一种简便的电磁超声测厚实现方法探究

针对电磁超声(EMAT)测厚中大功率脉冲电源和高灵敏度放大器等设计困难的问题,提出了使用压电超声仪来完成电磁超声测厚功能的方法。该方法仅需要设计电磁超声探头和转换电路模块。通过试验确定了检测探头的参数以及磁化方式,并研制了转换器,实现了一种简易有效的电磁超声测厚功能。实践证明,该方法应用效果良好,具有很好的推广价值。     

相邻金属孔间壁厚现场检测系统关键技术的研究

相邻金属孔间的壁厚测量以往都是根据镗床加工过程中的进刀量计算得出,精度较低.本文提出了一种应用电容传感器对两个金属孔间壁厚在线检测的系统.基于电容传感器,研究了电容测头的电场边缘效应的影响及保护环的宽度选择,设计了测量孔壁的电容测厚传感器进行差动测量.系统由两个距离确定的电容差动测厚传感器、测量电路、A/D接口及软件组成的.对壁厚2 mm,孔径3 mm的相邻金属孔壁厚的测量实验显示,误差达到0.3 μm.系统属于非接触测量,无需修正测头及工件变形误差.此系统测量精度高,测量速度快,操作方便,全套仪器便携,是解决相关壁厚现场精密检测问题的好方法.     

一种具有重力补偿的串联弹性执行器接触力控制方法

针对机械臂末端安装串联弹性执行器(Series Elastic Actuator,SEA)与环境或工件接触作业工况,考虑SEA端部负载对接触面压力随机械臂运动姿态变化的问题,研究一种具有重力补偿的SEA接触力控制方法。首先分析了一种基于滚珠丝杆模组的SEA与Staubli TX90 组合的力控制实验装置结构,建立了SEA与工件接触过程的动力学模型,提出了一种具有输入重力补偿的PD型SEA弹簧力控制方法,该方法在没有接触力传感器的情况下,依据机械臂关节角对SEA端部负载进行重力输入补偿,通过检测弹簧压缩变形量,计算并反馈弹簧力实现对接触力的控制。最后通过SEA与正弦面工件接触力控制实验,并对力传感器采集的接触力信号进行频谱分析,验证了所提出控制方法的有效性。     

辐射测厚仪测量精度分析与误差补偿技术

简单介绍了透射式辐射测厚原理,分析与研究了影响辐射测厚仪测量精度的各种因素.为了保证和提高测量精度,利用分段多项式曲线拟合与查表线性插值相结合的方法实现非线性补偿,利用软件查表法对测量气隙进行动态的温度补偿,利用内藏标样进行动态自动校正以实现综合误差补偿.实际应用表明,辐射测厚仪经过上述误差补偿后,测量范围广、测量精度高、性能稳定可靠、应用广泛.     

机器人传感器触觉心理量检测的研究

为了让机器人传感器具有触觉心理感知的能力,提出从接触力信息中提取被接触者触觉心理量的方法。该方法从人类触觉的心理物理学定律出发,在实验测量基础上拟合出人体皮肤触觉心理量与外部刺激之间的数学关系,将其应用到机器人传感器中实现了对接触者的触觉心理量的检测。实验证明:这种方法具有信号处理简单、误差小等优点。     

飞行机械臂系统的接触力控制

针对飞行机械臂系统的接触力控制问题,本文首先从理论上证明了闭环无人机系统具有与弹簧-质量-阻尼系统一致的动态特性.基于飞行机械臂接触状态下力的分析,得到了无人机水平前向接触力与系统重力和俯仰角之间的动态关系,进而分析出接触力控制可以不使用力传感器来实现.根据阻抗控制思想,提出了飞行机械臂系统接触力控制方法,即通过同时控制位置偏差和对应姿态角度来实现接触力的控制.给出了单自由度飞行机械臂系统动力学模型,对应分析出系统的稳定性.开发了基于四旋翼飞行器的单自由度飞行机械臂系统,并进行了实际的飞行实验,验证了所提出接触力控制方法的有效性,同时也证实了所开发系统的可靠性.     

扫描仪误差分析

为了解决用扫描仪测量微生物抑菌圈直径时误差较大问题,对扫描仪误差进行了分析。扫描仪误差包括像素间距误差、像素间距横纵比误差及扫描起点误差等。提出用椭圆拟合法对扫描仪误差进行测量。通过V isual C++6.0编程,研究了扫描仪误差与扫描时间、扫描位置、扫描分辨力等因素的关系,发现了一些规律,为编程实现针对扫描条件的测量结果自动修正打下了基础。     

基于力/力矩信息的面向位控机器人的阻抗控制

为了克服末端接触点距离力传感器中心较远时,力传感器测量实际接触力的局限性,分析实际作用力与测量力/力矩值之间的关系,利用力传感器信息或力矩信息得到位置控制方向和力控制方向.根据位控与力控方向对机器人末端进行参考轨迹规划,在阻抗控制律中应用参考比例因子调节参考轨迹.基于力误差信息通过模糊推理调节参考比例因子的大小,使生成的参考轨迹适应未知表面的变化.实验结果表明,所提出的控制方法能实现未知工件表面的恒力跟踪.     

扫描仪位置误差自动修正方法

在使用扫描仪测量微生物抑菌圈直径的过程中,受扫描仪工作原理的影响,存在着较大的系统误差。讨论了如何对扫描仪测量结果进行自动修正。通过Visual C++6.0编程,利用TWAIN标准,自动确定出随意摆放的被扫描物体在扫描仪工作平面上的位置。利用已知大小的物体,预先确定出各处的修正系数。实际测量时,可根据被测物体的位置,对结果进行自动修正,有效地减小位置误差的影响。实验获得了很高的测量精度,最大误差为0.18%。     

基于MEMS传感器的姿态测量系统设计

为解决单目三维扫描装置摄像机标定完成后姿态不能改变的问题,针对单目三维扫描装置使用过程中的运动方式与特点,设计了一款基于MEMS传感器的姿态测量系统;采用四元数对姿态进行解算,通过三轴姿态确定(TRAID)算法构建量测模型,以无迹卡尔曼滤波(UKF)算法进行数据融合,能有效抑制姿态解算过程中陀螺仪的漂移问题;实验结果表明,利用该系统进行姿态测量时静态误差低于±0.2°,动态误差低于±1°,系统实时性好、适用于动态三维扫描系统。     

基于电-声联合的液膜厚度测量方法研究

为了拓宽液膜厚度的测量范围,提出了一种联合应用电阻法与超声渡越时间法的液膜厚度测量新方法。设计了新型的电-声复合传感器,建立了用于优化传感器电极结构参数的数值模型,以灵敏度和线性度为优化目标确定了最优电极参数,通过开展液膜厚度测量实验验证了联合测量方法的有效性。研究结果表明：同轴金属电极适合于测量较薄液膜,在2.4mm~4.4mm厚度范围内的相对误差为-4.93%至5.35%;超声探头更适用于测量较厚液膜,在3.4mm~10.0mm厚度范围内的相对误差为-3.68%至2.20%。通过联合应用电阻法和超声法可以拓展两种方法各自的测量范围并且提高测量结果的可靠性。所提出的电学-声学联合测量方法具有测量范围宽、非侵入、响应快、精度和灵敏度高、安全性好等优点,能够广泛适用于工业生产和实验室研究等场合。     

Precise and smooth contact force control for a hybrid mobile robot used in polishing

Contact force is dominant in robotic polishing since it directly determines the material removal. However, due to the position and stiffness disturbance of mobile robotic polishing and the nonlinear contact process between the robot and workpiece, how to realize precise and smooth contact force control of the hybrid mobile polishing robot remains challenging. To solve this problem, the force tracking error is investigated, which indicates that the force overshoot mainly comes from the input step signal and the environmental disturbance causes force tracking error in stable state. Accordingly, an integrated contact force control method is proposed, which combines feedforward of the desired force and adaptive variable impedance control. The nonlinear tracking differentiator is used to smooth the input step signal of the desired force for force overshoot reduction. Through modeling of the force tracking error, the adaptive law of the damping parameter is established to compensate disturbance. After theoretical analysis and simulation verification, the polishing experiment is carried out. The improvement in force control accuracy and roughness of the polished surface proves the effectiveness of the proposed method. Sequentially, the proposed method is employed in the polishing of a 76-meter wind turbine blade. The measurement result indicates that the surface roughness after mobile robotic polishing is better than Ra1.6. The study provides a feasible approach to improve the polishing performance of the hybrid mobile polishing robot.     

捷联惯导大方位失准角快速初始对准

捷联惯导方位角快速性能优化问题,传统大方位失准角初始对准方位角收敛速度较慢,直接影响惯导系统的性能。为此提出一种无重置联邦滤波器的以速度误差和比力输出作为观测量的快速初始对准新算法。给出了捷联惯导系统非线性误差模型,并分析了两种观测量,建立了速度观测子滤波器和比力观测子滤波器,同时采用了相应的状态方程和观测方程。用三种方法进行了大方位失准角初始对准的数字仿真。仿真结果对比表明,新方法不仅使方位失准角收敛速度快,而且在加速度计噪声增大10倍的情况下,仍然具有极高的对准精度。     

Contact Stiffness Identification with Delay and Structural Compensation for Hardware-in-the-Loop Contact Simulator

The hardware-in-the-loop (HIL) simulation is necessary to test the contact dynamics of spacecraft in space. The stiffness parameter is important for the state recording and compliant control. A contact stiffness estimation method is proposed, where the force measurement delay and structural dynamics of the upper platform are compensated to guarantee the estimation accuracy. The force measurement delay and structural deformation of the upper platform lead to the delayed force signal and the position error respectively, and then the contact stiffness identification error. A phase lead based delay compensation is used to reconstruct the true contact force from the measured force. The structural deformation of the upper platform is compensated by a structural dynamics model to obtain the true contact position. Based on the compensated force and position signals, the stiffness identification is performed using the real time recursive least squares (RLS) method. The effectiveness of the proposed method is verified by simulations and experiments. In the experiments, the stiffness identification error is about ± 5 %, which is satisfactory for monitoring and control applications.     

MEMS制造中精确测量薄膜厚度的方法研究与比较

精确测量各种功能薄膜的厚度在微机电系统（ MEMS）制造加工过程中有非常重要的意义。利用接触式表面轮廓仪、光谱椭偏仪、电感测微仪、扫描电镜、原子力显微镜和工具显微镜分别测量了10 nm～100μm各种薄膜的厚度。比较了不同测量仪器的测量范围、分辨率和对样品的适用性,分析了薄膜厚度测量过程中误差产生的机理。实验结果表明：当存在膜层台阶时,10 nm～100μm的膜厚测量均可采用接触式表面轮廓仪,对于硬度较高的膜层可采用电感测微仪,对于厚度小于0.5μm的膜层可采用原子力显微镜;对于可观察样品侧面、厚度大于0.7μm的膜层可采用扫描电镜,工具显微镜适用于μm级膜层,对于厚度大于20μm的膜层不宜采用光谱椭偏仪。     

基于压电主动传感方式的螺栓松动检测实验研究*

针对螺栓联接结构中螺栓易松动而引发事故的情况,进行了压电主动传感方式的螺栓松动检测研究。采用压电材料激发超声波,根据透射波通过螺栓联接界面时,透射波携带的能量与界面间实际接触面积相关,而界面实际接触面积与界面压力(即螺栓作用力)成一定关系,通过测量透射波的能量确定螺栓的松紧程度。建立了实验装置,进行了实验研究。实验结果显示,作为传感器的压电材料所接收到的超声波能量与螺栓紧固力具有较好相关性,该方法可作为螺栓联接结构健康监测的一种新方法。     

基于GA-BP算法的超声波测量精度优化研究

针对复杂环境下超声波传感器测量系统测量精度问题,以罐体油位测量为例,提出一种基于神经网络遗传算法的超声波传感器测量精度优化模型,实现超声波油位测量系统的非线性误差校正。仿真结果表明,该方法可以减小超声波传感器本身结构和外界因素的干扰,提高测量精度。     

Neural Network Force Control for Industrial Robots

In this paper, we present a hierarchical force control framework consisting of a high level control system based on neural network and the existing motion control system of a manipulator in the low level. Inputs of the neural network are the contact force error and estimated stiffness of the contacted environment. The output of the neural network is the position command for the position controller of industrial robots. A MITSUBISHI MELFA RV-M1 industrial robot equipped with a BL Force/Torque sensor is utilized for implementing the hierarchical neural network force control system. Successful experiments for various contact motions are carried out. Additionally, the proposed neural network force controller together with the master/slave control method are used in dual-industrial robot systems. Successful experiments are carried out for the dual-robot system handling an object.     

Position-based force tracking adaptive impedance control strategy for robot grinding complex surfaces system

As a key technology of robot grinding, force control has great influence on grinding effects. Based on the traditional impedance control, a position-based force tracking adaptive impedance control strategy is proposed to improve the grinding quality of aeroengine complex curved parts, which considers the stiffness damping environmental interaction model, modifies the reference trajectory by a Lyapunov-based approach to realize the adaptive grinding process. In addition, forgotten Kalman filter based on six-dimensional force sensor is used to denoise the force information and a three-step gravity compensation process including static base value calculation, dynamic zero update and contact force real-time calculation is proposed to obtain the accurate contact force between tool and workpiece in this method. Then, to verify the effectiveness of the proposed method, a simulation experiment which including five different working conditions is conducted in MATLAB, and the experiment studying the deviation between the reference trajectory and the actual position is carried out on the robot grinding system. The results indicate that the position-based force tracking adaptive impedance control strategy can quickly respond to the changes of environmental position, reduce the fluctuation range of contact force in time by modifying the reference trajectory, compensate for the defect of the steady-state error of the traditional impedance control strategy and improve the surface consistency of machined parts.