Spray control systems are used in variety of applications, such as for applying paints and other coating compositions to plastic, metal, and optical components. In many of these applications, it is beneficial if not important to achieve a uniform thickness of coating material. Consequently, spray control systems typically utilize closed loop control to regulate the flow of coating fluid and/or fluid pressure provided to the spray gun or other applicator. These closed loop control schemes use the error between the measured flow and/or pressure and setpoints corresponding to desired flow and pressure to provide negative feedback that drives the flow toward the setpoint. PID (proportional plus integral plus derivative) control is common among these control schemes.
In other applications, such control systems may be employed in agricultural environments to regulate the application of liquids and chemicals such as water or fertilizer, to crops, plants and soil. In these applications, the spraying control system allows users to easily measure and monitor desired plant or crop characteristics such as temperature or soil density, control and modify the flow rate and pressure of the liquid or chemical being distributed, and adjust spray settings according to differing levels of plant/crop growth and activity. The capabilities afforded by such systems promote increased plant/crop production and better efficiency.
In these applications, the spray controller performs numerous logical operations based on the receipt of input information to provide overall monitoring and control of operating parameters of the system. For example, in the case of a mobile spraying system, the controller may receive various signals from input devices, such as sensors that detect system pressure, flow rate, spray application rate, and/or ground speed. Other input components may include a user keypad for entering desired setpoints, functional switches for altering application modes/settings or a barcode reader for receiving user input commands and instructions. In response to the input information, the spray controller operates in a logical fashion to provide output signals to various output components, such as flow valve actuators and the like.
The input and output components and devices interact with one another to perform the various functions of the controller under the control of a central processing unit (CPU). The CPU is capable of processing the logical instructions and/or algorithms that regulate how the components interact, and controls the overall operation of the spray system. These instructions and algorithms are stored in a programmable memory device resident within the controller circuitry or within the CPU memory directly. Commonly, the instructions/algorithms are designed using relay ladder logic and other conventional programmable logic languages.
In these known systems, the user has limited ability to modify the control and operation of the controller according to the specific requirements of his or her application. That is, while the user can alter the desired setpoints for the control system, the more intrinsic logical and procedural operations as defined by the instructions/algorithms within the controller memory cannot be directly modified. The ability of the user to accommodate spraying requirements that extend beyond the capabilities of the pre-programmed user settings/modes is impractical in most conventional spray controllers and systems.
Although the controller program code can be modified or customized for the user by the system manufacturer to meet a specific set of requirements, this level of customization can be costly to the user, especially when only small quantities of customized controllers are needed. Furthermore, users already having existing spray controllers that call for only simple modifications must either incur the expense of reprogramming the controller, or replace their existing controllers with a different one. These options are inconvenient and costly.