chemical and color properties; increase in ET caused a significant reduction in TPC and AA. Microwave expansion reduced anthocyanin content and AA, and increased TPC. Extrusion under optimal conditions (29% MC, 111 rpm, and 120 °C) generated products with a high retention of functional compounds, with high TAC (41.81%) and TPC (28.23%). Experimental validation of optimized process parameters yielded an average error of 13.73% from the predicted contents of individual anthocyanins. Results suggest that the TGSE of FBCS obtained by combining extrusion and microwave expansion achieved significant retention of bioactive compounds having potential physiological benefits for humans.
We present a series that describes the presenting features and clinical outcomes in patients with CSDH treated with a standardised technique and an open-drain placement.
We reviewed the medical ...records of 155 consecutive patients at a single centre who underwent CSDH evacuation by placing burr holes, accompanied by intraoperative irrigation and a subdural Penrose drain between 2014 and 2018.
The mean age was 65.9 years, 81.9% were males. The most common clinical characteristics were an altered mental state (21.9%) and headache (12.9%). It was necessary to perform a second surgical intervention due to the evidence in the postoperative tomography of a residual hematoma in 10.3% of the cases; there were 2 cases of recurrence in 6 months (1.3%). Pneumonia (6.5%) and seizures (5.8%) were the most frequent medical complications. Intracranial infections accounted for 1.9%, and the mortality rate was 6.4% of cases.
We provided our experience with a low-cost and less-commonly used technique in the management of CSDH. This technique showed similar recurrence, mortality and intracranial infection rates to those reported in the literature for closed drainage systems. Additional studies will be required to assess this technique.
In this paper, simultaneous state estimation and parameters identification for a class of nonlinear systems are addressed. With the aim of solving this problem, an adaptive observer based on the ...sliding mode (AOSM) approach is designed. The main advantage of the proposed adaptive observer design is that it combines the robustness and finite time convergence of the sliding mode observers, with the simplicity of tuning of high-gain observers, reducing tuning effort. The finite time convergence of the proposed adaptive observer is established using a Lyapunov approach. Furthermore, a comparative study of the proposed adaptive observer against schemes from literature is presented, in order to show the advantages of the proposed approach. Finally, numerical results are provided to demonstrate the effectiveness and performance of the proposed approach under noise and external disturbances.
•The adaptive observer estimates states and identifies unknown parameters.•Sufficient conditions guarantee the finite-time convergence.•Stability analysis for closed-loop is simplified, due to separation principle holds.•The proposed adaptive observer presents better performance and robustness.
In this paper, an alternative approach for extracting the angular position estimation error for an Interior Permanent Magnet Synchronous Machine (IPMSM) is introduced.
The originality of this work ...consists on obtaining the angular position estimation error by the measurable currents, in the αβ stationary reference frame, without considering the high frequency signal injection. Then, using the obtained angular position estimation error, an Adaptive High Order Sliding Mode Observer (AHOSMO) is proposed for estimating the position, speed and acceleration of the IPMSM. The observer is used for a parameter-free virtual dynamical system to avoid impact of the parameter variations on the estimation. The convergence analysis of the proposed observer is established using a Lyapunov stability theory. Furthermore, simulation and experimental results are presented to illustrate the efficiency of the proposed approach against disturbances and noises. The proposed approach is compared with high frequency (HF) and back electromotive force (BEMF) approaches.
This paper addresses the design of a continuous super twisting control combined with a high-order sliding mode observer for a class of nonlinear systems. An analysis of closed-loop stability is ...provided by means of Lyapunov approach, where sufficient conditions are given to ensure the convergence and to select the gains of the proposed controller. Numerical simulation and experimental results illustrate the performance of the proposed control-observer scheme for controlling the altitude of a quad-rotor aircraft. Furthermore, a comparative study against similar approaches from literature is included for illustrating that proposed methodology requires less control effort while shows the best performance.
•An observer-based control design based on a Simplified Super Twisting for a class of nonlinear systems is presented.•Reduction on tuning effort by means of a condition on controller and observer gains, which facilitates its implementation.•Sufficient conditions are given to guarantee finite-time stability using Lyapunov approach.•Simulation and experimental results show the performance of proposed observer-control.•Proposed scheme shows the best performance among tested controllers, as control signal is smoother and requires less control effort.
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