Define an excitation

The supported harmonic drive is DirectHarmonicExcitation. It applies

\[ \mathbf f_e(t) = \mathbf f_d \odot \boldsymbol\lambda \cos(\omega t), \]

where f_d is the modal force vector and lambdas scales it elementwise.

import jax.numpy as jnp
import poscidyn

excitation = poscidyn.DirectHarmonicExcitation(
    f_d=jnp.array([0.002, 0.0]),
    lambdas=jnp.array([1.0, 1.0]),
)

For solver.frequency_sweep(omegas), the solver supplies each drive frequency from omegas; leave omega unset. For solver.time_response(...), provide exactly one positive drive frequency when creating the excitation:

excitation = poscidyn.DirectHarmonicExcitation(
    f_d=jnp.array([0.002]),
    omega=jnp.array([1.0]),
)

f_d and lambdas must be compatible with the number of oscillator modes. Use a zero entry to leave a mode unforced.

ParametricHarmonicExcitation is present as development work, but its end-to-end solver support is not part of the supported documentation contract. See status and roadmap rather than relying on it for a production workflow.