避障区域判断调整，最小距离可变

ArduCopter/zr_flight.cpp

@@ -186,7 +186,13 @@ void Copter::do_avoid_action(){
 uint8_t Copter::avoid_area_detect(float dist)
 {
     static Proxy_Area area = PROXY_OUTRANGE;
-    if(dist < avoid.get_zr_avd_min()){
+    static int8_t min_dist;
+    if(area == PROXY_OUTRANGE){
+        min_dist = 15;
+    }else{
+        min_dist = avoid.get_zr_avd_min();
+    }
+    if(dist < min_dist){
         if(area != PROXY_TOO_CLOSE && area != PROXY_FIND_BARRIER){  // 前一个状态不是障碍物过近
             area = PROXY_OUTRANGE;
         }else{