CN110531776B - Four-rotor aircraft position control method and system based on active disturbance rejection control technology - Google Patents
Four-rotor aircraft position control method and system based on active disturbance rejection control technology Download PDFInfo
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Abstract
The invention discloses a method and a system for controlling the position of a four-rotor aircraft based on an active disturbance rejection control technology, which can effectively improve the robustness and tracking precision of the position control of the four-rotor aircraft. The method designs an active disturbance rejection controller aiming at a simplified position control model; in the active disturbance rejection controller, a tracking differentiator is adopted to send a position signal fed back by a controlled object to an observer after smooth noise reduction; the observer adopts a three-order extended state observer, and the three-order extended state observer inputs the output control quantity after compensation of motor response delay, so that each order state of the position control model and internal and external disturbance acting on the model can be accurately observed and estimated in real time; and subtracting the estimated quantity of the position and the speed output by the observer from the given quantity, calculating by a nonlinear control rate to obtain a primary control quantity, and compensating on the basis of the primary control quantity by using the disturbance estimated quantity obtained by the observer to obtain the actual output control quantity of the controller.
Description
Technical Field
The invention belongs to the technical field of control of four-rotor aircrafts, and relates to a four-rotor aircraft position control method and system based on an active disturbance rejection control technology.
Background
The four-rotor wing is an aircraft capable of taking off and landing Vertically (VTOL), belongs to a non-coaxial disc aircraft in the overall layout, has a more compact structure and generates more lift force compared with the conventional rotor wing aircraft, and two pairs of rotor wings with opposite rotation directions can mutually offset the reaction torque, so that the reaction torque paddle is not needed. Compared with a fixed-wing aircraft, the quad-rotor unmanned aerial vehicle can take off and land vertically and hover freely, has strong maneuvering capability and is particularly suitable for executing tasks under complex conditions. With the wide application of the quad-rotor unmanned aerial vehicle in the civil and military fields in recent years, the productivity level is improved, and meanwhile, the fighting mode of modern war is changed.
A quad-rotor aircraft has three translational degrees of freedom and three rotational degrees of freedom, for a total of six degrees of freedom, but only four control inputs. A quad-rotor aircraft is therefore a typical under-actuated system. Meanwhile, the four-rotor aircraft is a static unstable system with characteristics of strong coupling, nonlinearity, multivariable and the like, and can be interfered by external environments such as various physical effects and wind disturbance in low-altitude flight, so that the control effect is influenced and even instability is caused, and therefore a stable and reliable position control algorithm needs to be designed to ensure a series of requirements such as stability and precision of control under the condition of disturbance outside.
The active disturbance rejection control technology is developed by Korean Jingqing researchers and leading research groups thereof in the institute of mathematics and system science of Chinese academy of sciences, inherits and develops the concept of classical control, and absorbs the thought of modern control theory. The active disturbance rejection means: the unmodeled dynamic disturbance and the unknown external disturbance are both attributed to the unknown disturbance of the object, the input and output data are used for estimation and compensation, thereby realizing the dynamic feedback linearization of the dynamic system, and then the nonlinear configuration is used for forming a nonlinear feedback control law to improve the control performance of the closed-loop system.
Active disturbance rejection control techniques have been applied by relevant scholars to the relevant control of quad-rotor aircraft, but are commonly used for attitude control. For position control, the noise of position feedback signals is high, and the effect is not ideal even if an active disturbance rejection control technology is added.
Disclosure of Invention
In view of the above, the invention provides a method and a system for controlling a position of a quad-rotor aircraft based on an active disturbance rejection control technology, aiming at the defect of poor disturbance rejection capability in the position control of the existing quad-rotor unmanned aerial vehicle, and the method and the system can effectively improve the disturbance rejection capability and the tracking precision of the quad-rotor aircraft, thereby improving the robustness of the position control.
In order to solve the technical problem, the invention is realized as follows:
a four-rotor aircraft position control method based on active disturbance rejection is disclosed, wherein an active disturbance rejection controller is designed aiming at a position control model of a four-rotor aircraft; in the designed active disturbance rejection controller, a position signal y fed back by a controlled object is subjected to smooth noise reduction processing by a tracking differentiator and then is sent to an observer; the observer adopts a three-order extended state observer, and observes and estimates each order state of the position control model and internal and external disturbance acting on the model by utilizing position information after smooth noise reduction and control quantity u (t-tau) added with motor response delay tau; subtracting the estimation quantity of the position and the speed output by the observer from a given quantity, and calculating the difference value through a nonlinear control rate to obtain a primary control quantity u0Finally, the disturbance estimator obtained by the third-order extended state observer is used for estimating the initial control quantity u0Then, the final output controlled variable u (t) is obtained after compensation.
Preferably, a PID controller is further established in parallel with the active disturbance rejection controller; adopting a PID controller to control a manual takeoff process, starting to simultaneously operate the PID controller and an active disturbance rejection controller after the aircraft enters an automatic mode and is stably suspended, and adopting the output quantity of the PID controller as an actual output control quantity at the moment; and judging whether the difference between the control quantities calculated by the two controllers is within a certain range, and if the output quantity of the active disturbance rejection controller is not dispersed and the difference between the control quantity values calculated by the two controllers is within a certain range, switching to active disturbance rejection controller control.
Preferably, the tracking differentiator is constructed by adopting a steepest synthesis function fhan; in the steepest synthesis function, the fast factor r is 104Magnitude data, filter factor h1By using 10-2Magnitude data.
The invention also provides a four-rotor aircraft position control system based on active disturbance rejection, which comprises an active disturbance rejection controller; the active disturbance rejection controller comprises a tracking differentiator, an observer, a nonlinear control rate calculation module, a time delay module and a control quantity compensation module;
a tracking differentiator for smoothing and denoising the position signal y fed back by the controlled object to obtain a smoothed position signal v1Feeding into an observer;
the time delay module is used for adding the output control quantity u (t) into the motor response time delay tau to form u (t-tau) which is input into the observer;
the observer is a three-order extended state observer for utilizing the smoothed position signal v1And adding a time delay control quantity u (t-tau), observing and estimating each stage state of the position control model and internal and external disturbance acting on the model to obtain a position estimation quantity z1Velocity estimator z2And a disturbance estimator;
a non-linear control rate calculation module for estimating the position z1And velocity estimator z2Making difference with given quantity, calculating nonlinear control rate to obtain initial control quantity u0；
A control quantity compensation module for utilizing the disturbance estimation quantity obtained by the third-order extended state observer to obtain the preliminary control quantity u0And then compensating to obtain the final control quantity output u (t).
Preferably, the system further comprises a PID controller, a switching control module and a switch;
the switching control module is used for controlling the switching switch to enable the PID controller to work in a manual takeoff stage; after the aircraft enters an automatic mode and is stably suspended, the PID controller and the active disturbance rejection controller work simultaneously by controlling the selector switch, but the output quantity of the PID controller is still adopted as the actual output control quantity at the moment; and judging whether the difference between the control quantities calculated by the two controllers is within a certain range, and if the output quantity of the active disturbance rejection controller is not dispersed and the difference between the control quantity values calculated by the two controllers is within a certain range, switching to the active disturbance rejection controller to work by controlling a selector switch.
Preferably, the tracking differentiator is constructed by adopting a steepest synthesis function fhan; in the steepest synthesis function, the fast factor r is 104Magnitude data, filter factor h1By using 10-2Magnitude data.
Compared with the prior art, the invention has the advantages and positive effects that:
(1) different from the use of the tracking differentiator in the common auto-disturbance-rejection controller, the tracking differentiator is used for processing the position feedback signal with larger noise, so that the observation and control of a subsequent observer are facilitated, and an expected effect is achieved.
(2) In actual flight, although the use of the auto-disturbance-rejection attitude controller can largely improve the robustness of the overall flight, the robustness to the position channel is not sufficient. The invention adds the uncertain part of the real-time estimation position model of the extended state observer and the sum of internal disturbance and external disturbance into the position control loop, further considers the response delay time of the system in the design of ESO, leads the obtained estimated value to be more accurate, and finally compensates the estimated value on the output control quantity, thereby improving the robustness of position control.
(3) For fast factor r and filter factor h in active disturbance rejection controller1The value range is limited, the parameter selection is to meet the minimum delay as far as possible, the filtering requirement can be properly reduced, and the filter can be used as long as steps or peak signals with extremely large amplitude do not appear. This is done to ensure that the addition of a differentiator does not cause excessive hysteresis in the overall control process, and to avoid oscillations or even instability of the control system.
(4) The preferred embodiment of the invention adopts a scheme of an active disturbance rejection controller and a PID controller, the two controllers are used in stages, the PID control scheme is adopted in the takeoff stage, the problem that an observer is not easy to converge in the takeoff stage is solved, and the active disturbance rejection control scheme is adopted in the normal flight stage, so that the disturbance rejection capability and the tracking precision of the flight of the aircraft are improved. And by designing a reasonable switching control strategy, the stable transition of the switching process of the PID controller to the active disturbance rejection controller is ensured.
Drawings
FIG. 1 is a composite quad-rotor aircraft position control model based on active disturbance rejection + PID in an embodiment of the invention;
FIG. 2 is a block diagram of the position active disturbance rejection control architecture of the present invention;
FIG. 3 is a block diagram of a prior art position active disturbance rejection control architecture;
fig. 4 is a schematic diagram of a composite quad-rotor aircraft position control system based on active disturbance rejection + PID in an embodiment of the present invention.
FIG. 5 is a graph of a single channel tracking sinusoid under noise-free conditions;
FIG. 6 is a graph of a single channel tracking sinusoidal signal under certain noise conditions;
FIG. 7 is a diagram showing the output of the disturbance variable (roll axis) increased under the actual fixed position in flight;
FIG. 8 is a view showing an output condition (pitch axis) of an increased disturbance control amount in the case of an actual in-flight position fix point;
FIG. 9 shows the situation (in x and y axes) that the position of the composite controller is adopted to track the circular track in the actual flight attitude control;
fig. 10 shows the situation that the actual in-flight attitude control adopts the position of the composite controller to track the circular track.
Detailed Description
The invention provides a four-rotor aircraft position control scheme based on an active disturbance rejection control technology, which is designed according to the following design concept:
because the simplified dynamics model of the four-rotor unmanned aerial vehicle position channel is the simplest second-order model, a single-ring position control model is designed to control the position of the four-rotor unmanned aerial vehicle in order to control and adjust parameters conveniently. The position control model is constructed by adopting an active disturbance rejection controller.
For the design of the active disturbance rejection controller, firstly, a tracking differentiator is utilized to carry out smooth noise reduction processing on a position signal y with larger noise fed back by a controlled object, and then the position signal y is sent to an observer; then designing an extended state observer to carry out real-time compensation on the motor response delay tau by addingObserving and estimating the state of the position control model and internal and external disturbance acting on the model; calculating the difference between the estimated position and speed output by the observer and the given value through a nonlinear control rate to obtain a primary control quantity u0(ii) a Finally, a disturbance estimator obtained by utilizing a third-order extended state observer is used for estimating the initial control quantity u0And on the basis, compensating to obtain final output control quantity u (t), thereby compensating the estimated model uncertain part and the internal and external disturbance part borne by the system on the output control quantity to realize excellent control on the position channel.
It can be seen that the present invention has two distinct points:
one is to consider that when the position control tracks a given track, the given track signal is continuous, smooth and noiseless, so that the given signal does not need to be subjected to transient processing. In contrast, since the position feedback information adopted by the four-rotor aircraft is provided by the optical capturing system, the sending and receiving frequency of the position feedback information is relatively low, so that the position information received by the actual aircraft is high in precision but high in noise, and the speed information is higher in noise and cannot be used for control at all if the speed information is obtained by differentiating the position information directly. Therefore, the present invention uses a tracking differentiator to process the feedback position information to obtain a smoother position and velocity information for control. The tracking differentiator is different from the conventional tracking differentiator in use, does not smooth a given position and speed, and is used for processing a position feedback signal with high noise so as to be conveniently sent to an observer for observation. But at the same time it is noted that: the tracking differentiator can naturally filter a certain noise signal to obtain a smoother tracking result, but the smoother tracking means that the time lag of the signal is larger, which directly causes the lag of the whole control process, and is very disadvantageous to a control system, so that the stability margin of a closed-loop control system is reduced, and finally the oscillation and even instability of the control system are caused. Therefore, the selection of the tracking differentiator parameter is crucial, and the fast factor r and the filtering factor h are specifically referred to as the following1The description of (1).
Secondly, the invention improves the control quantity u (t) acting on the third-order extended state observer, and adds the time delay between the generation of the representative control quantity and the feedback, thereby accurately estimating the disturbance of the system in real time and compensating the disturbance.
The above-mentioned active disturbance rejection controller is mainly directed to the control of the automatic flight phase, since the manual flight phase does not involve too much position control, whereas the position controller plays a very important role in the case of automatic flight. The preferred embodiment of the invention described below also adds a PID controller, and the PID controller and the active disturbance rejection controller are used in stages, and the smooth transition of the switching process of switching the PID controller to the active disturbance rejection controller is ensured by designing the switching control strategy.
The invention is described in detail below by way of example with reference to the accompanying drawings.
Fig. 1 is a position control model of a composite quad-rotor aircraft based on active disturbance rejection plus PID in an embodiment of the present invention, which includes an active disturbance rejection controller and a PID controller that are arranged in parallel, and the two controllers are switched by using a switch.
Fig. 2 is a block diagram of the active disturbance rejection controller according to the present invention. Compared with the existing active disturbance rejection controller shown in fig. 3, a time delay link is added, a tracking differentiator on an input position is removed, and a tracking differentiator between the feedback quantity y and the ESO is added.
The following describes the design and workflow of the present invention.
Firstly, a four-rotor aircraft position dynamics model is established.
For the convenience of the following discussion, the model is simplified to some extent, and the simplified linearized model is as follows:
wherein the position y ═ Px、Py、Pz}，Px、Py、PzRespectively represent three-dimensional coordinates of the four-rotor aircraft in three directions of an inertia system xyz,
divided into acceleration in x, y and z directions, u ═ ux uy uz]TThe virtual control quantity corresponding to the three directions of x, y and z is represented, and the specific expression is shown as the following formula:
the psi, the theta and the phi respectively represent the yaw, pitch and roll angles of the four-rotor aircraft under an inertial system, the U is the lift force generated by the four-rotor aircraft in the Z direction of a body coordinate system, the g is the gravity acceleration, and the m is the mass of the four-rotor aircraft.
Under such conditions, the control model for each channel of position can be expressed as follows:
where ξ, v, u represent the position, speed and acceleration of the corresponding channel, respectively, f (ξ, v, w (t), t) represents the uncertain part of the system model and the sum of internal and external disturbances suffered by the system, bu (t- τ) represents the part of the output control quantity considering the delay of the actuator and the like acting on the system model, where τ is the system response delay time.
And secondly, designing a tracking differentiator of the active disturbance rejection control technology according to the established model. Different from the use of the conventional tracking differentiator, the tracking differentiator is mainly used for processing a position feedback signal with high noise so as to be convenient for being sent to an observer for observation.
The tracking differentiator is in the form of:
fh＝fhan(y1(k)-y(k),y2(k),r,h1)
y1(k+1)＝y1(k)+h2y2(k)
y2(k+1)＝y2(k)+h2fh
wherein, the input signal y (k) is the obtained global position information, and the output signal y1(k) For smoothed tracking position information, y2(k) For tracking velocity information, y1(k) The derivative of (c). fhan is the fastest synthesis function, and its expression is described in document 1 (active disturbance rejection control technology, han jingqing, front porch science 2007 & 1, general phase 1). r, h1Respectively representing fast and filter factors, h2Representing the step factor. The parameters are selected to meet the requirement of minimum delay as much as possible, the filtering requirement can be properly reduced, and the method can be used as long as no step or peak signal with extremely large amplitude appears, so that the fast factor r of the invention adopts 104Magnitude data, filter factor h1By using 10-2Magnitude data.
And thirdly, designing an Extended State Observer (ESO) according to a four-rotor aircraft position control model, and considering the response delay time of the added system, so as to accurately estimate the disturbance of the system in real time and compensate.
The above proposes a four-rotor position control model, which is a second order model of position control. And designing a corresponding three-order extended state observer for observing each order state of the system according to the model, estimating internal and external disturbances borne by the actual system, and compensating in real time to enhance the robustness of the system.
The specifically designed extended state observer is shown as follows:
e＝z1-y1
wherein y here1Representing tracking position information, z, obtained by smoothing external position information received by the system by a tracking differentiator1、z2And respectively representing the position and speed state quantities of the system, wherein the state quantities are one and two of three estimated values of the extended state observer, and subtracting a given position and a given speed after output to obtain a difference value which is used as the input of the nonlinear control rate model. z is a radical of3And representing the dynamic uncertainty and the internal and external disturbances of the system model for the extended state, wherein the dynamic uncertainty and the external disturbances are three estimated values of the extended state observer, and the three estimated values are multiplied by 1/b and then are used for compensating the three estimated values to an output control quantity u (t). bu represents the control quantity acting on the model, b is the estimated value of the control quantity amplification factor in the system model, u is the control quantity output by the control method, and tau represents the acting time delay of the control quantity, and the same needs to be considered and compensated; beta is a01、β02、β03Representing observations required for estimating respective quantities of stateThe gain of the device is related to the sampling step size of the system.
Compared with attitude control, the simplified model of position control is much simpler, firstly, the simplified model has no unknown system dynamics, and secondly, the value of b is directly taken as a unit value 1 without being analyzed and solved. This greatly reduces the workload of simulation and experiment.
Fourthly, obtaining position and speed state quantity z according to the obtained four-rotor attitude control model and the observer1,z2According to a set value r1,r2The difference can be made to obtain the position error e1And the differential e of the error2I.e. the speed error.
e1＝r1-z1
e2＝r2-z2
Fifthly, calculating the position and speed error e1、e2Calculating to obtain a preliminary control quantity u through a nonlinear control rate0。
For non-linear control rates, the present invention takes the form of:
u0＝αarctan(ke1+le2)+βarctan(le2)
wherein, alpha, beta, k and l are adjustable parameters of the controller. The controller is still a PD controller in nature, and only adds a nonlinear function to enable the controller to have some excellent nonlinear characteristics, so that the defects of a single-loop controller are overcome to a certain extent.
Sixthly, according to the basic principle of active disturbance rejection control, the system control rate after internal and external disturbance compensation is obtained as shown in the following formula:
wherein,
the method is a part for compensating the total disturbance value estimated by the third-order extended state observer into the control quantity. b is the control quantity in the system modelThe estimated value of the magnification, u, is the actual output value of the present control scheme.
In summary, according to the scheme, the control rate of the simplified model based on the position control is obtained for the model, but the control rate is obtained only by the virtual control quantity, and the actual angle control quantity is obtained only by resolving the control quantity by one time, and a specific resolving formula is shown as the following formula.
Wherein U is1Representing the resultant external force experienced by the four-rotor aircraft in the inertial system,. psid、θd、
Respectively representing the given angles of yaw, pitch and roll of the aircraft in the inertial system.
When the control system is used, aiming at the control model shown in the figure 1, a reasonably designed controller switching strategy can realize the stable transition between the PID controller adopted for manual flight and the active disturbance rejection controller adopted for automatic flight. The basic idea of the switching control strategy is as follows: after the PID controller is manually taken off and enters an automatic mode to be suspended stably basically, the PID controller and the active disturbance rejection controller are started to operate simultaneously, but the output quantity of the PID controller is still adopted as the actual output control quantity at the moment; at the moment, whether the difference between the calculated control quantities is within a certain range is judged, if the output quantity of the active disturbance rejection controller is not dispersed and the difference between the numerical values of the control quantities calculated by the two controllers is within a certain range, the controller is switched to the active disturbance rejection controller to work once the controller is switched, and the controller is not subjected to large fluctuation of control quantity output theoretically; if the auto-disturbance rejection controller diverges or the difference between the two control quantities is large, the switching cannot be carried out until the switching condition is met.
Based on the above method process, the invention also provides a four-rotor aircraft position control system based on the active disturbance rejection control technology, as shown in fig. 1, which comprises an active disturbance rejection controller, a PID controller, a switching control module and a switch.
The switching control module enables the PID controller to work by controlling the switching switch in a manual takeoff stage; after the aircraft enters an automatic mode and is stably suspended, the PID controller and the active disturbance rejection controller work simultaneously by controlling the selector switch, but the output quantity of the PID controller is still adopted as the actual output control quantity at the moment; and judging whether the difference between the control quantities calculated by the two controllers is within a set range, and if the output quantity of the active disturbance rejection controller is not dispersed and the difference between the control quantity values calculated by the two controllers is within the set range, switching to the active disturbance rejection controller to work by controlling a selector switch.
As shown in fig. 4, the active disturbance rejection controller includes a tracking differentiator, an observer, a nonlinear control rate calculation module, a time delay module, and a control amount compensation module.
A tracking differentiator for smoothing and denoising the position signal y fed back by the controlled object to obtain a smoothed position signal v1Feeding into an observer;
the time delay module is used for adding the output control quantity u (t) into the motor response time delay tau to form u (t-tau) which is input into the observer;
the observer is a three-order extended state observer for utilizing the smoothed position signal v1And adding a time delay control quantity u (t-tau), observing and estimating each stage state of the position control model and internal and external disturbance acting on the model to obtain a position estimation quantity z1Velocity estimator z2And a disturbance estimator;
a non-linear control rate calculation module for estimating the position z1And velocity estimator z2Making difference with given quantity, calculating by nonlinear control rateObtaining a preliminary control quantity u0；
A control quantity compensation module for utilizing the disturbance estimation quantity obtained by the third-order extended state observer to control the initial control quantity u0And then compensating to obtain the final control quantity output u (t).
Based on the above theoretical design of the position active disturbance rejection controller, simulation analysis is performed below to preliminarily verify the rationality and feasibility of the designed controller. And (4) not considering the final calculation of the control quantity, because each channel of the simplified model has no coupling effect and the model is the same, only one channel is subjected to simulation analysis.
As shown in FIG. 5, the graph shows the tracking condition of the control system tracking a sinusoidal signal with amplitude of 1m and angular frequency of 0.3rad/s under the noiseless condition; FIG. 6 is a trace curve for the same sinusoidal signal with the addition of process noise with a mean of 0, a variance of 0.001 and observed noise with a mean of zero and a variance of 0.001.
The controller has high tracking precision under the condition of no noise, no obvious time delay and good overall tracking effect; even if certain random noise is added, the overall control effect of the controller is not influenced, particularly, certain observation noise is added to simulate the position feedback quantity obtained by an actual system to obtain the control effect of the upper graph, and the robustness of the designed position disturbance rejection controller is further proved.
In order to further verify the effectiveness of the active disturbance rejection plus PID-based compound control technology four-rotor position controller, the invention utilizes the QAV-250 frame-based four-rotor aircraft to carry out actual flight experiments.
In the experiment, the four-rotor aircraft is developed mainly based on ANO-Pioneer open source flight control and is built by utilizing a QAV-250 frame. The flight control is based on an STM32F407VG main controller, the highest main frequency can reach 168MHz, an ICM20602 module is adopted as an inertia measurement module, an EMAX MT2204 KV2300 direct-current brushless motor, an EMAX sink 12A electronic speed regulator and 5045 blades are adopted as a power system. The total mass of the body in flight is about 650g and the load mass to which the disturbance is applied is about 150 g.
In order to verify the excellent performance of the outer ring position controller in an actual flight experiment, the effectiveness of the designed controller is verified from the aspects of the anti-interference performance under the fixed-point condition and the tracking performance under the track tracking condition. Applying a certain degree of disturbance to an actual four-rotor aircraft under the condition of a fixed position, and respectively observing the position response conditions of x and y channels in the horizontal direction, as shown in fig. 7 and 8; and the position tracking error of the x and y channels is observed by tracking a circular track, as shown in fig. 9 and 10.
It can be seen that in the whole fixed-point hovering process, before 60s, the four-rotor aircraft is in a non-disturbance (small-disturbance) fixed-point hovering state, and the error of the two position channels is basically stabilized at + -5cm at the moment, so that certain tracking accuracy is achieved; after 60s, a certain horizontal disturbance is applied to the observer, the observer is observed to oscillate in a small range near a fixed point, the oscillation error is about + -10cm, and the observer can finally reach a convergence state at a faster speed, which means that the observer can estimate and compensate the external disturbance more quickly and accurately, and meanwhile, the observer is ensured not to diverge. The control delay of the whole process is low, which shows that the observer has excellent performance, can realize rapid and accurate estimation and compensation of large and severe disturbance, and meets the requirement of certain disturbance rejection capability.
In the aspect of track tracking, the position controller based on the active disturbance rejection technology is used as an outer ring controller to track a circular track, so that the track tracking conditions in the x and y directions in the actual tracking process basically meet the requirements, the tracking error is basically limited to + -10cm, and the overall tracking effect is good. The only disadvantage is that there is some control compensation lag resulting in tracking inaccuracy, which may be due to insufficient compensation delay of the observer, which can be improved by subsequent parameter adjustments.
In summary, the above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (4)
1. Four-turn based on active disturbance rejectionThe method for controlling the position of the wing aircraft is characterized in that an active disturbance rejection controller is designed aiming at a position control model of the four-rotor aircraft; in the designed active disturbance rejection controller, a position signal y fed back by a controlled object is subjected to smooth noise reduction processing by a tracking differentiator and then is sent to an observer; the observer adopts a three-order extended state observer, and observes and estimates each order state of the position control model and internal and external disturbance acting on the model by utilizing position information after smooth noise reduction and control quantity u (t-tau) added with motor response delay tau; subtracting the estimation quantity of the position and the speed output by the observer from a given quantity, and calculating the difference value through a nonlinear control rate to obtain a primary control quantity u0Finally, the disturbance estimator obtained by the third-order extended state observer is used for estimating the initial control quantity u0After compensation is carried out on the basis, the final output control quantity u (t) is obtained;
establishing a PID controller parallel to the active disturbance rejection controller; adopting a PID controller to control a manual takeoff process, starting to simultaneously operate the PID controller and an active disturbance rejection controller after the aircraft enters an automatic mode and is stably suspended, and adopting the output quantity of the PID controller as an actual output control quantity at the moment; and judging whether the difference of the output control quantities calculated by the two controllers is within a certain range, and if the output control quantities of the active disturbance rejection controller are not dispersed and the difference of the output control quantity numerical values calculated by the two controllers is within a certain range, switching to the active disturbance rejection controller control.
2. The method of claim 1, wherein the tracking differentiator is constructed using a steepest synthesis function fhan; in the steepest synthesis function, the fast factor r is 104Magnitude data, filter factor h1By using 10-2Magnitude data.
3. An active-disturbance-rejection based quad-rotor aircraft position control system, comprising an active-disturbance-rejection controller; the active disturbance rejection controller comprises a tracking differentiator, an observer, a nonlinear control rate calculation module, a time delay module and a control quantity compensation module; the four-rotor aircraft position control system also comprises a PID controller, a switching control module and a switch;
a tracking differentiator for smoothing and denoising the position signal y fed back by the controlled object to obtain a smoothed position signal y1Feeding into an observer;
the time delay module is used for adding the output control quantity u (t) into the motor response time delay tau to form u (t-tau) which is input into the observer;
the observer adopts a three-order extended state observer for utilizing the smoothed position signal y1And adding a time delay control quantity u (t-tau), observing and estimating each stage state of the position control model and internal and external disturbance acting on the model to obtain a position estimation quantity z1Velocity estimator z2And a disturbance estimator;
a non-linear control rate calculation module for estimating the position z1And velocity estimator z2Making difference with given quantity, calculating nonlinear control rate to obtain initial control quantity u0；
A control quantity compensation module for utilizing the disturbance estimation quantity obtained by the third-order extended state observer to obtain the preliminary control quantity u0On the basis of the control signal, compensating to obtain a final output control quantity u (t);
the switching control module is used for controlling the switching switch to enable the PID controller to work in a manual takeoff stage; after the aircraft enters an automatic mode and is stably suspended, the PID controller and the active disturbance rejection controller work simultaneously by controlling the selector switch, but the output quantity of the PID controller is still adopted as the actual output control quantity at the moment; and judging whether the difference between the output control quantities calculated by the two controllers is within a certain range, and if the output control quantities of the active disturbance rejection controller are not dispersed and the difference between the output control quantity values calculated by the two controllers is within a certain range, switching to the active disturbance rejection controller to work by controlling a selector switch.
4. The system of claim 3, wherein the tracking differentiator is constructed using a steepest synthesis function fhan; among the fastest synthesis functions, the fast factorSub r is 104Magnitude data, filter factor h1By using 10-2Magnitude data.
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