Propeller rotating speed control method for determining self-propulsion point of self-propulsion model of underwater vehicle
By adjusting the propeller speed controller and speed correction coefficient in real time, the problems of low acceleration efficiency and speed loss of underwater vehicles in traditional methods are solved, and the target speed is achieved quickly and stably.
Patent Information
- Application Number
- CN202511003377.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-21
- Publication Date
- 2025-10-28
AI Technical Summary
Traditional methods for determining the self-centering point of underwater vehicles and models suffer from problems such as increased resistance, time and effort consumption, inability to adapt to different navigation depths and environmental disturbances, resulting in speed loss and low acceleration efficiency.
The propeller speed control method is adopted. By monitoring the speed and acceleration in real time, the propeller speed is dynamically adjusted by the propeller speed controller, including a nonlinear PI controller and a speed correction coefficient, to achieve rapid acceleration to the target speed.
It improves the convergence speed of thrust-drag balance, is applicable to various operating conditions, simplifies the testing and simulation process, avoids speed loss, and ensures safe and stable navigation.
Smart Images
Figure CN120848610A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of underwater vehicle speed technology, and in particular to a propeller speed control method for determining the self-propulsion point of an underwater vehicle model. Background Technology
[0002] Before conducting model tests and simulations of underwater vehicles, it is first necessary to determine the self-centering point of the self-propelled model, that is, to determine the propeller speed corresponding to the stable navigation of the underwater vehicle at the target speed. The speed of an underwater vehicle mainly depends on establishing the thrust-drag balance of the underwater vehicle's self-propelled model at the target speed. Therefore, determining the self-centering point of the underwater vehicle determines its speed.
[0003] The determination of the self-propulsion point of traditional underwater vehicle self-propelled models is mostly based on the forced self-propulsion method of towed pool restraint model. By determining the propeller speed corresponding to the underwater vehicle self-propelled model in the constant speed, constant depth and directional straight-line state within the design speed range, the set propeller speed is kept constant during underwater vehicle self-propelled model model test or numerical simulation, so that the underwater vehicle self-propelled model can accelerate to the target speed.
[0004] However, this method has certain drawbacks: First, when the underwater self-propelled model is sailing straight underwater, there may be some small range of attitude angle and rudder angle adjustments, which cannot maintain the ideal straight-sailing state during the forced self-propulsion test of the towed pool restrained model. This will undoubtedly lead to increased drag, and the propeller thrust at the set propeller speed cannot completely balance the drag, resulting in a loss of speed. Second, when the underwater self-propelled model is sailing straight near the water surface, near the seabed, or near the ice surface, the drag and propeller propulsion efficiency corresponding to different sailing depths are not the same. Using the forced self-propulsion method to conduct underwater self-propelled model tests to determine the self-way point is time-consuming and laborious. Meanwhile, hydrodynamic disturbances during the direct-straight-way movement of underwater vehicles on the surface, seabed, or ice will inevitably lead to changes in hull attitude and rudder angle. Near-surface navigation may also induce wave-making, generating additional wave drag. These factors will undoubtedly cause the actual speed of the underwater vehicle's self-propelled model to differ significantly from the target speed. Thirdly, when the propeller speed is constant, the underwater vehicle's self-propelled model initially accelerates at almost constant acceleration, gradually decreasing as it approaches the target speed; this process is relatively long. However, the steering points in underwater vehicle self-propelled model maneuvering tests or numerical simulations require the underwater vehicle to reach a stable straight-way state before execution. The method of accelerating the underwater vehicle's self-propelled model's straight-way movement based on a constant propeller speed is not only inefficient but also requires a large test area or numerical simulation domain to meet the spatial requirements of the long-duration acceleration straight-way movement. Summary of the Invention
[0005] This application addresses the aforementioned problems and technical requirements by proposing a propeller speed control method for determining the self-centering point of an underwater vehicle model. The technical solution of this application is as follows:
[0006] A method for controlling the propeller speed to determine the self-centering point of an underwater vehicle model includes the following steps:
[0007] Determine the target speed U of the underwater vehicle model. target Determine the initial sampling time t0 = 0, the speed U0 = 0, and the propeller speed n0;
[0008] For any sampling time t i =i·Δt, based on the underwater vehicle's self-propelled model at the previous sampling time t i-1 speed U i-1 Current sampling time t i speed U i and target speed U target Determine the current sampling time t i Speed correction factor α i Δt is the sampling time interval, and the initial value of the integer parameter i is 1;
[0009] Based on the previous sampling time t i-1 speed U i-1 and propeller speed n i-1 and the current sampling time t i speed U i Speed correction factor α i and target speed U target The current sampling time t is generated using the propeller speed controller. i propeller speed n i ;
[0010] Using the current sampling time t i propeller speed n i The propeller is driven to rotate, causing the underwater vehicle to accelerate and travel straight. The underwater vehicle's self-propelled model is then obtained at the next sampling time t. i+1 The speed U = (i+1)·Δt i+1 ;
[0011] Let i = i + 1, and repeat the steps of generating the propeller speed at the current sampling time and obtaining the speed at the next sampling time until the speed converges to the predetermined range of the target speed. Then, take the propeller speed at the current sampling time as the propeller speed at the self-navigation point of the underwater vehicle model.
[0012] A further technical solution involves introducing a nonlinear term into the PI controller using a nonlinear constant γ to construct a propeller speed controller; and using the propeller speed controller to generate the current sampling time t.i propeller speed n i for:
[0013]
[0014] Where P is a proportionality constant, I is an integral constant, and γ is a nonlinear constant used to control the speed convergence rate of the underwater vehicle's self-propelled model, γ>1.
[0015] Its further technical solution is to use the propeller speed n0 at the initial sampling time t0 = 0 and the target speed U target Determine the proportionality constant P = n0 / U target Determine the integration constant I = k·P, where k is a predetermined multiple.
[0016] A further technical solution involves determining the propeller rotational speed n0 at the initial sampling time t0 = 0, including:
[0017] Based on the propeller design requirements of the underwater vehicle self-propelled model, the target speed U is determined. target The maximum rotational speed n of the propeller below max ;
[0018] Based on the maximum propeller speed n max Determine the propeller speed n0 = α0·n at the initial sampling time t0 = 0. max α0 is a predetermined initial speed correction factor and α0∈[0.9,1].
[0019] The further technical solution is to determine the current sampling time t. i Speed correction factor α i include:
[0020] Based on the underwater vehicle's self-propelled model at the previous sampling time t i-1 speed U i-1 and the current sampling time t i speed U i And target speed U target Determine the underwater vehicle's self-propelled model at the current sampling time t. i Speed deviation and navigation acceleration
[0021] Based on the current sampling time t i Speed deviation ε i and navigation acceleration a i Determine the current sampling time t i The base value of the speed correction factor
[0022] For the current sampling time t iThe acceleration of the ship a i Differentiating the derivative yields the rate of change of acceleration δ i According to the current sampling time t i The rate of change of acceleration δ i Determine the current sampling time t i Speed correction factor compensation value
[0023] Determine the current sampling time t i Speed correction factor min() means taking the minimum value.
[0024] The further technical solution is to determine the current sampling time t. i The base value of the speed correction factor include:
[0025] Based on the current sampling time t i Speed deviation ε i and navigation acceleration a i Determine the speed stage of the underwater vehicle from the model aircraft;
[0026] Based on the control requirements at different speed stages and in conjunction with the initial speed correction coefficient α0, the base value of the speed correction coefficient is determined. The speed phase includes the large speed deviation phase, the stable acceleration phase, the abnormal deceleration phase, and the speed convergence phase.
[0027] The further technical solution is to determine the current sampling time t. i The base value of the speed correction factor include:
[0028] When the speed deviation ε i Exceeding the first deviation threshold ε th1 At that time, it was determined that the underwater vehicle was in a stage of large speed deviation, and the base value of the speed correction coefficient was determined.
[0029] When the speed deviation ε i Not exceeding the first deviation threshold ε th1 And exceeds the second deviation threshold ε th2 And the acceleration a i When the value is greater than 0, it is determined that the underwater vehicle is in a stable acceleration phase, and the base value of the speed correction coefficient is determined. a max This is the theoretical value of the maximum acceleration;
[0030] When the speed deviation ε i Not exceeding the first deviation threshold ε th1 And exceeds the second deviation threshold ε th2And the acceleration a i When the value is ≤0, it is determined that the underwater vehicle is in an abnormal deceleration phase, and the base value of the speed correction coefficient is determined.
[0031] When the speed deviation ε i Not exceeding the second deviation threshold ε th2 At that time, it is determined that the underwater vehicle is in the speed convergence phase, and the base value of the speed correction coefficient is determined. Where, 0 < ε th2 <ε th1 <1.
[0032] The further technical solution is to determine the current sampling time t. i Speed correction factor compensation value include:
[0033] Based on the current sampling time t i The rate of change of acceleration δ i The abrupt changes in drag experienced by the underwater vehicle model are determined, and the speed correction coefficient compensation value is determined based on these changes in drag.
[0034] A further technical solution involves determining the speed correction coefficient compensation value based on the sudden change in drag. include:
[0035] When the rate of change of acceleration δ i The absolute value is greater than the rate of change threshold δ th And the rate of change of acceleration δ i When the speed is less than 0, determine the sudden increase in drag experienced by the underwater vehicle model and determine the compensation value of the speed correction coefficient. Otherwise, determine the compensation value for the speed correction factor. λ is the compensation coefficient, sign() represents the sign function, and log() represents the logarithmic function.
[0036] The further technical solution involves determining the sampling time interval Δt, including:
[0037] For the self-propelled model test of underwater vehicles, the sampling time interval Δt = L / (M·U) target L is the length of the underwater vehicle's self-propelled model, and M is a constant coefficient;
[0038] For numerical simulation of underwater vehicle self-propelled models, the sampling time interval Δt is a predetermined multiple of the calculation time step.
[0039] The beneficial technical effects of this application are:
[0040] This application discloses a propeller speed control method for determining the self-centering point of an underwater self-propelled model. This method is applicable to the initial straight-line start-up phase of any underwater self-propelled model under any operating conditions (including underwater, near-surface, near-seabed, near-ice, etc.). This method does not require knowing the exact values of drag and propeller thrust experienced by the underwater self-propelled model. By monitoring the speed of the underwater self-propelled model in real time at various sampling moments, a suitable propeller speed control strategy can be obtained using a propeller speed controller, thereby rapidly accelerating the underwater self-propelled model to the target speed. Compared to the traditional method of determining the self-centering point based on forced self-propulsion using a towed pool-constrained model, this method effectively improves the thrust-drag balance convergence speed. Furthermore, this method can be applied simultaneously to physical model tests and numerical simulations of underwater self-propelled models, and is simple to operate and has a wide range of applications.
[0041] By analyzing the speed deviation from the target speed at various times and the acceleration at each time point, the speed stage of the underwater vehicle's autopropulsion model is determined. The speed correction coefficient is then adjusted according to different speed stages to achieve targeted adjustments to the control strategy. This facilitates precise control of the propeller speed, ensuring the safe and stable navigation of the underwater vehicle's autopropulsion model. Furthermore, the continuously updated and adjusted propeller speed control strategy ensures that the speed converges to the target speed, effectively avoiding the speed loss problem caused by the fixed propeller speed in traditional towed pool-constrained model forced autopropulsion methods. Attached Figure Description
[0042] Figure 1 This is a flowchart of the propeller speed control method.
[0043] Figure 2 This is a schematic diagram of the geometric model of an underwater vehicle self-propelled model, one embodiment.
[0044] Figure 3 This is a comparison chart of the thrust-balance convergence acceleration effect of an underwater vehicle in one embodiment. Detailed Implementation
[0045] The specific embodiments of this application will be further described below with reference to the accompanying drawings.
[0046] This application discloses a propeller speed control method for determining the autopilot point of an underwater vehicle. Please refer to [reference needed]. Figure 1 The flowchart shown illustrates the specific steps of this method as follows:
[0047] Step 1: Determine the target speed U of the underwater vehicle model. target Determine the initial sampling time t0 = 0, the speed U0 = 0, and the propeller speed n0.
[0048] The design parameters for different types and specifications of underwater self-propelled models vary. Therefore, the target speed and maximum propeller speed at the thrust-resistance balance self-propulsion point of an underwater self-propelled model need to be determined based on the design parameters. Taking the Joubert BB2 standard underwater self-propelled model as an example, the specific geometry of this model is as follows: Figure 2 As shown. Based on this model, this application sets the target speed U. target =1.2m / s.
[0049] In one embodiment, determining the propeller speed n0 at the initial sampling time t0 = 0 includes: determining the propeller speed n0 at the target speed U based on the propeller design requirements of the underwater vehicle self-propelled model. target The maximum rotational speed that ensures the propeller's safety and normal operation is the propeller's maximum rotational speed n. max Based on the maximum propeller speed n max Determine the propeller speed n0 = α0·n at the initial sampling time t0 = 0. max α0 is a predetermined initial speed correction coefficient. Since the initial speed is low during the initial straight-line start-up phase, rapid acceleration is required. Therefore, the propeller speed at the initial sampling time must be set sufficiently high to provide greater thrust. Based on historical test results, this application determines α0 ∈ [0.9, 1]. Selecting the initial speed correction coefficient within this range yields better acceleration. The specific value can be customized according to the underwater vehicle self-propelled model used. In this application, α0 = 0.917. Based on the design requirements of the Joubert BB2 underwater vehicle standard self-propelled model, the maximum propeller speed n can be determined. max =84 rad / s, thus the propeller speed at the initial sampling time t0=0 can be determined to be n0=77.03 rad / s. Based on this initial propeller speed, the underwater vehicle self-propelled model starts its straight-line motion, and the propeller speed is controlled in a closed-loop iterative manner using a propeller speed controller.
[0050] Step 2, for any sampling time t i =i·Δt, based on the underwater vehicle's self-propelled model at the previous sampling time t i-1 speed U i-1 Current sampling time t i speed U i and target speed U target Determine the current sampling time t i Speed correction factor α i Δt is the sampling time interval, and the initial value of the integer parameter i is 1.
[0051] Real-time monitoring of ship speed at each sampling time, sampling time t i =i·Δt to t i+1= (i+1)·Δt represents one iteration. During each iteration, the propeller speed is kept constant to propel the underwater vehicle self-propelled model to accelerate straight ahead. The duration of each iteration is the sampling time interval Δt between two adjacent sampling moments. The length of the sampling time interval determines the frequency at which the controller adjusts the propeller speed, thus determining the control accuracy and efficiency. This application determines the sampling time interval Δt based on the application scenario. In one embodiment, for underwater vehicle self-propelled model tests, the sampling time interval Δt is set according to the specifications of the underwater vehicle self-propelled model, and Δt = L / (M·U) target L represents the length of the underwater vehicle's self-propelled model, and M is a constant coefficient. A larger value for M results in a smaller sampling time interval, higher control frequency, and higher accuracy, but lower efficiency. The specific value of M can be customized according to the actual application. This application addresses... Figure 2 The Joubert BB2 underwater vehicle standard self-propelled model shown is used. Taking into account both accuracy and efficiency, M=200 is set, thus the sampling time interval Δt≈0.02s is obtained for the underwater vehicle self-propelled model test.
[0052] For numerical simulation of underwater vehicles using self-propelled models, the sampling time interval Δt is a predetermined multiple of the calculation time step. Similarly, the sampling time interval also determines the computational efficiency and accuracy of the numerical simulation, and can be customized based on the computation time step according to actual needs. For example, if the computation time step is 0.01s, and there are sufficient hardware resources for the numerical simulation, a sampling time interval Δt = 0.01s can be selected to ensure computational accuracy, meaning the propeller speed is adjusted at each simulation node.
[0053] Because the speed of the underwater vehicle model changes continuously at each sampling time, and the speed change varies at different speed stages, the propeller speed needs to be adjusted accordingly at each sampling time. In one embodiment, the current sampling time t is determined. i Speed correction factor α i include:
[0054] (1) Based on the underwater vehicle self-propelled model at the previous sampling time t i-1 speed U i-1 and the current sampling time t i speed U i And target speed U target Determine the underwater vehicle's self-propelled model at the current sampling time t. i Speed deviation and navigation acceleration
[0055] (2) Based on the current sampling time t i Speed deviation εi and navigation acceleration a i Determine the current sampling time t i The base value of the speed correction factor
[0056] In one embodiment, the current sampling time t is determined. i The base value of the speed correction factor include:
[0057] Based on the current sampling time t i Speed deviation ε i and navigation acceleration a i The speed phase of the underwater vehicle model is determined. This phase includes a large speed deviation phase, a stable acceleration phase, an abnormal deceleration phase, and a speed convergence phase. From the initial sampling time t0 = 0, the underwater vehicle model's speed is low, deviating significantly from the target speed. At this point, it is necessary to steadily increase the propeller speed to provide greater thrust to overcome static friction drag. As the speed gradually increases and remains in a stable acceleration phase, the increase in propeller speed needs to be reduced to match the drag change while preventing excessive thrust. When the speed is sufficiently close to the target speed, the control objective for propeller speed is to suppress oscillations and achieve smooth convergence.
[0058] Based on the control requirements for different speed stages mentioned above, and in conjunction with the initial speed correction coefficient α0, the base value of the speed correction coefficient is determined.
[0059] In one embodiment, the current sampling time t is determined. i The base value of the speed correction factor include:
[0060] When the speed deviation ε i Exceeding the first deviation threshold ε th1 At this point, the underwater vehicle model is determined to be in a stage of large speed deviation. A larger propeller thrust is required at this time, but the upper limit of propeller thrust is limited by cavitation and motor power. The speed correction coefficient increment design typically needs to retain a 15% safety margin in engineering safety design. This application, through extensive experimental results and theoretical analysis, finds that 0.07(1-α0) can meet this safety margin. Based on this control requirement, the basic value of the speed correction coefficient is determined.
[0061] When the speed deviation ε i Not exceeding the first deviation threshold ε th1 And exceeds the second deviation threshold ε th2 And the acceleration a iWhen α0 > 0, the underwater vehicle is determined to be in a stable acceleration phase. At this point, it is necessary to further control the increase in the speed correction coefficient, dynamically fine-tuning it based on real-time acceleration to achieve a smooth transition. As acceleration increases, the increase in the speed correction coefficient decreases, and the larger α0 is, the smaller the adjustment range to prevent overshoot. Based on this control requirement, a base value for the speed correction coefficient is determined. a max This is the theoretical value of the maximum acceleration, which can be calculated based on experiments or Newtonian dynamics models. T max R is the maximum propeller thrust. min is the hydrostatic resistance, and m is the mass of the underwater vehicle model.
[0062] When the speed deviation ε i Not exceeding the first deviation threshold ε th1 And exceeds the second deviation threshold ε th2 And the acceleration a i When the speed deviation is ≤0, the underwater vehicle is determined to be in an abnormal deceleration phase. At this point, the speed deviation is significant, but the deceleration indicates an abnormal situation, such as a sudden increase in drag due to external environmental interference or a malfunction in the propulsion system. To ensure sufficient propeller thrust to cope with this abnormal situation, it is not necessary to further reduce the increase in the speed correction coefficient. Based on this control requirement, the base value of the speed correction coefficient is determined.
[0063] When the speed deviation ε i Not exceeding the second deviation threshold ε th2 At this point, it is determined that the underwater vehicle is in the speed convergence phase, where the speed is close to the target speed. To ensure smooth convergence, a base value for the speed correction coefficient is determined based on this control requirement. Exponential decay is used to ensure smoothness and prevent overshoot; where 0 < ε th2 <ε th1 <1, ε th1 ε th2 The value can be customized, for example, setting ε. th1 =0.3, ε th2 =0.1.
[0064] (3) For the current sampling time t i The acceleration of the ship a i Differentiating the derivative yields the rate of change of acceleration δ i According to the current sampling time t i The rate of change of acceleration δ i Determine the current sampling time t i Speed correction factor compensation value
[0065] The real marine environment is complex and variable, and sudden changes in drag may occur, such as a sudden increase in drag when entering a turbulent region. Therefore, when conducting self-propelled model tests or numerical simulations of underwater vehicles, it is necessary to consider the situation of sudden drag changes, and to make certain compensations when drag increases suddenly in order to ensure that sufficient propeller thrust can be provided.
[0066] In one embodiment, the current sampling time t is determined. i Speed correction factor compensation value include:
[0067] Based on the current sampling time t i The rate of change of acceleration δ i The abrupt changes in drag experienced by the underwater vehicle model are determined, and the speed correction coefficient compensation value is determined based on these changes in drag.
[0068] The rate of change of acceleration reflects the acceleration state of an underwater vehicle's autopilot. During normal, stable acceleration, the rate of change of acceleration remains within a stable range. By monitoring the rate of change of acceleration, we can determine the abrupt changes in drag experienced by the underwater vehicle's autopilot, and thus determine the amount of compensation needed for the speed correction coefficient. The speed correction coefficient compensation value is determined based on the abrupt changes in drag. The specific method is as follows: when the rate of change of acceleration δ i The absolute value is greater than the rate of change threshold δ th And the rate of change of acceleration δ i When the speed is less than 0, determine the sudden increase in drag experienced by the underwater vehicle model and determine the compensation value of the speed correction coefficient. Otherwise, determine the compensation value for the speed correction factor. λ is the compensation coefficient, sign() represents the sign function, and log() represents the logarithmic function. The sign function term determines the sign of the speed correction coefficient compensation value based on the sign of the speed acceleration. When the speed acceleration is positive, it indicates that the engine is still accelerating under a sudden increase in drag. In this case, the propeller thrust is sufficient, and the speed correction coefficient can be appropriately reduced. Conversely, if the speed acceleration is negative, the speed correction coefficient needs to be increased. The rate of change threshold δ... th Furthermore, the compensation coefficient λ can be customized according to the actual application, such as setting δ. th =30, λ=0.03.
[0069] (4) Due to the speed correction factor α i The upper limit is 1, therefore, the current sampling time t is determined. i Speed correction factor min() means taking the minimum value.
[0070] Step 3, based on the previous sampling time t i-1 speed Ui-1 and propeller speed n i-1 and the current sampling time t i speed U i Speed correction factor α i and target speed U target The current sampling time t is generated using the propeller speed controller. i propeller speed n i .
[0071] A propeller speed controller is used to regulate the propeller speed in real time to cope with various situations under different operating conditions, and can be designed according to actual application requirements. In one embodiment, a nonlinear term is introduced into a PI controller using a nonlinear constant γ to construct the propeller speed controller; to calculate the propeller speed at each discrete sampling time, a differential propeller speed controller is used to generate the current sampling time t. i propeller speed n i for:
[0072]
[0073] Where P is a proportionality constant, I is an integral constant, and γ is a nonlinear constant used to control the speed convergence rate of the underwater vehicle's autopilot, γ > 1. This nonlinear scheme is chosen to maximize the speed convergence rate of the underwater vehicle's autopilot. If γ is too small, the improvement in speed convergence rate will be insignificant; if γ is too large, the speed convergence rate will be too fast, resulting in a large deviation between the final stable speed and the target speed. Therefore, γ is generally taken between 2 and 4, and in this application, γ is taken as 3.
[0074] The values of the proportional constant P and the integral constant I also determine the control performance of the propeller speed, thus affecting the speed convergence process. For example, an excessively large value of I can cause speed fluctuations, while an excessively small value can result in a slow speed convergence. In one embodiment, based on the propeller speed n0 at the initial sampling time t0 = 0 and the target speed U... target Determine the proportionality constant P = n0 / U target The integration constant I = k·P is determined, where k is a predetermined multiple; the value of k can be customized according to actual needs, and in this application, k = 0.064 is set.
[0075] Step 4, using the current sampling time t i propeller speed n i The propeller is driven to rotate, causing the underwater vehicle to accelerate and travel straight. The underwater vehicle's self-propelled model is then obtained at the next sampling time t. i+1 The speed U = (i+1)·Δt i+1 .
[0076] Let i = i + 1, and repeat the steps of generating the propeller speed at the current sampling time and obtaining the speed at the next sampling time until the speed converges to the predetermined range of the target speed. Then, take the propeller speed at the current sampling time as the propeller speed at the self-navigation point of the underwater vehicle model.
[0077] In each iteration, the propeller speed at the start of the iteration is used as a constant propeller speed to control the underwater vehicle's self-propelled acceleration in a straight line. The speed at the end of the iteration is measured and fed back to the propeller speed controller. This closed-loop iterative control process is repeated until the speed approaches the target speed and becomes stable, at which point the speed is determined to have converged to a predetermined range within the target speed. The criterion for determining whether the speed approaches the target speed and becomes stable can be set as follows: the deviation between the speed and the target speed in a predetermined number of consecutive iterations of the control process is within a predetermined error range. At this point, the underwater vehicle's self-propelled model reaches the thrust-resistance balance self-propulsion point. The propeller speed is set to be constant at the current sampling time, and the predetermined self-propelled model maneuvering motion test or numerical simulation command can be executed.
[0078] The propeller speed control method of this application is used for Figure 2 The effectiveness of this method is verified by numerical simulation of the underwater straight-line acceleration process of the Joubert BB2 underwater vehicle standard self-propelled model. The initial sampling time t0 = 0 has a speed U0 = 0, and the propeller speed is kept constant at n0 = 77.03 rad / s during the time interval from t0 = 0 to t1 = Δt. The underwater vehicle self-propelled model accelerates straight-line at a constant propeller speed to the sampling time t1 = Δt, and the speed at this moment is fed back and recorded as U1 = 0.0038 m / s.
[0079] For the first iteration when i=1, the propeller speed controller generates the propeller speed n1 = 76.76 rad / s at the current sampling time t1 = Δt. The propeller speed is kept constant at n1 = 76.76 rad / s from t1 = Δt to t2 = 2Δt, allowing the underwater vehicle to accelerate straight to the sampling time t2 = 2Δt at this constant propeller speed. The speed at this moment, U2 = 0.0099 m / s, is fed back and recorded. Then, i = i+1 is set, and the next iteration begins, continuing the propeller speed control process until the speed converges to the target speed. Figure 3 As shown, it takes approximately 20 seconds for the final speed to approach the target speed and stabilize. In contrast, the traditional method based on a towed pool-constrained model for forced self-propulsion requires approximately 95 seconds for the underwater vehicle's self-propulsion model to approach the target speed and stabilize, which is about 3.4 times longer than the method described in this application. Furthermore, the stable speed ultimately achieved by the method in this application is 1.001U. targetThe error from the target speed is 0.1%, while the traditional forced self-propulsion method based on towed pool restraint model suffers from speed losses due to changes in the underwater vehicle's self-propulsion model attitude, rudder angle, and hydrodynamic interference, resulting in a final speed of 0.974U. target The error between the actual speed and the target speed is 2.6%, which is much higher than the error in this application.
[0080] The above descriptions are merely preferred embodiments of this application, and this application is not limited to the above embodiments. It is understood that other improvements and variations that can be directly derived or conceived by those skilled in the art without departing from the spirit and concept of this application should be considered to be included within the protection scope of this application.
Claims
1. A method for controlling the propeller speed to determine the self-centering point of an underwater vehicle, characterized in that, The propeller speed control method includes: Determine the target speed U of the underwater vehicle model. target Determine the initial sampling time t0 = 0, the speed U0 = 0, and the propeller speed n0; For any sampling time t i =i·Δt, based on the underwater vehicle's self-propelled model at the previous sampling time t i-1 speed U i-1 Current sampling time t i speed U i and target speed U target Determine the current sampling time t i Speed correction factor α i Δt is the sampling time interval, and the initial value of the integer parameter i is 1; Based on the previous sampling time t i-1 speed U i-1 and propeller speed n i-1 and the current sampling time t i speed U i Speed correction factor α i and target speed U target The current sampling time t is generated using the propeller speed controller. i propeller speed n i ; Using the current sampling time t i propeller speed n i The propeller is driven to rotate, causing the underwater vehicle to accelerate and travel straight. The underwater vehicle's self-propelled model is then obtained at the next sampling time t. i+1 The speed U = (i+1)·Δt i+1 ; Let i = i + 1, and repeat the steps of generating the propeller speed at the current sampling time and obtaining the speed at the next sampling time until the speed converges to the predetermined range of the target speed. Then, take the propeller speed at the current sampling time as the propeller speed at the self-navigation point of the underwater vehicle model.
2. The propeller speed control method according to claim 1, characterized in that, The propeller speed controller is constructed by introducing a nonlinear term into the PI controller using a nonlinear constant γ; the propeller speed controller is then used to generate the current sampling time t. i propeller speed n i for: Where P is a proportionality constant, I is an integral constant, and γ is a nonlinear constant used to control the speed convergence rate of the underwater vehicle's self-propelled model, γ>1.
3. The propeller speed control method according to claim 2, characterized in that, Based on the propeller speed n0 at the initial sampling time t0 = 0 and the target speed U target Determine the proportionality constant P = n0 / U target Determine the integration constant I = k·P, where k is a predetermined multiple.
4. The propeller speed control method according to claim 1, characterized in that, Determining the propeller speed n0 at the initial sampling time t0 = 0 includes: Based on the propeller design requirements of the underwater vehicle self-propelled model, the target speed U is determined. target The maximum rotational speed n of the propeller below max ; Based on the maximum propeller speed n max Determine the propeller speed n0 = α0·n at the initial sampling time t0 = 0. max α0 is a predetermined initial speed correction factor and α0∈[0.9,1].
5. The propeller speed control method according to claim 4, characterized in that, The determination of the current sampling time t i Speed correction factor α i include: Based on the underwater vehicle's self-propelled model at the previous sampling time t i-1 speed U i-1 and the current sampling time t i speed U i And target speed U target Determine the underwater vehicle's self-propelled model at the current sampling time t. i Speed deviation and navigation acceleration Based on the current sampling time t i Speed deviation ε i and navigation acceleration a i Determine the current sampling time t i The base value of the speed correction factor For the current sampling time t i The acceleration of the ship a i Differentiating the derivative yields the rate of change of acceleration δ i According to the current sampling time t i The rate of change of acceleration δ i Determine the current sampling time t i Speed correction factor compensation value Determine the current sampling time t i Speed correction factor min() means taking the minimum value.
6. The propeller speed control method according to claim 5, characterized in that, The determination of the current sampling time t i The base value of the speed correction factor include: Based on the current sampling time t i Speed deviation ε i and navigation acceleration a i Determine the speed stage of the underwater vehicle from the model aircraft; Based on the control requirements at different speed stages and in conjunction with the initial speed correction coefficient α0, the base value of the speed correction coefficient is determined. The speed phase includes a large speed deviation phase, a stable acceleration phase, an abnormal deceleration phase, and a speed convergence phase.
7. The propeller speed control method according to claim 6, characterized in that, The determination of the current sampling time t i The base value of the speed correction factor include: When the speed deviation ε i Exceeding the first deviation threshold ε th1 At that time, it was determined that the underwater vehicle was in a stage of large speed deviation, and the base value of the speed correction coefficient was determined. When the speed deviation ε i Not exceeding the first deviation threshold ε th1 And exceeds the second deviation threshold ε th2 And the acceleration a i When the value is greater than 0, it is determined that the underwater vehicle is in a stable acceleration phase, and the base value of the speed correction coefficient is determined. a max This is the theoretical value of the maximum acceleration; When the speed deviation ε i Not exceeding the first deviation threshold ε th1 And exceeds the second deviation threshold ε th2 And the acceleration a i When the value is ≤0, it is determined that the underwater vehicle is in an abnormal deceleration phase, and the base value of the speed correction coefficient is determined. When the speed deviation ε i Not exceeding the second deviation threshold ε th2 At that time, it is determined that the underwater vehicle is in the speed convergence phase, and the base value of the speed correction coefficient is determined. Where, 0 < ε th2 <ε th1 <1.
8. The propeller speed control method according to claim 5, characterized in that, The determination of the current sampling time t i Speed correction factor compensation value include: Based on the current sampling time t i The rate of change of acceleration δ i The abrupt changes in drag experienced by the underwater vehicle model are determined, and the speed correction coefficient compensation value is determined based on these changes in drag.
9. The propeller speed control method according to claim 8, characterized in that, Determine the speed correction factor compensation value based on the sudden change in drag. include: When the rate of change of acceleration δ i The absolute value is greater than the rate of change threshold δ th And the rate of change of acceleration δ i When the speed is less than 0, determine the sudden increase in drag experienced by the underwater vehicle model and determine the compensation value of the speed correction coefficient. Otherwise, determine the compensation value for the speed correction factor. λ is the compensation coefficient, sign() represents the sign function, and log() represents the logarithmic function.
10. The propeller speed control method according to claim 1, characterized in that, Determining the sampling time interval Δt includes: For the self-propelled model test of underwater vehicles, the sampling time interval Δt = L / (MU) target L is the length of the underwater vehicle's self-propelled model, and M is a constant coefficient; For numerical simulation of underwater vehicle self-propelled models, the sampling time interval Δt is a predetermined multiple of the calculation time step.