Effects of attitude switching parameters on switching precision and time of flexible chassis of agricultural vehicles and its optimization

Abstract: In order to study the attitude switching operation characteristics of the flexible chassis of agricultural vehicles, the attitude switching analysis of the flexible chassis and the attitude switching test based on the second-generation prototype running on the hard surface were carried out. The attitude switching state model was established, and the switching parameters were optimized by the analytic hierarchy process and genetic algorithm. The index weights were determined for the lateral running attitude and the situ rotation attitude, respectively. The first level indicator included the preparatory phase, the holding phase and the recovery phase in the attitude switching process. The secondary indicators included all test indicators such as preparatory precision, preparatory time, lateral precision, lateral time, rotation precision, rotation time, recovery precision and recovery time. The population size of genetic algorithm was 300 and the number of iterations was 200, the genetic operation was roulette selection method and single point intersection method, and the variation used the small probability variation. Through the study of the switching precision and switching time under different translation angle, motor speed, switching angle, translation speed and rotating speed were obtained, the influence of various factors and their interactions on the attitude switching of the flexible chassis and the matching relationship between different switching attitude parameters were obtained. The results showed that the primary and secondary factors affecting the preparatory and recovery precision were the translation anglemotor rotation speed. The translation speed of the lateral running attitude had a very significant influence on lateral precision and time. Under any translation angle, the optimal motor speed of the lateral running attitude was 5.4 r/min, and the optimal translation speed was 3.45 m/s. The primary and secondary factors affecting the rotating precision of the situ rotation attitude was switching angle>rotating speed. The primary and secondary factors affecting the rotating time of the situ rotation attitude was switching angle> rotating speed>interaction. Under any translation angle, the optimal motor speed in the situ rotation attitude was 5.4 r/min. When the switching angle βr∈(0, 85°), the optimal rotating speed was (0.003 3βr+0.506 8) rad/s. When the switching angle βr≥85(, the optimal rotating speed was 0.78 rad/s. The optimal switching verification test results showed that the overall trend of the theoretical and experimental value of comprehensive precision and time was consistent. For the comprehensive precision, the maximum deviation was 1.00% and the minimum deviation was 0.75%. For the situ rotation attitude, the maximum deviation was 1.70% and the minimum deviation was 0.97%. For the comprehensive time, for the lateral running attitude, the maximum deviation was 698 ms and the minimum deviation was 454 ms. For the situ rotation attitude, the maximum deviation was 361 ms and the minimum deviation was 191 ms. The optimization parameter comparison results showed that, in the lateral running attitude, the test results of the optimized parameter group was equal to the precision priority group and 4.16% higher than that of the time priority group in terms of comprehensive precision, the test results of the optimized parameter group was equal to that of the time priority group and 17 110 ms less than that of the precision priority group in terms of comprehensive time. In the situ rotation attitude, the test results of the optimized parameter group was equal to that of the precision priority group and 5.15% higher than that of the time priority group in terms of comprehensive precision, the test results of the optimized parameter group was 646 and 996 ms less than that of the time priority group and the precision priority group, respectively. The research shows that the optimized attitude switching parameter can ensure the flexible chassis complete attitude switching process with faster attitude switching efficiency with slight loss of attitude switching precision.