The Design Of The Speed Sensor Of Eelectrical Machine Based On 51 MCU

The modern electrical machinery detecting system demands for a more and more accurate parameter.The speed and rotary inertia of electrical machine are the most important parameters that affect the dynamic response of electrical machinery control system;however,the existing motor speed sensors including both noncontact and contact type have their own practical application problems.Therefore,this thesis designed a new type of motor speed measuring system based on these problems.For the low measurement accuracy of non-contact speed sensors and instantaneity difference of sensor in low motor speed,this thesis designed a new kind of photoelectric encoding disc of motor speed measuring system to study the computing method of motor speed in both low speed and high speed and the identification algorithm of direction of rotation according to the structural features of this speed sensor.For the field installation of contact type is inconvenient,this thesis devised a new kind of soft contact motor speed measuring system.The main point is to fix the position of speed sensor according to the existing structure of photoelectric encoder and localization features of motor shaft in process—center hole in the motor shaft,in another word,to fix the speed sensor through the magnet attraction between magnetic materials and ferromagnetic materials.This paper developed the idea to combine the speed measuring and calculating,aiming at solving the problem of the separation between existing speed sensor and speed calculation instrument.The sensor system structure designed in this paper includes the inner-shaft structure and a photoelectric switch sensor,in addition,the circuit,the photoelectric encoding disc,the shaping circuit amplification and the MCU processing unit.Firstly,in this system,the photoelectric correlated switch in groove profile produced a pulse signal corresponded to holes in coded disc.Then the system confirms the width and number of pulse produced by the photoelectric elements,taking advantage of the event occurred in 51 MCU caused by the rising edge and falling edge of pulse signal so as to calculate the motor speed.Through this new algorithm,the motor speed value calculated can be real-time displayed in LED digital tube thus makes it possible to communicate with the upper machine and upload motor speed value.