Aiming at the problems of weak driving ability and low torsional stiffness of a pneumatic flexible arm, a new type of pneumatic flexible arm is developed using three fan-shaped driving cavities and convex–concave nested constraint ring structure. A prototype was constructed, and a static model of the elongation and bending characteristics of the flexible arm was established. In addition, static experiments were conducted. Through the comparative analysis of experiment and theory, the results show that the experimental data are basically consistent with the theory, which verifies the correctness of the theoretical model. When the elongation was 0 mm and the three fan-shaped driving cavities were filled with the same air pressure of 0.25 MPa, the driving force was 2087.3N; when the three fan-shaped driving cavities were filled with the same air pressure of 0.11 MPa, the flexible arm reached a maximum elongation of 140 mm and elongation percentage of 61.9%. The proposed flexible arm could be controlled to bend in any direction in the range of 0°–360° and at any angle in the range of 0°–98° by adjusting the pressure of the three fan-shaped driving cavities. The flexible arm overcomes the shortcomings of the weak driving ability and anti-torsion ability of the flexible robot and has strong flexibility. It can be used in flexible robots in the fields of service, medical treatment, and rescue and other operations to provide greater power and reliable support for manipulators and other actuators.

To address the issues that arise when auto-leveling the vehicle body of a hillside tractor under complex working conditions, an auto-leveling control system was developed based on a newly developed hillside tractor and four-point body leveling mechanism. In this approach, leveling accuracy and stability were improved by adopting a sliding mode variable structure control algorithm based on fuzzy switching gain adjustment to achieve real-time dynamic auto-leveling control. To obtain curves of front and rear axle leveling displacement, speed, flow, pressure and body tilting angle during the leveling process, AMEsim/Simulink co-simulation was used to simulate and analyze the control system. The simulation results revealed that the tractor achieves a good leveling effect under complex working conditions in hilly and mountainous areas; the tractor can remain within a ±2° tilting angle range during the leveling process and can return to 0° after leveling, demonstrating good dynamic stability. To further assess the algorithm, a model of the system was submitted to live-testing on a custom-built auto-leveling test bench. Comparison of the test and simulation results revealed a close agreement between the two, indicating that the self-leveling control system and control algorithm developed in this study have high leveling accuracies. The results reported in this paper could provide assistance with or in reference to obtaining solutions to the problems of tractor body leveling in hilly and mountainous areas.

No abstract