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Engineering a Better Golf Swing
University of
Pennsylvania
System Block Diagram
Transmission Diagram
Sensors and Calibration Methods
Velocity Measurement: ADXL150 Accelerometer
The ADXL150 has a 50G measurement range with on chip filters and zero G nulling
features. As there were no high-G calibration methods available, it was calibrated by
attaching it to a pendulum and connecting the output to an integrator. By varying the
pendulum’s amplitude, the peak velocity was calculated with mechanics equations
and the output voltage was measured.
Department of Electrical
and Systems
Engineering
Angle Measurement: ADXL320 Accelerometer
The ADXL320 is used as an inclinometer via it’s DC response to gravity. It was
calibrated by precisely measuring angles in the range of -45° to 45° in increments of
1° (via right triangle trigonometry) and recording the lookup table of the output
voltages for use in the display unit.
ABSTRACT:
Quantifying and measuring certain aspects of a
golf swing is a helpful tool for any golfer.
Currently, the only way to achieve this is by
traveling to an indoor, controlled environment
rigged with complex sensors and having a
system contained within measure the swing. Not
only are these facilities relatively sparse, but they
are prohibitively expensive to the average golfer.
The sensor blocks consist of the actual sensors to measure club velocity, angle and contact point, as well as the
circuitry needed to condition the values for transmission. User signals and coordination between the conditioning
circuits ensure that the data is collected properly and captured at the correct point in the swing.
Launch Angle Measurement:
The angle of the launch is measured as the player tees up the ball and prepares for the swing. It is measured by
a precise inclinometer to 1° of accuracy, and the value is held with a sample/hold circuit until transmission.
Club Speed Measurement:
A high G accelerometer is mounted on top of the club head with its axis of sensitivity in the direction of the swing.
The acceleration values generated by the accelerometer are passed to the conditioning circuit, which integrates
and scales them to get a velocity reading. This value is captured by a sample/hold circuit and held until
transmission. The velocity is measured to an accuracy of 1 mph.
The contact sensors themselves are strips of piezo-electric film. When the ball strikes one of the four strips, a
peak detector circuit holds the output voltage and sets a flip-flop. The flip-flop values are converted to one analog
value in preparation for transmission and are also used to generate the signal to capture the velocity value of the
club.
Display Unit
The display unit is composed of an IR receiver, an HC11 microcontroller, two 4-digit LED displays (for the velocity
and angle readings) , 4 LEDs (for the contact region) and user input buttons. It receives the input from the club
and displays the data to the user, who can scroll through up to 500 stored measurements from the current golf
session.
2.8
2.7
2.6
2.5
2.4
2.3
2.2
Inclination (Degrees)
Inclinometer Output Voltage vs. Inclination
45
42
39
36
33
30
27
24
21
18
15
12
9
6
3
0
-3
-6
-9
-1
2
-1
5
-1
8
-2
1
-2
4
-2
7
2.1
-3
0
The communication system makes use of Pulse Width Modulation to transmit the data. For each measurement to
be transmitted, the duty cycle of a 300 Hz square wave is changed proportionally to the voltage captured. The
square wave is fed to an IR LED, which transmits the data to the display unit. Since signals the three signals only
take 1/300th of a second each to transmit, full data transmission is accomplished in 10 ms.
2.9
-3
3
Communication System
GROUP 11
(clockwise from left: PVDF Strip, ADXL150 Accelerometer, ADXL320 Evaluation Board)
-3
6
Contact Region Measurement:
-3
9
DEMO TIMES: April 21st,
11-11:30am & 1:30-3pm
Sensors and interfacing circuitry
-4
2
ADVISOR:
Professor Jan Van der
Spiegel
The system is broken down into three overarching subsystems: on club sensors, an on club communication
circuit and an off club display unit.
-4
5
AUTHORS:
Seth Charlip-Blumlein
Shehzad Khan
System Design
PVDF is a material that produces a voltage between its two metalized surfaces when
a force is applied. No calibration was necessary for this material, as precise output
values weren’t important for it to function as an “on/off” contact sensor.
Output Voltage (Volts)
The solution to these problems is a series of
sensors and the necessary interfacing circuitry,
integrated onto a golf club. The system is
designed to measure the velocity of the swing,
the angle the ball is launched at and the region
of the club face where impact occurs. Accuracy,
unobtrusiveness and portability are the key
factors for this system and they drove the
approach to the project.
Contact Region Measurement: Polyvinylidene Fluoride Sheet