Inter national J our nal of Robotics and A utomation (IJRA) V ol. 10, No. 4, December 2021, pp. 308 318 ISSN: 2089-4856, DOI: 10.11591/ijra.v10i4.pp308-318 308 Adjustment mechanism with sliding mode f or adapti v e PD contr oller applied to unmanned xed-wing MA V altitude A.T . Espinoza-Frair e, A. S ´ aenz-Esqueda, F . C ´ ortes-Mart ´ ınez F acultad de Ingenier ´ ıa, Ciencias y Arquitectura, Uni v ersidad Ju ´ arez del Estado de Durango, G ´ omez P alacio, Durango, M ´ exico Article Inf o Article history: Recei v ed Jul 30, 2020 Re vised Jun 10, 2021 Accepted Jul 23, 2021 K eyw ords: Adapti v e control Altitude mode Unmanned ABSTRA CT This w ork presents an adjustment mechanism with the sliding modes technique to de- sign a proportional deri v ati v e (PD) controller with adapti v e g ains. The objecti v e and contrib ution are to design a rob ust adjustment mechanism in the presence of unkno wn and not modeled perturbations in the system; this perturbation can be considered wind gusts. The rob ust adjustment mechanism is designed with the MIT rule and the gra- dient method with the sliding mode theory . The adapti v e PD obtained is applied to re gulate unmanned x ed-wing miniature aerial v ehicle (MA V’ s) altitude. This is an open access article under the CC BY -SA license . Corresponding A uthor: A.T . Espinoza-Fraire F acultad de Ingenier ´ ıa, Ciencias y Arquitectura Uni v ersidad Ju ´ arez del Estado de Durango Uni v ersidad 1021, Filadela, 35010 Dgo, G ´ omez P alacio, Durango, M ´ exico Email: atespinoza@ujed.mx 1. INTR ODUCTION The de v elopment and use of unmanned aerial systems (U A Vs) ha v e been increasing in the last decade [1], [2], and the theory about adapti v e control is fundamental in the de v elopment and adv ances in this eld. And e v en the applications of the x ed-wing U A Vs are increasing; some applications are: forest re detection, in ci vil engineering (topograph y , analysis structural and others) [3], photogrammetry , and military applications [4], car detection [5] or for landing [6]. W e can nd some w orks in the scientic literature referents to adapti v e control based on the MIT rule. F or e xample, in [7] is de v eloped a model reference based on a proportional inte gral deri v ati v e (PID) controller . Compared with a con v entional or ordinary reference model, this is done to get better performance in the control of the v elocity of a DC motor . P a w ar and P arv at [8] is presented a modication in the structure of an model reference adapti v e control (MRA C) the modication is based on a PID controller as in [7]. Still, the dif ference is that in [8] the PID is used between other controllers based in MRA C and the plant, the proposed of [8] has the objecti v e of impro ving the transient response of the plant, and it uses the kno wn MRA C structure [9]. Whereas in [10] the direct model reference adapti v e and an internal controller is applied to doubly fed induction generator and in this w ork, is proposed the adjustment mechanism based on MIT rule. Still , in addition, the Perrin equation has been added to this mechanism with an impro v ed internal model controller lter design. Thus, in [10] the adjustment mechanism using the Perrin equation is intending to a v oid the selection of the adapti v e g ain by a heuristic method. Priyank and Nig am [11] is presented the design of a MRA C for a second-order system, that is, is presented a modied MIT rule to resolv e tw o problems that present the MIT rule, these problems are that with a suf ciently lar ge selection of the adaptation g ain or in the magnitude of the reference signal the system tends to the instability . And then, to gi v e a solution to these problems, in [11] a normalized algorithm with J ournal homepage: http://ijr a.iaescor e .com Evaluation Warning : The document was created with Spire.PDF for Python.
Int J Rob & Autom ISSN: 2089-4856 309 MIT rule is presented to de v elop the control la w . Riache et al. [12] is presented an adapti v e rob ust controller applied to quadrotor with a serial robot manipul ator onboard, the control objecti v e in [12] is that during the ight, mo v e the robot arm and k eep the desired trajectory . On the other hand, the w orks [7], [8], [10], [11] presents simulations results using the Matlab soft w are as well as in this w ork. W e can nd other adapti v e controllers applied to x ed-wing unmanned aerial v ehicle (U A V) as in [13] where is presented the guidance system mak es the airplane follo ws pre-computed references using a no v el iterati v e model predicti v e scheme, which can handle the nonlinear optimization problem by successi v e linearizations (starting the algorithm using a rob ust l 1 na vig ation la w . On the other hand, in [14] is presented an adapti v e control to compensate the unkno wn parameters of an unmanned aerial v ehicle with x ed-wing in normal condition ight, the control objecti v e is to achie v e a desired speed and roll angle, and after that to track desired path with minimum error . An adapti v e neuro-fuzzy controller is presented in [15], where is de v eloped an autonomous ight controller for x ed-wing U A V based on adapti v e neuro-fuzzy inference system (ANFIS). Three ANFIS modules are designed for controlling the altit ude, the heading angle, and the speed of the U A V . In this w ay , the U A V position is controlled in three-dimensional space: altitude, longitude, and latitude position. The simulation results sho w the capability of the designed approach and its v ery satisf actory performance with good stability and rob ustness ag ainst U A V parametric uncertainties and e xternal wind disturbance. Zhou et al. [16] is presented an attitude dynamic model of unmanned aerial v ehicles, considering a strong coupling in the aerodynamic model. Model uncertainties and e xte rnal gust disturbances are considered during designing the attitude control system for U A Vs and feedback linearization and M RA C are inte grated to design the attitude control system for a x ed-wing U A V . Qiu et al. [17] is presented the dynamics and attitude control of a mass-actuated x ed-wing U A V (MFU A V) with an internal slider . Based on the deri v ed mathematical model of the MFU A V , the inuence of the slider parameters on the dynamical beha vior is ana- lyzed, and the ideal installation position of the slider is gi v en. Besides, it is re v ealed that the mass-actuated scheme has a higher control ef cienc y for lo w-speed U A Vs. T o deal with the coupling, uncertainty , and dis- turbances in the dynamics, an adapti v e sliding mode controller based on fuzzy system, radial basis function (RBF) neural netw ork, and sliding mode control are proposed. P atel and Bhandari [18] is presented a neu- ral netw ork-based nonlinear adapti v e controller for a x ed-wing U A V , in [18] is used both of ine and online trained neural netw orks. Multi-layer perceptron (MLP) netw orks are used for the training of both the of f-line and online netw orks. Ev en in the scientic literature, we can nd some controllers for x ed-wing U A Vs that are not adap- ti v e controllers, as in [19] is proposed a comprehensi v e approach combining backstepping with PID controllers for simultaneous longitudinal and lateral-directional control of x ed-wing U A Vs. Kayacan et al. [20] is pre- sented a learning control s trate gy is preferred for the control and guidance of a x ed-wing unmanned aerial v ehicle to deal with lack of modeling and ight uncertai nties. F or learning the plant model and changing w orking conditions online, a fuz zy neural netw ork (FNN) is used in parallel with a con v entional proportional (P) controller . Among the learning algorithms in the literature, a deri v ati v e-free one, the sliding mode control (SMC) theory-based learning algorithm, is preferred as it has been pro v ed to be computationally ef cient in real-time applications. On the other hand, in [21] is presented a m od e l-free control (MFC) that is an algorithm dedicated to systems with poor modeling kno wledge. Indeed, the costs to deri v e a reliable and representati v e aerodynamic model for U A Vs moti v ated the use of such a controller . W e can see that e v ery application or control theory applied to x ed-wing U A Vs is necessary to de v elop an altitude control la w . Then, in this w ork, our control objecti v e is to design an altitude controller in the pres- ence of perturbations in unmanned x ed-wing miniature-aerial-v ehicle (MA Vs); the perturbations mentioned are the wind gusts. Exists al titude controllers with g ains denite x, b ut the problem with such controllers is that it w orks in specic altitudes (x ight points). On the other side, adapti v e controllers e xist that can w ork in dif ferent altitude points b ut present some problems in k eeping control objecti v es in perturbations. So in this w ork, we ha v e proposed an adapti v e controller that can lead an unmanned x ed-wing MA V to dif ferent altitudes in the presence of wind gusts (perturbations). As is mentioned in [9] the problem to resolv e an model reference adapti v e system (MRAS) is to determine the adjustment mechanism to stabilize the system and which achie v es the error to zero. Then a solution to this problem is the de v elopment of a proportional-deri v ati v e (PD) controller with adapti v e g ains. This adaptation is based on the adapti v e scheme kno wn as MRAS. Then, to achie v e the control objecti v e, we ha v e designed a rob ust adjustment mechanism for the adapti v e g ains of a PD controller . Our proposal to design it is using the MIT rule, an approach to model-reference adapti v e control and gradient method with sliding Evaluation Warning : The document was created with Spire.PDF for Python.
310 ISSN: 2089-4856 mode theory . The obta ined rob ust adapti v e mechanism for the adapti v e controller PD is going to compare with the kno wn adapti v e mechanism de v eloped in [9], that is, to demonstrate the adv antages in the error and the control ef fort concerning de v eloped in this w ork. The or g anization of the document is the follo wing: in the section 2. is presented the longitudinal model which denes the x ed-wing MA V and in the section 3. is sho wn the design of the adapti v e mechanism and the PD controller . In section 4. is presented the simulation results obtained, and nally , section 5. presents the conclusions and the future w ork. 2. LONGITUDIN AL MODEL T o re gulate the altitude of the x ed-wing MA V is used the aerodynamic model which denes the longitudinal model of an airplane. Then, this aerodynamic model has been obtained based on t h e second mo v ement la w of Ne wton; some considerations are tak en for the model obtention, that is, the earth is considered as plane due to the x ed-wing MA V is going to y short distances, and is not consider an y e xible part in the airplane for the dynamic model. Then, the longitudinal model of the airplane has been dened as (1), (2), (3), (4) and (5). ˙ V = 1 m ( D + T cos α mg sin γ ) (1) ˙ γ = 1 mV ( L + T sin α mg ) sin γ ) (2) ˙ θ = q (3) ˙ q = M q q + M δ e δ e (4) ˙ h = V sin( θ ) (5) Where V is the airplane speed, α describes the angle of attack, γ represents the ight-path angle, and θ denotes the pitch angle. In addition, q is the pitch angular rate (concerning the y -axis of the aircraft body), T denotes the force of engine thr u s t, h is the airplane altitude [22], [23] and δ e represents the ele v ator de viation. The aerodynamic ef fects on the airplane are obtained by the lift force L and the drag force D . The total mass of the airplane is denoted by m , g is the gra vitational constant, and I y y describes the component y of the diagonal of the inertial matrix. The v alue of the angle of attack is obtained by using the follo wing relation α = θ γ [22], the Figure1 sho ws the v ariables implies in the pure pitch motion to apply control in altitude. In aerodynamics, M q and M δ e are the stability deri v ati v es implicit in the pitch motion. The lift force L , the drag force D are dened as (6) and (7) [22], [23]. L = ¯ q S C L (6) D = ¯ q S C D (7) The aerodynamic stability deri v ati v es are dened by: where ¯ q denotes aerodynamic pressure. S represents the wing platform area, and ¯ c is the mean aerodynamic chord. C D and C L are the aerodynamic coef cients for drag force and lift force, respecti v ely . M q = ρS V ¯ c 2 4 I y y C m q M δ e = ρV 2 S ¯ c 2 I y y C m δ e Where: ρ : Air density (1.05 kg/m 3 ). S : W ing area (0.09 m 2 ). ¯ c : Standard mean chord (0.14 m ). b : W ingspan, (0.914 m ). I y y : Moment of inertia in pitch (0.17 k g · m 2 ). C m q : Dimensionless coef cient for longitudinal mo v ement, it is obtained e xperimentally (-50). C m δ e : Dimensionless coef cient for ele v ator mo v ement, it is obtained e xperimentally (0.25). Int J Rob & Autom, V ol. 10, No. 4, December 2021 : 308 318 Evaluation Warning : The document was created with Spire.PDF for Python.
Int J Rob & Autom ISSN: 2089-4856 311 L W D V q ± e Figure 1. Pure pitching motion 3. CONTR OLLER DESIGN T o design the adapti v e controller for altitude, we ha v e considered the (3), (4) and (5), this is due to which the (1) represents the v elocity of the airplane. Still, for the simulations of this w ork, it is considered as constant, and the (2) is the ight path produced by the wind. In this w ork, we are designing the control la w o v er the solid (aircraft body). F or that reason, the control la w is designed without considering the wind equations which dene the a irplane dynamics. Then, the altitude error is dened as ˜ e h = h d h , where h d is the desired altitude and h is the actual altitude. The desired altitude is achie v ed by controlling the pitch angle. Thus we ha v e dened an error for this angle, gi v en by ˜ e θ = θ d θ ( t ) , where θ d = ar c tan ( ˜ e h ) is the des ired pitch angle, and ς denotes the longitude from the center of mass of the miniature aerial v ehicle to the nose of it. Consider the equations (3) and (4), δ e denes the control input. Thus, The adapti v e control is gi v en by (8). δ e = ˆ k pa ˜ e θ + ˆ k v a ˙ ˜ e θ (8) Where ˆ k pa and ˆ k v a are called as the position and v elocity g ains, respecti v ely , these are the adapti v e g ains. The g ains of the PD control ha v e implicit a subscript to indicate the algorithm that has been applied as adjustment mechanism, a 1 corresponds to the MIT rule, a 2 corresponds to the MIT rule with sliding-mode, a 3 uses the MIT rul e with 2-sliding-mode, and a 4 represents the MIT rule with HOSM. Therefore, for the design of the MIT rule, it is introduced an error gi v en by (9). e θ m = θ m θ (9) Where θ m is the output from the reference model, we ha v e follo wed the methodology that has been presented in [9] for the MIT rule, taking this into account, the aerodynamic model has been transformed into the rep- resentation of a transference function to de v elop the deri v ati v es of sensiti vity; t hese ha v e been obtained by computing partial deri v ati v es concerning the controller parameters ˆ k pa and ˆ k v a . Thus, the closed-loop transfer function with the adapti v e PD controller has been dened as (10). θ = M δ e ( ˆ k p + ˆ k v s ) s 2 + ( M q + M δ e ˆ k v ) s + M δ e ˆ k p θ d (10) And the model of reference for the altitude dynamics has been dened as (11). θ m = ω 2 n s 2 + 2 ζ ω n s + ω 2 n θ d (11) Where ζ = 3 . 17 and ω = 3 . 16 . Considering (9), (10) and (11) and calculating the partial deri v ati v es with respect to ˆ k pa and ˆ k v a , it is obtained as (12) and (13). e θ m ˆ k p = M δ e s 2 + ( M q + M δ e ˆ k v ) s + M δ e ˆ k p ( θ θ d ) (12) e θ m ˆ k v = M δ e s s 2 + ( M q + M δ e ˆ k v ) s + M δ e ˆ k p ( θ θ d ) (13) Evaluation Warning : The document was created with Spire.PDF for Python.
312 ISSN: 2089-4856 Generally , the e xpressions (12) and (13) cannot be used due to the unkno wn parameters ˆ k pa and ˆ k v a . So that, an optimum case has been assumed and it is dened as (14). s 2 + ( M q + M δ e ˆ k v l ) s + M δ e ˆ k pl = s 2 + 2 ζ ω n s + ω 2 n (14) thus, after these approximations, we ha v e obtained the dif ferential equations of the adapti v e PD controller . ˙ ˆ k pa 1 = γ 1 1 s 2 + 2 ζ ω n s + ω 2 n ( θ θ d e θ m (15) ˙ ˆ k v a 1 = γ 2 s s 2 + 2 ζ ω n s + ω 2 n ( θ θ d ) e θ m (16) No w , it is proposed an MIT rule with second-order sliding mode; this approach is dif ferent t han the dened in [9]. Thus, it is dened a sliding-mode surf ace as s 1 = ˙ θ m q + k 1 e θ m (we are searching increase the stability of the adjustment mechanism), where k 1 is a positi v e g ain. Then, the dif ferential equations of the adapti v e controller , with the methodology by sliding-mode, are gi v en by (17) and (18). ˙ ˆ k pa 2 = γ 1 1 s 2 + 2 ζ ω n s + ω 2 n ( θ θ d ) ( β p ( s 1 )) (17) ˙ ˆ k v a 2 = γ 2 s s 2 + 2 ζ ω n s + ω 2 n ( θ θ d ) ( β v ( s 1 )) (18) Where β p and β v are positi v e v alues. Due to the chattering ef fect of the rst order sliding-mode, let us design an adjustment mechanism with a second-order sliding mode. This second-order sliding mode includes a rob ust dif ferentiator of rst-order [24]. This dif ferentiator is dened by (19). ˙ x 0 = v 0 = λ 0 | x 0 s 1 | 1 / 2 ( x 0 s 1 ) + x 1 ˙ x 1 = λ 1 ( x 1 v 0 ) (19) Where x 0 and x 1 are real-time estimations of s 1 and ˙ s 1 , respecti v ely . The v alues of λ 1 and λ 2 are positi v es and constants. Thus, the dif ferential equations of the adapti v e PD controller with a second- order sliding mode are dened by (20) and (21). ˙ ˆ k pa 3 = γ 1 1 s 2 + 2 ζ ω n s + ω 2 n ( θ θ d ) ( β p ( s 1 ) + β p 2 ( ˙ s 1 )) (20) ˙ ˆ k v a 3 = γ 2 s s 2 + 2 ζ ω n s + ω 2 n ( θ θ d ) ( β v ( s 1 ) + β v 2 l ( ˙ s 1 )) (21) Where β p , β p , β v and β v are positi v e denite g ains. T o reduce or eliminate the chattering ef fect in the second-order sliding mode, we h a v e des igned an adjustment mechanism with HOSM. T o design the adjustment mechanism, it i s necessary a rob ust dif ferentiator of second-order [24], which is gi v en by (22). ˙ x 0 = v 0 = λ 0 | x 0 s 1 | 2 / 3 ( x 0 s 1 ) + x 1 ˙ x 1 = v 1 = λ 1 | x 1 v 0 | 1 / 2 ( x 1 v 0 ) + x 2 (22) ˙ x 2 = λ 2 | x 2 v 1 | Where x 0 , x 1 y x 2 are real-time estimations of s 1 , ˙ s 1 and ¨ s 1 . The v alues of λ 0 , λ 1 and λ 2 are dened as positi v e constants. Finally , the dif ferential equations of the adapti v e PD controller with HOSM are dened by (23) and (24). Int J Rob & Autom, V ol. 10, No. 4, December 2021 : 308 318 Evaluation Warning : The document was created with Spire.PDF for Python.
Int J Rob & Autom ISSN: 2089-4856 313 ˙ ˆ k pa 4 = γ 1 1 s 2 + 2 ζ ω n s + ω 2 n ( θ θ d ) ( α pl [ ¨ s 1 l + 2( | ˙ s 1 l | 3 + | s 1 l | 2 ) 1 / 6 ( ˙ s 1 l + | s 1 l | 2 / 3 ( s 1 l ))]) (23) ˙ ˆ k v a 4 = γ 2 s s 2 + 2 ζ ω n s + ω 2 n ( θ θ d ) ( α v [ ¨ s 1 + 2( | ˙ s 1 | 3 + | s 1 | 2 ) 1 / 6 ( ˙ s 1 + | s 1 | 2 / 3 ( s 1 ))]) (24) Where α p and α v are positi v e and constant g ains. 4. SIMULA TION RESUL TS T o describe the simulations results with the MIT -rule with sliding mode theory , we ha v e analyzed the results with the L 2 -norm [25], that is, to analyze the error signals and the control ef fort with the dif ferents adapti v e mechanism proposed. Then, we ha v e applied the L 2 -norm to the error (25): L 2 [ e h ] = s 1 T t 0 Z T t 0 e h 2 dt (25) The L 2 -norm is also used to obtain the ef fort of the control la w , and it is dened as (26): L 2 [ δ e ] = s 1 T t 0 Z T t 0 δ e 2 dt (26) Thus, with the use of the (25) and (26) are obtained the errors and ef forts, see the T able 1. T able 1. L 2 -norm for the errors and the ef forts of the control la ws on the altitude mo v ement Adapti v e mechanism Altitude [m] L 2 [ e h ] L 2 [ δ e ] MIT 1.2949 0.2876 MIT -SM 1.2913 0.2689 MIT -2SM 1.0856 0.2362 MIT -HOSM 1.0773 0.2519 The simulations results for the altitude control applying the MIT rule [9], are presented in the Figure 2, in the upper graphic of the Figure 2 is presented the response of the MIT rule and in the lo wer graphic of the same gure, sho ws the controller response. Analyzing the results obtained in the T able 1 is appreciated that the PD controller with the adapti v e mechanism based on the MIT rule has presented more error than the MIT with the sliding mode theory , that is, the MIT rule is 0 . 278% , 16 . 1635% and 16 . 8044% bigger than MIT rule with sliding mode (MIT -SM), the MIT rule with tw o sliding modes (MIT -2SM) and the MIT rule with high order sliding mode (MIT -HOSM), respecti v ely . Meanwhile, the PD control ef fort with the MIT rule is bigger than the other technique in the st udy , that is, with the adapti v e mechanism by the MIT rule, the PD control ef fort is 6 . 5021% , 17 . 8721% and 12 . 4131% bigger than the MIT -SM, the MIT -2SM and the MIT -HOSM, respecti v ely (see the T able 1). On the other hand, the error of the PD controller with the adapti v e mechanism based on the MIT rule with the sliding mode is 15 . 9297% bigger than the MIT -SM and is 16 . 5725% bigger than the MIT -HOSM. The results obtained with the adapti v e mechanism bas ed on MIT rule with sliding mode are presented in the Figure 3, where the upper graphic of the same gure we can appreciate the con v er gence to the desired v alues in spite of the noise applied in the control system. In T able 1 we can see that the PD controller with the adapti v e mechanism based on the MIT rule with sliding mode applies a control signal 12 . 1607 bigger than the adapti v e mechanism based on the MIT rul e with Evaluation Warning : The document was created with Spire.PDF for Python.
314 ISSN: 2089-4856 tw o sliding modes (MIT), and e v en the adapti v e mechanism with the MIT rule with the sliding mode the control ef fort is 6 . 3221% bigger than the MIT -HOSM. In the lo wer graphic of the Figure 3 is sho wn the control signal generated by the PD with the adapti v e mechanism based on the MIT rule with the sliding mode. Time (s) 0 100 200 300 400 500 600 700 800 900 1000 Altitude (m) -2 0 2 4 6 Altitude (MIT-Sign) Reference Actual altitude Time (s) 0 100 200 300 400 500 600 700 800 900 1000 u θ  (deg) -20 -10 0 10 20 Control signal MIT-Sign Figure 2. Adapti v e mechanism based on the MIT -rule with sign function Time (s) 0 100 200 300 400 500 600 700 800 900 1000 Altitude (m) -2 0 2 4 6 Altitude (MIT-SM) Reference Actual altitude Time (s) 0 100 200 300 400 500 600 700 800 900 1000 u θ  (deg) -20 -10 0 10 20 Control signal MIT-SM Figure 3. Adapti v e mechanism based on the MIT -rule with sliding mode Figure 4 is presented the results obtained by the PD controller based on the MIT -2SM, in the upper graphic is appreciated the response of the PD controller with the adapti v e mechanism based on the MIT -2SM. In T able 1 we can see that the PD controller based on the MIT -2SM has presented an error 15 . 9297% bigger than the MIT -HOSM, b ut the adapti v e mechanism based on the MIT with tw o sliding modes has pre- sented a PD control ef fort 6 . 2327% smaller than the MIT -HOSM. In the lo wer graphic of Figure 4 is presented the response of adapti v e mechanism based on the MIT rule with tw o sliding modes. Meanwhile, the response of PD controller with the adapti v e mechanism based on the MIT -HOSM is presented in Figure 5, in the upper graphic of the same gure is sho wn the con v er gence to the desired v alues and in the upper graphic is presented the controller response. Int J Rob & Autom, V ol. 10, No. 4, December 2021 : 308 318 Evaluation Warning : The document was created with Spire.PDF for Python.
Int J Rob & Autom ISSN: 2089-4856 315 The PD controller based on the MIT -HOSM has a lo wer error in comparison with the other adapti v e mechanisms presented in this w ork and e v en presents a smaller control action when is compared with the PD controller with the adapti v e mechanism based on the MIT r ule and with them based on the MIT rule with sliding mode. An e xception occurs when it is compared with the adapti v e mechanism based on the MIT rule with tw o sliding modes (see T able 1). And nally , the adv antage of using the PD controller with the adapti v e mechanism based on the MIT rule with high order sliding mode is the reduction in the undesired chattering ef fect in the control signal, the e v olution of the chattering reduce e v en with the perturbation in the system, this can be appreciated in the Figure 6. Time (s) 0 100 200 300 400 500 600 700 800 900 1000 Altitude (m) -2 0 2 4 6 Altitude (MIT-2SM) Reference Actual altitude Time (s) 0 100 200 300 400 500 600 700 800 900 1000 u θ  (deg) -20 -10 0 10 20 Control signal MIT-2SM Figure 4. Adapti v e mechanism based on the MIT -rule with tw o sliding mode Time (s) 0 100 200 300 400 500 600 700 800 900 1000 Altitude (m) -4 -2 0 2 4 6 Altitude (MIT-HOSM) Reference Actual altitude Time (s) 0 100 200 300 400 500 600 700 800 900 1000 u θ  (deg) -20 -10 0 10 20 Control signal MIT-HOSM Figure 5. Adapti v e mechanism based on the MIT -rule with HOSM Evaluation Warning : The document was created with Spire.PDF for Python.
316 ISSN: 2089-4856 Tiempo (s) 0 100 200 300 400 500 600 700 800 900 1000 u θ  (deg) -1 -0.5 0 0.5 1 Control signal MIT-Sign Time (s) 0 100 200 300 400 500 600 700 800 900 1000 u θ  (deg) -1 -0.5 0 0.5 1 Control signal MIT-SM Time (s) 0 100 200 300 400 500 600 700 800 900 1000 u θ  (deg) -1 -0.5 0 0.5 1 Control signal MIT-2SM Time (s) 0 100 200 300 400 500 600 700 800 900 1000 u θ  (deg) -1 -0.5 0 0.5 1 Control signal MIT-HOSM Figure 6. Control signals zoom 5. CONCLUSION The adapti v e mechanism based on the MIT rule presented an error and control ef fort bigger than the MIT rule wi th the sliding mode techniques. Despite it, the adapti v e controller with the MIT rule as an adapti v e mechanism for the controlle r g ains achie v es the desired altitude. The adapti v e mechanism based on the MIT rule with high order sliding mode has presented a better performance than the other adapti v e mechanisms presented in this w ork, considering that the altitude error is the smallest. Ev en this adapti v e mechanism for the PD controller has presented less control ef fort than the adapti v e mechanisms based on the MI T rule and MIT rule with sliding mode. The PD controller with the adapti v e mechanism based on the MIT rule with high order sliding mode has presented a considerable reduction of the chattering ef fect . The future w ork consists of the implementation (real-time ight tests) of this technique in a miniature aerial v ehicle to analyze the performance of the PD controller with the adapti v e mechanisms proposed in this w ork. A CKNO WLEDGMENT The authors w ould lik e to thank F acultad de Ingenier ´ ıa, Ciencias y Arquitectura From the Uni v ersidad Ju ´ arez del Estado de Durango for the support during the de v elopment of this w ork. Int J Rob & Autom, V ol. 10, No. 4, December 2021 : 308 318 Evaluation Warning : The document was created with Spire.PDF for Python.
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