tailieunhanh - Electrical Engineering Mechanical Systems Design Handbook Dorf CRC Press 2002819s_14

Tham khảo tài liệu 'electrical engineering mechanical systems design handbook dorf crc press 2002819s_14', kỹ thuật - công nghệ, điện - điện tử phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | pick-and-place industrial systems positioned by mechanical stops. For such devices pneumatic actuation represents a fast cheap and reliable solution. The hydraulic actuator is to some extent similar to the pneumatic one but avoids its main drawbacks. The uncompressible hydraulic oil flows through a cylinder and applies pressure to the piston. This pressure force causes motion of the robot joint. Control of motion is achieved by regulating the oil flow. The device used to regulate the flow is called a servovalve. Hydraulic systems can produce linear or rotary actuation. There are many advantages of the hydraulic drives. Its main benefit is the possibility of producing a very large force or torque without using geartrains. At the same time the effector attached to the robot arm allows high concentration of power within small dimensions and weight. This is due to the fact that some massive parts of the actuator like the pump and the oil reservoir are placed beside the robot and do not load the arm. With hydraulic drives it is possible to achieve continuous motion control. The drawbacks one should mention are Hydraulic power supply is inefficient in terms of energy consumption Leakage problem is present. A fast-response servovalve is expensive. If the complete hydraulic system is considered reservoir pump cylinder and valve the power supply becomes bulky. Electric motors electromagnetic actuators are the most common type of actuators in robots today. They are used even for heavy robots for which some years ago hydraulics was exclusive. This can be justified by the general conclusion that electric drives are easy to control by means of a computer. This is especially the case with DC motors. However it is necessary to mention some drawbacks of electromagnetic actuation. Today motors still rotate at rather high speed. Rated speed is typically 3000 to 5000 . At the same time the output motor torque is small compared with the value needed to move a robot joint. For .