CHAPTER 1 INTRODUCTION

Transcription

1 CHAPTER 1 INTRODUCTION Grasping and fine manipulation with the multi- finger robotics hands are playing an important role in manufacturing and other applications that require precision and dexterity. Nowadays, most of robotics hand with multi-fingered are used as service robot, human friendly robot and personal robotics. A robot hand is defined as that can mimics the movements of human hands in operation. The project is related with the Data analysis on robotics hand through CAD/FEA in order to grasp objects. Research and development of robotics hand is the main focus of the projects. The multi-finger robotics hand performs like real human hands. That is it follows the same kinematics and mechanisms that a human hands do. Basically, the multi fingered robotics hand of our project is used to grasp objects. Thus, it can be success to maintain its own strategy in various fields. The challenging thing is to develop multi-finger robot, in order to get the precise and accurate grasp of the robotic hand. It is approximate the versatility and sensitivity of the human hand. Nowadays there are various types of robotics hand and its application. The most important aspects to be considered are their stability, reliability and economically. Main parts are a characteristic of robot hand is not the same as human. All of robot hand mechanism totally related to the cost. Simplifying the robot mechanism with less cost which is similar to human is most challenging task.

2 CHAPTER 2 LITERATURE REVIEW Robotics technology moves forward until now. The technology developments since 70 s era until now are rapidly changing the robotic hand engineering history. Existing hand now can divide into four types which are; 2.1 Robot hands of 80 s: a. Robot hands of 80 s b. Commercial hands c. Research hands d. Prosthetics hands. Development of robot hands early 80 s start with, Soft gripper Hirose Soft Gripper by Shigeo Hirose from Tokyo Inst. Technology. This development began late 70 s with 1 DOF when it graduated pulleys at joints and create evenly distributed forces. In the same era, more development and research done for this field to upgrade the prototypes and technologies. For example Stanford/JPL hand in Figure1 prototype with nine DOF designed. Others feature such as four tendons or finger also designed for fingertip manipulation is combined with strain gauge fingertip sensors. Figure 2.1: Stanford/JPL hand

3 2.2 Commercial hands: Hence the research and development in this disciplined increased and move towards, more of prototypes being commercialize being robotic hand products due to highly demand in industries or another platform also commercialize. Barrett hand from Barrett Technology Incorporated used 4 motors, one motor per finger for three finger and plus another spread motor for palm. The breakaway technology allows fingers to adapt to object geometry. It s also including the optical encoder for position sensing. This hand capability to maintain up to 3.3 lb. fingertip force and the weight of this hands about 1.18 kg. Finally, this commercial hand sells about 30K US Dollar. Another commercial hand is DLR / HIT hand in Figure 2 developed by Gerhard Hirzinger, This hand sold by Schunk Company about USD 60K. This hand larger than human size which is capability to maintain up to 1.5 lb. fingertip force with Hall Effect sensors and the weight of this hand about 2.2 kg. It has 13 controlled DOF (last two joints of each finger are coupled). Figure 2.2: DLR/HIT hand 2.3 Research hands: Finally, ACT hand by Y. Matsuoka from University of Washington developed shown in Figure 3 with three fully actuated fingers with human musculoskeletal structure (redundant actuation). This research hand goal is for study human control of hand movements because this hand passive and active dynamics consistent with human hand.

4 Figure 2.3: ACT hand 2.4 Prosthetic hands: Prosthetic hands are ilimb (Touch Bionics) in Figure 4 and Cyber hand in Figure 5. All of that used in order to help people who need it and commercialized too. ilimbs is about USD 18K. There are more than 250 people uses this hand. There are 5 motors driven from single muscle signal and thumb preshape for power, precision and key grip. Motors stall individually for adaptive pose by option. Prosthetic hand by Maria Carozza called Cyberhand from Scoula Superiore Sant Anna. It has 6 motors controlled 16 joint with cable driven. Multisensors used such as position, cable force, fingertip force and tactile array sensor. It mounts with 3.3 lb. fingertip force, closes in 3 seconds and 0.45kg weight only which is not including forearm motors. Finally, DEKA Dean Kamen are the prosthetic hand from the DARPA, Revolutionizing Prosthetics Program and others under development of (JHU/APL, RIC, Otto Bock) Figure 2.4: ilimb

5 Figure 2.5: Cyber Hand

6 CHAPTER 3 RESEARCH WORK We are in 21 st era, the era which is filled with advanced technology as to make human lifestyle comfort and reliable. Advanced innovation and invention are in increasing order. Similarly, robots are one of the most advanced technologies that are prevailing in the existing world. Robotics technology nowadays moves forward until now. Thus, we have studied about the existing robots with fingers. It is briefly described below. 3.1 Current Prosthetic Hands: Common Prosthetic Hands: There are commonly available prosthetic hands which offer very limited and simple functionality. All of these hands offer one action, opening or closing. They generally have a very blocky 13 appearance, and often have 3 fingers instead of 5. The simple hands were easier to design and build, but cannot perform many tasks required of the user. Fig 3.1: VASI Hand Family (Technologies, Liberating,2012) Fig 3.2: Mech Hands (Technologies, Liberating, 2012)

7 3.1.2 Michelangelo Hand: The Michelangelo Hand built by Advanced Arm Dynamics is simply the most advanced hand on the market today. It actually has the powered opposable thumb, the first one released as an actual product. Sadly, the arm costs $100,000, so it is unable to be purchased, and difficult for even insurance companies to pay for. (Pittman, 2012) The hand is incredibly well refined and streamlined in execution. Fig 3.3: Michelangelo hand Myoelectric Sensors: Myoelectric sensors are the most commonly used control method with advanced robotic prosthetic hands. (Dailami, 2002) These sensors would be an excellent way of controlling this hand, but they would have to not use a proprietary signal protocol. The hand would need to be programmed to accept serial communication from the sensors. Additionally, one of the main goals of this project was to create a simple and low cost system, and the myoelectric sensors could add a tremendous amount of cost and training with many customization visits with a prosthetist. Fig 3.4 Myoelectric Control Example (Phillipe, 2012)

8 3.1.4 Kickstart Robotic Hand: Christopher Chappell of the UK created a Kickstarter for a 3Dprinted robotic hand that is a little bit more sophisticated than the other Robohand. As per him, the campaign is to develop a humanoid robotic hand and arm that is of far lower cost than any other available. Features of hand: 6 degrees of freedom that can be actuated (1 thumb, 4 fingers and 1 wrist). The thumb has another degree of freedom that can be set manually The arm uses a tendon system, with the movement being provided by 5 Hobby Servos. 5 being the current number that can fit into the forearm Small elastic bands allow the joints to open and close smoothly Easy assembly and repair. All parts can be removed and fixed, should the need arise Off the shelf electronics. The arm uses arduinos and commercial servo drivers Free software. The software to control the hand will be posted online. This will allow control via PC, as well as other inputs (e.g., control glove, EEG etc.). The source code will be open so that you can create your own control systems. Fig 3.5: Kickstart robotic hand Shadow Hand: The Shadow Dexterous Hand is a humaniform robot hand system developed by The Shadow Robot Company in London. The hand is comparable to a human hand in size and shape, and reproduces all of its degrees of freedom. The Hand is commercially available in Pneumatic and Electric actuated models and currently used in a The Shadow Dexterous Hand has been designed to have a range of movement equivalent to that of a typical human being.

9 The four fingers of the hand contain two one-axis joints connecting the distal phalanx, middle phalanx and proximal phalanx and one universal joint connecting the finger to the metacarpal. The little finger has an extra one-axis joint on the metacarpal to provide the Hand with a palm curl movement. The thumb contains one one-axis joint connecting the distal phalanx to the proximal phalanx, one universal joint connecting the thumb to the metacarpal and one one-axis joint on the bottom of the metacarpal to provide a palm curl movement. The wrist contains two joints, providing flex/extend and adduct/abduct.

10 CHAPTER 4 DESIGN & MODELING 4.1 DESIGN CONCEPTS: Basically, the design is associated with the real human hands. The human hand has been cited as an important limb that developed the ability of the human brain to form the essential activities in life. The nerves trigger the muscle to generate force. Two sets of muscle act on the hand; extrinsic located in the forearm which is less powerful while the intrinsic that is located within the hand itself is much stronger. Most of the dexterity and flexibility of the hand is attributed by the intrinsic muscle. Some of the muscles act directly on the bones while others act through tendons. Flexor is used to close fingers to grip object and the extensors are used to open the hand again A hand is supported by a lot of bones that provide movement to each parts of the hand from the fingertips to the elbow. The human hand can perform all the necessary type of grasping. A human hand with twenty five degree of freedom is very flexible and versatile. The basic types of hand grasping are cylindrical, tip, hook or snap, palmer, spherical and lateral or key pinch grasp shown in Figure. Fig 4.1: Grasping Objects by Human Hand 4.2 BASIC COMPONENTS: Design of multi-finger robotics hand through cad is the main goals of ours to achieve. Firstly, the component that has been used is briefly described.

11 The components are: I. Stepper Motor II. Gear III. Servo motors STEPPER MOTOR: A stepper motor (or step motor) is a brushless, electric motor that can divide a full rotation into a large number of steps. The motor's position can be controlled precisely without any feedback mechanism (see Open-loop controller), as long as the motor is carefully sized to the application. Stepper motors are similar to switched reluctance motors (which are very large stepping motors with a reduced pole count, and generally are closed-loop commutated. Here, the used stepper motor acts as one of the main component as it aids the gears to rotate which ultimately results the movement of the fingers through other linkages. Fig 4.2: Stepper Motor The designed stepper motor is shown in the fig below: Fig 4.3: Designed Stepper Motor

12 GEARS: A gear is a rotating machine part having cut teeth, which mesh with another toothed part in order to transmit torque. Two or more gears working in tandem are called a transmission and can produce a mechanical advantage through a gear ratio and thus may be considered a simple machine. Geared devices can change the speed, torque, and direction of a power source. Various types of gears are in used in the manufacturing as well as automotive field. In the robotics hand we had used spur gear. Spur gears or straight-cut gears are the simplest type of gear. They consist of a cylinder or disk with the teeth projecting radially, and although they are not straight-sided in form, the edge of each tooth is straight and aligned parallel to the axis of rotation. These gears can be meshed together correctly only if they are fitted to parallel shafts. Two gears have been used. Drive gear rotates through the power produced by the stepper motor which aids the driven gear to rotate. Thus, the rotation of the gears helps to rotate the shaft mounted. Fig 4.4: Spur Gear Fig 4.5: Designed Gear SERVO MOTORS: A servomotor is a rotary actuator that allows for precise control of angular position. The servo motors usually have a rotation limit from 90 to 180. Some servos also have rotation limit of 360 or more. But servos do not rotate continually. Their rotation is restricted in between the fixed angles. The Servos are used for precision positioning. They are used in robotic arms and legs, sensor scanners and in RC toys like RC helicopter, airplanes and cars. Here, each finger is consists of three servo motors excluding thumb. Thumb has only one servo motor. Thus, the servo motors actuate the fingers i.e. the movement in the fingers are occurring due to the servo motor used.

13 Fig 4.6: Servo Motor Fig 4.7: Designed Servomotor 4.3. CAD MODELING: Similarly, other components of robotics hand have been designed through CAD. Our robotics hand reflects the human hand. So, it has been designed in accordance with the human hands. Likewise, human hands, designed robotics hands have a palm where the five fingers are placed. The five fingers are: a. Index finger b. Middle finger c. Ring finger d. Small finger e. Thumb Let us have a brief description about the five fingers as well as palm designed of the multi-finger robotics hand PALM: The palm is the part of hands where the fingers are associated with. Thus, the fingers of robotics hands are also placed in the palm. The palm is connected with the shaft at one end while the other end is connected with the five fingers. When the shaft gets rotate due to the rotation of the gear, the palm gets movement. Here, the palm rotates as per the rotation of the shaft. As our goal is to grasp any cylindrical object thus, the palm should be rotate with certain angle so as it can gives the movement on finger and become success to grasp the object.

14 Fig 4.8: Designed Palm FINGERS: One single finger was the starting point for the entire design process. The human hand was studied visually while grasping and handling many different objects. Being that the hand consists of four similar fingers and one thumb, it was logical to conclude that the finger design could potentially be replicated four times. This meant that if the size and space requirements to actuate one individual finger proved too large, then another method would be needed. The finger design process began with determining what motion was required for each finger. The human hand was simply viewed gripping various cylindrical objects such as a bottle commonly found in a person s daily routine. The location of the various joints was viewed. The human finger is an amazing piece of engineering consisting of three individual pivot joints which can almost be individually actuated through muscular tendons. The four main fingers can also be spread apart sideways and rolled slightly culminating in an impressively large amount of total degrees of freedom. Fortunately, to perform the majority of common gripping tasks, only a small amount of motion should actually be required. The human finger achieves a conformal adaptive grip by bending the knuckles as an object is grasped. By carefully studying own fingertip, it can be viewed that the final knuckle joint only rotates a small amount. Therefore the first opportunity for simplification comes from treating the fingertip as one fixed link as opposed to two separate links joined by a knuckle. The parts finger was carefully observed and CAD model was produced in the profile of a palm. As previously described, the fingertip was treated as one link with the final knuckle fixed slightly bent. An assembly was created in CAD which allowed for the motion of the two joints to be studied.

15 KINEMATICS ARCHITECTURE: The kinematics of each finger joint is described in the following subsections. MP Joint: The proximal actuator is integrated in the palm and transmits the movement through a slider-crank mechanism the proximal phalange providing flexion/extension movement. The slider is driven by the lead screw transmission directly mounted on the motor shaft. PIP joint: The same mechanism used for the MP moves the PIP joint. Only the geometrical features are varied in order to fit within the space available according to the specifications of the biomechatronic hand. High friction forces occur, during the mechanism movement, because of low pitch of the threaded shafts.. DIP joint: Four bars link has been adopted for the DIP joint and its geometrical features have been designed in order to reproduce as closely as possible natural DIP joint flexion. Fig: 4.9: Various Joints FINGER LINKAGE MODELING: After the design of palm has been completed, the design of finger was to be done. We had design the index finger at first. The index finger consists of three joints likely as human fingers. Different components of the fingers were designed individually and were finally assembled. After completing the design of the index finger assembly, other remaining fingers were designed similarly. Then the fingers were finally assembled in the profile to the palm.

16 When looking at the finger motion in the assembly, a link was added joining the palm or base of the hand to the final fingertip. As the first joint of the finger was rotated, linked motion of the fingertip was achieved. The location of the linkage pin holes was kept at a constant radius from the points of rotation. By maximizing this distance, the link would be under the least possible amount of stress and help reduce backlash in the final product. The angle of the linkage pin holes was a variable, as well as the length of the link itself. All of those variables were constantly adjusted until the desired visual motion was achieved. By moving the first finger joint through, the fingertip was also moved in relative to the first joint. The motion appeared smooth and relatively constant throughout the range of motion. The motion was verified by moving the assembly in CAD DESIGN ASSEMBLY OF FINGERS: Index Finger Assembly: Fig 4.10: Index Finger Assembly

17 Middle Finger Assembly: Fig 4.11: Middle Finger Assembly Ring Finger Assembly: Fig 4.12: Ring Finger Assembly Small Finger Assembly: Fig 4.13: small finger assembly

18 Thumb Assembly: Fig 4.14: Thumb Assembly My object for consideration is to grasp the cylindrical objects. Here, we have referred a bottle as a cylindrical object. Thus, the multi finger robotic-arm is grasping the bottle. Let us have a glance on our design bottle. Fig 4.15: Design Bottle

19 4.4 DESIGN ASSEMBLY OF MULTI FINGER ROBOTICS HAND: Fig 4.16: Final Assembly Thus, we have completed the final assembly of our multi finger-robotic hand. The above shown figure reflects the final assembly that we have done through CAD. POSITION OF HAND: Fig 4.17: Initial Position Fig 4.18: Final Position

20 CHAPTER 5 ANALYSIS & OPTIMIZATION For analysis of the each components we are used the CATIA CAD software. Initially, we tried to do stress analysis of each parts of the arms, like we are started with index finger, then thumb tip, etc. 5.1 ANALYSIS OF INDEX FINGER: Consider Normal Load on Clamp: 500N Analysis Result Output By CATIA: MESH: Entity Size Nodes 4013 Elements ELEMENT TYPE: Connectivity Statistics TE ( % ) ELEMENT QUALITY: Criterion Good Poor Bad Worst Average Distortion (deg) ( 70.51% ) 3857 ( 26.15% ) 493 ( 3.34% ) Stretch ( % ) 0 ( 0.00% ) 0 ( 0.00% ) Length Ratio ( % ) 0 ( 0.00% ) 0 ( 0.00% )

21 Materials 1ist Material Young's modulus Steel 2e+011N_m2 Poisson's ratio Density 7860kg_m3 Coefficient of thermal expansion 1.17e-005_Kdeg Yield strength 2.5e+008N_m2 STATIC CASE: Boundary Conditions Fig. 5.1: Index Finger in Loading Condition Structure Computation Number of nodes : 4013 Number of elements : Number of D.O.F. : Number of Contact relations : 0 Number of Kinematic relations : 0 Linear tetrahedron : 14751

22 RESTRAINT Computation Name: RestraintSet.1 Number of S.P.C: 171 LOAD Computation Name: uniform distributed load Applied load resulant : Fx = e-009 N Fy = e-009 N Fz = e+002 N Mx = e+002 Nxm My = e+002 Nxm Mz = e-009 Nxm STIFFNESS Computation Number of lines : Number of coefficients : Number of blocks : 1 Maximum number of coefficients per bloc : Total matrix size : Mb SINGULARITY Computation Restraint: RestraintSet.1 Number of local singularities : 0 Number of singularities in translation : 0 Number of singularities in rotation : 0 Generated constraint type : MPC CONSTRAINT Computation

23 Restraint: RestraintSet.1 Number of constraints : 171 Number of coefficients : 0 Number of factorized constraints : 171 Number of coefficients : 0 Number of deferred constraints : 0 FACTORIZED Computation Method : SPARSE Number of factorized degrees : Number of supernodes : 1161 Number of overhead indices : Number of coefficients : Maximum front width : 474 Maximum front size : Size of the factorized matrix (Mb) : Number of blocks : 2 Number of Mflops for factorization : e+002 Number of Mflops for solve : e+000 Minimum relative pivot : e-002 DIRECT METHOD Computation Name: StaticSet.1 Restraint: RestraintSet.1 Load: LoadSet.1 Strain Energy : 5.701e-005 J

24 Equilibrium Components Applied Forces Reactions Residual Relative Magnitude Error Fx (N) e e e e-014 Fy (N) e e e e-014 Fz (N) e e e e-013 Mx (Nxm) e e e e-013 My (Nxm) e e e e-013 Mz (Nxm) e e e e-014 Static Case Solution.1 - Deformed mesh.1 Fig: 5.2: Stress On Index Finger On deformed mesh ---- On boundary ---- Over all the model Static Case Solution.1 - Von Mises stress (nodal values).1

25 3D elements: Components: All Fig: 5.3 Index Finger On deformed mesh ---- On boundary ---- Over all the model Global Sensors Sensor Name Sensor Value Energy 5.701e-005J NOTE: All the rest finger are having approximant same dimension, so analysis will be same for that.

26 5.2. THUMB TIP ANALYSIS: MESH: Entity Size Nodes 1396 Elements 4305 ELEMENT TYPE: Connectivity Statistics TE ( % ) ELEMENT QUALITY: Criterion Good Poor Bad Worst Average Distortion (deg) 3299 ( 76.63% ) 944 ( 21.93% ) 62 ( 1.44% ) Stretch 4305 ( % ) 0 ( 0.00% ) 0 ( 0.00% ) Length Ratio 4305 ( % ) 0 ( 0.00% ) 0 ( 0.00% ) Materials.1 Material Young's modulus Steel 2e+011N_m2 Poisson's ratio Density 7860kg_m3 Coefficient of thermal expansion 1.17e-005_Kdeg Yield strength 2.5e+008N_m2 STATIC CASE:

27 Boundary Conditions Fig: 5.4: Thumb In Load Condition STRUCTURE Computation Number of nodes : 1396 Number of elements : 4305 Number of D.O.F. : 4188 Number of Contact relations : 0 Number of Kinematic relations : 0 Linear tetrahedron : 4305 RESTRAINT Computation Name: RestraintSet.1 Number of S.P.C : 213 LOAD Computation Name: Loads 500N

28 Applied load resultant : Fx = e-009 N Fy = e-009 N Fz = e+002 N Mx = e+001 Nxm My = e+001 Nxm Mz = e-010 Nxm STIFFNESS Computation Number of lines : 4188 Number of coefficients : Number of blocks : 1 Maximum number of coefficients per bloc : Total matrix size : Mb SINGULARITY Computation Restraint: RestraintSet.1 Number of local singularities : 0 Number of singularities in translation : 0 Number of singularities in rotation : 0 Generated constraint type : MPC CONSTRAINT Computation Restraint: RestraintSet.1 Number of constraints : 213 Number of coefficients : 0 Number of factorized constraints : 213 Number of coefficients : 0 Number of deferred constraints : 0

29 FACTORIZED Computation Method : SPARSE Number of factorized degrees : 3975 Number of supernodes : 620 Number of overhead indices : Number of coefficients : Maximum front width : 219 Maximum front size : Size of the factorized matrix (Mb) : Number of blocks : 1 Number of Mflops for factorization : e+001 Number of Mflops for solve : e+000 Minimum relative pivot : e-002 DIRECT METHOD Computation Name: StaticSet.1 Restraint: RestraintSet.1 Load: LoadSet.1 Strain Energy : 5.627e-004 J Equilibrium Components Applied Forces Reactions Residual Relative Magnitude Error Fx (N) e e e e-014 Fy (N) e e e e-014 Fz (N) e e e e-014 Mx (Nxm) e e e e-015 My (Nxm) e e e e-014

30 Mz (Nxm) e e e e-014 Static Case Solution.1 - Deformed mesh.1 Fig: 5.5: Stress on Thumb Tip On deformed mesh ---- On boundary ---- Over all the model Static Case Solution.1 - Von Mises stress (nodal values).1 3D elements: : Components: : All Fig: 5.6 Thumb Tip On deformed mesh ---- On boundary ---- Over all the model

31 Global Sensors Sensor Name Sensor Value Energy 5.627e-004J Note: Form above we can see our thumb is getting deform in 500N load, so we are redesigning our thumb tip and analyzing data.

32 5.3. RE-ANALYSIS OF THUMB TIP: MESH: Entity Size Nodes 1337 Elements 4107 ELEMENT TYPE: Connectivity Statistics TE ( % ) ELEMENT QUALITY: Criterion Good Poor Bad Worst Average Distortion (deg) 1653 ( 40.25% ) 1038 ( 25.27% ) 1416 ( 34.48% ) Stretch 4099 ( 99.81% ) 8 ( 0.19% ) 0 ( 0.00% ) Length Ratio 4069 ( 99.07% ) 38 ( 0.93% ) 0 ( 0.00% ) Materials.1 Material Young's modulus Steel 2e+011N_m2 Poisson's ratio Density 7860kg_m3 Coefficient of thermal expansion 1.17e-005_Kdeg Yield strength 2.5e+008N_m2

33 STATIC CASE: Boundary Conditions Fig:5.7: Loading Condition On Re-Designed Thumb Tip STRUCTURE Computation Number of nodes : 1337 Number of elements : 4107 Number of D.O.F. : 4011 Number of Contact relations : 0 Number of Kinematic relations : 0 Linear tetrahedron : 4107 RESTRAINT Computation Name: RestraintSet.1 Number of S.P.C : 171

34 LOAD Computation Name: Loads 500N Applied load resultant : Fx = e-010 N Fy = e-008 N Fz = e+002 N Mx = e+001 Nxm My = e+001 Nxm Mz = e-009 Nxm STIFFNESS Computation Number of lines : 4011 Number of coefficients : Number of blocks : 1 Maximum number of coefficients per bloc : Total matrix size : Mb SINGULARITY Computation Restraint: RestraintSet.1 Number of local singularities : 0 Number of singularities in translation : 0 Number of singularities in rotation : 0 Generated constraint type : MPC CONSTRAINT Computation Restraint: RestraintSet.1 Number of constraints : 171 Number of coefficients : 0 Number of factorized constraints : 171 Number of coefficients : 0 Number of deferred constraints : 0

35 FACTORIZED Computation Method : SPARSE Number of factorized degrees : 3840 Number of supernodes : 578 Number of overhead indices : Number of coefficients : Maximum front width : 234 Maximum front size : Size of the factorized matrix (Mb) : Number of blocks : 1 Number of Mflops for factorization : e+001 Number of Mflops for solve : e+000 Minimum relative pivot : e-003 DIRECT METHOD Computation Name: StaticSet.1 Restraint: RestraintSet.1 Load: LoadSet.1 Strain Energy : 7.419e-004 J Equilibrium Components Applied Forces Reactions Residual Relative Magnitude Error Fx (N) e e e e-014 Fy (N) e e e e-014 Fz (N) e e e e-012 Mx (Nxm) e e e e-013 My (Nxm) e e e e-013 Mz (Nxm) e e e e-015

36 Static Case Solution.1 - Deformed mesh.1 Fig: 5.8: Stress In Re-Designed Thumb Tip On deformed mesh ---- On boundary ---- Over all the model Static Case Solution.1 - Von Mises stress (nodal values).1 3D elements: : Components: : All Fig: 5.9: Re-Designed Thumb Tip On deformed mesh ---- On boundary ---- Over all the model Global Sensors Sensor Name Sensor Value Energy 7.419e-004J

37 CHAPTER 6 CONCLUSIONS It helped me to broaden my knowledge while analyzing I found that area is the most important factor for any object. As area is less, stress will be more so we are finding the critical area when stress will be less. Because in mechanical our main aim is to reduce the area. As area increase mass will also increase proportionally. So for reduction in cost we have to take less mass which is suitable for our purpose. While analysis firstly my thumb design got failed and for my purpose it got deform so I redesign my thumb and gave critical area to the thumb.

38 REFERENCES 1. Touch Bionics. (2012). ilimb Features. Retrieved from Touch Bionics: 2. Technologies, Liberating. (2012). Products. Retrieved from Liberating Technologies: 3. Hands Overview Slideshow Slide (2010),: Retreived August 23,2010; from: 4. Ikuo Yamano and Takashi Maeno Five-fingered Robot Hand using Ultrasonic Motors and Elastic Elements IEEE Proceeding International Conference on Robotics and Automation Barcelona, Spain (2005)

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