超声波果树冠层测量定位算法与试验

本文利用姿态航向参考系统、RTK-DGPS和超声波传感器，研究超声波果树冠层扫描时探测点在大地坐标系下的定位问题，建立了定位算法以校正车身倾斜对测量点位置计算的影响。文中考虑了车体的位置和姿态角信息以及超声波传感器安装的位置角度关系，利用一次、二次坐标转换建立算法模型，求解得到超声波探测点的绝对坐标位置。并利用农用拖拉机进行了直线行走试验和果树冠层扫描试验，其中的直线行走试验验证了校正模型的正确性。试验表明：通过姿态角和位置信息等建立的校正模型，消除了车体姿态角变化的影响，能正确解算作业车上任意点的大地坐标位置和冠层上超声波传感器探测点的大地坐标位置，使作业车辆在不平路面上工作时仍能准确地测绘出果树冠层形状。

Positioning algorithm for ultrasonic scanning of fruit tree canopy and its tests

In this paper, true geodetic coordinates of the detection point was derived using data provide by AHRS (attitude and heading reference system), RTK-DGPS and ultrasonic sensors, where position and attitude angles of the vehicle body, installation position offsets and angle offsets of ultrasonic sensors relative to the vehicle body were taken into consideration. The algorithm consisted of some coordinate transformation formula to obtain the detection points in the geodetic coordinates. Tests were conducted to examine the algorithm, including a straight line driving test on brick-scattered uneven road, which was used to verify the effectiveness of the correction model, and some field tests of tree canopies. Experimental results showed that the correction model (algorithm), which used the body attitude and position information, correctly transformed any point on the body into geodetic frame, and any point on the canopy detected by the ultrasonic sensor into geodetic frame, and ensured the true canopy shape could be measured regardless of body attitude changes and sensor installation offsets.