# The Development of Rubber Tapping Machines in Intelligent Agriculture: A Review
## 3 Development of Rubber Tapping Machines
### Self-Propelled Rubber Tapping Robot  
With the development of automation technologies, automatic control, sensor recognition, image processing, and other technologies have been widely applied in rubber tapping operations, which has promoted the design of self-propelled rubber tapping robots. As shown in Figure 7a, HARIBIT [60] unveiled a rubber tapping robot based on vision and lidar technology, which used a camera to access two-dimensional code labels attached to rubber trees. The two-dimensional code label contained the height and horizontal position information of the line to be tapped. They controlled the movement of the mechanical arm in relation to the corresponding position of rubber tapping according to the label and used a depth camera to extract the coordinates of knife marks on rubber trees to construct a new cutting track for rubber tapping.  
As shown in Figure 7b, [PERSON] et al. [18] presented a rubber tapping device with a rail-based mobile platform. This was an innovation over previous rubber tapping devices. An upgraded spatial spiral trajectory was established by analyzing the trunk and  
Figure 6: Fixed tapping machine. (**a**) Bundled profiled tapping machine [59]. (**b**) Fixed compound motion track rubber tapping machine [58]. (**c**) Rubber forest cutting test site [30].  
Figure 7: Self-propelled rubber tapping robot. (**a**) Crawler-type tapping robot [60]. (**b**) Rail-mounted tapping robot [18].  
manual rubber cutting trajectories for the operation of a six-axis tandem robot arm. A compact binocular stereo vision system was used to achieve the initial perception of the parameters required for the cutting trajectory. In addition, an integrated end-effector was developed to enable a more precise perception of the cutting trajectory and cutting operations. However, the motion of this robot depended on the rail, which greatly limited the application scenarios for the robot. Moreover, the study did not provide navigational operation information for the crawler chassis. Compared with this kind of fixed automatic tapping machine, a self-propelled rubber tapping robot is more intelligent and relies on less labor. Nevertheless, there is still room for research on these robots' navigation, control, and their recognition of rubber tapping trajectories. In the context of emerging information technology development, the use of self-propelled rubber tapping robots will become a trend in the future.  
Notably, an accurate tapping track, tapping depth, tapping thickness, and profiling mechanism are the most important evaluation indexes for rubber tapping machines. We have classified the above references and summed up the indexes used in each study in Table 2. The ticks and crosses in the table indicate whether the device in the literature contains the function in the list. In terms of the current development status of agricultural robots, most of the equipment is still in the laboratory stage and has not reached the stage of industrialization and commercial use. Against this background, the research and development of agricultural robots can make breakthroughs in the following aspects. One is to develop fixed automatic rubber tapping machines. This kind of research and development does not need to move the chassis, and it is easy to carry out production tests. The other is to focus on the research and development of the operating chassis and special mechanical arms with independent positioning and control systems. An operating chassis that can plan the operating route and avoid obstacles stably would provide the premise for mobile robots to transition from the laboratory to the market.