Combining our virtual force field (VFF) and vector field histogram (VFH) methods we have developed a new method, called the combined vector field (CVF). With this method, the principal steering direction is determined by the VFH algorithm, while the VFF algorithm applies virtual forces as a corrective measure (to account for the vehicle's rectangular dimensions). This way, steep force profiles with short-range effects can be used, thus avoiding the disadvantages of force field navigation.
(a) Multiple repulsive force fields are applied to multiple act-on points A_n on the periphery of the robot. All individual forces F_i,j are added at their act-on points and result in n repulsive forces F_k.
(b) Applying the principle of free-body diagrams, the moment M, caused by the repulsive forces F_k about the center point CP, can be computed. Using the VFH algorithm at CP, the principal steering direction is computed and a constant-magnitude vector F_VFH is applied in that direction.
(c) M is replaced by a force couple F_1 and F_2, acting on CP_1 and CP_2, respectively. While F_2 is discarded, F_VFH is shifted to CP_1 and added to F_1, yielding the new steering vector F_s.
(d) The Instantaneous Center of Rotation (ICR) can now be found and the velocities V_1 and V_2 of the two drive wheels are set accordingly.