A review on structural development and recognition–localization methods for end-effector of fruit–vegetable picking robots

Abstract

The excellent performance of fruit and vegetable picking robots is usually contributed by the reasonable structure of end-effector and recognition–localization methods with high accuracy. As a result, efforts are focused on two aspects, and diverse structures of end-effector, target recognition methods as well as their combinations are yielded continuously. A good understanding for the working principle, advantages, limitations, and the adaptability in respective fields is helpful to design picking robots. Therefore, depending on different grasping ways, separating methods, structures, materials, and driving modes, main characteristics existing in traditional schemes will be depicted firstly. According to technical routes, advantages, potential applications, and challenges, underactuated manipulators and soft manipulators representing future development are then summarized systematically. Secondly, partial recognition and localization methods are also demonstrated. Specifically, current recognition manners adopting the single-feature, multi-feature fusion and deep learning are explained in view of their advantages, limitations, and successful instances. In the field of 3D localization, active vision based on the structured light, laser scanning, time of flight, and radar is reflected through the respective applications. Also, another 3D localization method called passive vision is also evaluated by advantages, limitations, the degree of automation, reconstruction effects, and the application scenario, such as monocular vision, binocular vision, and multiocular vision. Finally portrayed from structural development, recognition, and localization methods, it is possible to develop future end-effectors for fruit and vegetable picking robots with superior characteristics containing the less driving element, rigid–flexible–bionic coupling soft manipulators, simple control program, high efficiency, low damage, low cost, high versatility, and high recognition accuracy in all-season picking tasks.

Study on the Fragrant Pear-Picking Sequences Based on the Multiple Weighting Method

“…The six-axis picking robot arm has many advantages such as good flexibility, strong compatibility, and simple structure, and can meet the positioning requirements at any point in space. Thus, the arm can successfully complete the fruit-picking task in orchards with many conditions such as considerable fruit shade, a wide fruit distribution, and complex growth environments [21][22][23][24][25][26][27][28][29]. The ROCR6 robot arm has a compact structure and excellent servo performance.…”

Low-Voltage-Driven Soft Electrothermal Actuators Based on Phase-Change Materials

“…Due to their fast response speed and high control precision, traditional rigid actuators are widely used in fields such as robotic arms 1 and rigid robots. 2 However, their rigidity limits their application in various unstructured environments and may pose risks in human−machine interactions. Additionally, their manufacturing cost is expensive because of their complex structure.…”

Design, simulation, and experiment for the end effector of a spherical fruit picking robot

“…As a terminal element directly contacting fruits and vegetables, the universality, practicality, and success rate of an end effector play a decisive role in the performance of picking robots. 28 Currently, the end effector can be classified into two categories if picking and separating methods are considered, such as rigid 29 and flexible 30 separation types. Of those, cutting tools such as scissors, blades, and saws are usually utilized to cut fruit stems after grabbing the fruit, which is so-called rigid separation method.…”