A Design Scheme of High Ultrasonic Intelligent Ranging System

Abstract: Based on the shortcomings and imperfections of traditional methods in ranging, this paper proposes a high-precision ultrasonic intelligent ranging system design scheme. The scheme first carries out the principle of high-precision ultrasonic rangefinder and the application of single-chip microcomputer. The analysis; the design of its measurement accuracy has been greatly improved on the original basis; and the system debugging and error analysis are carried out. It has been verified that this system has high measurement accuracy and has achieved a small distance measurement of 0.1mm.

  1 Introduction

1.1 Overview of development at home and abroad

Intelligent ranging systems currently have a certain level of research in China, and they are mostly used in the automotive industry and the navigation systems of intelligent robots and related fields. The frequency, power and sonic characteristics of the ultrasonic waves they produce are different, so their uses are also different. At present, the piezoelectric ultrasonic generator is more commonly used.

Ultrasound is often used for distance measurement due to its strong directivity, slow energy consumption and long distance in the medium. It is mainly used in reversing radar, rangefinders, level measuring instruments, development of mobile robots, construction sites and some industrial sites, such as: distance, liquid level, well depth, pipeline length, flow rate and other occasions. Ultrasonic detection is often quick and convenient, and the calculation is simple, and it is easy to achieve real-time control. The measurement accuracy can also meet the requirements of industrial practicality. Therefore, it has been widely used. The domestic distance measurement technology is relatively complete, but this The peripheral circuit of the analog system is relatively complicated, the display part is not image enough, and the accuracy is not high, most of which stay at the centimeter level.

1.2 System function and performance requirements

This design "high-precision ultrasonic intelligent ranging system" can realize the measurement function in the range of 2cm-4m, the accuracy can reach 0.1mm, the LCD screen Chinese character display function, and the distance segment alarm function. The physical object is small in size, low in power consumption, easy to be embedded in other systems, and has a certain use value.

2. System structure

2.1 System structure block diagram



2.2 Basic working principle

A 40KHZ square wave is generated on the P1.2 port through the single-chip microcomputer driver, and the ultrasonic transmitter probe is driven by the mediating circuit. When encountering obstacles, it is reflected by the P1.1 port ultrasonic receiving probe; the time is calculated by the internal timing circuit of the single-chip microcomputer to derive the obstacle The distance between the object and the probe is displayed by LCD12864 connected to the P0 port; the distance threshold is divided into 0-1m; 1m-1.5m; and three different frequency alarms above 1.5m.

3. Hardware design

Ultrasonic sensor circuit:

(1) IO trigger ranging, providing a high level signal of at least 10us;

(2) The module automatically sends 8 40kHz square waves, and automatically detects whether there is a signal return;

(3) There is a signal return, and a high level is output through IO. The duration of the high level is the time from the ultrasonic wave to the return. Test distance = (high level time (340m/S))/2; as shown in Figure 2.



4. Software design

4.1 Flow chart

The flow chart of the ultrasonic ranging system is shown in Figure 3 below.



4.2 Program execution process

(1) MCU initialization;

(2) Detect whether there is an echo;

(3) Timing initialization;

(4) Send ultrasound;

(5) Turn off external interrupts, read time, and calculate distance;

(6) Determine whether it exceeds the threshold and whether it alarms.

Execute the program cyclically.

5. Debugging results and error analysis

This design uses the HC-SR04 ultrasonic sensor probe, and the range of its ranging performance is required to be 4cm-4m, so the measurement distance selected in the experiment is the data measurement within its effective measurement range. The measurement results and error analysis are shown in Table 1.



The main error of the experiment lies in the system error, including the system error when the true value is determined, the error caused by the non-standard human operation, and the inevitable error caused by environmental interference.

The relative error within the limited range of the ultrasonic probe is analyzed in the range of 0-2.667%, the measurement accuracy is high, and the small distance measurement of 0.1mm is realized.

  6 Conclusion

This design adopts LCD12864 to achieve real-time display; compared with the traditional ranging circuit design, this design optimizes the circuit structure to make the circuit structure simpler, and the components used are inexpensive, and all functions can be realized. On the basis of the ranging range of 4cm-4m, the measurement accuracy is improved, and the small distance measurement of 0.1mm can be achieved, and the effect is significantly improved. This confirms the feasibility of this program. (Author: Huang Kun, Xu Shuai, Ma Shilei, Zhang Lingfei)