In PID control, I want to achieve a seamless switch from automatic to manual mode

I don’t know what system you’re using. Most DCS systems have this function integrated

In the regulator or DCS, it’s possible to switch directly from automatic to manual mode, with a seamless transition without any disruptions. I don’t quite understand what the LZ means

I use a Siemens PLC; after calling FB41 in OB35, I set the PID output value as the “manual value”. In other words, the “manual value” changes continuously in line with the “output value” in automatic mode. By selecting manual mode, FB41 will output the “manual value”, which remains the “output value” from the previous cycle. Just casually speaking, I might not have understood what the original poster was asking either, hehe

Starting with DDZ III-type instruments, the regulators (control units) enable seamless manual/automatic switching without disruption.

In PID control, there should be two disturbance-free switches: 1. the PID output and the output of the actual soft controller. The calculated output from the PID module is sent to the soft controller, and from there it is sent to the AO unit for use at the field site； When set to automatic, the input of the soft manual control is connected to the output of the PID; the PID output is calculated based on the magnitude of the deviation ； When switched to manual mode, the output of the soft controller is that of its own module; it no longer accepts the output from the PID, although the PID continues to calculate its output. At this time, if there is a discrepancy between the manual output from the manual control and the PID calculation, switching from manual to automatic mode will cause disturbances, which is a problem. Solution: In the PID module, there is usually a tracking switch that allows control of the manual/automatic signal for soft operation. When in manual mode, the output of the PID follows that of the soft operation; when in automatic mode, the soft operation follows the output of the PID. This way, the outputs of both modules remain consistent in both manual and automatic modes, thereby resolving this issue. The second disturbance is that disturbances also occur during the manual-to-automatic switch between the measured value and the set value; when in automatic mode, the measured value changes along with the set value, and there is no problem with that ； When in manual mode, the hand-automatic signal is used to make the set value change in accordance with the measured value; generally, soft manual operation modules are equipped with pins for set value tracking and a switch for toggling this tracking function ； This way, the problem can be solved, achieving a truly disturbance-free switch. :lol

The poster is using Siemens, right? It’s sufficient to use one variable address for both the PID output and the manual input, such as DB1.DBD0