4WID高地隙自走式电动喷雾机定速巡航控制方法

Research on constant speed cruise control of 4WID high ground clearance self-propelled electric sprayer

针对4WID高地隙自走式电动喷雾机在复杂工况下,面对来自外部道路坡度改变及内部药液喷洒带来整备质量下降,从而导致喷雾机行驶速度稳定性差、作业质量恶化等问题,在分析4WID高地隙自走式电动喷雾机结构与纵向动力学特性基础上,设计一种定速巡航分层控制算法。控制算法模型接收用户设定的期望行驶车速,经过算法计算后对纵向动力学系统模型输入加速度控制信号,实现喷雾机对期望车速的跟踪。搭建的纵向动力学系统结构主要包括5个部分:逆纵向动力学模型、加速与制动切换模型、转矩分配模型、电机模型和纵向动力学模型。通过对斜坡行驶状态下喷雾机的车身状态进行受力分析可获得其逆纵向动力学及纵向动力学模型;同时,为建立合理的四轮转矩分配策略,在喷雾机车身同时具有俯仰及侧倾的条件下进行分析,以各驱动轮的附着率作为分配依据,满足不同工况下各车轮的最佳驱动力矩,确保喷雾机动力的均衡性。模型定速巡航控制采用分层控制方法,通过建立上层PID控制及下层的模糊PID控制实现对喷雾机车速的有效跟踪,通过制定模糊控制规则,自动对下层控制器的PID参数进行整定,保证在各种复杂工况下喷雾机定速巡航系统的良好适应性。应用Matlab/Simulink建立控制模型,对控制系统进行仿真分析。试验结果表明,在典型工况下,设计的定速巡航控制系统能够有效地对喷雾机的速度进行控制。具体而言,在系统输入外部干扰及自重变化条件下,该控制系统的表现良好,超调量在2%以内,响应时间小于0.2 s,稳态误差趋于0,验证了所采用控制算法的准确性。

In response to the problems of poor speed stability and degraded spraying quality of 4WID high-clearance selfpropelled electric sprayers caused by changes in external road gradients and lowered payloads resulted from internal liquid spraying under complex operating conditions,a fixed-speed cruise control algorithm with a layered control approach is proposed based on an analysis of the structure and longitudinal dynamic characteristics of 4WID high-clearance self-propelled electric sprayers.The control algorithm model receives the user-specified desired speed and inputs acceleration control signals to the longitudinal dynamic system model through algorithmic calculation to realize the tracking of the sprayer to the desired speed.The structure of the longitudinal dynamic system mainly includes five parts:the inverse longitudinal kinematic model,the acceleration-braking switching model,the torque allocation model,the motor model,and the longitudinal kinematic model.The inverse longitudinal kinematic and longitudinal kinematic models of the sprayer can be obtained by analyzing the force on the body of the sprayer under the condition of driving on a slope.Meanwhile,in order to establish a reasonable fourwheel torque allocation strategy,the analysis is conducted under the condition that the sprayer has both pitching and tilting motions of the body,and the slip rate of each driving wheel is used as the basis for allocation,ensuring the optimal torque moment of each wheel under different operating conditions and ensuring the balanced power of the sprayer.The speed cruise control adopts a layered control approach,which realizes the effective tracking of the speed of the spraying machine through the establishment of the upper PID control and the lower fuzzy PID control.By defining fuzzy control rules,the PID parameters of the lower layer controller are automatically adjusted to ensure the good adaptability of the speed cruise control system to various complex operating conditions.A control model is established using Matlab/Simulink,and the control system is simulated and analyzed.The experimental results show that the designed speed cruise control system can effectively control the speed of the sprayer under typical operating conditions.Specifically,the performance of the system is excellent under conditions of external disturbance and self-weight variation,with overshoot less than 2%,response time less than 0.2 s,and steady-state error approaching 0,verifying the accuracy of the control algorithm used.