Real-time measurements for establishing database of sporting apparatus motion and impact parameters

Abstract

A sporting apparatus used by a person for engaging in a sporting activity. The sporting apparatus includes a single or multiple embedded MR sensors for measuring magnetic vectors of the earth magnetic field for dynamically recording a path of motion of the sporting apparatus in real time. In a preferred embodiment, the sporting apparatus further includes one or multiple MEMS accelerometer sensors for sensing acceleration of a designated portion of the sporting apparatus for measuring impact velocity as the designated portion impacting a ball. In a specific embodiment, the sporting apparatus is a golf club wherein the accelerometer sensors are disposed adjacent to the grip side of the shaft for sensing the impact of the club head against a golf ball. In another specific embodiment, the golf club further includes a magnetic field sensor disposed near the grip end of the golf club for measuring a motion path of the golf club.

Description

PRIORITY CLAIM

This application claims benefit of Provisional Application 60/583,876, entitled, Real-Time Measurements For Establishing Database of Sporting Apparatus Motion and Impact Parameters, filed Jun. 28, 2004, the entire contents of which is hereby incorporated by reference as if fully set forth herein, under 35 U.S.C. §119(e).

FIELD OF THE INVENTION

The present invention relates generally to design of microelectronic systems and methods for providing real-time measurements of the motion and impact parameters of sporting equipment. More particularly, this invention is related to the use of micro-electro-mechanical system (MEMS) and magneto-resistive (MR) sensors and other microelectronics installed in sporting equipment such as a golf club, a hockey stick, a boxing glove, a tennis racket or a baseball bat to obtain real-time motion parameter measurements for analyzing a player's performance and for establishing diagnostic and training databases associated with a given sport.

BACKGROUND OF THE INVENTION

Conventional methods of measuring instantaneous position, orientation and velocity of sporting equipment such as golf clubs, hockey sticks and baseball bats are limited by the high-cost measurement equipment such as high speed cameras, laser array and photo detector array. Such high-cost equipments are typically limited to club design and club-fit in R&D laboratories and/or pro shops as in the golf industry, for example. Further, the unwieldy size of the measurement equipment prevents the use of such equipment during actual play of the sport.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section diagram of the club shaft at the grip end that illustrates the relative location of the sensors in the system.

FIG. 2 is a schematic that represents a golfer's swing of a golf club.

FIG. 3 is a schematic that illustrates the roll angle.

FIG. 4 illustrates the magnetic field vector in the horizontal plane relative to the earth coordinate system.

FIG. 5 illustrates the coordinate system of the earth's magnetic field vector in the shaft coordinate system relative to the earth coordinate system.

FIG. 6 is a flow chart that illustrates a process flow for calculating parameters associated with a sporting implement at impact.

DETAILED DESCRIPTION OF THE INVENTION

According to certain embodiments, an embedded sensing system is disposed in optimally selected locations of a sporting implement, such as a golf club, a baseball bat, a tennis racket, a hockey stick, a boxing glove, etc. The embedded system includes sensors that are small in size, accurate and capable of high speed measurements in order to reliably and dynamically measure, record and/or transmit the measurements to a processor. According to certain embodiments, the sporting implement includes sensors as described herein, an embedded micro controller or digital signal processor (DSP), a memory, an optional display and an embedded communication module. The sensors include one or more magneto-resistive (MR) magnetic field or compass sensors.

According to certain embodiments, the MR sensors are used for dynamically measuring the three-dimensional magnetic vectors through the motion of the sporting apparatus, as in a golf swing or swing of a hockey stick, for example. For purposes of explanation, a golf club is used as an example. However, the embedded sensing system can be used for other sporting implements and can vary from implementation to implementation. The sporting implements include but are not limited to baseball bats, cricket bats, hockey sticks, tennis rackets, squash rackets, boxing gloves, etc. The sensors also include one or more MEMS accelerometer sensors for measuring the accelerations experienced by the sporting implement along various axes. Thus, the measurements made by the MR sensors and the MEMS sensors are used as input data into the micro controller or DSP for dynamically determining the movement profile, the launch angle, the face angle, and impact speed, and vibration characteristics of the sporting implement. Such parameters can be used for tracking and diagnosing the performance of the sportsman who is using the sporting implement. Such parameters can be sent through the communication module to a base station for further processing. The communication module can send data to the base station from the micro controller or DSP through wireless mechanisms such as infrared, Blue Tooth, WiFi, Zigbee or other Radio Frequency (RF) transmission mechanism. The communications module can also send data through RS232, SPI, USB or I²C and other wire based transmission mechanisms.

The one or more embedded MR sensors are adapted for measuring relative changes of earth magnetic field in projection with respect to the multiple axes for dynamically recording the motion path, impact angle and launch angle of the sporting implement in real-time. In one embodiment, the sporting apparatus further includes one or more MEMS accelerometer sensors for sensing acceleration along multiple axes of a designated portion of the sporting implement for sensing impact velocity (when the designated portion impacts a ball, for example) and the tilt angle between the sporting implement shaft and the earth gravitational direction. According to one embodiment, the sporting implement is a golf club where the accelerometer sensors and the magnetic sensors are disposed inside of the club shaft near the grip end for sensing a club head motion for measuring the velocity, club head orientation, hitting spot and motion path of the golf club head when a club head impact against a golf ball. According to certain other embodiments, the accelerometer sensors and the magnetic sensors are disposed inside of the club shaft near the grip end of the shaft.

The sensors, micro controllers or DSP, memory and communication modules can be separate semiconductor chips that are mounted on a printed circuit board (PCB) or connected by wires. Alternatively, the sensors, micro controllers or DSP, memory and communication modules can be integrated on a single chip that utilizes Application Specific Integrated Circuit Chip (ASIC) or Field Programmable Gate Arrays (FPGA) technologies that are capable of integrating several functions in a single chip.

The memory in the embedded sensing system can be flash memory or DRAM for storing the programs used by the micro controller or DSP and for storing the measurement data from the sensors. The flash memory can also be used to transport the data from the sporting apparatus to the base station for further analysis.

The base station is a separate unit that is not embedded in the sporting implement. The base station has a central processing unit (CPU) or a DSP, memory, display and communications modules to receive data transmitted by the embedded micro controller or DSP in the sporting implement for further processing and analysis. The base station can be but is not limited to a personal digital assistant (PDA), a cell phone or a portable handheld computer.

According to certain embodiments, the MR and MEMS sensors can be disposed adjacent to the club head for measuring the impact force of the club head against a golf ball, for example. The sensors can be mounted at the tip of the shaft of the golf club, or at the tip of the grip end of the shaft using a mounting module to be snapped onto the club.

Using the measurements from the sensors as described herein, the following parameters can be determined using the calculation methods described herein:

• • 1) angular difference of the sporting implement at moment of impact with the target object (examples of target objects are golf ball, hockey puck, baseball, etc.) compared with the address or static position.
  • 2) speed of the sporting implement at the moment of impact with the target object;
  • 3) direction of the sporting implement swing path;
  • 4) hitting zone of the sporting implement club face, if applicable (e.g., golf club face or hockey stick hook end. etc.); and
  • 5) determination of the swing plane.

The above parameters provide valuable evaluation feedback to the sportsman. A database can be maintained for storing the above parameters. The database can further include a data bank of data values of the above parameters associated with the performance of famous sportsman. Thus, a given player can analyze his performance based on comparisons with the data values associated with the performance of famous sportsman, or by comparing to another player of similar handicap, age, swing pattern, physical attributes, equipment used, etc.

Types of Sensors

The types of the sensors used in this design include a single-axis or multiple-axis magneto-resistive compass sensor (e.g. HMC1051 from Honeywell, Inc.) and a single-axis or multiple-axis MEMS accelerometer sensor (e.g. ADXL202 from Analog Devices).

Parameters Measured by the Sensors

The MR sensor measures the magnetic vector of the earth magnetic field along the MR sensor's axis. The MEMS accelerometer sensor measures the acceleration along the MEMS sensor's axis.

The Installed Locations of the Sensors

The sensors can be installed anywhere between the tip and the grip end of the club shaft. According to one embodiment, the sensors are installed near the grip end. When the sensors are installed near the grip end, there is minimum weight impact from the sensors and accompanying circuitry. The larger shaft diameter at the butt end is also convenient for installation of the sensors. The sensor system also bears relatively less force at the butt end of the shaft during the impact as compared to that at the club head.

FIG. 1 is a cross section diagram of the club shaft at the grip end that illustrates the relative location of the sensors in the system. In FIG. 1, the sensors are mounted on a printed circuit board (PCB) inside the shaft at the grip end of the shaft. The cross section shown in FIG. 1 has a centerline 30. Sensors 21, 22, 23, 24 and 28 are single-axis MEMS accelerometers and sensors 25, 26 and 27 are MR earth magnetic field sensors. The axis of sensors 21, 22 and 26 are along the Y (11) direction. The axis of sensors 23, 25 and 28 are along the Z (12) direction. The axis of sensors 24 and 27 are along the X (10) direction. X (10) Y (11) Z (12) are in the club shaft coordinate system.

However, according to certain embodiments, multiple-axes sensors can be used. For example, a two-axis MR sensor can replace the single-axis MR sensors 25 and 26. One two-axis accelerometer sensor can replace sensors 22 and 24.

Impact Velocity Calculation Method

FIG. 2 is a schematic that represents a golfer's swing of a golf club. Rod 101 represents the arms of the golfer, having the equivalent mechanical properties of his two arms, and rod 102 represents the golf club, having the mechanical properties of the club used in the swing. The joint (103) between rod 101 and rod 102 is a fully articulated joint. Further, joint 103 also represents the location of one set of sensors such as sensors 21, 22, 23, 24 of FIG. 1. The system rotates about an origin 100, which has a horizontal acceleration. The horizontal acceleration is along a direction in X_H Y_H plane. Location 104 is the location of another set of sensors, such as sensors 25, 26, 27 and 28 of FIG. 1. From the above model, the club head velocity at the impact is composed of three components. The three components are:

• • (1) The linear velocity of the rod 101 rotating around the origin 100. This velocity component can be measured by an accelerometer sensor (23) installed at joint 103;
  • (2) The linear velocity of the rod 102 rotating around the fully articulated joint 103. This velocity component can be measured by the centrifugal acceleration difference sensed by the sensor 23 at joint 103 (A23) and sensor 28 at 104 (A28) and the known distance between 103 and 104 (D(103-104)) and the distance between joint 103 and the club head or the club length (D103); and
  • (3) The velocity generated by the horizontal acceleration of the origin 100. This component is small and can be added base on the experimental results or simply neglected.
    Shaft Rotation Acceleration Calculation Method

In a typical golf swing, the shaft can have a rotation around centerline 30 as shown in FIG. 1. Such a rotation is for purposes of modeling the waggle of golfer's wrist and hand. This rotation acceleration can be measured by the acceleration difference of sensor 21 (A21) and sensor 22 (A22). This rotation acceleration is used in following roll angle calculation.

The Club Roll Angle (θ) Calculation Method

The roll angle (θ) is required for the launch angle (θ) and face angle (θ) calculation. The roll angle is defined as the angle between the club shaft and the gravitational force. FIG. 3 is a schematic that illustrates the roll angle. In FIG. 3, orthogonal coordinates X_H 108, Y_H 109, Z_H 110 represent the earth coordinate system, and (X_H, Y_H) plane is the horizontal plane. Location 104 is the location of sensors as previously described with reference to FIG. 2 and FIG. 1. Angle 106 is the roll angle (θ), axis 105 is in the direction of the earth's gravitational force. Axis 107 is an axis perpendicular to the longitudinal axis of the club shaft and parallel to the axis of the accelerometer sensor 21 installed at location 103 of FIG. 1. The roll angle is the angle between the horizontal plane and axis 107. The heading direction is in the direction of X_H 108 in the earth coordinate system. The acceleration component A21 can be measured by sensor 21. Thus, the roll angle (θ) can be calculated as arccosine (A21/g), where g is earth gravity.

The shaft rotation will affect the roll angle measurement and calculation. Therefore, instead of using A21 to calculate the roll angle, (A21-A22) should be used.

The Static Club Launch (Pitch) Angle (φ) Calculation Method

Before a golf swing, the golfer usually has a posture and has the club close to the ball in an “address” position. At the address position, a static launch angle or pitch angle (φ) can be measured by sensor 24 and calculated as arccosine (A24/g), where A24 is the acceleration measured by sensor 24 and g is earth's gravity.

The Earth Magnetic Field Vector in Earth Gravity Direction Calculation Method

If the orthogonal coordinates X_H 108, Y_H 109, Z_H 110 represent the earth coordinate system, and (X_H, Y_H) plane is the horizontal plane, then Z_H axis is the direction of the earth's gravity. FIG. 4 illustrates the magnetic field vector (Mx_H113, My_H114, Mz_H115) in the horizontal plane relative to the earth coordinate system. Angle 116 is the face angle. FIG. 5 illustrates the coordinate system of the earth magnetic field vector (Mx117, My118, Mz119) in the shaft coordinate system (i.e., embedded sensor coordinate system) relative to the earth coordinate system X_H 108, Y_H 109, Z_H 110. Angle 120 is the launch angle, and angle 106 is the roll angle. Mearth 111 is the earth's magnetic field. The earth's magnetic field can be expressed as M (Mx_H, My_H, Mz_H), where Mz_H is the same as M_g and M²=Mx_H²+My_H²+Mg². Because the angle between the earth's magnetic field and the earth's gravity does not change at any given location, M_g will be constant at the given location. Therefore, M_g will not change with the club motion.

At the address position when the golf shaft is static, the following parameters can be measured from the sensors as previously described:

• • shaft roll angle (θ₀) from sensor 21;
  • shaft pitch angle (φ₀) from sensor 24;
  • earth magnetic vector along X (10) direction Mx₀ from sensor 27;
  • earth magnetic field vector along Y (11) direction My₀ from sensor 26; and
  • earth magnetic field vector along Z (12) direction Mz₀ from sensor 25.

Mx₀, My₀ and Mz₀ can be transformed back to the horizontal plane (X_H, Y_H) by applying the rotational equations shown below:
Mx_H=Mx₀*cos(φ₀)+My₀*sin (φ₀)*sin(φ₀)−Mz₀*cos(θ₀)*sin(φ₀)
My_H=My₀*cos(θ₀)+Mz₀*sin(θ₀)
Azimuth(face angle(α₀))=arc Tan(My_H/MX_H)
Therefore, M_g²=M²−Mx_H²−My_H²
The Dynamic Launch Angle (φ) and Face Angle (α) Calculation Method

During a golf swing at impact, the following parameters can be measured by sensors:

• • shaft roll angle (θ) from sensor;
  • earth magnetic vector along X (10) direction Mx from sensor 27;
  • earth magnetic field vector along Y (11) direction My from sensor 26; and
  • earth magnetic field vector along Z (12) direction Mz from sensor 25.

Unlike the static situation, the pitch angle can not be measured by the accelerometer sensor 24 due to the interference of the shaft acceleration along the X (10) direction in the swing.

By using the same rotational equations shown below, Mx, My and Mz can still be transformed back to the horizontal plan (X_H, Y_H),
Mx_H=Mx*cos(φ)+My*sin(θ)*sin(φ)−Mz*cos(θ)*sin(φ)
My_H=My*cos(θ)+Mz*sin(θ)
Azimuth(face angle(α))=arc Tan(My_H/Mx_H)
M_g²=M²−Mx_H²−My_H²
Therefore,
Azimuth(face angle(α))=arc Tan((My_H/root square(M²−M_g²−My_H)²)=arc Tan(((My*cos(θ)+Mz*sin(θ))/root square(M²−M_g²−(My*cos(θ)+Mz*sin(θ))²)
Launch angle(φ)=arc sine((−B+/−root square(B²−4AC))/2A)
Where A=Mx²+((Mz*cos (θ)−My*sin (θ))², B=2*(Mz*cos (θ)−My*sin (θ))*root square (M²−M_g²−(My*cos (θ)+Mz*sin (θ))²), and C=M²−M_g²−Mx²−(My*cos (θ)+Mz*sin (θ))²

The three axis MR sensor orientation on the PCB board can be varied as long as the angle between one of its axes and the shaft longitudinal direction is known. A fix angle rotation operation can bring the coordinates back to the (Mx, My, Mz) coordinates discussed above.

FIG. 6 is a flow chart that illustrates a process flow for calculating parameters associated with a sporting implement at impact. At block 601, the sensing and DSP system (embedded and non-embedded) are initialized. At block 602, some data is input into the base station (such as a PDA) and the sensors are calibrated at block 604. Examples of data that is input into the base station are arm length of the player, and height of the player. The sensors can be calibrated based on a table lookup automatically performed by the base station, or the base station can be equipped to calculate the calibration. In the case of a table look-up, the table of data can be resident on the base station or can be downloaded over-the-air onto the base station from an appropriate server. The sensors need to be calibrated based on the geographic location where the game is played. At block 606, static position (address position, for example) measurements are taken. At block 608, the sporting implement is swung and impact of the sporting implement against a target object (such as a golf ball, shuttle cock, etc.) takes pace. At block 610, the impact velocity, the roll angle, the face angle, the launch angle and the hitting zone are calculated. At block 612 the swing path is calculated. At block 614, the measurements and results are stored in the base station such as a PDA. At block 616, the results are displayed on a display device such as the PDA and the results and measurement can be optionally transmitted (uploaded) to a relational database. The relational database can be web-based. At block 618, the process flow is complete and the system is reset.

In the foregoing specification, embodiments of the invention have been described with reference to numerous specific details that may vary from implementation to implementation. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.

Claims

1. A method for providing sports performance feedback to a sports player who is using a sporting implement, the method comprising:

using at least one magneto-resistive sensor embedded in said sporting implement for measuring orientation parameters; and

using said orientation parameters for dynamically determining one or more results from a set comprising: movement profile, velocity, acceleration, impact angle, launch angle, face angle and impact speed, hitting zone, direction of swing and swing path plan of said sporting implement.

2. The method of claim 1, wherein dynamically determining one or more results further comprises using, embedded in said sporting implement, at least one device from a set of devices comprising: a microcontroller and a digital signal processor (DSP)

3. The method of claim 1, wherein measuring said orientation parameters includes measuring three-dimensional earth magnetic field vectors associated with a motion of said sporting implement.

4. The method of claim 1, further comprising using at least one accelerometer sensor for measuring acceleration parameters associated with a motion of said sporting implement for dynamically determining said one or more results.

5. The method of claim 1, further comprising communicating said parameters and said one or more results to a remote computer for further processing using wireless mechanisms.

6. The method of claim 5, wherein said wireless mechanisms comprises one or more of: infrared, Blue Tooth, WiFi, Zigbee, and Radio Frequency transmission.

7. The method of claim 1, further comprising communicating said parameters and said one or more results to a remote computer for further processing using wire-based mechanisms.

8. The method of claim 7, wherein said wire-based mechanisms comprises one or more of: RS232, SPI, USB and I2C.

9. The method of claim 1, further comprising using a communication module embedded in said sporting implement, said communication module for sending said parameters and said one or more results to a remote computer for further processing.

10. The method of claim 1, further comprising using a portable display module capable of communicating with said sporting implement, said display module for displaying said one or more results.

11. The method of claim 1, further comprising using a memory module embedded in said sporting implement, said memory module for storing data associated with said at least one magneto-resistive sensor and said feedback.

12. The method of claim 1, further comprising using a remote database for storing said one or more results.

13. The method of claim 1, further comprising using a remote database for comparing said one or more results with corresponding performance results associated with other sports players.

14. The method of claim 1, further comprising using a remote database for comparing said one or more results with corresponding historical data of associated with a past performance of said sports player.

15. The method of claim 1, wherein said parameters are used for tracking and diagnosing a performance of said sports player during use of said sporting implement.

16. The method of claim 1, wherein said sporting implement is any one of a set of implements comprising: a baseball bat, a cricket bat, a hockey stick, a tennis racket, a squash racket, a boxing glove.

17. A system for providing sports performance feedback to a sports player who is using a sporting implement, the system comprising:

at least one magneto-resistive sensor and at least one accelerometer sensor embedded in said sporting implement for measuring velocity, acceleration and orientation parameters; and

wherein said parameters are used for dynamically determining one or more results from a set comprising: movement profile, launch angle, face angle and impact speed, hitting zone, direction of swing and swing path plan.

18. A system for providing sports performance feedback to a sports player who is using a sporting implement, the system comprising:

means for measuring velocity, acceleration and orientation parameters; and

means for dynamically determining, based on said parameters, one or more results from a set comprising: movement profile, launch angle, face angle and impact speed, hitting zone, direction of swing and swing path plan.

19. A system for providing sports performance feedback to a sports player who is using a sporting implement, the system comprising:

at least one magneto-resistive sensor and at least one accelerometer sensor embedded in said sporting implement for measuring velocity, acceleration and orientation parameters;

wherein said parameters are for dynamically determining one or more results from a set comprising: movement profile, launch angle, face angle and impact speed, hitting zone, direction of swing and swing path plan;

at least one device, embedded in said sporting implement, from a set of devices comprising: a microcontroller and a digital signal processor (DSP) for dynamically determining said one or more results;

at least one display module embedded in said sporting implement, said display module for displaying said one or more results; and at least one communication module embedded in said sporting implement, said communication module for sending said parameters to a remote computer for further processing.

20. A method for providing sports performance feedback to a sports player who is using a sporting implement, the method comprising:

using sensors embedded in said sporting implement for measuring velocity, acceleration and orientation parameters; and

using said parameters for dynamically determining one or more results from a set comprising: movement profile, launch angle, face angle and impact speed, hitting zone, direction of swing and swing path plan.