Abstract:The use of small-scale agricultural machinery becomes prevalent as it provides the stability of agricultural machinery research ideas. To lay the theoretical foundation for the research and design of agriculture walking mechanism, the Phantom Camera Control software was used to measure the anterior and posterior joint angle of a goat walking on different slopes. Foot pressure was measured by the film pressure sensor. The result of joint motion sequence, range of motion, and change of range showed that the fitting degree of the measured value was accurate. As the goat walking speed increased, the level of the hind limb angle changed to ensure itself stability. When the goat is walking, the forelimbs bear more weight than the hind limbs due to the different static and physiological structures of the front and rear legs. The key parameters of gait on different slopes were analyzed. The curve of angle change of legs was measured and analyzed when the goat is walking in slope. The results showed that, with the increase of the slope gradient, the anterior hip angle ranges from 83.3° to 117.1°, the posterior hip angle ranges at 120.3°-173.1°, the left knee angle ranges from 91.3° to 170.1°, the right knee angle is roughly the same as its range of variation. When the slope increased, the pressure change of left hind foot was consistent with that of the right anterior foot, and the pressure change of right hind foot was consistent with that of the left anterior foot. This demonstrated the theory of diagonal gait. Meanwhile, with the change of the slope, the plantar pressure of the limbs changes periodically. The research results verified the rationality of the four-legged bionic mechanism under various parameters, which can provide a theoretical basis for the design of agricultural walking mechanism to adapt different slopes in the hilly and mountainous areas.
The four-legged bionic robot for agriculture has been one of the hotspots in the field of robotics. The farmland environment is complex, and the balance requirement of quadruped bionic robot is higher. However, head adjustment is a key factor affecting the balance of quadruped animals. Based on this, this study takes the four-legged animal goat as an example to investigate the effect of goat head movement adjustment on the balance of goat. In this study, the head and neck of goats were simplified to a two-link model. The kinematics model was established by D-H method. MATLAB software was used to solve it. Origin software was used to draw the movement track of the center of mass of the head. The center of mass movement of the head is a quarter ellipse. Then, the goat walking experiments were carried out on the different slopes (0°, 5°, 10°, 15°, 20°, 25°, 30°, 35° and 40°). MATLAB software was used to fit the movement data of goat head. The movement of the center of mass of the goat's head corresponds to Fourier 6. The result is: the determination coefficient is 0.8629, and the mean variance is 0.019. When the slope gradient gradually increases, the volatility gradually increases and is cyclical. The results of this study verify the rationality of the four-legged bionic mechanism under various parameters and reveal the mechanism of goat walking with an appendage at the head.
A methodology for determining the maximal regular-shaped dexterous workspace (MRsDW) of parallel manipulators (PMs) is proposed. The MRsDW is the maximal subset of the dexterous workspace with prescribed dexterity, and has a regular shape such as a circle or rectangle for the planar and a cuboid or cylinder for the spatial situation. It is one of the objects of optimal design of the PMs while the workspace size and shape are considered. The concept of the utilizable ratio of dexterous workspace (URDW) is introduced, which is a new measure for the rationality of design parameters of a PM. The methodology based on the stratified workspace boundary search technique can determine both the dexterous workspace and their MRsDW. After the problem of determination of the MRsDW is defined formally, a numerical method is proposed to solve this problem by three algorithms. Finally, the validity and efficiency of the proposed method are verified through application of the 2-DOF planar PM and the linear Delta robot.
Summary In order to study bionic walking machinery, the uphill walking processes on different slopes (0°, 10°, 20°, and 30°) were recorded by a high speed video system (VRI Phantom M110). The kinematics parameters of goat slope are analyzed using PCC and ORIGIN software. Goat's average speed decreases with the increase in gradient. The average speed of goats on the 0° slope, 10° slope, 20° slope, and 30° slope are 1.72 m/s, 1.352 m/s, 0.742 m/s, and 0.609 m/s. In the Y axis direction, the variation ranges from 0.1 m to 0.37 m. The left hind legs are basically the same as the feet of the right hind legs. In the Y axis direction, the variation ranges from 0.1 m to 0.195 m. The length of the change in the X axis is greater than the posterior foot. The range of hip joint angle changes is from 46.10 to 135.50. The knee joint angle changes is from 87.90 to 179.80. The hip joint angle of hind leg changes from 115.30 to 1700. The knee joint angle of hind leg changes from 80.50 to 172.80. The present research can provide theoretical basis for the design of a biomimetic agricultural walking mechanism.
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