*3.2. Effect of Different Factors on Vibration Signals*

In this section, the effect of different factors such as speed, acceleration of the actuator on the vibration signals of the grape cluster during vertical transportation is studied. The experimental effect of different packaging materials on the grape cluster at different speed and acceleration excitations is explained. Additionally, the effect of the cluster's mass on berry deflection during vertical transportation and placing is analyzed. The details about the effect of these factors on the vibration signals are given in the subsequent sections.

#### 3.2.1. Effect of Different Speeds during Vertical Transportation

Figure 7 shows the force signals of the hanging grape cluster during different phases of vertical transportation under different speed excitations (0.4, 0.6, 0.8, 1.0 m/s). Based on the results, the magnitude of force for the grape cluster was observed at maximum at the start position (acceleration of the actuator) for four speeds, i.e., 12.2, 12.25, 12.28, 12.4 N. This was due to the sudden excitation coming from the actuator and transmitted towards the hanging grape cluster at the start; the cluster vibrated with high magnitude. Additionally, the magnitude of force increases with an increase in the speed of the actuator. It was observed from Figure 7 that the force signals suddenly decreased because gravity helped to reduce the weight of the cluster. After that, the signals showed that the cluster moved downward with constant speed and collided with the packaging material. After colliding with the packaging surface, the force signals suddenly became low because the excitation that comes from the packaging surface was transmitted to the whole cluster. Then, force signals showed some fluctuations after the impact due to the deflection of the cluster, and, at last, the force signals showed that the cluster reached the stop position, which showed the calibrated value of the grape cluster. These results suggest that the accelerating phase of the actuator caused the vibration of the cluster and more berry drop at this phase of robotic vertical transportation of the grape cluster.

**Figure 7.** Effect of different speeds on the force of the grape cluster during vertical transportation test: (**a**) 0.4 m/s; (**b**) 0.6 m/s; (**c**) 0.8 m/s; (**d**) 1.0 m/s.
