Abstract: We propose a new rule, loop reversal, in block diagram and signal flow graph manipulation (or transformation) that leads to equivalent block diagrams or signal flow graphs from existing ones ...

GRC has a signal generator block and interfaces ... You can find a simple starter project on the video below. GRC uses a block diagram (a flow graph) to represent your project.

Mathematical models of systems and linear approximations. Transfer functions of linear systems, block diagrams and signal flow graphs. Sensitivity, control of transient response, disturbance signals.