Virtual Model of Grip-and-Cut Picking for Simulation of Vibration and Falling of Grape Clusters

Abstract

Abstract. Current robotic prototypes mainly harvest fruit clusters by gripping and cutting the main rachis. However, severe cluster vibration and fruit falling may occur during speedy harvesting. Determining the characteristics of this vibration and falling is important to achieve optimal control in robotic harvesting. Therefore, a virtual grip-and-cut model of cluster picking was developed, and corresponding cluster vibration and fruit falling simulations were performed for robotic harvesting. Multi-property finite element modeling of the main rachis was based on measurements of the rachis compression, shearing, and bending properties. A simulation model of cluster vibration was then built and combined with an end-effector model to obtain a virtual model of grip-and-cut cluster picking. The 3D vibration simulation model of a fruit cluster coupled with the grip-and-cut end-effector model effectively characterized the complex vibration in multilevel and multicomponent fruit clusters with individual diversity of the components’ properties. With the virtual model for cluster picking, dynamic interactive simulation can be realized of the fruit cluster and the grip-and-cut end-effector. Experiments verified that the average deviation of the average swing angle and fruit falling ratio were 6.09% and 8.71%, respectively. Furthermore, the finger-rachis deviation and grip-and-cut speed had a significant influence on the swing angle and fruit falling ratio. The 3D vibration simulation model of a fruit cluster and the virtual model of cluster picking are useful tools for virtual analysis and design of robotic harvesters. Keywords: Falling, Fruit cluster, Harvesting, Robot, Simulation, Vibration.

Hanging force analysis for realizing low vibration of grape clusters during speedy robotic post-harvest handling

“…However, berry drop or shatter may occur during these robotic handling operations due to the vibration of the grape cluster. For long-distance transportation that including processing, packaging, storage, and logistics operations, the probability of berry drops would greatly increase, which may also increase the handling of the cluster fruits [6][7][8][9][10][11][12][13][14] . The loss caused by berry drop and decay of fruit is up to 20% to 30%, the integrity of fresh cluster fruits and non-destructive evaluation are two major quality criteria for grape cluster fruit [15] .…”

“…In robotic hanging handling, grape clusters are hung or clamped from the main rachis after harvest and being transported towards a box [7] as shown in (Figure 1). Although robotic handling of hanging cluster fruits can overcome bruising and abrading damage, the potential problems like the vibration of the cluster and corresponding berry falling attract more and more attention in the field of robotic post-harvest handling.…”

“…It is an important handling option in practice both on industrial and farm levels. For robotic harvesting of a single fruit, several researchers conducted different studies on fruit falling damage caused by vibration of the fruit that might be happened in stem gripping and cutting [7,[28][29][30][31][32][33][34][35] of a single fruit. Robotic post-harvest handling practices with hanging cluster fruits are few in the application where the gripping or holding force will be applied to a particular cluster part (rachis) bearing all the weight of the cluster [29,[36][37][38][39][40][41] .…”

“…Theoretical modeling and simulation of the hanging cluster ruits are powerful tools for understanding the vibration and berry dropping mechanism during robotic transportation of cluster fruits. Liu et al [7] firstly developed a compound mechanical model of a grape cluster, then carried out simulation and experimental analysis under different excitations in the transportation phase after cutting to observe the swing angle for each berry of the cluster. However, the vibration mechanism of the whole cluster, characteristics, hanging force for supporting grape cluster, and the effect of swing angle on the main rachis bending during robotic post-harvest transportation are still remaining unexplored.…”

Experimental Research on Grape Cluster Vibration Signals during Transportation and Placing for Harvest and Post-Harvest Handling

“…The hanging cluster, after cutting, needs to be transported to a basket or box, then unloading and placed into a basket or bulk bin to complete the on-site transportation. Additionally, for long-distance transportation or post-harvest operations, grape clusters need to be handled several times [7][8][9][10][11][12][13][14][15]. So the probability of berry drop greatly increases.…”