A method for controlling the altitude of a drone using only linear angle accelerometer measurements

Abstract

The present invention relates to a method for controlling the altitude of a drone by measuring linear acceleration and angular acceleration. The method measures the vertical acceleration and pitch acceleration of the drone by installing a linear accelerometer and an angular accelerometer, and obtains the vertical velocity, vertical height, pitch velocity, and pitch angle by double integration. At the same time, a mixed approximate differential of the pitch angle error is solved by an integer-order and fractional-order approximate differential method to provide damping for the control scheme. The uncertainty interference in the vertical acceleration, pitch acceleration, pitch velocity, pitch error, etc. is compensated by the design of an adaptive control law through a double-layer sliding mode control method of an inner and outer loop, and finally forms a pitch angle desired signal and a final control signal of the pitch channel, so as to realize tracking control of the drone to a given altitude. The entire control method has the advantages of simple measurement and economical saving.

Description

Technical Field

[0001] The present invention relates to the field of unmanned aerial vehicle motion control and fixed-altitude tracking flight control, and in particular to a method for controlling the altitude of an unmanned aerial vehicle using only a linear angular accelerometer for measurement. Background Art

[0002] In recent years, drone technology has achieved rapid development worldwide, and has been widely used in both military and civilian fields. Among them, the altitude control in drone flight control occupies a core position in the entire control, which affects the safety of drone flight. In traditional altitude control, most of them need to measure the precise attitude and precise position of the drone, such as using a gyroscope to measure the pitch angle, using a radio altimeter to measure the altitude of the drone, and also need to use a rate gyroscope to measure the attitude angular rate to improve the stability of the control system. In general, the introduction of the above-mentioned high-precision measurement device will greatly increase the economic cost of the overall flight control solution of the drone, which is unfavorable to the competitiveness in the civilian field or the field of low-end drones. Based on the above background reasons, the present invention proposes a complete set of methods for completing the altitude control of the drone by installing only a linear accelerometer and an angular accelerometer, and adopts a hybrid differential technology to improve the stability of the system, and adopts an adaptive technology to compensate for the disturbance problem caused by insufficient measurement accuracy, so that the entire control method has a high engineering application value.

[0003] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present invention, and therefore may include information that does not constitute prior art known to ordinary technicians in the field. Summary of the invention

[0004] The purpose of the present invention is to provide a method for controlling the altitude of a UAV using only a linear angular accelerometer for measurement, thereby overcoming the problems of complex UAV altitude control measurement equipment and low control quality caused by limitations and defects of related technologies.

[0005] According to one aspect of the present invention, a method for controlling the altitude of an unmanned aerial vehicle using only a linear angular accelerometer for measurement is provided, comprising the following steps:

[0006] Step S10, installing a linear accelerometer to measure the vertical acceleration of the UAV, installing an angular accelerometer to measure the pitch acceleration signal of the UAV, then integrating the vertical acceleration signal to obtain a vertical velocity signal, and then integrating the vertical velocity signal to obtain a height signal; setting a height expectation signal according to the flight mission requirements, and comparing it with the height signal to obtain a height error signal; and switching the integration to obtain a height error upper integral signal and a height error lower integral signal, and superimposing them to obtain a height error full integral signal.

[0007] Step S20, forming a height loop combined sliding mode signal according to nine signals including height error signal, vertical velocity signal, height error full integral signal, height error upper half integral signal, height error lower half integral signal, vertical acceleration adaptive signal, pitch angle acceleration adaptive signal, height error adaptive signal, and vertical velocity adaptive signal; and designing corresponding vertical acceleration adaptive law, pitch angle acceleration adaptive law, height error adaptive law, and vertical velocity adaptive law.

[0008] Step S30, combining the sliding mode signal of the altitude loop and superimposing the sliding mode nonlinear compensation signal, the sliding mode linear compensation signal, the vertical acceleration compensation signal, the pitch angle angular velocity compensation signal, the altitude error signal, the vertical velocity signal, the altitude error upper half integral signal, and the altitude error lower half integral signal to form a pitch angle expected signal, and designing the automatic updating rule of the corresponding compensation signal.

[0009] Step S40, integrating the pitch angular acceleration signal to obtain a pitch angular velocity signal, then integrating the pitch angular velocity signal to obtain a pitch angle signal, and comparing the pitch angle signal with the pitch angle expected signal to obtain a pitch angle error signal; then designing an integer-order approximate differentiator to obtain a pitch angle error integer-order approximate differential signal; then designing a one-tenth-order approximate fractional differentiator to obtain a pitch angle fractional-order approximate differential signal, and once again passing through a one-tenth-order approximate fractional differentiator and superimposing the pitch angle error integer-order approximate differential signal, to obtain a pitch angle error integer-fractional mixed approximate differential signal.

[0010] Step S50, switching integration is performed according to the pitch angle error signal to obtain a pitch angle error upper integral signal and a pitch angle error lower integral signal, and superposition is performed to obtain a pitch angle error full integral signal; a pitch angle error inner loop sliding mode signal is formed by superimposing the pitch angle error signal with the vertical velocity signal, the pitch angle error full integral signal, the pitch angle error upper integral signal, the pitch angle error lower integral signal, the vertical acceleration inner loop adaptive signal, the pitch angle acceleration inner loop adaptive signal, the vertical velocity inner loop adaptive signal and the pitch angle error inner loop adaptive signal; and an adaptive rule of an inner loop adaptive coefficient is designed according to the pitch angle error inner loop sliding mode signal.

[0011] Step S60, according to the pitch angle error inner loop sliding mode signal, design the inner loop sliding mode nonlinear compensation signal, the inner loop vertical acceleration nonlinear compensation signal, the inner loop sliding mode linear compensation signal, the inner loop pitch angle acceleration compensation signal, the inner loop pitch angle velocity linear compensation signal, and the inner loop pitch angle velocity nonlinear compensation signal; at the same time, design the adaptive update law of the compensation coefficient; and superimpose the pitch angle error signal, the pitch angle error integer fractional order mixed approximate differential signal and the pitch angle error inner loop sliding mode signal to form the final height loop control total signal, which is transmitted to the pitch rudder system of the UAV to realize the tracking control of the UAV to the desired height.

[0012] In an exemplary embodiment of the present invention, a linear accelerometer is installed to measure the vertical acceleration of the UAV, an angular accelerometer is installed to measure the pitch acceleration signal of the UAV, and then the vertical acceleration signal is integrated to obtain a vertical velocity signal, and then the vertical velocity signal is integrated to obtain a height signal; a height expectation signal is set according to the flight mission requirements, and compared with the height signal to obtain a height error signal; and an upper integral signal of the height error and a lower integral signal of the height error are obtained by switching the integral, and the height error full integral signal is obtained by superposition, which includes:

[0013] v y =∫a y dt;h y =∫v y dt;

[0014] e h =h y -h d ;

[0015]

[0016]

[0017] s h =s h1 +s h2 ;

[0018] where a y is the vertical acceleration signal, v y is the vertical speed signal, is the pitch angle acceleration signal; h d To set the altitude expectation signal according to the flight mission requirements; h y is the UAV height signal, e h is the UAV height error signal; s h1 is the integrated signal of the height error, s h2 is the integrated signal under height error, s h is the fully integrated signal of the height error.

[0019] In an exemplary embodiment of the present invention, a height loop combined sliding mode signal is formed according to nine signals including a height error signal, a vertical velocity signal, a height error full integral signal, a height error upper half integral signal, a height error lower half integral signal, a vertical acceleration adaptive signal, a pitch angle acceleration adaptive signal, a height error adaptive signal, and a vertical velocity adaptive signal; and corresponding vertical acceleration adaptive law, pitch angle acceleration adaptive law, height error adaptive law, and vertical velocity adaptive law are designed, including:

[0020]

[0021]

[0022]

[0023]

[0024]

[0025]

[0026]

[0027]

[0028] s1=c1e h +c2v y +c3s h +w1+w2+w3+w4+c8s h1 +c9s h2 ;

[0029] in is the pitch acceleration signal of the drone measured by the angular accelerometer, w1 is the vertical acceleration adaptive signal, w2 is the pitch acceleration adaptive signal, w3 is the altitude error adaptive signal, w4 is the vertical velocity adaptive signal, s1 is the altitude loop combined sliding mode signal; c1, c2, c3, c8, c9, ε1 are constant parameters; is the vertical acceleration adaptive coefficient, is the pitch acceleration adaptation coefficient, is the height error adaptive coefficient, is the vertical speed adaptation coefficient; k c4 , k c5 , k c6 , k c7 It is a constant parameter used to adjust the speed of convergence of the corresponding adaptive coefficient.

[0030] In an exemplary embodiment of the present invention, the method of combining the sliding mode signal of the altitude loop and superimposing the sliding mode nonlinear compensation signal, the sliding mode linear compensation signal, the vertical acceleration compensation signal, the pitch angle angular velocity compensation signal, the altitude error signal, the vertical velocity signal, the altitude error upper half integral signal, and the altitude error lower half integral signal to form the pitch angle expected signal, and designing the automatic update rule of the corresponding compensation signal includes:

[0031]

[0032]

[0033]

[0034]

[0035]

[0036]

[0037]

[0038]

[0039] θ d =d1s1+w5+w6+w7+w8+d7e h +d8v y +d9s h1 +d 10 s h2 ;

[0040] Among them, w5 is the sliding mode nonlinear compensation signal, w6 is the vertical acceleration compensation signal, w7 is the sliding mode linear compensation signal, w8 is the pitch angle angular velocity compensation signal, d1, d2, d7, d8, d9, d 10 is a constant parameter signal; is the sliding mode nonlinear compensation coefficient; is the vertical acceleration compensation coefficient; is the sliding mode linear compensation coefficient, is the pitch angle angular velocity compensation coefficient; k d3 , k d4 , k d5 , k d6 is a constant parameter used to adjust the automatic update speed of the corresponding compensation coefficient, θ d is the expected signal of the pitch angle.

[0041] In an exemplary embodiment of the present invention, the pitch angular velocity signal is obtained by integrating the pitch angular acceleration signal, and then the pitch angular velocity signal is integrated to obtain the pitch angle signal, and the pitch angle error signal is compared with the pitch angle expected signal; then an integer order approximate differentiator is designed to obtain a pitch angle error integer order approximate differential signal; then a one-tenth order approximate fractional differentiator is designed to obtain a pitch angle fractional order approximate differential signal, and the pitch angle error integer order approximate differential signal is superimposed by the one-tenth order approximate fractional differentiator again to obtain a pitch angle error integer order approximate differential signal. The signal includes:

[0042]

[0043] e1=θ-θ d ;

[0044]

[0045]

[0046]

[0047] where ω z is the pitch angular velocity signal, θ is the pitch angle signal, θ d is the pitch angle expected signal, e1 is the pitch angle error signal, a1 and a2 are constant parameters, s is the differential operator of the transfer function of the integer-order approximate differentiator; e2 is the integer-order approximate differential signal of the pitch angle error, e3 is the fractional-order approximate differential signal of the pitch angle, e d1 It is the integer fractional order mixed approximate differential signal of the pitch angle error.

[0048] In an exemplary embodiment of the present invention, switching integration is performed according to the pitch angle error signal to obtain a pitch angle error upper integral signal and a pitch angle error lower integral signal, which are superimposed to obtain a pitch angle error full integral signal; a pitch angle error inner loop sliding mode signal is formed by superimposing the pitch angle error signal with a vertical velocity signal, a pitch angle error full integral signal, a pitch angle error upper integral signal, a pitch angle error lower integral signal, a vertical acceleration inner loop adaptive signal, a pitch angle acceleration inner loop adaptive signal, a vertical velocity inner loop adaptive signal, and a pitch angle error inner loop adaptive signal; and an adaptive rule for designing an inner loop adaptive coefficient according to the pitch angle error inner loop sliding mode signal includes:

[0049]

[0050]

[0051] s θ =s θ1 +s θ2 ;

[0052]

[0053]

[0054]

[0055]

[0056] s2=f1e1+f2v y +f3s θ +p4+p5+p6+p7+f8s θ1 +f9s θ2 ;

[0057]

[0058]

[0059]

[0060]

[0061] where s θ1 is the integral signal of the pitch angle error, s θ2 is the integral signal under the pitch angle error, s θ is the full integral signal of the pitch angle error; p4 is the vertical acceleration inner loop adaptive signal, p5 is the pitch angle acceleration inner loop adaptive signal, p6 is the vertical velocity inner loop adaptive signal, p7 is the pitch angle error inner loop adaptive signal, s2 is the pitch angle error inner loop sliding mode signal; f1, f2, f3, f8, f9, ε2 are constant parameters; is the vertical acceleration inner loop adaptive coefficient, is the pitch angular acceleration inner loop adaptive coefficient, is the vertical velocity inner loop adaptive coefficient, k is the pitch angle error inner loop adaptive coefficient; f4 , k f5 , k f6 , k f7 It is a constant parameter used to adjust the convergence speed of the inner loop adaptive coefficient.

[0062] In an exemplary embodiment of the present invention, an inner loop sliding mode nonlinear compensation signal, an inner loop vertical acceleration nonlinear compensation signal, an inner loop sliding mode linear compensation signal, an inner loop pitch acceleration compensation signal, an inner loop pitch velocity linear compensation signal, and an inner loop pitch velocity nonlinear compensation signal are designed according to the pitch angle error inner loop sliding mode signal, and an adaptive update rule of the compensation coefficient is designed at the same time, and the pitch angle error signal, the pitch angle error integer fractional order mixed approximate differential signal and the pitch angle error inner loop sliding mode signal are superimposed to form the final height loop control total signal, which includes:

[0063]

[0064]

[0065]

[0066]

[0067]

[0068]

[0069] δ h =g1s2+m1+m2+m3+m4+m5+m6+g 10 e1+g 11 e d1 ;

[0070]

[0071]

[0072]

[0073]

[0074]

[0075]

[0076] Wherein m1 is the inner loop sliding mode nonlinear compensation signal, m2 is the inner loop vertical acceleration nonlinear compensation signal, m3 is the inner loop sliding mode linear compensation signal, m4 is the inner loop pitch angle acceleration compensation signal, m5 is the inner loop pitch angle velocity linear compensation signal, and m6 is the inner loop pitch angle velocity nonlinear compensation signal; is the inner loop sliding mode nonlinear compensation coefficient, is the vertical acceleration nonlinear compensation coefficient of the inner loop, is the inner loop sliding mode linear compensation coefficient, is the pitch acceleration compensation coefficient of the inner loop, is the linear compensation coefficient of the pitch angular velocity in the inner loop, k is the nonlinear compensation coefficient of pitch angular velocity in the inner loop; g3 , k g4 , k g5 , k g6 , k g7 , k g8 is a constant parameter signal, used to control the speed of automatic update of compensation coefficient; g1, g2, g9, g 10 , g 11 is a constant control parameter, δ h The total signal for the final height loop control.

[0077] Beneficial Effects

[0078] The present invention discloses a method for controlling the altitude of a UAV using only a linear angular accelerometer for measurement. The main innovations are as follows: First, the measurement method is simple. Only a linear accelerometer and an angular accelerometer need to be installed to meet the demand for altitude control of the UAV, thereby reducing the economic cost of the overall control scheme. Second, a mixed differential solution technology of an integer order and a fractional order is adopted to obtain a mixed approximate differential of the error, thereby improving the stability of the entire control scheme. Third, a design method of internal and external loop sliding mode and adaptive compensation is adopted. The design of the adaptive rule enables the overall control scheme to automatically compensate for the interference to the control quality caused by insufficient measurement of angles, speeds, accelerations, etc. or low measurement accuracy.

[0079] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] The accompanying drawings herein are incorporated into and constitute a part of the specification, illustrate embodiments consistent with the present invention, and together with the specification are used to explain the principles of the present invention. Obviously, the accompanying drawings described below are only some embodiments of the present invention, and for those of ordinary skill in the art, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0081] Figure 1 The present invention provides a flow chart of a method for controlling the altitude of a UAV using only a linear angular accelerometer for measurement.

[0082] Figure 2 is the altitude curve of the UAV according to the method provided in the embodiment of the present invention (unit: meter);

[0083] Figure 3 is the pitch angle curve of the drone according to the method provided in the embodiment of the present invention (unit: degree);

[0084] Figure 4 is the expected signal curve of the pitch angle of the UAV of the method provided in the embodiment of the present invention (unit: degree);

[0085] Figure 5 is a pitch angular velocity signal curve of the drone according to the method provided in the embodiment of the present invention (unit: radians per second);

[0086] Figure 6 It is a pitch angle acceleration signal curve of the UAV according to the method provided in the embodiment of the present invention (unit: radians per second squared). DETAILED DESCRIPTION

[0087] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as being limited to the examples set forth herein; on the contrary, these embodiments are provided so that the present invention will be more comprehensive and complete, and the concept of the example embodiments will be fully conveyed to those skilled in the art. The described features, structures, or characteristics may be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present invention. However, those skilled in the art will appreciate that the technical solutions of the present invention may be practiced while omitting one or more of the specific details, or other methods, components, devices, steps, etc. may be adopted. In other cases, known technical solutions are not shown or described in detail to avoid blurring out various aspects of the present invention.

[0088] The present invention provides a method for realizing the altitude control of a UAV by measuring the pitch acceleration and vertical acceleration of the UAV. The method is characterized in that the measuring equipment is simple and low-cost, making the whole scheme particularly competitive in the field of low-end UAVs. It adopts switching integral to improve the sensitivity of altitude control, and adopts a combination of integer-order approximate differentiator and one-tenth-order approximate fractional differentiator to obtain the pitch angle error integer-fractional order mixed approximate differential signal, thereby improving the stability margin of the control scheme. At the same time, the altitude loop combined sliding mode and adaptive technology matching solution are adopted to obtain the desired pitch angle signal; the pitch angle error inner loop sliding mode and adaptive technology matching solution are adopted to obtain the final altitude loop control total signal, thereby realizing the tracking control of the UAV to the desired altitude.

[0089] Next, a method for controlling the altitude of a drone using only a linear angular accelerometer for measurement according to the present invention will be further explained and illustrated in conjunction with the accompanying drawings. Figure 1 As shown, the method for controlling the altitude of a UAV using only a linear angular accelerometer for measurement may include the following steps:

[0090] Step S10, installing a linear accelerometer to measure the vertical acceleration of the UAV, installing an angular accelerometer to measure the pitch acceleration signal of the UAV, then integrating the vertical acceleration signal to obtain a vertical velocity signal, and then integrating the vertical velocity signal to obtain a height signal; setting a height expectation signal according to the flight mission requirements, and comparing it with the height signal to obtain a height error signal; and switching the integration to obtain a height error upper integral signal and a height error lower integral signal, and superimposing them to obtain a height error full integral signal.

[0091] Specifically, a linear accelerometer is first installed on the drone to measure the vertical acceleration signal of the drone, denoted as a y .

[0092] Secondly, the vertical acceleration signal is integrated to obtain the vertical velocity signal v y as follows:

[0093] v y =∫a y dt;

[0094] Next, the vertical velocity signal is integrated to obtain the UAV height signal h y as follows:

[0095] h y =∫v y dt;

[0096] Then, according to the needs of the flight mission, set the height expectation signal, denoted as h d , and compared with the UAV height signal, the height error signal is obtained, denoted as e h as follows:

[0097] e h =h y -h d ;

[0098] Furthermore, the pitch angle expected signal is compared with the pitch attitude angle signal to obtain an attitude angle error signal, which is recorded as e1. The comparison method is as follows: e1 = θ - θ d .

[0099] Finally, the upper integral signal of the height error and the lower integral signal of the height error are obtained by switching the integral as follows:

[0100]

[0101]

[0102] The full integral signal of the height error obtained by superposition is as follows:

[0103] s h =sh1 +s h2 ;

[0104] where s h1 is the integrated signal of the height error, s h2 is the integrated signal under height error, s h is the fully integrated signal of the height error.

[0105] Step S20, forming a height loop combined sliding mode signal according to nine signals including height error signal, vertical velocity signal, height error full integral signal, height error upper half integral signal, height error lower half integral signal, vertical acceleration adaptive signal, pitch angle acceleration adaptive signal, height error adaptive signal, and vertical velocity adaptive signal; and designing corresponding vertical acceleration adaptive law, pitch angle acceleration adaptive law, height error adaptive law, and vertical velocity adaptive law.

[0106] Specifically, firstly, the vertical acceleration adaptive signal, the pitch angle acceleration adaptive signal, the height error adaptive signal, and the vertical speed adaptive signal are calculated according to the vertical acceleration signal, the pitch angle acceleration signal, the height error signal, and the vertical speed signal as follows:

[0107]

[0108]

[0109]

[0110]

[0111] in is the vertical acceleration adaptive coefficient, is the pitch acceleration adaptation coefficient, is the height error adaptive coefficient, is the vertical speed adaptive coefficient, the initial value of the above coefficient is selected as 0, and the subsequent solution is as follows. w1 is the vertical acceleration adaptive signal, w2 is the pitch angle acceleration adaptive signal, w3 is the height error adaptive signal, and w4 is the vertical speed adaptive signal.

[0112] Secondly, according to the nine signals of altitude error signal, vertical velocity signal, altitude error full integral signal, altitude error upper half integral signal, altitude error lower half integral signal, vertical acceleration adaptive signal, pitch angle acceleration adaptive signal, altitude error adaptive signal, vertical velocity adaptive signal, altitude loop combined sliding mode signal is as follows:

[0113] s1=c1e h +c2v y +c3sh +w1+w2+w3+w4+c8s h1 +c9s h2 ;

[0114] Among them, c1, c2, c3, c8, and c9 are constant parameters; s1 is the height loop combined sliding mode signal.

[0115] Finally, according to the obtained altitude loop combined sliding mode signal, the corresponding vertical acceleration adaptive law, pitch angle acceleration adaptive law, altitude error adaptive law, and vertical speed adaptive law are designed as follows, so as to solve the vertical acceleration adaptive coefficient, pitch angle acceleration adaptive coefficient, altitude error adaptive coefficient, and vertical speed adaptive coefficient as follows:

[0116]

[0117]

[0118]

[0119]

[0120] Among them, ε1 is a constant parameter, k c4 , k c5 , k c6 , k c7 It is a constant parameter used to adjust the speed of convergence of the corresponding adaptive coefficient.

[0121] Step S30, combining the sliding mode signal of the altitude loop and superimposing the sliding mode nonlinear compensation signal, the sliding mode linear compensation signal, the vertical acceleration compensation signal, the pitch angle angular velocity compensation signal, the altitude error signal, the vertical velocity signal, the altitude error upper half integral signal, and the altitude error lower half integral signal to form a pitch angle expected signal, and designing the automatic updating rule of the corresponding compensation signal.

[0122] Specifically, firstly, the sliding mode nonlinear compensation signal, the sliding mode linear compensation signal, the vertical acceleration compensation signal, and the pitch angle angular velocity compensation signal are designed as follows:

[0123]

[0124]

[0125]

[0126]

[0127] Among them, w5 is the sliding mode nonlinear compensation signal, w6 is the vertical acceleration compensation signal, w7 is the sliding mode linear compensation signal, and w8 is the pitch angle angular velocity compensation signal; is the sliding mode nonlinear compensation coefficient; is the vertical acceleration compensation coefficient; is the sliding mode linear compensation coefficient, is the pitch angle angular velocity compensation coefficient; the initial value of the above coefficient is selected as 0, and the subsequent solution is shown below. d2 is a constant parameter signal, see the case implementation below for details.

[0128] Secondly, the automatic update rule of the corresponding compensation signal is designed according to the height loop combined sliding mode signal as follows:

[0129]

[0130]

[0131]

[0132]

[0133] where k d3 , k d4 , k d5 , k d6 It is a constant parameter used to adjust the automatic update speed of the corresponding compensation coefficient.

[0134] Finally, according to the height loop combined sliding mode signal superimposed sliding mode nonlinear compensation signal, sliding mode linear compensation signal, vertical acceleration compensation signal, pitch angle angular velocity compensation signal, height error signal, vertical velocity signal, height error upper half integral signal, height error lower half integral signal to form the pitch angle expected signal as follows:

[0135] θ d =d1s1+w5+w6+w7+w8+d7e h +d8v y +d9s h1 +d 10 s h2 ;

[0136] Among them, d1, d7, d8, d9, d 10 is a constant parameter signal; θ d is the expected signal of the pitch angle.

[0137] Step S40, integrating the pitch angular acceleration signal to obtain a pitch angular velocity signal, then integrating the pitch angular velocity signal to obtain a pitch angle signal, and comparing the pitch angle signal with the pitch angle expected signal to obtain a pitch angle error signal; then designing an integer-order approximate differentiator to obtain a pitch angle error integer-order approximate differential signal; then designing a one-tenth-order approximate fractional differentiator to obtain a pitch angle fractional-order approximate differential signal, and once again passing through a one-tenth-order approximate fractional differentiator and superimposing the pitch angle error integer-order approximate differential signal, to obtain a pitch angle error integer-fractional mixed approximate differential signal.

[0138] Specifically, firstly, the pitch angular acceleration signal is integrated to obtain the pitch angular velocity signal as follows:

[0139]

[0140] where ω z is the pitch angular velocity signal, and the pitch angle signal θ is obtained by integrating the pitch angular velocity signal as follows:

[0141] θ=∫ω z dt;

[0142] Then the pitch angle signal is compared with the pitch angle expected signal to obtain the pitch angle error signal e1 as follows:

[0143] e1=θ-θ d ;

[0144] Next, the integer-order approximate differentiator is designed as follows:

[0145]

[0146] Where s is the differential operator of the transfer function of the integer-order approximate differentiator; e2 is the integer-order approximate differential signal of the pitch angle error; a1 and a2 are constant parameters, see the case implementation below for details.

[0147] Then, a tenth-order approximate fractional differentiator is designed to obtain the pitch angle fractional-order approximate differential signal e3 as follows:

[0148]

[0149] Finally, the pitch angle fractional order approximate differential signal is passed through a one-tenth order approximate fractional differentiator again and superimposed with the pitch angle error integer order approximate differential signal to obtain the pitch angle error integer fractional order mixed approximate differential signal e d1 as follows:

[0150]

[0151] Step S50, switching integration is performed according to the pitch angle error signal to obtain a pitch angle error upper integral signal and a pitch angle error lower integral signal, and superposition is performed to obtain a pitch angle error full integral signal; a pitch angle error inner loop sliding mode signal is formed by superimposing the pitch angle error signal with the vertical velocity signal, the pitch angle error full integral signal, the pitch angle error upper integral signal, the pitch angle error lower integral signal, the vertical acceleration inner loop adaptive signal, the pitch angle acceleration inner loop adaptive signal, the vertical velocity inner loop adaptive signal and the pitch angle error inner loop adaptive signal; and an adaptive rule of an inner loop adaptive coefficient is designed according to the pitch angle error inner loop sliding mode signal.

[0152] Specifically, first, switching integration is performed according to the pitch angle error signal to obtain a pitch angle error upper integral signal and a pitch angle error lower integral signal as follows:

[0153]

[0154]

[0155] where s θ1 is the integral signal of the pitch angle error, s θ2 is the integrated signal of the pitch angle error.

[0156] Then, the pitch angle error upper integral signal and the pitch angle error lower integral signal are superimposed to obtain the pitch angle error full integral signal as follows:

[0157] s θ =s θ1 +s θ2 ;

[0158] where s θ is the fully integrated signal of the pitch angle error.

[0159] Secondly, the vertical acceleration inner loop adaptive signal, the pitch angle acceleration inner loop adaptive signal, the vertical velocity inner loop adaptive signal and the pitch angle error inner loop adaptive signal are designed as follows:

[0160]

[0161]

[0162]

[0163]

[0164] Among them, p4 is the vertical acceleration inner loop adaptive signal, p5 is the pitch angle acceleration inner loop adaptive signal, p6 is the vertical velocity inner loop adaptive signal, and p7 is the pitch angle error inner loop adaptive signal. is the vertical acceleration inner loop adaptive coefficient, is the pitch angular acceleration inner loop adaptive coefficient, is the vertical velocity inner loop adaptive coefficient, is the pitch angle error inner loop adaptive coefficient; the initial value of the above adaptive coefficient is set to 0, and the detailed solution is shown below.

[0165] Again, the pitch angle error signal is superimposed on the vertical velocity signal, the pitch angle error full integral signal, the pitch angle error upper integral signal, the pitch angle error lower integral signal, the vertical acceleration inner loop adaptive signal, the pitch angle acceleration inner loop adaptive signal, the vertical velocity inner loop adaptive signal and the pitch angle error inner loop adaptive signal to form the pitch angle error inner loop sliding mode signal as follows:

[0166] s2=f1e1+f2v y +f3s θ +p4+p5+p6+p7+f8s θ1 +f9s θ2 ;

[0167] Among them, s2 is the sliding mode signal of the pitch angle error inner loop; f1, f2, f3, f8, f9, and ε2 are constant parameters.

[0168] Finally, the adaptive rule of the inner loop adaptive coefficient is designed according to the pitch angle error inner loop sliding mode signal as follows:

[0169]

[0170]

[0171]

[0172]

[0173] where k f4 , k f5 , k f6 , k f7 is a constant parameter used to adjust the convergence speed of the inner loop adaptive coefficient. ε2 is a constant parameter. For detailed design, see the case implementation below.

[0174] Step S60, according to the pitch angle error inner loop sliding mode signal, design the inner loop sliding mode nonlinear compensation signal, the inner loop vertical acceleration nonlinear compensation signal, the inner loop sliding mode linear compensation signal, the inner loop pitch angle acceleration compensation signal, the inner loop pitch angle velocity linear compensation signal, and the inner loop pitch angle velocity nonlinear compensation signal; at the same time, design the adaptive update law of the compensation coefficient; and superimpose the pitch angle error signal, the pitch angle error integer fractional order mixed approximate differential signal and the pitch angle error inner loop sliding mode signal to form the final height loop control total signal, which is transmitted to the pitch rudder system of the UAV to realize the tracking control of the UAV to the desired height.

[0175] Specifically, firstly, according to the pitch angle error inner loop sliding mode signal, the inner loop sliding mode nonlinear compensation signal, the inner loop vertical acceleration nonlinear compensation signal, the inner loop sliding mode linear compensation signal, the inner loop pitch angle acceleration compensation signal, the inner loop pitch angle velocity linear compensation signal, and the inner loop pitch angle velocity nonlinear compensation signal are designed as follows:

[0176]

[0177]

[0178]

[0179]

[0180]

[0181]

[0182] Wherein m1 is the inner loop sliding mode nonlinear compensation signal, m2 is the inner loop vertical acceleration nonlinear compensation signal, m3 is the inner loop sliding mode linear compensation signal, m4 is the inner loop pitch angle acceleration compensation signal, m5 is the inner loop pitch angle velocity linear compensation signal, and m6 is the inner loop pitch angle velocity nonlinear compensation signal; is the inner loop sliding mode nonlinear compensation coefficient, is the vertical acceleration nonlinear compensation coefficient of the inner loop, is the inner loop sliding mode linear compensation coefficient, is the pitch acceleration compensation coefficient of the inner loop, is the linear compensation coefficient of the pitch angular velocity in the inner loop, is the nonlinear compensation coefficient of the pitch angular velocity in the inner loop; g2 and g9 are constant parameters, see the case implementation below for details.

[0183] Secondly, the adaptive update rule of the compensation coefficient is designed according to the sliding mode signal of the pitch angle error inner loop as follows:

[0184]

[0185]

[0186]

[0187]

[0188]

[0189]

[0190] where k g3 , k g4 , k g5 , k g6 , k g7 , k g8 It is a constant parameter signal, which is used to control the speed of automatic updating of the compensation coefficient. For detailed design, please refer to the case implementation below.

[0191] Finally, the pitch angle error signal, the pitch angle error integer fractional order mixed approximate differential signal and the pitch angle error inner loop sliding mode signal are superimposed to form the final height loop control total signal as follows:

[0192] δ h =g1s2+m1+m2+m3+m4+m5+m6+g 10 e1+g 11 e d1 ;

[0193] Among them, g1, g 10 , g 11 is a constant control parameter, δ h The final height loop control signal is sent to the pitch and rudder system of the UAV to achieve tracking control of the UAV to the desired height.

[0194] Case implementation and computer simulation results analysis

[0195] In step S10, the height expected signal h is set d =300 meters.

[0196] In step S20, select k c4 =0.002, k c5 =0.0015, k c6 =0.0024, k c7 =0.0018, ε1=0.45. c1=0.01, c2=0.05, c3=0.009, c8=0.014, c9=0.002

[0197] In step S30, k is setd3 =0.0013, k d4 =0.0011, k d5 =0.0015, k d6 =0.0009. d1=0.4, d2=0.15, d7=0.01, d8=0.02, d9=0.005, d 10 =0.001.

[0198] In step S40, a1=0.0025 and a2=0.3 are set.

[0199] In step S50, select k f4 =0.001, k f5 =0.0012, k f6 =0.0009, k f7 =0.0013, f1=2, f2=0.08, f3=0.4, f8=0.5, f9=0.1, ε2=0.6.

[0200] In step S60, select k g3 =0.01, k g4 =0.008, k g5 =0.013, k g6 =0.018, k g7 =0.014, k g8 =0.016. g1=1.4, g2=0.3, g9=0.6, g 10 =1.8, g 11 =0.6.

[0201] The final drone altitude signal is as follows: Figure 2 As shown, the pitch angle signal of the drone is Figure 3 As shown, the expected signal of the UAV pitch angle is as follows Figure 4 As shown, the pitch angular velocity signal of the UAV is as follows Figure 5 As shown, the pitch angle acceleration signal of the drone is as follows Figure 6 As shown. It can be seen that although the UAV altitude fluctuates, it can quickly climb to a height of 300 meters within 10 seconds, and the stability accuracy is relatively high, so it can meet the general control requirements of high-altitude flight stability. At the same time, the pitch angle, pitch angular velocity, and pitch angular acceleration curves can show that the entire climbing process control system is relatively stable, indicating that the method provided by the present invention is feasible and effective. At the same time, because the measuring components used in the present invention are relatively simple and cheap, it has high market competitiveness.

Claims

1. A method for controlling the altitude of an unmanned aerial vehicle using only a linear angular accelerometer, characterized in that: A linear accelerometer is installed to measure the vertical acceleration of the UAV, and an angular accelerometer is installed to measure the pitch acceleration signal of the UAV. Then, the vertical acceleration signal is integrated to obtain the vertical velocity signal, and then the vertical velocity signal is integrated to obtain the altitude signal; the altitude expectation signal is set according to the flight mission requirements, and compared with the altitude signal to obtain the altitude error signal; and the altitude error upper integral signal and the altitude error lower integral signal are obtained by switching the integral, and the altitude error full integral signal is superimposed; the altitude error signal, the vertical velocity signal, the altitude error full integral signal, the altitude error upper half integral signal, the altitude error lower half integral signal, the vertical acceleration adaptive The nine signals of the altitude loop combined sliding mode signal, namely, the pitch angle acceleration adaptive signal, the altitude error adaptive signal, and the vertical speed adaptive signal, are designed; and the corresponding vertical acceleration adaptive law, the pitch angle acceleration adaptive law, the altitude error adaptive law, and the vertical speed adaptive law are designed; and the altitude loop combined sliding mode signal is superimposed with the sliding mode nonlinear compensation signal, the sliding mode linear compensation signal, the vertical acceleration compensation signal, the pitch angle angular velocity compensation signal, the altitude error signal, the vertical speed signal, the altitude error upper half integral signal, and the altitude error lower half integral signal to form the pitch angle expected signal, and the corresponding compensation signal automatic update law is designed as follows: v y =∫a y dt; h y =∫v y dt; e h =h y -h d ; s h =s h1 +s h2 ; <h2 style=";text-align:left;direction:ltr">s1 = c1e<h2 style=";text-align:left;direction:ltr"> h <h2 style=";text-align:left;direction:ltr"> +c2v<h2 style=";text-align:left;direction:ltr"> y <h2 style=";text-align:left;direction:ltr"> +c3s<h2 style=";text-align:left;direction:ltr"> h <h2 style=";text-align:left;direction:ltr"> +w1+w2+w3+w4+c8s<h2 style=";text-align:left;direction:ltr"> h1 <h2 style=";text-align:left;direction:ltr"> +c9s<h2 style=";text-align:left;direction:ltr"> h2 <h2 style=";text-align:left;direction:ltr"> ; <h2 style=";text-align:left;direction:ltr">θ<h2 style=";text-align:left;direction:ltr"> d <h2 style=";text-align:left;direction:ltr"> = d1s1+w5+w6+w7+w8+d7e<h2 style=";text-align:left;direction:ltr"> h <h2 style=";text-align:left;direction:ltr"> +d8v<h2 style=";text-align:left;direction:ltr"> y <h2 style=";text-align:left;direction:ltr"> +d9s<h2 style=";text-align:left;direction:ltr"> h1 <h2 style=";text-align:left;direction:ltr"> +d<h2 style=";text-align:left;direction:ltr"> 10 <h2 style=";text-align:left;direction:ltr"> s<h2 style=";text-align:left;direction:ltr"> h2 <h2 style=";text-align:left;direction:ltr"> ; where a y is the vertical acceleration signal, v y is the vertical speed signal, is the pitch angle acceleration signal; h d To set the altitude expectation signal according to the flight mission requirements; h y is the UAV height signal, e h is the UAV height error signal; s h1 is the integrated signal of the height error, s h2 is the integrated signal under height error, s h is the full integral signal of the height error; w1 is the vertical acceleration adaptive signal, w2 is the pitch angle acceleration adaptive signal, w3 is the height error adaptive signal, w4 is the vertical velocity adaptive signal, s1 is the height loop combined sliding mode signal; among them, c1, c2, c3, c8, c9, ε1 are constant parameters; is the vertical acceleration adaptive coefficient, is the pitch acceleration adaptation coefficient, is the height error adaptive coefficient, is the vertical speed adaptation coefficient; k c4 , k c5 , k c6 , k c7 is a constant parameter used to adjust the speed of convergence of the corresponding adaptive coefficient; w5 is the sliding mode nonlinear compensation signal, w6 is the vertical acceleration compensation signal, w7 is the sliding mode linear compensation signal, w8 is the pitch angle angular velocity compensation signal, d1, d2, d7, d8, d9, d 10 is a constant parameter signal; is the sliding mode nonlinear compensation coefficient; is the vertical acceleration compensation coefficient; is the sliding mode linear compensation coefficient, is the pitch angle angular velocity compensation coefficient; k d3 , k d4 , k d5 , k d6 is a constant parameter used to adjust the automatic update speed of the corresponding compensation coefficient, θ d is the expected signal of the pitch angle.

2. The method for controlling the altitude of an unmanned aerial vehicle using only a linear angular accelerometer according to claim 1, characterized in that: The pitch angle acceleration signal is integrated to obtain the pitch angle velocity signal, and then the pitch angle signal is integrated to obtain the pitch angle signal, and the pitch angle error signal is compared with the pitch angle expected signal; then an integer order approximate differentiator is designed to obtain the integer order approximate differential signal of the pitch angle error; a one-tenth order approximate fractional differentiator is designed to obtain the pitch angle fractional order approximate differential signal, and the one-tenth order approximate fractional differentiator is used again to superimpose the pitch angle error integer order approximate differential signal to obtain the pitch angle error integer fractional order mixed approximate differential signal; and the pitch angle error upper integral signal and the pitch angle error lower integral signal are obtained by switching the pitch angle error signal to obtain the pitch angle error full integral signal; the pitch angle error signal is superimposed with the vertical velocity signal, the pitch angle error full integral signal, the pitch angle error upper integral signal, the pitch angle error lower integral signal and the vertical acceleration inner loop adaptive The pitch angle error inner loop sliding mode signal is composed of the pitch angle acceleration inner loop adaptive signal, the vertical velocity inner loop adaptive signal and the pitch angle error inner loop adaptive signal; and the adaptive law of the inner loop adaptive coefficient is designed according to the pitch angle error inner loop sliding mode signal; and the inner loop sliding mode nonlinear compensation signal, the inner loop vertical acceleration nonlinear compensation signal, the inner loop sliding mode linear compensation signal, the inner loop pitch angle acceleration compensation signal, the inner loop pitch angle velocity linear compensation signal, and the inner loop pitch angle velocity nonlinear compensation signal are designed according to the pitch angle error inner loop sliding mode signal, and the adaptive update law of the compensation coefficient is designed at the same time, and the pitch angle error signal, the pitch angle error integer fractional order mixed approximate differential signal and the pitch angle error inner loop sliding mode signal are superimposed to form the final height loop control total signal, which is transmitted to the pitch rudder system of the UAV to realize the tracking control of the UAV to the desired height as follows: e1=θ-θ d ; s θ =s θ1 +s θ2 ; <h2 style=";text-align:left;direction:ltr">s2 = f1e1 + f2v<h2 style=";text-align:left;direction:ltr"> y <h2 style=";text-align:left;direction:ltr"> +f3s<h2 style=";text-align:left;direction:ltr"> θ <h2 style=";text-align:left;direction:ltr"> +p4+p5+p6+p7+f8s<h2 style=";text-align:left;direction:ltr"> θ1 <h2 style=";text-align:left;direction:ltr"> +f9s<h2 style=";text-align:left;direction:ltr"> θ2 <h2 style=";text-align:left;direction:ltr"> ; δ h =g1s2+m1+m2+m3+m4+m5+m6+g 10 e1+g 11 and d1 ; where ω z is the pitch angular velocity signal, θ is the pitch angle signal, θ d is the desired pitch angle signal, e1 is the pitch angle error signal, s is the differential operator of the transfer function of the integer-order approximate differentiator; a1 and a2 are the constant parameters of the differentiator, e2 is the integer-order approximate differential signal of the pitch angle error, e3 is the fractional-order approximate differential signal of the pitch angle, and e d1 is the integer fractional order mixed approximate differential signal of the pitch angle error; s θ1 is the integral signal of the pitch angle error, s θ2 is the integral signal under the pitch angle error, s θ is the full integral signal of the pitch angle error; p4 is the vertical acceleration inner loop adaptive signal, p5 is the pitch angle acceleration inner loop adaptive signal, p6 is the vertical velocity inner loop adaptive signal, p7 is the pitch angle error inner loop adaptive signal, s2 is the pitch angle error inner loop sliding mode signal; f1, f2, f3, f8, f9, ε2 are constant parameters; is the vertical acceleration inner loop adaptive coefficient, is the pitch angular acceleration inner loop adaptive coefficient, is the vertical velocity inner loop adaptive coefficient, k is the pitch angle error inner loop adaptive coefficient; f4 , k f5 , k f6 , k f7 is a constant parameter used to adjust the convergence speed of the inner loop adaptive coefficient; m1 is the inner loop sliding mode nonlinear compensation signal, m2 is the inner loop vertical acceleration nonlinear compensation signal, m3 is the inner loop sliding mode linear compensation signal, m4 is the inner loop pitch angle acceleration compensation signal, m5 is the inner loop pitch angle velocity linear compensation signal, and m6 is the inner loop pitch angle velocity nonlinear compensation signal; is the nonlinear compensation coefficient of the inner loop sliding mode, is the vertical acceleration nonlinear compensation coefficient of the inner loop, is the inner loop sliding mode linear compensation coefficient, is the pitch acceleration compensation coefficient of the inner loop, is the linear compensation coefficient of the pitch angular velocity in the inner loop, k is the nonlinear compensation coefficient of pitch angular velocity in the inner loop; g3 , k g4 , k g5 , k g6 , k g7 , k g8 is a constant parameter signal, used to control the speed of automatic update of compensation coefficient; g1, g2, g9, g 10 , g 11 is a constant control parameter, δ h The total signal for the final height loop control.

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