Viewpoint Analysis for Maturity Classification of Sweet Peppers.

Ben Harel,Yael Edan,Rick Van Essen,Yisrael Parmet

doi:10.3390/s20133783

Abstract

The effect of camera viewpoint and fruit orientation on the performance of a sweet pepper maturity level classification algorithm was evaluated. Image datasets of sweet peppers harvested from a commercial greenhouse were collected using two different methods, resulting in 789 RGB—Red Green Blue (images acquired in a photocell) and 417 RGB-D—Red Green Blue-Depth (images acquired by a robotic arm in the laboratory), which are published as part of this paper. Maturity level classification was performed using a random forest algorithm. Classifications of maturity level from different camera viewpoints, using a combination of viewpoints, and different fruit orientations on the plant were evaluated and compared to manual classification. Results revealed that: (1) the bottom viewpoint is the best single viewpoint for maturity level classification accuracy; (2) information from two viewpoints increases the classification by 25 and 15 percent compared to a single viewpoint for red and yellow peppers, respectively, and (3) classification performance is highly dependent on the fruit’s orientation on the plant.

Highlights

Robotic harvesting can help overcome the lack of manual and seasonal labor, reduce production costs, and increase the quality of the harvested product [1]
Sweet peppers (Capsicum annuum L.) are widely cultivated since they are rich in flavor and a good source of vitamin C, which is known for its antioxidant activity [20,21]
These results show that two viewpoints ensure a higher chance of better classification, but still, in some cases, one viewpoint can yield the same or better results

Summary

Introduction

Robotic harvesting can help overcome the lack of manual and seasonal labor, reduce production costs, and increase the quality of the harvested product [1]. Most agricultural robotics research and development projects [3,4,5] focused on detecting [6,7,8], reaching [4,9,10], and detaching the fruit [4,9], with only a few studies focusing on maturity level determination [11,12,13]. Human harvesters usually estimate the maturity level of sweet peppers via the percentage of the pepper that has changed color from green to red/yellow [22]. The coloring percentage of pepper is highly correlated to other attributes of maturity, such as sugar content and firmness [22]. Since the whole pepper must be examined in order to estimate its color percentage, the precise determination of sweet pepper fruit

Methods

Results

Conclusion