两相混合式步进电机细分驱动器研制

讨论了步进电机的细分驱动原理以及数字PI控制策略。介绍了一种基于数字信号处理器(DSP)的两相混合式步进电机细分驱动器的软硬件结构,并给出了实际运行的电机相电流波形。通过采用电压补偿、电流负反馈以及数字PI调节,对步进电机相电流进行"阶梯化"正弦波控制,使步进电机相电流接近正弦波,改善了步进电机的运行工况。     

An event-driven simulation method for motor driver in virtual machine tool system

In this paper, an event-driven simulation method is proposed for the motor driver in a virtual machine tool system (VMT), of which simulation speed is always a puzzle. This method utilizes a set of pre-defined events to trigger the execution of simulator in a non-deterministic manner and at the most efficient moment. Comparing to the conventional time domain simulation method, it dramatically reduces the CPU time consumption without losing simulation accuracy, therefore it improves the simulation efficiency. The effectiveness of this method is verified through a PMSM (Permanent Magnet Synchronous Motor) motor driver model in studying Servo/Mechanical interaction within a VMT.     

高性能步进电动机细分驱动器的设计

本文设计了一种适合三相反应式步进电动机的高性能细分驱动器,在功率驱动中采用了大功率VMOS器件,在细分环形分配器设计中采用了两片GAL,使整个电路具有较高的运行性能,开关迅速,功耗小,体积较小,可靠性较高.     

针对机动车驾驶员的人脸检测方法

为了正确检测人脸区域、提高驾驶室内光照不足情况下人脸检测与定位方法的准确性和实时性,采用了肤色聚类的人脸检测方法,利用肤色聚类性将彩色图像分割成皮肤区和非皮肤区。同时,提出一种基于多尺度Retinex算法的改进算法,其能够在人脸检测之前对图像进行光照补偿处理。将改进后的算法应用到新建立的人脸图像库中进行仿真实验,并与传统的肤色聚类人脸检测方法进行对比,其正确率提高了4.7%。实验结果表明:改进后的肤色聚类人脸检测算法可实现对不同光照变化和旋转角度的人脸进行检测,且具有很强的实用价值。     

电压型变频器、三相交流异步电动机传动系统的稳定性

运用微分几何反馈控制方法,对电压型变频器、三相交流异步电机传动系统,在特殊的流形上,把这种多变量、非线性、强耦合的传动系统映射为两个独立的线性子系统;证明了系统的相对阶满足变换条件,提出了变换矩阵的构造性寻找方法;基于线性二阶系统Lyapunov函数,在此流形上,研究传动系统的稳定性函数,证明了这种函数的正定性以及其导数的定号性,最后对国产Y-系列15kW的电机进行研究,得出其稳定性判别函数,方法简单,而且稳定性区域大小满足工程实际需要.     

Modeling and performance analysis of a hybrid driver model

For an effective simulation of vehicle motion a realistic driver model is as necessary as the dynamic vehicle model. In this paper, the human perception process is described by discrete event techniques that also allow human deficiencies to be addressed. When a human driver reaches his personal physical limits, his control performance rapidly deteriorates.     

An integrated driver warning system for driver and pedestrian safety

A semi-integrated system for driver assistance and pedestrian safety is presented. This system is composed of a single camera which focuses on the driver for picking up visual cues and a stereo rig that focus on the road ahead for the detection of road obstructions and pedestrians. While the car is in motion, the driver's viewing direction is obtained and analyzed along with information of road condition and any moving vehicle ahead in order to determine if the current driving condition is safe. In addition, when the vehicle is moving slowly, the system can also detect the existence of a pedestrian ahead and warns the driver if the pedestrian moves in front of the car. This system contains algorithm-based safety analysis as well as fuzzy rules-based analysis for interaction between variables. Our experimental results show that the condition for driver safety can be accurately classified in 94.5% of the tested driving conditions, and the pedestrians can be identified in 93.18% of the tested cases. These were compared to the results of similar systems and shown to be superior.     

Realization of an adaptive voltage driver for voice coil motor

In this paper we describe a head servo-positioning system for hard disk drives (HDDs), in which the usual current command for the voice coil motor has been replaced by a simpler voltage command. This solution has proven advantages in terms of cost, since the voltage driver does not require any resistive shunt for current measurement and phase-shaping passive networks for the current controller. Also, it requires a lower pin count and can be easily implemented with a PWM power stage. The voltage driver consists of a voltage-controlled power stage, with a pre-filter placed at its input, plus a back e.m.f. feed-forward compensator. The role of the pre-filter is to provide a transfer function between input signal and VCM current as close as possible to that of a standard current loop, so providing a one-to-one replacement to standard current drivers. To achieve this, it can be shown that the filter must cancel out the low-frequency pole of the VCM, located in a position which depends on the electrical impedance of the VCM itself. This, however, may change by ±30% during HDD operations, due to self-heating and consequent variation of the VCM resistance. Such variation may lead to an unsatisfactory performance of the voltage driver, so an adaptation mechanism, capable of tracking variations of VCM coil resistance, must be set up. This paper presents an on-line estimation procedure, based on an extended Kalman filter (EKF), capable of estimating the VCM coil resistance with a high degree of accuracy. EKF, however, usually brings a high computational load, making it unsuitable for real-time, low-cost embedded applications. The paper presents two reduced-order model of the VCM, for which the EKF can be implemented with 30 and 50% less computational effort, respectively, while maintaining a good estimate of the VCM coil resistance. The paper reports experimental results of VCM resistance estimation, obtained with the proposed algorithm, running in 30 μS on a 25 MHz, fixed-point DSP. Also, the on-line estimation is used to adapt the pre-filter. Experimental results show that the servo performance with adaptive voltage driver is not affected by resistance variation and equivalent to that of the standard current driver.     

基于嵌入式Linux的步进电机驱动程序设计

介绍了Linux驱动程序的实现机制,在分析步进电机和驱动程序接口的基础上,给出了一个在嵌入式Linux平台上编写步进电机驱动的实例.本平台基于Samsung公司的S3C2410X CPU,采用Linux2.4内核作为它的操作系统.介绍了如何通过对驱动程序的操作实现对步进电机的控制.在JXARM2410实验平台上的实验结果表明驱动运行正常.     

Neural information processing with feedback modulations

Descending feedback connections, together with ascending feedforward ones, are the indispensable parts of the sensory pathways in the central nervous system. This study investigates the potential roles of feedback interactions in neural information processing. We consider a two-layer continuous attractor neural network (CANN), in which neurons in the first layer receive feedback inputs from those in the second one. By utilizing the intrinsic property of a CANN, we use a projection method to reduce the dimensionality of the network dynamics significantly. The simplified dynamics allows us to elucidate the effects of feedback modulation analytically. We find that positive feedback enhances the stability of the network state, leading to an improved population decoding performance, whereas negative feedback increases the mobility of the network state, inducing spontaneously moving bumps. For strong, negative feedback interaction, the network response to a moving stimulus can lead the actual stimulus position, achieving an anticipative behavior. The biological implications of these findings are discussed. The simulation results agree well with our theoretical analysis.     

Linear strain maximization in MEMS-elastomer hybrid configurations for isotropic electromagnetic modulations in stretchable electronics

We analyzed several model designs that have been subjected to incremental increase in the isotropically distributed strain for an elastomer component which is integrated into a four-actuator microelectromechanical system (MEMS) with a hybrid configuration in this study. Based on the fundamental configuration in which a cross-shaped polydimethylsiloxane (PDMS) structure was placed above the symmetrically designed MEMS with a limited 40.96% degree of isotropy (DOI), our analysis showed that retreating the location of the applied forces away from the center induced free-form PDMS deformation and increased the DOI by 36.48%. Continuous expansion of the DOI was realized by either connecting the geometrically dicontinuous PDMS (for an additional 7.20% improvement) or removing constraints from its right-angled shape (for an additional 7.52% improvement). Further analysis showed that an integrated configuration based on an eight-actuator MEMS exhibited a 100% DOI in the active area, which can be applied to support various electromagnetic modulations that require linear and isotropic strain operations as stretchable electronics. In addition to mechanical analyses, color filtering based on surface plasmon resonance was performed to evaluate potential improvements in terms of the positive relationship between the DOI and color purity. An example of further enhancement of the strain by increasing the forces applied to the MEMS is provided, which proves that a doubled linear and isotropic strain could be induced in the hybrid configuration compared to that generated by the existing configuration.     

Optimal closed-loop control of a hybrid step motor with chopper drive

Optimal closed-loop control of a hybrid step motor control with chopper drive is described. Expressions for the average torque and optimal control angle giving maximal average torque in the stationary state without phase current chopper control are presented. The effects of chopper current control on the torque and acceleration characteristics of a hybrid step motor are discussed. Expression have been developed for the control angle in the chopper current control mode, yielding greater torques and improved acceleration of hybrid step motors than for the optimal control angle without phase current control. The speed response of a hybrid step motor operated in a closed-loop system has been studied by computer simulation for different supply voltages and torque loads, using various control angle algorithms.     

An investigation of train driver visual strategies

Train driving is primarily a visual task; train drivers are required to monitor the dynamic scene visually both outside and inside the train cab. Poor performance on this visual task may lead to errors, such as signals passed at danger. It is therefore important to understand the visual strategies that train drivers employ when monitoring and searching the visual scene for key items, such as signals. Prior to this investigation, a pilot study had already been carried out using an eye tracking technique to investigate train drivers’ visual behaviour and to collect data on driver monitoring of the visual environment, Groeger et al. (2003) Pilot study of train drivers’ eye movements, University of Surrey. However, a larger set of data was needed in order to understand more fully train driver visual behaviour and strategies. In light of this need, the Transport Research Laboratory produced a methodology for the assessment of UK train driver visual strategies, on behalf of the Rail Safety and Standards Board and applied this methodology to conduct a large-scale trial. The study collected a wealth of data on train drivers’ visual behaviour with the aim of providing a greater understanding of the strategies adopted. The corneal dark-eye tracking system chosen for these trials tracks human visual search and scanning patterns, and was fitted to 86 drivers whilst driving in-service trains. Data collected include the duration and frequency of glances made towards different elements of the visual scene. In addition, the train drivers were interviewed after driving the routes, to try and understand the thought processes behind the behaviour observed. Statistical analysis of over 600 signal approaches was conducted. This analysis revealed that signal aspect, preceding signal aspect, signal type and signal complexity are important factors, which affect the visual behaviour of train drivers. Train driver interview data revealed that driver expectation also plays a significant role in train driving. The findings of this study have implications for the rail industry in terms of infrastructure design, design of the driving task and driver training. However, train driving is extremely complex and the data from this study only begin to describe and explain train driver visual strategies in the specific context of signal approaches. This study has provided a wealth of data and further analysis of it is needed to investigate the role of other factors and the complex relationships between factors during signal approaches and other driving situations systematically. Finally, there are important aspects of visual behaviour that cannot be examined using these data or this method. Investigation of other aspects of visual behaviour, such as peripheral vision, will require other methods such as simulation.     

Perturbation wavelet neural sliding mode position control for a voice coil motor driver

To cope with the nonlinear electro-magneto-mechanical characteristics, this paper proposes a perturbation wavelet neural sliding mode position control (PWSPC) system for a voice coil motor (VCM) driver. A perturbed wavelet neural network (PWNN) approximator is used to online approximate the unknown nonlinear term in the VCM system dynamics. The PWNN approximator uses perturbed wavelet functions to handle the rules uncertainties like interval type-2 fuzzy sets. The structure learning ability enables the PWNN approximator to evolve its structure online. Further, the parameter learning laws and stability analysis are derived in the sense of Lyapunov function; thus, the parameter convergence and system stability can be guaranteed. Finally, the experimental results verify that the proposed PWSPC system can achieve favorable control performance such as good disturbance rejection and good tracking accuracy.

     

An intelligent driver location system for smart parking

It is often frustrating for drivers to find parking spaces, and parking itself is costly in almost every major city in the world. Here we propose a crowdsourcing solution by exploiting sensors in smart-phones to collect real-time parking availability information. We design a phone-based system to track a driver’s trajectory to detect when they are about to leave their parking spot. We focus on the efficiency and accuracy of using a phone to monitor the driver’s walking trajectory, applying a waist-mounted PDR method that can measure the driver’s moving distance with a high accuracy. In addition, we design a map matching algorithm to calibrate the direction errors when the driver is in an indoor environment, using widely-available building floor plans. The results of our experiment show that we can achieve about 98% accuracy in estimating the user’s walking distance, with an overall location error of about 0.48 m.     

Vehicle and driver attributes affecting distance from the steering wheel in motor vehicles

The current study was designed to confirm that female drivers sit closer to the steering wheel than do male drivers and to investigate whether this expected difference in sitting position is attributable to differences in the physical dimensions of men and women. Driver body dimensions and multiple measures of sitting distance from the steering wheel were collected from a sample of 150 men and 150 women. The results confirmed that on average, women sit closer to the steering wheel than men do and that this difference is accounted for by variations in body dimensions, especially height. This result suggests that driver height may provide a good surrogate for sitting distance from the steering wheel when investigating the role of driver position in real-world crash outcomes. The potential applications of this research include change to vehicle design that allows independent adjustment of the relative distance among the driver's seat, the steering wheel, and the floor pedals.     

An autonomous vehicle for people with motor disabilities

The authors describe the creation of the VAHM prototype, including the hardware and software functionalities and other aspects of this “smart” wheelchair     

Multiplexed LCD with integrated driver

The problems of multiplexing liquid crystal displays are outlined, and an integrated driver is described.     

An improved hybrid classifier

Abstract. A new hybrid classifier is proposed which utilizes the advantages of the maximum likelihood classifier and the parallelepiped classifier. The new hybrid classifier reduces the processing time more substantially than the conventional one by introducing a lower boundary for each class. The rate of misclassification is comparable to that of maximum likelihood classifier. Performance of the conventional and the new method are compared by an example.