摘要 :
This article presents the design and tests of a closed-loop controlled microwave
beamformer for phased arrays. The proposed circuit owns an internal reference
signal used to automatically set predefined amplitudes and phases of ...
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This article presents the design and tests of a closed-loop controlled microwave
beamformer for phased arrays. The proposed circuit owns an internal reference
signal used to automatically set predefined amplitudes and phases of the
beamformer branches. This signal is applied to the branches through directional
couplers with high directivity and propagates in them similar to the
actual signals coming from the antenna array. As a consequence of this architecture,
we found that the impedance mismatch between the antennas and the
beamformer as well as the mutual coupling in the array is taken into account
during calibration, resulting in a more accurate adjustment of amplitudes and
phases. In this work, the influence of the mutual coupling between the antennas
and the directivity of the couplers on the beamforming calibration uncertainty
is also analyzed. From the derived uncertainties, the corresponding
pattern degradation is evaluated by performing Monte Carlo simulations. It is
shown that using couplers with low directivity together with tightly coupled
arrays can produce undesirable main lobe squints of up to 4.5, main lobe level
deviations of up to 4.2 dB, and side lobe level variations of up to 24 dB. On the
other hand, the use of high directivity couplers can mitigate these problems.
Lastly, the validation of the designed circuit is conducted in two stages: bench
tests and measurements in an anechoic chamber with an array of six printed
monopoles operating at 2.2 GHz. Amplitude and phase calibration errors less
than 0.5 dB and 3, respectively, were observed in the bench tests.
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In this paper, an experimental study on the buckling and postbuckling control of a laminated composite beam with eccentrically embedded NiTi actuators is performed. For the purpose of enhancing the critical buckling load, buckling...
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In this paper, an experimental study on the buckling and postbuckling control of a laminated composite beam with eccentrically embedded NiTi actuators is performed. For the purpose of enhancing the critical buckling load, buckling control is investigated through the use of reactive moment associated with the shape recovery force of NiTi actuators. To improve the control authority for the buckling and postbuckling control of the NiTi-composite beam, closed-loop control is used. The buckling and postbuckling control behaviours are presented and discussed qualitatively and quantitatively on load-deflection plots considering stacking sequence of the laminate, slenderness ratio of the beam and activation conditions of the NiTi actuators. The experimental results show that the buckling control can be extended to the postbuckling of the NiTi-composite beam with the proper reactive moment.
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Combining 3D printing and smart materials, 4D printing technologies enable the printed actuators to further change their shapes or other properties after prototyping. However, the shape morphing of 4D printed actuators suffers fro...
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Combining 3D printing and smart materials, 4D printing technologies enable the printed actuators to further change their shapes or other properties after prototyping. However, the shape morphing of 4D printed actuators suffers from poor controllability and low precision. One of the main challenges is that the 4D printed actuators are hard to be modeled and it is difficult to develop an appropriate controller for them. In this study, various popular reinforcement learning (RL) methods are applied to address the problem of online and adaptive model-free control of 4D printed shape memory polymer (SMP). Their training efficiencies are compared and an adaptive LQR controller based on Q learning is developed to realize efficient online learning. The RL controller achieves precise and quick shape control within 2 -3 learning episodes and is adaptive to the changing properties of SMP. The RL controller performance is then compared with a model-based LQR controller and shows high control precision and excellent adaptability to the varying control plant.
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The <1 Hz EEG slow oscillation (SO) is a hallmark of slow-wave sleep (SWS) and is critically involved in sleep-associated memory formation. Previous studies showed that SOs and associated memory function can be effectively enhanced by closed-loop auditory stimulation, when clicks are presented in synchrony with upcoming SO up states. However, increasing SOs and synchronized excitability also bear the risk of emerging seizure activity, suggesting the presence of mechanisms in the healthy brain that counter developing hypersynchronicity during SOs. Here, we aimed to test the limits of driving SOs through closed-loop auditory stimulation in healthy humans. Study I tested a "Driving stimulation" protocol (vs "Sham") in which trains of clicks were presented in synchrony with SO up states basically as long as an ongoing SO train was identified on-line. Study II compared Driving stimulation with a "2-Click" protocol where the maximum of stimuli delivered in a train was limited to two clicks. Stimulation was applied during SWS in the first 210 min of nocturnal sleep. Before and after sleep declarative word-pair memories were tested. Compared with the Sham control, Driving stimulation prolonged SO trains and enhanced SO amplitudes, phase-locked spindle activity, and overnight retention of word pairs (all ps < 0.05). Importantly, effects of Driving stimulation did not exceed those of 2-Click stimulation (p > 0.180), indicating the presence of a mechanism preventing the development of hypersynchronicity during SO activity. Assessment of temporal dynamics revealed a rapidly fading phase-locked spindle activity during repetitive cli...
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The <1 Hz EEG slow oscillation (SO) is a hallmark of slow-wave sleep (SWS) and is critically involved in sleep-associated memory formation. Previous studies showed that SOs and associated memory function can be effectively enhanced by closed-loop auditory stimulation, when clicks are presented in synchrony with upcoming SO up states. However, increasing SOs and synchronized excitability also bear the risk of emerging seizure activity, suggesting the presence of mechanisms in the healthy brain that counter developing hypersynchronicity during SOs. Here, we aimed to test the limits of driving SOs through closed-loop auditory stimulation in healthy humans. Study I tested a "Driving stimulation" protocol (vs "Sham") in which trains of clicks were presented in synchrony with SO up states basically as long as an ongoing SO train was identified on-line. Study II compared Driving stimulation with a "2-Click" protocol where the maximum of stimuli delivered in a train was limited to two clicks. Stimulation was applied during SWS in the first 210 min of nocturnal sleep. Before and after sleep declarative word-pair memories were tested. Compared with the Sham control, Driving stimulation prolonged SO trains and enhanced SO amplitudes, phase-locked spindle activity, and overnight retention of word pairs (all ps < 0.05). Importantly, effects of Driving stimulation did not exceed those of 2-Click stimulation (p > 0.180), indicating the presence of a mechanism preventing the development of hypersynchronicity during SO activity. Assessment of temporal dynamics revealed a rapidly fading phase-locked spindle activity during repetitive click stimulation, suggesting that spindle refractoriness contributes to this protective mechanism.
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The use of a multiple-input buck-boost converter for budgeting power between different energy sources is discussed. It is shown mathematically that the idealized converter can accommodate arbitrary power commands for each input so...
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The use of a multiple-input buck-boost converter for budgeting power between different energy sources is discussed. It is shown mathematically that the idealized converter can accommodate arbitrary power commands for each input source while maintaining a prescribed output voltage. Power budgeting is demonstrated experimentally for a real converter under various circumstances, including a two-input (solar and line-powered) system. A closed-loop control example involving simultaneous tracking of output voltage and set-point tracking of the solar array shows that an autonomous system is realizable.
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In this work, novel Shape Memory Alloy (SMA)-based actuators are proposed to provide angular displacements in both clockwise and counter-clockwise directions with compliance. A bidirectional SMA rotating actuator is fabricated usi...
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In this work, novel Shape Memory Alloy (SMA)-based actuators are proposed to provide angular displacements in both clockwise and counter-clockwise directions with compliance. A bidirectional SMA rotating actuator is fabricated using a rotating frame and two SMA wire-based actuating units similar to human skeletal muscle systems without any additional complicated rotational driving mechanism. These actuating units are activated independently to provide bidirectional rotary motions by using sequentially coordinated electrical inputs. The mechanical, thermal, and electrical properties of the bidirectional SMA rotating actuator are also characterized experimentally. The design and manipulation of the proposed actuator are experimentally verified with simple open-loop and closed-loop control strategies. (C) 2019 Elsevier B.V. All rights reserved.
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This article presents the development of an implanted artificial urethral valve that is used for the treatment of urinary incontinence, with emphasis on a transcutaneous power transmission system with closed-loop thermal control f...
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This article presents the development of an implanted artificial urethral valve that is used for the treatment of urinary incontinence, with emphasis on a transcutaneous power transmission system with closed-loop thermal control function. The valve uses a shape memory alloy (SMA) plate as the actuator, which is activated with batteries placed outside a patient's body using a transcutaneous power transmission system. The power transmission system is equipped with an implanted temperature monitor circuit and a temperature controller to prevent the SMA actuator from being overheated during a prolonged urination. Laboratory experiments and animal experiments, both in vitro and in vivo, show that the developed power transmission system can successfully control the temperature of the SMA actuator to activate the valve without excessive heating of the SMA actuator.
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In this paper, a simple and efficient design method of multi-loop PI controllers is proposed byextending the Maclaurin series approach to a multi-loop control system. The controller parameter of amultiloop system is related to tha...
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In this paper, a simple and efficient design method of multi-loop PI controllers is proposed byextending the Maclaurin series approach to a multi-loop control system. The controller parameter of amultiloop system is related to that of a SISO non-interacting system with an interaction factor in thesimple multiplication form. Based on this relation, analytical tuning rules for a multi-loop PI controllerare derived for several representative process models. In order to improve both performance androbustness of the multi-loop control system, the multi-loop Ms criterion is utilized as a performancecost function. The simulation studies confirm the effectiveness of the proposed method.
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An adaptive alignment scheme for packaging two-dimensional (2D) arrays of optoelectronic systems interconnected by free-space optics is presented. A method of using three quadrant detectors to detect alignment errors in six degree...
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An adaptive alignment scheme for packaging two-dimensional (2D) arrays of optoelectronic systems interconnected by free-space optics is presented. A method of using three quadrant detectors to detect alignment errors in six degrees of freedom is described. However, the complexity of this system increases due to the interactions among the detected error signals. A novel control algorithm is presented to eliminate the interaction and simplify the design of the closed-loop feedback control. A computer simulation compares different algorithms and shows the effectiveness of the proposed algorithm. An experimental closed-loop feedback system demonstrated the principle of the error detection and correction of the proposed system with initial errors in multiple degrees of freedom
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The shape memory alloy (SMA) is increasingly utilized among many industrial and civil applications as it is small in size but mighty in output. However, most of the current SMA-based mechanisms face with the low controllability or...
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The shape memory alloy (SMA) is increasingly utilized among many industrial and civil applications as it is small in size but mighty in output. However, most of the current SMA-based mechanisms face with the low controllability or bulk dimension. In this paper, a novel flexible SMA wire-based gripper is developed to address these challenges for improving the clamping stability and stroke for confined operation. To achieve this, the long SMA wire was spaced smartly within a miniature space to increase the output, further, to improve the stroke of the gripper (14 mm vs conventional 2 mm). Then, the theoretical model of the system was established by considering the thermal effect of SMA material and the static performance of the flexible beams. After that, the experimental setups were prototyped to crossly test the performances of the proposed SMA gripper. It can be seen from the experimental results that the model presented in this paper can be validated with high accuracy (error: 3.4%). It can also be found that the SMA gripper can realize the high tracking performances (i.e. 8.9% accuracy in displacement step response, 10.8% in displacement tracking response, and 12.1% accuracy in clamping force tracking response, respectively) for the industrial applications.
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