Precision Agriculture, 4, 413±419, 2003
2003 Kluwer Academic Publishers. Manufactured in The Netherlands.
Laboratory Measurement of Mowing Machine
Material Feed Rate
Czech University of Agriculture in Prague, Technology Faculty, Department of Agricultural Machines,
Prague, Czech Republic
Abstract. The main objective of this research was to evaluate two possibilities of material feed rate
measurement of modern mowing machines equipped with conditioner. The machines are commonly used for
harvest of grasses (Lolium multiflorum, Dactylus glomerata, Phleum pratense, etc.), clover (Trifolium pratense,
etc.), alfalfa (Medicago sativa) etc.
A mowing machine with finger conditioner was equipped with an electronic measuring unit for the purpose of
our measurements. The mowing machine's conditioner shaft was supplied with strain gauges placed on a torque-
meter and with a RPM optical sensor counter. Together with torque-meter the mowing machine was equipped
with a curved impact plate mounted on the machine's material output.
It was decided to arrange a laboratory measurement to obtain information about the dependence of
conditioner power input and signals from the impact plate on material mass flow. A mixture of grass and alfalfa
was used for our measurement.
The measurements carried out proved that a very good linear relationship existed between the conditioner's
power input, output frequency of the apparatus measuring impact force by means of the impact plate, and
material feed rate through the mowing machine. The calculated coefficients of correlation were about 0.95. It is
possible to differentiate a material feed rate difference of 0.5 kg s
using both methods. This accuracy should be
sufficient for practical utilisation such as creating yield maps.
Keywords: mowing machines, feed rate measurement, conditioner, impact plate
A forage crop feed rate sensor can be useful in several applications of precision farming.
Information about the variable feed rate of forage can be used for calculating site-specific
forage crop yield for a yield map.
Flowrate measurement techniques for forage harvesters have been published
previously. Vansichen and De Baerdemaeker (1993) calculated a yield from the torque
of the harvester's blower. Another possibility is to measure the distance between feeder
rolls of the harvester (Ehlert and Schmidt, 1995). Recently Auernhammer and Demmel
(1996) measured yield by using a nuclear gauge sensor placed in the spout of a forage
harvester. A mass flow sensor for a pull type (trailed) forage harvester based on a reaction
plate in the spout was constructed and tested by Missotten et al. (1997). This sensor was
designed to be used for various crop properties (e.g. moisture, crop maturity, stand height,
stand density) and crop type.
Site-specific measurement of biomass in growing crops has been proposed as a pivoted
cylindrical body moving horizontally through a plant population (moving pendulum).
The angle of deviation of this pendulum varies with the plant properties (e.g. stand