Plant microgravity simulation method based on buoyancy disturbance biaxial rotation and center of gravity following

Abstract

The application discloses a plant microgravity simulation method based on buoyancy disturbance biaxial rotation and barycenter following, relates to the field of space life science technology, and comprises the following steps: constructing a random buoyancy disturbance biaxial rotation microgravity control algorithm and a plant growth barycenter following algorithm; importing the algorithm into a device control system; and using the device control system to carry out plant microgravity simulation. The application uses the random buoyancy disturbance biaxial rotation microgravity control algorithm to carry out microgravity regulation and control, the double-factor coupling of buoyancy and rotation speed increases disturbance to actual gravity, and the physiological adverse effects of the rotation speed on plants are reduced; the plant growth barycenter following algorithm is used to carry out barycenter displacement control, so that the barycenter of plants is always located at the rotation axis position, and the problem that the microgravity simulation is uneven due to the uneven centripetal force of the rotation cultivation surface with the growth of plants is avoided; the simultaneous application of the two algorithms improves the microgravity simulation effect, improves fitting reproduction accuracy, and prolongs the cultivation time.

Description

Technical Field

[0001] This application relates to the field of space life science technology, and in particular to a plant microgravity simulation method based on buoyancy disturbance biaxial rotation and center of gravity following. Background Technology

[0002] Simulated microgravity cultivation serves as a preliminary experiment to address the plant cultivation needs and establish closed ecosystems in extraterrestrial environments (such as space stations and the moon). The accuracy of the simulated microgravity environment determines the selection of plant varieties for space experiments, the estimation of relevant growth and physiological data, and the selection of cultivation methods. It is also an important criterion for evaluating the feasibility of ground-based microgravity simulation systems.

[0003] Ground simulation methods for microgravity environments in 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, 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 triple-axis rotation. Among them, the single-axis and uniform / differential conditions 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 rotation speed and direction will be randomly adjusted according to the set time frequency. This method has acceleration force participating in the elimination of gravity vector and partially satisfies the fitting microgravity conditions. 2. Magnetic levitation method, which uses a strong magnetic field environment to counteract geomagnetic gravity, has physiological harm 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 is an effective way to reproduce microgravity processes, reaching 10⁻⁵ g, but the simulation time is relatively short. A large transport aircraft performs parabolic flight, which can be maintained for up to 4 minutes. 4. Immersion suspension method: The specific principle is similar to the RCCS system. This method involves non-adherent rotary suspension culture of plant and animal cells, but it is not suitable for terrestrial plants.

[0004] In the prior art, Chinese patent CN119262350A discloses a rotary device and method for simulating microgravity effects in plants, including: a main body box and a movable light source. The main body box includes: multiple modules connected in series, each module being equipped with multiple clamps for placing plant culture containers and rotating them. The movable light source is located at the front of the main body box and its distance from the main body box is adjustable, for providing illumination to the plant samples.

[0005] Chinese patent CN101726426A discloses a method for evaluating a microgravity biaxial gyroscope, including a motion calculation method and motion visualization. The main method involves projecting the gyroscope's trajectory and calculating real-time data. However, this method is only applicable to the calculation and evaluation of biaxial gyroscopes and cannot simulate complex random motion processes involving more than two axes (such as triaxial or spatial linear motion). 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 catapult. The method describes a microgravity simulation device comprising: a drop chamber, a guide rail, a tray, a linear motor, and a control module. The guide rail constrains the movement of the tray and provides a mounting position for the linear motor. The tray provides support force to the drop chamber to accelerate during launch and decelerate during recovery. The linear motor generates electromagnetic force and, during the electromagnetic catapult phase, pushes the tray to accelerate the drop chamber and moves both the drop chamber and the tray together; during the drag-free control phase, only the tray moves. The drop chamber provides a vacuum environment for the instrument under test and shields it from magnetic field interference introduced by the permanent magnets on the tray and the linear motor. However, this method, utilizing the linear motor, is merely a controllable upgrade to the drop tower method and cannot better simulate the microgravity environment in real time.

[0007] In summary, among the existing technologies mentioned above, the electromagnetic catapult or drop tower method has a short reproduction time and continuously simulates an environment with changes in gravitational acceleration. The biaxial rotation method does not change the actual gravity, and the uneven centripetal force of plants growing on the rotating surface under the influence of the rotation axis leads to uneven simulated force, resulting in poor microgravity simulation effect and short cultivation time. Summary of the Invention

[0008] This application provides a plant microgravity simulation method based on buoyancy disturbance biaxial rotation and center of gravity following, which solves the problems of existing plant microgravity simulation technology continuously simulating environments with changes in gravitational acceleration, and uneven simulated force caused by uneven centripetal force when plants grow on the rotating surface under the influence of the rotation axis, resulting in poor microgravity simulation effect and short cultivation time.

[0009] On the one hand, this application provides a method for simulating plant microgravity based on buoyancy disturbance biaxial rotation and center of gravity following, including the following steps:

[0010] Step 1: Construct a random buoyancy disturbance dual-axis rotation microgravity control algorithm and a plant growth center of gravity following algorithm.

[0011] 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.

[0012] Step 3: Use the device control system to simulate microgravity in plants.

[0013] The device control system includes: a microgravity control system, a center of gravity displacement control system, and an environmental control system.

[0014] The microgravity control system is configured to use the random buoyancy disturbance dual-axis rotation microgravity control algorithm for microgravity control.

[0015] The center of gravity displacement control system is configured to use the plant growth center of gravity following algorithm for center of gravity displacement control.

[0016] The environmental control system is configured to regulate plant cultivation environmental parameters.

[0017] In one possible implementation, the random buoyancy disturbance dual-axis rotation microgravity control algorithm includes:

[0018] A biaxial rotational model of random buoyancy coupled with random rotational speed is established.

[0019] The net force variation curve with time or position is fitted using the aforementioned random buoyancy biaxial rotation model.

[0020] The frequency of buoyancy fluctuations, rotational speed, and direction changes over a set time is dynamically adjusted based on the aforementioned change curve.

[0021] The genetic algorithm is used to optimize the dynamic adjustment process to minimize the objective function and obtain the optimal control path for buoyancy fluctuation, rotation speed and direction. Microgravity control is then performed based on the optimal control path.

[0022] In one possible implementation, fitting the curve of net force variation with time or position using the random buoyancy biaxial rotation model includes:

[0023] Based on the assumed random distribution, samples of Z-axis position changes caused by buoyancy fluctuations are generated.

[0024] For each sample, calculate the vector sum of the buoyancy disturbance acceleration force, the centripetal force in two directions, and the gravitational acceleration to obtain the net force corresponding to each sample.

[0025] A dynamic fitting function is generated based on the acceleration that changes over time.

[0026] Based on the net force corresponding to each sample, a curve fitting method is used to fit the curve of net force change with time or location, and the gravity adjustment is minimized according to the dynamic fitting function.

[0027] In one possible implementation, 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:

[0028] For each sample, calculate the centripetal force in the x-axis and y-axis directions as a function of time frequency.

[0029] Considering the change in centripetal force, we introduce random fluctuations in buoyancy and calculate the vector sum of the buoyancy disturbance acceleration, the centripetal force in two directions, and the gravitational acceleration to obtain the net force corresponding to each sample.

[0030] In one possible implementation, the plant growth centroid following algorithm includes:

[0031] Establish a plant growth model.

[0032] The L-system plant growth algorithm was used to calculate the plant centroid of the plant growth model, and the displacement curve of the plant centroid as the plant grows was plotted.

[0033] 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.

[0034] In one possible implementation, the step of using the L-system plant growth algorithm to calculate the plant centroid of the plant growth model and plotting the displacement curve of the plant centroid as the plant grows includes:

[0035] The plant morphology of the plant growth model is generated using the L-system plant growth algorithm.

[0036] Calculate the plant centroid of the plant growth model based on the plant morphology, and plot the displacement curve of the plant centroid as the plant grows.

[0037] In one possible implementation, calculating the plant centroid of the plant growth model based on the plant morphology includes:

[0038] The stem weight, stem centroid, leaf weight, and leaf centroid of the plant are obtained based on the plant morphology.

[0039] The plant center of gravity of the plant growth model is calculated based on the stem weight, the stem centroid, the leaf weight, and the leaf centroid, and a curve showing the displacement change of the plant center of gravity as the plant grows is plotted.

[0040] The plant microgravity simulation method based on buoyancy disturbance biaxial rotation and center of gravity following in this application has the following advantages:

[0041] By employing a random buoyancy-perturbed 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 introduce real gravity disturbances during cultivation, improving the microgravity simulation effect. A plant growth center-of-gravity following algorithm is used for center-of-gravity displacement control, ensuring the plant's center of gravity remains at the rotation axis position, avoiding uneven microgravity simulation caused by uneven shear forces on the rotational surface due to the rotation axis's influence. The simultaneous application of both algorithms improves the microgravity simulation effect and extends the cultivation time; specifically, the rotational speed decreases as the plant gets closer to the rotation axis. The falling tower perturbation gravity acceleration generated by random buoyancy participates in counteracting the gravity between the cultivated plant and the rotating system. The thermal insulation of underwater operation and random buoyancy reduce the impact of air convection and air shear forces on plants during cultivation, and provide simulation conditions for low-gravity simulations on the Moon / Mars. This study aims to address the uneven centripetal force caused by the increased center of gravity of plants in existing three-dimensional rotating microgravity simulation devices, thereby reducing systematic errors caused by plant growth and enabling better simulation of microgravity for plant cultivation. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 A flowchart illustrating the plant microgravity simulation method based on buoyancy disturbance dual-axis rotation and center of gravity following, provided in the embodiments of this application;

[0044] Figure 2 A schematic diagram illustrating the principle of the random buoyancy disturbance dual-axis rotation microgravity control algorithm provided in the embodiments of this application;

[0045] Figure 3 A schematic diagram illustrating the principle of the plant growth centroid following algorithm provided in this application embodiment;

[0046] Figure 4 This is a schematic diagram of the control principle of the device control system provided in the embodiments of this application;

[0047] Figure 5 This is a schematic diagram of gravity disturbance under buoyancy fluctuations provided in an embodiment of this application;

[0048] Figure 6 A fitting graph of the time variation of rotational speed and direction corresponding to the 5-10s rotational speed direction change frequency provided in the embodiments of this application;

[0049] Figure 7 A fitting graph of the time variation of rotational speed and direction corresponding to the 10-20s rotational speed direction change frequency provided in the embodiments of this application;

[0050] Figure 8 This is a fitting diagram of the relationship between acceleration and rotational speed in the XYZ three-axis directions provided in an embodiment of this application;

[0051] Figure 9 A graph showing the displacement of the center of gravity as the plant grows, provided for embodiments of this application;

[0052] Figure 10 This is a schematic diagram of the plant morphology and center of gravity results provided in the embodiments of this application. Detailed Implementation

[0053] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0054] like Figure 1 As shown, this application provides a method for simulating plant microgravity based on buoyancy disturbance biaxial rotation and center of gravity following, including the following steps:

[0055] Step 1: Construct a random buoyancy disturbance dual-axis rotation microgravity control algorithm and a plant growth center of gravity following algorithm.

[0056] 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.

[0057] Step 3: Use the device control system to simulate microgravity in plants.

[0058] The device control system includes: a microgravity control system, a center of gravity displacement control system, and an environmental control system.

[0059] The microgravity control system is configured to use the random buoyancy disturbance dual-axis rotation microgravity control algorithm for microgravity control.

[0060] The center of gravity displacement control system is configured to use the plant growth center of gravity following algorithm for center of gravity displacement control.

[0061] The environmental control system is configured to regulate plant cultivation environmental parameters.

[0062] like Figure 2The diagram shown illustrates the principle of a random buoyancy disturbance-driven dual-axis rotational microgravity control algorithm. For example, the random buoyancy disturbance-driven dual-axis rotational microgravity control algorithm includes:

[0063] A biaxial rotational model of random buoyancy coupled with random rotational speed is established.

[0064] The net force variation curve with time or position is fitted using the aforementioned random buoyancy biaxial rotation model.

[0065] The frequency of buoyancy fluctuations, rotational speed, and direction changes over a set time is dynamically adjusted based on the aforementioned change curve.

[0066] The genetic algorithm is used to optimize the dynamic adjustment process to minimize the objective function and obtain the optimal control path for buoyancy fluctuation, rotation speed and direction. Microgravity control is then performed based on the optimal control path.

[0067] For example, fitting the curve of net force change with time or position using the random buoyancy biaxial rotation model includes:

[0068] Based on the assumed random distribution, samples of Z-axis position changes caused by buoyancy fluctuations are generated.

[0069] For each sample, calculate the vector sum of the buoyancy disturbance acceleration force, the centripetal force in two directions, and the gravitational acceleration to obtain the net force corresponding to each sample.

[0070] A dynamic fitting function is generated based on the acceleration that changes over time.

[0071] Based on the net force corresponding to each sample, a curve fitting method is used to fit the curve of net force change with time or location, and the gravity adjustment is minimized according to the dynamic fitting function.

[0072] For example, 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:

[0073] For each sample, calculate the centripetal force in the x-axis and y-axis directions as a function of time frequency.

[0074] Considering the change in centripetal force, we introduce random fluctuations in buoyancy and calculate the vector sum of the buoyancy disturbance acceleration, the centripetal force in two directions, and the gravitational acceleration to obtain the net force corresponding to each sample.

[0075] Specifically, the parameter requirements for plant microgravity simulation are: g ≤ 10. -3 (0.001m / s²).

[0076] In this embodiment, the rotational speed is defined as follows: ω = 1.38951 × 10 2(L0t) -1 / 3 Where ω represents the optimal rotation speed (r / min), L0 represents the distance (cm) from the plant sample to the rotating shaft, which varies with the height of the plant sample during cultivation and is equal to half the height. Let L0 = 0 to 17cm, meaning the maximum growth height in the cultivation chamber is 34cm. t represents the cultivation time (s). Let the minimum cultivation time be 5.5h, then t = 5.5h to +∞. 0≤ω≤1.998r / min = 0.0333r / s.

[0077] The rotational speed is set to 0 to ±2 rpm, with a precise rotational speed fluctuation of 0.1 r / s, a reaction time of 0.1 s, and a maximum angular acceleration a = 1.05 r / s². 2 .

[0078] In this implementation case, the Z-axis height and acceleration change are defined as follows: H = H0 + ΔH t .

[0079] Where H represents the height of the device after displacement, H0 represents the initial height, and ΔH t Indicates the displacement height.

[0080] Note: Changes in immersion volume are not included in the microgravity fitting calculations for the plants inside the cultivation chamber.

[0081] In this embodiment, the acceleration force generated by buoyancy fluctuation is defined as follows: F b =mW.

[0082] Where m represents mass and W represents buoyancy wave acceleration.

[0083] Because the gravity calculation formula F g =mg, so it can be regarded as W's perturbation of g.

[0084] The influence of centripetal force and vertical random buoyancy variations on the gravity-sensing intervention of plants needs to be considered. A biaxial rotational model of random buoyancy coupled with random rotational speed is established, and the force analysis is as follows: The net force F acting on the plant... net =F b +F c -F g Among them, F c F represents centripetal force. g It represents gravity.

[0085] Numerical simulation: Through numerical simulation, samples of the acceleration and positional changes of convection-induced disturbances are generated based on an assumed random distribution. The net force F corresponding to each sample is calculated. net .

[0086] The specific steps for fitting the curve of net force variation with time or position using a stochastic buoyancy biaxial rotation model are as follows:

[0087] For each computational sample, calculate the centripetal force F in the x-axis direction. cx Centripetal force F in the y-axis direction cy :

[0088] The centripetal force in the x-axis direction is F cx =m·ω x 2 ·r x .

[0089] The centripetal force in the y-axis direction is F cy =m·ω y 2 ·r y .

[0090] Where, ω x and ω y These are the angular velocities of the plant along the x and y axes, respectively, r. x and r y These are the distances from the two ends of the plant to the center of rotation along the x-axis and y-axis, respectively (half the growth height).

[0091] Consider the change in centripetal force: if the angular velocity or distance of the plant changes with time, the centripetal force will also change. Introduce the time variable to describe these changes. For example:

[0092] Angular velocity in the x-axis direction: ω x (t)=ω x0 +△ω x (t).

[0093] Angular velocity in the y-axis direction: ω y (t)=ω y0 +△ω y (t).

[0094] Distance along the x-axis: r x (t)=r x0 +△r x (t).

[0095] Distance along the y-axis: r y (t)=r y0 +△r y (t).

[0096] Where, ω x0 and ω y0 Let r represent the initial angular velocities in the x-axis and y-axis directions, respectively. x0 and r y0 Let Δω represent the initial distances along the x-axis and y-axis, respectively. x (t) and Δω y(t) represents the fluctuation of angular velocity in the x-axis and y-axis directions as a function of time, Δr x (t) and Δr y (t) represents the fluctuation of the distance in the x-axis and y-axis directions over time.

[0097] Introducing random buoyancy fluctuations: F b (t)=F b0 +△F b (t).

[0098] Among them, F b0 Let ΔF represent the initial buoyancy. b (t) represents the fluctuation of buoyancy over time.

[0099] Calculate the resultant force F total As shown in the following formula:

[0100] .

[0101] If the plants inside the sealed chamber are not subject to buoyancy (in a non-submerged state), the random motion generated by water convection will cause a vertical one-degree-of-freedom disturbance to the biaxial rotating system. The mechanical analysis is as follows:

[0102] Introducing random displacement perturbations: In the simulated microgravity environment, random vertical displacement perturbations are achieved by introducing random displacement vectors in the inner-loop coordinate system. Assume the displacement vector...

[0103] .

[0104] In the formula, dx(t), dy(t), and dz(t) are the random displacement components that change with time in the x-axis, y-axis, and z-axis directions, respectively.

[0105] Based on the assumed random distribution, samples of the acceleration change Δd(t) and position change Δr(t) caused by convection are generated. The perturbation displacement is as follows:

[0106] .

[0107] Where r(t) is the position vector of the object when it is undisturbed, and r'(t) is the position vector after it is disturbed.

[0108] Establish a mathematical model: Assume that the acceleration changes Δd(t) and position changes Δr(t) caused by convection are random, and use stochastic processes to describe these changes. Assume that Δd(t) and Δr(t) follow some random distribution (such as a normal distribution).

[0109] In this embodiment, a stochastic buoyancy biaxial rotation model is constructed using MATLAB. The cosine matrix of the biaxial gyroscope is calculated as follows:

[0110] Let the base coordinate system be OXYZ, the outer rotation ring be O'X'Y'Z', the inner rotation ring be O”X”Y”Z, the rotation angle of the outer ring be θ, and the rotation angle of the inner ring be θ. .

[0111] The cosine matrix of the direction between the outer ring and the base is:

[0112] .

[0113] The cosine matrix of the direction between the inner and outer rings is:

[0114] .

[0115] The cosine matrix of the direction between the inner ring and the base is:

[0116] .

[0117] Let the acceleration due to gravity in the base coordinate system be: g = [0, 0, -g] T .

[0118] The components of gravitational acceleration on the inner coordinate axis are:

[0119] .

[0120] Incorporating random buoyancy fluctuations into the model:

[0121] .

[0122] W represents the acceleration force generated by the buoyancy causing fluctuations in the cultivation bin.

[0123] The components of buoyancy on the inner ring coordinate axis are:

[0124] .

[0125] The real-time net force is calculated as follows:

[0126] .

[0127] Dynamic function calculation:

[0128] The effects of the disturbance on line-of-sight acceleration are as follows:

[0129] The disturbance displacement is as follows:

[0130] .

[0131] Where r(t) is the position vector of the object when it is undisturbed, and r'(t) is the position vector after it is disturbed.

[0132] The effects of the disturbance on line-of-sight acceleration are as follows:

[0133] 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 inner and outer ring rotations. d The vector sum of the acceleration W caused by random displacement disturbances:

[0134] .

[0135] By taking the second time derivative of the displacement vector d(t), we obtain:

[0136] .

[0137] The method for calculating the real-time generated acceleration vector along the three axes:

[0138] Calculation of outer ring acceleration:

[0139] .

[0140] Inner ring acceleration calculation:

[0141] .

[0142] Calculation of acceleration due to random disturbances caused by buoyancy fluctuations:

[0143] .

[0144] In the above formula, A outer A inter A disturb These represent the angular acceleration along the X-axis, angular acceleration along the Y-axis, and disturbance acceleration along the Z-axis, respectively. It is the angle between the gravity axis disturbance and the X-axis, α represents the rate of change of angular acceleration caused by the outer ring rotation, and β represents the rate of change of angular acceleration caused by the inner ring rotation.

[0145] Calculation of apparent gravitational acceleration vector fitting in the experimental chamber during biaxial rotation:

[0146] .

[0147] Right now:

[0148] .

[0149] The formula for calculating the apparent gravitational acceleration vector in a biaxial rotary engine:

[0150] .

[0151] Right now:

[0152] .

[0153] Formula for calculating the time derivative of gravitational acceleration:

[0154] .

[0155] Updated calculation methods for rotational angular velocity and angular acceleration:

[0156] To calculate the required acceleration fitting value for real-time microgravity under Z-axis acceleration perturbation and rotational angular acceleration:

[0157] .

[0158] In the formula A z W is the fitted value of the biaxial angular acceleration and the z-axis acceleration. z,i It is the component of the Z-axis disturbance acceleration in the inner loop coordinate system.

[0159] X-axis apparent acceleration:

[0160] .

[0161] Y-axis apparent acceleration:

[0162] .

[0163] Z-axis apparent acceleration:

[0164] .

[0165] Differentiating each component and substituting the derivative into the above formula, we can obtain the overall function expression for the time-displacement acceleration fitting the microgravity: .

[0166] The parameters of the stochastic buoyancy biaxial rotation model were adjusted, including the buoyancy fluctuation acceleration d(t) and the liquid level fluctuation height ΔH. t And adjust the inner ring speed ω1 and the outer ring speed ω2.

[0167] The buoyancy fluctuations, rotational speed, and direction are dynamically adjusted based on the curve of net force change over time or position.

[0168] The magnitude of the buoyancy fluctuation acceleration is randomly generated with time / s and liquid level height, while the rotation speed and direction are dynamically adjusted and change once every 5-10s or 10-20s.

[0169] The existing genetic algorithm (GA) is used to optimize the dynamic adjustment process to minimize the objective function (minimize the g value) and obtain the optimal control path for buoyancy fluctuations, rotational speed and direction.

[0170] like Figure 3The diagram shown illustrates the principle of a plant growth centroid following algorithm. For example, the plant growth centroid following algorithm includes:

[0171] Establish a plant growth model.

[0172] The L-system plant growth algorithm was used to calculate the plant centroid of the plant growth model, and the displacement curve of the plant centroid as the plant grows was plotted.

[0173] 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.

[0174] For example, the step of using the L-system plant growth algorithm to calculate the plant centroid of the plant growth model and plotting the displacement curve of the plant centroid as the plant grows includes:

[0175] The plant morphology of the plant growth model is generated using the L-system plant growth algorithm.

[0176] Calculate the plant centroid of the plant growth model based on the plant morphology, and plot the displacement curve of the plant centroid as the plant grows.

[0177] For example, calculating the plant centroid of the plant growth model based on the plant morphology includes:

[0178] The stem weight, stem centroid, leaf weight, and leaf centroid of the plant are obtained based on the plant morphology.

[0179] The plant center of gravity of the plant growth model is calculated based on the stem weight, the stem centroid, the leaf weight, and the leaf centroid, and a curve showing the displacement change of the plant center of gravity as the plant grows is plotted.

[0180] Specifically, in this embodiment, plants are planted in the cultivation chamber on a liftable cultivation platform (with a lifting range of 95-210mm). When the plants are planted, the cultivation platform is at its highest point and 200mm from the axis (planting chamber height 400mm ÷ 2). Then, according to the height of the plant growth, the cultivation platform is gradually lowered so that the center of gravity of the plant is always at the position of the rotation axis. Water and light continuously guide the direction of plant growth, avoiding the plant growth direction from being different from the lifting direction.

[0181] In this embodiment, the plant growth model is established as follows: Let the change of the plant's center of gravity with growth height be represented by the function h(t), where t is the growth time, and the displacement ∆h(t) is:

[0182] ∆h(t)=h(t)-h0.

[0183] Where h0 represents the initial height of the plant.

[0184] Growth Rate and Center of Gravity Adjustment: The growth rate of plants may change under microgravity conditions, and its specific form needs to be determined through experimental data. Assume the relationship between the growth rate v(t) and time t is as follows:

[0185] .

[0186] The growth height is obtained by integration:

[0187] .

[0188] After microgravity correction, we get:

[0189] .

[0190] Where μ represents the microgravity correction factor.

[0191] Based on plant morphology, the stem weight, stem centroid, leaf weight, and leaf centroid of the plant are obtained as follows:

[0192] .

[0193] .

[0194] .

[0195] r 叶,i (t)=r 茎 (t)+r 相对叶,i .

[0196] Where, m 茎 (t) represents the cumulative stem weight over time, L is the stem length, D is the stem diameter, and ρ 茎 r represents the relative density of the stem. 茎 (t) represents the stem's growth vector per unit time (corresponding to the stem's centroid). This represents the vector along the z-axis. Where m... 叶,i (t) represents 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 It is the geometric center position of the i-th leaf relative to the stem (i.e., the centroid of the i-th leaf).

[0197] The plant centroid of the plant growth model is as follows:

[0198] .

[0199] The displacement values ​​(one-dimensional single stem height direction x) are as follows:

[0200] .

[0201] Where, mi Let x represent the mass of the i-th particle. i Let x' represent the position of the i-th particle. The height of the cultivation platform after displacement is x' = x - x0. x0 represents the initial height of the cultivation platform.

[0202] In this embodiment, the plant growth model established is a lettuce growth model.

[0203] Table 1 shows the lettuce growth time control table:

[0204] Table 1. Lettuce Growth Time Comparison Table

[0205]

[0206] The initial parameters for the plant growth model are set as follows: 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 m². 2 Stem growth rate: 0.01 m / day; Leaf growth rate: 0.00001 m / day 2 / day, incubation period: 30 days.

[0207] The L-system plant growth algorithm was used to calculate the plant centroid of the plant growth model, and the displacement curve of the plant centroid as the plant grows was plotted.

[0208] 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.

[0209] like Figure 4 As 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.

[0210] The microgravity control system includes a water pump frequency converter and a motor servo controller. The water pump frequency converter is connected to a z-axis accelerometer, an ultrasonic level sensor, an outlet water pump, an inlet water pump, a booster water pump, and a drain solenoid valve. The calculated random buoyancy fluctuations are input to the water pump frequency converter. The motor servo controller is connected to a 9-axis angular acceleration sensor, an x-axis servo motor, and a y-axis servo motor. The calculated centripetal force fitting and the running genetic algorithm are both input to the motor servo controller. The x-axis and y-axis servo motors are used together to adjust the random speed and the direction of rotation.

[0211] The center of gravity displacement control system includes a lead 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 are all applied to the lead screw stepper controller.

[0212] The environmental control system includes a timer, a temperature and humidity controller, and a CO2 concentration controller. The timer is used to control the illumination time, water supply duration, and necessary air circulation duration. The temperature and humidity controller is connected to a temperature and humidity sensor and is used to control the heating of the buoyancy chamber, the heating and cooling of the air chamber, atomization humidification, and additional air supply ventilation. The CO2 concentration controller is connected to a CO2 concentration sensor and is used to supplement CO2 to the air chamber.

[0213] like Figure 5 The diagram shows a gravity disturbance under buoyancy fluctuations.

[0214] Figure 6 This is a fitting graph showing the time variation of rotational speed and direction corresponding to the frequency of rotational speed direction change over 5-10 seconds. Figure 6 The top left subplot shows the time-varying rotational speed along the x-axis, the top right subplot shows the time-varying rotational speed along the y-axis, the bottom left subplot shows the time-varying rotational speed along the x-axis, and the bottom right subplot shows the time-varying rotational speed along the y-axis.

[0215] Figure 7 This is a fitting graph of the time variation of rotational speed and direction corresponding to the frequency of rotational speed direction change over 10-20 seconds. Figure 7 The top left subplot is the time-varying rotational speed of the x-axis, the top right subplot is the time-varying rotational speed of the y-axis, the bottom left subplot is the time-varying rotational speed of the x-axis, and the bottom right subplot is the time-varying rotational speed of the y-axis (the data shown is 100 seconds of data captured during continuous operation).

[0216] Figure 8 The fitting graph of acceleration versus rotational speed in the XYZ axes is used to make the fitting value of each surface infinitely approximate 9.8 m / s².

[0217] Figure 9 The graph shows the displacement of the center of gravity as the plant grows. It can be seen that as the number of days increases, the plant's center of gravity shifts as the stem rises.

[0218] Figure 10 This is a schematic diagram of plant morphology and plant center of gravity results, where the red circle represents the plant's center of gravity and the blue circle represents the simulated gravity points of various parts of the plant as the stem and leaves grow.

[0219] Through calculation and simulation verification, the plant microgravity simulation method based on buoyancy disturbance biaxial rotation and center of gravity following proposed in this application can achieve a rotation speed and direction switching frequency of 10-20s (overall result: 0.0001136 < g < 0.001), which is slower than the frequency of previous biaxial rotators and has less impact on plant rotation.

[0220] The microgravity simulation method for plants based on buoyancy disturbance biaxial rotation and center of gravity following in this application yields a fitted gravity (overall result: 0.0000396 < g < 0.000156) of g < 0.00016 at a frequency of 5-10 s, which is much smaller than 10. -3 It has a better microgravity simulation effect, and buoyancy provides a buoyancy environment for all mechanical structures. The disturbance of gravity by liquid fluctuations truly changes the gravity experienced by plants in the vertical direction. The experimental results are more meaningful than those of traditional rotary devices, and the frequency of rotational acceleration and rotational direction changes is further reduced, thus further reducing the impact of rotation on plants.

[0221] This application employs a random buoyancy perturbation dual-axis rotational microgravity control algorithm for microgravity regulation. The dual-factor coupling of random buoyancy and rotational speed achieves real-time gravity changes. Minimizing the fitted function using a genetic algorithm further improves the simulation accuracy of microgravity. A plant growth center-of-gravity following algorithm controls the center-of-gravity displacement, ensuring the plant's center of gravity remains at the rotation axis position. This avoids uneven shear force on the rotational surface caused by the rotation axis, thus reducing the adverse physiological effects of rotation on the plant. The simultaneous application of these two algorithms enhances the microgravity simulation effect and extends the cultivation time. Specifically, when buoyancy perturbation is involved, the fitted gravitational acceleration is at its minimum value, while the rotational speed of the gyrator is reduced. By utilizing the gravitational acceleration caused by the falling tower disturbance generated by random buoyancy, the gravity of the cultivated plants and the rotating system is counteracted. The thermal insulation and random buoyancy of the underwater operation reduce the impact of air convection and air shear forces on the plants during cultivation, further simulating the microgravity environment of a confined space and providing simulation conditions for low-gravity simulations on the Moon / Mars. This approach addresses the problem of uneven centripetal force caused by the increased center of gravity of plants in existing three-dimensional rotating microgravity simulation devices, thereby reducing systematic errors caused by plant growth and enabling better simulation of microgravity plant cultivation.

[0222] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0223] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A method for simulating microgravity in plants based on buoyancy disturbance biaxial rotation and center of gravity following, characterized in that, Includes 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; 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; Step 3: Use the device control system to simulate microgravity in plants; The device control system includes: a microgravity regulation system, a center of gravity displacement control system, and an environmental control system; The microgravity control system is configured to use the random buoyancy disturbance dual-axis rotation microgravity control algorithm for microgravity control. The center of gravity displacement control system is configured to use the plant growth center of gravity following algorithm for center of gravity displacement control. The environmental control system is configured to regulate plant cultivation environment parameters; The random buoyancy disturbance dual-axis rotation microgravity control algorithm includes: establishing a random buoyancy dual-axis rotation model coupled with random buoyancy and random rotation speed; fitting the net force variation curve with time or position using the random buoyancy dual-axis rotation model; dynamically adjusting the buoyancy fluctuation, rotation speed, and direction variation frequency with a set time according to the variation curve; running a genetic algorithm to optimize the dynamic adjustment process to minimize the objective function, obtain the optimal control path for buoyancy fluctuation, rotation speed, and direction, and performing microgravity control based on the optimal control path; The process of fitting the net force variation curve with time or position using the random buoyancy biaxial rotation model includes: generating samples of Z-axis position changes caused by buoyancy fluctuations based on an assumed random distribution; for each sample, calculating the vector sum of the buoyancy disturbance acceleration force, the centripetal force in two directions, and the gravitational acceleration to obtain the net force corresponding to each sample; generating a dynamic fitting function based on the acceleration changing with time; fitting the net force variation curve with time or position using a curve fitting method based on the net force corresponding to each sample, and minimizing gravity adjustment based on the dynamic fitting function; The plant growth center of gravity following algorithm includes: establishing a plant growth model; using the L-system plant growth algorithm to calculate the plant center of gravity of the plant growth model, and plotting the displacement change curve of the plant center of gravity as the plant grows; controlling the displacement of the cultivation platform according to the displacement change curve so that the plant center of gravity is always at the position of the rotation axis.

2. The plant microgravity simulation method based on buoyancy disturbance biaxial rotation and center of gravity following according to claim 1, 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, calculate the centripetal force in the x-axis and y-axis directions as a function of time frequency; Considering the change in centripetal force, we introduce random fluctuations in buoyancy and calculate the vector sum of the buoyancy disturbance acceleration, the centripetal force in two directions, and the gravitational acceleration to obtain the net force corresponding to each sample.

3. The plant microgravity simulation method based on buoyancy disturbance biaxial rotation and center of gravity following according to claim 1, characterized in that, The step of calculating the plant centroid of the plant growth model using the L-system plant growth algorithm and plotting the displacement curve of the plant centroid as the plant grows includes: The plant morphology of the plant growth model was generated using the L-system plant growth algorithm. Calculate the plant centroid of the plant growth model based on the plant morphology, and plot the displacement curve of the plant centroid as the plant grows.

4. The plant microgravity simulation method based on buoyancy disturbance biaxial rotation and center of gravity following according to claim 3, characterized in that, The calculation of the plant centroid of the plant growth model based on the plant morphology includes: The stem weight, stem centroid, leaf weight, and leaf centroid of the plant are obtained based on the plant morphology. The plant center of gravity of the plant growth model is calculated based on the stem weight, the stem centroid, the leaf weight, and the leaf centroid, and a curve showing the displacement change of the plant center of gravity as the plant grows is plotted.

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