Effects of Rotary Tine Tool Velocity on Soil Reaction Forces, Power, and Energy Intensity

Highlights Draft force and torque on a vertical rotary tine tool were studied for various longitudinal velocities and speed ratios. Draft force increased with longitudinal velocity but decreased with speed ratio, and soil reaction torque increased with both longitudinal velocity and speed ratio. Total power required by the tool increased with speed ratio, and energy intensity increased with speed ratio and longitudinal velocity, with substantial changes observed at higher velocities. Abstract. Studying soil-tool interaction can provide valuable information on the actuation force and energy requirements of a weeding tool operating in soil. Soil-tine interaction was investigated for a vertical rotary tine tool that was intended to be used as a weeding tool for an automated mechanical intra-row weeder. The main objective of the research was to investigate the effects of linear and rotational velocities on soil reaction forces and power associated with actuation of the rotary tine tool in soil. A series of soil bin experiments were conducted in loam soil. Soil horizontal (draft) force and torque on the tool were measured at three longitudinal/travel velocities of 0.09 m s-1, 0.29 m s-1, and 0.5 m s-1 that were used to move the tool linearly across the soil bin length. The speed ratio, defined as the ratio of the longitudinal velocity to the peripheral velocity of the rotary tines, determined the rotational speeds required for the study. The draft force and torque were evaluated at four speed ratio levels (0, 1, 1.5, and 2). An Analysis of Variance (ANOVA) performed for statistical analysis using p < 0.05 showed that both longitudinal velocity and speed ratio had significant main and interaction effects on the draft force and torque. In most cases, the draft force decreased while torque increased with increasing speed ratios for the different longitudinal velocities used in the study. Power and energy intensity were also calculated using draft force and torque measurements for different experimental settings. For increases in speed ratios, the power requirements for tool draft force decreased, whereas the power requirements for rotating the tool increased for each longitudinal velocity. At the highest test travel speed of 0.5 m s-1, the power decreased from 66 W to 28 W for draft and increased from 0 W to 76 W for rotation of the tool at increasing speed ratios. The maximum total power calculated for the tool was 110 W at 0.5 m s-1 and a speed ratio of 2. The study shows the changes in power and energy requirements of a vertical rotary tine tool for different operating parameters for weed control. This information could be valuable for optimizing the physical weeding process. Keywords: Energy intensity, Power, Rotary tool, Soil-tine interaction, Weed control.