Applications of Robotics in Forestry and Woodworking Machinery

　　Robotics and Its Applications in Forestry and Woodworking Machinery Kong Qinghua, Northeast Forestry University, Harbin, Heilongjiang 150040 With the continuous development and maturation of robotics technology, its range of applications has been steadily expanding. Over the past two decades, supported by the “79” Key Project and the National Sixth Five-Year Plan, China’s robotics sector has achieved remarkable progress across various fields. Under the auspices of the National Sixth Five-Year Plan and the State Forestry Administration, Northeast Forestry University has undertaken bold and effective explorations into the application of robots in forestry and woodworking machinery, yielding significant results.

　　1. Conifer Cone Collection Robot: This robot can not only collect large quantities of pine seeds during the relatively short maturation period of conifer cones, but also plays a crucial role in forest ecological conservation, forest regeneration, and sustainable forest development.

　　1.1 Structure and Operating Principle The forest cone‑collecting robot consists primarily of a manipulator, a traveling mechanism, a tractor‑based hydraulic drive system, and a microcontroller‑based control system. The manipulator comprises a rotary table, a vertical column, a main arm, an auxiliary arm, and a collecting claw, with a total of five degrees of freedom. During cone collection, the robot is positioned 35 meters from the target mother tree. The operator uses the manipulator’s rotary motor to orient the arm toward the selected tree, after which the microcontroller simultaneously raises the main and auxiliary arms in a controlled, flexible manner to a predetermined height. The collecting claw then opens and swings; once aligned with the target branch, both arms move in unison, guiding the claw along the branch’s growth direction until it reaches approximately 1.5–2 cm from the branch tip. At this point, the claw’s comb‑like teeth close around the branch, grasping the cone. The main and auxiliary arms then retract the claw along the original path, gently combing the cones off the branch and completing one harvesting cycle. The robot subsequently lowers itself, repositions the claw to align with the next branch, and repeats the process. After several cycles, the collected cones are emptied into a collection bin mounted at the rear of the tractor. Once a tree has been harvested, the manipulator is rotated to prepare for the next tree.

　　Main performance parameters: maximum operating grade 12%.

　　This project was awarded the Science and Technology Progress Award by the State Forestry Administration.

　　2. Structure and Working Principle of the New Intelligent Stump‑Removal Robot The stump‑removal robot is converted from a hydraulic excavator, serving dual purposes: it is fully hydraulically driven and computer‑controlled, with built-in visual capabilities. The excavator’s bucket is removed and replaced with the robot’s end effector—a rotary cutting head for stump removal. This cutting head features a cylindrical design, driven by two hydraulic motors; its serrated cylindrical cutter at the lower end performs the cutting operation. Once the stump is severed, a hydraulic cylinder actuates claw‑type grippers inside the cylinder wall to firmly clamp the stump. Under the coordinated action of the boom and arm, the stump is then lifted and deposited at a designated location.

　　The operating procedure of the root‑removal and cleanup robot is as follows: the operator controls the hydraulically driven locomotion system to enter the work site and manually adjusts the position of the rotary cutter head. Upon pressing the start button, the robot switches to automatic mode; the onboard computer first commands the six‑degree‑of‑freedom manipulator to perform a rotational scan, using the camera’s visual capabilities to locate the target roots. It then executes servo‑controlled positioning, rotary cutting, clamping, lifting, and stacking. The microcontroller‑based control system is installed in the robot’s cab, where operators use a real-time monitoring system comprising a camera and a 5.5‑inch display to search for the target roots. Equipped with an advanced LCD display, the robot can present various types of information—such as operational parameters and diagnostic data—on its 240×128 screen, thereby overcoming the limitation of conventional 103‑signal displays, which were understandable only to a small group of specialists. All relevant information can be readily accessed directly from the screen.

　　2.2 Main Performance Parameters: Maximum working radius of the manipulator: 8 m; minimum working radius: 4 m; maximum rotational speed of the rotary‑cutting unit: 300 r/min; arm rotation speed: 5 r/min; maximum working pressure of the hydraulic system: 16 MPa; maximum operating slope: 12°; maximum diameter of stumps to be cleared: 550 mm; post‑clearance pit diameter; operational efficiency; vehicle mass; overall dimensions; experimental and application results. This stump‑removal robot can clear approximately 100 stumps per shift, which is 50 times the output of manual root excavation. By swapping out rotary‑cutting and lifting attachments of different diameters and lengths, it can be adapted to various logging sites and regions. Using this robot for stump removal minimizes soil disturbance, reduces water and soil loss on the site, facilitates the full utilization of logging residues, and promotes artificial regeneration and afforestation while protecting the ecological environment.

　　3. Structure and Working Principle of the Intelligent Centering Log‑Loading Robot for Rotary Cutting The large-scale intelligent centering log‑loading robot for rotary cutting relies primarily on video control via an industrial camera, supplemented by contact‑based detection by a robotic arm. Without requiring the log to rotate, it achieves optimal centering during rotary cutting. This mechanism and methodology represent an advancement over the current state-of-the-art international approach, which employs laser‑based centering combined with 360° log rotation and five laser rangefinders for point‑by‑point measurement. The proposed solution not only significantly reduces investment in sensing equipment but also cuts energy consumption by 60%, while simultaneously improving centering accuracy.

　　The compact, intelligent centering and log‑feeding robot for rotary slicing is primarily used in the production of plywood made from core veneers derived from small‑diameter logs. It is the most widely adopted centering machine in China, boasts high throughput, and holds significant potential for widespread adoption. Capable of performing dynamic monitoring during high‑speed rotary slicing, it maximizes the utilization of small‑diameter timber resources, making it a mainstream solution for intelligent centering and log‑feeding in rotary‑slicing applications.

　　The operational requirements for the intelligent log‑centering and loading robot are as follows: first, it must pick up the log and feed it into the field of view of a vision system composed of two industrial cameras. The computer then performs an optimized calculation for log centering based on the shapes of the two end faces and the degree of curvature in the middle, determining the optimal theoretical center.

　　The software for the intelligent centering and log‑feeding robot used in rotary cutting is developed with the internationally popular MATLAB R2016a. Based on practical requirements, the software is divided into several core modules: a video data acquisition and processing module, a mechanical centering parameter acquisition and processing module, a centering optimization module, and a drive‑control module. These modules are integrated into an executable program. Specifically, the video data acquisition and processing module captures, processes, and analyzes images of cross‑sections 1 and 4, calculating the maximum inscribed circle and its center coordinates for each. The mechanical centering parameter acquisition and processing module acquires and processes centering parameters for cross‑sections 2 and 3, and, using the six‑point centering theory, computes the maximum inscribed circles and their center coordinates for these two sections. The centering optimization module, guided by centering optimization principles, derives the largest inscribed cylinder and the coordinates of the rotary‑cutting center based on the circle and center data from the four cross‑sections. Finally, the drive‑control module uses these computed results to command the actuating mechanism, positioning the log at the clamping point of the rotary cutter and completing one working cycle.

　　Key performance parameters: the robot’s log‑gripping stroke range is 1.5–3.2 m; its lifting range for logs is 1.5–1.9 m; it can handle logs with diameters from 0.3 to 1.6 m; and it accommodates log lengths of 1.8–2.6 m. The maximum log weight it can grasp is 3.0 t, and its visual centering accuracy is 1.0 mm. According to verification, this robot can increase the average veneer yield by 3.5%. China currently has over 3,000 plywood factories, more than 300 of which are large enough to deploy such robots. With an average annual output of 8,000 units per factory and a price of approximately RMB 2,400 per unit, the annual incremental economic benefit could reach around RMB 240 million, indicating extremely promising prospects for industrialization.