| Ultrasonic ranging is a kind of typical non-contact measurement methods and is used widely.In this paper, an ultrasonic distance measurement system based on STM32Microprocessor is presented. Compared with the traditional microcontroller, the basic frequency and the Timer frequency of the STM32microcontroller reach up to72MHz, which improve the resolution of the measuring time. The PWM function of ultrasonic timer can be used to drive the launch of the ultrasonic transmitter, and the use of timer function input capture can help receive echo signals.The timer open will start PWM and input capture while beginning to ranging distance, and The superiority is that you can start PWM channels to drive ultrasonic transmitters and input capture channel at the same time. The time gain compensation (TGC) circuit is designed to, improve the measuring precision. it firstly converts amplification gain that is correspond with a certain distance to position of digital potentiometer taps, and put these position parameters to Flash. In order to reduce the blind area but not reduce measuring range at the same time, the double comparator plastic circuit is designed to respectively measure near and distant echo signals, and the close comparator can effectively screen ultrasonic diffraction signal in order to decrease the blind area. In addition, using the peak time detecting technique through the software algorithm, the arrival time of ultrasonic echo can be correctly detected.The study shows that the system measurement accuracy can reach1mm, blind area low to2.5cm, and the ranges is over500cm. when the distance is closer, the precision of the system is ideal and can be used as the reverse radar when parking cars, also can be used for liquid surface detection (liquid level of tank), can also be used for the automatic induction, robot visual identification, etc. If a big system is integrated with several range finders, then the system can be used for positioning obstacle avoidance. |
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