Mingchuan Zhou

Comparing an ant colony algorithm with a genetic algorithm for replugging tour planning of seedling transplanter

Display Omitted Optimizing the replugging tour was used to improve the efficiency of transplanter.An ACA algorithm and a GA were proposed for optimization of the replugging tour.ACA algorithm was proved to be more efficient for optimizing the replugging tour. The important task of replugging bad or missing cells with healthy seedlings in greenhouses is carried out by automatic transplanters. Grippers of such transplanters spend a considerable amount of time shuttling between the source and target trays during replugging. Therefore, work efficiency of transplanters can be significantly improved by tour planning. In this study, performances of the ant colony algorithm (ACA), the genetic algorithm (GA), and the common sequence method (CSM) in replugging tour planning were compared. Two types of seedling trays, with 50 and 200 cells, were used. The ACA and the GA were found to have more advantages than the CSM in total tour lengths for one tray. Moreover, the ACA performed better than the GA when the numbers of empty cells and healthy seedlings in the target and source trays, respectively, increased. When a 20i?10 tray was used, the average length of the ACA decreased by 6000.9mm compared with that of the GA and by 13058.4mm compared with that of the CSM after finishing 40 empty cells in one tray. The average run times of the GA and the ACA in MATLAB (R2012a) were 0.32 and 0.94s, respectively. These results meet real-time operation requirements.

Using hyperspectral imaging to discriminate yellow leaf curl disease in tomato leaves

This paper investigated the possibility of discriminating tomato yellow leaf curl disease by a hyperspectral imaging technique. A hyperspecral imaging system collected hyperspectral images of both healthy and infected tomato leaves. The reflectance spectra, first derivative reflectance spectra and absolute reflectance difference spectra in the wavelength range of 500–1000xa0nm of both background and the leaf area were analyzed to select sensitive wavelengths and band ratios. 853xa0nm was selected to create a mask image for background segmentation, while 720xa0nm from the reflectance spectra, four peaks (560, 575, 712, and 729xa0nm) from the first derivative spectra and, four wavelengths with higher values (586, 720xa0nm) and lower values (690, 840xa0nm) in the absolute difference spectra were selected as a set of sensitive wavelengths. Four band ratio images (560/575, 712/729, 586/690, and 720/840xa0nm) were compared with four widely used vegetation indices (VIs). 24 texture features were extracted using grey level co-occurrence matrix (GLCM), respectively. The performance of each feature was evaluated by receiver operator characteristic (ROC) curve analysis. The best threshold values of each feature were calculated by Yonden’s index. Mean value of correlation (COR_MEAN) extracted from the band ratio image (720/840xa0nm) had the best performance, whose AUC value was 1.0. The discrimination result for a validation set based on its best threshold value was 100%. This research also demonstrated that multispectral images at 560, 575 and 720xa0nm have a potential for detecting tomato yellow leaf curl virus infection in field applications.

CPG-based control of smooth transition for body shape and locomotion speed of a snake-like robot

In this paper, a lightweight central pattern generator(CPG) model is designed for a snake-like robot, to achieve smooth transition of body shape and locomotion speed. First, based on the convergence behavior of the gradient system, a lightweight CPG model with fast computing time is designed and compared with other widely adopted CPG models. Then, the body shape and locomotion speed transitions in rolling gait are simulated based on the proposed CPG model. Compared with the sinusoid-based method, a smooth transition process can be achieved, without generating undesired movement or abnormal torque. Finally, extensive prototype experiments are conducted to demonstrate that the CPG-based control can effectively ensure smooth transition process and avoid abnormal torque, when the body shape and locomotion speed are changed.