In recent years, with the need of automatic identification in the process of industrial automated production and assembly, especially the need of automatic ranging, navigation system and visual recognition system of industrial robots, a variety of identification methods and principles have emerged. According to the different information carriers, it can be summarized as optical method and ultrasonic method. However, the optical method has its limitations in some application fields, in contrast, ultrasonic method has obvious advantages in these aspects: ultrasonic propagation speed is only one millionth of light wave, so it can directly measure the target at a relatively close distance, and the longitudinal resolution is high; Sound wave is insensitive to color and illuminance and can be used to identify objects with poor transparency and diffuse reflectance; It is insensitive to external light and electromagnetic field, and can be used in dark, dust or smoke, strong electromagnetic interference, toxic and other harsh environments; Ultrasonic sensor has simple structure, small size, low cost, simple and reliable information processing, and is easy to miniaturize and integrate. The traditional ultrasonic ranging device uses two transducers, the structure is complex, easy to cause interference between each other; Temperature compensation system is adopted, which increases the cost and is not conducive to popularization.
The purpose of this ultrasonic range finder is to overcome the shortcomings of the prior art, and to provide a kind of ultrasonic range finder with strong anti-interference ability and real-time dynamic display of the measured distance.
In order to achieve the above purposes, the technical scheme of the same type ultrasonic rangefinder is: The same type ultrasonic rangefinder, which includes transducers, transmitting circuit, receiving circuit, MCU controller, the receiving circuit is mainly composed of pre-amplification circuit, bandpass filter, automatic gain circuit, shaping circuit, low-pass filter, which is characterized by the transducer and transmitting circuit, receiving circuit is connected, transmitting circuit, receiving circuit is connected with MCU controller, respectively. The single chip microcomputer controller is connected with the upper computer; The MCU controller controls the transmitting circuit, so that the ultrasonic transmitting circuit drives the transducer to emit ultrasonic narrow pulse signal regularly, while the transducer receives the reflected wave, the receiving circuit amplifies the reflected wave and transmits it to the MCU controller, the MCU controller captures the time interval corresponding to the peak value of the transmitted wave and the reflected wave. Then the time signal is sent to the upper computer by RS-485 bus standard.
The pre-amplifier circuit is composed of audio power amplifier LM386, electrical resistance R, resistor R₂, resistor R, capacitor C, capacitor C₂, capacitor C₁ form, capacitor C connected in the audio power amplifier LM386 pin 1 and pin 8, the signal from the resistor R into connected to the forward input terminal. Resistance R₂ one end of the connection resistance R, the other end of the connection, resistance R and capacitance C, connect the reverse input and output, form feedback, audio power amplifier LM386 output 5 pin connection capacitance C₂ and capacitance C, capacitance C₂ one end of the connection, change the size of the capacitance C₁ can adjust the gain value.
The automatic gain circuit is mainly composed of resistance, operational amplifier, diode, field effect tube, the output of the automatic gain circuit through the resistance R; Connected to the forward input end of OP-amp 1, the resistance R₂ end is connected to the forward input end, the other end is connected, the inverse input end of OP-amp 1 through the resistance R, connected to the output end, the resistance R₃ connected to the reverse input end, the output of OP-amp 1 through the resistance R₃ connected to the inverse input end of op-amp 2, Its forward input to the ground through resistance R, the output of op amp 2 is connected to the positive of diode D2, the negative of diode D2 is connected to the negative of diode D1, and the positive of diode D1 is connected to the output of op amp 1; The negative terminal of diode D2 is connected to the reverse input of OP-Amp 3 through resistance R, and the reverse input and output of resistor R are connected; The forward input of operational amplifier 3 via adjustable resistance R, to the ground, operational amplifier 3 via resistance R connected to the gate of the field effect tube, drain to the ground, source connected to the reverse input of operational amplifier 1, form feedback; Operational amplifier 2, operational amplifier 3 and field effect tube form the feedback of operational amplifier 1, operational amplifier 2, operational amplifier 3 according to the size of the input signal to adjust the field effect tube grid voltage, so as to adjust the feedback resistance of operational amplifier 1, change its gain, so as to change the size of the output signal, so as to make it in a certain range.
The receiver and receiver of the same type ultrasonic rangefinder adopts the above structure and has the following characteristics:
- The transmitting transducer and the receiving transducer adopt the same transducer, which can avoid the interference of the transmitting wave to the reflected wave, and is conducive to integration and miniaturization;
- The use of single-chip microcomputer technology to capture the corresponding time interval of the peak of the transmitted wave and the reflected wave; Then the time signal to RS-485 bus standard sent to the computer, through Visual Basic6.0 advanced language to compile a visual interface, the data filtering processing, real-time dynamic display of the measured distance;
- The main operational amplifier with audio power amplifier LM386 as the reflected wave detection amplifier circuit is simple in structure and has a good sex to noise ratio;
- The dynamic calibration method based on the reference material replaces the traditional temperature compensation link, eliminates the accidental factor, realizes the dynamic real-time calibration, saves the cost;
5), the peak detection method compensates the measurement error and improves the detection accuracy;
The pre-amplifier circuit adopts the amplifier circuit based on the audio power amplifier LM386, compared with the ordinary operational amplifier, not only has a good signal-to-noise ratio, but also has a simple structure and is easy to integrate. Automatic gain circuit (AGC) uses operational amplifier and field effect tube to form a controlled amplifier, and the field effect tube acts as a voltage-controlled resistor to form a feedback regulation loop. The equivalent output resistance of the FET can be controlled by changing the pressure difference between the gate and the source of the FET, so as to change the size of the input signal. Using the dynamic calibration method based on the reference material, the traditional temperature compensation link (including temperature sensor and sampling and holding circuit, etc.) is abandoned, which greatly simplifies the structure of the system and has real-time performance.
Illustrative figure
Figure 1 is a block diagram of the structure of the utility model.
Figure 2 is the single chip microcomputer controller program flow chart.
Figure 3 is the data processing flow chart of the upper computer.
Figure 4 is the main interface of data processing.
FIG. 5 shows the pre-amplification circuit diagram.
Figure 6 shows the automatic gain amplification circuit diagram.
Specific implementation mode
As shown in Figure 1, the receiver and receiver of the same size ultrasonic rangefinder, which includes a transducer, transmitting circuit, receiving circuit, MCU controller, receiving circuit is mainly composed of pre-amplification circuit, bandpass filter, automatic gain circuit, shaping circuit, low-pass filter, transducer and transmitting circuit, receiving circuit connected, The transmitting circuit and receiving circuit are connected with the single-chip microcomputer controller, and the single-chip microcomputer controller is connected with the upper computer; MCU controller controls the transmitting circuit, so that the ultrasonic transmitting circuit drives the transducer to periodically emit ultrasonic narrow pulse signal, while the transducer receives the reflected wave, the receiving circuit will magnate the reflected wave and transmit to the MCU controller, the MCU controller captures the time interval corresponding to the peak value of the transmitted wave and the reflected wave. Then the time signal is sent to the upper computer by RS-485 bus standard.
As shown in Figure 5, the said preamplifier circuit consists of audio power amplifier LM386, resistor R, Resistor R₂, Resistor R, Capacitor C₂ ₃, and Capacitor C₄ ₄. Capacitor C₄ is ₄ connected to pin 1 and pin 8 of the audio power amplifier LM386. The signal is ₄ introduced from the resistor R to the forward input. The R₂ is attached to the R, and the other ₁ ₁ form ground. The R₃ and the C₁ ₁ form a feedback form. The output pin 5 of the LM386 power amplifier ₃ is attached to the C₂ and C₃. The C₃ ₁ amount is ₁ to adjust the gain.
As shown in Figure 6, the automatic gain circuit described mainly consists of a resistor, an op amp, a diode, and a field effect tube. The output of the automatic gain circuit is connected to the forward input of op amp 1 through resistance R. The resistance R₂ end is connected to the positive input and the other end ₄ The reverse input of op amp 1 is connected to the output via resistance R₄. The resistor R₃ connects to the reverse input to the ground and the output of op amp 1 goes through resistance R. Connected to the inverse input of OP-amp 2, whose forward input to the ground through resistance R, the output of OP-amp 2 is connected to the positive of diode D2, the negative of diode D2 is connected to the negative of diode D1, and the positive of diode D1 is connected to the output of OP-amp 1. The negative of diode D2 is connected to the reverse input of OP-Amp 3 via resistance R, and resistor R is connected to the reverse input and output; The forward input end of the operational amplifier 3 through the adjustable resistance R, to the ground, operational amplifier 3 through the resistance R connected to the gate of the field effect tube, drain to the ground, the source connected to the reverse input end of the operational amplifier 1, form feedback; Operational amplifier 2, operational amplifier 3 and the field effect tube form the feedback of operational amplifier 1, operational amplifier 2, operational amplifier 3 according to the size of the input signal to adjust the field effect tube grid voltage, so as to adjust the feedback resistance of operational amplifier 1, change its gain, so as to change the size of the output signal, make it in a certain range. As shown in Figure 1, the propagation speed of sound wave in the air C is certain, and the time interval of transmitting wave and reflecting wave of ultrasonic transducer 7 can be measured to calculate the distance S from the transducer to the measured object
.
Through automatic gain amplification, filtering, detection, comparison and other links, to obtain the appropriate reflected wave signal; Using single chip computer technology to capture the corresponding time interval of the peak value of the transmitted wave and the reflected wave; Then the time signal is sent to the computer by RS-485 bus standard. The Visual interface is compiled by Visual Basic6.0, the data is filtered, and the measured distance is displayed dynamically in real time. The test head is aligned with the measured object, and then start the upper computer, the upper computer issues the test command OFFH to the single chip microcomputer, and then wait for the single chip microcomputer to send the response signal 00H, if no response signal is received, then send the start command to the single chip microcomputer again. If the response signal is received, the handshake signal OFOH is sent to the single chip microcomputer. When the handshake is successful, the single chip microcomputer starts the test, and first transmits the test distance of the reference object to the upper computer, and then transmits the test distance of the measured object to the upper computer. The task of data processing is completed by the host computer. The host computer will receive the data every 50 adjacent to do a digital filter, and then combined with the test distance of the reference, the test distance of the measured object and the actual distance of the reference object can calculate the actual distance of the measured object. This method replaces the traditional temperature compensation method, eliminates the accidental factor, and realizes the dynamic real-time calibration. The data processing program of the upper computer is compiled by Visual Basic 6.0, and has a visual interface (as shown in Figure 4), which can display the measured distance in real time by curved line. The program flow of the single chip microcomputer controller is shown in Figure 2, and the data processing flow of the upper computer is shown in Figure 3.
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