Industrial Robot

Industrial RobotModern industrial robots are true marvels of engineering. A robot the size of a person can easily carry a load over one hundred pounds and move it very quickly with a repeatability of +/-0.006 inches. Furthermore these robots can do that 24 hours a day for years on end with no failures whatsoever. Though they are reprogrammable, in many applications (particularly those in the auto industry) they are programmed once and then repeat that exact same task for years.A six-axis robot like the yellow one below costs about $60,000. What I find interesting is that deploying the robot costs another $200,000. Thus, the cost of the robot itself is just a fraction of the cost of the total system. The tools the robot uses combined with the cost of programming the robot form the major percentage of the cost. That's why robots in the auto industry are rarely reprogrammed. If they are going to go to the expense of deploying a robot for another task, then they may as well use a new robot.This is pretty much the typical machine people think of when they think of industrial robots. Fanuc makes this particular robot. Fanuc is the largest maker of these type of robots in the world and they are almost always yellow. This robot has six independent joints, also called six degrees of freedom. The reason for this is that arbitrarily placing a solid body in space requires six parameters; three to specify the location (x, y, z for example) and three to specify the orientation (roll, yaw, pitch for example).If you look closely you will see two cylindrical pistons on the side of the robot. These cylinders contain "anti-gravity" springs that are a big part of the reason robots like these can carry such heavy loads. These springs counter-balance against gravity similar to the way the springs on the garage door make it much easier for a person to lift.You will see robots like these welding, painting and handling materials.The robot shown at right is made by an American company, Adept Technology. Adept is America's largest robot company and the world's leading producer of SCARA robots. This is actually the most common industrial robot. SCARA stands for Selective Compliance Articulated (though some folks use Assembly here) Robot Arm. The robot has three joints in the horizontalplane that give it x-y positioning and orientation parallel to the plane. There is one linear joint that supplies the z positioning. This is the typical "pick and place" robot. When combined with a vision system it can move product from conveyor belt to package at a very high rate of speed (think "Lucy and the candies" but way faster).The robot's joint structure allows it to be compliant (or soft) to forces in the horizontal plane. This is important for "peg in hole" type applications where the robot will actually flex to make up for inaccuracies and allow very tight part fits.mechanical hand, is also called from begins, auto hand can imitate the manpower and arm's certain holding function, with by presses the fixed routine to capture, the transporting thing 'OR' operation tool's automatic operation installment. It may replace person's strenuous labor to realize the production mechanization and the automation, can operate under the hostile environment protects the personal safety, thus widely applies in departments and so on machine manufacture, metallurgy, electron, light industry and atomic energy. the manipulator is mainly composed of the hand and the motion. The hand is uses for to grasp holds the work piece (or tool) the part, according to is grasped holds the thing shape, the size, the weight, the material and the work request has many kinds of structural styles, like the clamp, the request hold and the adsorption and so on. The motion, causes the hand to complete each kind of rotation (swinging), the migration or the compound motion realizes the stipulation movement, changes is grasped holds the thing position and the posture.Motion's fluctuation, the expansion, revolving and so on independence movement way, is called manipulator's degree-of-freedom. In order to capture in the space the optional position and the position object, must have 6 degrees-of-freedom. The degree-of-freedom is the key parameter which the manipulator designs. The degree-of-freedom are more, manipulator's flexibility is bigger, the versatility is broader, its structure is also more complex. Generally the special-purpose manipulator has 2~3 degrees-of-freedom. the manipulator's type, may divide into the hydraulic pressure type, the air operated according to the drive type, electromotive type, the mechanical manipulator; May divide into the special-purpose manipulator and the general-purpose manipulator two kinds according to the applicable scope;The purpose of manipulator control is to maintain the dynamic response of a computer-based manipulator in accordance with some prespecified system performance and desired goals. In general, the dynamic performance of a manipulator directly depends on the efficiency of the control algorithms and the dynamic model of the manipulator. The control problem consists of obtaining dynamic models of the physical robot arm system and then specifying corresponding control laws or strategies to achieve the desired system response and performance. Application of dynamic modelsRobot arm dynamic deals with the mathematical formulations of the equations of robot arm motion. The dynamic equations of motion of a manipulator are a set of mathematical equationsdescribing the dynamic behavior of the manipulator. Such equations of motion are useful for computer simulation of the robot arm motion, the design of suitable control equations for a robot arm, and the evaluation of the kinematic design and structure of a robot arm. The actual dynamic model of an arm can be obtained from known physical laws such as the laws of newtonian and lagrangian mechanics. This leads to the development of dynamic equations of motion for the various articulated joints of the manipulator in terms of specified geometric and inertial parameters of the links. Conventional approaches like the Lagrange- Euler (L-E) and the Newton-Euler (N-E)formulations can then be applied systematically to develop the actual robot arm motion equations. These motion equations are equivalent to each other in the sense that they describe the dynamic behavior of the same physical robot manipulator. However, the structure of these equations may differ as they are obtained for various reasons and purposes.Some are obtained to achieve fast computation time in evaluating the nominal joint torques in servoing a manipulator, others are obtained to facilitate control analysis and synthesis, and still others are obtained to improve computer simulation of robot motion. The derivation of the dynamic model of manipulator based on the L-E formulation is simple and systematic. Assuming rigid body motion, the resulting equations of motion, excluding the dynamics of electronic control devices, backlash, and gear friction, are a set of second-order coupled nonlinear differential equations. The L-E equations of motion provide explicit state equations for robot arm dynamics and can be utilized to analyze and design advanced joint-variable spacecontrol strategies. Unfortunately, the computation of the dynamic coefficients requires a fair amount of arithmetic operations. Thus, the L-E equations are very difficult to utilize for real-time control purposes unless they are simplified. As an alternative to deriving more efficient equations of motion, attention was turned to develop efficient algorithms for computing the generalized forces/torques based on the N-E equations of motion. The derivation is simple, but messy, and involves vector crossproduct terms. The resulting dynamic equations, excluding the dynamics of the control device, backlash, and gear friction, are a set of forward and backward recursive equations. This set of recursive equations can be applied to the robot links sequentionally. The most significant result of this formulation is that the computation time of the generalized forces/torques is found linearly proportional to the number of joints of the robot arm and independent of the robot arm configuration. With this algorithm, one can implement simple real-time control of a robot arm in the joint-variable space. The N-E formulation results in a very efficient set of recursive equations, but they are difficult to use for deriving advanced control laws. Another approach for obtaining an efficient set of explicit equations of motion is based o n the generalized d’Alembert principle to derive the equations of motion which are expressed explicitly in vector-matrix form suitable for control analysis. In addition to allowing faster computation of the dynamic coefficients than the L-E equations of motion, the G-D equations explicitly identify the contributions of the translational and rotationalSOME PROBLEMS OF MANIPULATOR MOTION CONTROL Transfer inováciíffects of the links. Such information is useful for designing a controler in state space. Furthermore, the G-D equations of motion can be used in anipulator design. The computational efficiency is achieved from a compact formulation using Euler transformation matrices (or rotation matrices) and relative position vectors between joints.The computation of the applied forces/torques from the gener alized d’Alembert equations of motion is of order () On3 , while the L-E equations are of order () On4 [or of order() On3 if optimized] and the N-E equations are of order () On , where n is the number of degrees of freedom of the robot arm.ConclusionsCurrent industrial approaches to robot arm control treat each joint of the robot arm as a simple joint servomechanism. The servomechanism approach models the varying dynamics of a manipulator inadequately because it neglects the motion and configuration of the whole arm mechanism. These changes in the parameters of the controlled system sometimes are significant enough to render conventional feedback control strategies ineffective. The result is reduced servo response speed and damping, limiting the precision and speed of the end-effector and making it appropriate only for limited-precision tasks. Manipulators controlled in this manner move at slow speeds with unnecessary vibrations. Any significant performance gain in this and other areas of robot arm control require the consideration of more efficient dynamic models, sophisticated control approaches, and the use of dedicated computer architectures and parallel processing techniquesMay divide into the position control and the continuous path according to the path control mode controls the manipulator and so on. the manipulator usually serves as the engine bed or other machine's add-on component, like on the automatic machine or the automatic production line loading and unloading and the transmission work piece, replaces the cutting tool in the machining center and so on, generally does not have the independent control device. Some operating equipment needs by the person direct control, if uses in the host who the atomic energy department manages the dangerous goods from the type operator also often being called the manipulator.The machine at left can be called a Cartesian robot, though calling this machine a robot is really stretching the definition of a robot. It is Cartesian because it allows x-y-z positioning. Three linear joints provide the three axes of motion and define the x, y and z planes. This robot is suited for pick and place applications where either there are no orientation requirements or the parts can be pre-oriented before the robot picks them up (such as surface mounted circuit board assembly)..阅读书目[1] Ben Zion Sandler. [Robotics : Designing the Mechanisms for Automated Machinery] [M] Academic Press,1999本锡安桑德勒. [机器人:机制设计自动化机械][M]学术出版社,1999[2] Jorge Angeles. [Fundamentals of Robotic Mechanical Systems][M]. Springer, 2002豪尔赫洛杉矶. [基础机器人机械系统][M]斯普林格,2002[3] Jiming Liu / Jianbing Wu. [Multiagent Robotic Systems][M]. CRC Press, 2001铭刘/建吴.[ 多智能体机器人系统][M] CRC出版社,2001。