A method of indicating airspeed control based on speed differential signal

Abstract

The present invention belongs to the field of aircraft flight control, and specifically relates to an indicated airspeed control method based on a speed differential signal. The method adopts an inner and outer loop cascade control structure. The outer loop adopts indicated airspeed control, generates a speed differential instruction and sends it to the inner loop. The inner loop adopts speed differential control based on robust servo theory; the speed differential signal phase leads the indicated airspeed signal, and the inner loop contains an integral term of the speed differential deviation. The present invention adopts a speed differential signal that is ahead of the indicated airspeed phase as the inner loop control signal, which can produce a faster control effect on the change of the indicated airspeed and make the indicated airspeed control response faster. Throttle self-balancing can be achieved through the integration of the speed differential deviation, without the need to design a throttle feedforward value, thereby reducing the strong dependence on aerodynamic parameters and engine data.

Description

Technical Field

[0001] The invention belongs to the field of aircraft flight control, and in particular relates to an indicated airspeed control method based on a speed differential signal. Background Art

[0002] The rapid and stable control of the indicated airspeed of a UAV is the premise for ensuring the flight safety of the UAV and is also the key to executing the mission. Nowadays, the indicated airspeed control of UAVs is mainly based on engine throttle control. At present, the closed-loop control of the indicated airspeed of the UAV engine throttle is mostly based on the PI or PID control of the indicated airspeed, and its control law is generally as follows:

[0003]

[0004] or

[0005]

[0006] Where Ax is the axial acceleration, To balance the throttle, V IAS is the indicated airspeed, Indicates airspeed control command.

[0007] This control scheme has a simple and clear structure, simple design, easy engineering implementation, and a wide range of applications. However, it still has many disadvantages. First, The design of is extremely dependent on the accuracy of aerodynamic data and engine thrust data. If the value is not given properly, the indicated airspeed control effect is not good, which is particularly prominent in the design of low-cost UAVs. Second, the main principle of the current control law design is error feedback control, that is, the speed adjustment starts after the disturbed indicated airspeed of the UAV deviates from the predetermined target value, and there is a large lag phenomenon. Third, the integrator control parameters are small. If the trim throttle is not selected properly, the integral time required to eliminate the static error is long, the effect is poor, and the integral parameter setting is cumbersome. Fourth, if Ax is used as the damping term of the speed, because Ax is the acceleration under the body axis, the acceleration and deceleration characteristics of the indicated airspeed cannot be accurately characterized under large attitude conditions, and a good damping effect cannot be achieved. In view of the above drawbacks, it is of great significance to study a new indicated airspeed control method. Summary of the invention

[0008] In order to realize automatic throttle trim and ensure fast indicated airspeed control without static error, the present invention discloses a speed control method based on speed differential.

[0009] In order to achieve the above-mentioned invention object, the technical solution provided by this application is as follows:

[0010] The invention discloses an indicated airspeed control method based on a speed differential signal, which adopts an inner and outer loop cascade control structure. The outer loop adopts indicated airspeed control, generates a speed differential instruction and sends it to the inner loop, and the inner loop adopts speed differential control based on robust servo theory. The speed differential signal phase leads the indicated airspeed signal, which produces a faster control effect on the change of the indicated airspeed and makes the indicated airspeed control respond faster. The inner loop contains an integral term of the speed differential deviation, which improves the type of the system, not only enhances the ability of the system to suppress external disturbances, but also makes the steady-state error output by the control system zero, and realizes zero-static-error tracking of the indicated airspeed instruction. The throttle self-balancing can be realized by integrating the speed differential deviation, without designing the throttle feedforward value, and reducing the strong dependence on aerodynamic parameters and engine data.

[0011] The outer loop of the engine indicated airspeed control uses the indicated airspeed signal as the control quantity to generate a speed differential instruction and send it to the inner loop. The controller structure is as follows:

[0012]

[0013] in is the speed differential instruction, V IAS To indicate the airspeed signal, To indicate the airspeed signal command, K3 is the control gain.

[0014] The inner loop of the engine indicated airspeed control adopts speed differential control based on robust servo theory, and its controller structure is as follows:

[0015]

[0016] where δ p is the throttle opening command, is the speed differential signal, is the speed differential signal command, K1 and K2 are the control gains.

[0017] The speed differential signal can be output by the atmospheric data system. When it cannot be output by the sensor, it can be constructed by indicating the airspeed signal. The construction method is as follows:

[0018]

[0019]

[0020] in, is the velocity differential value after filtering of the kth beat, is the velocity differential value after filtering for the k-1th beat, is the k-th velocity differential value calculated from the indicated airspeed, T is the sampling period, T1 is the time constant, n is the number of beats used to smooth the indicated airspeed signal.

[0021] The advantages of the present invention are:

[0022] 1. The present invention adopts a speed differential signal that is ahead of the indicated airspeed phase as an inner loop control signal, which can produce a faster control effect on the change of the indicated airspeed and make the indicated airspeed control response faster.

[0023] 2. The present invention can realize throttle self-balancing through the integration of speed differential deviation, without the need to design throttle feedforward value, thus reducing the strong dependence on aerodynamic parameters and engine data.

[0024] 3. The internal loop of the present invention contains an integral term of the speed differential deviation, which improves the type of the system. It not only enhances the system's ability to suppress external disturbances, but also makes the steady-state error output by the control system zero, thereby achieving zero-static-error tracking of the indicated airspeed command. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is the outer loop control structure of the indicated airspeed controller based on speed differential.

[0026] Figure 2 It is the inner loop control structure of the indicated airspeed controller based on speed differential.

[0027] Figure 3 It is the simulation curve of the traditional indicated airspeed PI controller.

[0028] Figure 4 It is a simulation curve after adopting the present invention. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is to explain the present invention rather than to limit the present invention. Based on the embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0030] The specific implementation method of the present invention is described below with reference to the accompanying drawings and examples, but the present invention is not limited to this embodiment.

[0031] Example 1

[0032] The invention discloses an indicated airspeed control method based on a speed differential signal, which adopts an inner and outer loop cascade control structure. The outer loop adopts indicated airspeed control, generates a speed differential instruction and sends it to the inner loop, and the inner loop adopts speed differential control based on robust servo theory. The speed differential signal phase leads the indicated airspeed signal, which produces a faster control effect on the change of the indicated airspeed and makes the indicated airspeed control respond faster. The inner loop contains an integral term of the speed differential deviation, which improves the type of the system, not only enhances the ability of the system to suppress external disturbances, but also makes the steady-state error output by the control system zero, and realizes zero-static-error tracking of the indicated airspeed instruction. The throttle self-balancing can be realized by integrating the speed differential deviation, without designing the throttle feedforward value, and reducing the strong dependence on aerodynamic parameters and engine data.

[0033] The outer loop of the engine indicated airspeed control uses the indicated airspeed signal as the control quantity to generate a speed differential instruction and send it to the inner loop. The controller structure is as follows:

[0034]

[0035] in is the speed differential instruction, V IAS To indicate the airspeed signal, To indicate the airspeed signal command, K3 is the control gain.

[0036] The inner loop of the engine indicated airspeed control adopts speed differential control based on robust servo theory, and its controller structure is as follows:

[0037]

[0038] where δ p is the throttle opening command, is the speed differential signal, is the speed differential signal command, K1 and K2 are the control gains.

[0039] The speed differential signal can be output by the atmospheric data system. When it cannot be output by the sensor, it can be constructed by indicating the airspeed signal. The construction method is as follows:

[0040]

[0041]

[0042] in, is the velocity differential value after filtering of the kth beat, is the velocity differential value after filtering for the k-1th beat, is the k-th velocity differential value calculated from the indicated airspeed, T is the sampling period, T1 is the time constant, n is the number of beats used to smooth the indicated airspeed signal.

[0043] Example 2

[0044] An indicated airspeed control method based on speed differential signal adopts an inner and outer loop cascade control structure. The outer loop adopts indicated airspeed control to generate speed differential instructions and send them to the inner loop. The inner loop adopts speed differential control based on robust servo theory. The speed differential signal phase leads the indicated airspeed signal, which can produce a faster control effect on the change of indicated airspeed and make the indicated airspeed control response faster; the inner loop contains an integral term of speed differential deviation, which improves the type of the system, not only enhances the system's ability to suppress external disturbances, but also makes the steady-state error of the control system output zero, and realizes zero-static tracking of the indicated airspeed instruction; the throttle self-balancing can be realized through the integration of the speed differential deviation, without the need to design the throttle feedforward value, which reduces the strong dependence on aerodynamic parameters and engine data.

[0045] The speed differential signal can be output by the atmospheric data system. When it cannot be output by the sensor, it can be constructed by indicating the airspeed signal. The construction method is as follows:

[0046]

[0047]

[0048]

[0049]

[0050] Where T is the sampling period, T1 is the time constant, and n is the number of beats used to smooth the indicated airspeed signal.

[0051] Substitute the airspeed signal measured by the atmospheric system into (1) and calculate the indicated airspeed of the k-1th beat after smoothing by n beats: Substitute the airspeed signal measured by the atmospheric system into (2) and calculate the k-th indicated airspeed after n-beat smoothing: The indicated airspeed of the k-1th beat after smoothing over n beats and the kth beat indicated airspeed after n beats smoothing Substitute (3) and solve to get the k-th beat velocity differential value The k-th beat velocity differential value Substitute (4) to obtain the k-th beat velocity differential value after low-pass filtering: Then the speed differential signal is obtained.

[0052] Figure 1 The outer loop control structure of the indicated airspeed controller based on speed differential is shown, and its control law is:

[0053]

[0054] Among them, K3 is the control gain.

[0055] Tracking (5) indicated airspeed given target value Calculate the speed differential command signal to the inner loop controller.

[0056] Figure 2 The inner loop control structure of the indicated airspeed controller based on speed differential is shown, and its control law is:

[0057]

[0058] Among them, K1 and K2 are control gains.

[0059] Tracking (6) Speed ​​differential given target value Calculate the target engine speed (δ p ) and sent to the engine control unit to control the drone to maintain the current speed.

[0060] Figure 3 The simulation curve of the traditional PI indicated airspeed control based on a certain type of UAV is given. Figure 4 A simulation curve based on a certain type of UAV using the indicated airspeed control method of the present invention is given. It can be seen from the figure that at about 92s of the simulation time, the airspeed target increases from 69.5m / s to 111.1m / s. Compared with the traditional indicated airspeed control method, the indicated airspeed control method proposed by the present invention is faster and has no static error in tracking. The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

Claims

1. An indicated airspeed control method based on a speed differential signal, characterized in that: An inner and outer loop cascade control structure is adopted. The outer loop adopts indicated airspeed control, generates speed differential instructions and sends them to the inner loop. The inner loop adopts speed differential control based on robust servo theory. The speed differential signal phase leads the indicated airspeed signal, and the inner loop contains an integral term of the speed differential deviation. The outer loop uses indicated airspeed control to generate speed differential instructions and send them to the inner loop. The controller structure is as follows: in is the speed differential instruction, V IAS To indicate the airspeed signal, is the airspeed signal command, K3 is the control gain; The inner loop adopts speed differential control based on robust servo theory, and its controller structure is as follows: where δ p is the throttle opening command, is the speed differential signal, is the speed differential signal command, K1 and K2 are the control gains.

2. The indicated airspeed control method based on the speed differential signal according to claim 1, characterized in that: The speed differential signal is output by the atmospheric data system. When it cannot be output by the sensor, it can be constructed by indicating the airspeed signal. The construction method is as follows: in, is the velocity differential value after filtering of the kth beat, is the velocity differential value after filtering for the k-1th beat, is the k-th velocity differential value calculated from the indicated airspeed, T is the sampling period, T1 is the time constant, n is the number of beats used to smooth the indicated airspeed signal.

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