Data acquisition system for soil-tire interface stress measurement

In today’s production agriculture industry, a renewed interest has been placed on input costs and energy efficiency. The fact that the soil-tire interface of a tractive vehicle is inherently inefficient is widely known but not widely understood. To support evaluation of the soil-tire interface a measurement system was created to sense the normal stress at the interface of the tire and soil. To acquire and log the data from this sensor array, a unique data acquisition system was developed and is presented in this paper. The system utilized a microcontroller to process and write data to a compact flash card from a total of 56 analog channels. It also used a two-dimensional accelerometer to determine the angular position of the vehicle tire and the attached sensors. Custom data acquisition software was developed to log the data to the compact flash card in an efficient, organized manner. Results confirmed that the data acquisition system was capable of operating at 887 Hz per-channel analog sampling frequency. Data from field testing illustrated the capability of the accelerometer to determine wheel angular rotation and associate the applied normal stress with that angular rotation. Results also confirmed the capability of the data acquisition system to estimate the rotational angle of contact of the tire while engaging soil.