  With the development of robotics, ground robots are no longer limited to
planar motion. Passive height variation due to complex terrain and active
height control provided by special structures on robots require a more general
navigation planning framework beyond 2D. Existing methods rarely considers both
simultaneously, limiting the capabilities and applications of ground robots. In
this paper, we proposed an optimization-based planning framework for ground
robots considering both active and passive height changes on the z-axis. The
proposed planner first constructs a penalty field for chassis motion
constraints defined in R3 such that the optimal solution space of the
trajectory is continuous, resulting in a high-quality smooth chassis
trajectory. Also, by constructing custom constraints in the z-axis direction,
it is possible to plan trajectories for different types of ground robots which
have z-axis degree of freedom. We performed simulations and realworld
experiments to verify the efficiency and trajectory quality of our algorithm.
