  This paper proposes a coordinate-free controller for a nonholonomic vehicle
to circumnavigate a fully-actuated moving target by using range-only
measurements. If the range rate is available, our Proportional Derivative
(PD)-like controller has a simple structure as the standard PD controller,
except the design of an additive constant bias and a saturation function in the
error feedback. We show that if the target is stationary, the vehicle
asymptotically encloses the target with a predefined radius at an exponential
convergence rate, i.e., an exact circumnavigation pattern can be completed. For
a moving target, the circumnavigation error converges to a small region whose
size is shown proportional to the maneuverability of the target, e.g., the
maximum linear speed and acceleration. Moreover, we design a second-order
sliding mode (SOSM) filter to estimate the range rate and show that the SOSM
filter can recover the range rate in a finite time. Finally, the effectiveness
and advantages of our controller are validated via both numerical simulations
and real experiments.
