【温馨提示】购买原稿文件请充值后自助下载。全部文件那张截图中的文件为本资料所有内容，下载后即可获得。预览截图请勿抄袭，原稿文件完整清晰，无水印，可编辑。有疑问可以咨询QQ：414951605或1304139763AbstractPneumatic manipulator is a robot which is based on Pressure-driven. The robot is the combination of expertise and expertise of an anthropomorphic machine electro-mechanical device, not simply instead of manual labor. It owns both the rapid response to the environment state and the ability of a long continuous operation, high accuracy, and the resistance to harsh environments. It is mainly used to crawl at a fixed program, and carry objects and operate tools automatically. So Pneumatic Manipulator can reduce labor intensity, improve production efficiency. However, its disadvantages are obvious. Pneumatic Manipulator getting the precise positioning is very difficult, especially achieving multi-point positioning to anywhere because of the great compressibility of gas. Also, the compressibility limits a load to be too heavy. Traditional pneumatic system only relies on the set position of the mechanical giving location and reliable positioning and velocity which relies on a single one-way throttle. So it is often unable to meet many requirements of the automatic control equipment. After a deep study, we found that the pneumatic flip robot on the current production line can only be achieved crawling and flip function once in a movement process whose efficiency is too low. So we design a pneumatic flip robot which can achieve the two crawling and flipping in a motion process. There is no doubt that the pneumatic flip robot can improve work efficiency and speed up the production efficiency. Key words: pneumatic devices; robot; turning device; clip bottle;目录摘要Abstract第1章绪论 11.1 引言 11.2气动机械手的发展 11.2.1国外气动机械手状况 11.2.2国内气动机械手情况 31.3发展趋势 31.3.1重复高精度 31.3.2模块化 31.3.3无给油化 41.3.4 机电气一体化 41.4 机械手夹持部件结构示意图 41.4.1 外夹持型机械手 41.4.2 内夹持型机械手 51.5国内外气动机械手设计举例 51.5.1与模具切割相结合 51.5.2 机械手虚拟样机 61.5.3 高精度机械手 6第2章气动翻转机械手总体设计 82.1 抓取系统的初步设计 82.2 翻转系统的初步设计 82.2.1 锥齿轮电机翻转 82.2.2 链轮链条气缸翻转 92.2.3 翻转方案选择 92.3气动翻转机械手的三维建模、装配思路 102.3.1各部分零件设计 102.3.2 气动翻转机械手的运动学仿真 102.3.3 研究思路方案、可行性分析及预期成果 11第3章气动翻转机械手重要零部件设计校核及其装配 123.1气缸的设计和校核 123.1.1 夹紧系统气缸设计和校核 123.1.2 翻转系统气缸设计和校核 143.2齿轮设计和校核 153.2.1齿轮参数的选择 153.2.2齿轮几何尺寸确定 153.2.3齿根弯曲疲劳强度计算 163.3齿条的设计和校核 183.3.1齿条的设计 183.4 固定机架上的轴设计和校核 203.4.1求输入轴上的功率、转速和转矩 203.4.2求作用在齿轮上的力 203.4.3 初步确定轴的最小直径 213.4.4轴的结构设计 213.4.5精确校核轴的疲劳强度 233.5圆锥滚子轴承的设计和校核 253.6键连接设计和校核 263.6.1输入轴键计算 263.6.2中间轴键计算 263.6.3输出轴键计算 273.7联轴器的设计和校核 27第4章三维建模和运动仿真 294.1 整体装配图 294.2夹紧系统装配图 294.3气缸推动和翻转系统装配图 304.4 气缸推动夹紧装置系统装配图 30第5章总结与展望 325.1总结 325.2展望 32参考文献 33致谢 35第1章绪论1.1 引言近20年来，气动技术的应用领域迅速拓宽，尤其是在各种自动化生产线上得到广泛应用。电气可编程控制技术与气动技术相结合, 使整个系统自动化程度更高, 控制方式更灵活, 性能更加可靠; 气动机械手、柔性自动生产线的迅速发展, 对气动技术提出了更多更高的要求;由于气动脉宽调制技术具有结构简单、抗污染能力强和成本低廉等特点, 国内外都在大力研发气动机械手。1.2气动机械手的发展1.2.1国外气动机械手状况从各国的行业统计资料来看, 近30多年来, 气动行业发展很快。20世纪70年代, 液压与气动元件的产值比约为9：1, 而30多年后的今天, 在工业技术发达的欧美、日本等国家, 该比例已达到6：4, 甚至接近5：5。90年代初，有布鲁塞尔皇家军事学院Y.Bando教授领导的综合技术部开发研制的电子气动机器人-"阿基里斯"六脚勘测员，也被称为FESTO的"六足动物"12。Y.Bando教授采用了世界上著名的德国FESTO生产的气动元件、可编程控制器和传感器等，创造了一个在荷马史诗中最健壮最勇敢的希腊英雄-阿基里斯。它能在人不易进入的危险区域、污染或放射性的环境中进行地形侦察。六脚电子气动机器人的上方安装了一个照相机来探视障碍物，能安全的绕过它，并在行走过程中记录和收集数据。六脚电子气动机器人行走的所有程序由FPC101-B可编程控制器控制，FPC101-B能在六个不同方向控制机器人的运动，最大行走速度0.1m/s。通常如果有三个脚与地面接触，机器人便能以一种平稳的姿态行走，六脚中的每一个脚都有三个自由度，一个直线气缸把脚提起、放下，一个摆动马达控制脚伸展、退回，另一个摆动马达则负责围绕脚的轴心作旋转运动。每个气缸都装备了调节速度用的单向节流阀，使机械驱动部件在运动时保持平稳，即在无级调速状态下工作。控制气缸的阀内置在机器人体内，由FPC101-B可编程控制器控制。当接通电源时，气动阀被切换到工作状态位置，当关闭电源时，他们便回到初始位置。此外，操作者能在任何一点上停止机器人的运动，如果机器人的传感器在它的有效范围内检测到障碍物，机器人也会自动停止。由汉诺威大学材料科学研究院设计的气动攀墙机器人，它能在两个相互垂直的表面上行走(包括从地面到墙面或者从墙面到天花板上)。该机器人轴心的圆周边上装备着等距离(根据步距设置)的吸盘和气缸，一组吸盘吸力与另一组吸盘吸力的交替交换，类似脚踏似的运动方式，使机器人产生旋转步进运动。这种攀墙式机器人可被用于工具搬运或执行多种操作，如在核能发电站、高层建筑物气动机械手位置伺服控制系统的研究或船舶上进行清扫、检验和安装工作。机器人用遥控方式进行半自动操作，操作者只需输入运行的目标距离，然后计算机便能自动计算出必要的单步运行。操作者可对机器人进行监控。国外的设计人员对于机械手的设计理念已经非常成熟。Wright等人分析比较了机械手与人手抓取系统，并把机械手分成与机器人手臂和控制系统相兼容、安全抓取和握持对象、准确的完成复杂性任务三种类别。许多工厂的机械手的例子和机械手设计指导方针也被描述进去了。Pham等人总结了机械手在不同应用环境下设计方案应该如何选择。在他们的研究中，影响机械手如何选择的变量如下：（a）成分，（b）任务,(c)环境，（d）机械臂和控制条件。“成分”这个变量包括几何、形状、重量、表面质量和温度，这些因素都需要考虑好。对于可重构系统，他们以形状和大小为标准又把这个变量分成了其他家族。对于“任务”这个变量，除了机械手的类型、不同组成部分的数量、准确性及周期需要考虑外，还有主要的操作处理如抓取、握持、移动和放置都要考虑。在合适的地方设计核实的机械手，必须考虑所有的因素，而且验证性的测试必须要多做。为了减少疲劳效应，pham等人开发了一个用于选择机械手的专家系统。瑞典EIET ROIUX 公司于最近创造一种新产品一一气动机械手。这种机械手以压缩空气为动力, 小巧灵便,它装在一个圆形竖柱上, 该圆柱又能上下移动0 至150 mm , 左右移动350mm，机械手的最高速度为1000m/s，定位精度为500m/s;两个机械手各能举起5kg重物。1.2.2国内气动机械手情况我国改革开放以来，气动行业发展很快。1986年至2003年间，气动元件产值的年第增率达24.2，高于中国机械工业产值平均年递增率10的水平。虽然市场和应用发展迅速，但是我国的气动技术与欧美、日本等国相比，还存在着相当大的差距。我国在气动技术的研究与开发的方面，缺乏先进的仪器与设备，研究开发手段落后，技术力量差，每年问世的新产品数量极其有限。在许多开发与研究领域还是空白，因此必须跟踪国外气动技术的最新发展动向，以减小差距，提高我国气动技术的水平。1.3发展趋势1.3.1重复高精度精度是指机器人、机械手到达指定点的精确程度, 它与驱动器的分辨率以及反馈装置有关。重复精度是指如果动作重复多次, 机械手到达同样位置的精确程度重复精度比精度更重要, 如果一个机器人定位不够精确, 通常会显示一个固定的误差, 这个误差是可以预测的, 因此可以通过编程予以校正。重复精度限定的是一个随机误差的范围, 它通过一定次数地重复运行机器人来测定。随着微电子技术和现代控制技术的发展, 以及气动伺服技术走出实验室和气动伺服定位系统的成套化。气动机械手的重复精度将越来越高, 它的应用领域也将更广阔, 如核工业和军事工业等。1.3.2模块化有的公司把带有系列导向驱动装置的气动机械手称为简单的传输技术, 而把模块化拼装的气动机械手称为现代传输技术。模块化拼装的气动机械手比组合导向驱动装置更具灵活的安装体系。它集成电接口和带电缆及气管的导向系统装置, 使机械手运动自如。由于模块化气动机械手的驱动部件采用了特殊设计的滚珠轴承, 使它具有高刚性、高强度及精确的导向精度。优良的定位精度也是新一代气动机械手的一个重要特点。模块化气动机械手使同一机械手可能由于应用不同的模块而具有不同的功能, 扩大了机械手的应用范围, 是气动机械手的一个重要的发展方向。智能阀岛的出现对提高模块化气动机械手和气动机器人的性能起到了十分重要的支持作用。因为智能阀岛本来就是模块化的设备, 特别是紧凑型CP 阀岛, 它对分散上的集中控制起了十分重要的作用, 特别对机械手中的移动模块。1.3.3无给油化为了适应食品、医药、生物工程、电子、纺织、精密仪器等行业的无污染要求, 不加润滑脂的不供油润滑元件已经问世。随着材料技术的进步, 新型材料(如烧结金属石墨材料) 的出现, 构造特殊、用自润滑材料制造的无润滑元件, 不仅节省润滑油、不污染环境, 而且系统简单、摩擦性能稳定、成本低、寿命长。1.3.4 机电气一体化由“可编程序控制器-传感器-气动元件”组成的典型的控制系统仍然是自动化技术的重要方面;发展与电子技术相结合的自适应控制气动元件, 使气动技术从“开关控制” 进入到高精度的“ 反馈控制”; 省配线的复合集成系统, 不仅减少配线、配管和元件, 而且拆装简单, 大大提高了系统的可靠性。而今, 电磁阀的线圈功率越来越小, 而PLC 的输出功率在增大, 由PLC直接控制线圈变得越来越可能。气动机械手、气动控制越来越离不开PLC, 而阀岛技术的发展, 又使PLC 在气动机械手、气动控制中变得更加得心应手。1.4 机械手夹持部件结构示意图1.4.1 外夹持型机械手图1-2为一种较简单平行开闭手爪的结构。气缸的活塞有压缩空气驱动，通过活塞杆7上的支点轴2带动拨叉3转动，再通过传动轴4使手爪1沿导向槽做平行移动，图中为双作用气缸，也可为单作用气缸返回运动靠弹簧完成。该结构的特点是重量轻，体积小，最小型重量为75g，最大型为300g，因此，可以与小型机械手配套使用。

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关键词：: 气动翻转机械手部件设计仿真 ppt

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Abstract
　　　Pneumatic manipulator is a robot which is based on Pressure-driven. The robot is the combination of expertise and expertise of an anthropomorphic machine electro-mechanical device, not simply instead of manual labor. It owns both the rapid response to the environment state and the ability of a long continuous operation, high accuracy, and the resistance to harsh environments. It is mainly used to crawl at a fixed program, and carry objects and operate tools automatically. So Pneumatic Manipulator can reduce labor intensity, improve production efficiency. However, its disadvantages are obvious. Pneumatic Manipulator getting the precise positioning is very difficult, especially achieving multi-point positioning to anywhere because of the great compressibility of gas. Also, the compressibility limits a load to be too heavy. Traditional pneumatic system only relies on the set position of the mechanical giving location and reliable positioning and velocity which relies on a single one-way throttle. So it is often unable to meet many requirements of the automatic control equipment.
　　　 After a deep study, we found that the pneumatic flip robot on the current production line can only be achieved crawling and flip function once in a movement process whose efficiency is too low. So we design a pneumatic flip robot which can achieve the two crawling and flipping in a motion process. There is no doubt that the pneumatic flip robot can improve work efficiency and speed up the production efficiency.
Key words: pneumatic devices; robot; turning device; clip bottle;

目录
摘要
Abstract
第1章绪论 1
1.1 引言 1
1.2气动机械手的发展 1
1.2.1国外气动机械手状况 1
1.2.2国内气动机械手情况 3
1.3发展趋势 3
1.3.1重复高精度 3
1.3.2模块化 3
1.3.3无给油化 4
1.3.4 机电气一体化 4
1.4 机械手夹持部件结构示意图 4
1.4.1 外夹持型机械手 4
1.4.2 内夹持型机械手 5
1.5国内外气动机械手设计举例 5
1.5.1与模具切割相结合 5
1.5.2 机械手虚拟样机 6
1.5.3 高精度机械手 6
第2章气动翻转机械手总体设计 8
2.1 抓取系统的初步设计 8
2.2 翻转系统的初步设计 8
2.2.1 锥齿轮电机翻转 8
2.2.2 链轮链条气缸翻转 9
2.2.3 翻转方案选择 9
2.3气动翻转机械手的三维建模、装配思路 10
2.3.1各部分零件设计 10

2.3.2 气动翻转机械手的运动学仿真 10
2.3.3 研究思路方案、可行性分析及预期成果 11
第3章气动翻转机械手重要零部件设计校核及其装配 12
3.1气缸的设计和校核 12
3.1.1 夹紧系统气缸设计和校核 12
3.1.2 翻转系统气缸设计和校核 14
3.2齿轮设计和校核 15
3.2.1齿轮参数的选择 15
3.2.2齿轮几何尺寸确定 15
3.2.3齿根弯曲疲劳强度计算 16
3.3齿条的设计和校核 18
3.3.1齿条的设计 18
3.4 固定机架上的轴设计和校核 20
3.4.1求输入轴上的功率、转速和转矩 20
3.4.2求作用在齿轮上的力 20
3.4.3 初步确定轴的最小直径 21
3.4.4轴的结构设计 21
3.4.5精确校核轴的疲劳强度 23
3.5圆锥滚子轴承的设计和校核 25
3.6键连接设计和校核 26
3.6.1输入轴键计算 26
3.6.2中间轴键计算 26
3.6.3输出轴键计算 27
3.7联轴器的设计和校核 27
第4章三维建模和运动仿真 29
4.1 整体装配图 29
4.2夹紧系统装配图 29
4.3气缸推动和翻转系统装配图 30
4.4 气缸推动夹紧装置系统装配图 30
第5章总结与展望 32

5.1总结 32
5.2展望 32
参考文献 33
致谢 35

第1章绪论
1.1 引言
　　　近20年来，气动技术的应用领域迅速拓宽，尤其是在各种自动化生产线上得到广泛应用。电气可编程控制技术与气动技术相结合, 使整个系统自动化程度更高, 控制方式更灵活, 性能更加可靠; 气动机械手、柔性自动生产线的迅速发展, 对气动技术提出了更多更高的要求;由于气动脉宽调制技术具有结构简单、抗污染能力强和成本低廉等特点, 国内外都在大力研发气动机械手。
1.2气动机械手的发展
1.2.1国外气动机械手状况
　　　从各国的行业统计资料来看, 近30多年来, 气动行业发展很快。20世纪70年代, 液压与气动元件的产值比约为9：1, 而30多年后的今天, 在工业技术发达的欧美、日本等国家, 该比例已达到6：4, 甚至接近5：5。
　　　90年代初，有布鲁塞尔皇家军事学院Y.Bando教授领导的综合技术部开发研制的电子气动机器人--"阿基里斯"六脚勘测员，也被称为FESTO的"六足动物"[12]。Y.Bando教授采用了世界上著名的德国FESTO生产的气动元件、可编程控制器和传感器等，创造了一个在荷马史诗中最健壮最勇敢的希腊英雄--阿基里斯。它能在人不易进入的危险区域、污染或放射性的环境中进行地形侦察。六脚电子气动机器人的上方安装了一个照相机来探视障碍物，能安全的绕过它，并在行走过程中记录和收集数据。六脚电子气动机器人行走的所有程序由FPC101-B可编程控制器控制，FPC101-B能在六个不同方向控制机器人的运动，最大行走速度0.1m/s。通常如果有三个脚与地面接触，机器人便能以一种平稳的姿态行走，六脚中的每一个脚都有三个自由度，一个直线气缸把脚提起、放下，一个摆动马达控制脚伸展、退回，另一个摆动马达则负责围绕脚的轴心作旋转运动。每个气缸都装备了调节速度用的单向节流阀，使机械驱动部件在运动时保持平稳，即在无级调速状态下工作。控制气缸的阀内置在机器人体内，由FPC101-B可编程控制器控制。当接通电源时，气动阀被切换到工作状态位置，当关闭电源时，他们便回到初始位置。此外，操作者能在任何一点
上停止机器人的运动，如果机器人的传感器在它的有效范围内检测到障碍物，机器人也会自动停止。
　　　由汉诺威大学材料科学研究院设计的气动攀墙机器人，它能在两个相互垂直的表面上行走(包括从地面到墙面或者从墙面到天花板上)。该机器人轴心的圆周边上装备着等距离(根据步距设置)的吸盘和气缸，一组吸盘吸力与另一组吸盘吸力的交替交换，类似脚踏似的运动方式，使机器人产生旋转步进运动。这种攀墙式机器人可被用于工具搬运或执行多种操作，如在核能发电站、高层建筑物气动机械手位置伺服控制系统的研究或船舶上进行清扫、检验和安装工作。机器人用遥控方式进行半自动操作，操作者只需输入运行的目标距离，然后计算机便能自动计算出必要的单步运行。操作者可对机器人进行监控。
　　　国外的设计人员对于机械手的设计理念已经非常成熟。Wright等人分析比较了机械手与人手抓取系统，并把机械手分成与机器人手臂和控制系统相兼容、安全抓取和握持对象、准确的完成复杂性任务三种类别。许多工厂的机械手的例子和机械手设计指导方针也被描述进去了。Pham等人总结了机械手在不同应用环境下设计方案应该如何选择。在他们的研究中，影响机械手如何选择的变量如下：（a）成分，（b）任务,(c)环境，（d）机械臂和控制条件。“成分”这个变量包括几何、形状、重量、表面质量和温度，这些因素都需要考虑好。对于可重构系统，他们以形状和大小为标准又把这个变量分成了其他家族。对于“任务”这个变量，除了机械手的类型、不同组成部分的数量、准确性及周期需要考虑外，还有主要的操作处理如抓取、握持、移动和放置都要考虑。在合适的地方设计核实的机械手，必须考虑所有的因素，而且验证性的测试必须要多做。为了减少疲劳效应，pham等人开发了一个用于选择机械手的专家系统。瑞典EIET ROIUX 公司于最近创造一种新产品一一气动机械手。这种机械手以压缩空气为动力, 小巧灵便,它装在一个圆形竖柱上, 该圆柱又能上下移动0 至150 mm , 左右移动350mm，机械手的最高速度为1000m/s，定位精度为500m/s;两个机械手各能举起5kg重物。

1.2.2国内气动机械手情况
　　　我国改革开放以来，气动行业发展很快。1986年至2003年间，气动元件产值的年第增率达24.2，高于中国机械工业产值平均年递增率10的水平。虽然市场和应用发展迅速，但是我国的气动技术与欧美、日本等国相比，还存在着相当大的差距。我国在气动技术的研究与开发的方面，缺乏先进的仪器与设备，研究开发手段落后，技术力量差，每年问世的新产品数量极其有限。在许多开发与研究领域还是空白，因此必须跟踪国外气动技术的最新发展动向，以减小差距，提高我国气动技术的水平。
1.3发展趋势
1.3.1重复高精度
　　　精度是指机器人、机械手到达指定点的精确程度, 它与驱动器的分辨率以及反馈装置有关。重复精度是指如果动作重复多次, 机械手到达同样位置的精确程度重复精度比精度更重要, 如果一个机器人定位不够精确, 通常会显示一个固定的误差, 这个误差是可以预测的, 因此可以通过编程予以校正。重复精度限定的是一个随机误差的范围, 它通过一定次数地重复运行机器人来测定。随着微电子技术和现代控制技术的发展, 以及气动伺服技术走出实验室和气动伺服定位系统的成套化。气动机械手的重复精度将越来越高, 它的应用领域也将更广阔, 如核工业和军事工业等。
1.3.2模块化
　　　有的公司把带有系列导向驱动装置的气动机械手称为简单的传输技术, 而把模块化拼装的气动机械手称为现代传输技术。模块化拼装的气动机械手比组合导向驱动装置更具灵活的安装体系。它集成电接口和带电缆及气管的导向系统装置, 使机械手运动自如。由于模块化气动机械手的驱动部件采用了特殊设计的滚珠轴承, 使它具有高刚性、高强度及精确的导向精度。优良的定位精度也是新一代气动机械手的一个重要特点。模块化气动机械手使同一机械手可能由于应用不同的模块而具有不同的功能, 扩大了机械手的应用范围, 是气动机械手的一个重要的发展方向。智能阀岛的出现对提高模块化气动机械手和气动机器人的性能起到了十分重要的支持作用。因为智能阀岛本来就是模块化的设备, 特别是紧凑型CP 阀岛, 它对分散上的集中控制起了十分重要的作用, 特别对机械手中的移动模块。
1.3.3无给油化
　　　为了适应食品、医药、生物工程、电子、纺织、精密仪器等行业的无污染要求, 不加润滑脂的不供油润滑元件已经问世。随着材料技术的进步, 新型材料(如烧结金属石墨材料) 的出现, 构造特殊、用自润滑材料制造的无润滑元件, 不仅节省润滑油、不污染环境, 而且系统简单、摩擦性能稳定、成本低、寿命长。
1.3.4 机电气一体化
　　　由“可编程序控制器-传感器-气动元件”组成的典型的控制系统仍然是自动化技术的重要方面;发展与电子技术相结合的自适应控制气动元件, 使气动技术从“开关控制” 进入到高精度的“ 反馈控制”; 省配线的复合集成系统, 不仅减少配线、配管和元件, 而且拆装简单, 大大提高了系统的可靠性。
　　　而今, 电磁阀的线圈功率越来越小, 而PLC 的输出功率在增大, 由PLC直接控制线圈变得越来越可能。气动机械手、气动控制越来越离不开PLC, 而阀岛技术的发展, 又使PLC 在气动机械手、气动控制中变得更加得心应手。
1.4 机械手夹持部件结构示意图
1.4.1 外夹持型机械手
　　　图1-2为一种较简单平行开闭手爪的结构。气缸的活塞有压缩空气驱动，通过活塞杆7上的支点轴2带动拨叉3转动，再通过传动轴4使手爪1沿导向槽做平行移动，图中为双作用气缸，也可为单作用气缸返回运动靠弹簧完成。该结构的特点是重量轻，体积小，最小型重量为75g，最大型为300g，因此，可以与小型机械手配套使用。

内容简介：: Compliance effects in a parallel jaw gripperA.J.G. Nuttall, A.J. Klein Breteler*Faculty of Design, Construction and Production, Department of Transportation Technology, University of TechnologyDelft, Mekelweg 2, 2628 CD Delft, The NetherlandsReceived 17 April 2002; received in revised form 24 April 2003; accepted 30 June 2003AbstractThis paper discusses mechanical compliance effects in a gripper with parallel jaws. In it a case study of adedicated gripper design is presented to analyse two different design elements influencing the compliantbehaviour: the flexibility introduced by preloaded springs and the resistance caused by friction.The gripper manipulates semi-automatic twistlocks used for securing seagoing cargo containers. Thecompliance effects are effective to reduce misalignment and overload of the gripper.? 2003 Elsevier Ltd. All rights reserved.Keywords: Mechanical compliance; Twistlock manipulator; Preloaded springs; Friction force1. IntroductionRobots grasp and manipulate objects with the aid of a gripper. Usually the object is presentedat a predefined pickup location where the robot can grasp and move it to another predefinedlocation.Difficulties arise when the pickup location and destination are part of a heavy rigid body thatcan move due to external disturbances. If the robot cannot adapt to this movement during pickupor release, the full force of the movement will be transferred into the robot?s components, whichcan result in damage. Therefore the robot should be flexible or compliant where the environmentis stiff3.Compliance can be introduced to the robot by using a compliant end-effector or gripper. Thiscan be done in different ways. In literature a variety of subjects on gripper compliance canbe found 1,3,4, these are mainly focussed on control theories for universal grippers and fine*Corresponding author. Tel.: +31-15-278-3130; fax: +31-15-278-1397.E-mail address: a.j.kleinbretelerwbmt.tudelft.nl (A.J. Klein Breteler).0094-114X/$ - see front matter ? 2003 Elsevier Ltd. All rights reserved.doi:10.1016/S0094-114X(03)00100-9Mechanism and Machine Theory 38 (2003) 15091522/locate/mechmtmanipulation. In 5,6 such a compliance is investigated using stiffness models and in 7 a remotecompliance centre is introduced. These investigations integrate compliance into the control sys-tem, with the aid of special sensors and actuators making reliable force and position controlpossible. With this form of electronic control the universal gripper can manage many differenttasks and objects.This is in contrast to the special-purpose end-effector that is to be designed for a specific taskand object. By making use of simple sensors and actuators combined with a mechanical form ofcompliance an effective, reliable and robust gripper can result, which will also be able to adapt (allbe it in a limited manner) to a moving pickup point. The adaptation of this form of compliance forgripper configurations has proven hard to find in literature.This paper gives an insight into the effects of mechanical compliance in a gripper. A case studyof a gripper design will aid as example to discuss two different modes of mechanical compliance.This example case consists of a parallel jaw gripper configuration intended for the manipulationof semi-automatic twistlocks.2. Background to the twistlock manipulatorA manipulator was required to automatically connect and remove semi-automatic twistlocks toand from a container?s bottom corner castings. In Fig. 1 a semi-automatic twistlock is shown onthe left. This type of twistlock is a lashing device that is used to secure sea-going cargo containersto the deck of a ship. It consists of a body, an upper and lower rotating cone and a handle formanual operation of the cone positions.The upper cone can be inserted into the bottom corner casting depicted on the right side of Fig.1 by unlocking it through rotating the lower cone. The top collar fixes into the hole of the cornercasting, because it matches the shape of the hole. When the cones are rotated back to their originalposition, the twistlock is secured to the bottom corner casting. The handle is intended for manualoperation. If it is pulled the shaft rotates that connects the cones together.Fig. 1. A semi-automatic twistlock and a corner casting of a container.1510A.J.G. Nuttall, A.J. Klein Breteler / Mechanism and Machine Theory 38 (2003) 15091522For automation of this securing procedure and the reverse operation a gripper had to be de-signed that can hold different types of twistlocks by their collars with sufficient grasping force 10.The jaws also have to open far enough, to prevent collisions with the cones while the manipulatoris positioning over the twistlock with open jaws.The container can move during the pickup or release operation due to external disturbances,because it will be hoisted up in the air by cables or resting on a rolling chassis with pneumatictyres. The wind is an example of a disturbance that can generate fluctuating forces on the side ofthe container, which can result in an oscillating movement. Due to the possible movement of thelarge container mass (30 ton) and the robust construction of the twistlock the gripper will have tobe compliant to prevent damage to itself or other components of the robot. Mechanical com-pliance will also help tackle the problem of the moving pickup point on the container and keep therequired control system simple.The collar was chosen as contact surface for the gripper, because it is the common element indifferent twistlock designs. It has to fit into the standardised hole of the corner casting, so theshape and size will be roughly the same. Although the width of the hole is only allowed a toleranceof 1.5 mm the collar widths found in practice can vary between 57 and 62 mm. This 5 mm range incollar sizes had to be taken into account for a reliable operation of the gripper.In Fig. 2a the forces applied by the jaws during a grasp are presented. The frictional forcesgenerated on the collar sides will have to be sufficiently large to compensate the static and dy-namic forces created on the twistlock. The total force (Ftot) that has to be compensated in a di-rection parallel to the collar surface is 200 N. This was calculated by determining the dynamicforces caused by movement of the manipulator and the static gravitational force. With a fric-tional coefficient (l) of 0.125 the grasping force exerted by each jaw (Fjaw) can be calculated asfollows:Ftot 2 ? lFjaw) FjawFtot2l 800 NThis is the minimal force that has to be guaranteed during the manipulation of a twistlock, for allcollar sizes.Fig. 2b shows the open and closed position of the jaws. It shows how far the jaws have to open,during the positioning of the open gripper. There has to be enough clearance between the coneFig. 2. Grasping forces on twistlock and the required jaw travel.A.J.G. Nuttall, A.J. Klein Breteler / Mechanism and Machine Theory 38 (2003) 150915221511and jaw to prevent a collision, because the cone diameter is larger then the collar width. To get aclearance of 15 mm the displacement of a jaw has to be 40 mm.3. Finding a suitable gripper configurationAn existing gripper that is capable of producing a rather large clamping force and large dis-placement is illustrated in Fig. 3a 2. It consists of two parallel jaws, actuated by a double actingpneumatic cylinder. Attached to the cylinder?s piston rod is a dual rack gear, which drives twopartial sectors of pinion gears. Two pairs of the symmetrical arranged parallel closing linkages aremounted directly on the partial sectors of the pinions and provide the clamping force.This design only features compliant behaviour with respect to the width of the grasped object.If the grasped object is larger then the distance between the closed jaws, they will come in contactwith the object before they are fully closed. Therefore the piston will not travel to its end positionduring this closing operation. This makes it possible to grasp different sized objects. It willhowever be more difficult to sense the closed position of the jaws. A special sensing method likeforce detection will be required to measure the closed position.The gripper configuration of Fig. 3a can be given additional compliance as shown in Fig. 3b.Preloaded springs have been added to the jaws, to get compliant behaviour in the horizontaldirection. Preloading the springs gives two advantages. First of all the stroke required to build upsufficient grasping force can be short. If the preload is set to the minimal required grasping force,after contact with the object the springs hardly need any travel for a secure grip. Secondly theminimal required grasping force can be guaranteed with the aid of a proximity sensor that candetect the end position of the pneumatic cylinder. If the cylinder reaches the end of the closingstroke with an object between the jaws, the springs will have been pressed in and the graspingforce would at least have to be equal to the set preload.Fig. 3. Parallel gripper configurations with compliance.1512A.J.G. Nuttall, A.J. Klein Breteler / Mechanism and Machine Theory 38 (2003) 15091522This gripper design with springs in the jaws was not used for the twistlock manipulator, becausethe springs take up too much space. Special measures would have to be taken to keep the jawconstruction sufficiently compact.An alternative configuration with spring elements can be seen in Fig. 3c. The preloaded springsare not directly connected to the jaws, but they have been placed between the actuator and thelever of the jaw parallelograms. The mechanism amplifies the force of the cylinder, when the jawsare closing, if the springs would have been ordinary bars. The generated grasping force is largestwhen the jaws are nearly closed. The more they are opened the smaller the possible force, but thelarger their displacement versus the cylinder displacement.In this configuration another effect is introduced with respect to compliant behaviour. If ahorizontal force is applied, a resistance is generated by friction in the contact surfaces. Thehorizontal force has to be large enough to overcome this resistance and to move the jaws with theobject in between.The cause of this effect is illustrated in Fig. 3d. When the grasped object moves to the right theleft jaw swings up and the right jaw swings to a lower position while they both remain parallel toeach other. This causes the jaws to slide over the surface and generate frictional forces if thegrasped object does not change orientation. In the example case the object or twistlock will notchange orientation, because it is fixed to the container during the grasping manoeuvre. It can onlymove with the container in the horizontal direction.The design in Fig. 3c will be considered further for the twistlock manipulator and will beanalysed using the theory given below.4. Modeling the gripper, FEM approachWhen the frictional compliancy is in effect, the jaws will slip relatively to the twistlock surface.The friction forces under slip will be considered proportional to the contact force. This is areasonable assumption for the conceptual design phase of the gripper.The theory needed concerns just the equilibrium of static forces, as for instance can be de-scribed with the principle of virtual work. The spring forces and the friction in the grippermechanism are considered as internal forces. Their virtual work must be equal to the virtual workof the compliant force, which is considered as the driving force.To perform the actual calculations, a general computer program for kinematic and dynamicanalysis can be used in which this theory has been embedded. The portion of the theory used toperform the analysis calculations, is described below briefly. The theory is also known as finiteelement approach 8,9.From FEM the two maps displacements on deformations, and applied forces on internal forcesare known as dual maps, indicating that both relations can be described with the same matrix.Here it means that the contact forces of the jaws (internal forces) will be calculated with the samematrix as used for kinematic motion analysis.A.J.G. Nuttall, A.J. Klein Breteler / Mechanism and Machine Theory 38 (2003) 150915221513A model of the gripper mechanism can be built with truss elements each having constant length.In the FEM-concept a constant length is considered to have deformation zero. For kinematicsit concerns just a mathematical variation of the length, for force analysis a normal force exists asan internal force.The length itself is a continuous function of global co-ordinates (position vector x) of the el-ement. For a truss element, defined by the end-points P and Q and numbered k, the continuityequation can be written asxk jxPyPxQyQjTkxk ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiyQ? yP2 xQ? xP2q1Moving with deformation zero can be expressed in kinematics with a continuity equation of thefirst order, like here for constant lengthokoxk?T?oxkok? 12Written out with the help of (1)?cosbk?sinbkcosbksinbk?oxkok? 13where b is the angle of the element that can be obtained from the given xkvector.Comparable continuity equations can be constructed to prescribe a fixed angle of the trusselement or a fixed angle w between two truss elements.Those partial derivatives concerning fixed nodes are known (zero); those concerning movingnodes are the unknowns in a linear system of first order continuity equations. In a correctmechanism model there are as many equations (prescribed deformations, vector ep) as unknownpartial derivatives (the total amount of co-ordinates of moving nodes, vector xc). Following theFEM-approach the mechanism input is also to be modelled as a prescribed deformation. In thegripper mechanism this concerns the elongation of the pneumatic cylinder.To calculate all unknown partial derivatives, co-ordinates with respect to deformations, thematrix called Dc(the known coefficients of the first order continuity equations) can be invertedoxcoep? Dc?14and this determines implicitly the kinematic transfer function of first order as one column (ormore columnsin case of a multiple DOF mechanism) of the inverse of matrix Dc.Applied forces (vector fc) can be exerted at the co-ordinates. Their amount of virtual work willbe consumed by the internal forces (vector rp), which should be regarded as multipliers for theprescribed deformations. This equilibrium condition yieldsrp DcT?1? fc5known in the FEM for stress analysis of statically determined structures. Eqs. (4) and (5) showclearly the dual use of the maps: the matrix Dccan be used both for position analysis and for force1514A.J.G. Nuttall, A.J. Klein Breteler / Mechanism and Machine Theory 38 (2003) 15091522analysis. The deformation modelled for input has a corresponding r, which is then the drivingforce. As with a pneumatic cylinder, this force should be interpreted either as tensile or com-pressive force.Position analysis of the mechanism needs a numerical procedure with prediction and correctionof the co-ordinate values. Starting at a given position (all co-ordinate values given), the input canbe incremented (given a finite deformation), which can iteratively be reduced to zero to find theneighbouring position. The Newton/Rapson method is suited because the required partial de-rivatives are available.A spring element, in the form of a coil spring, can be modelled using the continuity equation forthe length of a truss element. Now the internal normal force rkis to be given as a function of thelength, which means a spring characteristic must be known. Length of this spring element shouldnot be prescribed, but can be calculated in the known mechanism position. This spring force canbe converted to applied forces at the connection points, using (3)fkokoxk? rk6The theory given above is available in a computer program 11, which has been used for theinvestigations.5. Force amplification on the driving cylinderThe driving concept assumes a fixed stroke of the pneumatic cylinder. If the end position can bedetected with a simple on/offswitch the required contact forces between jaws and twistlock can beguaranteed by (preloaded) springs.The jaws need a relatively wide opening (see Fig. 2b) and a high force at the end of the stroke tohold the twistlock. This combination tends to both a large cylinder diameter and a large stroke.Force amplification, such that the high forces apply only when needed, can reduce the cylinderdiameter. This is advantageous for space occupation of the moving end-effector. Not just thediameter, but also the overall length decreases because the piston length, bearing and end cap areshorter. A second advantage is the decreased volume of the air supply.To investigate the force amplification, mainly intended to help to choose the driving cylinder, anumerical experiment has been performed. Having in mind the mechanism of Fig. 3c and springsat the jaws (like in Fig. 3b), the whole subsystem of the two springs and the twistlock can bereplaced by one spring (see Fig. 4). With d as the width of the twistlock the spring characteristiccould be chosen as follows: Length greater than d 22 mm (11 mm clearance at both sides): the applied forces are zero. From d 22 to d 20 mm the applied forces build up to 400 N (the preload). From d 20 to d mm the applied forces increase linearly to 800 N.The closing motion including force analysis according the FEM-theory has been performedusing the mechanism model in Fig. 4. Some trials have been made before the final dimensions ofthe gripper mechanism were chosen. The spring force at the jaws and the driving force of theA.J.G. Nuttall, A.J. Klein Breteler / Mechanism and Machine Theory 38 (2003) 150915221515cylinder have been depicted in Fig. 5 for the largest and the smallest width of the twistlock. Thegraphs have been marked with DRIVE_57 (driving force for collar width d 57 mm) andGRASP_57 (contact force for collar width d 57 mm) etc. Apparently a driving force of about500 N is sufficient to fully compress the spring being responsible for the grasping force of 800 N.Assuming that a standard air pressure of 6 bar is available, the information obtained from thisinvestigation is sufficient to choose a cylinder diameter.6. Construction of the gripperThe gripper includes a device to rotate the cones of the twistlock while it is being grasped. Therotation device needs to occupy some space between the gripper links. Therefore it is advantageousFig. 4. Mechanism model for motion and force analysis.Fig. 5. Driving force and grasping force.1516A.J.G. Nuttall, A.J. Klein Breteler / Mechanism and Machine Theory 38 (2003) 15091522to apply two identical gripper mechanisms, at parallel planes aside the rotation device, which canbe connected by the jaws (see Fig. 6, the rotation device and the frame are left out this figure).Now it is natural to use driving cylinders for each of the two parallel mechanisms. These twocylinders together will produce the total driving force. This embodiment avoids space conflictswith other driving elements of the gripper. The overall length of these smaller cylinders can bedecreased again and will reduce space conflicts with the gripper?s surroundings.The experiment of the previous section has also provided the normal forces in the connectionbars numbered 1 and 2 in Fig. 4. These bars have been selected to act in reality as the preloadedsprings, with the intention to generate grasping forces comparable with those presented in Fig. 5.It was decided to choose the following spring characteristic for the two bars (l0is the preloadedbut free length): Length l0 1 mm: spring force zero (actually loss of contact). Length from l0 1 mm to l0: building up to 80% of the preload. Length from l0to l0? 2 mm: building up linearly to 100%. This part determines the actualspring constant. Shorter length will numerically be accepted (no matter the technical realization of the spring).7. Compliance investigationsThe situation where the twistlock is grasped will be investigated with respect to side forces, aswould be caused by the oscillating container. Wrenching is left out the investigations. Since theFig. 6. Embodiment of the gripper mechanism.A.J.G. Nuttall, A.J. Klein Breteler / Mechanism and Machine Theory 38 (2003) 150915221517gripper contains two identical mechanisms in parallel planes, only one of these mechanisms needsto be considered further. The driving force and the forces at the twistlocks are thus less by half.The driving cylinder of the mechanism is completely out, and one end-point of each springmay be considered as a fixed point. The model of this mechanism is depicted in Fig. 7.7.1. Investigation 1: compliance without frictionThis situation occurs typically for flat objects, which can easily have friction coefficients higherthan b=d (the ratio of height and width of the grasping object, here the collar of the twistlock).The twistlock will tumble slightly and no slip occurs. The twistlock can be modelled as a simplebar, which is connected with pin-joints to the jaws (Fig. 7).The symmetry axis of the twistlock will be moved from left to right over a distance of 20 mm(from )10 to +10 mm). The force required for this movement, the driving force should be re-garded as resistance force. The stiffness is the reverse of the compliance. The result of the FEMbased analysis is presented in Fig. 8. It clearly shows that the resistance force grows suddenlywhen one of the jaws looses contact, and then proceeds with a lower stiffness because only one ofthe springs is active. This type of behaviour is typical for grippers with preloaded springs. It can beremarked further: The sudden jump is advantageous because it can consume extra energy during overload. In the case of twistlock removal the gripper is upside down. The twistlock does not directly fallout of the gripper when one of the jaws looses contact. The force characteristic is not precisely symmetrical to the origin. The two springs are the sameindeed, but the link chains left and right are not. They therefore do not equally contribute tothe resistance force. If this matters, the l0of both springs could be given unequal values. A small width seems to have little compliance. There is however more clearance between twist-lock and corner casting of the container.Fig. 7. Mechanism model for compliance investigation.1518A.J.G. Nuttall, A.J. Klein Breteler / Mechanism and Machine Theory 38 (2003) 15091522A rough conclusion is that this gripper arrangement can function properly even with a mis-alignment of 3 mm. Dynamic overload protection can be much larger, but depends on thetechnical properties of the spring, like the minimum compressive length.7.2. Investigation 2: compliance with frictionIt will be assumed that the twistlock slips along the parallel jaws. This happens not only forrectangular objects that have a high value for b=d, but also when the object has a fixed orien-tation. The latter situation applies certainly when the twistlock is still in the corner casting of thecontainer. The model of the mechanism may be changed like in Fig. 7, alternative twistlockmodel.The symmetry axis of the twistlock will be moved from left to right and then back to the left,with the same displacement as in the previous experiment. Because the software available for themotion and force analysis does not yet support friction forces, the friction needs to be added in apost-processing action to obtain the driving forces with friction. This can be done as follows.Suppose F0is the driving force without friction in the mechanism model of Fig. 7. The contactforces at the left-hand and the right-hand jaw appear in the FEM approach as internal forces(normal forces) called further rLand rR.With s as the slip and l as the friction coefficient, the slip forces rw, which are of course re-garded as internal forces, can be expressed asrwL sign_ s sL ? lL? jrLjrwR sign_ s sR ? lR? jrRj7Fig. 8. Compliance without friction.A.J.G. Nuttall, A.J. Klein Breteler / Mechanism and Machine Theory 38 (2003) 150915221519They contribute to the driving force, acting along displacement direction x, in accordance with thebalance of virtual workDF rwLdsLdx rwRdsRdx8The friction influences not only the driving force, but also the internal forces, and among themthe normal forces at the jaws. The friction equations (7) can be substituted into equation system(5) for rp, but this system will then become non-linear. This could be solved into the programitself, but not in a post-processing phase.For this purpose of investigation the normal forces can be estimated with the result of theprevious mechanism position. The horizontal force equilibrium of the twistlock in position i issatisfied accurate enough byrLi r0Li DFi?1andrRi r0Ri? DFi?19where r0indicates the normal force without friction.The driving force F F0 DF has been calculated for a width d 60 mm of the twistlock, fora range of friction coefficients l. The result has been depicted in Fig. 9. A hysteresis loop, which istypical for the friction effect, is clearly present. This effect is advantageous because of reasons like it helps to suppress the container oscillations, although the effect is probably small; it can prevent the system of the gripper holding a twistlock to oscillate; and It provides some initial resistance force against side movements of the twistlock. In this partic-Fig. 9. Compliance with friction.1520A.J.G. Nuttall, A.J. Klein Breteler / Mechanism and Machine Theory 38 (2003) 15091522ular case the gripper must place the twistlock upside down in a storage position. Halfway thismanipulation task the symmetry axis will be horizontal. From the picture it can be concludedthat a twistlock with a mass of 8 kg will not slip due to gravity forces if the friction coefficientl 0:3 or more.It can be concluded that friction is not only required to hold an object between parallel jaws,but it can also provide extra resistance against side forces. This compliance effect is extra to theelastic compliance of built-in preloaded springs and depends on the friction coefficient and thefirst order kinematic slip. The latter is a property of the gripper configuration, which could bedesigned with respect to the mentioned effect.8. Experimental verificationAn experimental twistlock manipulator was built using the described gripper configuration(Fig. 6) and it was tested for different types of twistlocks. During the test the manipulator proveditself, being capable of a secure and reliable grip using a simple sensing and control system.Tests were also done to give an indication of the gripper compliance. For these tests the pre-cision was measured with which the gripper has to be positioned at the pickup or release point fora problem free manipulation. Before the manipulator was given the command to get or put away atwistlock the position of the corner casting was moved from the predefined position with a staticoffset. The maximum amount of static offset was measured that would still allow a problem freemanipulation. The result for two twistlocks with different collar widths (59.5 and 62 mm) is twistlock 1 (collar width59.5 mm), maximum offset: 7 mm; twistlock 2 (collar w

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