Luo Yin etc:Pedestrian Dead Reckoning Device Design BasednSTM32 projected onto the xy plane after tilt compensation7] ssind as Hx Hy,the heading angle Aof pedestrian can be expressed by formula(4): 男=%+cosA H=M sin+M sin (1) 3.2 Heading angle calculation H,=M,sin 0,sin 0,+M,cos 0-M.sin 0;cos The pitch(represented by0l and the tilt angle (represented by02)of the sensor module calculated by the Ax,Ay,Az measured by the three-dimensional (4) The Mx、My、Mz is the three-axis magnetic field component after ellipsoid correction8. 3.3 Count of the number of step and stride estimate Since the three-dimensional sensor module is placed on the waist of pedestrian the accelerometer can a=acal丁E+E A detec e of pedestrian,the vertical acceleration n threshold The Ax,Ay,Az in the formula(2)is acquired by the determination method is used to count the number of triaxial acceleration values corrected through least step.Meanwhile,the stride frequency(Hz)and stride squares method [61 Since the sensor module is placed length(m)of pedestrian has linear relationship and can on the waist of pedestrian.It is inevitably introduce be used the following mode]toestimate: ibration isturbance when the pedestrian is walking. 0.4375. ≤1.35 and result in pitch and tilt angle solving error,a S- 0.45F-0.17,135<F<2.45 complementary filtering algorithm is used to integrate 0.9325 2.45≤f<ao (5) with the data produced by the gyroscope to reduce Where S is the real-time stride length of pedestrian interference of solving error caused by vibration let F is pedestrian's real time walking frequency.To count e the three-axis data of the gyro scope after the real time walking frequeney in thedat performing filtering complementary algorithm as Gx terminal can determine the real time stride lengthof Gy,Gz.and three direction acceleration data afte pedestrian,and reduce the travel distance statistical fusion as Ax',Ay'.Az'The weight of three directions error. acceleration as PAx、PAy、PAz.the weight of hrce-axis gyroscope data as PGx、PGy、PGz,thc 4TEST RESULT AND ANALYSIS A=(A,×P+G,×P)MP旺+P) Field test result is shown in Figure6,the test site is the school internal standard athletic field.the athletic A.=(A.xP:+G,xP)/(P:+P) field included two straight lane,one is set form the west to the east,and the other is set from the east to A=(A×P+G,xP)P+P) the west The fifth is chosen nd the (3) lane walking length is 430m.the actual number of steps is By reducing the weight of the acceleration values 560.The number of steps measured by dead reckoning and improving the weight of three-axis data of is 587,the measured walking distance is 428.5m.The relative statistical error of the number of step is 4 8% ula(3)we car ror of walking di stance is less than I%.Compared with the actual route.the combine with three-axis magnetic field components maximum deviation is 5m,appears in the straight lane Mx、My、Mz measured by the electronic which is set from the east to the west,the deviation compass,suppose the component of the magnetic field interval length is 85m.the heading angle measuredLuo Yin etc.: Pedestrian Dead Reckoning Device Design Based on STM32 9 / 0 0 sin n tT t i x x SA = = = + ∑ ∑ = = = + n t T i yt x S A / 0 0 cos （1） 3.2 Heading angle calculation The pitch(represented byθ1 ) and the tilt angle (represented byθ2) of the sensor module calculated by the Ax, Ay, Az measured by the three-dimensional accelerometer can be expressed as[5]: arctan( ) 2 2 1 y z x A A A + θ = arctan( ) 2 2 2 x z y A A A + θ = (2) The Ax、Ay、Az in the formula(2) is acquired by the triaxial acceleration values corrected through least squares method [6].Since the sensor module is placed on the waist of pedestrian.It is inevitably introduce vibration disturbance when the pedestrian is walking, and result in pitch and tilt angle solving error,a complementary filtering algorithm is used to integrate with the data produced by the gyroscope to reduce interference of solving error caused by vibration. Let us suppose the three-axis data of the gyroscope after performing filtering complementary algorithm as Gx、 Gy、Gz,and three direction acceleration data after fusion as Ax’、Ay’、Az’ The weight of three directions acceleration as PAx 、 PAy 、 PAz,the weight of three-axis gyroscope data as PGx、PGy、PGz,the following can be expressed as formula(3): ( )/( ) ' x G x A x x G x Ax = Ax × PA + G × P P + P ( )/( ) ' y G y A y y G y Ay = Ay × PA + G × P P + P ( )/( ) ' z G z A z z G z Az = Az × PA + G × P P + P （3） By reducing the weight of the acceleration values and improving the weight of three-axis data of gyroscope can achieve satisfied filtering effect.Put the processed acceleration values into formula(3), we can obtain the de-noised pitch and tilt angle.Let us combine with three-axis magnetic field components Mx 、 My 、 Mz measured by the electronic compass,suppose the component of the magnetic field projected onto the xy plane after tilt compensation[7] as Hx、Hy,the heading angle A of pedestrian can be expressed by formula(4): 1 1 Hx = M x sinθ + M z sinθ 2 1 2 2 1 H y = M x sin θ sin θ + M y cos θ − M z sin θ cos θ arctan( ) y x H H A = （4） The Mx、My、Mz is the three-axis magnetic field component after ellipsoid correction[8]. 3.3 Count of the number of step and stride estimate Since the three-dimensional sensor module is placed on the waist of pedestrian, the accelerometer can detect vertical acceleration changes in walking cycles of pedestrian,the vertical acceleration threshold determination method is used to count the number of step. Meanwhile, the stride frequency(Hz) and stride length(m) of pedestrian has linear relationship and can be used the following model[9] to estimate: 0.4375， 0<F≤1.35 S= 0.45F-0.17， 1.35<F<2.45 0.9325 2.45≤F<∞ （5） Where S is the real-time stride length of pedestrian, F is pedestrian’s real time walking frequency. To count the real time walking frequency in the data processing terminal can determine the real time stride length of pedestrian, and reduce the travel distance statistical error. 4 TEST RESULT AND ANALYSIS Field test result is shown in Figure 6, the test site is the school internal standard athletic field, the athletic field included two straight lane, one is set form the west to the east, and the other is set from the east to the west.The fifth lane is chosen and the actual walking length is 430m, the actual number of steps is 560 .The number of steps measured by dead reckoning is 587, the measured walking distance is 428.5m.The relative statistical error of the number of step is 4.8% and the relative statistical error of walking distance is less than 1 %.Compared with the actual route, the maximum deviation is 5m, appears in the straight lane which is set from the east to the west, the deviation interval length is 85m, the heading angle measured