tailieunhanh - Crc Press - Mechanical Engineering Handbook - Robotics 1 Part 4

Tham khảo tài liệu 'crc press - mechanical engineering handbook - robotics 1 part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 14-30 Section 14 An attention to details in which issues such as power requirements impact resistance and sensor signal routing are not left as an afterthought. Some of the main considerations are briefly discussed below. Sensing Sensors are vital for some manufacturing applications and useful in many others for detecting error conditions. Virtually every end effector design can benefit from the addition of limit switches proximity sensors and force overload switches for detecting improperly grasped parts dropped parts excessive assembly forces etc. These binary sensors are inexpensive and easy to connect to most industrial controllers. The next level of sophistication includes analog sensors such as strain gages and thermocouples. For these sensors a dedicated microprocessor as well as analog instrumentation is typically required to interpret the signals and communicate with the robot controller. The most complex class of sensors includes cameras and tactile arrays. A number of commercial solutions for visual and tactile imaging are available and may include dedicated microprocessors and software. Although vision systems are usually thought of as separate from end effector design it is sometimes desirable to build a camera into the end effector this approach can reduce cycle times because the robot does not have to deposit parts under a separate station for inspecting them. Actuation The actuation of industrial end effectors is most commonly pneumatic due to the availability of compressed air in most applications and the high power-to-weight ratio that can be obtained. The grasp force is controlled by regulating air pressure. The chief drawbacks of pneumatic actuation are the difficulties in achieving precise position control for active hands due primarily to the compressibility of air and the need to run air lines down what is otherwise an all-electric robot arm. Electric motors are also common. In these the grasp force is regulated via the motor current. A .