Industrial automation plants crops at speed

Able to take vegetable seedlings from trays and plant them in a field at up to 20 per second, a new machine applies factory automation concepts and equipment to products that are soft and delicate, each slightly different from every other, and sometimes separate and sometimes entangled. The machine was originally conceived by three brothers in a family nursery business but it has since taken 10 years, millions of pounds, and a lot of effort by a UK manufacturer of agricultural equipment – backed by a leading maker of factory automation equipment – to bring it to market. Missing plants, or those failing to thrive, are automatically detected and healthy plants put in their place, resulting in higher crop yields. Machines are already in service in the UK and the US and point the way forward to machine processing of even the most variable and difficult to handle products. Eureka saw the machine at work in a field in Lincolnshire, planting a large field full of brassica seedlings (brassicas are vegetables such as cabbages, cauliflowers and broccoli) in a few hours, with the help of only three men: one driving the tractor and two on the back, putting trays of seedlings on the input platforms in time for telescoping pneumatic cylinders to push them into the seedling grasping and handling system. The task would have at one time required the efforts of a gang of people working over several days. Phillip Bosworth, marketing and sales director of Boston-based developer, Richard Pearson, told us that even with a modern semi-automated equipment, such a task requires plenty of labour. “It would need around 13 people on a 10-row gang – mainly to take the seedlings out of the trays,” he said. “This machine can do 20-30 acres per day, selecting four plants per second on five heads and running forward at 4miles per hour.” Bosworth added: “You have to have a very sophisticated system to be able to do this”, indicating the large industrial enclosure of computing equipment on the platform of the machine. “The system has control of the module [the plant in its piece of earth] from the moment it is picked. The Mitsubishi computer system controls every movement of the mechanism – the speed of the heads, the actuators, the braked servo motors and the picking pauses”. The company seems impressed with the parts and support they have received from Mitsubishi Industrial Automation Systems Division. Its website describes Mitsubishi as “a market leading supplier with a superb reputation for high quality, reliable components”. The modules are grown in standard rigid trays with a separate, slightly tapered square aperture for each seedling. The modules are grasped and lifted out a row at time. Four steel fingers go in and pick each module. A carbon fibre rod pushes a plastic block to open the fingers. Then as the fingers are pushed into the module, the block is retracted upwards, allowing the fingers to grip the module. “We call this our ‘positive pick’,” said Bosworth. Once it is in the pick fingers, the module is retracted from the cell. The head assembly then moves a full row of modules horizontally until it is over one of two flighted belts. The carbon fibre rods, which run in carbon fibre finger tubes, then push each module into a place between a pair of nylon flights. The head assembly then retracts vertically. While one flighted belt is being charged, the other is delivering plants, controlled by a clutch assembly, which is controlled whenever a plant without foliage is detected by the optical sensor as being absent. High forward speed of the machine is possible because one belt is charging while the other belt is feeding. The clutch assembly allows a maximum speed of 12 plants per second. Within a given row of plants – if planting four plants per second – it is possible to make up for up to three dead cells or plants without foliage. This is important for growers because present practice is for somebody to come along after a field has been machine planted and put plants into the gaps by hand. These plants, however, having been planted later, do not grow in step with the others, causing problems later when it comes to harvesting for supermarkets. “A switchover mechanism ensures that each plant is accurately delivered from one of the flighted belts to the sweet spot between the delivery belts,” said Bosworth. “The delivery belt assembly is made up of two foam covered endless belts, which are also controlled by the computer and delivered into the ground. A strong coulter opens the soil, and as the soil flows round the back of the coulter, the plant is put in and two circular press wheels firm the plant in place.” R Fountain and Sons is a family owned company with 20 acres of glasshouse nurseries. The company started construction of its Mark 1 prototype machine in 2000, and tested it in 2001. A second Mark 2 machine was built and tested in 2002. The five-head, Mark 3 machine was able to plant over 500 acres of different brassica varieties in 2003 in a variety of soil conditions. In 2004, a worldwide licensing agreement was signed with a local company, Richard Pearson, which has been in business of making agricultural machinery since 1955. Bosworth told us: “In 2004, we started productionising Fountain’s prototype, and the two companies then cooperated to build two machines – which we upgraded and modified for the 2006 season. The Fountain machine did 1250 acres from 1 April to 31 July 2006. In the same year, we also shipped a machine to the USA for tomatoes. It is now working well in California and we are now receiving many strong enquiries for machines manly to plant tomatoes and brassicas.” A modem allows Pearson to monitor the performances of machines remotely and to carry out diagnostics and remote programming if required. The main moving parts need no lubrication. Entrapped dust and other material is removed by blowing down with compressed air. Pointers * System is able to handle items that are very delicate and differ slightly from each other at speeds of up to 20 per second * It brings industrial factory automation technology into agriculture