Weight measurement and liquid supply control system for greenhouse horticulture.
By combining multiple load sensors with a single amplifier, the problems of complex wiring and high cost in existing technologies are solved, enabling precise weight measurement and liquid fertilizer supply in multiple cultivation units, improving measurement accuracy and noise immunity, and making it suitable for a variety of plant growth environments.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- YAMAMOTO ELECTRIC CO LTD
- Filing Date
- 2025-01-10
- Publication Date
- 2026-07-23
AI Technical Summary
In existing technologies, the use of multiple load sensors leads to complex wiring and high costs, while failing to guarantee measurement accuracy and noise immunity in large incubators, especially when the plant growth direction changes, making it difficult to achieve precise liquid fertilizer supply.
By combining multiple load sensors with a single amplifier, and through signal synthesis and digital conversion, it achieves precise weight measurement and liquid fertilizer supply control for multiple culture units. It uses RS485 signals and LoRa wireless communication to reduce wiring and equipment quantity.
It enables precise weight measurement and liquid fertilizer supply within multiple culture units, reducing system complexity and cost while improving measurement accuracy and noise immunity, and is suitable for a variety of plant growth environments.
Smart Images
Figure 2026121173000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a liquid supply control system incorporated in protected horticulture for cultivating cultivated plants placed indoors such as in a vinyl house by supplying liquid fertilizer.
Background Art
[0002] In Patent Document 1 related to the previous application of the applicant of the present application, a hydroponic cultivation device has been proposed that automatically supplies liquid fertilizer to cultivated plants planted in a large number of cultivation containers at the same time. In this hydroponic cultivation device, at least one of the containers during plant cultivation is used for measurement, and the decrease in the weight of this container is treated as the decrease in liquid fertilizer. When the decrease becomes less than or equal to a threshold value, liquid fertilizer is supplied, and an appropriate amount of liquid fertilizer can be supplied at the proper timing that should originally be supplied.
Prior Art Documents
Patent Documents
[0003] <0上記の容器のように一部を重量計測用に取り出すことはできない。
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] By the way, in hydroponic cultivation of strawberries and the like, a cultivation tank for storing a culture medium is made inside a vinyl house using a frame and sheets extended above it, and a part cannot be taken out for weight measurement like the above-mentioned container. Therefore, a weight measuring device will be installed on the lower side of the cultivation tank. A load cell is in circulation as a weight measuring device, and it is desirable to use this if possible. However, if only one load cell is installed on the lower side of the cultivation tank, since the cultivation tank is an elongated rectangle when viewed from above, the cultivation tank is likely to sway in the length direction like a weathervane, and the measurement accuracy of the weight cannot be ensured.
[0005] On the other hand, if multiple load cells, at least two, are installed on the underside of the cultivation tank, the lifting balance is improved, making the cultivation tank less likely to sway in the length direction. However, the number of load cells increases proportionally to the number of wires. Typically, multiple cultivation tank systems are set up along the rows inside a greenhouse, resulting in a lot of wiring. Furthermore, since each load cell is equipped with its own amplifier, the number of amplifiers increases with the number of load cells. As a result, the number of components increases, making the overall system more complex and increasing its cost.
[0006] Furthermore, supplying the correct amount of liquid fertilizer at the right time requires measurement in 1g increments. However, when using the world standard analog instrumentation signal of 4-20mA, the signal resolution is limited to 1 / 35,000 for typical equipment. For a pot (with about one plant), the total weight is about 5kg, so the resolution becomes 1 / 5,000, providing approximately 7 times the margin of resolution (= margin of measurement error), allowing for practical weight measurement results. However, for a cultivation tank (with multiple plants), the total weight is about 20kg, so sufficient margin of resolution cannot be secured. Moreover, changing the analog instrumentation signal from a current signal to a voltage signal results in inferior noise immunity.
[0007] Furthermore, even when measuring the weight of a cultivation pot, if the direction of growth of the cultivated plant is shifted horizontally, the pot is suspended from above with a hook, requiring weight measurement from both the top and bottom. Therefore, the same problems as described above arise.
[0008] This invention addresses the above-mentioned problems of the conventional methods and aims to provide a novel and useful weight measurement and liquid supply control system for greenhouse horticulture that measures the weight of cultivation tanks, etc., using multiple load cells, without requiring additional wiring or amplifiers to correspond to the arrangement of load cells, while ensuring noise immunity and sufficient resolution. [Means for solving the problem]
[0009] The present invention has been made to achieve the above objective, and is a weight measurement and control system for greenhouse horticulture comprising a master unit including a controller that controls the supply of liquid fertilizer by controlling the opening and closing of a liquid fertilizer supply line that supplies liquid fertilizer to a system consisting of multiple cultivation units arranged in a row, and a slave unit connected to a plurality of load cell type weight measuring devices that are connected to the master unit in a signal transmission manner and measure the weight of a portion selected from the plurality of cultivation units, wherein in response to an inquiry from the master unit, the slave unit amplifies the total output voltage of each load cell of the plurality of load cell type weight measuring devices with a single amplifier, converts it into a digital weight signal according to its resolution with a converter, and further synthesizes the analog temperature signal with the digital temperature signal and transmits it to the master unit as a multi-signal.
[0010] Preferably, a slave unit is installed for each of the multiple systems, and each slave unit transmits a combined signal including an identification signal, while the master unit is equipped with a slave unit identifier. Preferably, the master unit consists of a receiver, a slave unit identifier, and a controller, and the slave unit consists of a load cell amplifier, a temperature conversion transmitter, and a programmable signal conversion synthesizer. In response to an inquiry from the master unit, the slave unit synthesizes a weight signal corresponding to the sum of the output voltages of multiple load cells and an instrumentation signal corresponding to the increase / decrease current of the temperature sensor, and further adds a system identification signal before transmitting it to the master unit as a multi-signal. The master unit identifies the slave unit and processes the received multi-signal without demodulating it into an analog signal. Preferably, data is transmitted from the slave unit to the master unit via wired RS485 signals or wirelessly via LoRa (including WAN) signals using low-power radio.
[0011] When a weight measurement and control system for greenhouse horticulture is incorporated into a hydroponic cultivation system using cultivation tanks, multiple load cell-type weight measuring devices support and lift one cultivation tank in a horizontal position. When incorporating a weight measurement and control system for greenhouse horticulture into a cultivation pot type hydroponic cultivation system, multiple load cell type weight measuring devices are used to support one or more cultivation pots from below while also suspending them from above. [Effects of the Invention]
[0012] According to the present invention's weight measurement system for greenhouse horticulture, weight is measured using multiple load cells, but it can be constructed as a practical system that ensures noise immunity and sufficient resolution without requiring additional wiring or amplifiers to accommodate the arrangement of each load cell. Therefore, by using one of the multiple cultivation tanks arranged in a row to form a single system for weight measurement, the timing of liquid fertilizer supply for a single system can be accurately determined. The same applies to cultivation pots with the top of the cultivated plants suspended. It is also possible to apply this to multiple systems using a common controller. Although the above issues are described with a focus on hydroponics, the weight measurement system of the present invention can be used in any system that measures weight using multiple load cells, and therefore the application of the weight measurement and control system of the present invention extends to greenhouse horticulture in general. [Brief explanation of the drawing]
[0013] [Figure 1] This is a schematic plan view of the inside of a greenhouse of a cultivation tank type hydroponic cultivation apparatus incorporating a weight measurement and control system for facility horticulture according to an embodiment of the present invention. [Figure 2] Figure 1 is a side view of the cultivation tank used for weight measurement. [Figure 3] Figure 1 shows the wired electrical configuration diagram of the connection between the slave and master units of the weight measurement and control system for greenhouse horticulture. [Figure 4] This is an electrical configuration diagram of another example of a slave unit. [Figure 5] This is a schematic side view of a cultivation pot type hydroponic cultivation apparatus incorporating a weight measurement system for greenhouse horticulture according to an embodiment of the present invention. [Figure 6] Unlike Figure 3, this is an electrical configuration diagram for a wireless type. [Modes for carrying out the invention]
[0014] Hereinafter, an example of a facility horticulture weight measurement and control system according to an embodiment of the present invention incorporated in a hydroponic cultivation device 1 of a cultivation tank type will be described according to the drawings. FIG. 1 is a schematic plan view of a hydroponic cultivation device 1 of a cultivation tank type for hydroponic cultivation of strawberries installed inside a greenhouse. Inside the greenhouse, a plurality of rectangular cultivation tanks 3 are arranged in a row and extend in a long strip shape to form one system. As shown in FIG. 2, the cultivation tank 3 is configured by coco bag (registered trademark) cultivation using coconut coir as a medium, and a rectangular coco bag 7 is placed on a styrofoam base 5. Three holes are opened on the upper surface of the bag of the coco bag 7, and the medium is exposed there. The tip of a liquid fertilizer supply pipe 9 attached to the tip of a liquid fertilizer supply tube 8a branched from a liquid fertilizer supply tube 8 is inserted into the medium. A solenoid valve 11 is connected to the liquid fertilizer supply tube 8, and this solenoid valve 11 is operated to open and close. This solenoid valve 11 opens and closes according to a command from a controller (PLC) 13. The cultivation tank 3 is lifted and supported from the ground by a gantry 15. A plurality of systems are provided inside the greenhouse, and in this embodiment, four systems are installed parallel to each other.
[0015] For weight measurement, one cultivation tank 3 is used as a weight measurement cultivation tank 3A for each system, and a facility horticulture weight measurement system is incorporated in the hydroponic cultivation device 1 of the cultivation tank type. In the cultivation tank 3A for weight measurement, a pair of load cell type weight measurement devices 17, 17 are arranged between the floor board 16 provided on the styrofoam base 5 and the coco bag 7 at intervals in the length direction. The case of the load cell type weight measurement device 17 is in the shape of a flat square box, and the pair of load cell type weight measurement devices 17, 17 are arranged symmetrically in the front-back, left-right directions with respect to the cultivation tank 3A for weight measurement. The cultivation tank 3A for weight measurement is lifted horizontally by the pair of load cell type weight measurement devices 17, 17. The cultivation tank 3A for weight measurement is physically separated from the other cultivation tanks 3, 3,....
[0016] Fig. 3 shows the detailed electrical configuration of the weight measurement system for protected horticulture. In the load cell type weight measurement devices 17, 17, the weight sensing means is constituted by load cells 19 respectively. The electrical resistance value of the strain gauge adhered to the strain body increases or decreases, causing a change in electrical resistance. This change in electrical resistance is taken out as a weak output voltage that changes between the terminals of the Wheatstone bridge circuit. When distinguishing between the pair of load cell type weight measurement devices 17, 17, they are referred to as load cell type weight measurement devices 17A, 17B. A thermistor 21 is also provided in the load cell type weight measurement device 17B as a temperature sensor. This thermistor 21 is provided to compensate for the error factor due to temperature included in the output voltage of the load cell 19, and is measured as an increasing or decreasing current. Note that the temperature sensor may be constituted by a resistance temperature detector or a thermocouple instead of the thermistor 21.
[0017] The load cell 19 in the load cell type weight measurement device 17A and the load cell 19 in the load cell type weight measurement device 17B are connected by signal lines so that signals merge. Reference numeral 23 indicates a housed box type slave unit. It is provided on the load cell type weight measurement device 17B side, and the total output voltage of the output voltage of the load cell 19 in the load cell type weight measurement device 17A and the output voltage of the load cell 19 in the load cell type weight measurement device 17B, and the increasing or decreasing current from the thermistor 21 are input to the slave unit 23.
[0018] In the load cell amplifier 25 within the slave unit 23, the output voltage mV / V from the strain gauges 19 is amplified and then converted into a weight signal (digital signal (serial RS-232C)). In addition, the temperature conversion transmitter 27 amplified the increasing / decreasing current from the thermistor 21 and converted into an instrumentation signal (4-20mA). The signal conversion synthesizer (hybrid converter) 29 functions as a multiplexer signal conversion communication device. Its internal program combines the input weight signal and instrumentation signal, adds a system identification signal, and then converts it into an RS485 signal conforming to RS485 standards, which is then output.
[0019] Since the slave unit 23 is installed in each system according to the above configuration, weight information and temperature information, along with system identification information, can be provided to the controller 13 for each system. On the other hand, the controller 13 is equipped with a serial port (RS485 compatible) 31 as a receiver, enabling direct exchange of RS485 signals with the slave unit 23. The signal lines on the slave units 23, 23, 23, and 23 are connected, and there are two signal lines between them and the master unit controller 13. The controller 13 also includes a slave unit identifier (multiplexer communication device) 33, which allows it to identify the slave unit 23 based on the received identification information.
[0020] The weight measurement and control system for greenhouse horticulture is configured as described above. The controller (with built-in microcontroller) 13 controls the entirety of each of the four cultivation tank-type hydroponic cultivation systems 1. According to the set program, it opens and closes the solenoid valve 11 connected to the nutrient solution supply tube 8 based on the appropriate weight that changes from flowering to fruit growth and just before harvest, thereby supplying nutrient solution. By incorporating a weight measurement system for greenhouse horticulture, the controller 13 sequentially queries slave units 23 (No. 1), 23 (No. 2), 23 (No. 3), and 23 (No. 4) by changing the identification number of each slave unit 23 in order to determine the timing of liquid fertilizer supply for each system. When a slave unit 23 receives its own identification number (No.), it responds by sending back its weight information, temperature information, and identification information as a signal. In response to this response, if the controller 13 determines that the current weight has decreased below the appropriate weight, it supplies liquid fertilizer to the system related to that slave unit 23 to replenish the amount of the decrease.
[0021] As described above, the weight measurement system for greenhouse horticulture is incorporated into the cultivation tank type hydroponic cultivation system 1, and two load cells 19, 19 are installed for each system, but only one load cell amplifier 25 is needed, which is installed on the slave unit 23 side. Furthermore, the signal lines from the slave units 23, 23, 23, and 23 merge and connect to the serial port 31 of the controller (master unit) 13, so the wiring does not increase and only one port is needed. Therefore, the amount of wiring and materials used in its construction does not increase unnecessarily, preventing the system from becoming overly complex or expensive.
[0022] Analog signals are transmitted between load cell weight measuring devices 17A and 17B, and between load cell weight measuring device 17B and the slave unit 23, but because they are in close proximity, signal degradation is minimal. Furthermore, if the load cell amplifier 25 is configured with 24-bit resolution, the signal resolution becomes 1 / 16,777,216. Since the total weight of cultivation tank 3 (containing multiple plants) is about 20 kg, a margin of approximately 800 times the resolution is achieved. Furthermore, the controller 13 processes the digital signal directly without demodulating it back into an analog signal, resulting in reduced conversion errors. In addition, since signals conforming to the global standard RS485 specification are transmitted between the slave unit 23 and the master unit controller 13, it has high noise immunity and is less susceptible to noise interference.
[0023] Another characteristic is that the nutrient solution supply is controlled independently for each system. For example, if the planting system extends east-west, the system closest to the south will receive the most direct sunlight, while the systems further north will be in the shade. Therefore, the northernmost system will be in the shadiest position. Consequently, there will be differences in the growth of the strawberries in each system, but it is possible to provide the optimal nutrient solution according to their growth stage. Furthermore, even if the types of plants cultivated are changed for each system, or the cultivation periods are staggered, it is possible to achieve optimal nutrient solution supply according to the growth conditions of each system.
[0024] As shown in Figure 4, other electrical configurations are also possible within the slave unit 23. In Figure 4(a), the temperature conversion transmitter 27 has been eliminated. In the above embodiment, the system consists of a total of three devices: the load cell amplifier 25, the temperature conversion transmitter 27, and the signal conversion combiner 29. By eliminating the temperature conversion transmitter 27, the total number of devices is reduced to two, resulting in cost reduction and a reduction in device errors. The temperature conversion transmitter 27 is relatively easy to implement in software on the signal conversion combiner 35, making it an easily adoptable component. In Figure 4(b), the load cell amplifier 25 is further reduced and implemented in software in the signal conversion synthesizer 37. By integrating all the functions of the load cell amplifier, temperature measurement, and identification number assignment, further cost reductions and mitigation of errors in individual devices can be achieved.
[0025] Next, an example of a weight measurement and control system for greenhouse horticulture according to an embodiment of the present invention, incorporated into a cultivation pot type hydroponic cultivation device 47 suitable for tomatoes and the like, will be described with reference to Figure 5. A load cell type weight measuring device 17B is positioned between the frame 49 and the bottom surface of the cultivation pot 51. Hooks for connecting are provided on the top and bottom surfaces of the load cell type weight measuring device 17A. One end of a wire 53 is connected to the stem of a tomato planted in the cultivation pot 51, and the other end is connected to the bottom surface of the load cell type weight measuring device 17A. Another wire 55 is stretched across the greenhouse, and the hook on the top surface of the load cell type weight measuring device 17A is slidably connected to this wire 55.
[0026] Initially, the stems can be guided straight upwards, but if the stems grow further and can no longer be guided upwards, the wire 55 will need to be shifted horizontally to guide them. When the plants can be guided straight upwards, the entire weight is supported by the load cell type weight measuring device 17B, allowing for accurate weight measurement using only the load cell type weight measuring device 17B. However, when the plants are guided horizontally, the cultivation pot 51 is supported in two places, making accurate weight measurement impossible with only the load cell type weight measuring device 17B on the lifting side. However, since the load cell type weight measuring device 17A is positioned on the suspension side, accurate weight measurement is possible using the same mechanism as for measuring the weight of the cultivation tank 3.
[0027] Although embodiments of the present invention have been described in detail above, the specific configuration is not limited to the embodiments described above, and any design changes that do not depart from the spirit of the present invention are also included in the invention. For example, the specific electrical configuration and component specifications of a weight measurement and control system for greenhouse horticulture can be changed as long as the expected functions of the present invention are ensured. Furthermore, in the above embodiment, the slave unit 23 and the master unit controller 13 are connected via a wired connection for the global standard RS485. However, as shown in Figure 6, wireless units (UART modules) 39 and 41 may be connected, and transmission may be performed using the LoRa (including WAN) protocol utilizing low-power radio. [Explanation of symbols]
[0028] 1…Cultivation tank type hydroponic cultivation system 3...Cultivation tank 3A...Cultivation tank for weight measurement 5…Styrofoam base 7…Coco bag 8... Liquid fertilizer supply tube 8a... Liquid fertilizer supply tube 9…Liquid fertilizer supply pipe 11…Solenoid valve 13…Controller 15…Mounting stand 16…Base plate 17A, 17B…Load cell type weight measuring device 19...Load cell 21...Thermistor 23...Slave unit 25...Load cell amplifier 27...Temperature conversion transmitter 29...Signal conversion combiner 31…Serial port 33…Slave device identifier 35... Signal conversion and combining device 37... Signal conversion and combining device 39... Wireless unit 41... Wireless unit 47…Cultivation pot type hydroponic cultivation system 49…Stand 51…Cultivation pot 53... Wire 55... Wire
Claims
1. The system comprises a master unit including a controller that controls the opening and closing of a liquid fertilizer supply line that supplies liquid fertilizer to a system consisting of multiple cultivation units arranged in a row, and a slave unit connected to the master unit so as to be able to transmit signals and connected to multiple load cell type weight measuring devices that measure the weight of a portion of the multiple cultivation units selected from the system. A weight measurement and control system for greenhouse horticulture, characterized in that, in response to an inquiry from the master unit, the slave unit amplifies the total output voltage of each load cell of a plurality of load cell type weight measuring devices with a single amplifier, converts it into a digital weight signal according to its resolution with a converter, and further synthesizes an analog temperature signal before transmitting it to the master unit as a multi-signal.
2. In the weight measurement and control system for greenhouse horticulture described in claim 1, Multiple slave units are installed for each system, and each slave unit transmits a combined signal including its identification signal. A weight measurement and control system for greenhouse horticulture, characterized in that the master unit is equipped with a slave unit identification device.
3. In the weight measurement and control system for greenhouse horticulture described in claim 2, The master unit consists of a receiver, a slave unit identifier, and a controller. The slave unit consists of a load cell amplifier, a temperature conversion transmitter, and a programmable signal conversion synthesizer. The slave unit, in response to an inquiry from the master unit, synthesizes a weight signal corresponding to the total output voltage of multiple load cells and an instrumentation signal corresponding to the increase / decrease current of the temperature sensor, and further adds a system identification signal before transmitting it to the master unit as a multi-signal. The aforementioned master unit is characterized by identifying the slave unit and processing the signal without demodulating the received multi-signal into an analog signal, and is a weight measurement and control system for greenhouse horticulture.
4. In the weight measurement system for greenhouse horticulture described in claim 3, A weight measurement and control system for greenhouse horticulture, characterized by transmitting signals from a slave unit to a master unit via wired RS485 signals or wirelessly via LoRaWAN signals using low-power radio.
5. In a weight measurement and control system for greenhouse horticulture as described in any one of claims 1 to 4, A weight measurement and control system for greenhouse horticulture, characterized in that the cultivation section consists of cultivation tanks, and multiple load cell type weight measuring devices support and lift one cultivation tank in a horizontal position.
6. In a weight measurement and control system for greenhouse horticulture as described in any one of claims 1 to 4, A weight measurement and control system for greenhouse horticulture, characterized in that the cultivation section consists of cultivation pots, and multiple load cell type weight measuring devices support one or more cultivation pots from below while also supporting them from above by suspending them.