Aiming at the problem of how the thermal characteristics of cylindrical roller bearings affect the lubrication characteristics of bearings under actual working conditions, the influence of parameters such as speed and load on the lubrication characteristics of cylindrical roller bearings under thermal effects is analyzed. The numerical calculation method combining the quasi-static model of cylindrical roller bearing and the thermal elastohydrodynamic lubrication model is adopted. The effects of rotational speed, load and thermal effect on the lubrication performance of the bearing and the lubrication state under certain oil supply conditions were analyzed via numerical model calculation. The oil film thickness was measured via an immersion ultrasonic method to verify the correctness of the model. The results show that the larger the bearing speed, the larger the central film thickness and the minimum film thickness. At the same time, the thermal effect on the film thickness is more obvious; the greater the load, the greater the maximum oil film pressure. The film thickness gradient in the inlet region is greatly reduced, but the thermal effect has no obvious effect on the overall film thickness. In addition, there is a critical value of effective lubrication film thickness for each set of operating parameters. When the actual film thickness is equal to the critical value, the bearing lubrication state is at its best; the numerical simulation results are compared with the experimental values. Under the calculation conditions, the maximum error at the measuring point is within 10%, which meets the error requirements and provides a theoretical basis for revealing the bearing lubrication mechanism.

The necks of birds that possess complex structures, graceful curves, and flexible movements are perfect natural motion actuators. Studying their structural features, mechanic characteristics, and motion rules can provide valuable references for imitating such actuators and motion functions artificially. Previous studies have analyzed the influence of two-dimensional motion geometric features and anatomical structure of the neck on motion efficiency and motion stability. However, the mechanism of motion flexibility from the perspective of neck structure has not been investigated. This study investigates the general law of the relationship between the structural parameters and motion characteristics of birds’ necks using tomography technology and 3D reconstruction technology. The results show that the structural characteristics of geese and ducks are similar, and there are significant differences in joint motion characteristics. Geese obtains complex neck postures through active intervertebral joints and highly flexible facet joints and possesses higher neck flexibility than ducks. This study provides a generic measuring method for obtaining birds’ cervical spinal vertebral structural dimensional parameters and offers a new theoretical concept for bionic robotic structural design and manufacture.

The most usual failure mode of any mechanical structure is fatigue, which is characterized by an important feature of the decrease of elastic modulus of the material. In this paper, a fatigue life evaluation model based on equivalent elastic modulus is proposed for in-service mechanical structure. In the proposed model, parameters that represent the operating conditions of the mechanical structure, such as load, vibration, and shaft torque, etc., are used as the generalized load. To replace the fatigue stress, the statistical method is used here, which is also used in the conventional fatigue analysis method. The structural strain is also measured simultaneously. Using the statistical theory, the equivalent modulus of elasticity is formulated based on the relationship of stress, strain, and modulus of elasticity. To validate the proposed model, an online fatigue damage experiment has been conducted. The experimental results have been compared with that of the fatigue life prediction model with good agreement. It is expected that the methodology proposed in this paper will be widely used.

Seedling transplanting is an important part of vegetable mechanized production in modern agriculture. After the seedlings are cultivated on a large scale by the nursery tray, they are planted into the field by the transplanter. However, unlike manual transplanting, transplanter is unable to judge the status of seedlings in the hole during seedling planting, which leads to problems such as damaged seedlings and empty holes being picked in the same order and planted into the field, resulting in yield reduction and missed planting. Aiming at this problem, we designed a seedling selective planting control system for vegetable transplanter which includes vision unit, seedling picking mechanism, seedling feeding mechanism, planting mechanism, pneumatic push rod unit, limit sensor, industrial computer and logic controller. We used asymmetrical light to construct visual identification scenes for planting conditions, which suppresses environmental disturbances. Based on the intersection operation of mask and image, a fast framework of tray hole location and seedling identification (FHLSI) was proposed combined with FCM segmentation algorithm. The vision unit provides the transplanting system with information on the status of the holes to be transplanted. Based on the information, planting system chooses the healthy seedlings for transplanting, improving the survival rate and quality of transplanting. The results show that the proposed visual method has an average accuracy of 92.35% for identification with the selective planting control system of seedlings and improves the transplanting quality by 15.4%.