Visual Acuity in the Flying Snake, Chrysopelea paradisi

Synopsis Visual control during high-speed aerial locomotion requires a visual system adapted for such behaviors. Flying snakes (genus: Chrysopelea) are capable of gliding at speeds up to 11 m s− 1 and perform visual assessments before take-off. Investigating mechanisms of visual control requires a closed-loop experimental system, such as immersive virtual arenas. To characterize vision in the flying snake Chrysopelea paradisi, we used digitally reconstructed models of the head to determine a 3D field of vision. We also used optokinetic drum experiments and compared slow-phase optokinetic nystagmus (OKN) speeds to calculate visual acuity, and conducted preliminary experiments to determine whether snakes would respond to closed-loop virtual stimuli. Visual characterization showed that C. paradisi likely has a large field of view (308.5 ± 6.5° azimuthal range), with a considerable binocular region (33.0 ± 11.0° azimuthal width) that extends overhead. Their visual systems are broadly tuned and motion-sensitive, with mean peak OKN response gains of 0.50 ± 0.11, seen at 46.06 ± 11.08 Hz, and a low spatial acuity, with mean peak gain of 0.92 ± 0.41, seen at 2.89 ± 0.16 cycles per degree (cpd). These characteristics were used to inform settings in an immersive virtual arena, including frame rate, brightness, and stimulus size. In turn, the immersive virtual arena was used to reproduce the optokinetic drum experiments. We elicited OKN in open-loop experiments, with a mean gain of 0.21 ± 0.9, seen at 0.019 ± 6 × 10−5 cpd and 1.79 ± 0.01 Hz. In closed-loop experiments, snakes did not exhibit OKN, but held the image fixed, indicating visual stabilization. These results demonstrate that C. paradisi responds to visual stimuli in a digital virtual arena. The accessibility and adaptability of the virtual setup make it suitable for future studies of visual control in snakes and other animals in an unconstrained setting.

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The Modelling, Simulation and FPGA-Based Implementation for Stepper Motor Wide Range Speed Closed-Loop Drive System Design

Machines ◽

10.3390/machines6040056 ◽

2018 ◽

Vol 6 (4) ◽

pp. 56 ◽

Cited By ~ 1

Author(s):

Chiu-Keng Lai ◽

Jhang-Shan Ciou ◽

Chia-Che Tsai

Keyword(s):

Embedded System ◽

High Speed ◽

Closed Loop ◽

Open Loop ◽

Drive System ◽

Stepper Motor ◽

Motor Drive ◽

Digital Controllers ◽

Loop Control ◽

Wide Range

Owing to the benefits of programmable and parallel processing of field programmable gate arrays (FPGAs), they have been widely used for the realization of digital controllers and motor drive systems. Furthermore, they can be used to integrate several functions as an embedded system. In this paper, based on Matrix Laboratory (Matlab)/Simulink and the FPGA chip, we design and implement a stepper motor drive. Generally, motion control systems driven by a stepper motor can be in open-loop or closed-loop form, and pulse generators are used to generate a series of pulse commands, according to the desired acceleration/run/deceleration, in order to the drive system to rotate the motor. In this paper, the speed and position are designed in closed-loop control, and a vector control strategy is applied to the obtained rotor angle to regulate the phase current of the stepper motor to achieve the performance of operating it in low, medium, and high speed situations. The results of simulations and practical experiments based on the FPGA implemented control system are given to show the performances for wide range speed control.

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Modeling and Analysis for Thermal Control of Spindles for Reconfigurable Machines

10.1115/imece2001/dsc-24584 ◽

2001 ◽

Author(s):

Jeffrey L. Stein ◽

John E. Harder

Keyword(s):

High Speed ◽

Metal Cutting ◽

Closed Loop ◽

Dynamic Performance ◽

Thermal Control ◽

Open Loop ◽

Limiting Factor ◽

Process Conditions ◽

Bearing Load ◽

Bearing Loads

Abstract Control of thermally induced bearing loads remains an important but unsolved problem for precision, high-speed, metal cutting, machining spindles. Spindle dynamic performance, as well as spindle life, depends on bearing loads. Because these loads can change drastically with a change in process conditions, poor spindle dynamic performance, and dramatically reduced bearing life can result. The purpose of this paper is to evaluate the feasibility of controlling bearing loads by controlling the heat generated by a thermal actuator placed around the housing of the spindle. A mathematical model of the open loop response of a laboratory prototype spindle is developed and validated. The model is then used to evaluate the closed loop performance. The results show that closed loop control of the bearing load is achievable in steady state and under bandwidth limited transient conditions. The proposed system has reasonable command authority when additional heat is required, however, it is possible for the system to lose control when the heater is required to “provide” negative heat. This situation can be mitigated by proper choice of initial preload. As expected, measurement noise limits the control gain but is not a limiting factor. More open loop tests are suggested to validate the model under a broader set of conditions. In addition, closed loop validation is suggested. However, based on results obtained it appears bearing load control is achievable by controlling the thermal field around the spindle.

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Introduction to the Six Eye Movement Systems and the Visual Fixation System

Eye Movement Disorders ◽

10.1093/oso/9780195324266.003.0008 ◽

2008 ◽

Author(s):

Agnes Wong

Keyword(s):

Visual Acuity ◽

Eye Movements ◽

High Resolution ◽

Information Overload ◽

Survival Rates ◽

Large Field ◽

Field Of Vision ◽

Very High Spatial Resolution ◽

Different Characteristics ◽

The Brain

One main reason that we make eye movements is to solve a problem of information overload. A large field of vision allows an animal to survey the environment for food and to avoid predators, thus increasing its survival rate. Similarly, a high visual acuity also increases survival rates by allowing an animal to aim at a target more accurately, leading to higher killing rates and more food. However, there are simply not enough neurons in the brain to support a visual system that has high resolution over the entire field of vision. Faced with the competing evolutionary demands for high visual acuity and a large field of vision, an effective strategy is needed so that the brain will not be overwhelmed by a large amount of visual input. Some animals, such as rabbits, give up high resolution in favor of a larger field of vision (rabbits can see nearly 360°), whereas others, such as hawks, restrict their field of vision in return for a high visual acuity (hawks have vision as good as 20/2, about 10 times better than humans). In humans, rather than using one strategy over the other, the retina develops a very high spatial resolution in the center (i.e., the fovea), and a much lower resolution in the periphery. Although this “foveal compromise” strategy solves the problem of information overload, one result is that unless the image of an object of interest happens to fall on the fovea, the image is relegated to the low-resolution retinal periphery. The evolution of a mechanism to move the eyes is therefore necessary to complement this foveal compromise strategy by ensuring that an object of interest is maintained or brought to the fovea. To maintain the image of an object on the fovea, the vestibulo-ocular (VOR) and optokinetic systems generate eye movements to compensate for head motions. Likewise, the saccadic, smooth pursuit, and vergence systems generate eye movements to bring the image of an object of interest on the fovea. These different eye movements have different characteristics and involve different parts of the brain.

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The Design of High-Speed Synchronization Data Collection Node Machine for Multi-Chip CCD Measurement

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.427-429.702 ◽

2013 ◽

Vol 427-429 ◽

pp. 702-707

Author(s):

Li Li ◽

Guo Fu Yin

Keyword(s):

High Speed ◽

Image Data ◽

Large Field ◽

Protocol Stack ◽

Visual Technology ◽

Field Of Vision ◽

Communication Module ◽

Drive Pulse ◽

Performance Results ◽

Ccd Image

The high-speed synchronous node machine is developed for collecting high-precision and synchronous data from multi-chip CCD to measure the dynamic object with large field coverage by Visual technology. Node machine contains core, A/D converter module and Ethernet communication module. The FPGA of 600,000 gates which have a built-in FLASH chip is used as the core, which provides work-frequency of 10MHz and drive pulse for multi-chip CCD. A/D converter module configures the differential amplifier and builds 3-way 30MHz 16-bit A / D converter. 10/100M Ethernet protocol stack controller and RJ45 interface are internally installed in Ethernet module. This module also uses CC2430 chip to perform fast wireless synchronization control. Paper emphasizes how to implement the key technologies of multi-chip CCD for synchronous and precision measurement, and test the node machine by 5-chip CCD image data synchronous collecting with large field of vision. The node machine runs smoothly and reliably .The performance results of test show that the speed of image data collecting reaches up to 1800 frames/s, the speed of data processing reaches up to 150M Bytes/s and the transporting speed reaches up to 50M Bytes/s. The time of synchronous control is within 2 us.

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WindSTORM: Robust online image processing for high-throughput nanoscopy

Science Advances ◽

10.1126/sciadv.aaw0683 ◽

2019 ◽

Vol 5 (4) ◽

pp. eaaw0683 ◽

Cited By ~ 13

Author(s):

Hongqiang Ma ◽

Jianquan Xu ◽

Yang Liu

Keyword(s):

Image Processing ◽

High Throughput ◽

High Speed ◽

High Density ◽

Frame Rate ◽

Large Field ◽

Localization Accuracy ◽

Image Characteristics ◽

Emitter Localization ◽

Online Image Processing

High-throughput nanoscopy becomes increasingly important for unraveling complex biological processes from a large heterogeneous cell population at a nanoscale resolution. High-density emitter localization combined with a large field of view and fast imaging frame rate is commonly used to achieve a high imaging throughput, but the image processing speed and the presence of heterogeneous background in the dense emitter scenario remain a bottleneck. Here, we present a simple non-iterative approach, referred to as WindSTORM, to achieve high-speed high-density emitter localization with robust performance for various image characteristics. We demonstrate that WindSTORM improves the computation speed by two orders of magnitude on CPU and three orders of magnitude upon GPU acceleration to realize online image processing, without compromising localization accuracy. Further, WindSTORM is highly robust to maximize the localization accuracy and minimize the image artifacts in the presence of nonuniform background. WindSTORM paves the way for next generation high-throughput nanoscopy.

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Research on a High-Speed and Heavy-Duty Closed-Loop Drive System of a Two-Phase Hybrid Stepping Motor Based on a Hybrid Controller

Wireless Communications and Mobile Computing ◽

10.1155/2021/2515820 ◽

2021 ◽

Vol 2021 ◽

pp. 1-13

Author(s):

Zhou Yansuo ◽

Leng Yonggang ◽

Lu Wenqi ◽

Li Yu ◽

Li Qingmian ◽

...

Keyword(s):

High Speed ◽

Closed Loop ◽

Position Control ◽

Load Capacity ◽

Open Loop ◽

Drive System ◽

Heavy Duty ◽

Two Phase ◽

Hybrid Controller ◽

State Process

Low load capacity and poor positioning accuracy of stepper motors in high-speed operation are currently two of the bottlenecks that limit their application in high-speed and heavy-duty drive applications. To solve this problem, a hybrid controller is proposed for the high-speed heavy-duty closed-loop stepper motor driving system, which includes two core contents. First, for the position control, a hybrid controller based on position error for open-loop/closed-loop automatic switching-combined spatial current given amplitude and angle automatic adjustment is proposed. Secondly, an advanced angle compensation strategy based on error-integrated feedforward is adopted to compensate for the electrical angle of the combined space current vector. To verify the effectiveness of the proposed method, theoretical analysis and system development as well as testing are carried out. Compared with the traditional open-loop drive system, results show that the maximum operating speed and maximum torque of the newly developed drive system based on the proposed method are improved by 50% and 81.25%, respectively. And at the same set speed and position, the response speed is faster and the accuracy of the steady-state process is higher. In the case of setting higher running speed and load torque, the drive system also maintains high-precision operation.

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EyeLoop: An Open-Source System for High-Speed, Closed-Loop Eye-Tracking

Frontiers in Cellular Neuroscience ◽

10.3389/fncel.2021.779628 ◽

2021 ◽

Vol 15 ◽

Author(s):

Simon Arvin ◽

Rune Nguyen Rasmussen ◽

Keisuke Yonehara

Keyword(s):

Eye Tracking ◽

Open Source ◽

High Speed ◽

Closed Loop ◽

Low Cost ◽

Open Loop ◽

Eye Tracker ◽

High Resource ◽

Real Time Analysis ◽

Loop Design

Eye-trackers are widely used to study nervous system dynamics and neuropathology. Despite this broad utility, eye-tracking remains expensive, hardware-intensive, and proprietary, limiting its use to high-resource facilities. It also does not easily allow for real-time analysis and closed-loop design to link eye movements to neural activity. To address these issues, we developed an open-source eye-tracker – EyeLoop – that uses a highly efficient vectorized pupil detection method to provide uninterrupted tracking and fast online analysis with high accuracy on par with popular eye tracking modules, such as DeepLabCut. This Python-based software easily integrates custom functions using code modules, tracks a multitude of eyes, including in rodents, humans, and non-human primates, and operates at more than 1,000 frames per second on consumer-grade hardware. In this paper, we demonstrate EyeLoop’s utility in an open-loop experiment and in biomedical disease identification, two common applications of eye-tracking. With a remarkably low cost and minimum setup steps, EyeLoop makes high-speed eye-tracking widely accessible.

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Active Gate Driver and Management of the Switching Speed of GaN Transistors during Turn-On and Turn-Off

Electronics ◽

10.3390/electronics10020106 ◽

2021 ◽

Vol 10 (2) ◽

pp. 106

Author(s):

Mamadou Lamine Beye ◽

Thilini Wickramasinghe ◽

Jean François Mogniotte ◽

Luong Viêt Phung ◽

Nadir Idir ◽

...

Keyword(s):

Gate Voltage ◽

High Speed ◽

Closed Loop ◽

Voltage Control ◽

Open Loop ◽

Effective Control ◽

Loop Analysis ◽

Switching Speed ◽

Switching Losses ◽

Electromagnetic Disturbances

The paper investigates the management of drain voltage and current slew rates (i.e., dv/dt and di/dt) of high-speed GaN-based power switches during the transitions. An active gate voltage control (AGVC) is considered for improving the safe operation of a switching cell. In an application of open-loop AGVC, the switching speeds vary significantly with the operating point of the GaN HEMT on either or both current and temperature. A closed-loop AGVC is proposed to operate the switches at a constant speed over different operating points. In order to evaluate the reduction in the electromagnetic disturbances, the common mode currents in the system were compared using the active and a standard gate voltage control (SGVC). The closed-loop analysis carried out in this paper has shown that discrete component-based design can introduce limitations to fully resolve the problem of high switching speeds. To ensure effective control of the switching operations, a response time fewer than 10 ns is required for this uncomplex closed-loop technique despite an increase in switching losses.

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Leakage reduction in fast superconducting qubit gates via optimal control

npj Quantum Information ◽

10.1038/s41534-020-00346-2 ◽

2021 ◽

Vol 7 (1) ◽

Author(s):

M. Werninghaus ◽

D. J. Egger ◽

F. Roy ◽

S. Machnes ◽

F. K. Wilhelm ◽

...

Keyword(s):

Optimal Control ◽

High Speed ◽

Closed Loop ◽

Open Loop ◽

Pulse Generation ◽

High Fidelity ◽

Superconducting Qubit ◽

Loop Optimization ◽

Precise Control ◽

Qubit Operations

AbstractReaching high-speed, high-fidelity qubit operations requires precise control over the shape of the underlying pulses. For weakly anharmonic systems, such as superconducting transmon qubits, short gates lead to leakage to states outside of the computational subspace. Control pulses designed with open-loop optimal control may reduce such leakage. However, model inaccuracies can severely limit the usability of such pulses. We implemented a closed-loop optimization that simultaneously adapts all control parameters based on measurements of a cost function built from Clifford gates. We directly optimize the amplitude and phase of each sample point of the digitized control pulse. We thereby fully exploit the capabilities of the pulse generation electronics and create a 4.16 ns single-qubit pulse with 99.76 % fidelity and 0.044 % leakage. This is a sevenfold reduction of the leakage rate and a threefold reduction in standard errors of the best DRAG pulse we have calibrated at such short durations on the same system.

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