Modeling of the power requirement and crop flow for a disc mower

Abstract

Rotary disc mowers are capable of much higher throughput than traditional mowers, and as a result have much higher power demands. With the recent increasing popularity of rotary mowers and the ever-increasing size of high-capacity forage and haying equipment, manufacturers are offering larger mowers with higher power demands. A disc mower cutterbar requires a significant amount of the total implement power, and little research has been performed relating to the study of power requirements and material movement. The objectives of this research were to develop a means of measuring cutterbar power requirements and material flow, and to perform a statistical design of the mower in operation. Using these results, it may be possible to offer insight into changes that could be considered in the design of rotary mower cutterbars.

Two types of experiments were performed on a prototype disc mower. Both experiments were performed in both alfalfa and light grass, at three different ground speeds, and at three different disc rotational velocities. The first experiment consisted of measuring the power requirements and specific energy of three individual discs on the prototype cutterbar. The rotational direction of the three adjacent discs investigated produce converging and diverging cutting zones. Measurements were made by means of instrumented drive hubs, each with individual onboard data acquisition systems. Average power measurements recorded by each instrumented hub were found to be approximately 2.45 and 3.31 kW for alfalfa and grass, respectively. Likewise, average specific energy measurements for alfalfa and grass ranged from 1.83 to 5.74 kW•h/t, respectively. The second experiment involved the optical flow field calculation from high-speed videos captured of the cutterbar in operation. A phase-based optical flow algorithm was applied to videos captured to study material flow across the cutterbar.

An analytical model and two regression models were developed to describe and predict the cutterbar specific energy at the converging and diverging zones. The analytical model was based on the cutting and transport processes as performed by the rotating discs, as well as the zero-load power. The model included the results of the averaged material flow vector angles. The regression models were fitted to the experimental specific energy results as a function of the different combinations of effects in the experimental design. All three models, which were produced for both the converging and diverging cutting zones, were found with coefficient of determination values between 0.79 and 0.96.