| In order to meet the requirements of ultrasonic logging, in this paper, the DC power supply ripple and motor commutation for brushless DC motor torque ripple has been studied, and ultrasonic transducer drive motor logging control system has been developed.The torque ripple of brushless DC motor due to DC power supply ripple is implemented, the variation ripple of power supply has been analyzed a simulation study of torque ripple caused by supply has been done, and the influence of the torque ripple due to power supply has been Obtained.For the problem of torque ripple caused by motor commutation, the dissertatio- n presents a novel method based on overlap commutation and improved hysteresis current control to inhibit the commutation torque ripple. For the defects of overlapping commutation method and hysteresis current law, taking into account the the practical application of high-temperature environment, a novel based on overlap commutation and improved hysteresis current control has been presented: by combiniing the overlapping commutation and current contral with hysteresis law, the commutation torque ripple have been well suppressed. Through the direct control of non-commutation phase current and the restrictions of the switching frequency in the area of non-commutation, the system losses decreased significantly. Simulation results show that this method can well inhibit the commutation torque ripple.For the problem of false triggering by the way of traditional time-based trigger, the dissertation presents a new type of ultrasonic logging triggering method based on location. The system can not complete the north finding by detecting the magnetic field in some wells, to solve this problem, this dissertation achieve the position calibration by marking tick on the logging equipment, at the same time, aligning the initial phase of the resolver and motor.is required.According to the requirements of ultrasonic logging system, the dissertation has developed a brushless dc motor control system to drive ultrasonic logging energy converter which can realize the position detection, speed detection and logging trigger based on position by resolver. The current sampling and regulate circuit are designed to realize motor commutation, double closed loop control of speed and current by the integrated three-phase inverter bridge and DSP, the speed closed-loop controller is base on PID adjustor, and current closed loop controller is base on overlap commutation and improved hysteresis current control method. The system software has been designed to complete A/D sampling, SPI communication, position, signal processing and motor soft start, realizing double-sided SCI commu- nication between the system and the ground upper computer.Finally, using the system developed in this paper to make a experiment, the results show that the system can work reliably and stably under the environment of high temperature, and can produce accurate ultrasonic logging triggered signals. |
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