| Random positioning machine is an important device of microgravity simulation, and the speed setting of the biaxial is critical for simulating microgravity effect. In application, it is mainly based on experience to set the rotational speed. In this paper, we investigate the conditions simulated microgravity with random positioning machine in theory, simulation and experiment, and obtain a speed setting method of the biaxial to simulate microgravity effect with the random positioning machine.In theory, by analyzing the forces and motion of the sample in the random positioning machine, the speed range is determined to meet the simulated microgravity effects. Based on the structure of random positioning machine, the relationship between the component and the time of the gravity vector in different coordinate axes is obtained. And, the minimum running time of the simulated microgravity effect is determined by the method of calculating the average gravity.In simulatin, with the help of Matlab software, the motion trajectory of the sample in random positioning machine is simulated, the coverage rate of the trajectory in motion sphere is calculated, and the range of the theoretical speed is optimized to determine the minimum running time. In addition, the relationship between the minimum gravity response time and the minimum gravity response angle can be determined in simulation.In experiment, the macro phenomena (displacement distance and displacement angle of the root) and microscopic phenomena (starch grains distribution in root cells) are observed under different rotational speeds. The experimental results combining theoretical analysis give the optimal rotational speed of random positioning machine.It is hoped that the methods of optimal rotational speed and the minimum running time proposed in this paper can provide useful enlightenment to the biological workers when simulated microgravity effect with random positioning machine. |
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