LARM PKM solutions for torso design in humanoid robots

Human-like torso features are essential in humanoid robots. In this paper problems for design and operation of solutions for a robotic torso are discussed by referring to experiences and designs that have been developed at Laboratory of Robotics and Mechatronics (LARM) in Cassino, Italy. A new solution is presented with conceptual views as waist-trunk structure that makes a proper partition of the performance for walking and arm operations as sustained by a torso.     

Experimental Characterization of Operation of a Waist-Trunk System with Parallel Manipulators

An extensive research activity has been focused on the upper and lower limbs of humanoid robots. However, due to mechanical design difficulties and complex control of multi-body system, the torso of humanoid robot is somehow a neglected or simplified design part. In this paper, operation performance of a new waist-trunk system as torso for humanoid robots is presented through results of lab experimental tests. The proposed waist-trunk system is composed of two 3 DOFs (degrees of freedom) parallel manipulators, which are connected in a serial chain architecture. A prototype is built by using two prototypes of CaPaMan (Cassino Parallel Manipulator), which are convenient stiff architectures with easy-operation characteristics. Experimental tests are carried out with the aims to imitate lateral-bending and transverse-rotation movements of human torso. Operation performances like displacements, accelerations, and actuation torque are measured for a performance evaluation and design characterization of the used manipulator solution imitating human torso. Experimental test results are illustrated and discussed to show the practical operation feasibility of the proposed architecture and the operation characteristics of the built prototype.     

液压四足机器人机身扰动抑制及实验研究

针对液压四足机器人在运动过程中的机身扰动较大的问题,提出基于运动学和虚拟模型的液压四足机器人机身扰动抑制策略。分析机器人机身扰动产生的机理及其影响,建立四足机器人整机运动学方程,根据机器人实时姿态反馈抑制机身扰动。同时在机器人机身横滚和俯仰自由度上引入弹簧阻尼虚拟元件,通过调整虚拟力的大小控制机身姿态。面向机器人对角小跑步态,对机器人摆动相和支撑相进行足端轨迹规划。通过液压四足机器人平台进行实验验证,实验结果表明,该扰动抑制策略能够根据机器人的机身姿态调整关节角度,机器人机身起伏小,机器人实际运动轨迹与理论运动轨迹接近,验证了所提方法的有效性。     

外骨骼负重重心自适应凸轮连杆机构设计与性能研究

针对负重型下肢外骨骼机器人存在的问题,提出了一种新的下肢外骨骼机器人重心自适应凸轮连杆机构。具体位置在外骨骼机器人髋关节与靠背板之间,新机构可以满足人体躯干与负重作相反转动,使人体上肢躯干重心前移,抵消负重带来的反向力矩,躯干前倾可增强人体负重行走稳定性。首先分析了新机构工作原理,其次通过重心变化和载荷分配分析验证了新机构有效性,最后对机构仿真验证得出不同负重对应不同躯干的前倾角度,达到重心驱动的效果。MATLAB仿真结果表明：新结构能够满足人体随不同负重而调整对应前倾角度。     

基于蒙皮模型和WEOPA的人体外形和运动跟踪

为了解决多关节人体三维外形和运动跟踪问题,提出了一种基于蒙皮模型(skinned model)和加权扩展正交普鲁克分析(weighted extended orthogonal procrustes analysis,WEOPA)的三维人体外形和运动跟踪方法。首先使用Shape-From-Silhouettes方法从当前帧多目视频图像轮廓中计算出被跟踪人物的可视外壳,然后建立人物先验蒙皮模型并与之匹配,其中蒙皮模型的引入使得多关节人体三维外形和运动跟踪问题被转化为一个分层非线性最小二乘匹配问题。考虑到在先验模型获取中肢体间连接部位产生的网格顶点粘连问题,采用WEOPA算法来进行求解,其中通过引入4种不同的权值分配策略,克服了顶点粘连对匹配的影响,并有效利用了匹配点对的几何法线信息。实验结果表明,该方法能对人物外形和运动进行有效的跟踪。     

外骨骼机器人系统中人体下肢关节力矩动态解算

利用下肢外骨骼关节位移传感器及惯性导航单元采集人体运动信息,计算获得下肢髋、膝关节的相对角度以及躯干的姿态和加速度,通过动力学逆解实时解算穿戴者运动所需的关节驱动力矩。在此过程中,利用人体五杆模型,对人体下肢的运动进行了运动学和动力学分析,通过Matlab/Simulink软件编程求解,得到了人体下肢关节在连续步态周期内关节力矩的变化,通过对比计算获得的支撑踝关节力矩值与足底力传感器实测值,证明了关节力矩求解方法的正确性,保障了外骨骼机器人能够根据此力矩对穿戴者提供助力。     

基于中国人体特征的正面碰撞假人的开发策略探讨

采用计算机仿真方法探讨了在现有Hybrid Ⅲ假人基础上通过较少的改变来开发符合中国人体特征的假人的可行性。根据比例缩放方法建立了整体符合中国50百分位人体的假人有限元模型。考虑到中美两国人体最大差异在于四肢,且躯干全部缩放后加工难度较大,故建立了以美国人体特征为基础仅缩放假人四肢和调整部分躯干部件的假人模型,同时,改变假人的材料参数得到了另外一个假人模型。对以上三个假人模型进行碰撞仿真,结果表明,改变假人的材料参数对其碰撞响应的影响很小,而缩放假人外形尺寸对其碰撞响应影响较大,且结果显示缩放假人四肢并调整部分躯干部件的假人与缩放全体段假人的动态响应基本吻合。因此,采用部分缩放的方法来开发中国假人是可行的。     

Variative designing of grinding operations

A new method is proposed for the design of grinding operations—that is, the selection of tool characteristics and machining conditions. In this approach, tool performance is predicted, and combinations of wheel characteristics and grinding conditions are selected on that basis, with simultaneous satisfaction of all the constraints on the grinding operations and the specifications in the drawing of the part. By variant design of the grinding operations, the tool best suited to specific grinding conditions may be identified during preproduction.     

An Investigation into Improving Worn Electrode Reliability in the Electrical Discharge Machining Process

In this paper, the use of a strength–stress interference model to study electrode reliability during wear in electrical discharge machining has been reported. In order to improve the electrode reliability, the Taguchi method, which is a powerful tool for parameter design of performance characteristics is used to determine machining parameters for minimum electrode wear ratio in electrical discharge machining operations. Through this study, not only is the electrode reliability improved, but also the machining parameters that significantly affect the electrode wear ratio in electrical discharge machining operations are obtained. Experimental results are provided to verify this approach.     

Experimental study and model validation of selective spinal cord and brain hypothermia induced by a simple torso-cooling pad

In vivo experiments have been performed to test the effectiveness of a torso-cooling pad to reduce the temperature in the spinal cord and brain in rats. Coolant was circulated through the cooling pad to provide either mild or moderate cooling. Temperatures in the brain tissue, on the head surface, and on the spine and back surfaces were measured. During mild cooling, the temperature on the back surface was 22.82 +/- 2.43 degrees C compared to 29.34 +/- 1.94 degrees C on the spine surface. The temperature on the back surface during moderate cooling was 13.66 +/- 1.28 degrees C compared to 24.12 +/- 5.7 degrees C on the spine surface. Although the temperature in the brain tissue did not drastically deviate from its baseline value during cooling, there was a difference between the rectal and brain temperatures during cooling, which suggests mild hypothermia in the brain tissue. Using experimental data, theoretical models of the rat head and torso were developed to predict the regional temperatures and to validate the rat models. There was good agreement between the theoretical and experimental temperatures in the torso region. Differences between the predicted and measured temperatures in the brain are likely to be the result of imperfect mixing between the cold spinal fluid and the warm cerebrospinal fluid that surrounds the brain.     

基于神经-肌肉架构的仿生并联躯干柔顺控制

模仿动物躯干的构造搭建了六自由度仿生并联躯干。提出一种神经肌肉控制方法,通过控制虚拟肌肉的伸缩使仿生并联躯干在外力冲击下进行柔顺运动。建立了神经运动控制网络,根据非线性振荡器生成的节律信号规划了仿生并联躯干的运动轨迹。运用逆运动学求解了关节转角,按照转角信息控制电机带动仿生并联躯干运动。构建的虚拟肌肉模型在外力作用下驱动躯干关节产生顺应运动。仿真模型和并联躯干实体测试结果表明该方法可有效提高并联躯干的柔顺缓冲性和快速响应性。     

Effects of the influence factors in adhesive workpiece clamping with ice: experimental study and performance evaluation for industrial manufacturing applications

An ice-clamping device holds workpieces by using the adhesive bond of frozen water. Demanding parts like micro pieces, complex geometries, or soft materials pose challenges in manufacturing processes, being hard to clamp during machining operations. By encapsulating a workpiece form and force-fitted, ice clamping introduces an innovative technique towards a flexible, deformation-reduced, damage-free, and sustainable fixture technology addressing as well the demands of green manufacturing. Due to the relative novelty, basic information about the technique’s capability are rare. To address the question of industrial applicability, the paper investigates influence factors, like reachable strengths in the presence of shear and tensile forces as well as torque, dynamic loads, the impact of workpiece materials, and the effect of process heat. The main findings of the proposed clamping technique are discussed with regard to a targeted use in common industrial machining operations like milling, drilling, or turning. A performance evaluation was executed by means of high-speed cutting operations, using, inter alia, a hard-to-clamp workpiece.     

Exploring Operation Mechanisms of the Flexible Metal-to-Metal Face Seal: Part I—Numerical Modeling and Validations

A numerical model was developed for a special type of metal-to-metal face seal to evaluate its performance under various operating conditions. The model considers interactions among surface deformations due to thermomechanical twists, oil transport in the sealing band, and heat transfer in the seal pair simultaneously. In the meantime, experimental efforts have been made to measure the friction coefficients and seal temperatures during different operations. The model predictions were then compared with the experiment results through the two above-mentioned quantities. The comparisons show that the numerical simulations consistently overestimate the friction by 15–20%. However, the overall trend of friction variation with speed and some details of the friction have been captured, indicating that the current models are able to properly predict tribology of seal operations.     

AN APPRAISAL OF EMPIRICAL MODELING AND PROPRIETARY SOFTWARE DATABASES FOR PERFORMANCE PREDICTION OF MACHINING OPERATIONS

In this paper the importance of quantitatively reliable technological machining performance measures and their influence on the economic performance of machining operations has been demonstrated. It has been shown that since F.W. Taylor's time these technological performance measures were required to select cutting conditions which optimise the economic performance of machining operations and that the trend to use 'recommended' rather than economic 'optimal' cutting conditions can result in significant economic penalties which need to be eliminated. The 'empirical' approach and equations developed since Taylor's seminal paper are reviewed as are some computerised technological machining performance databases incorporated in modem proprietary software packages. The various strategies used to minimise the amount of testing required to establish the comprehensive sets of 'empirical' equations in manuals and handbooks published in the U.S.A., China and Russia are described and the penalties in the quantitative reliability of the predictions discussed. Two computerised machining performance databases are explored, the 'short cuts' identified and the plausibility of the predictions discussed. While the mathematical form of the 'empirical' equations in those databases could be considered plausible the values of the exponents and constants in the equations, which greatly affect the quantitative reliability of the performance predictions, can be considered dubious for the drilling databases. It is shown that a 'large gap' exists between the development of reliable technological machining performance databases and the selection of cutting conditions which optimize the economic performance of machining operations advocated by Taylor since 1907.     

Assessment of movement distribution in the lumbar spine using the instantaneous axis of rotation

Journal of Mechanical Science and Technology - The position of the torso and the magnitude of exertion are thought to influence the distribution pattern of intervertebral movements within the...     

A MACHINING PERFORMANCE STUDY IN DRY CONTOUR TURNING OF ALUMINUM ALLOYS WITH FLAT-FACED AND GROOVED DIAMOND TOOLS

This paper presents the results from an experimental study of dry contour turning operations on aluminum alloys (6061B and 2011-T3) using PCD flat-faced and diamond coated grooved tools. The machining performance is assessed on the basis of cutting forces, chip flow, chip-form and surface roughness observed during contour turning operations. The constantly varying cutting conditions (especially effective depth of cut due to varying geometry of the contour surface) and effective tool geometry cause a wide fluctuation in cutting forces and the ensuing chip flow. The chip flow angle is measured along the contour geometry using high-speed filming techniques and these results are compared with predicted chip flow values from the measured experimental cutting forces (which are measured along the entire contour geometry). The resultant surface roughness at different locations along the contour profile is measured and correlated with the chip flow and chip-form variations. Machining performance issues specifically relevant to dry contour turning of aluminum (such as problems due to poor chip flow and the resultant poor surface roughness) are studied and the effectiveness of selective work-tool (both tool material and tool geometry) pairs is illustrated.     

滚动轴承性能不确定性与可靠性评估

以灰色系统理论和泊松计数过程为基础,对滚动轴承性能不确定性进行参数量化,并在设定阈值条件下研究不同工况下轴承性能可靠性,进而建立其性能不确定性与可靠性匹配序列,以寻找轴承服役期间两者之间的内在联系。根据轴承运转期间某属性时间序列,进行灰自助处理得到该属性的不确定性;然后参考设定阈值进行泊松计数,获得该时间序列的有效变异强度,进而得到其性能运转可靠性;最后分析不确定性与可靠性两者之间的灰关系。实验结果显示,滚动轴承性能不确定性与可靠性的演变状况可以被真实描述,两者归一化处理结果十分相像,有着明显的灰关系,各案例的实验结果保持良好的一致性。     

AN APPRAISAL OF EMPIRICAL MODELING AND PROPRIETARY SOFTWARE DATABASES FOR PERFORMANCE PREDICTION OF MACHINING OPERATIONS

Abstract

In this paper the importance of quantitatively reliable technological machining performance measures and their influence on the economic performance of machining operations has been demonstrated. It has been shown that since F.W. Taylor's time these technological performance measures were required to select cutting conditions which optimise the economic performance of machining operations and that the trend to use ‘recommended’ rather than economic ‘optimal’ cutting conditions can result in significant economic penalties which need to be eliminated. The ‘empirical’ approach and equations developed since Taylor's seminal paper are reviewed as are some computerised technological machining performance databases incorporated in modem proprietary software packages. The various strategies used to minimise the amount of testing required to establish the comprehensive sets of ‘empirical’ equations in manuals and handbooks published in the U.S.A., China and Russia are described and the penalties in the quantitative reliability of the predictions discussed. Two computerised machining performance databases are explored, the ‘short cuts’ identified and the plausibility of the predictions discussed. While the mathematical form of the ‘empirical’ equations in those databases could be considered plausible the values of the exponents and constants in the equations, which greatly affect the quantitative reliability of the performance predictions, can be considered dubious for the drilling databases. It is shown that a ‘large gap’ exists between the development of reliable technological machining performance databases and the selection of cutting conditions which optimize the economic performance of machining operations advocated by Taylor since 1907.     

A GENERIC MECHANICS OF CUTTING APPROACH TO PREDICTIVE TECHNOLOGICAL PERFORMANCE MODELING OF THE WIDE SPECTRUM OF MACHINING OPERATIONS

The need for quantitatively reliable predictive models for the many technological machining performance measures to optimize the economic performance of machining operations, and to design machine tools and cutting tools that enhance this economic performance, has been highlighted. Also highlighted is the formidable task of establishing the required quantitative technological performance data and equations, and the gap between theory and practice. The development and generic nature of the “unified or generalized mechanics of cutting approach” to technological performance prediction for the wide spectrum of machining operations is presented and discussed in this paper. Suggestions for overcoming some practical difficulties and extending the scope of this predictive modeling approach are also considered.     

A GENERIC MECHANICS OF CUTTING APPROACH TO PREDICTIVE TECHNOLOGICAL PERFORMANCE MODELING OF THE WIDE SPECTRUM OF MACHINING OPERATIONS

ABSTRACT

The need for quantitatively reliable predictive models for the many technological machining performance measures to optimize the economic performance of machining operations, and to design machine tools and cutting tools that enhance this economic performance, has been highlighted. Also highlighted is the formidable task of establishing the required quantitative technological performance data and equations, and the gap between theory and practice. The development and generic nature of the “unified or generalized mechanics of cutting approach” to technological performance prediction for the wide spectrum of machining operations is presented and discussed in this paper. Suggestions for overcoming some practical difficulties and extending the scope of this predictive modeling approach are also considered.