Instrumented picking bag for measuring fruit weight during harvesting

Abstract. A worker‘s picking rate during tree fruit harvesting can provide useful information for better workforce management; orchard platform crew management; yield maps (in combination with position). A commercial picking bag was instrumented to measure harvested fruit weight. Two load cells were placed inside an enclosure, which was placed between the bag and its shoulder straps, without hindering picking motions. The load cells measure the forces exerted on the straps by the bag and fruits. All electronics were placed inside the enclosure, and included an Arduino, signal conditioning circuits, an Xbee shield, a GPS, and an SD card. The microcontroller transmits data in real time and saves time-stamped data on the SD card. Data are filtered using a median and a low-pass filter to reduce noise. Dynamic calibration was performed in the lab over the weight range of the bag‘s capacity. Baseballs provided consistent weight and volume and were placed in the bag to provide a staircase ground truth weight signal. One person carried the bag and moved in a manner analogous to pickers. Results showed a root mean squared error of 0.47 kg. Major error sources included bag acceleration and body reaction force.