What is Closed & Open Loop Simulation?

Closed-loop simulation and open-loop simulation are two types of simulations that are used to model and analyze dynamic systems.

Open-loop Simulation
In an open-loop simulation, the system is modeled and analyzed without any feedback or control. This means that the input to the system is predefined and fixed, and the output is observed. The system’s response is analyzed, but there is no attempt to control or modify it. Open-loop simulations are useful for understanding the behavior of a system under different conditions, but they do not provide any information on how to modify the system to achieve a desired response.

Examples of Open-loop Simulation:

• Replay of real-life camera logs as input streams to the controller of the vehicle.
• Simulate what happens if we send a specific control signal (defined over time) to turn the vehicle.

Closed-loop Simulation
In a closed-loop simulation, the system is modeled and analyzed with feedback and control. The input to the system is modified based on the system’s output, which is measured in real-time. The system’s response is continuously adjusted until the desired output is achieved. Closed-loop simulations are useful for designing and optimizing control systems, as they allow for the testing and evaluation of different control strategies under various conditions.
If a driver or operator of a vehicle is simulated, then the simulation can be considered closed-loop.

Examples of Closed-loop Simulation:

• Simulation of vehicle that uses it’s relative position to a road’s lane markers as input to its control logic.
• Flight simulator with a real pilot operating the simulated aircraft