人类辅助生殖技术规范.ppt

IE458CAMComputer Aided ManufacturingPart-5Robotic Systems,Industrial Engineering DepartmentKing Saud University,Contents,What is an industrial robot?The basic components of a robotPower sources for robotsHydraulic driveElectric drive Pneumatic drive Robot sensorsThe hand of a robot(end-effector)Robot Movement and Precision,The robot jointsRobot classificationPhysical classificationControl classificationRobot reachRobot motion analysis and controlRobot Programming and LanguagesRobot SelectionRobot applicationsRobot Economic,衬塑复合管 涂塑复合管 钢塑复合管 消防涂覆钢管,What is an industrial robot?,The word robot is derived from a satirical fantasy play,Rossums Universal Robots,written by Karel Capek in 1921.In his play,Capek used the word to mean,forced labor.The Robotics Industries Association(RIA),formerly known as the Robotics Institute of America,defines robot in the following way:An industrial robot is a programmable multi-functional manipulator designed to move materials,parts,tools,or special devices through variable programmed motions for the performance of a variety of tasks.,An industrial robot consists of a number of rigid links connected by joints of different types,controlled and monitored by a computer.To a large extent,the physical construction of a robot resembles a human arm.The link assembly mentioned above is connected to the body,which is usually mounted on a base.This link assembly is generally referred to as a robot arm.A wrist is attached to the arm.To facilitate gripping or handling,a hand is attached at the end of the wrist.In robotics terminology,this hand is called an end-effector.The complete motion of the end-effector is accomplished through a series of motions and positions of the links,joints,and wrist.A typical industrial robot with six-degrees of freedom is shown in.,Figure 1,The widespread use of CNC in manufacturing is ideal for the use of industrial robots to perform repetitive tasks.Such tasks may involve handling heavy and sometimes hazardous materials.Sophisticated CNC machining centers can contain palette changers and special interfaces that can easily accommodate industrial robots.,Specialized robots can assist in both assembly and inspection processes.,Material handling robots are used in many industries.It may be surprising to find such robots used even in the fast food industry.,This material handling robot is used in preparing palettes for shipping.Repetitive tasks are ideal to be performed by such machines.,Shown is a Fanuc M-16i Robotic Arm used in a precision grinding process on automotive parts.,Shown is a Fanuc Robot arm lifting three heavy boxes at once.In using robotics,human safety factors in such a task are completely eliminated.This also greatly reduces the risks of repetitive stress injuries to factory workers.,Handling of dangerous materials is an important task for Robots to perform.The size and weight of some automotive parts may be too cumbersome and hazardous for humans to manipulate in certain processes.,Shown is a robotic arm used in conjunction with a small punch press.Together these two machines could comprise a small manufacturing cell.The use of Robotics in such a setup can greatly reduce the chance of human error and injury.,It is now commonplace to find automotive manufacturers using robotics in many phases of the automotive assembly line.Here an automotive spray booth utilizes a Fanuc Robot arm is used to precisely deposit paint on this car body.The use of robotics can improve the quality of certain manufactured goods.,Here a Fanuc S-420W material handling robot is used in the electronic appliances industry.You will note several others in the background used in other steps of the manufacturing process.,Another Fanuc A-510 robot arm used in the food industry.Improved productivity is an important factor in using robotic equipment is repetitive production line operations.It can greatly reduce the human factors which can lead to errors and risk of injury.,Shown are two Fanuch Robot arms employed to perform precision welding tasks.This type of process would be extremely difficult to achieve by humans.,THE BASIC COMPONENTS OF A ROBOTThe basic components of a robot include the manipulator,the controller,and the power supply sources.The types and attributes of these components are discussed next.,Power Sources for Robots An important element of a robot is the drive system.The drive system supplies the power,which enables the robot to move.The dynamic performance of the robot is determined by the drive system adopted,which depends mainly on the type of application and the power requirements.The three types of drive systems are generally used for industrial robots:Hydraulic driveElectric drive Pneumatic drive,Hydraulic DriveA hydraulic drive system gives a robot great speed and strength.These systems can be designed to actuate linear or rotational joints.The main disadvantage of a hydraulic system is that it occupies floor space in addition to that required by the robot.Problems of leaks,making the floor messy.Because they provide high speed and strength,hydraulic systems are adopted for large industrial robots.Hydraulic robots are preferred in environments in which the use of electric-drive robots may cause fire hazards,for example,in spray painting.,Electric DrivesCompared with a hydraulic system,An electric system provides a robot with less speed and strength.Electric drive systems are adopted for smaller robots.Robots supported by electric drive systems are more accurate,exhibit better repeatabilityCleaner to use.,Pneumatic Drive Pneumatic drive systems are generally used for smaller robots.These robots,with fewer degrees of freedom,carry out simple pick-and-place material-handling operations,such as picking up an object at one location and placing it at another location.These operations are generally simple and have short cycle times.Pneumatic robots are less expensive than electric or hydraulic robots.Most pneumatic robots operate at mechanically fixed end points for each axis.A big advantage of such robots is their simple modular construction,using standard commercially available components.This makes it possible for a firm to build its own robots at substantial cost savings for simple tasks such as pick and place,machine loading and unloading,and so forth.,Robotic SensorsThe motion of a robot is obtained by precise movements at its joints and wrist.While the movements are obtained,it is important to ensure that the motion is precise and smooth.The drive systems should be controlled by proper means to regulate the motion of the robot.Along with controls,robots are required to sense some characteristics of their environment.These characteristics provide the feedback to enable the control systems to regulate the manipulator movements efficiently.Sensors provide feedback to the control systems and give the robots more flexibility.Sensors such as visual sensors are useful in the building of more accurate and intelligent robots.The sensors can be classified in many different ways based on their utility.In this section we discuss a few typical sensors that are normally used in robots:Position sensors.They are used to monitor the position of joints.Range sensors.Range sensors measure distances from a reference point to other points of importance.Velocity sensors.Velocity sensors are used to estimate the speed with which a manipulator is movedProximity sensors.Proximity sensors are used to sense and indicate the presence of an object within a specified distance or space without any physical contact,The Hand of a Robot:End-EffectorsThe end-effectors(commonly known as robot hand)mounted on the wrist enables the robot to perform specified tasks.Various types of end-effectors are designed for the same robot to make it more flexible and versatile.,End-effectors are categorized into two major types:1.Grippers:2.Tools.,Grippers are generally used to grasp and hold an object and place it at a desired location.Grippers can be classified as:Mechanical grippers,Vacuum or suction cups,Magnetic grippers,Adhesive grippers,Hooks,Scoops,Others.,Grippers usually operate in jaw type fashion by having fingers which either attach to the gripper,or are part of the construction,open and close.The attached fingers can be replaced with new or different fingers,allowing for flexibility,see Figure 2.Grippers can operate with two fingers or more.,Figure 2,At times,a robot is required to manipulate a tool to perform an operation on a work part.Spot-welding tools,arc-welding tools,spray-painting nozzles,and rotating spindles for drilling and grinding are typical examples of tools used as end-effectors.,End-effectors-Tools,Gripper designs:There are many approaches to gripper designs.These Figures shows the various linkages which result in pivoting action for gripping.,Robot Movement and PrecisionSpeed of response and stability are two important characteristics of robot movement.Speed defines how quickly the robot arm moves from one point to another.Stability refers to robot motion with the least amount of oscillation.A good robot is one that is fast enough but at the same time has good stability.The precision of robot movement is defined by three basic features:high resolutionAccuracy Repeatability,1.Spatial ResolutionThe spatial resolution of a robot is the smallest increment of movement into which the robot can divide its work volume.It depends on:the systems control resolution and the robots mechanical inaccuracies.The control resolution is determined by the robots position control system and its feedback measurement system.The controller divides the total range of movements for any particular joint into individual increments that can be addressed in the controller.The bit storage capacity of the control memory defines this ability to divide the total range into increments.For a particular axis,the number of separate increments is given by,Number of increments=2nwhere n is the number of bits in the control memory.,EXAMPLE A robots control memory has 8-bit storage capacity.It has two rotational joints and one linear joint Determine the control resolution for each joint,if the linear link can vary its length from as short as 0.2 m to as long as 1.2 m.Solution Control memory=8 bit From the equation above,number of increments=28=256(a)Total range for rotational joints=360 Control resolution for each rotational joint=360/256=1.40625(b)Total range for linear joint=1.2-0.2=1.0 m Control resolution for linear joint=1/256=0.003906 m=3.906 mm,2.Accuracy Accuracy can be defined as the ability of a robot to position its wrist end at a desired target point within its reach.In terms of control resolution,the accuracy can be defined as one-half of the control resolution.,3.RepeatabilityRepeatability refers to the robots ability to position its end-effectors at a point that had previously been taught to the robot.The repeatability error differs from accuracy as described below,Let point A be the target point as shown in Figure a.Because of the limitations of spatial resolution and therefore accuracy,the programmed point becomes point B.The distance between points A and B is a result of the robots limited accuracy due to the spatial resolution.When the robot is instructed to return to the programmed point B,it returns to point C instead.The distance between points B and C is the result of limitations on the robots repeatability.However,the robot does not always go to point C every time it is asked to return to the programmed point B.Instead,it forms a cluster of points.This gives rise to a random phenomenon of repeatability errors.The repeatability errors are generally assumed to be normally distributed.If the mean error is large,we say that the accuracy is poor.However,if the standard deviation of the error is low,we say that the repeatability is high.We pictorially represent the concept of low and high repeatability as well as accuracy in Figure b,c,d,and e.Consider the center of the two concentric circles as the desired target point.The diameter of the inner circle represents the limits up to which the robot end-effector can be positioned and considered to be of high accuracy.Any point outside the inner circle is considered to be of poor or low accuracy.A group of closely clustered points implies high repeatability,whereas a sparsely distributed cluster of points indicates low repeatability.,Figure a.,Figure(a)Accuracy and repeatability;(b),high accuracy and high repeatability;(c)high accuracy and low repeatability;(d)low accuracy and high repeatability;(e)low accuracy and low repeatability.,THE ROBOTIC JOINTSA robot joint is a mechanism that permits relative movement between parts of a robot arm.The joints of a robot are designed to enable the robot to move its end-effectors along a path from one position to another as desired.The basic movements required for the desired motion of most industrial robots are:Rotational movement.-This enables the robot to place its arm in any direction on a horizontal plane.Radial movement.This enables the robot to move its end-effectors radially to reach distant points.Vertical movement.This enables the robot to take its end-effector to different heights.,These degrees of freedom,independently or in combination with others,define the complete motion of the end-effector.These motions are accomplished by movements of individual joints of the robot aim.The joint movements are basically the same as relative motion of adjoining links.Depending on the nature of this relative motion,the joints are classified as prismatic or revolute.Prismatic joints are also known as sliding as well as linear joints.They are called prismatic because the cross section of the joint is considered as a generalized prism.They permit links to move in a linear relationship.Revolute joints permit only angular motion between links.,The five joint types are:Linear joint(L).The relative movement between the input link and the output link is a linear sliding motion,with the axes of the two links being parallel.Orthogonal joint(O).This is also a linear sliding motion,but the input and output links are perpendicular to each other during the move.Rotational joint(R).This type provides a rotational relative motion of the joints,with the axis of rotation perpendicular to the axes of the input and output links.Twisting joint(T).This joint also involves a rotary motion,but the axis of rotation is parallel to the axes of the two links.Revolving joint(V).IN this joint type,the axis of the input link is parallel to the axis of rotation of the joint,and the axis of the output link is perpendicular to the axis of rotation.,two forms of linear joint-type L;two forms of orthogonal joint-type O;rotational joint-type R;twisting joint-type T;revolving joint-type V.,Example:,A typical robot manipulator can be divided into two sections:A body-and-arm assembly,and A wrist assembly.There are usually 3 degrees of freedom associated with t