Method for the posture control of bionic mechanical wheel-legged vehicles in hilly and mountainous areas

In response to the weaknesses of traditional agricultural equipment chassis with poor environmental adaptability and inferior mobility, a novel unmanned agricultural machinery chassis has been developed that can operate stably and efficiently under various complex terrain conditions. Initially, a new wheel-legged structure was designed by drawing inspiration from the motion principles of grasshopper hind legs and combining them with pneumatic-hydraulic linkage mechanisms. Kinematic analysis was conducted on this wheel-legged configuration by utilizing the D-H parameter method, which revealed that its end effector has a travel range of 0-450 mm in the X-direction, 0-840 mm in the Y-direction, and 0-770 mm in the Z-direction, thereby providing the structural foundation for features such as independent four-wheel steering, adjustable wheel track, automatic vehicle body elevation adjustment, and maintaining a level body posture on different slopes. Subsequently, theoretical analysis and structural parameter calculations were completed to design each subsystem of the unmanned chassis. Further, kinematic analysis of the wheel-legged unmanned chassis was carried out using RecurDyn, which substantiated the feasibility of achieving functions like slope leveling and autonomous obstacle negotiation. An omnidirectional leveling control system was also established, taking into account factors such as pitch angle, roll angle, virtual leg deployment, and center of gravity height. Joint simulations using Adams and Matlab were performed on the wheel-legged unmanned chassis, comparing its leveling performance with that of a PID control system. The results indicated that the maximum absolute value of leveling error was 1.08° for the pitch angle and 1.19° for the roll angle, while the standard deviations were 0.216 47° for the pitch angle and 0.176 22° for the roll angle, demonstrating that the wheel-legged unmanned chassis surpassed the PID control system in leveling performance, thus validating the correctness and feasibility of its full-directional body posture leveling control in complex environments. Finally, the wheel-legged unmanned chassis was fabricated, assembled, and subjected to in-place leveling and ground clearance adjustment tests. The experimental outcomes showed that the vehicle was capable of achieving in-place leveling with response speed and leveling accuracy meeting practical operational requirements under the action of the posture control system. Moreover, the adjustable ground clearance proved sufficient to meet the demands of actual obstacle crossing scenarios.

Convergent evolution inspired serrated structure for improving efficiency of soil imprinting and its mechanism investigation

Remarkable geometrical similarities are found in digging claws of soil burrowing animals,in spite of the fact that they evolved independently.Based on convergent evolution theory,this study innovatively proposed a bionic engineering perspective that focuses on general and analogous geometrical characteristics of soil animals.It was observed that soil animals with powerful burrowing ability have analogous serrated structures on their digging claws.Taking soil imprinting toothed wheel as the research object,the hypothesis that special serrated structures have the potential of reducing penetrating resistance from soil and enhancing digging efficiency for soil engaging component was investigated.The convergent evolution inspired bionic serrated structures were utilized for the design of cutting edge on toothed wheel.Then,a toothed wheel that mounted with the conventional tooth and a bionic tooth were manufactured and tested in the soil bin.Results showed that special bionic serrated structure could reduce the required draft force for toothed wheel;meanwhile increase the depth and volume of prepared micro-basin.It was found that the soil-penetrating mechanism of the bionic toothed wheel behaved as saw cutting that similar to the digging behavior of soil burrowing animals.Geometry of serrated structure has the ability to maximum stress concentrations in soil,thus increased the tendency of soil material to fail.These results indicate that the convergent evolution inspired bionic approach is novel and advantageous for the design of new soil engaging implements for working quality optimization and forward resistance reduction.