| The flexible chassis can be used for patrol monitoring and road transportation in narrow spaces such as facility agriculture,and part of field operations.Through the cooperation of the four single-wheel running systems and the chassis frame,the flexible chassis can achieve various road running modes such as attitude steering,attitude translation and attitude switching.The 8 k W flexible chassis prototype was designed and trial-produced.The hardened road running test of attitude steering,attitude translation and attitude switching mode was based on this prototype.Through the analysis and optimization of the test results,the state model and optimal input parameters of the flexible chassis attitude operation mode were obtained.In order to provide a corresponding theoretical and experimental basis for the multi-attitude operation planning problem of the flexible chassis.The main conclusions of this project are as follows:1)An 8 k W flexible chassis prototype based on four-wheel independent drive and four-wheel independent steering technology was designed and prototyped.The dimensions of the flexible chassis prototype was 1715 mm × 1475 mm × 1135 mm.The wheel tread was 1320 mm and the wheel base was 1200 mm.The minimum ground clearance was 235 mm.the mass of chassis was 750 kg.The rated traction was 2400 N and the rated power was 8 k W.The maximum design speed was 28 km·h-1.The theoretical plowing operation speed was 5 km·h-1 and the theoretical continuous plowing operation time was more than 1 h.The modular layered control system using CAN bus communication was designed and built,including the status monitoring modules of flexible chassis,the central control modules of flexible chassis and the control modules of single-wheel running system.2)The motion process of the flexible chassis attitude steering mode was analyzed,the attitude steering mode hardened surface test was carried out,and the attitude steering mode state model of the flexible chassis was obtained.Through the analysis of variance of the test results,the relationship of steering angle,motor speed and steering speed on steering precision and steering time index in discontinuous and continuous steering motion were obtained.In the two-wheel steering attitude,the primary and secondary relation of the test factors on the steering preparatory precision,the steering preparatory time,the steering recovery precision,the steering recovery time,the steering tangential-enter time and the steering tangential-exit time was steering angle > motor speed > interaction;the primary and secondary relation of the test factors on the steering tangential-enter precision and the steering tangential-exit precision was steering angle > motor speed;the primary and secondary relation of the test factors on the steering holding precision was steering angle > steering speed;the primary and secondary relation of the test factors on the steering holding time was steering speed > steering angle > interaction.In the four-wheel steering attitude,the primary and secondary relation of the test factors on the steering preparatory precision,the steering recovery precision,the steering tangential-enter time and the steering tangential-exit time was steering angle > motor speed > interaction;the primary and secondary relation of the test factors on the steering preparatory time and the steering recovery time was steering angle > motor speed;the primary and secondary relation of the test factors on the steering tangential-enter time was motor speed > steering angle;the primary and secondary relation of the test factors on the steering tangential-exit time was motor speed > steering angle >interaction;the primary and secondary relation of the test factors on the steering holding precision was steering angle > steering speed > interaction;the primary and secondary relation of the test factors on the steering holding time was steering speed > steering angle > interaction.3)The motion process of the flexible chassis attitude translation mode was analyzed,the attitude translation mode hardened surface test was carried out,and the attitude translation mode state model of the flexible chassis was obtained.Through the analysis of variance of the test results,the relationship of translation angle,motor speed and translation speed on translation precision and translation time index in discontinuous and continuous translation motion were obtained.In the translation preparatory and translation recovery phase of interrupted translation motion,the primary and secondary relation of the test factors on translation preparatory precision,translation preparatory time,translation recovery precision and translation recovery time was translation angle > motor speed > interaction.In the translation tangential-enter and translation tangential-exit phase of continuous translation motion,the primary and secondary relation of the test factors on translation tangential-enter time,translation tangential-exit precision and translation tangential-exit time was translation angle > motor speed > interaction;the primary and secondary relation of the test factors on translation tangential-enter precision was motor speed > translation angle.In the translation holding phase of interrupted and continuous translation motion,the primary and secondary relation of the test factors on translation holding precision were translation speed > translation angle(Quadrant Ⅰ and Quadrant Ⅲ),translation angle > translation speed(Quadrant Ⅱ),translation speed > translation angle>interaction(Quadrant Ⅳ);the primary and secondary relation of the test factors on translation holding time were translation speed > translation angle > interaction(Quadrant Ⅰ and Quadrant Ⅲ),translation speed > translation angle(Quadrant Ⅱ and Quadrant Ⅳ).4)The motion process of the flexible chassis attitude switching mode was analyzed,the attitude switching mode hardened surface test was carried out,and the attitude switching mode state model of the flexible chassis was obtained.Through the analysis of variance of the test results,the relationship of translation angle,motor speed and lateral running speed in lateral running motion and translation angle,motor speed,rotation switching angle and rotation angular speed in situ rotation motion on translation precision and translation time index were obtained.In lateral running motion,the primary and secondary relation of the test factors on switching preparatory precision and switching recovery precision was motor speed > translation angle;the primary and secondary relation of the test factors on switching preparatory time and switching recovery time was translation angle > motor speed;the primary and secondary relation of the test factors on lateral holding precision and lateral holding time was lateral speed having a very significant impact.In situ rotation motion,the primary and secondary relation of the test factors on switching preparatory precision and switching recovery precision was motor speed > translation angle;the primary and secondary relation of the test factors on switching preparatory time and switching recovery time was translation angle > motor speed;the primary and secondary relation of the test factors on rotation holding precision was rotation switching angle > rotation angular speed;the primary and secondary relation of the test factors on rotation holding time was rotation switching angle>rotation angular speed > interaction.5)Based on the analytic hierarchy process and genetic algorithm,the optimal input parameters of the state model of attitude steering,attitude translation and attitude switching mode were solved,and the solution results were verified by tests.In attitude steering mode,the optimization results of two-wheel steering motion input parameters were as follows: in any quadrant,the steering speed was 4 m·s-1 and the motor speed was 5.4 r·min-1.The optimization results of four-wheel steering motion input parameters were as follows: in any quadrant,the motor speed was 5.4 r·min-1;in quadrant I,when the steering angle was(0,60)°,the steering speed was(0.00001φ2 + 0.014φ + 3.538)m·s-1;and when the steering angle was [60,180]°,the steering speed was 4 m·s-1;in quadrants II,III and IV,the steering speed was 4 m·s-1.In attitude translation mode,the optimization results of interrupted translation motion input parameters were as follows: in any quadrant,the translation speed was 4 m·s-1;the motor speed was(0.2480θ + 4.5211)m·s-1 in quadrant I,(0.2921θ + 3.5456)m·s-1 in quadrant II,(0.3027θ + 2.9356)m·s-1 in quadrant III and(0.2944θ + 3.2925)m·s-1 in quadrant IV.The optimization results of continuous translation motion input parameters were as follows: in any quadrant,the translation speed was 4 m·s-1;the motor speed was(0.2027θ + 9.2392)m·s-1 in quadrant I,(0.1978θ + 9.4408)m·s-1 in quadrant II,(0.1970θ + 9.3528)m·s-1 in quadrant III and(0.1968θ + 9.4864)m·s-1 in quadrant IV.In attitude switching mode,the optimization results of lateral running motion input parameters were as follows: in forward direction,the motor speed was 5.4 r·min-1 and the lateral speed was 3.47 m·s-1;in backward direction,the motor speed was 5.4 r·min-1 and the lateral speed was 3.54 m·s-1.The optimization results of situ rotation motion input parameters were as follows: in forward direction,the motor speed was 5.4 r·min-1;when the rotation switching angle was(0,90)°,the rotation angular speed was(0.0031βsr + 0.5146)rad·s-1;when the rotation switching angle was [90,180]°,the rotation angular speed was 0.78 rad·s-1.in backward direction,the motor speed was 5.4 r·min-1;when the rotation switching angle was(0,90)°,the rotation angular speed was(0.0031βsr + 0.5080)rad·s-1;when the rotation switching angle was [90,180]°,the rotation angular speed was 0.78 rad·s-1. |
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