植保无人机精准覆盖航迹规划算法设计与验证

Design and Verification of an Algorithm of Precision Coverage Path Planning for Unmanned Aerial Vehicle

植保无人机作业航线规划中,应尽量降低无人机能耗、减少药液的浪费。为此,提出了一种航线规划算法,在保证无漏喷的前提下,基于贯穿线理论分析可知,以待作业区域边界为起始边进行作业航线规划时可获得较少转弯次数和冗余覆盖率;利用转弯区域的平行四边形理论,求解可完全覆盖作业区域的最小平行四边形,获得最小的冗余覆盖率;构建作业航线覆盖区域边界,精确计算重喷率和误喷率。基于该算法开发航迹规划软件,可自动推荐最优作业航线,也可由使用者手动选择;提出最优航线选择时应对各个目标参数加权评优,从而选择最优作业航线。算法验证结果表明:待作业区域为面积983.125m^(2)的不规则凸五边形时,将漏喷率降低至0,作业方向相同的情况下,最多减少作业过程中航线总长度39.41m,即减少15.49%作业航线总长度,获得了12.24%的最小冗余覆盖率。经过加权评分之后推荐的最优作业航线的起始作业方向为A_(4)A_(3),转弯次数为6次,作业航线总长度为240.51m,冗余覆盖率为13.47%,重喷率为5.94%,误喷率为7.53%,综合评分为4.39。

Unmanned aerial vehicles(UAV)were widely used in agriculture,especially in plant protection.Most researchers focused on the route planning of"point-to-point"mission of the UAV,the route only needed to be the optimal route from point to point.Unlike the former,research about operation route planning of"coverage"mission of the plant protection UAV was not mature,the operation route should cover the operating area completely and minimize energy consumption and waste of liquid.Therefore,this paper studied a precision coverage path planning algorithm based on reciprocating operation mode for unmanned rotorcraft that used for plant protection.The algorithm planned each possible operation route with no leakage spray,minimum total route length and minimum redundant coverage rate.Based on the analysis of the through-line theory,we could obtain less turning times and smaller redundant coverage rate when we choose the operation area boundary line to be the starting edge to do the route planning.Based on the theory of parallelogram of the turning area,we could obtain minimum redundant coverage rate by searching for the minimum parallelogram which could cover the turning area completely.After rotating the coordinate system parallel to the starting edge,coordinates of the optimal turning point could be obtained by using the positive and negative polarities of abscissa of the turning area.After finishing route planning,we could accurately calculate re-spray rate and wrong spray rate by building coverage area boundary line of the planning route.There was a nonlinear correlation between each index of evaluating operation route,so we couldn't only rely on the merits of single index to evaluate the advantages and disadvantages of the operation route.We should select the optimal operation route by weighting all the indexes.In this paper,weights of each parameters were as follows:weight of turning times was 0.3,weight of total route length was 0.2,weight of redundant coverage rate was 0.3,weight of re-spray rate was 0.1 and weight of wrong spray rate was 0.1.Based on this algorithm,a route planning software was developed,which could plan coverage operation route and recommend the optimal operation route automatically.The users also could choose the optimal operation route by themselves.The operation area used in this paper was irregular convex pentagon of 983.125 m2.Results of algorithm verification experiment shown that the leakage spray rate was reduced to 0%,the total route length was reduced by 15.49% which was 39.41m,the redundant coverage rate reached the minimum of 12.24%.After the weighted scoring,the software recommended the optimal route.The starting operation direction is,total length of the operation route is 240.51m,the redundant coverage rate is 13.47%,the re-spray rate is 5.94%,wrong spray rate is 7.53% and the comprehensive score is 4.39.Under the same heading angle,there were two different operation directions with different indexes of evaluating operation route.So different operation directions should be distinguished during the route planning.