Thus cuckoo birds are always looking for a better place in order to decrease the chance of their eggs to be discovered. The process customer reviews can be approximated by the fraction pa of the NP nests which are displaced by new nests (with new random solutions). Consequently, it will enhance the original quality of the candidate solution. Thus, the more cuckoos a UCAV path is passed by, the bigger possibility that a path can be selected by the other cuckoos. This process can guarantee nearly all cuckoos walk along the shortest UCAV path in the end.Based on the above analysis, the pseudocode of improved CS-DE/CS for UCAV three-dimension path planning is described as follows (Algorithm 5).Algorithm 5Algorithm of DE/CS for UCAV three-dimension path planning.5.
Path-Smoothing StrategiesThe generated UCAV optimal three-dimension path using the proposed hybrid metaheuristic method DE/CS is usually hard for exact flying. There are some turning points on the optimized path [20, 21]. In this section, we adopt a class of dynamically feasible trajectory smooth strategy called B-Spline curves smoothing strategy [17]. B-Splines are adopted to define the UCAV desired path, providing at least first-order derivative continuity. B-Spline curves are well fitted in the evolutionary procedure; they need a few variables (the coordinates of their control points) in order to define complicated curved paths. Each control point has a very local effect on the curve’s shape and small perturbations in its position produce changes in the curve only in the neighborhood of the repositioned control point.
B-Spline curves are parametric curves, with their construction based on blending functions [22]. Their parametric construction provides the ability to produce nonmonotonic curves. If the number of control points of the corresponding curve is n + 1, with coordinates w0(x0, y0, z0),��, wn(xn, yn, zn), the coordinates of the B-Spline curve may be written asx(u)=��i=1nxi?Ni,p(u),y(u)=��i=1nyi?Ni,p(u),z(u)=��i=1nzi?Ni,p(u),(11)where u is the free parameter of the curve, Ni,p(u) are the blending functions of the curve, and p is its degree, which is associated with curve’s smoothness (p + 1 being its order). Higher values of p correspond to smoother curves. The blending functions are defined recursively in terms of a knot vector U = u0,��, um, which is a nondecreasing sequence of real numbers, with the most common form being the uniform nonperiodic one, defined asui={0if??i