Plant microgravity simulation method based on buoyancy disturbance double-shaft rotation and gravity center following

Abstract

The invention discloses a plant microgravity simulation method based on buoyancy disturbance double-shaft rotation and gravity center following, and relates to the technical field of space life science, and the method comprises the following steps: constructing a random buoyancy disturbance double-shaft rotation microgravity control algorithm and a plant growth gravity center following algorithm; importing an algorithm into a device control system; a device control system is used for plant microgravity simulation. According to the method, microgravity regulation and control are carried out by adopting a random buoyancy disturbance double-shaft rotation microgravity control algorithm, disturbance to actual gravity is increased through double-factor coupling of buoyancy and rotating speed, and the adverse effect of the rotating speed on physiology of plants is reduced; gravity center displacement control is performed by adopting a plant growth gravity center following algorithm, so that the gravity center of the plant is always located at the position of a rotating shaft, and the problem of non-uniform microgravity simulation caused by non-uniform centripetal force of a rotating cultivation surface growing along with the plant is avoided; the simultaneous application of the two algorithms improves the microgravity simulation effect, improves the fitting reproduction precision, and prolongs the culture time.

Description

Technical Field

[0001] The present application relates to the field of space life science technology, and in particular to a plant microgravity simulation method based on buoyancy perturbation dual-axis rotation and center of gravity following. Background Art

[0002] Cultivation in simulated microgravity is a preliminary experiment for meeting the requirements of plant cultivation and establishing closed ecosystems in extraterrestrial environments (such as space stations and the Moon). The accuracy of microgravity simulation determines the accuracy of plant variety selection, growth and physiological data estimation, and cultivation method selection in the early stages of space experiments. It is also a key criterion for evaluating the feasibility of terrestrial microgravity simulation systems and methods.

[0003] The ground simulation methods of microgravity environment for plant cultivation or physiological experiments can be divided into four categories: 1. Rotation method, which is the most important long-term growth cultivation simulation method, and can be specifically divided into (1) uniform rotation, (2) random rotation, and (3) differential rotation. According to the number of rotation axes, it can be divided into single-axis, double-axis, and three-axis rotation. Among them, the single-axis, uniform / differential speed condition method can eliminate the gravity vector, but cannot reproduce microgravity. The latest technology uses the RPM random rotation method, that is, random acceleration rotation along the XY axis or XYZ axis. The speed and direction will be randomly adjusted according to the set time frequency. This method has acceleration force participating in the elimination of the gravity vector and partially meets the fitting microgravity conditions. 2. Magnetic levitation method, which uses a strong magnetic field environment to offset the geomagnetic gravity. It has physiological hazards to organisms and is expensive. It is mainly used for the verification of short-term or space cultivation methods and equipment. 3. Parabolic or drop tower method: This method effectively recreates microgravity, capable of reaching 10-5g, but with a shorter simulation time. Large transport aircraft perform parabolic flights, with a maximum duration of 4 minutes. 4. Immersion suspension method: The specific principle is similar to the RCCS system. This method uses non-adherent rotary suspension culture for plant and animal cells and is not suitable for terrestrial plants.

[0004] In the prior art, Chinese patent CN119262350A discloses a rotator and method for simulating the microgravity effect on plants, comprising: a main box and a movable light source. The main box comprises: multiple groups of modules spliced ​​in series, each of which is provided with a plurality of clamps, which are used to place plant culture containers and drive the plant culture containers to rotate; the movable light source is arranged on the front side of the main box and has an adjustable distance relative to the main box to provide light for plant samples.

[0005] Chinese patent CN101726426A discloses a method for evaluating a microgravity dual-axis cyclotron. The method includes a motion calculation method for the dual-axis cyclotron and motion graph visualization. The method primarily utilizes projected cyclotron motion trajectories and calculates real-time data. However, this method is only applicable to the calculation and evaluation of dual-axis cyclotrons and cannot simulate complex random motion processes involving calculations larger than two axes (such as three axes or linear motion in space). This differs from the fitting calculation method described in this application.

[0006] Chinese patent CN 111439401 A discloses a microgravity simulation device and method based on electromagnetic ejection. The method provides a microgravity simulation device comprising: a drop tower, a guide rail, a tray, a linear motor, and a control module. The guide rail is used to constrain the movement of the tray and provide a mounting position for the linear motor. The tray is used to provide support for the drop tower to achieve acceleration during ejection and deceleration during recovery. The linear motor is used to generate electromagnetic force and propel the tray to accelerate the drop tower during the electromagnetic ejection phase, and propel the drop tower and tray together. During the drag-free control phase, only the tray is propeld. The drop tower provides a vacuum environment for the instrument under test and shields the magnetic field interference introduced by the permanent magnet on the tray and the linear motor. However, this method uses the linear motor as a controllable upgrade of the drop tower method and cannot better simulate the microgravity environment in real time.

[0007] In summary, among the above-mentioned existing technologies, the electromagnetic catapult or drop tower method has a short recurrence time and continuously simulates an environment with changing gravitational acceleration. The dual-axis rotation method does not change the actual gravity, and the plants under the influence of the rotating axis grow on the rotating surface due to the uneven centripetal force, which leads to uneven simulated force. As a result, the microgravity simulation effect is poor and the cultivation time is short. Summary of the Invention

[0008] The present application provides a plant microgravity simulation method based on buoyancy perturbation dual-axis rotation and center of gravity following, which is used to solve the problems of existing plant microgravity simulation technology continuously simulating an environment with changing gravitational acceleration, and the uneven simulated force caused by the uneven centripetal force when plants grow on the rotating surface under the influence of the rotating axis, resulting in poor microgravity simulation effect and short cultivation time.

[0009] On the one hand, the present application provides a plant microgravity simulation method based on buoyancy perturbation dual-axis rotation and center of gravity following, comprising the following steps: Step 1: Construct a random buoyancy disturbance dual-axis rotation microgravity control algorithm and a plant growth center of gravity following algorithm.

[0010] Step 2: Import the random buoyancy disturbance dual-axis rotation microgravity control algorithm and the plant growth center of gravity following algorithm into the device control system.

[0011] Step three, using the device control system to simulate plant microgravity.

[0012] The device control system includes: a microgravity control system, a center of gravity displacement control system, and an environmental control system.

[0013] The microgravity control system is configured to perform microgravity control using the random buoyancy disturbance dual-axis rotation microgravity control algorithm.

[0014] The center of gravity displacement control system is configured to: perform center of gravity displacement control using the plant growth center of gravity following algorithm.

[0015] The environmental control system is configured to regulate plant cultivation environmental parameters.

[0016] In one possible implementation, the random buoyancy perturbation dual-axis rotation microgravity control algorithm includes: A random buoyancy dual-axis rotation model is established under the dual-factor coupling of random buoyancy and random rotation speed.

[0017] The random buoyancy biaxial rotation model is used to fit the curve of net force changing with time or position.

[0018] The buoyancy fluctuation, rotation speed and direction are dynamically adjusted according to the change curve with the set time change frequency.

[0019] A genetic algorithm is run to optimize the dynamic adjustment process to minimize the objective function, obtain the optimal control path for buoyancy fluctuation, rotation speed and direction, and perform microgravity control based on the optimal control path.

[0020] In a possible implementation, fitting a curve of net force changing with time or position using the random buoyancy dual-axis rotation model includes: Generate samples of the Z-axis position changes caused by buoyancy fluctuations based on an assumed random distribution.

[0021] For each sample, the vector sum of the buoyancy disturbance acceleration force, the centripetal force in two directions, and the gravitational acceleration is calculated to obtain the net force corresponding to each sample.

[0022] Generate a dynamic fitting function based on the acceleration calculation that changes with time.

[0023] According to the net force corresponding to each sample, the curve fitting method is used to fit the curve of the net force changing with time or position, and the gravity minimization adjustment is performed according to the dynamic fitting function.

[0024] In a possible implementation, for each sample, calculating the vector sum of the buoyancy disturbance acceleration force, the centripetal forces in two directions, and the gravitational acceleration to obtain the net force corresponding to each sample includes: For each sample, the centripetal force in the x-axis and y-axis directions is calculated as a function of time frequency.

[0025] Considering the change of centripetal force, random fluctuation of buoyancy is introduced, and the vector sum of buoyancy disturbance acceleration force, centripetal force in two directions and gravitational acceleration is calculated to obtain the net force corresponding to each sample.

[0026] In a possible implementation, the plant growth center following algorithm includes: Establish a plant growth model.

[0027] The L-system plant growth algorithm is used to calculate the plant gravity center of the plant growth model, and a displacement change curve of the plant gravity center as the plant grows is drawn.

[0028] The displacement of the cultivation platform is controlled according to the displacement change curve so that the center of gravity of the plant is always at the position of the rotation axis.

[0029] In a possible implementation, the calculating the plant gravity center of the plant growth model using the L-system plant growth algorithm and drawing a displacement curve of the plant gravity center as the plant grows includes: The plant morphology of the plant growth model is generated using an L-system plant growth algorithm.

[0030] The plant center of gravity of the plant growth model is calculated according to the plant morphology, and a displacement change curve of the plant center of gravity as the plant grows is drawn.

[0031] In a possible implementation, calculating the plant center of gravity of the plant growth model according to the plant morphology includes: The stem weight, stem center of gravity, leaf weight and leaf center of gravity of the plant are obtained according to the plant morphology.

[0032] The plant center of gravity of the plant growth model is calculated according to the stem weight, the stem center of gravity, the leaf weight, and the leaf center of gravity, and a displacement change curve of the plant center of gravity as the plant grows is drawn.

[0033] The plant microgravity simulation method based on buoyancy perturbation dual-axis rotation and center of gravity following in this application has the following advantages: By employing a random buoyancy perturbation dual-axis rotational microgravity control algorithm for microgravity regulation, the dual-factor coupling of buoyancy and rotational speed reduces the adverse physiological effects of rotational speed on plants. Buoyancy fluctuations create a real-world gravity disturbance during cultivation, improving microgravity simulation. By employing a plant growth center-of-gravity following algorithm for center-of-gravity displacement control, the center of gravity of the plant is consistently positioned at the axis of rotation, avoiding the uneven shear force on the rotating surface under the influence of the axis, which can lead to uneven microgravity simulation. The simultaneous application of these two algorithms enhances microgravity simulation and prolongs cultivation time by reducing the rotator speed as the plant approaches the axis of rotation. The gravitational acceleration of the drop tower perturbation generated by random buoyancy is used to offset the gravity of the cultivated plant and the rotating system. The adiabatic properties of underwater operation and random buoyancy are utilized to reduce the effects of air convection and shear force on the plant during cultivation, providing simulation conditions for low-gravity environments such as the Moon and Mars. The invention solves the problem of uneven centripetal force caused by the increase of the center of gravity of plants in the existing three-dimensional rotating microgravity simulation device, thereby reducing the system error caused by plant growth and better simulating microgravity for plant cultivation. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0035] Figure 1 A schematic flow chart of a plant microgravity simulation method based on buoyancy perturbation dual-axis rotation and center of gravity following provided in an embodiment of the present application; Figure 2 Schematic diagram of the principle of the random buoyancy perturbation dual-axis rotation microgravity control algorithm provided in an embodiment of the present application; Figure 3 A schematic diagram of the principle of the plant growth center of gravity following algorithm provided in an embodiment of the present application; Figure 4 A schematic diagram of the control principle of the device control system provided in an embodiment of the present application; Figure 5 A schematic diagram of gravity disturbance under buoyancy fluctuation provided in an embodiment of the present application; Figure 6 This is a time-varying fitting diagram of the speed and direction corresponding to the 5-10s speed direction change frequency provided in the embodiment of the present application; Figure 7 This is a time-varying fitting diagram of the speed and direction corresponding to the 10-20s speed direction change frequency provided in the embodiment of the present application; Figure 8 A fitting diagram of the relationship between acceleration and speed in the XYZ three-axis directions provided in an embodiment of the present application; Figure 9 A graph showing the displacement of the center of gravity as the plant grows, provided in an embodiment of the present application; Figure 10 This is a schematic diagram of the plant morphology and plant center of gravity results provided in the examples of this application. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0037] like Figure 1 As shown, the embodiment of the present application provides a plant microgravity simulation method based on buoyancy perturbation dual-axis rotation and center of gravity following, comprising the following steps: Step 1: Construct a random buoyancy disturbance dual-axis rotation microgravity control algorithm and a plant growth center of gravity following algorithm.

[0038] Step 2: Import the random buoyancy disturbance dual-axis rotation microgravity control algorithm and the plant growth center of gravity following algorithm into the device control system.

[0039] Step three, using the device control system to simulate plant microgravity.

[0040] The device control system includes: a microgravity control system, a center of gravity displacement control system, and an environmental control system.

[0041] The microgravity control system is configured to perform microgravity control using the random buoyancy disturbance dual-axis rotation microgravity control algorithm.

[0042] The center of gravity displacement control system is configured to: perform center of gravity displacement control using the plant growth center of gravity following algorithm.

[0043] The environmental control system is configured to regulate plant cultivation environmental parameters.

[0044] like Figure 2 FIG. 1 is a schematic diagram showing the principle of a random buoyancy perturbation dual-axis rotation microgravity control algorithm. Exemplarily, the random buoyancy perturbation dual-axis rotation microgravity control algorithm includes: A random buoyancy dual-axis rotation model is established under the dual-factor coupling of random buoyancy and random rotation speed.

[0045] The random buoyancy biaxial rotation model is used to fit the curve of net force changing with time or position.

[0046] The buoyancy fluctuation, rotation speed and direction are dynamically adjusted according to the change curve with the set time change frequency.

[0047] A genetic algorithm is run to optimize the dynamic adjustment process to minimize the objective function, obtain the optimal control path for buoyancy fluctuation, rotation speed and direction, and perform microgravity control based on the optimal control path.

[0048] Exemplarily, the using the random buoyancy dual-axis rotation model to fit the curve of net force changing with time or position includes: Generate samples of the Z-axis position changes caused by buoyancy fluctuations based on an assumed random distribution.

[0049] For each sample, the vector sum of the buoyancy disturbance acceleration force, the centripetal force in two directions, and the gravitational acceleration is calculated to obtain the net force corresponding to each sample.

[0050] Generate a dynamic fitting function based on the acceleration calculation that changes with time.

[0051] According to the net force corresponding to each sample, the curve fitting method is used to fit the curve of the net force changing with time or position, and the gravity minimization adjustment is performed according to the dynamic fitting function.

[0052] Exemplarily, for each sample, calculating the vector sum of the buoyancy disturbance acceleration force, the centripetal forces in two directions, and the gravitational acceleration to obtain the net force corresponding to each sample includes: For each sample, the centripetal force in the x-axis and y-axis directions is calculated as a function of time frequency.

[0053] Considering the change of centripetal force, random fluctuation of buoyancy is introduced, and the vector sum of buoyancy disturbance acceleration force, centripetal force in two directions and gravitational acceleration is calculated to obtain the net force corresponding to each sample.

[0054] Specifically, the parameter requirements for plant microgravity simulation are: g≤10 -3 (0.001m / s²).

[0055] In this embodiment, the rotational speed is defined as follows: ω = 1.38951 × 10 2 (L0t) -1 / 3Where ω represents the optimal rotational speed (r / min), L0 represents the distance from the plant sample to the rotating axis (cm), which varies with the height of the plant sample during cultivation and is equal to half of the height. Assuming L0 = 0 to 17 cm, the maximum growth height of the cultivation chamber is 34 cm. t represents the cultivation time (s). Assuming the minimum cultivation time is 5.5 h, then t = 5.5 h to +∞. 0 ≤ ω ≤ 1.998 r / min = 0.0333 r / s.

[0056] The speed is set to 0 to ±2, the precise speed fluctuation is 0.1r, the response time is 0.1s, and the maximum angular acceleration a=1.05r / s 2 .

[0057] In this implementation case, the Z-axis height and acceleration change are defined as follows: H = H0 + △H t .

[0058] Among them, H represents the height of the device after displacement, H0 represents the initial height, △H t Indicates displacement height.

[0059] Note: The changes in submerged volume are not included in the microgravity fitting calculation for plants inside the cultivation chamber.

[0060] In this embodiment, the acceleration force generated by buoyancy fluctuation is defined as follows: F b =mW.

[0061] Where m represents mass and W represents buoyancy fluctuation acceleration.

[0062] Because the gravity calculation formula F g =mg, so it can be regarded as the disturbance of W on g.

[0063] It is necessary to consider the influence of centripetal force and random buoyancy changes in the vertical direction on the gravity induction of plants, establish a random buoyancy dual-axis rotation model under the dual-factor coupling of random buoyancy and random speed, and perform force analysis as follows: the net force F on the plant net =F b +F c -F g Among them, F c represents the centripetal force, F g Represents gravity.

[0064] Numerical simulation: Through numerical simulation, we generate samples of acceleration changes and position changes caused by convection according to the assumed random distribution. We calculate the net force F corresponding to each sample. net .

[0065] The specific steps for fitting the curve of net force changing with time or position using the random buoyancy biaxial rotation model are as follows: For each calculation sample, calculate the centripetal force F in the x-axis direction cx and the centripetal force F in the y-axis direction cy : The centripetal force in the x-axis direction is F cx =m·ω x 2 ·r x .

[0066] The centripetal force in the y-axis direction is F cy =m·ω y 2 ·r y .

[0067] Among them, ω x and ω y are the angular velocities of the plant in the x-axis and y-axis directions, r x and r y They are the distances from the plant's two end points to the center of rotation in the x-axis and y-axis directions (half the growth height).

[0068] Consider the change in centripetal force: If the plant's angular velocity or distance changes over time, the centripetal force will also change. Introduce a time variable to describe these changes. For example: Angular velocity in the x-axis direction: ω x (t)=ω x0 +△ω x (t).

[0069] Angular velocity in the y-axis direction: ω y (t)=ω y0 +△ω y (t).

[0070] Distance in the x-axis direction: r x (t)=r x0 +△r x (t).

[0071] Distance along the y-axis: r y (t)=r y0 +△r y (t).

[0072] Among them, ω x0 and ω y0 They represent the initial angular velocity in the x-axis and y-axis directions, r x0 and r y0 Represents the initial distance in the x-axis direction and the y-axis direction, △ω x (t) and Δω y (t) represents the fluctuation of angular velocity in the x-axis direction and the y-axis direction over time, △r x (t) and △ry (t) represents the fluctuation of the distance in the x-axis direction and the y-axis direction over time.

[0073] Introducing random buoyancy fluctuations: F b (t)=F b0 +△F b (t).

[0074] Among them, F b0 represents the initial buoyancy, △F b (t) represents the fluctuation of buoyancy over time.

[0075] Calculate the resultant force F total As shown in the following formula: .

[0076] If the plants inside the closed chamber are not subject to liquid buoyancy (non-submerged state), the random motion generated by water convection will cause a disturbance of one degree of freedom in the vertical direction of the dual-axis rotation system. The mechanical analysis is as follows: Introducing random displacement perturbation: In the simulated microgravity environment, the random up and down displacement perturbation is achieved by introducing a random displacement vector in the inner ring coordinate system. Assume that the displacement vector .

[0077] Where dx(t), dy(t), and dz(t) are the random displacement components that change with time in the x-axis direction, y-axis direction, and z-axis direction, respectively.

[0078] Based on the assumed random distribution, samples of acceleration change △d(t) and position change △r(t) caused by convection are generated. The perturbation displacement is as follows: .

[0079] Where r(t) is the position vector of the object before the disturbance, and r'(t) is the position vector after the disturbance.

[0080] Build a mathematical model: Assume that the acceleration change △d(t) and position change △r(t) caused by convection are random, and use a random process to describe these changes. Assume that △d(t) and △r(t) follow a random distribution (such as a normal distribution).

[0081] In this embodiment, a random buoyancy dual-axis gyroscope model is constructed using MATLAB. The cosine matrix of the known dual-axis gyroscope is calculated as follows: Assume the base coordinate system OXYZ, the outer rotation ring: O'X'Y'Z', the inner rotation ring: O"X"Y"Z", the outer ring rotation angle θ, the inner ring rotation angle .

[0082] Then the cosine matrix of the direction between the outer ring and the base is: .

[0083] The cosine matrix of the direction between the inner ring and the outer ring is: .

[0084] The cosine matrix of the direction between the inner ring and the base is: .

[0085] Assume that the acceleration due to gravity in the base coordinate system is: g=[0,0,-g] T .

[0086] The component of gravitational acceleration on the inner ring coordinate axis is: .

[0087] Introduce random buoyancy fluctuations into the model: .

[0088] W represents the acceleration force caused by the fluctuation of buoyancy on the cultivation chamber.

[0089] The component of buoyancy on the inner ring coordinate axis is: .

[0090] The real-time net force is calculated as follows: .

[0091] Dynamic function calculation: The effect of disturbance on apparent acceleration is as follows: The disturbance displacement is as follows: .

[0092] Where r(t) is the position vector of the object before the disturbance, and r'(t) is the position vector after the disturbance.

[0093] The effect of disturbance on apparent acceleration is as follows: Real-time acceleration calculation: After considering random displacement disturbances, the apparent acceleration A' of the object is the gravitational acceleration g and the centripetal fitting acceleration a generated by the rotation of the inner and outer rings. d And the vector sum of the acceleration W due to random displacement disturbance: .

[0094] By taking the second-order time derivative of the displacement vector d(t), we can obtain: .

[0095] The calculation method of the acceleration vector generated in real time on three axes is: Outer loop acceleration calculation: .

[0096] Inner loop acceleration calculation: .

[0097] Calculation of random disturbance acceleration generated by buoyancy fluctuation: .

[0098] In the above formula, A outer , A inter , A disturb Respectively represent the X-axis angular acceleration, Y-axis angular acceleration, and Z-axis disturbance acceleration values, is the angle between the gravity axis disturbance and the X-axis, α is the rate of change of angular acceleration caused by the outer ring rotation, and β is the rate of change of angular acceleration caused by the inner ring rotation.

[0099] Fitting calculation of the apparent gravity acceleration vector of the experimental chamber during dual-axis rotation: .

[0100] Right now: .

[0101] The calculation formula for the apparent gravity acceleration vector in a two-axis gyrator is: .

[0102] Right now: .

[0103] Calculate the time derivative of gravitational acceleration: .

[0104] Update the calculation method of rotation angular velocity and angular acceleration: Calculate the acceleration fitting value required for fitting the rotational angular acceleration under Z-axis acceleration disturbance to microgravity in real time: .

[0105] Where A z is the fitting value of biaxial angular acceleration and z-axis acceleration W z,i is the component of the Z-axis disturbance acceleration in the inner ring coordinate system.

[0106] X-axis apparent acceleration: .

[0107] Apparent acceleration on the Y axis: .

[0108] Apparent acceleration on the Z axis: .

[0109] By taking the derivative of each component and inserting it into the above derivative formula, we can get the total function expression of time displacement acceleration fitting microgravity: .

[0110] Adjust the parameters of the random buoyancy biaxial rotation model, including the buoyancy fluctuation acceleration d(t), the liquid level fluctuation height △H t , and adjust the inner ring speed ω1 and outer ring speed ω2.

[0111] The buoyancy fluctuation, speed and direction are dynamically adjusted according to the change curve of the net force over time or position.

[0112] The magnitude of the buoyancy fluctuation acceleration is randomly generated with time / s and liquid level height, and the speed and direction are dynamically adjusted and changed once every 5-10s or 10-20s.

[0113] The dynamic adjustment process is optimized using the existing genetic algorithm (GA) to minimize the objective function (minimize the g value) and obtain the optimal control path for buoyancy fluctuation, rotation speed and direction.

[0114] like Figure 3 FIG. 1 is a schematic diagram showing the principle of a plant growth center-of-gravity following algorithm. Exemplarily, the plant growth center-of-gravity following algorithm includes: Establish a plant growth model.

[0115] The L-system plant growth algorithm is used to calculate the plant gravity center of the plant growth model, and a displacement change curve of the plant gravity center as the plant grows is drawn.

[0116] The displacement of the cultivation platform is controlled according to the displacement change curve so that the center of gravity of the plant is always at the position of the rotation axis.

[0117] Exemplarily, the calculating the plant gravity center of the plant growth model by using the L-system plant growth algorithm and drawing a displacement curve of the plant gravity center as the plant grows includes: The plant morphology of the plant growth model is generated using an L-system plant growth algorithm.

[0118] The plant center of gravity of the plant growth model is calculated according to the plant morphology, and a displacement change curve of the plant center of gravity as the plant grows is drawn.

[0119] Exemplarily, calculating the plant center of gravity of the plant growth model according to the plant morphology includes: The stem weight, stem center of gravity, leaf weight and leaf center of gravity of the plant are obtained according to the plant morphology.

[0120] The plant center of gravity of the plant growth model is calculated according to the stem weight, the stem center of gravity, the leaf weight, and the leaf center of gravity, and a displacement change curve of the plant center of gravity as the plant grows is drawn.

[0121] Specifically, in this embodiment, the plants are planted on a liftable cultivation platform (with a lifting range of 95-210 mm) in the cultivation chamber. When the plants are planted, the cultivation platform is at the highest point and 200 mm from the axis (the height of the planting chamber is 400 mm ÷ 2). Then, according to the growth height of the plants, the cultivation platform is gradually moved down so that the center of gravity of the plants is always at the position of the rotation axis. The water supply and light continuously guide the growth direction of the plants to avoid the situation where the growth direction of the plants is different from the lifting direction.

[0122] In this embodiment, the plant growth model is established as follows: the center of gravity of the plant changes with the growth height, which is represented by the function h(t), t is the growth time, and the displacement ∆h(t) is: ∆h(t)=h(t)-h0.

[0123] Where h0 represents the initial height of the plant.

[0124] Growth rate and center of gravity adjustment: The growth rate of plants in a microgravity environment may change, and its specific form needs to be determined through experimental data. Assume that the relationship between growth rate v(t) and time t is: .

[0125] The growth height is obtained by integration: .

[0126] Correcting for microgravity yields: .

[0127] where μ is the microgravity correction factor.

[0128] According to the plant morphology, the stem weight, stem center of gravity, leaf weight, and leaf center of gravity of the plant are as follows: .

[0129] .

[0130] .

[0131] r 叶,i (t)=r 茎 (t)+r 相对叶,i .

[0132] Among them, m 茎 (t) is the accumulation of stem weight over time, L is the stem length, D is the stem diameter, ρ 茎 is the relative density of the stem, r 茎 (t) represents the unit time growth vector of the stem (corresponding to the center of gravity of the stem), Represents the vector along the z axis. Where m 叶,i (t) is the accumulated weight of the i-th leaf over time, A i (t) is the function of the area of ​​the i-th leaf changing with time, r 相对叶,i is the geometric center position of the i-th leaf relative to the stem (i.e., the leaf centroid of the i-th leaf).

[0133] The plant center of gravity of the plant growth model is as follows: .

[0134] The displacement values ​​(one-dimensional single stem height direction x) are as follows: .

[0135] Among them, m i represents the mass of the i-th particle, x i represents the position of the i-th mass point. The height of the cultivation platform after displacement is x' = x-x0. x0 represents the initial height of the cultivation platform.

[0136] In this embodiment, the established plant growth model is a lettuce growth model.

[0137] Table 1 shows the growth time comparison table of lettuce: Table 1. Comparison table of lettuce growth time

[0138] Set the initial parameters of the plant growth model: stem density: 0.5 kg / m³, leaf density: 0.1 kg / m³, initial stem length: 0.005 m, initial stem diameter: 0.001 m, initial number of leaves: 2, initial leaf area: 0.00001 m 2 , stem growth rate: 0.01m / day, leaf growth rate 0.00001 m 2 / day, culture days: 30d.

[0139] The L-system plant growth algorithm is used to calculate the plant center of gravity of the plant growth model, and the displacement curve of the plant center of gravity as the plant grows is drawn.

[0140] The displacement of the cultivation platform is controlled according to the displacement change curve so that the center of gravity of the plant is always at the position of the rotation axis.

[0141] like Figure 4As shown, the device control system in this embodiment includes: a microgravity control system, a center of gravity displacement control system, and an environmental control system.

[0142] The microgravity control system includes a water pump variable frequency controller and a motor servo controller. The pump variable frequency controller is connected to a z-axis accelerometer, ultrasonic level sensor, outlet pump, inlet pump, booster pump, and drain solenoid valve. The calculated random buoyancy fluctuations are fed into the pump variable frequency controller. The motor servo controller is connected to a nine-axis angular accelerometer, x-axis servo motor, and y-axis servo motor. The calculated centripetal force fitting and the genetic algorithm are fed into the motor servo controller. The x-axis and y-axis servo motors are used to regulate the random speed and direction of rotation.

[0143] The center of gravity displacement control system includes a screw stepper controller, which is connected to the cultivation platform and is used to control the displacement of the cultivation platform. In this embodiment, the lettuce growth time height model (i.e., plant growth model), initial data and rate, and the calculation results of the L-system plant growth algorithm all act on the screw stepper controller.

[0144] The environmental control system includes a timer, a temperature and humidity controller, and a CO2 concentration controller. The timer is used to control the lighting time, water supply time, and necessary air circulation time. The temperature and humidity controller is connected to a temperature and humidity sensor to control the buoyancy tank heating, air tank heating and cooling, atomization humidification, and additional air supply and ventilation. The CO2 concentration controller is connected to a CO2 concentration sensor to replenish CO2 to the air tank.

[0145] like Figure 5 Shown is a schematic diagram of gravity disturbance under buoyancy fluctuation.

[0146] Figure 6 This is the time variation fitting diagram of speed and direction corresponding to the 5-10s speed direction change frequency. Figure 6 The upper left sub-figure is the time change fitting diagram of the rotation speed of the x-axis, the upper right sub-figure is the time change fitting diagram of the rotation speed of the y-axis, the lower left sub-figure is the time change fitting diagram of the direction of the x-axis, and the lower right sub-figure is the time change fitting diagram of the direction of the y-axis.

[0147] Figure 7 This is the time variation fitting diagram of speed and direction corresponding to the speed direction change frequency of 10-20s. Figure 7 The upper left sub-figure is the time variation fitting diagram of the rotational speed of the x-axis, the upper right sub-figure is the time variation fitting diagram of the rotational speed of the y-axis, the lower left sub-figure is the time variation fitting diagram of the direction of the x-axis, and the lower right sub-figure is the time variation fitting diagram of the direction of the y-axis (shown are 100s data captured during continuous operation).

[0148] Figure 8This is a fitting diagram of the relationship between acceleration and speed in the XYZ three-axis directions, making the fitting value of each surface infinitely close to 9.8m / s².

[0149] Figure 9 The graph shows the displacement change of the center of gravity as the plant grows. It can be seen that as the number of days increases, the center of gravity of the plant moves along with the rise of the stem.

[0150] Figure 10 This is a schematic diagram of plant morphology and plant gravity center results, where the red circle represents the plant gravity center and the blue represents the simulated gravity points of various parts of the plant as the stems and leaves grow.

[0151] After calculation and simulation verification, the plant microgravity simulation method based on buoyancy perturbation dual-axis rotation and center of gravity following in this application can achieve a speed and direction switching frequency of 10-20s (comprehensive result: 0.0001136<g<0.001), which is slower than the frequency of previous dual-axis rotators and has less damage to the rotation of plants.

[0152] The gravity fitted by the plant microgravity simulation method based on buoyancy perturbation dual-axis rotation and center of gravity following in this application (comprehensive result: 0.0000396<g<0.000156) is g<0.00016 at a frequency of 5-10s, which is much smaller than 10 -3 , with a better microgravity simulation effect, and the buoyancy provides a buoyancy environment for all mechanical structures. The disturbance of gravity by liquid fluctuations actually changes the gravity exerted on plants in the vertical direction. The test results are more meaningful than those of traditional rotators, and the frequency of rotational acceleration and rotational direction change is further reduced, and the impact of rotation on plants is further reduced.

[0153] The embodiment of the present application adopts a random buoyancy perturbation dual-axis rotation microgravity control algorithm to perform microgravity regulation, and realizes real-time gravity changes through the dual-factor coupling of random buoyancy and rotation speed; the minimization result of the fitting function by the genetic algorithm is further improved, and the center of gravity displacement is controlled by adopting the plant growth center of gravity following algorithm, so that the center of gravity of the plant is always at the position of the rotation axis, avoiding the problem of uneven shear force on the rotating surface under the influence of the rotation axis, which leads to uneven microgravity simulation and reduces the adverse physiological effects of rotation on plants; the simultaneous application of the two algorithms jointly improves the microgravity simulation effect and prolongs the cultivation time. Specifically, when the buoyancy perturbation is involved, the fitted gravity acceleration is at the lowest value, and the rotator speed value is reduced. The random buoyancy generated by the drop tower perturbs the gravitational acceleration, which helps offset the gravity of the cultivated plants and the rotating system. The thermal insulation and random buoyancy of underwater work reduce the effects of air convection and air shear on the plants during cultivation, further simulating the confined space environment under microgravity and providing simulation conditions for low-gravity simulations on the moon and Mars. This solves the problem of uneven centripetal force caused by the elevated center of gravity of plants in existing three-dimensional rotating microgravity simulation devices, thereby reducing the systematic errors caused by plant growth and facilitating better simulation of microgravity for plant cultivation.

[0154] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present application.

[0155] Obviously, those skilled in the art may make various changes and modifications to this application without departing from the spirit and scope of this application. Thus, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalents, this application is intended to include these modifications and variations.

Claims

1. A plant microgravity simulation method based on buoyancy perturbation dual-axis rotation and center of gravity following, characterized by: The following steps are involved: Step 1: Construct a random buoyancy perturbation dual-axis rotation microgravity control algorithm and a plant growth center of gravity following algorithm; Step 2: Importing the random buoyancy disturbance dual-axis rotation microgravity control algorithm and the plant growth center of gravity following algorithm into the device control system; Step 3, using the device control system to simulate plant microgravity; The device control system includes: a microgravity control system, a center of gravity displacement control system, and an environmental control system; The microgravity control system is configured to: perform microgravity control using the random buoyancy disturbance dual-axis rotation microgravity control algorithm; The center of gravity displacement control system is configured to: perform center of gravity displacement control using the plant growth center of gravity following algorithm; The environmental control system is configured to regulate plant cultivation environmental parameters.

2. The plant microgravity simulation method based on buoyancy disturbance dual-axis rotation and center of gravity following according to claim 1 is characterized in that: The random buoyancy disturbance dual-axis rotation microgravity control algorithm includes: A random buoyancy dual-axis rotation model is established under the dual-factor coupling of random buoyancy and random rotation speed; The random buoyancy biaxial rotation model is used to fit the curve of net force changing with time or position; Dynamically adjust the buoyancy fluctuation, speed and direction change frequency over a set time according to the change curve; A genetic algorithm is run to optimize the dynamic adjustment process to minimize the objective function, obtain the optimal control path for buoyancy fluctuation, rotation speed and direction, and perform microgravity control based on the optimal control path.

3. The plant microgravity simulation method based on buoyancy disturbance dual-axis rotation and center of gravity following according to claim 2 is characterized in that: The use of the random buoyancy dual-axis rotation model to fit the curve of net force changing with time or position includes: Generate samples of Z-axis position changes caused by buoyancy fluctuations based on the assumed random distribution; For each sample, the vector sum of the buoyancy disturbance acceleration force, the centripetal force in two directions, and the gravitational acceleration is calculated to obtain the net force corresponding to each sample; Generate a dynamic fitting function based on the acceleration calculation that changes with time; According to the net force corresponding to each sample, the curve fitting method is used to fit the curve of the net force changing with time or position, and the gravity minimization adjustment is performed according to the dynamic fitting function.

4. The plant microgravity simulation method based on buoyancy disturbance dual-axis rotation and center of gravity following according to claim 3 is characterized in that: For each sample, the vector sum of the buoyancy disturbance acceleration force, the centripetal force in two directions, and the gravitational acceleration is calculated to obtain the net force corresponding to each sample, including: For each sample, the centripetal force in the x-axis and y-axis directions is calculated as a function of time frequency; Considering the change of centripetal force, random fluctuation of buoyancy is introduced, and the vector sum of buoyancy disturbance acceleration force, centripetal force in two directions and gravitational acceleration is calculated to obtain the net force corresponding to each sample.

5. The plant microgravity simulation method based on buoyancy disturbance dual-axis rotation and center of gravity following according to claim 1 is characterized in that: The plant growth center following algorithm includes: Establish plant growth models; The L-system plant growth algorithm is used to calculate the plant gravity center of the plant growth model, and a displacement curve of the plant gravity center as the plant grows is drawn; The displacement of the cultivation platform is controlled according to the displacement change curve so that the center of gravity of the plant is always at the position of the rotation axis.

6. The plant microgravity simulation method based on buoyancy disturbance dual-axis rotation and center of gravity following according to claim 5 is characterized in that: The method of calculating the plant center of gravity of the plant growth model using the L-system plant growth algorithm and drawing a displacement curve of the plant center of gravity as the plant grows includes: generating a plant morphology of the plant growth model using an L-system plant growth algorithm; The plant center of gravity of the plant growth model is calculated according to the plant morphology, and a displacement change curve of the plant center of gravity as the plant grows is drawn.

7. The plant microgravity simulation method based on buoyancy disturbance dual-axis rotation and center of gravity following according to claim 6, characterized in that: Calculating the plant center of gravity of the plant growth model according to the plant morphology includes: Obtaining the stem weight, stem center of gravity, leaf weight, and leaf center of gravity of the plant according to the plant morphology; The plant center of gravity of the plant growth model is calculated according to the stem weight, the stem center of gravity, the leaf weight, and the leaf center of gravity, and a displacement change curve of the plant center of gravity as the plant grows is drawn.

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