Under the global wave of a new technological revolution, China has identified seven strategic emerging industries: energy conservation and environmental protection, new energy, next-generation information technology, biotechnology, high-end equipment manufacturing, new materials, and new-energy vehicles. Meanwhile, since the Internet of Things represents an extension and application of internet technologies, coupled with continuous innovations in productivity and means of production, coal mine mechanical and electrical equipment has also seen rapid promotion and development. In coal mining production, mechanical and electrical equipment is playing an increasingly significant role, permeating every stage along the entire production line. A large number of coal-mining devices have been introduced and put into use in coal mines, leading to a corresponding increase in coal extraction volumes. However, this rise in extraction volume has brought about a new challenge: how to safely and efficiently transport the extracted coal out of the mine. To address this issue, Chinese coal mines have adopted measures such as increasing the number of locomotive transport vehicles, boosting the speed of electric locomotives, and operating locomotives around the clock—24 hours a day. As a result, drivers are prone to fatigue driving and loss of concentration, thereby creating a host of safety hazards. Therefore, the design of a locomotive collision-avoidance alarm system has become critically important for ensuring coal mine safety. The key technology behind this system lies in distance measurement—the ability to determine the distance between the locomotive and any obstacles ahead. Today, ultrasonic sensors, having undergone rigorous testing in numerous industrial applications, represent an ideal solution for both distance measurement and object detection. As a typical non-contact measurement method, ultrasonic ranging finds widespread use in many fields, including industrial automation control, construction engineering surveying, and robotic visual recognition. Compared with other distance-measuring methods, ultrasonic ranging is unaffected by factors such as illumination levels, smoke, or electromagnetic interference. It is now commonly employed in reversing radar systems, construction sites, and various industrial environments. In recent years, efforts to enhance the effective range of ultrasonic ranging systems while simultaneously improving their measurement accuracy and anti-interference capabilities have emerged as another crucial research direction in ultrasonic ranging technology.
　　Ultrasonic Ranging Sensor Ranging Principle
　　An ultrasonic ranging device consists of three main components: an ultrasonic transmitter, a receiver, and a signal-processing unit. As a special type of sound wave, ultrasonic waves share the fundamental physical characteristics of conventional sound waves. Ultrasonic ranging operates precisely by exploiting the reflection properties of these waves. The ultrasonic transmitter continuously emits a series of consecutive pulses—such as ultrasonic waves at 30 kHz—and provides a short pulse to the measurement logic circuit. When the receiver detects the reflected wave that bounces back from an obstacle after encountering it, it also sends a short pulse to the measurement logic circuit. Subsequently, a bistable circuit converts these two short pulses into a square-wave pulse. The width of this square-wave pulse corresponds to the time interval between the two short pulses. By measuring the width of this square-wave pulse, we can determine the distance between the transmitter and the target object. Furthermore, by measuring the width of the output pulse—the time interval between the emission and reception of the ultrasonic wave—we can calculate the distance [S] between the locomotive and the obstacle using the following formula: \[ S = \frac{1}{2} v t \] where: - \( v \) is the speed of sound (i.e., the speed of ultrasonic waves); - \( t \) is the time interval between the emission and reception of the ultrasonic wave.
　　Although ultrasonic ranging sensors have many advantages, the detection range of ultrasonic distance measurement depends on both the transmission power and the receiver sensitivity. The greater the transmission power, the stronger the returning echo, and the farther the measurable distance. However, this also brings about a side effect: the longer the reverberation time, making it impossible to measure objects at close ranges. Moreover, when measuring obstacles at greater distances, the returned echo signals become increasingly weak, necessitating prior amplification through an amplification circuit. The higher the amplification factor, the greater the sensitivity and the farther the measurable distance—but at the same time, interfering signals are also amplified, leading to measurement errors. Therefore, by carefully controlling the transmission power and receiver sensitivity, it is possible to achieve an optimal balance between measurement range and stability.
　　Considering the complex environment of coal mines themselves and aiming to achieve long-distance ultrasonic ranging, Gongcai.com recommends the MaxBotix high-performance sonar range sensor—ultrasonic transducer MB7040. This product is an industrial outdoor I2CXL-MaxSonar-WR sensor featuring a robust PVC housing that provides IP67-level protection. These sensors offer detection ranges from short to long distances and feature a narrow beam angle. On the other hand, the I2CXL-MaxSonar-WR outdoor ultrasonic sensor boasts high-power output, noise suppression, and automatic calibration capabilities. In addition to the standard I2CXL-MaxSonar-WR model, we’ve also developed an F option designed for use in particularly hazardous chemical environments where extra protection is required. Highly corrosive gases or liquids can degrade or damage the operation of sensing devices. Therefore, we provide a chemically inert seal that enables our sensors to function reliably in all kinds of chemical environments. Beyond their chemical resistance, these sensors also exhibit enhanced performance in humid or dusty environments.