Ultrasonic sensor application is simple, easy, and cost is very low. Ultrasonic sensors but has some shortcomings, such as reflection, noise, cross-cutting issues. 1. Reflection if the detected object is always at right angles, the ultrasonic sensor will get the correct angle. But unfortunately it is in actual use, rarely detected objects can be correctly detected. 　　

Several errors can occur: 

       2. triangle error when measured with the sensor at an angle when error detection distance and actual distance has a River Delta. 

       3. mirror the problems and high school physics in the study of the reflection of light is the same. At specific angles, mirror reflection of sound waves are smooth objects out, therefore unable to generate echoes, is unable to produce the distance readings. 　　

Then the ultrasonic sensor will ignore the existence of this object. 

       4. multiple reflection of this phenomenon in detection of corner or more common similar structure of objects. 　　

Sonic rebound was many times the sensor receives, so the actual detection distance value of value is not real. These problems through the use of multiple listed according to their angle of ultrasonic wave to solve. 　　

Through multiple ultrasonic return value used to filter out the correct reading. 

       5. even though most of the operating frequency of the ultrasonic sensor for 40-45Khz, much higher than humans can hear frequencies. But the environment also produce similar frequencies of noise. 　　

For example, in rotation of the motor can produce certain high-frequency, the wheels on the firm ground of the friction generated by the high-frequency noise and jitter of the robot itself, even when there are multiple robots when other sound waves of robot ultrasonic sensor, which will cause the sensor to receive the wrong signal. This problem can be solved by encoding the emission of the ultrasonic, such as launching a set of sound waves of different lengths, only when the sensor detects the same combination of Sonic when distance calculation. 　　

This can effectively avoid misreading due to ambient noise. 

       6. cross-cutting issues when crossing multiple Ultrasonic sensors in a certain angle is caused when mounted on the robot. 　

       X ultrasonic sound waves, through specular reflection, z and y get by sensor when z and y distance value will be calculated according to the signal, making it impossible to get the correct measurement. Solutions can encode signals for each sensor. 

       Let each Ultrasonic sensors listen to its own voice.