成果機(jī)器人技術(shù)chapter

1、1Robot TechnologyCh.12 computers for robots2lessonsChina Jiliang UniversityDr. Binrui Wang 212 computers for robotsThe interface between the human user and the robot will be considered. It is normally the computer interface through which a user takes advantage of all the underlying mechanics and con

2、trol algorithms. A number of algorithms associated with the kinematics, dynamics and control of robotic systems.312.1 computational speedThere exist a number of algorithms for controlling the various aspects of a robot motion for which it will be shown how the complex calculations in these algorithm

3、s can be performed in a short time. Ways to organise the software and hardware to meet the objective will also be presented.412.1.1 software speed-upsTechnique for increasing for the speed of computations in a conventional computer will be addressed. These techniques take advantage of the unique pro

4、perties of many of the calculations that are required for robot control.1. using integer arithmetic2. computing trigonometric functions3. matrix operations512.1.2 hardware considerationDistributed computing, i.e. the use of several computers interacting in real time to provide the required computati

5、onal speed and power, finds an immediate application in robotics. Here, for two simple functions.Reading encodersComputation of servo-error signals612.2 hardware requirementsThe Unimate PUMA architecture exemplifies the concept of distribution by joints. This architecture is shown in fig.12.1. A sep

6、arate processor is attached to the input and out put transducers of each joint. this processor maintains current angular position and velocity for that joint and servos that joint towards a set piont provided by the central processor.7PUMA architectureFig. 12.1 PUMA architecture8Fig.12.2 A proposed

7、architecture to decouple the servo calculations9Fig . 12.3. robot control distributed by function and by joint1012.3 control considerationsthe control system to supervise the activities of a robotic system shall be endowed with a number of tools providing the following functions1. capability of movi

8、ng physical objects in the working environment, i.e. manipulation ability.2. capality of obtaining information on the state of the system and working environment, i.e. sensory ability.113. capability of exploiting information to modify the system behavior in a preprogrammed manner, i.e. intelligent

9、ability.4. capability of storing, elaborating and providing data on system activity, i.e. data processing ability. 12Hierarchical control modulesFig. 12.4 Hierarchical control modules13Hierarchical positionFig. 12.5 Hierarchical position14Details of a single levelFig.12.6 shows this most clearly by

10、detailing a single level in the structure.1512.4 robot programmingthe greatest advantage in industrial applications of robots is their flexibility, their ability to rearrange for new production and their large movement range. However, a major obstacle in using manipulators as a general-purpose assem

11、ble machines is the lack of suitable and efficient communication between the user and the robotic system so that the user can direct the manipulator to plish a given task. Utilization of the robots flexibility presupposes effective programming.1612.4.1 online programmingonline programming takes plac

12、e at the site of production itself and involves the workcell. The robot is programmed with a teach box. online programming has the following advantages and disadvantages compared to offline programming.Advantages 1. Easily accessible 2. in concordance with the actual position of equipment and pieces

13、17 3. simplicity in programming so that even an operator with virtually no qualification can do it. Disadvantages1. Slow movement of the robot while programming2. Program logic and calculations are hard to program3. Difficult to incorporate sensor data4. Suspension of production while programming5.

14、Cost equivalent to production value6. Poorly documented18Lead through programmingOne method in online programming is called the lead through programming. This is also known as teach and playback or guiding, and is the most commonly used method in present-day industrial robots. Teach and playback is

15、typically plished by the following steps:19(i) leading the robot in slow motion using manual control through the entire assembly task and recording the joint angles of the robot at appropriate locations in order to replay the motion(ii) Editing and playing back the taught motion(iii) if the taught m

16、otion is correct, then the robot is run at an appropriate speed in repetitive mode.20Walk through programmingIn contrast to the lead through programming, the user specifies the intermediate point with a teach pendant, which is connected to a robot controller to direct and program the robot. The teac

17、h pendant has layout, weight, buttons and command sequences completely different between manufacturers.2112.4.2 offline programmingOffline programming takes place on a computer and model of workcell with the robot, workpieces and surroundings. The robot programming can in most cases be created by th

18、e reuse of existing CAD data so that the programming will be quick and effective. The advantages and disadvantages of offline programming are followings:22Advantages1. it does not occupy production equipment, and in this manner production can continue during the programming process.2. effective prog

19、ramming of logics and calculations with state-of-the-art debugging facilities.3. locations are built according to models and this can mean that programs will have to fine-tune programs on-line or utilize sensors.4. effective programming of locations.235. verifications of program through simulation a

20、nd visualization.6. well documented through simulation model with appropriate programs.7. reuse of existing CAD data.8. cost independent of production. Production can continue while programming.9. process support tools for instance selection of welding parametersDisadvantages1. need of expert users.

21、2.demands investing in an off-line programming system.24Robot-oriented programmingRobot-oriented programming languages are structured programming languages which incorporate high-level statements and have the characteristic of an interpreted language, in order to obtain an interactive environment al

22、lowing the programmer to check the execution of each source program statement before proceeding to the next one. 25A simple insertion taskFig. 12.7 A simple insertion task26Task-level programmingA completely different approach in robot programming is by task-level programming. The nature way to desc

23、ribe an assembly task is in terms of the objects being manipulated rather than by the robot motions. Task-level language make use of this fact and simplify the programming task. A task-level programming system allows the user to describe the task in a high-level language.27Task plannerFigure 12.8 sh

24、ows one possible architecture for the task planner2812.4.3 programming by simulationAmong the newest technologies available today for programming are those which use a virtual simulation. Simulation with the use of virtual models of the working environment and the robots themselves can offer advantages to both the company and programmer.2912.5 hardware architectureThe hierachical structure of t