| 基于PWM信号的农用柔性底盘驱动与转向协同控制特性试验 |
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| 引用本文： | 瞿济伟,郭康权,高华,宋树杰,李翊宁,周伟.基于PWM信号的农用柔性底盘驱动与转向协同控制特性试验[J].农业工程学报,2018,34(7):75-81. |
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| 作者姓名： | 瞿济伟 郭康权 高华 宋树杰 李翊宁 周伟 |
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| 作者单位： | 1. 西北农林科技大学机械与电子工程学院，杨凌 712100；,1. 西北农林科技大学机械与电子工程学院，杨凌 712100；2. 陕西省农业装备工程技术研究中心，杨凌 712100；,1. 西北农林科技大学机械与电子工程学院，杨凌 712100；,3. 陕西师范大学食品工程与营养科学学院，西安 710119,1. 西北农林科技大学机械与电子工程学院，杨凌 712100；,1. 西北农林科技大学机械与电子工程学院，杨凌 712100； |
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| 基金项目： | 国家自然科学基金资助项目（51375401） |
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| 摘 要： | 针对四轮独立驱动独立转向的农用柔性底盘驱动转向时需要同时打开和锁紧电磁摩擦锁的矛盾,该文提出一种基于脉冲宽度调制信号(pulse width modulation,PWM)的电磁摩擦锁控制方法来实现偏置转向轴机构的分时步进驱动和转向,并利用自制偏置转向轴试验台,采用双因素试验测试了PWM波频率和占空比对偏置转向轴电磁摩擦锁脉冲锁紧力矩的影响,采用三元二次正交旋转组合试验测试了分时步进驱动和转向时频率、占空比和轮毂电机转速对转向特性的影响。双因素试验结果表明:频率、占空比及其交互作用对脉冲锁紧力矩均有极显著影响(P0.01);在频率4~24 Hz、占空比20%~80%时,锁紧力矩变化范围为6.822~40.046 N·m;旋转组合试验结果表明:频率、占空比、两者交互作用及轮毂电机初始转速对分时步进转向时转向平均角速度均有显著影响(P0.05),转向平均角速度随占空比和轮毂电机初始转速增大而减小,随频率增大而缓慢增大,在频率4~24 Hz、占空比20%~80%、初始转速30~120 r/min时,转向平均角速度变化范围为0~0.514 rad/s。该结论可为农用柔性底盘驱动与转向协同控制提供参考。
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| 关 键 词： | 农业机械 运输 控制 柔性底盘 PWM技术 偏置转向轴 驱动与转向 协同控制 |
| 收稿时间： | 2017/12/20 0:00:00 |
| 修稿时间： | 2018/3/5 0:00:00 |
Experiments on collaborative control characteristics of driving and steering for agricultural flexible chassis based on PWM signal |
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| Qu Jiwei,Guo Kangquan,Gao Hu,Song Shujie,Li Yining and Zhou Wei.Experiments on collaborative control characteristics of driving and steering for agricultural flexible chassis based on PWM signal[J].Transactions of the Chinese Society of Agricultural Engineering,2018,34(7):75-81. |
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| Authors: | Qu Jiwei Guo Kangquan Gao Hu Song Shujie Li Yining and Zhou Wei |
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| Institution: | 1. College of Mechanical and Electronic Engineering, Northwest A&F University, Yangling 712100, China;,1. College of Mechanical and Electronic Engineering, Northwest A&F University, Yangling 712100, China; 2. Shaanxi Engineering Research Centre for Agriculture Equipment, Yangling 712100, China;,1. College of Mechanical and Electronic Engineering, Northwest A&F University, Yangling 712100, China;,3. College of Food Engineering and Nutritional Science, Shaanxi Normal University, Xi''an 710119, China,1. College of Mechanical and Electronic Engineering, Northwest A&F University, Yangling 712100, China; and 1. College of Mechanical and Electronic Engineering, Northwest A&F University, Yangling 712100, China; |
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| Abstract: | Abstract: Electromagnetic friction lock is an important part of agricultural flexible chassis. When it is closed, flexible chassis will be driven forward, and will steer when opened. In engineering practice, flexible chassis needs to steer while advancing. Therefore, there is conflict between the opening and the closing of electromagnetic friction lock when the 2 motions need to be carried out at the same time. In order to solve this problem, a method based on pulse width modulation (PWM) technology was proposed to control the opening and the closing in this paper. The opening was achieved during low level of PWM wave, while the closing was achieved during high level of PWM wave. In this way, flexible chassis can be driven forward during steering. Further, some experiments were conducted to investigate the influences of PWM frequency and duty cycle on driving and steering performance of flexible chassis. Firstly, based on off-centered steering shaft test bench, two-factor experiments were performed to study the effects of frequency and duty cycle on pulse tightening torque, using a traction device which was composed of a lever and a force sensor. Then tightening torque was calculated from force sensor measurement and arm length value. Secondly, for the purpose of examining the characteristics of time-sharing steering related with the influence of frequency, duty cycle and initial speed of electric wheel, a quadratic orthogonal regression experiment was conducted on off-centered steering shaft test bench. In this test, steering motion was simulated by controlling the speed of horizontal turntable of test bench and electric wheel. Average steering angular velocity was taken as the evaluating indicator of steering characteristics, and it can be attained by measuring the steering time due to the same target angle of steering. Afterwards, results of two-factor experiment showed that frequency, duty cycle and their interaction had highly significant influences on tightening torque (P<0.01). In the process of rotation, the curve of tightening torque showed a pulse change, and the rotation angle of steering arm displayed a step-like rise. When frequency was 4-24 Hz and duty cycle was 20%-80%, the tightening torque of off-centered steering shaft varied from 6.822 to 40.046 N·m. The tightening torque declined as frequency increased when duty cycle was 20%-80% except a few duty cycles. Meanwhile, for the frequency ranging from 4 to 24 Hz, tightening torque rose with the increasing of duty cycle. Then regression analysis was carried out according to the results and a regression model was presented. Results of quadratic orthogonal regression experiment illustrated that the average steering angular velocity was remarkably influenced by the PWM frequency, duty cycle and their interaction as well as the initial rotation speed of in-wheel motor (IWM) (P<0.05). With the increment of duty cycle and the initial speed of IWM, the steering average angular velocity decreased rapidly but slowly increased with the increasing of frequency. When the frequency was 4-24 Hz and the duty cycle was 20%-80%, and the initial speed of IWM was 30-120 r/min, the average steering angular velocity varied from 0 to 0.514 rad/s. Therefore, through changing the PWM frequency, duty cycle and the initial speed of IWM, the process of pulse-driven and time-sharing steering for flexible chassis is able to be well achieved, and these results can provide a basis for cooperative control of flexible chassis. |
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| Keywords: | agricultural machinery transportation control flexible chassis pulse width modulation off-centered steering shaft driving and steering cooperative control |
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