*4.3. The Results and Discussion of the Pruning Test*

The results of the pruning test are shown in Table 4. Due to the unstructured natural growth of jujube tree canopy, the number of branches, which were identified to be pruned, and the location of the pruning point vary from tree to tree. Therefore, the number and position of the pruning points were different for each jujube tree in the test. Among them, when the first jujube tree was pruned, a total of 36 pruning points were determined, and 33 points were successfully pruned. The success rate of pruning was 91.67%, which was the highest among the 5 jujube trees. Additionally, the pruning time was about 29.3 min. When the 5th jujube tree was pruned, 23 of the 27 pruning points were successfully pruned, and the success rate of a single jujube tree was 85.16%, which was the lowest among the 5 jujube trees. The pruning time was about 25.6 min.


**Table 4.** The results of the pruning test.

A total of 156 pruning points were determined in the 5 tests, and the results show that 139 points were successfully pruned. The average success rate of pruning a single jujube tree was about 89.10%, and the average time was about 27.7 min. Additionally, the manipulator ran smoothly in each pruning process. The test verified the reasonableness and feasibility of the designed pruning manipulator.

Figure 15 shows the whole process of the failed pruning of the manipulator. The main reason for the failure was that the branches deviated from the sensor detection area in the pruning process of the moving cutter. Figure 16 shows the whole process of the successful pruning performed by the manipulator. The main reason for the success was the branches in the pruning process of the moving cutter; the branches are always in the sensor detection area. To summarize, the remote and small branches on the side of the jujube tree were easy to fail pruning in the test. The main reason is that the mechanical arm is in a state when the manipulator runs lateral to the jujube trees in a remote location. According to the results of the positioning accuracy of the positioning error of the manipulator, the end-effector is large at this time. In addition, small branches are easy to bend when touching the moving cutter, leading to branches deviating from the sensor detection area. The next study is to optimize and improve the sensitivity and detection range of the end-effector, so that the improved sensor can effectively avoid the jujube branches from breaking away from the detection area after bending.

**Figure 15.** The whole process of failed pruning of the manipulator. (**a**) The start of the pruning process; (**b**) during the pruning process; and (**c**) the branch has not been pruned.

**Figure 16.** The whole process of the successful pruning of the manipulator. (**a**) The start of the pruning process; (**b**) during the pruning process; and (**c**) the branch has been pruned.

At present, there are many researches on the robot technology in agricultural fields, such as orchard picking, plant protection, and fruit-tree pruning. For different agricultural production links and different operation objects, each form of research has put forward different strategies. In many cases, it is difficult to compare and evaluate the performance of different machines, because the operating objects and operating conditions greatly vary. At present, typical researches in the field of orchard pruning, such as the grapepruning robot designed by Botterill et al. [26], the apple-tree pruning robot designed by Zahid et al. [27–29], the loquat-pruning robot designed by Huang et al. [35,36], and the

high-branch pruning manipulator designed by Wu et al. [37], are still in the initial stage of research. Because the growth information and agronomic pruning requirements of jujube trees are different from other fruit trees, it is necessary to design special pruning equipment for jujube trees, according to the growth characteristics and agronomic pruning requirements of dwarf and densely planted jujube trees in Xinjiang. Fu et al. developed a shaping and pruning machine for dwarf and densely planted jujube trees [20]. This machine can realize the rapid shortening pruning function of large-scale jujube trees, with a high pruning efficiency. However, it cannot realize the thinning branch pruning function of jujube trees, and the internal ventilation and light transmission of jujube trees after pruning are poor. Therefore, on the basis of this research, we propose the manipulator pruning jujube tree program. According to the characteristics of the artificial pruning of jujube trees, a 5-DOF jujube pruning manipulator was designed by choosing a joint manipulator structure to realize the function of the selective pruning of jujube trees.
