Development and Calibration of a Hyperstatic Six-component Force/Torque Sensor

The six-component force/torque sensor has become one kind of the most important sensors with the ability of measuring all the external forces and torques. A novel hyperstatic six-component force/torque sensor based on the Stewart platform structure, which can be used for the force measurement of the robot wrist, is proposed, and its structural optimal design, finite element analysis and calibration experimentation is presented. The characteristic of the sensor structure is analyzed in comparison with the traditional Stewart platform-based sensor. The mathematical expression of the sensor＇s force mapping matrix is introduced. The condition number and generalized amplifying coefficient defined by singular values of force Jacobian matrix are used to evaluate the performances of isotropy and sensitivity of the sensor respectively. The optimal design of the sensor structure is performed with the objective of achieving high measurement sensitivity and good isotropy. The sensor prototype is fabricated, and the static and dynamic characteristics of the sensor are analyzed with finite element analysis software package ANSYS. The calibration device is manufactured, and the data acquisition and processing system is developed. The theoretical and experimental study of the static calibration of the sensor prototype is carried out. The results of simulation analysis and calibration experimentation prove the feasibility of the hyperstatic sensor structure, and the contents of this paper possess theoretical significance and engineering value for the further research and practical application of the six-component force sensor.

Miniature 6-axis force/torque sensor for force feedback in robot-assisted minimally invasive surgery

In order to restore force sensation to robot-assisted minimally invasive surgery(RMIS),design and performance evaluation of a miniature 6-axis force/torque sensor for force feedback is presented.Based on the resistive sensing method,a flexural-hinged Stewart platform is designed as the flexible structure,and a straightforward optimization method considering the force and sensitivity isotropy of the sensor is proposed to determine geometric parameters which are best suited for the given external loads.The accuracy of this method is preliminarily discussed by finite element methods(FEMs).The sensor prototype is fabricated with the development of the electronic system.Calibration and dynamic loading tests for this sensor prototype are carried out.The working ranges of this sensor prototype are 30 N and 300 N·mm,and resolutions are 0.08 N in radial directions,0.25 N in axial direction,and 2.4 N·mm in rotational directions.It also exhibits a good capability for a typical dynamic force sensing at a frequency close to the normal heart rate of an adult.The sensor is compatible with surgical instruments for force feedback in RMIS.

Torque Sharing Function Control of Switched Reluctance Machines with Reduced Current Sensors

This paper presents a Torque Sharing Function(TSF)control of Switched Reluctance Machines(SRMs)with different current sensor placements to reconstruct the phase currents.TSF requires precise phase current information to ensure accurate torque control.Two proposed methods with different chopping transistors or a new PWM implementation require four or two current sensors to replace the current sensors on each phase regardless of the phase number.For both approaches,the actual phase current can be easily extracted during the single phase conducting region.However,how to separate the incoming and outgoing phase current values during the commutation region is the difficult issue to deal with.In order to derive these two adjacent currents,the explanations and comparisons of two proposed methods are described.Their effectiveness is verified by experimental results on a four-phase 8/6 SRM.Finally,the approach with a new PWM implementation is selected,which requires only two current sensors for reducing the number of sensors.The control system can be more compact and cheaper.

A novel speed sensor-less direct torque control system for mining locomotive haulage

A novel speed sensor-less direct torque control induction motor drive system for the mining locomotive haulage is presented in the paper. Rotor speed identification is based on the model reference adaptive control theory with neural network using back propagation algorithm. The system is implemented using a real-time TMS320F240 digital signal processor. The simulation study and experiment results indicate that the suggested system has good performance.

Design and calibration of spoke piezoelectric six-dimensional force/torque sensor for space manipulator

The large manipulator outside the space cabin is a multi-degree of freedom actuator for space operations.In order to realize the automatic control and flexible operation of the space manipulator,a novel spoke structure piezoelectric six-dimensional force/torque sensor with redundancy ability,high stiffness and good decoupling performance is innovatively proposed.Based on the deformation coordination relationship,the redundancy measurement mechanism is revealed.The mathematical models of the sensor with and without branch fault are established respectively.The finite element model is established to verify the feasibility of structure and redundancy measuring principle of the sensor.Depending on the theoretical analysis and simulation analysis,the prototype of the sensor is developed.Static and dynamic calibration experiments are carried out.The actual output voltage signal of the six-dimensional force/torque sensor is collected to establish the equation between the standard input applied load and the actual output voltage signal.Based on ant colony optimized BP algorithm,performance indexes of the sensor with and without branch fault are analyzed respectively.The experimental results show that the spoke piezoelectric sixdimensional force/torque sensor with the eight-point support structure has good accuracy and reliability.Meanwhile,it has strong decoupling characteristic that can effectively shield the coupling between dimensions.The nonlinear errors and maximum interference errors of decoupled data with and without branch faults are less than 1% and 2%,respectively.The natural frequency of the sixdimensional force sensor can reach 2856.45 Hz and has good dynamic characteristics.The research content lays a theoretical and experimental foundation for the design,development and application of the new six-dimensional force/torque sensors with redundancy.Meanwhile,it will significantly improve the research level in this field,and provide a strong guarantee for the smooth implementation of force feedback control of the space station manipulator project.

基于Modbus/TCP的电容式扭矩传感器数据采集系统设计

扭矩传感器通常安装于机械设备的旋转关节处,用于扭矩的测量。电容式扭矩传感器需要配备专门的数据采集系统才能使用,且数据采集系统的性能直接影响传感器的精确测量。针对实验室自主研制的电容式扭矩传感器的应用需求,设计了一种基于Modbus/TCP协议的数据采集系统。系统以STM32为主控芯片,通过控制电容数字转换芯片AD7147实现电容信号采集与转换,然后由W5500以太网芯片将数据上传到自主开发的上位机软件中进行处理、显示与存储。实验测试表明:系统最大测量误差为1.47%,数据输出频率为1000 Hz。

磁聚焦式扭矩传感器激励线圈控制策略研究

为测量旋转轴不同工况下的扭矩,提出了一种基于磁聚焦式扭矩传感器的激励线圈控制策略。该控制策略以控制传感器稳定输出幅值为2 mV电信号为目标,将感应电压数学模型和正交试验法相结合,对各个工况下的激励线圈控制策略进行设计,并利用MATLAB和COMSOL软件对各控制策略进行理论计算和有限元仿真验证。为模拟传感器在台架实验中得到的带噪声信号,对仿真得到的输出电信号添加高斯白噪声,利用MATLAB仿真软件对带噪声信号进行滤波优化。仿真结果表明:该控制策略能够使传感器在旋转轴的不同工况下,稳定输出幅值为2 mV的类正弦电压信号,验证了其可行性。

谐波减速器转矩原位测量及误差补偿

为实现协作机器人精准力控,利用谐波减速器柔轮变形研制了一种原位集成转矩传感器。提出了基于傅里叶级数模型的剩余纹波补偿方法提高测量精度。提出了基于傅里叶级数模型的剩余纹波补偿方法提高测量精度。首先,分析了柔轮底部应变规律,通过正弦叠加的原理设计了应变敏感栅结构;然后建立纹波与波发生器角度之间的傅里叶级数模型,补偿剩余纹波;最后,研制了测试平台进行加载测试,结果表明,在波发生器静止状态下施加瞬时激励和阶跃负载,自制转矩传感器与标准转矩传感器输出误差为0.988%和0.253%;在波发生器旋转状态下施加阶梯变化、正弦变化、正弦变化过程中人为碰撞三种形式的负载,自制转矩传感器与标准转矩传感器输出误差为3.822%,4.247%和4.456%。本文提出的补偿方法能有效降低剩余纹波对传感器输出的干扰,有利于推动关节转矩精准测量的实现。

汽车装配生产线电动伺服螺纹拧紧设备发展现状

中国汽车销量已经连续14年居世界第一,螺纹连接为汽车零部件之间的主要连接形式,螺纹拧紧设备市场需求巨大。目前国内汽车生产线上的拧紧设备主要依靠进口,造价高,已经成为卡脖子问题。为此文章针对汽车生产线的电动伺服螺纹拧紧设备的关键技术展开论述:对比了交流永磁伺服同步电机的控制策略;论述了拧紧设备的减速机构方案;对比了不同的扭矩检测方案;最后分析了国内外现有的电动伺服螺纹拧紧设备的特点。通过对电动伺服螺纹拧紧设备关键技术的研究分析,指出了现阶段电动伺服拧紧设备上不同技术方案的优缺点及发展趋势,为国内电动伺服螺纹拧紧设备的研究与开发提供了思路。

剪切梁结构扭矩传感器的应变解析

为实现对机器人在复杂情况下的灵活控制,需要在机器人关节处增加扭矩传感器,扭矩传感器是获取机器人关节运行状态的重要检测部件。考虑机器人自身尺寸限制及工作场景等因素,扭矩传感器采用轮辐式结构。本文介绍了扭矩传感器的结构和工作原理,分析了传感器弹性横梁在扭矩载荷作用下的变形协调条件,基于变形协调条件和铁木辛柯梁理论推导了剪切梁的应变计算公式,并建立了简化力学解析模型。通过有限元分析对力学模型的准确性和对弹性体结构参数的敏感性进行了验证。算例结果表明,该简化力学模型得出的结果和有限元结果数值相对误差在8.9%以内,表明了该简化力学解析模型的准确性。

磁场对脱手检测功能的影响与优化方法分析

阐述一种通过监控学习获取可信EPS零漂的方法,并将可信EPS零漂引入到脱手检测控制逻辑中。该方法有效地消除扭矩传感器零漂对脱手报警的影响,提高自动驾驶辅助系统脱手报警的准确率。

Inspection of Complex Internal Surface Shape with Fiber-optic Sensor II: for Specular Tilted Surface Measurement

Complex surface shape measurement has been a focus topic in the CAD/CAM field. A popular method for measuring dimensional information is using a 3D coordinate measuring machine (CMM)with a touch trigger probe. The measurement set up with CMM, however, is a time consuming task and the accuracy of the measurement deteriorates as the speed of measurement increase. Non-contact measurement is favored since high speed measurement can be achieved and problems with vibration and friction can be eliminated. Although much research has been conducted in non-contact measurement using image capturing and processing schemes, accuracy is poor and measurement is limited. Some optical technologies developed provide a good accuracy but the dynamic range and versatility is very limited. A novel fiber-optic sensor used for the inspection of complex internal contours is presented in this paper, which is able to measure a surface shape in a non-contact manner with high accuracy and high speed, and is compact and flexible to be incorporated into a CMM. Modulation functions for tilted surface shape measurement, based on the Gaussian distribution of the emitting beam from single-mode fiber (SMF), were derived for specular reflection. The feasibility of the proposed measurement principle was verified by simulations.

Research on Non-Contact Weak Current Detection Technology

With the continuous development of industrial technology, the weak current plays an increasingly important role in all fields of life. In order to facilitate the user to carry, the study of contactless weak current measurement technology is also emerging. This article’s design idea is based on two-dimensional reluctance sensor device built non-contact weak current detection system. The system uses the reluctance sensor HMC1002 to collect the current signal and the temperature sensor DS18B20 to compensate the temperature. The signals collected by the reluctance sensor and the temperature sensor are extremely weak. After being amplified by the amplifying circuit, the signal is conducive to subsequent detection and processing. Filter circuit can filter out interference signals to achieve the goal of improving accuracy. After the corresponding algorithm of the microcontroller will convert the signal voltage, easy to read and store, thus designing a non-contact current measurement capable of detecting weak currents and achieving higher accuracy.

电容式六维力与力矩传感器数据采集系统设计

为实现电容式六维力与力矩传感器测量力与力矩信息的实时采集和显示,针对实验室自主研制的电容式六维力与力矩传感器开发了一套数据采集系统。系统以STM32F103C8T6作为主控芯片,电容信号经AD7147采集并转换为数字信号,转换结果经隔离型SPI通讯传输到主控芯片后,主控芯片通过基于Modbus协议的RS485通讯发送给上位机。上位机采用WinForm界面进行设计,能对数据进行进一步标定计算处理,并最终实现所测量力与力矩值的实时显示与保存。经过实验测试,采集系统的测量值和实际加载的力与力矩值的测量误差低于3%。该系统的采样精度高、开发成本低且上位机功能完善,为电容式六维力与力矩传感器的应用研究提供了重要的信息。

带负载扰动补偿的永磁同步电机改进MRAS观测器控制

针对传统模型参考自适应系统(MRAS)对转速和负载变化敏感及鲁棒性差等问题,提出一种基于快速超螺旋滑模自适应观测器的改进型控制算法。利用快速超螺旋滑模代替传统的PI自适应环节,提高了系统鲁棒性;考虑负载转矩对系统产生的影响,将负载转矩和转速作为状态变量,选取转速实际值与观测值误差作为滑模面,设计负载转矩滑模观测器,将实时辨识的负载转矩引入到电流环,对参考转矩进行前馈补偿,提高了系统的抗负载扰动能力。以表贴式永磁同步电机为控制对象进行仿真和实验。结果表明:相比传统的模型参考自适应控制,改进型快速超螺旋滑模观测器控制具有更好的动态性能和鲁棒性。

双馈感应电机无速度传感器直接转矩控制方法

风电机组双馈感应发电机运行中,由于参数变化的不确定性导致其无速度传感器直接转矩控制输出值出现异常波动,为保证双馈感应电机的频率稳定性,提出一种双馈感应电机无速度传感器直接转矩控制方法。计算转子磁链同步转速和转差速度,得到发电机的转速观测值;分析转子绕组电压空间矢量,建立磁链模型并构建电磁矩阵,在矩阵中计算定子绕组和转子绕组的磁势矢量,通过二者的矢量积得到电机的电磁转矩;转速和转矩共同组成直接转矩控制系统,实现对电机的速度调节和控制。仿真分析结果表明:采用所提方法时,在双馈感应电机启动后转速迅速增加,且在1.2 s后转速始终保持为1400 r/min,可保证转子磁链的运行轨迹接近于圆形,直接转矩控制效果平稳。

半导体应变片式高灵敏度力矩传感器静态标定

半导体应变片式力矩传感器广泛应用于智能机器人、航空、机械装配与制造等多个领域。对实验室自主研制的半导体应变片式力矩传感器进行静态标定实验,在刚度分析的基础上确定了传感器静态性能参数指标,验证了高灵敏度力矩传感器结构设计的合理性与使用的可靠性。

关节力矩反馈型协作机器人的阻抗控制研究

针对机器人和环境接触的作业任务,一般方法是利用六维力矩传感器实现阻抗控制,本文利用关节力矩传感器研究阻抗控制。首先,根据拉格朗日法建立动力学模型,基于关节力矩传感器建立阻抗控制模型;然后,根据阻抗控制算法做金相试样的打磨实验;最后,利用六维力矩传感器做对比实验,分析末端输出力的效果和改变不同阻抗参数对阻抗效果的影响。结果表明:基于关节力矩传感器的阻抗控制策略能够实现对输出力的控制,阻抗控制中力和位置能够同步稳定;惯性参数Mz越小,系统振荡越明显,稳定时间越长,但Mz不影响稳态误差;随着阻尼Bz的增加,响应速度变快,超调变大,但也不会影响系统的稳态误差;Kz主要影响系统的稳态误差,Kz越大,稳态误差越大,且系统越难稳定。所以基于关节力矩传感器的阻抗控制方法,可以完成机器人和环境接触的作业任务,力控制的精度可满足要求。

基于十字梁结构的六维力/力矩传感器全方位机械过载保护研究

六维力/力矩传感器是空间机械臂智能化的核心关键部件,随航天器发射进入太空的过程中会面临剧烈的振动与冲击。缺乏过载保护的六维力/力矩传感器可能遭到破坏而失去测量能力。针对这一问题,以十字梁结构六维力/力矩传感器为研究对象,对其受力变形特征进行理论和仿真分析,确定了各维力过载保护的原理。进而提出一种勾合式全方位机械过载保护机构,利用间隙限位实现对传感器全方位保护。间隙限位不仅能够保证传感器在过载时不被损坏,而且不会影响其正常的力测量功能。通过理论分析确定了间隙大小;并通过数值仿真验证了该结构的过载保护能力,结果表明该结构可以在不影响六维力/力矩传感器正常测量的情况下,可以分别在F_(x)/F_(y)、F_(z)、M_(x)/M_(y)、M_(z)方向提高20、20、13、20倍的过载能力。

扭矩传感器用弹性体材料微观组织与力学性能

采用金相显微镜、材料晶体结构分析仪(XRD)、发射扫描电镜(SEM)、背散射电子衍射技术(EBSD)和马氏体组织分析(TEM)等表征手段对某扭矩传感器弹性体材料的微观组织与晶体结构进行系统研究,利用洛氏硬度仪、万能材料试验机、摆锤式冲击试验机和高温弹性模量和内耗分析仪对弹性体材料的力学性能进行分析。结果表明:材料具有回火马氏体组织特征,内部有大量板条状马氏体,在马氏体内部和晶界处分布着大量颗粒状Cr_(23)C_(6)析出物,还有少量的残余奥氏体;材料洛氏硬度为:(81.9±0.4)HRB,(51.8±0.2)HRC,平均冲击功为(6.56±1.15)J,拉伸屈服强度为1170 MPa,抗拉强度为1800 MPa,伸长率为9.8%~14.4%,平均弹性模量温度系数为-4.05×10^(-4)℃。