WO2008018810B1 - Body kinetics monitoring system - Google Patents

Abstract

The present invention relates to a sensing system for the monitoring of posture, orientation and movement of a body in a three dimensional space, differentiating among the various stationary states and transient states in what the user can be. Sensing modules are composed by three-axis accelerometers, three-axis magnetometers and interfacing electronics. The device is encapsulated, enabling its use in adverse and harsh environments. The data monitored by the sensing modules are transmitted in real time, by the local communication device, to the central communication device, using a 2.4 GHz RF transceiver. Generic applications derived from the analysis of the monitored data include not only the rectification of a user's incorrect body posture, thereby avoiding injuries, but also the acceleration of the healing process in therapy or the simple monitoring of a user's physical activity. Being compact and encapsulated, this device can be used to monitor and analyze the movement of athletes in physical activity, e.g. a swimmer.

Claims

AMENDED CLAIMS Received by the International Bureau on 23. June.2008 (23.06.08)CLAIMS

1. A system for monitoring posture, orientation and movement of bodies in space and measuring body acceleration comprising sensing modules, processing unit, storage unit and communication unit, comprising a device that applies a method for correction of the vertical component of Earth' s magnetic field and decoupling of linear and gravitational acceleration that comprises the following steps:

defining the gravity field data, g_meas =

r the

magnetic field data, m_meas =

i the previous

measured magnetic field data, Sι_prev =

^m _{pz >} the

previous calculated rotation vector v_prev =

^v _pz and the angle between the previous magnetic and gravitational fiels, α_prev; calculating the absolute value of the measure gravity field using equation one (XI) ;

checking if \g\ = 1 and jumping to the calculation of the pitch {θ) and roll (φ) in case \g\ = 1 or applying extra intermediate steps otherwise;

calculating the normal of the plane defined by the vectors in_prev and m_me3S using equation two (XII) ;

n = (JΠ_X, m_y, m_∑) x (m_px, m_py, m_pz) (XIi; calculating the angle β, which corresponds to the angle between the previous and measured magnetic fields using equation (III) ;

β = K=' ^my> ^mz) ^• (^mpx' ^mpy> m (XIII)

rotating the previous computed rotation vector v_prev over the rotation matrix (XIV) wherein getting the new rotation vector v_new using equation (XV) ;

n u + c ⁿyⁿx^U - ⁿz^S n n u + n_ys

M = ⁿxⁿy^U + n,s n_yu + ⁿzⁿy^U ~ ⁿx^S (XIV) nA^{u ~ n} _y ^s n_yn_zu + n s ⁿl^u + ^c wherein s = sin (β) , c = cos (/3) and u = 1 — cos {β)

vnew = Mvvprev = V. V V (XV)

retrieving the gravitational field by rotating the measured magnetic field data over the rotation matrix (XVI) and using equation (XVII) ;

^Vnx^U + ^{C V}ny^Vn,P ~ ^Ωz^{S V}nz^Vnx^U + ^{V '} ny^S

M = ^Vn*^Vny^U + ^Vnz^{S V}ny^U + ^{C V}nz^Vny^U ~ ^V n_X ^S (XVI )

^Vn_X ^Vnz^{U ~ V}ny^{S V}ny^Vnz^U + ^V nx^S wherein s = sin (α ) , c = cos (α ) and u = 1 - cos (α )

-3 new a prev ^» newx ? newy ^r newz ' (xvii;

calculating the motion acceleration using equation (XVIII) and assuming as the gravity measure field data the calculated gravity field using equation (XIX) ,

motion = (a_x a J - (a_n i ' new yy ^r ' nneewwz ' (xviii ;

aj = (a newx t new ryy ' ' newz ' (XIX)

calculating the pitch [Q) and roll [φ) angles using the equation (I) ;

θ ⁽i:

calculating the correction factors by means of the rotation vector (IV) , which corresponds to the vector product of the gravity and magnetic fields, and the rotation angle (V) , which corresponds to the angle between the gravity and magnetic fields;

v = (α_x,α α_z)x(m_x,m m_z) (IV) π α = —-arc∞s(α^_χiα_Jt).(m_x,m_y,m_z) (V)

applying the correction factors with the rotation matrix (VI) wherein the readings from the magnetic sensors are compensated by equation (VII) ;

V_χU + C ^v _y ^v _x ^u — ^V _z ^S V₂V_xU + V _yS

M_rot = v_xv_yu + v_zs V_yU + c V₂V_yU - V_xS (Vi ;

V_xV₂U - V_yS V^V₂W f V/ V₂ ²U + C wherein s = sin(α) , c = cos(α) and w = l - cos(α) <_t = M_rotm (VII )

compensating of the yaw (φ) angle for roll (φ) and pitch (θ) movements using equation (VIII) being its value determined by equation (III) ;

X_H = m_rot cos θ - m_rot sin θ sin φ - m_rot sin θ cos φ

(VIII )

^YH = ^mro_K ^{COS (}p - ^mr_Ol ^m ψ

(III)

2. A system for monitoring posture, orientation and movement of the human body, according to claim 1, characterized in that one of the sensing modules (reference module) is located in the trunk zone.

3. A system for monitoring posture, orientation and movement of the human body, according to claim 1, characterized in that the sensing modules are located in body areas where the linear acceleration caused by the rotation of the limbs is zero.

4. A system for monitoring posture, orientation and movement of the human body, according to claim 1, characterized in that the sensing modules have power consumption lower to 50 mW, provided by batteries.

5. A system for monitoring posture, orientation and movement of the human body, according to claim 1, characterized in that the sensing modules have compact dimensions and a volume inferior to 5 cm³.

6. A system for monitoring posture, orientation and movement of the human body, according to claim 1, characterized in that the communication unit is composed by a central communication device and one or more local communication devices.

7. A system for monitoring posture, orientation and movement of the human body, according to the preceding claims, characterized in that the sensing modules register their position in relation to Earth' s gravity and magnetic fields and transmit data through the local communication device to the central communication device, providing the posture, orientation and movement of the body.

8. A system for monitoring posture, orientation and movement of the human body, according to claim 6, characterized in that the local communication device sends the monitoring data to the central communication device in real time at a sampling rate between 1 and 50 Hz.

9. A system for monitoring posture, orientation and movement of the human body, according to claim 6, characterized in that the local communication device can be integrated in the sensing modules, allowing direct wireless communication with the central communication device.

10. A system for monitoring posture, orientation and movement of the human body, according to claim 9, characterized in that the wireless communication takes place by radiofrequency (RF) at 2.4 GHz, allowing the connectivity with personal devices (cellular phones, PDAs, laptop computers, etc.).

11. A system for monitoring posture, orientation and movement of the human body, according to claim 1, characterized in that the storage unit stores de monitored data, retransmitting them afterwards to the central communication device in case of transmission failure.

12. A system for monitoring posture, orientation and movement of the human body, according to claim 1, characterized in that the sensing modules and local communication devices are housed in hermetic materials, allowing their operation in adverse or harsh environments.

13. A system for monitoring posture, orientation and movement of the human body, according to the preceding claims, characterized in that the reference module, the sensing modules and the local communication device can be embodied in a textile basis.