Embed’s unknown and constraint blocks can be used to trim a simulation to begin at a desired non-zero point. This technique is especially useful for slow-running simulations in which the interesting region lies later in the trajectory. By trimming the conditions at the interesting region, you save time.
The initial condition of the integrator can be set externally using a summingJunction block. (The actual initial condition on the integrator is set to 0.) The goal is to drive the derivative signal to zero on the first pass of the simulation by adjusting the value of the unknown blocks, which is the integrator initial condition.