Robots and vision systems handle packaged seeds
Andrew Wilson
At the end of each year, Pioneer Hi-Bred (Des Moines, IA), a supplier of hybrid corn, beans, and other crops, recalls all unsold seed, tests for spoilage, and rebags good seeds for the next selling season. Every year in the company`s Algona, IA, production facility, more than a half-million heavy bags of seeds are lifted from palettes and placed on a conveyor that leads to an automatic bag slitter where seed is reclaimed for repackaging.
To accomplish this automatically, Pioneer contracted Automated Concepts (Council Bluffs, IA) to build a vision-guided robotic placement system. Based on a M410-IWX four-axis robot with RJ-2 controller from Fanuc Robotics (Auburn Hills, MI) coupled to a SmartImage Sensor from DVT (Norcross, GA), the robot can simultaneously lift three bags, each weighing up to 65 lbs, at speeds of up to 20 bags per minute.
Because pallet loads are built by hand, they can be skewed and loosely positioned. Thus, the vision system must first determine the skew and position of the bags before they can be lifted by the robot. To do so, Automated Concepts mounted the Smart Image sensor 20 ft above the robot so that an image of all the bags on each palette could be captured in one pass. To calculate the position and possible skew of each bag, the sensor locates the Pioneer logo on each bag and the letter "N" in the Pioneer name below the logo. By comparing the orientation of these two points with the four corners of the pallet, the skew and positioning of each bag are determined.
To allow the robot handler to be correctly positioned over three bags, image coordinates must be translated into world coordinates. To accomplish this, Automated Concepts mounted a photoeye on the end of the palletizing arm and programmed the robot arm to descend until it touches the topmost layers of bags, triggering a reflective sensor. Once triggered, the top of the pallet is calculated, and, based on this height, the vision system calculates via triangulation the real-world coordinates of the bags.
Once these coordinates are determined, the SmartSensor transmits them over the sensor`s RS-232 port in a 48-character string to the robot`s controller. The robot then decides whether the bags are close enough together and if the skew is minimal enough to permit three bags to be lifted simultaneously. If not, the robot lifts one bag at a time.
Pioneer connected a laptop to the system so that the operator can see when the vision system encounters bags that are obscured by dust, wrinkles, or tears. In such cases, the operator cleans or straightens the bag so that it becomes visible to the system, or removes them by hand.
