Application Note: Why apple harvesters need angle sensors
The Fruit Harvesting division of SFM Technology Limited (Somerset, UK) is widely recognized as one of the world's leading designers and manufacturers of advanced fruit-harvesting machines. Its SFM Samurai is a self-propelled apple harvester that collects fallen fruit and is widely used in the cider production industry.
With its 800-mm pick-up head, the multi-operational machine clears a passage between rows of apple trees and scoops up the fruit, which is cleaned and stored in an integral 3-ton-capacity hopper. A powerful blower cleans the row by propelling any missed fruit to the next row. With the capability to harvest up to 100 tons of apples each day, the machine is designed for optimal navigation through the narrowest of orchard rows thanks to its SFM-developed four-wheel steering system, which relies on Novotechnik RFC4800 series angle sensors, supplied by Variohm EuroSensor, to monitor each axle position to ensure complete front- and rear-wheel synchronization.
NovoTechnik RFC4800 angle sensors feature "touchless" contact technology and offer a practically unlimited operational life.
Novotechnik's RFC4800 series "touchless technology" non-contacting angle sensors are well proven for steering-position feedback on agricultural machinery and other mobile machinery applications. Its widespread use also extends to cost-effective rotary position feedback tasks in construction equipment, industrial and automation technology, and medical engineering. The robust and durable sensor features a 12-bit resolution (0.09 degrees) in a compact two-part design comprising a position marker (in the form of an encapsulated magnet that is typically attached to a rotating shaft component) and separate and fixed sensor electronics encased in an environmentally sealed housing.
The wear-free and completely "touchless" sensor offers a practically unlimited operational life, and with no bearings required and no need for mechanical couplings, installation is straightforward.
The RFC4800's compact dimensions suit space-restricted areas, and the separate magnet and sensor arrangement is less sensitive to axial and radial alignment tolerances and can also operate through non-magnetic materials if required -- allowing uncomplicated mechanical interfacing. Furthermore, with the sensor's absolute position output signal and the permanently fixed alignment between magnet and sensor, there is no need for elaborate calibration on setup or a need to reset the steering position on start-up or when restoring power to the vehicle.
The RFC4800 series is available in single-channel or multichannel versions with dual redundant output. Nominal sensor electronics housing dimensions are around 48-mm diameter x 14-mm thickness with 38-mm PCD mounting, while a choice of optional encapsulated magnet housings are nominally 28-mm diameter and 15-mm thick. Other magnet options include bolts, separate magnets, and shaft adaptors.
A wide choice of output signal options includes voltage, current, and ratiometric as well as fieldbus interfaces for CAN and SAEJ1939, IO-Link, SSI, and SPI. Environmental sealing can be specified for IP67 or IP69, and the sensor's generous operational temperature extends to -40 C to 105 C.
Learn more at www.novotechnik.com/Rotary-Touchless/touchless-rotary.html.
Published April 2020
Rate this article