RU2820152C1 - Method of aircraft flight dynamics simulation - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: disclosed is a method of simulating flight dynamics of an aircraft on a flight simulator, which includes conversion of signals of overloads and angular accelerations coming from a unit of a mathematical model of the aircraft and receiving at the output of the signals of the given linear and angular position of the cockpit of the flight simulator, which are supplied to the actuating part of the mobility system. Conversion of overload and angular acceleration signals coming from the aircraft mathematical model unit is performed due to transmission of signals of overloads and angular accelerations through high-pass filters for linear longitudinal channel, linear vertical channel, linear side channel, angular channel by roll, angular channel by pitch, angular channel by yaw and low-pass filters for angular channel by roll and angular channel by pitch, wherein each filter has its input signal limiter and input signal amplifier. Additionally, from the aircraft mathematical model unit, two additional signals are supplied for buffeting – a buffeting signal in a linear vertical channel and a buffeting signal in a linear side channel, these signals are passed through high-pass filters, wherein each filter has its input signal limiter and input signal amplifier, after which the obtained signals are summed with signals obtained at the outputs of the high-pass filters in the linear vertical and linear side channels, respectively.

EFFECT: disclosed is a method of simulating flight dynamics of an aircraft.

1 cl, 5 dwg

Description

The invention relates to the field of semi-natural modeling of the flight dynamics of aircraft on flight stands and simulators.

To study the stability and controllability of aircraft, flight stands are currently widely used (RU 2249856 C1, RU 108685 U1, RU 94025128 A1, RU 2737246 C2, etc.), which include cockpit mobility systems (RU 2321073 C1, RU 2129305 C1 , F.M.Nieuwenhuizen, H.H.Bülthoff, “The MPI cybermotion Simulator: A Novel Research Platform to Investigate Human Control Behavior” Jornal of Computing Science and Engineering Vol.7, No.2, June 2013, pp.122-131), allowing to reproduce linear overloads and angular accelerations (hereinafter referred to as acceleration signals) acting on the pilot in flight. The amplitude-phase frequency characteristics (APFC) of the executive part of such systems, as a rule, provide the best quality of reproduction of the input signal at piloting frequencies (0.1-1.5 Hz), while at frequencies above 2-3 Hz the AFC characteristic has a significant decrease in the amplitude characteristic (about 6 dB/decade). When modeling critical flight conditions, an important aspect is the reproduction of aerodynamic buffeting. The frequency range of such a signal lies significantly higher than piloting frequencies (2.5-8 Hz), so its reproduction on flight stands and simulators using classical approaches to converting g-forces and angular accelerations into specified cabin movements currently poses significant difficulties.

There is a known method of converting overload and angular acceleration signals coming from a block of a mathematical model of an aircraft into specified movements of the cockpit of a flight stand or simulator by passing the overload and angular acceleration signals through a set of high- and low-pass filters with their own gain factors and input signal limitations (Conrad, B. , Schmidt, S.F.: A study of techniques for calculating motion drive signals for flight simulators. NASA CR-114345 (1971), Bjorn Canrad, J.G. Douvillier, S.F. Schmidt, Washout circuit design for multi-degrees-of-freesom moving base simulators, Proceedings of the AIAA Visual and Motion Simulation Conference, Palo Alto (CA), September 10, 1973, vol. 12, 1973) and receiving the output signals of the specified position of the cockpit of the flight stand/simulator entering the executive part of the mobility system. Within the framework of such a structure, when trying to reproduce buffeting signals, the reproduced signal will have a significantly lower amplitude compared to the signal specified from the block of the mathematical model, due to a decrease in the amplitude characteristics of the mobility system at frequencies characteristic of buffeting. At the same time, increasing the gain for the input buffet signal will not lead to an increase in the reproduced buffet signal, since the buffet signal is passed through, among other things, an input signal limiter configured to the input signal level characteristic of the signal at piloting frequencies. Therefore, within the framework of the existing structure of cabin motion control algorithms, it is not possible to achieve satisfactory quality of reproduction of the buffet signal.

In addition, a method is known (Reid, L., Nahon, M.A.: Flight simulation motion-base drive algorithms: part 1. Developing and testing equations. University of Toronto, Technical report (1985), Reid, L., Nahon, M.A.: Flight simulation motion-base drive algorithms: part 2. Selecting the system parameters. University of Toronto, Technical report (1986), Reid, L., Nahon, M.: Flight simulation motion-base drive algorithms Part 3: Pilot evaluations. (1986)), different from (Conrad, B., Schmidt, S.F.: A study of techniques for calculating motion drive signals for flight simulators. NASA CR-114345 (1971), Bjorn Canrad, J.G. Douvillier, S.F. Schmidt, Washout circuit design for multi-degrees-of-freesom moving base simulators, Proceedings of the AIAA Visual and Motion Simulation Conference, Palo Alto (CA), 10 September 1973, vol.12 (1973)) by the presence of a low-pass filter in the channel of coordinated cockpit tilts for reproduction low frequency linear motion signal.

The closest in technical essence to the stated one is “A method for controlling the movements of a flight simulator and a flight simulator that implements such a method” (RU 2425409 C2), including linear and angular accelerations perceived by the pilot, as a result of which the angular velocity of roll and angular velocity of yaw, as well as lateral overload, calculated in accordance with the model of the simulated aircraft at the center of gravity of the simulated aircraft, are converted into the linear and angular position of the simulator cabin, taking into account the linear offset of the pilot's cabin relative to the center of gravity of the aircraft, and includes the calculation of the roll angle of the simulator cabin in accordance with the roll angle simulated aircraft by correcting the initially calculated value of the roll angle with a correction coefficient proportional to the transverse overload; in addition, the overload acting in the transverse channel at the location of the pilot in the simulated aircraft is decomposed into a first component and a second component, wherein the first component is associated with the overload at the center of gravity of the simulated aircraft, and the second component has a first term associated with accelerations due to the yaw angular motion and a second term associated with the roll angular motion. This method makes it possible to well simulate overloads and angular velocities in the cockpit, but does not affect the bandwidth of the mobility system of a flight stand or simulator, and therefore does not allow reproducing the buffet signal.

The objective of the claimed method is to eliminate the above disadvantages.

The technical result of the claimed method is to increase the reliability of semi-natural modeling of critical flight conditions due to high-quality reproduction of aerodynamic buffeting, to increase the efficiency of ground-based studies of stability and controllability characteristics by expanding the range of tasks studied on ground-based flight stands, to increase the efficiency of training flight personnel on flight simulators and to improve safety flight.

The technical result is achieved by the features of a method for simulating the flight dynamics of an aircraft on a flight stand or simulator, including converting the overload and angular acceleration signals coming from the block of the mathematical model of the aircraft and receiving at the output signals of a given linear and angular position of the cockpit of the flight stand or simulator, entering the executive part of the system mobility. The transformation of the overload and angular acceleration signals coming from the block of the mathematical model of the aircraft occurs by passing the overload and angular acceleration signals through high-pass filters for the linear longitudinal channel, linear vertical channel, linear lateral channel, roll angular channel, pitch angular channel, angular channel yaw and low-pass filters for the roll angular channel and pitch angular channel. In this case, each filter has its own input signal limiter and input signal amplifier. Additionally, two signals for buffeting are supplied from the block of the mathematical model of the aircraft - a buffeting signal in a linear vertical channel and a buffeting signal in a linear lateral channel. These signals are passed through high-pass filters, each filter having its own input limiter and input amplifier. The received signals are summed with the signals obtained at the outputs of high-pass filters in the linear vertical and linear side channels, respectively.

Ground-based flight simulation tools can be divided into two groups: flight stands and flight simulators (aviation simulators).

Flight simulators and flight stands are similar in structure. The fundamental thing is that all elements of both the flight stand and the flight simulator are combined into a closed control loop, similar to the real closed loop of the aircraft-pilot. The fundamental difference lies in the purpose of flight stands and flight simulators, which is reflected in the specific appearance of their constituent elements. In terms of flight control, a flight simulator is an analogue of a specific aircraft and a means of training a pilot to fly this aircraft. Therefore, the flight deck must be equipped in exact accordance with the specific prototype aircraft. In terms of speed, memory capacity and other parameters, the aircraft dynamics computer must be sufficient to reproduce the movement process of a particular aircraft, but have minimal redundancy in this part for reasons of minimal cost. The same principle applies to equipment for recording and diagnosing flight results, which should be minimally sufficient to evaluate the learning process and results. From the above it follows that the possibilities of studying the dynamic characteristics of a pilot in a flight simulator are very limited. Flight stands, which are designed for experimental research and testing of technical solutions in the field of manual control of an aircraft (requirements for the flight characteristics of aircraft, selection of stability and controllability characteristics of specific aircraft being designed, testing of the principles of functioning of specific automatic control systems) have significantly greater capabilities in this regard [A .V.Efremov, A.V.Ogloblin, A.N.Predtechensky, V.V.Rodchenko / Pilot as a dynamic system, Moscow, Mechanical Engineering, 1992, pp. 283-284].

Thus, it is advisable to use the claimed method both on flight stands in order to increase the realism of modeling critical flight conditions and, accordingly, the effectiveness of ground-based studies of the stability and controllability of aircraft, and on flight simulators in order to improve the quality and efficiency of flight crew training to prevent an aircraft from being hit into a stall, and, in the event of a stall, to bring the aircraft out of the stall and into normal flight.

The method is shown schematically in Fig. 1, where:

- longitudinal overload formed in the block of the mathematical model of the aircraft;

- increment of normal overload generated in the block of the mathematical model of the aircraft;

- lateral overload formed in the block of the mathematical model of the aircraft;

- angular acceleration of the roll, formed in the block of the mathematical model of the aircraft;

- angular yaw acceleration generated in the block of the mathematical model of the aircraft;

- angular acceleration of the pitch generated in the block of the mathematical model of the aircraft;

- contribution of buffeting to normal overload;

- contribution of buffeting to lateral overload;

- increment of normal overload, reproduced on a flight bench/simulator;

- lateral overload, reproduced on a flight bench/simulator;

X _cab , Y _cab , Z _cab - linear movements of the cockpit of the flight stand/simulator;

ϑ _cab , γ _cab , ψ _cab - angular movements of the cockpit of the flight stand/simulator.

The linear longitudinal channel includes 1 high-pass filter and converts the longitudinal overload signal coming from the block of the mathematical model of the aircraft into a signal of a given longitudinal movement of the flight bench/simulator cabin, transmitted to the executive part of the mobility system.

The linear vertical channel includes the sum of 2 high-pass filters that convert the normal g-force increment signal and the buffet signal for the vertical channel into a signal of a given vertical movement of the flight stand/simulator cabin, transmitted to the executive part of the mobility system.

The linear side channel includes the sum of 2 high-pass filters that convert the lateral overload signal and the buffet signal for the side channel into a signal of a given lateral movement of the flight stand/simulator cabin, transmitted to the executive part of the mobility system.

The angular roll channel includes the sum of a high-pass filter and a low-pass filter that converts lateral overload and angular acceleration of the roll into a signal of a given angular position of the cockpit/roll simulator, transmitted to the executive part of the mobility system.

The pitch angular channel includes the sum of a high-pass filter and a low-pass filter that converts longitudinal overload and pitch angular acceleration into a signal of a given angular position of the flight bench/pitch simulator cabin, transmitted to the executive part of the mobility system.

The yaw angular channel includes 1 high-pass filter and converts the yaw angular acceleration into a signal of a given angular position of the flight stand/yaw simulator cabin, transmitted to the executive part of the mobility system.

The block with additional channels for buffeting is marked with a dotted line.

The implementation of the method is carried out in the environment of a modeling complex of a flight stand/simulator in the circuit: Block of a mathematical model of an aircraft - the executive part of the mobility system, by connecting in parallel with the channels for generating vertical and lateral movement of the cockpit of a flight stand/simulator an additional block for reproducing buffeting with two high-pass filters 3rd order:

Where:

- transfer functions of high-pass filters for vertical and side channels to reproduce buffeting;

- scaling coefficients of high-pass filters for vertical and side channels to reproduce buffeting;

- time constants of second-order high-pass filters for the vertical and side channels to reproduce buffeting;

- time constants of first-order high-pass filters for the vertical and side channels to reproduce buffeting;

- damping of high-pass filters for vertical and side channels to reproduce buffeting;

- Laplace operator.

The expression for reproducible overloads in the vertical and lateral channels for the classical structure of cabin motion control algorithms has the following form:

Where:

, - transfer functions of high-pass filters having the same structure as the filters for reproducing buffeting, but differing in the actual values of the gain factors, restrictions on the maximum amplitude of the input signal, time constants of the high-pass filters, and damping high pass filters:

Where:

- scaling coefficients of high-pass filters for vertical and side channels to reproduce linear overloads with frequencies characteristic of piloting;

- time constants of second-order high-pass filters for the vertical and lateral channels to reproduce linear overloads with frequencies characteristic of piloting;

- time constants of first-order high-pass filters for the vertical and lateral channels to reproduce linear overloads with frequencies characteristic of piloting;

- damping of high-pass filters for vertical and side channels to reproduce linear overloads with frequencies characteristic of piloting;

Taking into account the proposed method, the expressions for the vertical and lateral channels are transformed to the form:

+

The claimed method was tested on the PSPK-102 TsAGI flight stand and is used in bench studies related to reaching high angles of attack for transport category aircraft. To demonstrate the performance of the claimed method, the buffet signal was supplied with a frequency of 4.5 Hz in the vertical channel and 7.4 Hz in the lateral channel, which corresponds to the buffet frequencies for a typical medium-range transport category aircraft. If the buffeting signal was supplied to the mobility system through the standard linear vertical and linear lateral channels together with overloads arising as a result of the movement of the aircraft from the pilot's control actions, the level of the buffeting signal reproduced by the mobility system was orders of magnitude lower than the specified one and insufficient to give the pilot additional warning information about reaching high angles of attack and about the aircraft approaching a stall.

In the case of using the proposed method, the following filter parameters were selected:

longitudinal channel

HF: K _xh =0.3, T _xh =0.7, ξ _xh =0.7, τ _xh =2;

LF: K _xh =0.3, T _xh =0.7, ξ _xh =0.7;

vertical channel

HF: K _{y h} =0.3, T _{y h} =0.7, ξ _{y h} =0.7, τ _{y h} =3;

HF for buffeting: K _ybuff =1.0, T _ybuff =0.2, ξ _ybuff =0.7, τ _ybuff =3;

side channel

HF: K _{z h} =0.3, T _{z h} =0.7, ξ _{z h} =0.7, τ _{z h} =10;

HF for buffeting: K _zbuff =2.5, T _zbuff =0.2, ξ _zbuff =0.7, τ _zbuff =10;

LF: K _{z l} =0.3, T _{z l} =0.7, ξ _{z l} =0.7;

roll channel

HF: K _wx =0.3, T _wx =0.7, ξ _wx =0.7;

pitch channel

HF: K _{w z} =0.3, T _{w z} =0.7, ξ _{w z} =0.7;

yaw channel

HF: K _{w y} =0.3, T _{w y} =0.7, ξ _{w y} =0.7.

When using such parameters, the total amplitude-frequency response of high-pass filters in the vertical channel received the form shown in Fig. 2, and for the side channel the form shown in Fig. 3. In this way, it was possible to achieve the desired level of the reproduced buffeting signal in both the vertical and lateral channels, which is confirmed by the graphs of the spectral characteristics of the normal and lateral overload signals shown in Fig. 4 and Fig. 5, specified from the block of the mathematical model of the aircraft and the overloads reproduced by the mobility system for vertical and lateral channels, respectively. The results obtained confirm the specified technical result.

Thus, the claimed invention makes it possible to increase the realism of modeling critical flight conditions and, accordingly, the efficiency of ground-based studies of the stability and controllability of aircraft on flight stands and the efficiency of training flight personnel on flight simulators and improve flight safety.

Claims (1)

A method for simulating the flight dynamics of an aircraft on a flight stand or simulator, including converting the overload and angular acceleration signals coming from the block of the mathematical model of the aircraft and receiving at the output signals of a given linear and angular position of the cockpit of the flight stand or simulator, entering the executive part of the mobility system, wherein the conversion signals of overloads and angular accelerations coming from the block of the mathematical model of the aircraft occurs by passing the signals of overloads and angular accelerations through high-pass filters for a linear longitudinal channel, a linear vertical channel, a linear lateral channel, a roll angular channel, a pitch angular channel, an angular channel along yaw and low-pass filters for the roll angular channel and the pitch angular channel, each filter having its own input signal limiter and input signal amplifier, characterized in that two additional signals for buffeting are supplied from the block of the mathematical model of the aircraft - the buffeting signal in the linear vertical channel and the buffet signal in the linear side channel, these signals are passed through high-pass filters, each filter having its own input signal limiter and input signal amplifier, after which the resulting signals are summed with the signals obtained at the outputs of the high-pass filters in the linear vertical and linear side channels, respectively.

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