PID controller is the most accurate

Automatic controllers can be different both on the principle of the device and the algorithm of action. They have one thing in common - they all implement feedback.

The most common type istwo-position. This is the simplest and cheapest device to maintain the desired parameter in a given range. Examples of such systems can be called many, they are used in both production and household appliances. Iron, electric heater - convector, AGV and even toilet bowl - these are the devices in which the simplest two-position scheme is applied, the principle of which is that the regulating organ (PO) is located either in one extreme position or in the other. The disadvantage of this method of controlling the output parameter is the low accuracy of regulation.

More complex proportional regulators. They generate a signal for the position of the regulating organ, depending on how much the regulated parameter has increased or decreased. There are no more than two POS provisions, it can be located at any intermediate points. Principle of operation: the more the output parameter deviates from the set value, the more the position of the regulated organ changes. The disadvantage is the presence of a static error, that is, a stable deviation from the set value of the output parameter.

To eliminate this error applyintegrated regulation. As a result, proportional-integral (PI) regulators appeared. Their disadvantage was the inability to take into account the inertia of the regulated system, its lag in relation to the control action. By the time the regulator reacts to the disturbance of the system, it is possible that the opposite effect is already needed, and negative feedback can turn into a positive one, which is highly undesirable.

The most perfect is the PID controller. It takes into account the differential component of the acceleration characteristic of the controlled parameter, that is, the rate of its change as a result of a step-like change in the position of the PO. The adjustment of the PID controller is more complicated, it is preceded by the removal of the acceleration characteristic, the determination of object parameters such as the time lag and the time constant. In addition, all three components are configured. The PID controller provides an effective stabilization of the output parameter without a static error. In doing so, it eliminates parasitic generation.

The PID controller can be executed on differentelement base. If the basis of its scheme is a microprocessor, it is often called a controller. The accuracy of maintaining the parameter is calculated on the principle of reasonable sufficiency.

It happens that the technological requirements forthe maintenance of one of the parameters is so rigid that only a PID controller can be used. An example is microbiological production, in which the thermal regime determines the quality of products. In this case, the PID temperature controller will maintain the microclimate to within 0.1 degrees or less, if, of course, the sensors are correctly mounted and the settings are calculated.