Inter national J our nal of Electrical and Computer Engineering (IJECE) V ol. 9, No. 5, October 2019, pp. 3779 3785 ISSN: 2088-8708, DOI: 10.11591/ijece.v9i5.pp3779-3785 r 3779 The best quintic chebyshe v appr oximation of cir cular ar cs of order ten Abedallah Rababah Department of Mathematics, Jordan Uni v ersity of Science and T echnology , Jordan Article Inf o Article history: Recei v ed Feb 19, 2019 Re vised Apr 4, 2019 Accepted Apr 9, 2019 K eyw ords: High performance computing B ´ ezier curv es Quintic approximation Circular arc High accurac y Approximation order CAD ABSTRA CT Mathematically , circles are represented by trigonometric parametric equations and im- plicit equations. Both forms are not proper for computer applications and CAD sys- tems. In this paper , a quintic polynomial approximation for a circular arc is presented. This approximation is set so that the error function is of de gree 10 rather than 6 ; the Chebyshe v error function equioscillates 11 times rather than 7 ; the approximation order is 10 rather than 6 . The method approximates more than the full circle with Chebyshe v uniform error of 1 = 2 9 . The e xamples sho w t he competence and simplicity of the proposed approximation, and that it can not be impro v ed. Copyright c 2019 Insitute of Advanced Engineeering and Science . All rights r eserved. Corresponding A uthor: Abedallah Rababah, Department of Mathematics, Jordan Uni v ersity of Science and T echnology , 22110 Irbid, Jordan. Email: rababah@just.edu.jo 1. INTR ODUCTION Only NURBS (Non Uniform Rational B-Splines) are capable to properly symbolize circles. NURBS ha v e mathematical frame and harnessing them depends on mathematical kno wledge and, in significant cases, demands the potential of emplo ying geometric and analytic concepts. Ho we v er , circles are directed to be used by people of limited and e xclusi v e kno wledge of mathem atical notions and processes lik e computer graphics designers, stylers, animators, computer aided designers, and engineers. Dra wing a circle in an y CAD system is the primary alphabet in an y softw are. So, it is v ery genuine to ha v e the circl e as a primiti v e and as a b uilt- in-function in the softw are. A circle can be represented using rational B ´ ezier curv es and can be approximated by polynomial curv es. Therefore, approximating a circular arc by polynomial curv es with highest possible accurac y is a v ery important matter [1]. W e treat the circular arc c : t 7! (cos( t ) ; sin( t )) ; t , see Figure 1, to be approximated by a polynomial curv e with superior uniform approximation. T o come to this consequence, the geometric symmetries of the circle are used to f airly choose the B ´ ezier points in order to symbolize the quintic B ´ ezier curv e that has highest approximation order of 10 . The circle c is approximated in this paper using a quintic parametrically defined polynomial curv e p : t 7! ( x ( t ) ; y ( t )) ; 0 t 1 , where x ( t ) ; y ( t ) are polynomials of de gree 5 , that approximates c with least de viation. Man y researchers ha v e tackled this issue using dif ferent de grees, norms, and methods, see for e xample [2, 3, 4, 5, 6, 7, 8, 9] and the references therein. In [10], methods for approximating circular arcs using quintic polynomial curv es with dif ferent bound- ary conditions are conside red. The results of our method in this paper outperform the results in [10], J ournal homepage: http://iaescor e .com/journals/inde x.php/IJECE Evaluation Warning : The document was created with Spire.PDF for Python.
3780 r ISSN: 2088-8708 are optimal, and can not be impro v ed. The error function to measure the distance between p and c is the follo wing radial basis distance: E ( t ) := p x 2 ( t ) + y 2 ( t ) 1 : (1) The radial distance formula contains radicals and thus will be replaced by the follo wing de viation measure: e ( t ) := x 2 ( t ) + y 2 ( t ) 1 : (2) Since the error function e ( t ) = 0 represents the implicit equation of the circle; thus it is the suitable measure to test if x ( t ) and y ( t ) satisfy the equation of the circle and to measure the error . q - q 1 Figure 1. A circular arc Among all possible kinds of approximations, the best uniform approximation yields the most accurate approximation. Unfortunately , in the li terature, there is no method to find the best uniform approximation of de gree fi v e that approximates with order 6 [11]. In this paper , the quintic best uniform approximation is found that approximates with order 10 rather that 6 . This is a significant impro v ement o v er the order of the Chebyshe v and Borel theorems [11]. In particular , the approximation problem that is considered in this paper is to locate a polynomial curv e p : t 7! ( x ( t ) ; y ( t )) ; 0 t 1 , where x ( t ) ; y ( t ) are quintic polynomials, that ”mimics” c and minimizes max t 2 [0 ; 1] j e ( t ) j . Moreo v er , the follo wing conditions are fulfilled: (a) e ( t ) equioscillates 11 times o v er [0 ; 1] rather than 7 , (b) p approximates c with order 10 rather than 6 . These conditions are used to locate the B ´ ezier points and to get the v alues of the parameters that are utilized to satisfy the geometric conditions of the circular arc. F or more on these topics, see [1]. T o achie v e the conditions of the issue of the approximation, the follo wing feature of the Chebyshe v polynomials is used. Namely , the monic Chebyshe v polynomial ~ T 10 ( u ) ; u 2 [ 1 ; 1] , gi v en by ~ T 10 ( u ) = 1 512 + 25 256 u 2 25 32 u 4 + 35 16 u 6 5 2 u 8 + u 10 ; u 2 [ 1 ; 1] (3) is the unique polynomial of de gree 10 that equioscillates 11 times between 1 2 9 for all u 2 [ 1 ; 1] and has the least de viation from the x -axis [11]. Since the uniform error (for e ( t ) ) equals 2 9 , so, we allo w the angle to be as lar ge as possible in order to approximate the lar gest circular arc with this specified error . Ther eafter , this angle has to be scaled by a f actor that also combined with a reduction in the uniform error , see the last conclusions and open problems’ section. Int J Elec & Comp Eng, V ol. 9, No. 5, October 2019 : 3779 – 3785 Evaluation Warning : The document was created with Spire.PDF for Python.
Int J Elec & Comp Eng ISSN: 2088-8708 r 3781 2. RESEARCH METHOD The curv e p ( t ) is gi v en in B ´ ezier form in order to use the B ´ ezier technique [13]. See Figure 2 for possible B ´ ezier points of a quintic B ´ ezier curv e. A B ´ ezier curv e p ( t ) of de gree 5 is gi v en by p ( t ) = 5 X i =0 p i B 5 i ( t ) =: x ( t ) y ( t ) ; 0 t 1 : (4) The points p 0 ; p 1 ; p 2 ; p 3 ; p 4 and p 5 are called the B ´ ezier points, and the polynomials B 5 0 ( t ) = (1 t ) 5 ; B 5 1 ( t ) = 5 t (1 t ) 4 ; B 5 2 ( t ) = 10 t 2 (1 t ) 3 ; B 5 3 ( t ) = 10 t 3 (1 t ) 2 ; B 5 4 ( t ) = 5 t 4 (1 t ) and B 5 5 ( t ) = t 5 are the well- kno wn quintic Bernstein polynomials. Since our purpose is to represent the arc with a polynomial curv e with the least possible error , it is not substantial for the errors to tak e place at the endpoints or else where; it is significant to ensure that this anno yance is as lo w as concei v able no matter where the error occurs. Our approach considers lessen the wrongdoing o v er all of the se gment [0 ; 1] . T o e xplore the B ´ ezier form approximation of a circular a rc, a careful selection of locations of the B ´ ezier points should be well-done. These locations are substantial to earn the con v enient curv e that redeems the approximation conditions. Based on the symm etry property of the circle, the right choice for the be ginning control point p 0 should obe y the follo wing form: p 0 = ( 0 cos( ) ; 0 sin( )) , where v alues of 0 and 0 could b ut should not be the same. Similarly , for symmetry reasoning, the v alid option for the end control point p 5 is p 5 = ( 0 cos( ) ; 0 sin( )) . Set p 1 = ( a 1 ; b 1 ) , then the point p 4 has to be selected to satisfy the form p 4 = ( a 1 ; b 1 ) . Set the point p 2 = ( a 2 ; b 2 ) , then the point p 3 has to be selected to satisfy the form p 3 = ( a 2 ; b 2 ) . Using the substitutions a 0 = 0 cos( ) ; b 0 = 0 sin( ) , then the con v enient choices for the B ´ ezier points ha v e to be, see Figure 2, p 0 = a 0 b 0 ; p 1 = a 1 b 1 ; p 2 = a 2 b 2 ; p 3 = a 2 b 2 ; p 4 = a 1 b 1 ; p 5 = a 0 b 0 : (5) It will be apparent that there are more than one solution; the consonant solution of best approximation be gins in the second quadrant and ends in the fourth quadrant counter clockwise. Therefore, in order to ha v e the B ´ ezier curv e p be gin in the second quadrant, go counter clockwise through fourth, third, first, second, and ends in the fourth quadrant as the circular arc c , the follo wing stipulations should be satisfied: a 0 ; a 1 ; b 1 ; b 2 < 0 ; a 2 ; b 0 > 0 : (6) Emplo y the B ´ ezier points in (5) in the B ´ ezier curv e p ( t ) in (4) to obtain: p ( t ) = x ( t ) y ( t ) = a 0 B 5 0 ( t ) + B 5 5 ( t ) + a 1 B 5 1 ( t ) + B 5 4 ( t ) + a 2 B 5 2 ( t ) + B 5 3 b 0 B 5 0 ( t ) B 5 5 ( t ) + b 1 B 5 1 ( t ) B 5 4 ( t ) + b 2 B 5 2 ( t ) B 5 3 ( t ) ; 0 t 1 : (7) The B ´ ezier curv e is settled by the 6 parameters a 0 ; a 1 ; a 2 ; b 0 ; b 1 ; b 2 [12]. These parameters are hired to get the best uni form approximation. W e w ant to impose the conditions on the polynomial curv e p ; the polynomials x ( t ) and y ( t ) are substituted into e ( t ) . This leads to a polynomail of de gree 10 that is solv ed using a computer algebra system. These proceedings are demonstrated in the ne xt section. 3. RESUL TS AND AN AL YSIS The v alues of a 0 ; a 1 ; a 2 ; b 0 ; b 1 ; b 2 that satisfy the conditions of the approximation problem are speci- fied numerically and rounded fittingly in the follo wing theorem. Theor em 1: The B ´ ezier curv e (7) together with the B ´ ezier points in (5) and the v alues of the parameters a 0 ; a 1 ; a 2 ; b 0 ; b 1 , and b 2 gi v en by a 0 = 0 : 978179455549407 ; a 1 = 1 : 338058000836784 ; a 2 = 2 : 365283682287911 ; (8) b 0 = 0 : 21241016393227463 ; b 1 = 1 : 6287837424896061 ; b 2 = 2 : 4356328876380307 (9) achie v es the follo wing three conditions: p minimizes the uniform norm of the error function max t 2 [0 ; 1] j e ( t ) j and approximates c with order 10 , and the error function e ( t ) equioscillates 11 times in [0 ; 1] . The best quintic c hebyshe v appr oximation of ... (Abedallah Rababah) Evaluation Warning : The document was created with Spire.PDF for Python.
3782 r ISSN: 2088-8708 The error functions fulfill: 1 2 9 e ( t ) 1 2 9 ; 1 2 9 (2 ) E ( t ) 1 2 9 (2 + ) ; where = max 0 t 1 j E ( t ) j 2 10 ; 8 t 2 [0 ; 1] : (10) Pr oof: W e be gin by considering the polynomials x ( t ) and y ( t ) in equation (7) and substituting them into the error function e ( t ) in (2). Disposition the phrase and performing se v eral simplifications gi v es the follo wing equation: e ( t ) = 4 b 2 0 40 b 0 b 1 + 100 b 2 1 + 80 b 0 b 2 400 b 1 b 2 + 400 b 2 2 t 10 + 20 b 2 0 + 200 b 0 b 1 500 b 2 1 400 b 0 b 2 + 2000 b 1 b 2 2000 b 2 2 t 9 + 25 a 2 0 + 150 a 0 a 1 + 225 a 2 1 100 a 0 a 2 300 a 1 a 2 + 100 a 2 2 + 65 b 2 0 570 b 0 b 1 + 1225 b 2 1 + 1060 b 0 b 2 4500 b 1 b 2 + 4100 b 2 2 t 8 + 100 a 2 0 600 a 0 a 1 900 a 2 1 + 400 a 0 a 2 + 1200 a 1 a 2 400 a 2 2 140 b 2 0 + 1080 b 0 b 1 1900 b 2 1 1840 b 0 b 2 + 6000 b 1 b 2 4400 b 2 2 t 7 + 200 a 2 0 + 1100 a 0 a 1 + 1500 a 2 1 700 a 0 a 2 1900 a 1 a 2 + 600 a 2 2 + 220 b 2 0 1420 b 0 b 1 + 2000 b 2 1 + 2100 b 0 b 2 5100 b 1 b 2 + 2600 b 2 2 t 6 + 250 a 2 0 1200 a 0 a 1 1350 a 2 1 + 700 a 0 a 2 + 1500 a 1 a 2 400 a 2 2 254 b 2 0 + 1320 b 0 b 1 1450 b 2 1 1540 b 0 b 2 + 2700 b 1 b 2 800 b 2 2 t 5 + 210 a 2 0 + 830 a 0 a 1 + 700 a 2 1 420 a 0 a 2 600 a 1 a 2 + 100 a 2 2 + 210 b 2 0 850 b 0 b 1 + 700 b 2 1 + 700 b 0 b 2 800 b 1 b 2 + 100 b 2 2 t 4 + 120 a 2 0 360 a 0 a 1 200 a 2 1 + 140 a 0 a 2 + 100 a 1 a 2 120 b 2 0 + 360 b 0 b 1 200 b 2 1 180 b 0 b 2 + 100 b 1 b 2 ) t 3 + 45 a 2 0 + 90 a 0 a 1 + 25 a 2 1 20 a 0 a 2 + 45 b 2 0 90 b 0 b 1 + 25 b 2 1 + 20 b 0 b 2 t 2 + 10 a 2 0 10 a 0 a 1 10 b 2 0 + 10 b 0 b 1 t + ( a 2 0 + b 2 0 1) : The approximation conditions are satisfied if the error function is equalized with the polynomial of least de viation among all monic polynomials of de gree 10 . So, the last equation which e x emplifies the error function has to be equalized with the Chebys he v polynomial of first kind of de gree 10 , ~ T 10 (2 t 1) = 512 . W e kno w that ~ T 10 ( u ) = cos(10 arccos( u )) ; u 2 [ 1 ; 1] is the unique monic polynomial of de gree 10 that has the least de viation. It is gi v en by equation (3), see [11]. Comparing the coef ficients of equal po wers of both sides and using the utilities of the computer algebra system in Mathematica, the solution that fulfills the conditions in (6) is established. Unfortunately , the solution is a collection of length y fractions and radicals that is impractical to write do wn the v alues of the parameters in this paper , so, we write them in decimal forms in equat ions (8) and (9). This sho ws that p fulfills the three conditions of the approximation problem. T o pro v e the error formula for E ( t ) , the relation to e ( t ) is established. The error function e ( t ) minimized is link ed to the radial error E ( t ) by the formulation: e ( t ) = x 2 ( t ) + y 2 ( t ) 1 = ( p x 2 ( t ) + y 2 ( t ) + 1) ( p x 2 ( t ) + y 2 ( t ) 1) = (2 + E ( t )) E ( t ) : Thus E ( t ) = e ( t ) 2 + E ( t ) : Substituting the bounds for e ( t ) gi v es 1 2 9 (2 ) E ( t ) 1 2 9 (2 + ) ; where = max 0 t 1 j E ( t ) j 2 10 ; t 2 [0 ; 1] : This completes the proof of Theorem 1. Int J Elec & Comp Eng, V ol. 9, No. 5, October 2019 : 3779 – 3785 Evaluation Warning : The document was created with Spire.PDF for Python.
Int J Elec & Comp Eng ISSN: 2088-8708 r 3783 The circular arc and the approximating B ´ ezier curv e are plotted in Figure 2 . The resulting error between the curv e and the approximation is not identified by the human e ye which is clear from figure of the corresponding error plotted in Figure 3 . - q P 0 P 5 P 1 P 2 P 3 P 4 1 Figure 2. Circular arc and its quintic B ´ ezier curv e in Theorem 1 . 0.2 0.4 0.6 0.8 1.0 - 0.0010 - 0.0005 0.0005 0.0010 Figure 3. Radial Error of the quintic B ´ ezier curv e in Theorem 1 . The resulting B ´ ezier curv e re v eals a brilliant positioning of the B ´ ezier points to embrace more than a whole circle whilst possessing the Chebyshe v error . W e could not foresee a quintic polynomial to approximate more than the full circle further accurately than this approximation. 4. CONCLUSION In this article, quintic approximation of the circle is established. The approximation fulfills e xtremely conclusi v e circumstances. Unlik e the classical approximation that a w ards order of approximation of 6 , this approximation has order of approximation of 10 ; this is an superb acquisition. Moreo v er , in the significance of the Chebyshe v norm, this approximation is the best and can not be impro v ed. The error function equioscillates 11 times rather than 7 . The numerical e xamples re v eal ho w ef ficient this method is. The approximation intersects the circular arc 10 times with maximum error 2 9 and thus outperforming an y other approximation. Further research and in v estig ations can be accomplished by considering the follo wing issues: (a) Finding the quintic best polynomial approximation for other curv es that are widely used in the computer’ s applications lik e the h yperbolas and the spirals. (b) Using the qui ntic best polynomial approximation in this paper to find the of fset curv e approximations of the B ´ ezier curv es. (c) Finding the quintic best polynomial approximation with geometric conditions, G 1 - and G 2 -conditions at the end points. The best quintic c hebyshe v appr oximation of ... (Abedallah Rababah) Evaluation Warning : The document was created with Spire.PDF for Python.
3784 r ISSN: 2088-8708 (d) Applying the method in this paper to approximate the bit error rate (BER) e xpressions of the dif ferential M-PSK modulation [14]. (e) Finding the quintic best polynomial approximation to shorter arcs of the circle that has an error reduced according to the length of the arc relati v e to the gi v en approximation to more than the whole circle. (f) Using the res ults in this paper to obtain the optimal delays between consecuti v e requests (DCR) in LoW - P AN border routers to limit request send rates [15]. (g) Making a v alid conjecture similar to the conjecture in [16, 17] that impro v es the results of Chebyshe v’ s and Borel’ s theorems to approximate a curv e with 2 n + 1 equioscillations rather than for functions with n + 2 equioscillations. This is a no v el break through and treasure tro v e in the field of approximation theory; ho we v er , this is a challenging issue and our today’ s kno wledge is not rich enough to tackle it. A CKNO WLEDGEMENT The author o wes thanks for the re vie wers for in v aluable suggestions to impro v e an earlier v ersion of this paper . This research w as funded by Jordan Uni v ersity of Science and T echnology . REFERENCES [1] K. H ¨ ollig, J. H ¨ orner: ”Approximation and Modeling with B-Splines, ” SIAM, T itles in Applied Mathe- matics , v ol. 132, 2013. [2] Y . J. Ahn and C. Hof fmann, ”Circle approximation using LN B ´ ezier curv es of e v en de gree and its ap- plication, ” Journal of Mathematical Analysis and Applications , v ol. 410 Issue 1, pp. 257–266, February 2014. [3] P . B ´ ezier , ”The mathematical basis of the UNISURF CAD system, ” Butterw orth-Heinemann Ne wton , MA, USA, ISBN 0-408-22175-5, 1986. [4] J. Blinn, ”Ho w man y w ays can you dra w a circle?, ” Computer Graphics and Applications, IEEE , v ol. 7, Issue 8, pp. 39–44, 1987. [5] C. de Boor ., et al., ”High ac curac y geometric Hermite interpolation, ” Computer Aided Geometric Design , v ol. 4, pp. 269–278, 1988. [6] S. W . Kim and Y . J. Ahn, ”Circle approximation by quartic G 2 spline using alternation of error function, ” J. KSIAM , v ol. 17, Issue 5, pp. 171–179, 2013. [7] A. Rababah, ”The Best Uniform Quadratic Approximation of Circular Arcs with High Accurac y , ” Open Mathematics , v ol. 14, pp. 118–127, 2016. DOI: https://doi.or g/10.1515/math-2016-0012 [8] A. Rababah, ”The best uniform quintic approximation of circular arcs with high accurac y , ” 14th Inter - national Conference of Numerical Analysis and Applied Mathematics , Rhodes, Greece, AIP Conference Proceedings v ol. 1863, Issue 1, 060005, 2017. https://doi.or g/10.1063/1.4992219. [9] A. Rababah, ”The best uniform cubic approximation of circular arcs with high accurac y , ” Communica- tions in Mathematics and Applications , v ol. 7, Issue 1, pp. 37–46, 2016. [10] L. F ang, ”Circular arc approximation by quintic polynomial curv es, ” Computer Aided Geometric Design , v ol. 15, Issue 8, pp. 843-861, 1998. [11] J. Rice, ”The approximation of functions, ” 1: linear theory . , Addison-W esle y , 1964. [12] A. Rababah, ”Best se xtic approximation of circular arcs with thirteen equioscillations, ” Pro- ceedings of the Jangjeon Mathematical Society , v ol. 21, Issue 1, pp. 111–123, 2018. DOI: http://doi.or g/10.17777/pjms2018.21.1.111 [13] G. F arin, ”Curv es and Surf aces for Computer Aided Geometric Design, ” Academic Press , Boston, 1997. [14] S. Alabed, ”Performance Analysis of Dif ferential Beamforming in Decentralized Netw orks, ” Interna- tional Journal of Electrical and Computer Engineering (IJECE) , v ol. 8 Issue 3, pp. 1692-1700, 2018. DOI: http://doi.or g/10.11591/ijece.v8i3.pp1692-1700 [15] C. Suw annapong and C. Khunboa, ”An Approximation Delay betwee n Consecuti v e Requests for Con- gestion Control in Unicast CoAP-based Group Communication, ” International Journal of Electrical and Computer Engineering (IJECE) , v ol. 9, Issue 3, June 2019. DOI: http://doi.or g/10.11591/ijece.v9i3. [16] A. Rababah, ”Approximation v on K urv en mit Polynomen und Splines, ” Ph. Dissertation, Stuttg art Uni- v ersit ¨ at , W est German y , 1992. [17] A. Rababah, ”T aylor theorem for planar curv es, ” Proceedings of the American Mathematical Society , v ol. 119, Issue 3, pp. 803–810, 1993. Int J Elec & Comp Eng, V ol. 9, No. 5, October 2019 : 3779 – 3785 Evaluation Warning : The document was created with Spire.PDF for Python.
Int J Elec & Comp Eng ISSN: 2088-8708 r 3785 BIOGRAPHY OF A UTHORS Abedallah Rababah is a professor of Mathematics at Jordan Uni v ersity of Science and T ech- nology . He is w orking in the field of Computer Aided Geometric Design, abbre viated CA GD. In particular , his research is on de gree raising and reduction of B ´ ezier curv es and s urf aces with geometric boundary conditions, Bernstein polynomials, and their duality . He is kno wn for his research in describing approximation methods that significantly impro v e the standard rates obtained by classical (local T aylor , Hermite) methods. He pro v ed the follo wing conjec- ture for a particular set of curv es of nonzero measure: Conjecture: A smooth re gular planar curv e can, in general, be approximated by a polynomial curv e of de gree n with order 2n. The method e xploited the freedom in the choice of the parametrization and achie v ed the order 4n/3, rather than n + 1. Generalizations were also pro v ed for space curv es. Professor Rababah is also doing research in the fields of classical approximation theory , orthogonal polynomials, Jacobi-weighted orthogonal polynomials on triangular domains, and best uniform approxi- mations. Since 1992, He has been teaching at German, Jordania n, American, Canadian, and Emirates’ uni v ersities. He is acti v e in the editorial boards of man y journals in mathematics and computer science. Further info can be found on his homepage at ResearchGate: https://www .researchg ate.net/profile/Abedallah Rababah or at http://www .just.edu.jo/eportfolio/P ages/Def ault.aspx?email=rababah The best quintic c hebyshe v appr oximation of ... (Abedallah Rababah) Evaluation Warning : The document was created with Spire.PDF for Python.