Abstract:

Objective: In order to address the problems of limited workspace and difficulty in adapting to complex climbing environments for existing tree climbing robots, this study aims to develop a new type of claw-type tree climbing robot platform and climbing gait to expand the operating range of existing prototypes in tree trunk environments, replacing the forest researchers to carry out canopy level operations and reducing the safety hazards. Method: Based on the physiological characteristics and climbing mechanism of primate organisms, a three-armed clawed robot structure was designed, and the rationality of the design scheme was verified through the static simulation analysis. Two gait strategies, three-claw vertical climbing and dual-claw turnover, were proposed, and the workspace equations of the robot were deduced through geometric analysis to determine the maximum step length under each climbing gait. Adams dynamics simulation was used to verify the joint torque stability, and energy consumption was calculated to evaluate the range performance. Finally, field gait verification experiments were conducted using the prototype to assess the gait feasibility and the actual climbable range of the robot. Result: 1) The maximum deformation of the structure was at the sub-millimetre level, and the maximum equivalent stress in the material was 67 MPa. Theoretically, there will be no serious deformation or damage during operation, and its design and material selection meet the requirements. 2) The designed three-claw climbing gait was able to achieve a maximum step length of 210 mm, with a single gait cycle of about 4 minutes. 3) The dual-claw turnover gait was able to achieve a maximum of 51° around a tree pole turnover, with a single gait cycle of about 2.5 minutes. 4) According to the climbing range experiment, the robot was able to reach the trunk of about 61–136 mm in diameter, with an angle of about 40°–87° to the ground. 5) The endurance experiment showed that the lithium battery with a capacity of 9 800 mAh was able to continue to output the maximum working current after 30 minutes of continuous operation, and there was no obvious wear and tear on the key parts such as the joint rudder disc and the support frame of the robot. Conclusion: In this study, a new three-armed clawed tree-climbing robot and its climbing gaits are developed through the biomimetic design of primates. The robot is made of aluminum alloy and photosensitive resin material, with a total weight of about 2.5 kg. Based on the results of static simulation, the rationality of the dimensional design and the material selection is verified. Through the climbing range experiment, its adaptable diameter range accounts for about 68% of the experimental tree trunk range, and the climbable inclination angle can meet most of the climbing scenarios, and the climbing range can be further expanded by replacing the claws. After field experiments, the current power supply configuration can support at least 30 minutes of continuous climbing operation, and it can achieve continuous operation by replacing the battery in the woodland environment. The experimental results verify that the robot is able to climb with the designed gait, and shows a more ideal overall performance, which provides a new solution for assisting forest researchers to carry out high-altitude forest tree sampling and canopy monitoring.

Key words: forestry operation, tree-climbing robot, bionic design, gait strategy, workspace