外文翻译---控制系统的介绍(编辑修改稿)

外文翻译---控制系统的介绍(编辑修改稿)内容摘要：

g a cutting wheel at a constant speed. When a piece of wood is applied to the surface of the cutting wheel, it acts as a disturbing torque of the motor any results in a reduction of the speed of the cutting wheel, assuming that control signal remains constant. This situation can be represented as shown in . The symbol appearing between the motor and the load represents a substractor. The effect of disturbance torques, or other secondary inputs, is detrimental to the accurate functioning of an open –loop control system, it has no way of automatically correcting its output, because there is no feedback parison. Closedloop Control System Closedloop control systems derive their valuable accurate reproduction of input from feedback parison. An error detector derives a signal proportional to the differences between the input and output. The closedloop control system drives the output until it equals the input and the error is zero. Any differences between the Fieldcontrolled dc motor Fieldcontrolled dc motor having a disturbance torque 4 active and desired output will be automatically corrected in a closedloop control system. Through proper design, the system can be made relatively independent of secondary inputs and changes in ponent characteristics. illustrates an automatic tanklevel control version of the system shown in . It can maintain the desired tank level h within quite accurate tolerances even through the output flow rate through value V1 is varied. If the tank level is not correct, an error voltage is developed. This is amplified and applied to a motor drive that adjusts value V2 in order to restore the desired tank level。