Method for determining deflection rate requirement of steering engine
By determining the required servo deflection rate and utilizing flight state and system theory, the problem of PIO caused by inappropriate servo deflection rate selection was solved, achieving a balance between safety and economy in the design phase and avoiding the occurrence of PIO.
Patent Information
- Application Number
- CN202511859360.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-10
- Publication Date
- 2026-02-27
AI Technical Summary
In the existing technology, inappropriate selection of servo deflection rate is the main cause of PIO phenomenon, which leads to flight safety issues, and it is difficult to effectively avoid PIO trend during the design stage.
By obtaining the transfer function of the stabilized aircraft under typical flight conditions, and combining the Neal-Smith criterion and nonlinear system theory, the negative inverse description function of the servo is determined using the Nichols diagram and Gap criterion. The servo deflection rate requirement is calculated to ensure that the pilot-stabilized aircraft transfer function is tangent to the negative inverse description function of the servo, and the minimum requirement expression for the servo deflection rate is constructed.
By rationally selecting the servo deflection rate during the aircraft design phase, the PIO trend can be effectively avoided, unnecessary design costs can be reduced, and flight safety can be improved.
Smart Images
Figure CN121580673A_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of flight mechanics technology, and specifically relates to a method for determining the deflection rate requirement of a servo motor. Background Technology
[0002] With the development of modern high-gain, full-authority, fly-by-wire aircraft, while improving flight characteristics, safety, and comfort, more complex human-machine coupling situations also arise. Pilot-induced oscillation (PIO) caused by the rate-limited servo (RLA) is the most frequent and dangerous PIO phenomenon in human-machine coupling. Almost all fly-by-wire aircraft have experienced PIO due to rate limitation, resulting in serious flight accidents. To ensure safe flight and avoid serious PIO, it is essential to mitigate PIO tendencies from the design stage. Inappropriate servo deflection rate selection is one of the main causes of PIO.
[0003] The servo's deflection rate is directly related to its power. When the servo's deflection command exceeds its deflection capability, a servo rate limitation occurs, causing phase lag and amplitude attenuation. Therefore, increasing the servo's power is an important means of avoiding PIO (Problem-Induced Instability), but this means incurring greater weight, cost, and power costs. Thus, servo selection should not solely focus on achieving a higher deflection rate. During the overall design phase, rationally specifying the servo deflection rate requirements to avoid PIO at minimal cost is of significant engineering importance. Summary of the Invention
[0004] The purpose of this application is to provide a method for determining the servo deflection rate requirement, in order to solve or mitigate at least one of the problems in the prior art.
[0005] On one hand, the technical solution of this application is: a method for determining the deflection rate requirement of a servo motor, comprising:
[0006] Obtain typical flight conditions and calculate the stability augmentation aircraft transfer function without servo motors under the typical flight conditions;
[0007] Under typical flight conditions, the pilot model is obtained according to the Neal-Smith criterion, and the pilot-stabilized aircraft transfer function is obtained based on the stabilized aircraft transfer function and the pilot model.
[0008] The negative reciprocal description function of the servo motor is calculated based on nonlinear system theory, and the amplitude and phase of the negative reciprocal description function of the servo motor are obtained.
[0009] The magnitude and phase of the negative reciprocal description function of the servo and the pilot-stabilized aircraft transfer function are plotted on the same Nichols plot. By adjusting the gain value in the pilot model, the pilot-stabilized aircraft transfer function is made exactly tangent to the negative reciprocal description function of the rate-limiting servo in the Nichols plot, thereby obtaining the gain change value, frequency and magnitude at the tangent point based on the Gap criterion.
[0010] Construct a minimum required expression for the servo deflection rate that includes the gain change value, the frequency at the tangent point, and the amplitude. Calculate the required servo deflection rate based on the minimum required expression for the servo deflection rate.
[0011] Preferably, the driver model is: In the formula, K p For gain, T L T I These are the lead and lag time constants, τ and τ, respectively. p For neuromuscular delay, s is a complex frequency variable.
[0012] Preferably, the pilot-stabilized aircraft transfer function is: G(s) = G θδ (s)•G p (s), where G(s) is the pilot-stabilized aircraft transfer function, G θδ (s) is the transfer function for the stabilized aircraft.
[0013] Preferably, the magnitude of the negative reciprocal describing function of the servo motor is: ;
[0014] The phase is: ;
[0015] In the formula, Let N(K*) be the negative inverse describing function of the servo motor, and K be the describing function of the nonlinear element. * The amplitude of the input sine wave signal.
[0016] Preferably, the minimum required deflection rate of the servo motor is expressed as: In the formula, V L For the minimum deflection rate of the servo motor, A max This represents the maximum deflection angle of the servo motor.
[0017] This application determines the servo deflection rate requirement based on the Gap criterion, which makes up for the shortcomings of previous methods that determined the servo deflection rate requirement from the perspective of avoiding PIO in the design phase. It is of great significance for the rational selection of servos in the design phase of aircraft and avoids the trend of PIO in the future. It effectively reduces unnecessary design costs and improves flight safety. Attached Figure Description
[0018] To more clearly illustrate the technical solutions provided in this application, the accompanying drawings will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application.
[0019] Figure 1 This is a schematic diagram illustrating the method for determining the servo deflection rate requirement of this application.
[0020] Figure 2 The negative inverse description function and the pilot-stabilized aircraft transfer function in one embodiment of this application are plotted together in a Nichols schematic diagram.
[0021] Figure 3 This is a diagram illustrating pitch tracking at different servo speeds according to an embodiment of this application. Detailed Implementation
[0022] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings.
[0023] The Gap criterion is a PIO prediction method based on a rate-limited servo describing function model, an aircraft transfer function model, a Neal-Smith pilot model, and a generalized describing function method. By analyzing the Gap criterion, the physical meaning of the criterion value is obtained. A criterion value greater than 1 indicates that a servo deflection larger than the available servo deflection is likely to induce PIO, which is practically impossible; therefore, no PIO trend occurs in this case. Conversely, a criterion value less than 1 indicates a PIO trend in the human-machine closed-loop system. A criterion value equal to 1 indicates that the PIO trend in the human-machine closed-loop system is at a critical state. Based on the mathematical relationship between the Gap criterion value of 1 and the critical PIO occurrence, this application derives a formula for the minimum servo deflection rate to avoid a PIO trend, and uses this formula to obtain the required servo deflection rate.
[0024] This application proposes a method for determining servo speed requirements based on the Gap criterion theory. This method allows for the selection of appropriate servos during the aircraft design phase, avoiding the unilateral pursuit of servo power (at the cost of weight, hydraulic energy, space, etc.) and effectively preventing the PIO trend that occurs after aircraft development, thereby improving the safe and controllable flight of the aircraft.
[0025] In the aircraft design phase, from the perspective of avoiding PIO (Problem Injection), this application proposes a method for determining the minimum servo deflection rate requirement, providing a basis for selecting a suitable servo for the aircraft design.
[0026] like Figure 1 As shown, the method for determining the servo deflection rate requirement provided in this application includes the following steps:
[0027] Step S10: Obtain the typical flight state that requires precise tracking and trajectory maintenance, and calculate the stability augmentation aircraft transfer function without servos under the typical flight state. .
[0028] This application takes the aircraft pitch channel as an example, and describes the stability-enhanced aircraft transfer function G without servos under a typical flight condition. θδ (s) is: = In the formula, s is a complex frequency variable.
[0029] Step S20: Under typical flight conditions, obtain the pilot model G according to the Neal-Smith criterion. p (s), the pilot-stabilized aircraft transfer function G(s) is obtained based on the stabilized aircraft transfer function and the pilot model.
[0030] Among them, the driver model based on the Neal-Smith criterion In the formula, K p For gain, T L T I These are the lead and lag time constants, τ and τ, respectively. p For neuromuscular delay, s is a complex frequency variable.
[0031] For example, in this embodiment of the application, the driver model that meets the parameter conditions is obtained according to the Neal-Smith criterion as follows: = .
[0032] Based on the stabilized aircraft transfer function and the pilot model, a linear pilot-stabilized aircraft transfer function G(s) = G is constructed. θδ (s)•G p (s).
[0033] Step S30: Calculate the negative reciprocal description function of the servo motor based on nonlinear system theory. The magnitude and phase of the negative reciprocal description function of the servo motor are obtained, where:
[0034] Amplitude:
[0035] Phase:
[0036] In the formula, N(K*) is the describing function of the nonlinear element, and K... * The amplitude of the input sine wave signal.
[0037] Step S40, the negative inverse description function of the servo motor. The magnitude and phase of the pilot-stabilized aircraft transfer function G(s) are plotted in the same Nichols plot. By adjusting the gain value in the pilot model, the pilot-stabilized aircraft transfer function G(s) is made exactly the negative reciprocal description function of the rate-limiting servo. Tangent to the Nichols plot, and thus obtain the gain change value based on the Gap criterion. Frequency ω and amplitude at the tangent point .
[0038] A Nichols plot is a logarithmic graph that plots the amplitude-phase frequency response with frequency ω as a parameter. The vertical axis represents amplitude (dB), and the horizontal axis represents phase (degrees). Frequency ω constitutes an implicit parameter on the curve. For example... Figure 2 The diagram shows the negative reciprocal description function of the aforementioned servo motor in this embodiment of the application. The magnitude and phase of the pilot-stabilized aircraft transfer function G(s) are plotted on the same Nichols plot. The gain change can be obtained by adding a gain to the pilot-stabilized aircraft transfer function G(s) so that it is tangent to the negative inverse describing function of the servo. =2dB, amplitude at the tangent point =0.9, frequency =3.25 rad / s.
[0039] S50, constructing a value including gain variation Frequency ω and amplitude at the tangent point The minimum required servo deflection rate is given by the expression, and the required servo deflection rate is calculated based on this expression.
[0040] In this application, the minimum required servo deflection rate is expressed as: In the formula, V L For the minimum deflection rate of the servo motor, A max This represents the maximum deflection angle of the servo motor.
[0041] For example, in this embodiment of the application, the maximum available deflection of the servo motor =21°, the servo deflection rate can be calculated based on the minimum required expression for the servo deflection rate mentioned above. .
[0042] This application determines the servo deflection rate requirement based on the Gap criterion, which makes up for the shortcomings of previous methods that determined the servo deflection rate requirement from the perspective of avoiding PIO in the design phase. It is of great significance for the rational selection of servos in the design phase of aircraft and avoids the trend of PIO in the future. It effectively reduces unnecessary design costs and improves flight safety.
[0043] like Figure 3The method described in this embodiment of the application is verified based on time-domain simulation using data such as aircraft geometric parameters, mass characteristic parameters, flight envelope, overall aerodynamic characteristics, control surface efficiency, and maximum deflection angle. In this embodiment, the time-domain tracking effect of pitch commands is simulated. For ease of comparison and analysis, the servo deflection rate in the model is taken as both greater than and less than the determined servo deflection requirement rate. Figure 3 The target tracking comparison results show that when the servo deflection rate is greater than the servo deflection rate determined by the method of this application, the pitch command tracking is better. Conversely, when the servo deflection rate is less than the servo deflection rate determined by the method of this application, there is a tendency for PIO to occur during the pitch command tracking process. The rationality of the deflection rate determination method of this application can also be verified by time-domain simulation.
[0044] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.
Claims
1. A method of determining a rudder deflection rate demand, characterized by, The method comprises the following steps: acquiring typical flight states, and calculating a transfer function of a stability-augmented aircraft without aileron at the typical flight states; acquiring a pilot model according to the Neal-Smith criterion at the typical flight states, and obtaining a pilot-stability-augmented aircraft transfer function based on the stability-augmented aircraft transfer function and the pilot model; calculating a negative inverse describing function of the aileron according to a nonlinear system theory, and obtaining an amplitude and a phase of the negative inverse describing function of the aileron; plotting the negative inverse describing function of the aileron and the amplitude and the phase of the pilot-stability-augmented aircraft transfer function on the same Nichols chart, and adjusting a gain value in the pilot model to make the pilot-stability-augmented aircraft transfer function just tangent to the negative inverse describing function of the rate-limited aileron in the Nichols chart, so as to obtain a gain variation value, a frequency at a tangent point and an amplitude based on the Gap criterion; constructing an aileron deflection rate minimum requirement expression containing the gain variation value, the frequency at the tangent point and the amplitude, and calculating an aileron deflection rate requirement according to the aileron deflection rate minimum requirement expression.
2. The method of claim 1, wherein the rudder deflection rate demand is determined based on a difference between the target rudder angle and the current rudder angle. The driver model is: where K p is a gain, T L and T I are lead and lag time constants, respectively, τ p is a neuromuscular delay, and s is a complex frequency variable.
3. The method for determining the servo deflection rate requirement as described in claim 2, characterized in that, The pilot-stabilized aircraft transfer function is: G(s) = G θδ (s) • G p (s), where G(s) is the pilot-stabilized aircraft transfer function, G θδ (s) is the stabilized aircraft transfer function.
4. The method of claim 3, wherein the rudder deflection rate demand is determined by: ###0001### where: ###0002### ###0003### The amplitude of the negative inverse describing function of the rudder is: ; Phase is: ; wherein N(K*) is a non-linear element, K * is the amplitude of the input sinusoidal signal.
5. The method of claim 4, wherein the rudder deflection rate demand is determined by: ###0001### where: ###0002### ###0003### The rudder deflection rate minimum requirement expression is: , wherein V L is the rudder minimum deflection rate, A max is the rudder maximum deflection angle.