Structural design of a mobile robot based on feline claw bionics and analysis of obstacle crossing

Traditional wheeled mobile robots have been extensively applied in various fields such as logistics, agriculture, and service industries, owing to their remarkable motion smoothness, high speed, and excellent maneuverability. Nevertheless, due to the limited obstacle-crossing capabilities, it is arduous for them to handle the complex terrains in urban areas, such as curb-side steps and continuous outdoor steps. To enhance the adaptability of wheeled robots to unstructured environments, this paper proposes a novel flexible transformable mechanism and corresponding transmission scheme, inspired by the bionic principle of feline claws. Different from other transformable wheel structures, the presence of the drag spring within this mechanism endows the wheel with improved motion smoothness during reverse movement and significant advantages in motor and servo protection. To ensure stable obstacle crossing, the process is systematically analysed and the maximum acceleration is evaluated based on the zero moment point method. Virtual prototyping simulation results show that, during the robot's reverse motion, the range and standard deviation of the centre of the mass velocity fluctuation are reduced by 98.31% and 98.26%, respectively; the average torque magnitude optimization rate of the motor reaches 79.73%, and the average torque standard deviation optimization rate is 76.49%. Under various urban operating conditions, the servo protection effect is also significant, with the best performance observed in continuous steps climbing scenarios, where the average torque magnitude optimization rate is 93.17% and the torque fluctuation optimization rate is 90.20%. Servo protection performance experiment indicate that the designed flexible structure achieves a torque optimization rate of 85.00%, further validating the advantage of the flexible configuration. Finally, experiments on single-step and continuous-step conditions verify that the robot can traverse a single step of 165 mm in height, and continuous steps of 115 mm in height and 410 mm in width, demonstrating excellent adaptability to urban environments. The results of this study provide a new design approach for protecting motors and servos in current transformable wheel systems based on bionic principles.