An Automatic Plant Growth Measurement System for Plant Factory

Plant factories are closed cultivation spaces where environmental conditions are controllable. In order to find the most suitable environmental conditions for plant growth, plant features can provide a good indication. Traditional direct measurement methods are simple but destructive and laborious. In this research, an automatic plant growth measurement system, which is composed of a stereo vision system and a weight measurement system, was developed. The growth of Boston lettuces were monitored and measured with our automatic system. The camera mounted on a sliding rail was moved by a linear actuator to extend the field of view of the planting bed. Using image processing methods and stereo vision techniques, panoramic images of the plating bed were constructed and plant geometric features such as projected leaf area, maximum and minimum radii and plant volume were calculated. At the same time, plant weights were continuously recorded by the weight measurement instrument. Both the vision-based system and weight measurement system are based on non-destructive methods, so the plants features can be monitored throughout the whole growth cycle without affecting its growth. The plant growth measurement system developed in this research can obtain a large amount of plant features easily comparing to traditional destructive measurement methods. Besides, the relationship between the projected leaf area and the fresh weight of Boston lettuces was also discussed in this research. The results have proved the feasibility and functionality of this integrated system. This system would provide valuable information for plant factory managements and agricultural research applications.