Apparatus and method for identifying and analyzing the free flight dynamics of a body

• US 9,140,717 B2
• Filed: 09/20/2011
• Issued: 09/22/2015
• Est. Priority Date: 09/20/2011
• Status: Active Grant

• Current Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Original Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Inventors: Perkins, Noel, King, Kevin, Doss, Ryan
• Primary Examiner(s): HWANG, TIMOTHY
• Application Number:
  US13/236,725
• Publication Number:
  US 20130073247A1
• Time in Patent Office: 1,463 Days
• Field of Search: 702/141, 702/145, 702/153
• US Class Current: 1/1
• CPC Class Codes: A63B 2024/0034 during flight
• CPC Class Codes: A63B 2220/40 Acceleration
• CPC Class Codes: G01C 21/185 for gravity
• CPC Class Codes: G01P 3/44 for measuring angular speed G01P3/56 takes precedence

Abstract

An apparatus for analyzing free flight of a body including an inertial measurement unit having at least one accelerometer continuously measuring three orthogonal axes of acceleration and outputting data representative thereof and a processing unit operably receiving the data and determining three components of an angular velocity of the body during free flight.

Claims

1. An apparatus for analyzing free flight of a body of sports equipment, said apparatus comprising:

an inertial measurement unit having no more than one accelerometer continuously measuring no more than three acceleration signals representing no more than three orthogonal axes of acceleration and outputting data representative thereof; and

a processing unit operably receiving said data, said processing unit algebraically computing three components of an angular velocity of the body of sports equipment from said data representative of said measured three orthogonal axes of acceleration.

4. The apparatus according to claim 1 wherein said processing unit compensates for errors in said data by comparing a calculated acceleration of a mass center of the body of sports equipment to a predetermined acceleration due to gravity.

2. An apparatus for analyzing free flight of a body of sports equipment, said apparatus comprising:

an inertial measurement unit having one accelerometer continuously measuring three orthogonal axes of acceleration and outputting data representative thereof; and

a processing unit operably receiving said data, said processing unit computing three components of an angular velocity of the body of sports equipment from said data representative of said measured three orthogonal axes of acceleration,

wherein said processing unit calculates said angular velocity (ω

_x, ω

_y, ω

_z) of the body of sports equipment based on simultaneous solution of the equations

a_x=−

x(ω

_y²+ω

_z²)+yω

_xω

_y+zω

_xω

_z

a_y=−

y(ω

_z²+ω

_x²)+zω

_yω

_z+xω

_yω

_x

a_z=−

z(ω

_x²+ω

_y²)+xω

_zω

_x+yω

_zω

_y

wherein x, y, z is the position of the mass center of the body of sports equipment relative to the position of said accelerometer and a_x, a_y, a_z is said measured three orthogonal axes of acceleration from said inertial measurement unit.

3. An apparatus for analyzing free flight of a body of sports equipment, said apparatus comprising:

an inertial measurement unit having one accelerometer continuously measuring three orthogonal axes of acceleration and outputting data representative thereof; and

a processing unit operably receiving said data, said processing unit computing three components of an angular velocity of the body of sports equipment from said data representative of said measured three orthogonal axes of acceleration,

wherein said processing unit calculates said angular velocity (ω

_x, ω

_y, ω

_z) of the body of sports equipment based on simultaneous solution of the measured output of the at least one accelerometer ({right arrow over (a)}_measured)

{right arrow over (a)}_measured=[−

I_c<sup>−

1</sup>({right arrow over (ω

)}×

I_c{right arrow over (ω

)})]×

{right arrow over (r)}_p/c+{right arrow over (ω

)}×

({right arrow over (ω

)}×

{right arrow over (r)}_p/c)

wherein I_c is the inertia tensor about principal axes (x, y, z) through the mass center, c;

{right arrow over (ω

)} is the angular velocity vector;

{right arrow over (r)}_p/c is the position vector of said accelerometer measured from the mass center, c.

5. An apparatus for analyzing free flight of a body of sports equipment, said apparatus comprising:

an inertial measurement unit having only one accelerometer measuring acceleration using no more than three acceleration signals along no more than three rigid body degrees of freedom and outputting data representative thereof; and

a processing unit operably receiving said data, said processing unit outputting six rigid body degrees of freedom of the body of sports equipment during free flight in response to algebraically calculating angular velocity based on said data representative of said acceleration measured along said three rigid body degrees of freedom.

6. The apparatus according to claim 5 wherein said accelerometer comprises a three-axis accelerometer.