  This paper considers collision avoidance for vehicles with first-order
nonholonomic constraints maintaining nonzero forward speeds, moving within
dynamic environments. We leverage the concept of control barrier functions
(CBFs) to synthesize control inputs that prioritize safety, where the safety
criteria are derived from the velocity obstacle principle. Existing
instantiations of CBFs for collision avoidance, e.g., based on maintaining a
minimal distance, can result in control inputs that make the vehicle stop or
even reverse. The proposed formulation effectively separates speed control from
steering, allowing the vehicle to maintain a forward motion without
compromising safety. This is beneficial for ensuring that the vehicle advances
towards its desired destination, and it is moreover an underlying requirement
for certain vehicles such as marine vessels and fixed-wing UAVs. Theoretical
safety guarantees are provided, and numerical simulations demonstrate the
efficiency of the strategy in environments containing moving obstacles.
