Apple of your eye

By integrating precision electric linear drives with state of the art vision systems, fruit suppliers can cut costs and save production time using intelligent robots. Dean Palmer reports A robot has been developed to take over the laborious task of packing apples for supermarkets, cutting costs by almost 60% and freeing up key workers for other vital duties at harvest time. Core to the robot’s operation is the control of precision electric linear drives via intelligent information gathered by a state of the art vision system. Because supermarkets always insist that the attractive side of an apple is displayed to the customer, buyers require suppliers to undertake this responsibility during their packing process. To date, this has meant considerable expense in packing millions of apples manually, one-by-one. But at this year’s Hanover Fair, the first credible alternative, Apfelrobo, was on display from Hoerbiga-Origa. Apfelrobo was developed in conjunction with Hermann Schuster, an Austrian company that specialises in fruit technologies. Since the Hanover Fair this year, the company has entered into series production with the robot. It is expected that 25 robots will be deployed into the firm’s logistics supply chain, with a further 50 next year. The robot itself works in several discrete stages. Apples are delivered via a conveyor and each one is individually picked up by a suction cup on a belt-driven actuator, then an air stream is used to rotate the apple until the stalk stands vertically upright. Next comes Apfelrobo’s core function: the apple is rotated through 360 degrees under the watchful eye of the vision system, which looks for the reddest area of the apple’s surface. This is determined in real time and the apple rotated back or forwards, as the apple is transferred and lowered onto the packaging pallet. For absolute perfection, the stalks of all the apples are arranged to point backwards, away from the final customers’ viewing position in the supermarket. Apfelrobo then packs the filled pallets into boxes and places them onto an exit conveyor belt to continue their journey to the high street. All movement axes are based on Hoerbiga-Origa OSP-E electric linear drives. In this case, belt Drive models are used in preference to ballscrew units since their robust construction requires minimal maintenance. The actual maintenance interval is 3,000km of travel, which the firm says is far greater than that of any comparable actuator on the market. This interval comes around remarkably quickly since the robot is likely to be working 16 or 20 hours a day, seven days a week. During development of Apfelrobo, ballscrew drives were used, but Schuster was delighted that Hoerbiger-Origa could replace these with belt units for field deployment, as simplicity of design was very attractive in an agricultural environment. Similarly, the original servo motors were replaced with stepper motors on the final design. As throughput is very high, high speed and precision was required of the drive axes. The vision system was also required to work in real time, as no delays could be tolerated. The inspection rotation of the apple, for example, the analysis to determine its best aspect and subsequent rotation to its final position, had to be undertaken in less than 500ms. The total time allowed for Apfelrobo to complete all of its functions is 2.5s per apple, so that a productivity of 300kg per hour could be maintained. This is roughly equal to the performance of a person working at their best, without stopping for breaks or slowing down due to fatigue, a target figure often used when converting a manual process into an automated one so that bottlenecks are not created further downstream. It is expected that speed increases will follow over a period of time as the industry becomes used to automation. The machine is also roughly twice as accurate as a person. Packaging costs have been cut by about euros 0.02 per kg, a saving of £4.50 per hour or up to £750 per week and gives a payback time of months rather than years.