Design and experiment of a ridge-surface based cutting height active adjustment system for a leafy vegetable harvester

Due to the discrepancy between the cutting baseline and the adjustment baseline, existing harvester cutting height adjustment schemes are unsuitable for the ridge-planting and ridge-crossing harvesting modes of leafy vegetables. This study proposes an active cutting height adjustment system based on the ridge surface, thereby achieving the unification of the two baselines. A combined mechanical-hydraulic adjustment scheme is designed. A cutting height adjustment model is established, considering the influence of ridge height. Changes in ridge height during actual harvesting are converted into existing system hardware information, enabling application to different ridge heights. The static test results demonstrated that the system could achieve active adjustment across varying ridge and cutting heights. Under varying ridge heights, the average response times (ARTs) for adjusting the cutting height from 0 mm to 10, 20, and 30 mm were 0.06, 0.16, and 0.22 s, respectively, with mean absolute error values (MAEVs) of 1.2, 1.5, and 1.4 mm. The ARTs for adjusting the cutting height back from 30 mm to 20, 10, and 0 mm were 0.08, 0.20, and 0.29 s, with MAEVs of 1.3, 1.4, and 1.5 mm, respectively. The field test results indicated that the established adjustment system could maintain stubble height within the allowable range of (0, 20) mm with a probability of 0.97, and the average control accuracy was 94.5 %. This study presents a novel and effective active cutting height adjustment method for ridge-planting and ridge-crossing harvesting.