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.

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.

Force/Moment Isotropy of 8/4-4 Parallel Six-Axis Force Sensor Based on Performance Atlases

A six-axis force sensor with parallel 8/4-4 structure is introduced and its measurement principle is analyzed.Based on condition numbers of Jacobian matrix spectral norm of the sensor,the relationship between the force and moment isotropy and some structural parameters is deduced.Orthogonal test methods are used to determine the degree of primary and secondary factors that have significant effect on sensor characteristics.Furthermore,the relationship between each performance index and the structural parameters of the sensor is analyzed by the method of the atlas,which lays a foundation for structural optimization design of the force sensor.

Dynamic analysis of double-layer and pre-stressed multi-limb six-axis force sensor

In order to adapt to the specific task, the six-axis dynamic contact force between end-effectors of intelligent robots and working condition needs to be perceived. Therefore, the dynamic property of six-axis force sensor which is installed on the end-effectors of intelligent robots will have influence on the veracity of detection and judgment to working environment contact force by intelligent robots directly. In this paper, dynamic analysis to double-layer and pre-stressed multi-limb six-axis force sensor is conducted. First, the structure of the sensor is introduced, and the limb number is confirmed by introducing the related definitions of convex analysis. Then, based on vibration of multiple-degree-of-freedom system, a mechanical vibration simplified model of double-layer and pre-stressed multiple limb six-axis force sensor is set up. After that, movement differential equations of sensor and the response of analytical expression are deduced, and the movement differential equations is solved. Finally, taking the double-layer and pre-stressed seven limb six-axis force sensor as an example, numerical calculation and simulation of deriving result is conducted, which verify the correctness and feasibility of the theoretical analysis.

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.

ROBOT'S MOTION ERROR AND ONLINE COMPENSATION BASED ON FORCE SENSOR

Robot＇s dynamic motion error and on-line compensation based on multi-axis force sensor are dealt with.It is revealed that the reasons of the error are formed and the relations of the error are delivered.A motion equation of robot＇s termination with the error is established,and then,an error matrix and an error compensation matrix of the motion equation are also defined.An on-line error＇s compensation method is put forward to decrease the displacement error,which is a degree of millimeter,shown by the result of simulation of PUMA562 robot.

Ground demonstration system based on in-orbit assembly oriented manipulator flexible force control

To eliminate the load weight limit of carrier rockets and reduce the burden on support structures,in-orbit assembly is a key technology to make design of scattering a large diameter telescope into submirror modules,which requires smooth operation of assembly robots,and flexible force control technology is necessary. A ground demonstration system is presented for in-orbit assembly focusing on flexible force control. A six-dimensional force/torque sensor and its data acquisition system are used to compensate for gravity. For translation and rotation,an algorithm for flexible control is proposed. A ground transportation demonstration verifies accuracy and smoothness of flexible force control,and the transportation and assembly task is completed automatically. The proposed system is suitable for the development of in-orbit assembly robots.

复合梁结构小型六维力传感器的优化设计

文中设计了一种三横梁与三竖梁复合的六维力传感器弹性体结构,使其外径缩小至40 mm,整个传感器装配完成后外径为45 mm。首先基于有限元技术分析了其在各种载荷条件下的应变分布,根据应变分布特性,设计了传感器的惠斯登电桥方案,推导了每个方向的输出电压公式。在此基础上,基于Box-Behnken响应面法开展弹性体结构的优化,以弹性体上应变片贴片位置的平均应变作为优化目标,通过多目标遗传算法得到最优设计参数,F_(x)、F_(y)、F_(z)、M_(x)、M_(y)、M_(z) 6个方向的平均应变分别是优化前的1.5833、1.5632、1.7338、1.5113、1.5109、2.171倍。进行样机制作,完成标定实验,使用最小二乘法求得解耦矩阵,通过解耦矩阵求得传感器的Ι类误差分别为0.18%、0.42%、0.41%、0.05%、0.49%、0.6%,ΙΙ类误差最大值为1.665%,精度高,维间耦合小,验证了该结构的可行性。

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。

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。

用于不平衡冲量测试的一种六维力传感器结构设计

单兵无后坐炮发射时运动十分剧烈、复杂,传统不平衡冲量测试装置不能准确测量各方向力系,从而对测量结果的准确性造成影响,因此,基于十字梁型结构研究了一种可实时监测各方向力系的六维力传感器。利用有限元软件建立初始模型并进行单因素分析,基于响应面法以关键尺寸参数完成响应面试验设计,结合最小二乘法得到响应面模型,采用多目标粒子群算法优化策略进行优化求解,研制原理样机并设计标定系统进行标定。仿真与实验结果表明,优化后力矩通道测量灵敏度最大提升32.24%,力通道测量灵敏度最大提升31.02%,解耦后的维间耦合最大1.01%,标定结果符合测量要求。

基于IFWA-ELM的六维力传感器解耦算法

针对六维力传感器的维间耦合严重影响测量精度的问题,提出了一种基于改进烟花算法优化极限学习机(IFWA-ELM)的解耦算法。首先,对烟花算法的爆炸半径、变异算子和选择策略进行改进,形成改进烟花算法(IFWA)。其次,采用改进烟花算法寻找极限学习机的最佳网络参数,解决极限学习机随机生成初始权值和阈值导致网络不稳定、隐含层神经元数量对网络性能影响较大的问题。为了验证算法的解耦性能,以应用于4500 m深海机械臂的六维力传感器作为研究对象,采用最小二乘法(LS)、BP神经网络(BPNN)、极限学习机(ELM)和IFWA-ELM算法进行解耦实验。实验结果表明:IFWA-ELM算法具有较好的非线性解耦能力,解耦后Ⅰ类误差控制在0.27%以内,Ⅱ类误差控制在0.13%以内,有效提高了六维力传感器的测量精度。

基于UKF的六维力传感器重力补偿算法研究

为解决人机交互中六维力传感器受末端重力影响导致示数不准确的问题,提出一种基于无迹卡尔曼滤波(Unscented Kalman Filter,UKF)算法的六维力传感器误差校正方法。通过对传感器数据进行处理和估计,实现对传感器误差的准确估计和修正,从而将传感器误差降至0~0.227 N之间。实验结果表明:该方法可以显著提高六维力传感器的测量精度,为人机交互中的精准力控制提供了可靠的技术支持。

基于混合滤波算法的力传感器信号噪声处理

为了解决六维力传感器输出信号不可避免地会被随机噪声干扰而造成准确性不佳的问题,从力传感器的简化模型出发,设计了一种基于自适应卡尔曼滤波和滑动平均值滤波的混合滤波算法。采用改进的卡尔曼滤波算法,引入渐消因子来加大当前观测量的权重,减小初始偏差带来的影响,同时将新息方差引入卡尔曼增益中来动态调整预测模型,降低过程噪声和测量噪声的干扰。最后进行滑动平均值滤波处理,得到最终的滤波数据。实验比较结果表明,混合滤波算法性能更好,有效地滤除了干扰信号,提高了传感器输出信号的稳定性和平滑性。

基于六维力传感器运动意图的识别

为解决上肢康复机器人在运动意图识别中识别信息稳定性低及采集过程复杂等问题,本文提出一种基于六维力传感器识别手部运动行为意图的人机交互系统,其涉及到位移方向及速度的变化。创建一个实时系统,利用六维力传感器获取人机交互力数据,通过二阶低通滤波方法对数据进行分析和处理,推导出运动意图信号,将其用于控制康复机器人的运动,最后建立合力与机器人运动速度之间的数学函数关系,更精细地调控机器人的运动过程。实验结果表明,六维力传感器能够准确识别患者的运动意图,实时接收患者施加力的变化并进行相应运动,达到预期目标。该研究具有一定的实际应用价值。

应变式三轴力传感器的ANSYS分析与应用

应变式三轴力传感器可用作车床切削力的测量,但其应变原理使传感器被施加压力后会产生相应的形变量,会影响到机床的加工精度。本文对LH-SZ-05三轴力传感器进行ANSYS分析及载荷试验,从试验和有限元分析方面验证应变式三轴力传感器对机床切削力测量的可行性,为应变式三轴力传感器的进一步制作和应用奠定了基础,为数控机床高速切削状态下切削力测试奠定基础。

压阻式大扭矩动态六轴力传感器设计

六轴力传感器在智能制造、精密装配、运动医疗等领域有着重要应用价值。本研究以大量程六轴力传感器为研究目标,针对六轴力解耦测量和交叉干扰抑制的技术难题,提出了一种压阻式大扭矩动态六轴力传感器的设计方法。在传感器结构设计中,采用4个直梁式三轴力传感器组合的方式进行载荷分摊,满足大力值和大扭矩的测量需求;在三轴力传感器设计中,利用弹性体应力对称性分布的特点和惠斯通电桥平衡原理,布置传感器敏感电阻并组合成测量电桥,实现三轴力的解耦测量;根据六轴力传感器在三轴力和三轴力矩作用下的应力变化规律,采用矩阵解耦的方式实现六轴力解耦测量。

空间机械臂用六维力传感器静态标定系统研究

为解决极端温度环境对空间机械臂用六维力传感器测量精度的影响,设计一种新型六维力传感器静态标定系统。系统由标定实验台、数据采集装置和分体式温控装置组成。其中标定实验台包含18路独立标定力通道,通过一次装卡可实现12个方向标定力/力矩的加载。采用研华UNO-3083G作为工控机,通过研华PCI-1742U数据采集卡配以电源转换模块实现六维力传感器输出信号的高速采集。分体式温控装置由温控箱、保温箱和保温送风管组成,可实现不同温度条件下六维力传感器的标定实验校准。在此基础上,研究了标定系统误差来源,计算了系统主要误差值。研究结果表明:相较第Ⅰ类误差,第Ⅱ类误差是影响标定系统精度的主要因素,研制的新型六维力传感器标定系统总体误差小于2.10%,满足使用需求。

面向压电式六维力传感器的动态建模与性能分析方法

针对目前六维力传感器固有频率低、动态范围小的问题,设计了一种自预紧压电式六维力传感器结构,并对其性能进行了分析。建立了传感器动态理论数学模型,绘制了传感器灵敏度、固有频率与传感器结构参数变化相关的四维图谱,基于图谱法得到了传感器灵敏度和动态固有频率随传感器结构参数变化的规律。研制出了基于多组石英晶片的压电式六维力传感器并进行了性能测试,试验结果表明,所设计的六维力传感器固有频率为9.6 KHz,动态测量范围为3.2 KHz,大于弹性体式六维力传感器2 KHz以下的动态范围,验证了所设计六维力传感器具有更高的固有频率,更大的动态范围,可更好地满足高动态范围使用要求。