Avalable onlne at www.scencedrect.com Proceda Engneerng 13 (211) 17 22 5 th Asa-Pacfc Congress on Sports Technology (APCST) A proposal for the moton analyss method of skng turn by measurement of orentaton and gldng trajectory K Hrose *, H Dok Graduate School of Engneerng and Resource Scence, Akta Unversty, Tegata Gakuen-mach, Akta-sh, Akta, Japan Receved 18 March 211; revsed 9 May 211; accepted 11 May 211 Abstract Ths paper proposes the moton analyss method on skng turn by the measurement system of orentaton and gldng trajectory. The orentaton measurement system that conssts of nertal and magnetc feld sensor measures angular velocty, acceleraton and magnetc feld, on the other hand the gldng trajectory measurement system that conssts of the GPS recever measures lattude, longtude and alttude. The 3D orentaton of sker s body segments and the 3D gldng trajectory on skng turn are estmated usng sensor fuson and the nformaton measured by the orentaton measurement systems and the gldng trajectory measurement system attached to sker. The 3D gldng velocty on skng turn s estmated wth the 3D gldng trajectory. The measurement experment has been conducted by the sker attached the measurement systems on an actual snow feld. The jont angle has ndcated the gldng form n skddng and carvng turn, the gldng trajectory has vsualzed clearly the dfference n movng dstance between skddng turn and carvng turn. Furthermore, the gldng velocty relatve to sker s coordnate has perceved the dfferent perod and the effect of sde skddng on these two turns. The expermental results have ndcated quanttatvely the everchangng state of sker. The major features of skng turn can be analyzed by the proposed method, whch can use as an effectve method for suggestng more deal turnng form, the skll ratng, the preventon of dsorder and njury from skng. 211 Publshed by Elsever Ltd. Open access under CC BY-NC-ND lcense. Selecton and peer-revew under responsblty of RMIT Unversty Keywords: Sk; moton analyss; jont angle; gldng trajectory; gldng velocty * Correspondng author. Tel.: +81-18-889-2341; fax: +81-18-837-45. E-mal address: hrose@gpc.akta-u.ac.jp. 1877 758 211 Publshed by Elsever Ltd. Open access under CC BY-NC-ND lcense. do:1.116/j.proeng.211.5.45
18 K Hrose and H Dok / Proceda Engneerng 13 (211) 17 22 1. Introducton Skng has progressed wth mprovement of equpment and technque. There are several studes on skng such as development of sk robot [1], smulaton of skng turn [2], characterstcs analyss of sk [3] and the moton analyss of sker [4]. It s mportant to analyze the moton of sker gldng on an actual snow feld to resolve the mechansm of skng turn. However, t s dffcult to measure physcal exerton due to the severe expermental surroundng such as the outsde snow condtons and the weather on the mountan. Thus, few studes have analyzed skng turn quanttatvely. Studes on the moton measurement and analyss are the moton measurement of sker by potentometer and stran gage [5], the moton analyss of sker by 3D magnetc postonng system and 6-axs force sensor [6] and bomechancal analyss of sk racng by nertal measurement unts and GPS recever [7]. The method by nertal sensor, magnetc sensor and GPS recever s effectve the measurement of wde range such as snow sports. Thus, t s necessary to develop the analyss method by these measurement systems. In our prevous studes, we have proposed the measurement method of 3D orentaton, 3D gldng trajectory and 3D gldng velocty on skng turn [8], [9]. Ths paper proposes the moton analyss method usng 3D orentaton and 3D gldng velocty by nertal sensor, magnetc feld sensor and GPS recever. Furthermore, we conduct the experments by sker gldng on an actual snow feld, and we ndcate the effectveness of proposed analyss method. 2. Measurement System 2.1. 3D orentaton measurement The orentaton measurement system shows n Fgure 1. Ths system that conssts of gyro sensor (Analog Devces, ADIS1611), acceleraton sensor (Htach metals, H3CD), and magnetc feld sensor (Ach steel, AMI 34) measures 3-axs angular velocty, 3-axs acceleraton and 3-axs magnetc feld. The sze of ths system s 45 65 25mm, and the weght s 6g. 2.2. Gldng trajectory measurement The 3D gldng trajectory of skng turn s measured by GPS recever and the orentaton measurement system. The GPS recever (FV-M8, San Jose Technology) s shown n Fgure 2. The GPS recever measures lattude, longtude and alttude. The nformaton of GPS recever s translated to the 3D poston (dstance from startng poston). The nformaton of the orentaton measurement system s used to nterpolate the 3D poston of the GPS recever. Fg. 1. Orentaton measurement system Fg. 2. GPS recever
K Hrose and H Dok / Proceda Engneerng 13 (211) 17 22 19 3. Theory 3.1. Jont angle The 3D orentaton s estmated by the sensor fuson usng an extended Kalman flter. The nonlnear state equaton and the nonlnear measurement equaton n the extended Kalman flter consst of the nformaton obtaned from two orentaton measurement systems. Ths method compensates the errors caused by drft and dynamc acceleraton. The block dagram of sensor fuson for orentaton measurement s shown n Fgure 3, where 1x, 1y, 1z are gyro sensor output (angular velocty) n sensor 1, 2x, 2y, 2z are gyro sensor output n sensor 2, a 1x, a 1y, a 1z are acceleraton sensor output n sensor 1, a 2x, a 2y, a 2z are acceleraton sensor output n sensor 2, m 1x, m 1y, m 1z are magnetc feld sensor output n sensor 1, m 2x, m 2y, m 2z are magnetc feld sensor output n sensor 2, 1m, 2m are Yaw-angle obtaned by compensatng the nclnaton error from magnetc feld, 1x, 1y, 1z are 3D orentaton (roll ptch yaw angle) n sensor 1 and 2x, 2y, 2z are 3D orentaton (roll ptch yaw angle) n sensor 2, respectvely. Fg. 3. Block dagram of sensor fuson for orentaton measurement The rotatonal matrx n relatve coordnate s calculated from the 3D orentaton (roll ptch yaw angle) by equatons (1) and (2). The jont angle s calculated from the rotatonal matrx n relatve coordnate by nverse knematcs. cosψ snψ cosθ snθ 1 R ( ) ( ) ( ) = R ψ R θ R φ = snψ cosψ 1 cosφ snφ (1) 1 snθ cosθ snφ cosφ 1 1 T ( R 1) R = ( R 1) R R (2) = 3.2. 3D gldng trajectory and velocty The 3D gldng trajectory and velocty are estmated by sensor fuson usng a Kalman flter. The state equaton and the measurement equaton n a Kalman flter conssts of acceleraton translated to global coordnate and GPS recever output. The block dagram of sensor fuson for measurement of gldng
2 K Hrose and H Dok / Proceda Engneerng 13 (211) 17 22 trajectory and velocty s shown n Fgure 4. The 3D gldng velocty s translated to sker s coordnate by equaton (3) for moton analyss of skng turn. Where A x, A y, A z are acceleraton sensor output, g s gravty acceleraton, A x, A y, A z are acceleraton n global coordnate, P xgps, P ygps, P ygps, are 3D poston obtaned by GPS recever, P x, P y, P z are 3D gldng trajectory, V x, V y, V z are 3D gldng velocty n global coordnate, and V x, V y, V z are 3D gldng velocty n sker s coordnate, respectvely. V V V x y z = R T V V V x y z (3) Fg. 4. Block dagram of sensor fuson for measurement of gldng trajectory and velocty 4. Experment 4.1. Expermental condton We have conducted the experment by sker attached the measurement systems. The orentaton measurement systems are attached to upper body, lumber, femur, lower thgh, foot parts, and the gldng trajectory measurement system s attached on head. The settng poston of the measurement systems are shown n Fgure 5. Fg. 5. Settng poston of the measurement system
K Hrose and H Dok / Proceda Engneerng 13 (211) 17 22 21 The experment has been conducted by sker attachng the measurement systems on an actual snow feld. Sker has conducted carvng turn and skddng turn. In the experment, the samplng frequency of the orentaton measurement system s 1Hz, and the samplng frequency of GPS recever s 1Hz, and the measurement tme s 3sec. 4.2. Expermental results The results of the rght hp jont angles are shown n Fgure 6. The flexon angle of rght hp jont n carvng turn s hgher than one n skddng turn. The result of the gldng trajectory obtaned by sensor fuson and the 3D poston obtaned by the GPS recever are shown n Fgure 7. The gldng trajectory has ndcated the result nterpolatng the 3D poston obtaned by the GPS recever. The gldng veloctes relatve to sker s coordnate are shown n Fgure 8. X-axs velocty ndcates the speed of transfer drecton, Y-axs velocty ndcates the lateral drecton velocty, and Z-axs velocty ndcates the rse and fall drecton velocty. In the result of skddng turn, X-axs velocty s decreased when absolute value of Y-axs velocty s ncreased. The result ndcates the decrease of the speed of transfer drecton because of sde skddng of sk. In the result of carvng turn, X-axs velocty s not decreased than one n skddng turn. Ths result ndcates that the effect of sde skddng on the speed of transfer drecton n carvng turn s less than one n skddng turn. Fg. 6. Rght hp jont angle (a) Carvng turn (b) Skddng turn Fg. 7. Gldng trajectory
22 K Hrose and H Dok / Proceda Engneerng 13 (211) 17 22 Fg. 8. Gldng velocty n sker s coordnate (a) Carvng turn (b) Skddng turn 5. Concluson In ths study, we proposed an analyss method of skng turn by the orentaton and the gldng trajectory measurement systems. The jont angle s measured by the orentaton measurement system, and the gldng trajectory and velocty s measured by the orentaton and the gldng trajectory measurement systems. The results of experment by sker gldng on an actual snow feld ndcated quanttatvely the jont angle, the gldng trajectory and velocty both n skddng turn and n carvng turn. The major features of skng turn can be analyzed by the proposed method, whch can use as an effectve method for suggestng more deal turnng form, the skll ratng, the preventon of dsorder and njury from skng. References [1] T. Yoneyama, H. Kagawa, M. Unemoto, T. Izuka, N. W. Scott, A Sk robot system for qualtatve modelng of the carved turn, Sports Engneerng, 29, 11, 131-141. [2] P. Federolf, M. Roos, A. Luth and J. Dual, Fnte element smulaton of the sk-snow nteracton of an alpne sk n a carved turn, Sports Engneerng, 21, 12, 123-133. [3] A. Subc, P. Clfton, J. Beneyto-Ferre, A. Leflohc, Y. Sato, V. Pchon, Investgaton of snowboard stffness and camber characterstcs for dfferent rdng styles, Sports Engneerng, 29, 11, 93-11. [4] T. Yoneyama, M. Ktabe and K. Osada, Investgaton on the sk-snow nteracton n a carved turn based on the actual measurement, Proceda Engneerng 2, 21, 291-296. [5] T. Yoneyama, H. Kagawa and K. Osada, Measurement of sk snow-pressure profles, Sports Engneerng, 27, 1, 145-156. [6] C. Naga, Y. Sakura, H. Dok and T. Iwam, Studes on the Effect of Wast Movement on the Sk Turn, Journal of Sk Scence, 24, 2-1, 9, (n Japanese). [7] M. Brode, A. Walmsley, W. Page, Fuson moton capture: a prototype system usng nertal measurement unts and GPS for the bomechancal analyss of sk racng, Sports Technology, 28, 1-1, 17-28. [8] K. Hrose, H. Dok, S. Koda, K. Nagasaku, Studes on the dynamc analyss and moton measurement of skng turn usng extended Kalman flter, JEMS, 211, 77-774, 47-48 (n Japanese). [9] K. Hrose, H. Dok, H. Murata, N. Sato, Studes on the moton analyss of skng turn usng orentaton and gldng trajectory measurement, Journal of Sk Scence, 211, 8-1, (n Japanese).