基于对称重复纹理的摄像机位姿测量方法

某些目标上具有对称重复的纹理,这些纹理的图像矩阵具有低秩特性。当摄像机在偏离对正方向拍摄纹理时,由于存在投影形变,该纹理图像在原有方向上的对称性和重复性不再保留,从而不再具备低秩特性。通过建立摄像机拍摄方向与纹理图像的秩之间的数学模型,将摄像机方向的求解问题等效为一定约束下纹理图像的秩最小化问题。求解该问题,可得到摄像机拍摄方向,进一步结合纹理上任意两点的成像关系求解摄像机的空间位置。该方法与传统的基于目标图像中点、线等局部特征的测量方法相比,具有更高的准确性和良好的抗噪性能。仿真实验和实际实验均证明了该方法的有效性。     

基于机器视觉的汽车轮胎磨损检测系统设计CSCD

针对当前采用人工检测方法普遍存在效率低、容易出现误判、检测不方便等问题,提出一种基于机器视觉与图像处理相结合的轮胎纹理深度检测方法,设计了相应的检测系统。通过工业相机和激光器相配合获取汽车轮胎纹理图像,利用图像处理和误差补偿对图像进行处理获取轮胎纹理深度数据。通过实验验证了所提出的方法的可行性,为行驶中检测打下基础。     

基于双目视觉的工程车辆定位与行驶速度检测

针对工程车辆行驶速度低、滑转率高的特点,提出了一种基于双目序列图像的检测方法,以便快速检测工程车辆的相对位置与实际行驶速度。将双目摄像机安装在车辆上,连续采集周围环境的序列图像;利用SURF(speeded up robust features)特征对已采集到的各帧双目图像进行立体匹配,计算出环境特征点到摄像机坐标系原点的距离,从而实现车辆的相对定位;再对相邻两帧图像进行特征跟踪匹配,根据不同景深将匹配特征点对划分为远距点对和近距点对,分别利用远距点对和近距点对估算车辆运动过程中坐标系的旋转矩阵和平移矢量,并利用Levenberg-Marquardt法进行优化求解;最后根据优化后的旋转矩阵和平移矢量计算出车辆的行驶速度。户外模拟试验结果表明了方法的有效性和可行性。     

基于机器视觉的汽车轮胎磨损检测系统设计

针对当前采用人工检测方法普遍存在效率低、容易出现误判、检测不方便等问题,提出一种基于机器视觉与图像处理相结合的轮胎纹理深度检测方法,设计了相应的检测系统。通过工业相机和激光器相配合获取汽车轮胎纹理图像,利用图像处理和误差补偿对图像进行处理获取轮胎纹理深度数据。通过实验验证了所提出的方法的可行性,为行驶中检测打下基础。     

安瓿智能视觉检测机器人研究

针对医药安瓿中出现的可见异物,设计了一种医药安瓿智能视觉检测机器人。介绍了该系统的系统结构、视觉成像原理、电气控制系统和检测算法等内容。该系统通过运用机械装置使安瓿与背景之间产生运动差异,利用高速摄像机获取安瓿的序列图像,在软件中采用二次差分和能量累积的方法提取图像中的运动目标。还分析了不同系统机构的优劣和该机器所选择的系统结构。实验证明所研制的医药安瓿智能机器视觉检测机器人可以应用于实际在线检测。     

重轨视觉检测系统的摄像机成像角度优化

在机器视觉系统中摄像机的成像位姿很大程度上影响着图像质量。结合重轨的结构特点和表面缺陷分布位置,采用六摄像机环绕布置方案,通过提出不同的优化策略对摄像机成像角度进行优化,并研究图像清晰度评价函数建立重轨表面图像综合评价方法,分别从图像灰度均值、灰度方差、图像熵和灰度直方图、几何特征等方面对摄像机成像角度优化的结果进行评价,求得各摄像机的最佳成像角度,为重轨表面缺陷视觉检测系统搭建提供理论基础。     

克服阴影和车道线影响的路面坑洞识别研究

坑洞是非常严重的路面损坏,实现对路面坑洞的自动识别,对于自动驾驶车辆的安全性有重要意义。为解决现有路面坑洞识别方法易受阴影、车道线影响的问题,提出了一种可克服阴影和车道线影响的路面坑洞识别方法。该方法采用纹理和灰度信息相融合的灰度补偿算法去除图像中的阴影、车道线后,根据纹理特性利用小波变换对图像进行分解与融合,得到路面缺陷区域,然后利用积分投影得到路面缺陷区域的形状特征,再经支持向量机分类,得到含有坑洞的路面图像。实验结果表明,在有阴影、车道线影响的情况下,方法坑洞识别准确率更高。     

显微成像系统的多参数自适应优化技术

在基于显微磨粒图像处理的磨损故障诊断系统中,图像质量是保证磨粒分析的关键。而磨粒显微图像的成像质量与摄像机参数、光源参数有非常大的关系。采用遗传算法,对摄像机参数和光源参数进行了6个参数自动优化,利用标准图像与某参数下的图像差异构造了适应度函数,通过实数编码、赌轮选择、算术交叉和均匀变异等遗传算法操作,最终得到了一组最优的摄像机和光源参数。在该组参数下,磨粒图像与标准图像达到了最佳的逼近。最后,通过实验验证了该方法的正确有效性。     

三次透视投影变换图像拼接

为了减少带有路面信息的建筑物图像的拼接中产生的图像失真并提高拼接速度,基于局部变形方法并结合建筑物和路面纹理信息的不同提出了三次投影变换图像拼接方法。该方法根据图像内容将图像分割成不同子图像,然后拼接图像内容相同的子图像,最后实施总体拼接。为了改善当前全局投影变换带来的图像形状失真或扭曲问题,整个拼接过程采用三次局部的透视投影图像变换方法。由于是在传统的透视投影变换的基础上基于图像内容分割后再拼接,故拼接结果比传统方法更精确、更真实。实验结果表明:采用提出的图像拼接方法克服了路面部分纹理信息过少导致图像失真的缺陷,拼接速度比相关拼接方法提高了20%~40%。该方法能快速得到清晰无缝的拼接图像,基本满足拼接速度快、真实度高的要求。     

履带式车辆特殊路面反应谱测试

工程机械及履带式车辆所行驶的路面多数为非人工路面,基于公路路面的路面谱测量方法不再适用,因此描述与分析了履带车辆通过碎石路面的特点及采用直接在第一轮轴上安装加速度传感器进行测试的方法.并在理论上分析对采集的加速度信号进行处理的原理方法,以功率谱密度作桥梁,把实测路面对车辆的加速度激励信号转化为时间域上的反应谱,再通过车速信号,获得特殊路面的空间谱并计算给出谱的有关特征值.最后,对获得的谱与国家标准路面谱进行了对比.     

模糊PID控制的汽车牵引力系统仿真研究

汽车在低附着系数路面加速、起步或爬坡时,驱动轮极易发生过度滑转从而使汽车失去稳定性,汽车牵引力控制系统将驱动轮的滑转率控制在最佳的范围。建立了四轮驱动汽车的动力学模型,以驱动轮的滑转率为控制目标,采用基于模糊PID控制的汽车牵引力控制的算法,设计了以制动阀占空比为控制对象,从而达到调节轮缸制动压力的目的,在MatLab／Simulink仿真环境下,对车辆在均一和分离两种路面上进行了仿真,对比仿真结果,表明模糊PID控制具有响应速度快、稳态性能好的特点。     

Solid mechanics-based Eulerian model of friction stir welding

A new Eulerian model is established based on solid mechanics. With comparisons to the experimental data and the ALE model, the current model is validated. The power and the heat generations from pin side surface, pin tip surface, and shoulder contact surface in different rotating speeds are studied. Results indicate that the ratio of the heat input powers from the pin and the shoulder keeps constant in different rotating speeds. The velocity of the material flow around the welding tool and the slipping velocity are both increased with the increase of the rotating speed. The increase of the slipping velocity is the main reason for the increase of the heat input with the increase of the rotating speed. The torque from the shoulder contact surface is the major part of the total torque. The contribution to the total torque from the pin tip surface is the smallest.     

半环型锥盘滚轮式无级变速器的传动特性研究

分析了半环型锥盘滚轮式无级变速器基本结构、工作原理及在半接触角和摆动角变化时诸如传动比、滑动率、接触区的自转角速度、传动效率、滑滚比、牵引系数等牵引传动特性。研究表明，存在一个半接触角使得无级变速器在整个速比范围内，滑动率较小，自转角速度的绝对值较小，传动效率也较高，滑滚比较小，牵引系数较大，牵引力较小。随着动力滚子半接触角的增大，接触区的压力随着摆动角的增大而减小，传动比会减小，速比范围也有所减小。     

汽车牵引式无级变速器的传动特性研究

在分析了牵引式无级变速器基本结构和工作原理的基础上，着重分析了在半接触角和摆动角变化时诸如传动比、滑动率、接触区的自转角速度和传动效率等的传动特性。研究表明，存在一个半接触角使得无级变速器在整个速比范围内，滑动率较小，自转角速度的绝对值较小，传动效率也较高。随着动力滚子半接触角的增大，接触区的压力随着摆动角的增大而增大，传动比也会增大，但速比范围会有所减少。     

A theory of viscous hydroplaning

The traction developed in the contact area of a pneumatic tyre rolling and accelerating on a wet road surface is simulated by a block of rubber slipping on a two-dimensional sinusoidal surface covered with a thin water film. The resulting pressure-wedge formation on individual asperities of the surface provides a net uplift which tends to force tyre-tread and surface apart, thus promoting the onset of skidding or viscous hydroplaning. The important factor in minimizing skidding hazards is the provision of an adequate micro-roughness at asperity tips which contributes an adhesional mechanism to the overall friction coefficient. It is shown that in comparison with the adhesional contribution to friction, the contribution of hysteresis and viscous shear of the film are insignificant at low slip speeds.     

轮毂打磨5-DOF机械臂动力学建模与驱动参数预估

提出了一种基于2-UPS+UPU机构的5-DOF机械臂,建立了机械臂的手腕运动状态与其关节驱动参数之间的传递方程显式表达式,从而得到机械臂的伺服电机驱动参数峰值预估模型,计算出各伺服电机中的驱动转速最大理论值为25.1r/s,驱动力矩最大理论值为6.2N*m。以一组具体的结构参数作为算例,计算出伺服电机中的驱动转速最大值为18.7r/s,驱动力矩最大值为4.73N*m,算例伺服电机选型的预估功率为700W,证明了伺服电机峰值驱动参数预估模型的合理性。     

新型内窥镜机器人结构优化设计研究

研究了一种结构简单的新型内窥镜机器人驱动机构,并建立了内窥镜机器人在人体内腔中运动的数学模型.采用有限差分法分析了内窥镜机器人结构特性参数对机器人的最小粘液膜厚度和轴向摩擦牵引力的影响,从而获得当需要较厚的粘液膜厚度和较大的轴向摩擦驱动力时最优的机器人结构特性参数,为机器人更好地以较厚的粘液膜厚度和较快的速度悬浮式运行创造条件.内窥镜机器人的运行速度试验证明了此理论分析模型的正确性.     

Study of Boundary Slippage Using Movement of a Post-Impact EHL Dimple Under Conditions of Pure Sliding and Zero Entrainment Velocity

A well-recognized phenomenon of typical traction tests of elastohydrodynamic lubrication (EHL) contacts is finite maximum traction at increasing speeds, which led to the postulation that the limiting shear stress of liquid lubricants, a high-pressure rheological property, existed. If slippage occurs at the oil–solid boundary, the limiting traction measured is not necessarily an intrinsic property of the lubricant but rather a function of interfacial properties between the bounding solid surface and the lubricant. A recent report presented experimental evidence of boundary slippage at EHL contacts using a simple methodology based on differences in the speed of oil entrapment and the apparent entrainment. The reported experiments were carried out under pure sliding conditions. The phenomenon may also be explained by internal slippage in the bulk fluid film because of the limiting shear stress of the lubricant. To clarify this, similar experiments were repeated under zero entrainment velocity (ZEV) conditions. Evidence of the highly pressurized lubricant at the center of the oil entrapment sliding against the solid bounding surface was obtained. The purpose of this article is to discuss whether the slippage is attributed to the limiting shear stress of the oil or the critical shear stress of the oil/solid interfaces, and how to differentiate the magnitudes of the critical shear stress of the two bounding surfaces in a conventional optical EHL test rig.     

Clutch torque formulation and calibration for dry dual clutch transmissions

This paper focuses on the clutch torque formulation and calibration for dry dual clutch transmissions (DCT). The correlation on the theoretical clutch torque and control parameters is established based on constant friction power and clutch actuator kinematics. An algorithm based on powertrain dynamics is proposed for the calculation of clutch torque during vehicle launch and shift operations. This algorithm uses wheel speed sensor data as input and is capable of determining the clutch torque while both clutches are slipping, thus provides a reliable correlation between clutch torque during real time operations and clutch actuator control variables. The accuracy of the proposed algorithm has been validated by torque measurement in prototype testing on prove ground.     

Numerical simulation and experimental research on the wheel brush sampling process of an asteroid sampler

To examine the environmental characteristics of the microgravity force and the weathered layer on an asteroid surface, a symmetric wheel brush asteroid sampler is proposed for the collection of particles on the asteroid surface. To study the influence of the wheel brush rotation speed on the sampling efficiency and the driving torque required for the wheel brush, the contact dynamics model between particles and sampling wheel brushes is established and a simulation and experimental verification of the sampling process are conducted. The parameter calibration of the sampled particles is studied first, and the calibrated particle parameters are used in the numerical simulation of the sampling process. The sampling results and the particle stream curves are obtained for the working conditions of different rotation speeds, and the effects of different parameter settings on the sampling efficiency are analyzed. In addition, a set of rotating symmetrical sampling wheel brush devices is built for the ground test, and the dynamic torque sensor is used to test the torque change of the wheel brush during the sampling process. The relationship between the speed of the wheel brush and the driving torque of the wheel brush motor is determined by comparing the simulation results with the test results. Results indicate that when the rotating speed of the wheel brush is faster, the sampling efficiency is higher, and the driving torque required for the sampling wheel brush is greater. Moreover, a numerical simulation analysis of the sampling process of the wheel brush sampler in a microgravity environment is conducted to determine the optimal speed condition, and the brushing test of the wheel brush sampler in the microgravity environment is verified with the drop tower method. This research proposes the structural optimization design and motor selection of a wheel brush asteroid sampler, which provides important reference value and engineering significance.