Optimal Dynamic Control Systems in Agriculture

Most environmental control systems attempt to maintain constant input conditions i.e. temperature, humidity, gas levels etc. The constant value of the input condition (set-point) used, is determined experimentally to maximise (or minimise as appropriate) the output of the process; a task that is slow, expensive and invariably a compromise. Many input/output responses are characterised by curves with a maximum (or minimum). For instance, animals, birds, growing plants and stored fruit will not grow or store well if the temperature is too high or too low. Optimum control can be achieved with maximum (or minimum) seeking algorithms. The control system measures the output directly and dynamically changes the input conditions in order to maximise (or minimise) the output. Further extensions to the optimal control system are multi-variable and dynamic control. This allows the maintenance of maximum output in time, with a number of interacting input variables. The problem with most agricultural applications is that the output variable is difficult to measure continuously and automatically. The paper considers the principles of optimal dynamic control and explores its application in various agricultural applications.