In order to implement variable rate application control of intermittent spray based on pulse width modulation ( PWM ) technology, a blended pulse variable rate application controller was designed with its core part DSP56F805. The controller has two working modes. Operational parameters were set artificially in single mode, and received from upper computer through CAN bus in online mode. The controller can output 12 channels of PWM signal which can be adjusted individually. It also can monitor traveling speed of sprayer, rotational speed of diaphragm pump' s input shaft, spray pressure and application flow rates of each boom partition. In addition, the spray pressure can be regulated on-line by predictive control algorithm with proportional relief valve. A variable rate application system was constructed by integration of a modified commercial boom sprayer and the controller, and its performance tests were carried out. Test results showed that the maximal effective frequency of the PWM signal was within 5 Hz, the ratio of flow regulation was more than 10, measuring error was within ±0.1 km/h for the traveling speed, within ±1.5 r/min for the rotational speed, within ±0. 01 Mpa for the spray pressure and within ±0. 05 L/min for the flow rate, and regulating error of the spray pressure was within ±0. 01 Mpa in a 2 s regulating period.%为实现基于脉宽调制(PWM)间歇喷雾的流量调节式变量喷施控制,以DSP56F805数字信号控制器为核心,设计了一种PWM间歇喷雾式变量喷施控制器.控制器有单机和联机两种工作模式,可输出12路独立调节的PWM信号,实时检测喷雾机组前进速度、隔膜泵输入轴转速、喷杆压力和喷施流量,并采用预测比例控制方法,通过比例溢流阀在线调节喷杆压力.将控制器安装到一台经过改装的商购喷杆式喷雾机上,构建了一套PWM间歇喷雾式变量喷施系统,并进行了系统测试.测试结果表明:PWM信号有效频率小于等于5 Hz、流量调节范围大于10,喷雾机组前进速度检测误差在±0.1 km/h范围内、隔膜泵输入轴转速检测误差在±1.5 r/min范围内、喷杆压力检测误差在±0.01 MPa范围内、喷施流量检测误差在±0.05 L/min范围内,经2 s调节后喷杆压力调节误差在±0.01 MPa范围内.
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