The Key Technical Study And Experimental Research Of Brushless Dc Drilling Motor

It needs to do a lot of drilling work in the oil field exploration,well drilling and oil recovery,etc.Improving the efficiency of drilling can effectively reduce the production cycle and the mining cost.Brushless dc motors(BLDC)have a lot of advantages such as small volume,high efficiency,wide speed range,etc.When the bit is directly connect the multiple BLDC motor,it not only has the advantages of large starting torque,strong overload capacity,large output torque but also improves the ability to withstand,reduces the system volume and improves the efficiency of the system.The more polar logarithmic brushless dc motor has,the smaller mechanical angle an electric angle cycle has,the higher the accuracy of the rotor position detection is,the higher the installation accuracy requirement of traditional position sensor is.In other words,the more polar logarithmic brushless dc motor has,the greater influence to motor commutation the installation error has.O n the other hand,the position sensor can be damaged under high temperature in the well.The use of position sensor is limited.Therefore,it is of great significance to study the detection method of the rotor position which can be applied to the multi-pole direct driving brushless dc drilling motor.Based on the multi-pole direct driving brushless dc drilling motor under the working conditions of low speed,high temperature,high pressure,sediment,load changing,etc,the following research work were carried out.Firstly,the rotor position detection is carried out by means of the magnetic chain function,which is independent of the rotational speed.Next,the principle of the magnetic chain function method was analyzed and a kind of method to analyze the magnetic chain function based on line inverse potentiality was put forward.In order to reduce the lazy properties of the intrinsic parameters of the motor,the magnetic chain function is simplified.There are some disturbing pulses in the waveform of simplified magnetic chain function method.The disturbing pulses can be eliminated using the method of voltage filtering.We gets the conclusion that the phase lag caused by filtering can be ignored in the low speed domain by analyzing the delay angle.In order to realize the high accuracy change of the motor,the closed-loop control based on non-commutative phase current is designed.Firstly,detect the non-commutative current errors.Then,the error value is returned to the phase change threshold,the phase change threshold is adjusted at real-time.Finally,the commutation error of the motor is compensated.After all of these analyzing,the following conclusion is made in the simulation environment.It can cause the motor to make false switch and stop when directly using the simplified magnetic chain function method.The precise exchange of the motor can be achieved by optimizing the magnetic chain function method.The non-commutative phase current of the motor is reduced by the change o f phase of the closed-loop control,and it is the indirect proof that the error of the motor is compensated.In order to verify that the motor can run normally when using the flux function optimization method under the working condition of high temperature,high pressure in well,the closed-loop control of phase change threshold and the double closed loop control system were combined together in this paper.In order to test the performance and the mechanical characteristics of the motor on the test platform,the algorithm program of electrical motor control was writhed into the flash of the DSP,the electric motor test platform was set up.The experimental results verify that the optimization of magnetic chain function is better in the actual motor control.The commutative threshold closed loop control effectively compensates for the phase change error.