Solve Ultrasonic Sensor Problems: Reflection, Noise, And Cross-over Issues Become Challenges

The application principle of ultrasonic sensor is simple, convenient and low-cost. However, there are currently some challenges in ultrasonic sensor level measurement, such as reflection, noise and crossover problems.

 

 

1. Reflection problem:

The object being detected is usually not at an ideal angle, which results in the ultrasonic sensor rarely detecting the object correctly. The main errors include:

▪Trigonometric error: When the measured object is at a certain angle with the ultrasonic distance sensor, there is an error between the detected distance and the actual distance.

▪Specular reflection: Specular reflection on the smooth surface of an object prevents sound waves from echoing, resulting in the inability to correctly detect the object.

▪Multiple reflections: When detecting corners or similar structures, sound waves are received after multiple reflections, causing the actual detection value to be different from the true distance value.

These problems can be solved by using multiple ultrasonic coils arranged at an angle to filter out the correct reading.

2. Noise:

Although most ultrasonic sensors operate at frequencies as high as 40-45kHz, which is much higher than the human hearing frequency, the surrounding environment also produces noise at similar frequencies. For example, high-frequency noise when the motor is running, noise caused by wheels rubbing on hard ground, vibration of the robot itself, and sound waves emitted by other robot sensors. These can cause the sensor to receive erroneous signals.

To solve this problem, the emitted ultrasonic waves can be encoded, for example, by emitting a set of sound waves of different lengths, and only when the detector detects the same combination of sound waves, the distance is calculated. This can effectively avoid misreading caused by environmental noise.

3. Cross-cutting issues:

When multiple ultrasonic sensors are installed on a machine at a certain angle, crossover problems can occur. For example, the sound wave emitted by ultrasonic wave X is captured by sensors Z and Y after mirror reflection, causing Z and Y to calculate an incorrect distance value based on the signal.

The solution is to encode the signal emitted by each sensor to ensure that each ultrasonic sensor only receives its own acoustic signal to avoid cross interference.