Estimation of agricultural soil surface roughness based on ultrasonic echo signal characteristics

Roughness is an important physical property of soil surface, and the estimation of soil surface roughness (SSR) has widely applications in the working performance evaluation and parameter control of agricultural machinery. This paper analyzed the influence of SSR on the reflection characteristics of ultrasonic beam and the subsequent changes in the receiver output voltage signal. Then, taking the peak output voltage Vmax, median value time interval Tm, single-cycle voltage integral Er and peak time interval Tp of the received voltage signal as inputs, an SSR estimation model based on adaptive neuro-fuzzy inference system (ANFIS) was established. The experimental results showed that the average estimation error was less than 18% with the measurement distance in 40 - 45 cm. The proposed method is different from laser scanning, depth camera and other non-contact measurement methods to obtain a 3D shape of the soil surface through the point cloud information, but directly estimates the SSR according to the reflection characteristics of the ultrasonic beam. Therefore, it is convenient and efficient, and the measurement component is mainly an ultrasonic sensor. The measurement principle determines that it has a good anti-interference performance to the ambient light intensity, dust and machine vibration, and can well meet the real-time requirements.