一种基于迈斯纳效应的超导电机的驱动力的计算

超导体的迈斯纳效应是超导体的特有的性质之一,超导驱动的电机正是利用超导体的这个性质而设计的一种新型电机,由于驱动原理与传统的电机有很大的不同,这种电机的驱动力的计算一直是这种超导电机设计中要解决的主要问题,针对一种结构的电机,利用理论分析和数值计算的方法计算了一种基于超导体迈斯纳效应的超导电机驱动力的大小,为这种电机的设计提供了主要依据。     

某光电吊舱内方位电机组件低温摩擦特性分析研究

为提升产品可靠性和环境适应性，需对某光电吊舱内方位电机组件在-50℃的摩擦特性进行改善。分析了可能影响电机组件摩擦特性的因素，并针对各因素提出相应的改善措施，借助仿真与试验相结合的研究方法，对改善措施的效果进行了验证。经研究:-50℃时，电机组件摩擦力矩的增大既有低温单独作用的结果，也有低温和电机组件潜在因素共同作用的结果。电机组件在低温下的微变形不足以引起摩擦力矩的增大，通过增加电机保护罩和在电机与电机座之间增加厚度为1 mm的软磁合金薄片，能使电机的摩擦力矩降低到0.063 N·m。该改善措施适用于光电吊舱电机组件的设计及类似产品的开发研制。     

Quantitative analysis of asymmetrical cortical activity in motor areas during sequential finger movement

Brain asymmetry is a phenomenon well known for handedness and has been studied in motor cortices. However, few quantitative studies on asymmetrical cortical activity in motor areas have been conducted. In this study, we systematically investigated asymmetrical cortical activity in motor areas during sequential finger movement by quantitatively analyzing functional magnetic resonance imaging (fMRI) blood oxygenation level-dependent (BOLD) responses. The norm of BOLD signal percentage of change was introduced to quantitatively measure the BOLD signal intensity change difference between the left and right motor areas. The results of the data collected from six subjects show that the norm of BOLD signal percentage of change in the right motor area is higher than that in the left motor area for two-hand movement (P=.0059) and single-hand movement (P=.0279) with right-handedness. These results from fMRI show the asymmetry of motor areas and may suggest that the left hemisphere motor area comes into being as an adaptation system that needs few neuron cells only to finish any movement task for right-handedness. The activation intensity in the left motor area is reduced with normal right finger movement. The activation intensity in the right motor area is obviously higher than that in the left motor area.     

光电伺服机构电机选型问题研究

在轻量化设计需求日益提升的环境下,驱动电机的选型直接影响系统整体尺寸和质量,传统的电机选型方法存在着载荷分析不全面、针对某些影响因素定量化程度不深等问题,因此对电机选型方法的研究和选型工具的开发对于伺服系统的轻量化设计有着较大的影响。对光电伺服系统的各种载荷进行定量化计算,对于难以精确计算的载荷,给出其估算方法,并对电机的动态特性进行校核,引入了置信度的概念辅助电机选型。基于Matlab/GUI编写了伺服电机选型软件,并针对某光电吊舱进行电机选型,最终选得置信度为0.79的直流电机。     

A traveling wave ultrasonic motor of high torque

A traveling wave ultrasonic motor of high torque with a new configuration is proposed in this paper. In the new design, a part of the motor serves as the stator. The rotor is the vibrator consisting of a toothed metal ring with piezoelectric ceramic bonded, which generates ultrasonic vibration. The rotor is in contact with the shell of motor and is driven by the friction between the rotor and the stator. This configuration not only removes the rotor in a conventional type of traveling wave ultrasonic motor but also changes the interaction between the rotor and the stator of the motor so that it improves the output performance of the motor. Although an electric brush is added to the ultrasonic motor, it is easy to be fabricated because of the low speed of motor. The finite element method was used to compute the vibration modes of an ultrasonic motor with a diameter of 100mm to optimize the design of the motor. A 9th mode was chosen as the operation mode with a resonance frequency about 25 kHz. According to the design, a prototype was fabricated. Its performance was measured. The rotation speed-torque curves for various frequencies were obtained. The result shows that its stall torque is greater than 4 Nm within a range of 400 Hz. This ultrasonic motor was used to drive the window glass of a mobile car and the result was satisfactory. In the further the research on the friction material between the stator and the rotor is under way to improve the efficiency of the ultrasonic motor.     

Dynamic instability of collective myosin Ⅱ motors

Some kinds of muscles can oscillate spontaneously,which is related to the dynamic instability of the collective motors.Based on the two-state ratchet model and with consideration of the motor stiffness,the dynamics of collective myosin Ⅱmotors are studied.It is shown that when the motor stiffness is small,the velocity of the collective motors decreases monotonically with load increasing.When the motor stiffness becomes large,dynamic instability appears in the forcevelocity relationship of the collective-motor transport.For a large enough motor stiffness,the zero-velocity point lies in the unstable range of the force-velocity curve,and the motor system becomes unstable before the motion is stopped,so spontaneous oscillations can be generated if the system is elastically coupled to its environment via a spring.The oscillation frequency is related to the motor stiffness,motor binding rate,spring stiffness,and the width of the ATP excitation interval.For a medium motor stiffness,the zero-velocity point lies outside the unstable range of the force-velocity curve,and the motion will be stopped before the instability occurs.     

螺旋天线步进电机控制系统仿真及运行曲线优化

为实现机械相控阵列天线的波束扫描,采用步进电机驱动螺旋天线单元转动来达到预定的辐射相位。为了优化步进电机的开环控制,研究运行曲线对步进电机控制性能的影响,提高步进电机控制速度和精度。根据步进电机及控制系统的工作原理,建立了基于Simulink的步进电机开环控制系统仿真模型,并在此基础上对梯形和抛物线两种运行曲线进行了仿真研究。仿真结果表明,该仿真模型能精确实现两种运行曲线对步进电机的控制,在100 ms的控制周期内,采用梯形运行曲线步进电机的最大无失步转动角度能够达到270°,而采用抛物线运行曲线时其转动角度能够达到360°,抛物线运行曲线在开环控制系统中具有更高的控制速度。     

基于三磷酸腺苷调节的分子马达单向能量跃迁模型

分子马达的梯跳运动和在过阻尼溶液中动力学原理尚未揭示清楚, 从分子马达输运特点和实验现象出发, 构建满足朗之万方程的单向能量跃迁模型, 并通过Monte Carlo方法分析了分子马达的随机动力学行为. 结果表明, 在合适的跃迁能量作用下, 分子马达可以利用噪声进行稳定的梯跳运动和有效的输运, 但负载力会减弱分子马达系统的输运能力; 轨道周期势虽影响分子马达速度的大小但不会改变其运动方向, 分子马达运动方向由跃迁能量决定; 另外, 虽然在不同的噪声强度时平均速度不为零, 但是分子马达系统的高效输运对噪声有一定选择性. 关键词： 分子马达 能量跃迁 朗之万方程 噪声强度     

Chemomechanical Coupling of Molecular Motors: Thermodynamics, Network Representations, and Balance Conditions

Molecular motors are considered that convert the chemical energy released from the hydrolysis of adenosine triphosphate (ATP) into mechanical work. Such a motor represents a small system that is coupled to a heat reservoir, a work reservoir, and particle reservoirs for ATP, adenosine diphosphate (ADP), and inorganic phosphate (P). The discrete state space of the motor is defined in terms of the chemical composition of its catalytic domains. Each motor state represents an ensemble of molecular conformations that are thermally equilibrated. The motor states together with the possible transitions between neighboring states define a network representation of the motor. The motor dynamics is described by a continuous-time Markov process (or master equation) on this network. The consistency between thermodynamics and network dynamics implies (i) local and nonlocal balance conditions for the transition rates of the motor and (ii) an underlying landscape of internal energies for the motor states. The local balance conditions can be interpreted in terms of constrained equilibria between neighboring motor states; the nonlocal balance conditions pinpoint chemical and/or mechanical nonequilibrium.     

Drift coefficients of motor proteins moving along sidesteps

In the paper, we investigate two motor proteins moving along the sidesteps： a motor protein moving along a two- dimensional sidestep and another protein moving along a three-dimensional sidestep. The drift coefficients （or stationary average velocities） of these two motor proteins are calculated. We believe that our investigation of the motor proteins moving along the sidesteps in the present paper can benefit the investigation of the transport of the motor proteins to some extent.     

无电刷法拉第模型电动机的动力学原理

法拉第电动机使用电刷改变流经转子线圈中电流的方向,若无电刷的情况下法拉第电动机似乎不能维持转动.事实上无电刷法拉第模型电动机在人为给转子线圈初始角动量的情况下却可以不停地转动.提出了转子线圈转轴跳动假设,给出无电刷法拉第模型电动机转动的动力学解释,并得到实验验证.     

Coupling of two motor proteins: a new motor can move faster

We study the effect of a coupling between two motor domains in highly processive motor protein complexes. A simple stochastic discrete model, in which the two parts of the protein molecule interact through some energy potential, is presented. The exact analytical solutions for the dynamic properties of the combined motor species, such as the velocity and dispersion, are derived in terms of the properties of free individual motor domains and the interaction potential. It is shown that the coupling between the motor domains can create a more efficient motor protein that can move faster than individual particles. The results are applied to analyze the motion of RecBCD helicase molecules.     

电机温度时滞耦合系统自抗扰控制仿真研究

电机温度过高会造成绝缘性能老化,电机安全性能下降。电机控制系统是典型的非线性系统,电机温度也因此具有时滞性和耦合性的特点,难以建立准确的数学模型。传统的方法对电机温度的控制精度较差,从而导致电机温度失控。为此,提出基于BP神经网络自抗扰控制算法的电机时滞耦合关系下温度控制方法。将BP神经网络与PID控制方法相结合建立电机温度网络自抗扰控制器模型,利用梯度下降法修正电机温度控制器模型的权值系数,从而实现了BP神经网络自抗扰控制器参数的实时调整。实验结果表明,利用BP神经网络自抗扰算法进行电机时滞耦合关系下温度调整,能够有效提高控制的精确度,缩短了控制过程中的时间延时。     

基于永磁同步电机的光电设备新型驱动研究

针对目前光电设备中直流电机的惯量大、成本高、需要维护等问题,提出了交流伺服控制系统,以适应新型光电设备的发展要求或替代目前的直流控制系统。以永磁同步电机为控制对象,分析了永磁同步电机的磁场定向矢量控制原理,以获得类似直流电动机的控制效果。通过复合式光电编码器确定永磁同步电动机转子的初始位置,设计了永磁同步电机伺服控制系统的硬件电路。以id-0的矢量控制方法实现了永磁同步电机位置闭环伺服控制,能够满足新型光电设备跟踪控制系统的快速与稳定性要求。     

一种基于迈斯纳效应的超导电机

超导电机是基于低温环境下超导体迈斯纳效应应用的一种新型旋转电机．该电机有常规电机无法比拟的优良特性：具有高速，结构简单和低损耗的特点．近年来得到发展，特别是在航空，航海，卫星等高科技领域的应用．本文讨论了应用迈斯纳效应的超导电机的工作原理，电机的设计方案．着眼于工程制造，应用有限元方法针对电机设计进行了可行性分析，并对电机性能进行了理论评估．     

Correlating magnetic resonance imaging markers of axonal injury and demyelination in motor impairment secondary to stroke and multiple sclerosis

The primary pathological mechanisms in stroke and multiple sclerosis (MS) are very different but in both diseases, impairment may arise from a final common pathway of axonal damage. We aimed to examine the relationship between motor impairment, magnetisation transfer ratio (MTR) (an index of demyelination), and N-acetyl aspartate (NAA) loss (an index of axonal injury) localised to the descending motor pathways in stroke and MS. Twelve patients between 1 and 10 months after first ischaemic stroke causing a motor deficit and 12 patients with stable MS with asymmetric motor deficit were examined. T(2)-weighted imaging of the brain together with MTR and proton (voxel 1.5x2x2 cm(3)) MRS localised to the posterior limb of the internal capsule were performed and correlated to a composite motor deficit score. MTR and NAA in the internal capsule were reduced in both stroke and MS patients compared to controls. NAA loss correlated with motor deficit score in both stroke and MS (p<0.001 and p = 0.04, respectively). Correlations were seen between MTR and motor deficit (p<0.001) MTR and NAA loss (p <0.001) in stroke patients but not in MS patients. Axonal injury in the descending motor tracts would appear to be an important determinant of motor impairment in both stroke and MS. In stroke, MTR measures of demyelination are closely related to axonal damage and thus also correlate with motor deficit. However in MS, MTR measures of demyelination do not correlate with NAA loss or motor deficit suggesting that demyelination and gliosis may occur independently of axonal damage and are less closely linked with functional impairment.     

Relationships between Gross Motor Abilities and Sensory Processing in Children Aged 18 to 36 Months

OBJECTIVE: We investigated the relationship between gross motor abilities and sensory processing in typically developing children. METHOD: Participants included children aged 18 to 36 months (N = 48). All participants were full-term infants. We assessed gross motor abilities based on the Gross Motor Function Measure (GMFM), and sensory processing characteristics based on the Infant/Toddler Sensory Profile (ITSP). The gross motor ability index was calculated using GMFM score which was estimated from the age. Pearson''s product moment correlation coefficients were used to examine the relationships between the gross motor ability indexes and ITSP section scores. RESULTS: Our findings showed that gross motor ability may be related to oral sensory processing. The children who were more responsive to oral sensory processing tended to exhibit gross motor abilities below the standard for that age. CONCLUSION: Gross motor abilities were related with sensory processing, especially oral sensory processing, in children aged 18 to 36 months.     

Both projection and commissural pathways are disrupted in individuals with chronic stroke: investigating microstructural white matter correlates of motor recovery

ABSTRACT: BACKGROUND: Complete recovery of motor function after stroke is rare with deficits persisting into the chronic phase of recovery. Diffusion tensor imaging (DTI) can evaluate relationships between white matter microstructure and motor function after stroke. The objective of this investigation was to characterize microstructural fiber integrity of motor and sensory regions of the corpus callosum (CC) and descending motor outputs of the posterior limb of the internal capsule (PLIC) in individuals with chronic stroke and evaluate the relationships between white matter integrity and motor function. RESULTS: Standardized measures of upper extremity motor function were measured in thirteen individuals with chronic stroke. Manual dexterity was assessed in thirteen healthy age-matched control participants. DTI scans were completed for each participant. Fractional anisotropy (FA) of a cross-section of sensory and motor regions of the CC and the PLIC bilaterally were quantified. Multivariate analysis of variance evaluated differences between stroke and healthy groups. Correlational analyses were conducted for measures of motor function and FA. The stroke group exhibited reduced FA in the sensory (p = 0.001) region of the CC, contra- (p = 0.032) and ipsilesional (p = 0.001) PLIC, but not the motor region of the CC (p = 0.236). In the stroke group, significant correlations between contralesional PLIC FA and level of physical impairment (p = 0.005), grip strength (p = 0.006) and hand dexterity (p = 0.036) were observed. CONCLUSIONS: Microstructural status of the sensory region of the CC is reduced in chronic stroke. Future work is needed to explore relationships between callosal sensorimotor fiber integrity and interhemispheric interactions post-stroke. In addition, contralesional primary motor output tract integrity is uniquely and closely associated with multiple dimensions of motor recovery in the chronic phase of stroke suggesting it may be an important biomarker of overall motor recovery.     

Dual-hemisphere tDCS facilitates greater improvements for healthy subjects' non-dominant hand compared to uni-hemisphere stimulation

Background  

Transcranial direct current stimulation (tDCS) is a non-invasive technique that has been found to modulate the excitability of neurons in the brain. The polarity of the current applied to the scalp determines the effects of tDCS on the underlying tissue: anodal tDCS increases excitability, whereas cathodal tDCS decreases excitability. Research has shown that applying anodal tDCS to the non-dominant motor cortex can improve motor performance for the non-dominant hand, presumably by means of changes in synaptic plasticity between neurons. Our previous studies also suggest that applying cathodal tDCS over the dominant motor cortex can improve performance for the non-dominant hand; this effect may result from modulating inhibitory projections (interhemispheric inhibition) between the motor cortices of the two hemispheres. We hypothesized that stimultaneously applying cathodal tDCS over the dominant motor cortex and anodal tDCS over the non-dominant motor cortex would have a greater effect on finger sequence performance for the non-dominant hand, compared to stimulating only the non-dominant motor cortex. Sixteen right-handed participants underwent three stimulation conditions: 1) dual-hemisphere – with anodal tDCS over the non-dominant motor cortex, and cathodal tDCS over the dominant motor cortex, 2) uni-hemisphere – with anodal tDCS over the non-dominant motor cortex, and 3) sham tDCS. Participants performed a finger-sequencing task with the non-dominant hand before and after each stimulation. The dependent variable was the percentage of change in performance, comparing pre- and post-tDCS scores.