  Non-equilibrium stochastic dynamics of several active Brownian systems are
modeled in terms of non-linear velocity dependent force. In general, this force
may consist of both even and odd functions of velocity. We derive the
expression for total entropy production in such systems using the Fokker-Planck
equation. The result is consistent with the expression for stochastic entropy
production in the reservoir, that we obtain from probabilities of time-forward
and time-reversed trajectories, leading to fluctuation theorems. Numerical
simulation is used to find probability distribution of entropy production,
which shows good agreement with the detailed fluctuation theorem.
