PID control loop

Scenario

The standard closed-loop PID block diagram appears in every control systems textbook (Ogata, Franklin, Åström) and every control system design spec sheet. Schematex renders it from a signal-flow description — not a generic flowchart — using proper summing junction symbols and automatic feedback routing.

Annotation key

• block("label") [role: ...] — transfer function block; role: controller and role: plant affect visual styling
• sum(+r, -y) — summing junction: adds the +r (reference) signal and subtracts the -y (output feedback)
• signal("label") — named signal node
• G -> err — the feedback path: plant output y routes back to the summing junction

How to read

The setpoint r enters the summing junction err, which subtracts the plant output y to compute the error signal. The PID controller C(s) processes the error and drives the plant G(s). The plant output y is both the system output and the feedback signal. The loop is closed when G -> err feeds y back to the summing junction.