Research on parallel load sharing principle of piezoelectric six-dimensional heavy force/torque sensor

In working process of huge heavy-load manipulators, such as the free forging machine, hydraulic die-forging press, forging manipulator, heavy grasping manipulator, large displacement manipulator, measurement of six-dimensional heavy force/torque and real-time force feedback of the operation interface are basis to realize coordinate operation control and force compliance control. It is also an effective way to raise the control accuracy and achieve highly efficient manufacturing. Facing to solve dynamic measurement problem on six-dimensional time-varying heavy load in extremely manufacturing process, the novel principle of parallel load sharing on six-dimensional heavy force/torque is put forward. The measuring principle of six-dimensional force sensor is analyzed, and the spatial model is built and decoupled. The load sharing ratios are analyzed and calculated in vertical and horizontal directions. The mapping relationship between six-dimensional heavy force/torque value to be measured and output force value is built. The finite element model of parallel piezoelectric six-dimensional heavy force/torque sensor is set up, and its static characteristics are analyzed by ANSYS software. The main parameters, which affect load sharing ratio, are analyzed. The experiments for load sharing with different diameters of parallel axis are designed. The results show that the six-dimensional heavy force/torque sensor has good linearity. Non-linearity errors are less than 1%. The parallel axis makes good effect of load sharing. The larger the diameter is, the better the load sharing effect is. The results of experiments are in accordance with the FEM analysis. The sensor has advantages of large measuring range, good linearity, high inherent frequency, and high rigidity. It can be widely used in extreme environments for real-time accurate measurement of six-dimensional time-varying huge loads on manipulators.     

Research on the parallel load sharing principle of a novel self-decoupled piezoelectric six-dimensional force sensor

This paper presents a novel integrated piezoelectric six-dimensional force sensor which can realize dynamic measurement of multi-dimensional space load. Firstly, the composition of the sensor, the spatial layout of force-sensitive components, and measurement principle are analyzed and designed. There is no interference of piezoelectric six-dimensional force sensor in theoretical analysis. Based on the principle of actual work and deformation compatibility coherence, this paper deduces the parallel load sharing principle of the piezoelectric six-dimensional force sensor. The main effect factors which affect the load sharing ratio are obtained. The finite element model of the piezoelectric six-dimensional force sensor is established. In order to verify the load sharing principle of the sensor, a load sharing test device of piezoelectric force sensor is designed and fabricated. The load sharing experimental platform is set up. The experimental results are in accordance with the theoretical analysis and simulation results. The experiments show that the multi-dimensional and heavy force measurement can be realized by the parallel arrangement of the load sharing ring and the force sensitive element in the novel integrated piezoelectric six-dimensional force sensor. The ideal load sharing effect of the sensor can be achieved by appropriate size parameters. This paper has an important guide for the design of the force measuring device according to the load sharing mode.     

WRIST FORCE SENSOR''S DYNAMIC PERFORMANCE CALIBRATION BASED ON NEGATIVE STEP RESPONSE

Negative step response experimental method is used in wrist force sensor＇s dynamic performance calibration. The exciting manner of negative step response method is the same as wrist force sensor＇s load in working. This experimental method needn＇t special experiment equipments. Experiment＇s dynamic repeatability is good. So wrist force sensor＇s dynamic performance is suitable to be calibrated by negative step response method. A new correlation wavelet transfer method is studied. By wavelet transfer method, the signal is decomposed into two dimensional spaces of time-frequency. So the problem of negative step exciting energy concentrating in the low frequency band is solved. Correlation wavelet transfer doesn＇t require that wavelet primary function be orthogonal and needn＇t wavelet reconstruction. So analyzing efficiency is high. An experimental bench is designed and manufactured to load the wrist force sensor orthogonal excitation force/moment. A piezoelectric force sensor is used to setup soft trigger and calculate the value of negative step excitation. A wrist force sensor is calibrated. The pulse response function is calculated after negative step excitation and step response have been transformed to positive step excitation and step response. The pulse response function is transferred to frequency response function. The wrist force sensor＇s dynamic characteristics are identified by the frequency response function.     

新型过约束正交并联六维力传感器测量模型与静态标定试验

面向航空航天领域对重载大吨位多维测力传感器的急需,通过引入冗余测力分支,提出一种适用于重载测力场合的新型过约束正交并联六维力传感器结构,在提高传感器结构刚度和承载能力的同时有效抑制了关节摩擦对多维力传感器测量精度的影响。基于螺旋理论,推导得到了该并联传感器一阶静力影响系数矩阵,建立理想状态下该新型过约束正交并联六维力传感器测量数学模型。考虑各测量分支的初始预紧力与刚度,基于传感器静力平衡方程与补充建立的位移协调方程,推导建立考虑初始预紧力与分支刚度因素下该新型过约束正交并联六维力传感器测量数学模型。在此基础上,设计并研制该新型过约束正交并联六维力传感器样机,搭建传感器加载标定与信号采集及处理试验系统,对新型过约束正交并联六维力传感器进行了加载标定试验。根据试验结果计算了传感器测量误差矩阵,分析得到了传感器测量精度,从而为重载过约束并联六维力传感器的开发与应用提供了参考。     

A novel piezoelectric 6-component heavy force/moment sensor for huge heavy-load manipulator's gripper

This paper presents the development of a piezoelectric 6-component heavy force/moment sensor which may be used to detect forces F_x, F_y and F_z, and moments M_x, M_y and M_z on huge heavy-load manipulator's gripper, simultaneously. The structure of the sensor is newly modeled. Piezoelectric quartz is chosen as force sensing element to realize real-time measurement. In order to investigate the validity of the proposed method, a prototype of piezoelectric 6-component heavy force/moment sensor is developed, and a characteristic test of the piezoelectric 6-component heavy force/moment sensor is performed. The experiments show that the linearity of the sensor is no more than 1%, and the interference errors are less than 3%. The carrying capability of force sensor is improved greatly by using load distribution.     

Dynamic characteristics and optimization research on PVDF piezoelectric film force sensor for steel ball cold heading machine

According to cold heading process with overloaded craft, high-impact dynamic real-time measurement requirements, this paper presents researches on dynamic characteristics and optimization of PVDF piezoelectric film force sensor for steel ball cold heading forming quality monitoring, through the combination method of mechanism analysis, mathematical modeling, numerical simulation and experimental validation. The motivation and strategic objectives are to breakthrough dynamic time-varying impacting load measuring fundamental technologies in steel ball forging process. The structure of piezoelectric film force sensor is proposed. The theoretical calculation formula of natural frequency is deduced and calculated by using MATLAB software. The mechanical performance analysis on dynamic model and structural optimization simulation by FEM is carried out. In order to study the validity of the proposed method, a prototype of the sensor is fabricated. The static and dynamic calibration devices are designed to realize calibration experiments on the fabricated PVDF piezoelectric film force sensor. The differences among experimental value, simulation value and the theoretical value are given. The nonlinear error of the fabricated sensor is 0.197%. The sensor’s first order natural frequency value is 5238 Hz. It is proved that the PVDF piezoelectric film force sensor has superior dynamic performance and high accuracy for measuring deformation in steel ball. The paper will provide important scientific basis and technical foundation to achieve superior performance steel ball.     

基于六维力传感器的机器人动力学参数辨识

采用基座布置六维力传感器的方式进行机器人动力学参数辨识。以递推牛顿-欧拉方程为基础建立机器人动力学模型，给出六维力传感器输出与机器人关节间动力学关系，分离待辨识动力学参数并确定其最小惯性参数集，最终建立基于基座六维力传感器的机器人辨识模型。为了进一步提高辨识精度，采用两层低通滤波算法推导出加速度替代公式和速度滤波算法，减少加速度和速度噪声的影响。最后，以六自由度协作机器人的前2个关节为对象，设计辨识实验，获得两关节的最小动力学参数集。通过结果逆向验算表明，基座布置六维力传感器方式能以较高的精度辨识出机器人动力学参数。     

磁力调频压电电磁复合发电设计与实验

开展了基于环境振动发电作为微电源弥补传统化学电池供能缺陷的研究。基于非线性磁力调频开发了低宽频振动能采集压电电磁复合发电系统。介绍了发电装置工作原理;利用ANSYS和Ansoft Maxwell有限元分析软件仿真分析了压电和电磁发电的输出特性;最后,搭建了压电电磁复合宽频发电装置实验测试系统,测试了发电系统在磁力自调过程中的输出特性。实验结果显示:复合发电系统在谐振频率60Hz时输出开路电压峰值为5.8V,高于压电系统(5.5V)和电磁系统(410mV)独立发电的开路电压峰值。施加磁力拓宽装置后,当压电悬臂梁沿竖直方向上下移动0~15mm时,系统适应谐振频带拓宽为45~76Hz;悬臂梁沿水平方向平移0~30mm时,谐振频带拓宽为51~70 Hz。结果表明仿真分析与实验测试结果吻合很好。该宽频带能量采集技术可用于低频振动环境的能量采集,可在频变环境中为微型低功耗系统提供低电能。     

Research on force-sensing element's spatial arrangement of piezoelectric six-component force/torque sensor

This paper proposes a novel piezoelectric six-component force/torque sensor with four-point supporting structure, and makes research on force-sensing element's spatial arrangement of the novel sensor. Two kinds of different spatial arrangements are advanced, lozenge and square arrangement. The mathematical models are built and calculated. The influence on using performance of the two kinds of different spatial arrangements of the sensor is analyzed by FEM (ANSYS software). In order to investigate the validity of the proposed method, a prototype of piezoelectric six-component force/moment sensor is developed with two kinds of different spatial arrangements, and characteristic tests of the piezoelectric six-component force/moment sensor are performed. The test shows that both of the different spatial arrangement sensors could be used to measure six-component force/torque, but the square arrangement piezoelectric six-component force/moment sensor is more suitable for measurement of six-component force/torque on axis. The interference errors of square arrangement sensor are less than 5%, which are lower than those of the lozenge arrangement sensor. The natural frequencies in six directions are analyzed and discussed.     

DYNAMIC BOUNDARY CONTROL OF BEAMS USING ACTIVE CONSTRAINED LAYER DAMPING

A globally stable boundary control strategy is developed to damp the vibration of beams fully treated with active constrained layer damping (ACLD) treatments. The devised boundary controller is compatible with the operating nature of the ACLD treatments where the strain induced generates a control force and moment acting at the boundary of the treated beam. The development of the boundary control strategy is based on a distributed-parameter model of the beam/ACLD system in order to avoid the classical spillover problems resulting from using ‘truncated’ finite element models. Such an approach makes the boundary controller capable of controlling all the modes of vibration of the ACLD-treated beams and guarantees that the total energy norm of the system is decreasing continuously with time. The control strategy is provided also with a dynamic compensator to shape the vibration damping characteristics of the ACLD in the frequency domain. The effectiveness of the ACLD in damping out the vibration of cantilevered beams is determined for different control gains and compared with the performance of conventional passive constrained layer damping (PCLD). The results obtained demonstrate the high damping characteristics of the boundary controller particularly over broad frequency bands.     

一种机器人多轴腕力传感器弹性体有限元分析

建立一种机器人腕力传感器弹性体的静、动特性的有限元计算模型,分析传感器弹性体在各种工况下的应力分布规律以及固有振动的频率和振型,为改进传感器的弹性体的设计,进行传感器结构的优化设计进行前期的准备。     

柔性自适应桁架结构的振动控制方法实验研究

为提高结构对外部环境的抗干扰能力,构造了空间柔性自适应桁架结构,并对其主动控制进行了研究。通过加速度传感器测量位移的实验,建立了由dSPACE数据采集与处理系统、压电传感器、压电作动器、桁架结构和微机实时测控组成的实时计算机控制系统。基于自适应桁架结构的有限元理论,采用改进的二次积分力反馈控制方法,研究了空间柔性自适应桁架结构的振动主动控制问题。通过正弦激励进行了实时控制实验,给出了控制前后节点18x方向的位移振幅抑制变化情况及功率谱响应曲线。实验研究结果表明,该控制方案对空间柔性结构的低频大幅振动有很好的控制效果。     

正弦力法动态力传感器灵敏度不确定度评定

随着汽车技术的日益发展,动态力传感器在汽车NVH、模态试验中用到的越来越多,一般采用动态法校准.本文依据振动与冲击传感器校准方法,以标准振动传感器为标准器,采用正弦力法校准动态力传感器灵敏度,并计算动态力传感器灵敏度测量值的不确定度,确保量准的准确一致和正确传递.     

Beam vibration control using cellulose-based Electro-Active Paper sensor

Cellulose based Electro-Active Paper (EAPap) has recently shown a great potential as an environment-friendly smart material due to its biodegradability, biocompatibility and flexibility. Lots of studies have been conducted to investigate the basic smart characteristics of EAPap, but its application has not yet developed well. In this paper, the possibility of cellulose-based Electro-Active Paper (EAPap) as a piezoelectric sensor was investigated by the vibration control of the cantilevered beam. The EAPap sample was attached at the root of the cantilevered beam and used as a vibration sensor. The piezoceramic patch was also attached at the root of the beam and played as an actuator. The voltage output of EAPap showed exact dynamic characteristics of the cantilevered beam. The frequency bandwidth and quality factor of EAPap were similar to those of piezoceramic patch, which results EAPap has similar sensing capability of piezoceramic patch. To find the application of EAPap sensor, beam vibration control was performed. EAPap sensor output was considered as a position error of the cantilevered beam and a simple PID controller was designed to suppress the vibration of the beam. The EAPap sensor output provided clear time response of the beam. The controlled system showed good vibration control performance of the beam. The results provided that the piezoelectric characteristic of EAPap has a great potential as a sensor and also as a new smart material.     

新型扭矩—轴向力传感器标定研究

扭矩—轴向力传感器是研究复合振动攻丝过程的重要装置。在振动攻丝机上安装扭矩和轴向力传感器,可以实现扭矩和轴向力的在线测量,对研究在振动攻丝过程中扭矩和轴向力的关系具有重要意义。为了研究新设计的扭矩—轴向力传感器的基本特性,选择了标定设备和标定方法对传感器进行静态标定和动态标定,得出传感器的静态特性和动态特性指标,为进一步设计和改造传感器结构提供理论依据。     

智能Timoshenko梁强迫振动响应的行波解

运用行波法求解智能Timoshenko梁的强迫振动响应.基于梁的振动行波法分析理论,介绍周期力和周期力矩激励下激励点处波的传播关系,推导在逆压电效应下,智能Timoshenko梁上某一点的响应函数,并以智能Timoshenko悬臂梁为例,得到梁不同位置的拾振点处的幅频和相频特性及不同受力状况下的智能梁的幅频特性,还得到了受迫振动的时域响应信号波形,最后将求解结果与有限元法求解结果做对比分析.分析结果表明,行波法分析可用于精确计算智能梁的强迫振动响应.     

压电应变传感特性的理论分析与实验研究

提出了一种通过测量动态应变实现工程中低频振动监测的方法.在对动态应变压电传感特性进行理论分析的基础上,对压电传感元件在不同激振频率下(0.1~40.0Hz)的动态响应进行了实验研究,实验给出了较好的测量精度.结果表明,压电传感元件灵敏度高、频响范围宽、响应时间快,符合工程中低频振动测量的要求.     

切削与振动联合测试诊断机床整机薄弱环节

通过对机床进行切削实验和振动实验联合的测试手段分析出机床整机的薄弱环节.首先,对机床进行整机模态实验分析,得到整机固有频率和振型,对其动态特性有一些初步掌握.其次,在机床进行切削实验过程中,采集记录时域下的切削力数据.通过快速傅里叶变换,在频域下对该数据进行分析,找出切削力较大时所对应的频率.最后,结合切削力测试结果和整机模态测试结果进行对比分析,找出在切削过程中切削力较大值所对应的频率恰好与整机某一阶次固有频率相重合.通过分析该阶次所对应的振型,找出整机的薄弱环节.     

带弹性足的压电管道微机器人致动机理和运动特性的研究

建立了带弹性足的压电管道微机器人的数学模型,并用此数学模型计算了该微机器人的谐振频率,所得结果与试验结果一致,这表明所建立的数学模型是正确的。此外,还研究了压电微机器人的结构参数对机器人性能的影响。     

过约束平面并联三维力/力矩传感器的研制

针对轴承的故障早期诊断和在线实时监测,提出了一种新型过约束平面并联三维力/力矩传感器。通过采用分支轴线均不过传感器中心的6条对称分布的测力分支,该传感器可同时测量轴承径向载荷和轴向力矩。根据静力学平衡方程,求解了其测量数学模型;基于传感器测量模型与性能指标分析了传感器性能,进而对其各结构参数进行优化设计。研制了传感器样机及其加载标定实验系统,开展了加载标定实验,得到了该传感器的测量精度。标定实验结果显示:传感器径向力测量精度为2.56%,力矩测量精度为0.92%,Ⅰ类误差为2.56%,最大Ⅱ类误差为2.29%。文中所做工作,为将该新型过约束平面并联三维力/力矩传感器应用于在线实时测量轴承径向载荷和轴向摩擦力矩奠定了基础。