Control of variable rate system of a rotary tiller based on real-time measurement of soil surface roughness

Abstract

It is required to employ variable rate (VR) tillage because the soil is not uniform and immense spatial variability is available inside the agricultural fields. A conventional rotary tiller was instrumented to instantly vary the tillage intensity based on the tilled soil surface roughness measurement. The random roughness (RR) was estimated as the standard deviation of surface peaks and depressions which were measured using an infrared sensor. The tilling intensity was adjusted based on rising off and lowering down the tiller soil shield that was controlled by a hydraulic actuator. The soil shield could be adjusted from 0° to 80° in 20° increments with an average response time of 0.26 s. The field tests were performed in order to recognize whether the VR tiller can create predefined soil roughness which was assigned in three ranges of 0.5 ≤ RR1 ≤ 1.5, 1.5 < RR2 ≤ 2.5, and 2.5 < RR3 ≤ 3.5 cm. As a reference, a pin-type profiler was utilized to measure the soil roughness created by the VR tiller. The results showed the soil shield tended to be closer when finer predefined roughness was requested. There were no significant differences in RR over the experimental subplots which received similar adjustments, verifying the tiller performance. The results also showed that different surface roughness could be statistically separated when they were created by the tiller at different travel speeds of 2.6, 3.5, and 4.8 km/h (p < 0.01), because the soil shield tends to be closer when the travel speed increases. The tiller developed in this study could perform VR tillage across the field with an overall success of 83.3%.