Open loop versus closed loop

Try it in the current lab

Pin the closed-loop run. Switch to Open loop at 7 V without changing any other setting, then open Control effort. Pin that run too and compare at the same replay time.

Compare speed and applied voltage before and after the 4 s load. Both runs start from rest, use a 100 rad/s comparison target, and share the same motor and persistent 0.04 N·m load event.

The lab recalculates after a setting changes. Pin a run before changing one variable; the response and control-effort plots share the same replay time. PID experiments also show the P/I/D terms; estimator experiments show measured and estimated states.

What the system is doing

A held 7 V matches 100 rad/s for this nominal unloaded motor. After the load arrives, open-loop speed falls toward 77.14 rad/s because the voltage does not react. The feedback preset raises voltage toward 8.6 V and recovers the target. Other parameters or voltage limits can change recovery.

Connect the design method

This open-loop exercise holds a manual voltage; measured speed never changes that command. The target stays on the graph as a comparison line. At 7 V the nominal unloaded motor approaches 100 rad/s. A 0.04 N·m shaft load at 4 s lowers its equilibrium to about 77.14 rad/s. The feedback preset can supply the extra 1.6 V and recover 100 rad/s. Pin both modes and compare speed and applied voltage. Open-loop control can also use a scheduled input in general; holding voltage is the specific example here.