An online measurement device for grain moisture content based on frequency-sweeping microwave penetration method

Abstract

The invention discloses a cereal moisture content online measuring device based on a frequency sweeping microwave penetrating method. The cereal moisture content online measuring device comprises a microwave transmitting end, a microwave receiving end, an antenna lifting platform, a control unit and a conveyor; the microwave transmitting end and the microwave receiving end are slidably arranged ona lower half space and an upper half space of the antenna lifting platform respectively; the control unit moves a microwave antenna according to signals of a laser alignment sensor and the attenuation deviation of microwave signals to complete automatic alignment of the antenna; the optimal measurement distance and antenna distance are determined and adjusted to according to three conditions of the antenna far-field condition, the moisture content measurement result representativeness and the microwave space transmission loss reduction; the conveyor carries to-be-measured cereals to penetratethrough the measurement space formed between the microwave transmitting end and the microwave receiving end, the cereals interact with microwave frequency-sweeping signals, the optimized microwave frequency-sweeping signals are utilized for replacing signals with the single frequency to measure the cereal moisture content, the cereal moisture content information is more comprehensively obtained while multiple reflection influences are inhibited, and the measurement precision of the cereal moisture content is increased.

Description

technical field [0001] The present invention relates to grain quality detection, in particular to an on-line measurement device for grain moisture content based on frequency-sweeping microwave penetration method. The key device for high-precision on-line measurement of grain moisture content. [0002] technical background [0003] Moisture content is an important characteristic of grain, which has a great influence on its physical and chemical properties. The moisture content of grain affects its harvesting, storage, transportation, processing and other aspects, and it is also a key indicator for judging the quality of certain grains. As a new rapid non-destructive testing method, the microwave detection method can realize the rapid non-destructive detection of the moisture content of the material. The microwave penetration method allows the microwave to penetrate the grain to be tested in the form of space radiation, which can not only detect the water on the surface of the...

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Problems solved by technology

CN 200920033543.8 proposes a device for measuring the moisture content of fabrics based on changes in microwave attenuation. The device only uses microwaves of a single frequency, and does not consider reflected signals when calculating microwave attenuation, resulting in a calculated attenuation value that is greater than the actual attenuation big value

CN201710017788.0 proposes a multi-frequency microwave moisture content detection system, which uses a frequency sweep signal of 300MHz to 2.4GHz, but the detection system is aimed at liquids and is not suitable for grains

CN200910085533.3 proposes a dual-source dual-probe orthogonal microwave moisture content measurement device for coal moisture content measurement. Considering the characteristics of low-frequency microwave signals and high-frequency microwave signals, two frequencies of 2.4GHz and 9.4GHz are used. Microwave, two sets of antennas are used, the measuring device is relatively complicated, and the reflected signal is not considered when calculating the microwave attenuation, resulting in the calculated attenuation value being larger than the real attenuation value

In the current on-line measurement device of grain moisture content based on the microwave penetration method, there are not many applications of microwave frequency sweep signals. The use of frequency sweep signals can not only suppress the influence of multiple reflections, but also obtain more comprehensive grain moisture information. In addition, The alignment between the microwave transceiver antennas in the current on-line measurement device of grain moisture content based on the microwave penetration method is usually completed with simple measurement tools combined with human eye observation, and the alignment accuracy between the microwave transceiver antennas is poor. The coincidence degree of the main lobe of the antenna beam is not high, the microwave signal transmission is incomplete, and the measurement distance from the transmitting antenna to the material under test and the distance between the microwave transceiver antennas are relatively arbitrary. When the microwave antenna is used to measure the moisture content of different materials When the microwave antenna is sensitive to different positions, it is necessary to adjust the measurement distance from the transmitting antenna to the material to be tested and the distance between the receiving and transmitting antennas to an appropriate value. The measurement distance and the distance between antennas are automatically and reasonably set, and the online measurement device for grain moisture content is more comprehensively obtained grain moisture information while using frequency sweep signals to suppress the influence of multiple reflections

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