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CHAPTER 1

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1. INTRODUCTION

Tennis tutor is an automated, smart ball throwing machine which

greatly helps the player to train in a better way. Most of the ball throwing

machines available in India are imported and costly, so there came an idea

to design and build a cost efficient machine with added features. The

general specifications of the tutor machines involve the type of spin

induced on the ball and the portion of the court where the ball is to be

thrown. Apart from this, the tennis tutor brings in the features of remotely

controlling the machine through an app in our mobile phone. The app also

gives us statistical information about the hours of training, level of training,

etc. The smart feature of this product is the use of Myo armband, the

gesture recognition device to easily control various parameters of the

machine. Tennis tutor will be built on the myRIO Platform. The product

involves controlling various DC motors, servo motors and wiper motors. It

also runs algorithms that precisely control various parameters and throw

the ball in the desired direction. It also communicates with our mobile

phone app via Bluetooth and also interfaces with Myo. The various

interfaces are done with the help of the Bluetooth module HC-06.

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CHAPTER 2

4

2. PROPOSED METHODOLOGY

Fig 2.1 Block diagram of the proposed system

The first input is given through the mobile phone app which has the

facilities to change the position, direction and spin induced on the ball

throw and the ball. It also has the various levels of training that a player

could go through. The other input is given through the Myo armband which

can give inputs through the gestures. These inputs are given to the MyRIO

which acts as the processing system that helps to get the desired outputs to

drive the appropriate motors. The motor drivers are the control units that

rotate the motors in a specific speed. The motors rotate accordingly to the

necessary speeds.

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CHAPTER 3

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3. HARDWARE DESCRIPTION

The hardware section of the system has two parts.

Electronic Section

o NI myRIO

o Bluetooth module HC-06

o Myo Armband

o DC motor driver – MD30C

Mechanical Section

3.1 ELECTRONIC SECTION

3.1.1 NI myRIO - DEVICE DESCRIPTION

Fig 3.1 myRIO

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National Instruments has been working on a device called NI

myRIO, an hardware & software platform that aims at giving engineering

students the ability to design real systems quickly for automation, robotics,

data logging or embedded systems. The hardware is based on Xilinx Zynq-

7010 with a dual-core ARM Cortex-A9 processor and an FPGA with

28,000 programmable logic cells, and features 10 analog inputs, 6 analog

outputs, audio I/O channels, and up to 40 lines of digital input/output

(DIO). The National Instruments myRIO-1900 is a portable reconfigurable

I/O (RIO) device that students can use to design control, robotics, and

mechatronics systems. The pinouts, connectivity information, dimensions,

mounting instructions, and specifications for the NI myRIO-1900 are

described in the following sections.

3.1.2 HARDWARE SPECIFICATION

Fig 3.2 myRIO outline

The hardware specifications are as follows:

SoC – Xilinx Zynq-7010 with a dual core Cortex A9 processor and

FPGA with 28,000 cells

System Memory – Unknown

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Storage – Unknown

Expansion Ports: myRIO expansion Ports (MXP) – Two identical

ports (MXP A and MXP B) with 4 analog inputs, 6 digital

inputs/outputs, 2 analog outputs, 1 quad encoder, 3 PWMs, 1 UART,

1 I2C and 1 SPI by default. Ports configuration is customizable with

LabVIEW FPGA.

Mini Systems Port (MSP) – Power, 2 analog outputs, 4 analog

inputs, and 8 digital inputs/outputs by default. Ports configuration is

customizable with LabVIEW FPGA.

Connectivity – Wi-Fi

USB – 1x USB host port, 1x USB device port for connection to PC

Audio – Audio In, Audio Out

Misc. – User and reset buttons, power, status and Wi-Fi LEDs, 4

user-defined LEDs, on-board accelerometer.

Power – 6-16V input, or battery.

3.1.3 PINOUT DIAGRAM

Fig 3.3 myRIO pinout

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Fig3.4 Detailed pinout diagram of port A and port B

Fig 3.5 Detailed pinout diagram of port C

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Table 3.1 Voltage levels and direction of the pins

Signal Name

Reference

Direction

Description

+5V DGND Output +5 V power output.

AI <0..3> AGND Input 0-5 V, referenced, single-ended

analog input channels.

AO <0..1> AGND Output 0-5 V referenced, single-ended

analog output

+3.3V DGND Output +3.3 V power output.

DIO <0..15> DGND Input or

Output

General-purpose digital lines with

3.3 V output, 3.3 V/5 V-compatible

input.

UART.RX DGND Input UART receive input.

UART lines are electrically identical

to DIO lines.

UART.TX DGND Output UART transmit output. UART lines

are electrically identical to DIO

lines.

DGND N/A N/A Reference for digital signals, +5 V,

and +3.3 V.

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3.1.4 BLOCK DIAGRAM

Fig 3.6 Internal block diagram of myRIO

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NI myRIO-1900 Expansion Port (MXP) connectors A and B carry

identical sets of signals. The signals are distinguished in software by the

connector name, as in Connector A/DIO1 and Connector B/DIO1.

3.1.5 ANALOG INPUT CHANNELS

The NI myRIO-1900 has analog input channels on myRIO

Expansion Port (MXP) connectors A and B, Mini System Port (MSP)

connector C, and a stereo audio input connector. The analog inputs are

multiplexed to a single analog-to-digital converter (ADC) that samples all

channels. MXP connectors A and B have four single-ended analog input

channels per connector, AI0-AI3, which you can use to measure 0-5 V

signals. MSP connector C has two high-impedance, differential analog

input channels, AI0 and AI1, which you can use to measure signals up to

±10 V. The audio inputs are left and right stereo line-level inputs with a

±2.5 V full-scale range.

3.1.6 MYO ARMBAND

Fig 3.7 Myo armband

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The Myo armband is a gesture recognition device, worn on the wrist

and manufactured by Thalmic Labs. The Myo enables the user to control

technology wirelessly using various wrist and forearm motions. It uses a

set of electromyography (EMG) sensors that sense electrical activity in the

forearm, combined with a gyroscope, accelerometer and magnetometer to

recognize gestures. The Myo can be used to control video games,

presentations, music and visual entertainment. It differs from the Leap

Motion device as it is worn rather than a 3D array of cameras that sense

motion in the environment. The eight segments of expandable

casing house the Myo armband's components and are connected using

stretchable material that allows them to expand and contract relative to

each other, so that the Myo armband can comfortably fit each user's unique

physiology. The electrical sensors measure electrical signals traveling

across the user's arm, which the Myo armband translates into poses and

gestures. The USB charging port allows you to charge the Myo armband's

internal battery using a USB power adapter or a conventional USB port on

a computer. The logo LED shows the sync state of the Myo armband. It

pulses when the Myo armband is not synced. The LED becomes solid

when you perform the Sync Gesture successfully and the Myo armband is

synced to your arm. The status LED shows the current state of the Myo

armband. It lights up in blue once the Myo armband is connected to a

device.

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The Myo armband is connected to a device (e.g. a computer, tablet,

or smartphone) using Bluetooth 4.0 Low Energy. The SDK takes care of

all of the low level details related to Bluetooth connections and data

transmission. At its core, the Myo armband provides two kinds of data to

an application, spatial data and gestural data. Spatial data informs the

application about the orientation and movement of the user's arm. The Myo

SDK provides two kinds of spatial data:

An orientation represents which way the Myo armband is

pointed. In the SDK this orientation is provided as a quaternion

that can be converted to other representations, like a rotation

matrix or Euler angles.

An acceleration vector represents the acceleration the Myo

armband is undergoing at any given time. The SDK provides this

as a three-dimensional vector.

Gestural data tells the application what the user is doing with their

hands. The Myo SDK provides gestural data in the form of one of several

preset poses, which represent a particular configuration of the user's hand.

For example, one pose represents the hand making a fist, while another

represents the hand being at rest with an open palm. The Myo armband

provides information about which arm it is being worn on and which way

it is oriented - with the positive x axis facing either the wrist or elbow. This

is determined by a Sync Gesture performed upon putting it on. The Myo

armband similarly detects when it has been removed from the arm. An

application can provide feedback to the wearer of the Myo armband by

issuing a vibration command. This causes the Myo armband to vibrate in

a way that is both audible and sensed through touch.

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3.1.7 USE OF MYO

Myo band will be used to vary the parameters like ball speed, spin,

type and direction of the delivery. Myo will be connected to myRIO via

Bluetooth. The gestures recognized by Myo will be programmed for the

above various desired functions. This is done to reduce the amount of user

interaction with the system physically.

3.1.8 HC-06 BLUETOOTH MODULE DESCRIPTION

Fig 3.8 HC-06 Bluetooth module

This Bluetooth module can easily achieve serial wireless data

transmission. Its operating frequency is among the most popular 2.4GHz

ISM frequency band (i.e. Industrial, scientific and medical). It adopts

Bluetooth 2.0+EDR standard. In Bluetooth 2.0, signal transmit time of

different devices stands at a 0.5 seconds interval so that the workload of

Bluetooth chip can be reduced substantially and more sleeping time can be

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saved for Bluetooth. This module is set with serial interface, which is easy

to use and simplifies the overall design/development cycle.

3.1.9 HC-06 SPECIFICATIONS

Bluetooth protocol: Bluetooth 2.0+ EDR standard

USB protocol: USB v1.1/2.0

Operating frequency: 2.4GHz ISM frequency band

Modulation mode: Gauss frequency Shift Keying

Transmit power: ≤ 4dBm, second stage

Sensitivity: ≤-84dBm at 0.1% Bit Error Rate

Transmission speed: 2.1Mbps(Max)/160 kbps(Asynchronous)

1Mbps/1Mbps(Synchronous)

Safety feature: Authentication and encryption

Supported configuration: Bluetooth serial port (major and minor)

Supply Voltage: +3.3 VDC 50mA

Operating temperature: -20 to 55℃

Size: 36.5*16mm

Weight: 4g

3.1.10 30A DC MOTOR DRIVER – MD30C

MD30C is the successor of MD30B which is designed to drive

medium to high power brushed DC motor with current capacity up to 80A

peak and 30A continuously. Fully NMOS design not only provides faster

switching time, it is also more efficient and no heatsink or fan is required.

Besides that, MD30C also incorporates some user friendly features

such as reverse polarity protection and on-board PWM generator which

allows it to operate without host controller. The motor can simply be

17

controlled with the on-board switches and speed potentiometers. External

switches and potentiometer can also be used.

Fig 3.9 MD30C 30A motor driver

FEATURES

Bi-directional control for 1 brushed DC motor.

Motor Voltage: 5V - 30V.

Maximum Current: 80A peak (1 second), 30A continuously.

Reverse polarity protection.

3.3V and 5V logic level input.

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Fully NMOS H-Bridge for better efficiency and no heat sink is

required.

Speed control PWM frequency up to 20 KHz (Actual output

frequency is same as input frequency when external PWM is

selected).

On-board PWM generator with switches and potentiometer for

standalone operation.

Support both locked-antiphase and sign-magnitude for external

PWM operation.

3.2 MECHANICAL STRUCTURE

The base plate is the one which generally holds the entire structure.

The wheels are attached to the structure in order to help the system to attain

the motion towards the left or the right side of the court. The basic structure

which is held over the base plate is supported using the side frames. The

wheels rotate in opposite direction and the gap between them is slightly

less than the typical tennis ball diameter. The ball speed and spin is

controlled by controlling the speed of the DC motors which have a

maximum of 5200rpm. To give the ball direction, the frame must move in

two axis, lateral movement and Up-down movement. These movements

can be controlled with the help of wiper motors. For the up and down

movement there is a wiper motor to the frame with the help of the bearing

that in turn helps to move the frame up and down and in the case of the

lateral movement there is a wiper motor to the base plate where there are

two rotatable wheels that help to move the system which is at the back and

a wheel at the front to make the lateral movement. This in turn helps to

stabilize the system from moving from its initial position. And for the

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power source for the motors, the testing is done with various options like

normal lead-acid battery and lithium-polymer.

The basic structure was designed using Cryo cad software. The

design photos are attached below:

Fig 3.10 Design model 1

This is 3D model of the frame which is used for the tennis tutor

machine. The rollers are made of the foam material and the frames are

made of steel. There are aluminum based rounded frames attached to the

rollers to enhance the roller spin without inducing any imbalances while

the roller is spinning.

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Fig3.11 Deign model 2

The finished model of the mechanical structure is attached to get

brief idea of the design.

Fig 3.12 Image of the assembled system

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The clear idea about the type of ball delivery is obtained through the

below image.

Fig 3.13 Type of spin induced on the ball

The future upgrade to the system is the design of ball feeding

mechanism, because it is not possible to go and keep the ball between the two

rollers which is not going to be called as an automated tutor. The design is an

optimum rollers considering all the necessary parameters such as the weight of

the balls in the container and type of the motor used.

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The designed structure of the roller is as bellow.

Fig 3.14 Design of roller for ball feeding mechanism

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CHAPTER 4

24

4. SOFTWARE DESCRIPTION

The software section consists of two parts, one is programming the

myRIO using NI LabVIEW and other is developing an android application for

the remote control of the system.

4.1 NI LabVIEW

LabVIEW is an acronym for Laboratory Virtual Engineering

Workbench and it’s a system-design platform and development environment for

a visual programming. LabVIEW is commonly used for data acquisition,

instrument control and industrial automation on a variety of platform. This tool

is chosen because it suits the most for the tennis tutor.

LabVIEW ties the creation of user interfaces into the development

cycle. LabVIEW programs are called Virtual Instruments (VIs). Each VI has

three components: a block diagram, a front panel, and a connector panel.

The block diagram of the VI is shown below.

Fig 4.1 VI block diagram for the manual control

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Fig 4.2 VI block diagram for roller motors

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Fig 4.3 VI block diagram for Myo control of the system

Fig 4.4 VI front panel

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4.2 MIT App Inventor

App inventor for android is an open source web application

originally provided by google and now maintained by Massachusetts Institute of

Technology (MIT). Hence the name, MIT App Inventor.

It allows newcomers to computer programming to create software

applications for the Android operating system (OS). It uses graphical interface,

very similar to Scratch and the StarLogo TNG user interface, which allows user

to drag-and-drop visual objects to create an application that can run on Android

devices

It allows real time debugging of the apps which are under

development on the connected devices via Wi-Fi, not just USB.

Fig 4.5 User Interface of the MIT App inventor

The app for controlling the tutor is created using this MIT App

Inventor. It has the three screens to control the tutor. First is the screen which has

two buttons to select whether the control has to be manual or automatic with

specific training level.

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Fig 4.6 First screen for the selection of mode

Next screen is the manual mode which has buttons and sliders to

control the speed of the motors and to move the tutor to left or right and to change

the pitch of the ball. This is called as the manual mode.

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Fig 4.7 Manual mode screen of App

The Third screen is the screen for players to get trained at various

levels via radio buttons with values beginner, professional and world class. And

this screen also displays about the time of training the player has trained. This is

called as Automatic mode

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Fig 4.8 Automatic mode screen of App

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CHAPTER 5

32

5. WORKING PRINCIPLE

The MyRIO is going to act as the central console or the heart of the

embedded system. The MyRIO consists of pins to control the motors. So

this is mainly going to support our action. The inputs are obtained from the

Myo armband and also from the android app that is created for our tennis

tutor. The inputs are basically passed with help of the Bluetooth module

(HC-06).The MyRIO then takes the inputs and it varies the speed of the

corresponding motors .This is done with the help of the motor drivers. The

motor drivers decide the speed at which the roller should rotate. Thus the

speed of the roller is manually controlled in order to obtain the desired spin

on the ball that is played. The android app generally has the features to

change the speed of the motor and the direction of the ball throw which can

be given as inputs to the myRIO that executes the function

correspondingly. The Myo involves the use of gestures to give inputs to

the system. This system makes use of four gestures and using these four

gestures the various operations are made.

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CHAPTER 6

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6. COST ANALYSIS

The existing machine without any added features to the tutor except

for the ball throwing action costs about 699$(which is 46K approx. without

any taxes included).A fully automated machine which can only be remote

controlled or with physical contact with the machine costs about 1099-

3299 $ (which is from 75k-200k in Indian rupees). So from the above

analysis it clearly shows that it is beyond the money an average Indian can

spend on it. The machine that is built costs only about 50K at the maximum

with the full features embedded in it.

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CHAPTER 7

36

7. CONCLUSION

The model which is presented helps to enhance the usability of a

product, satisfies the people who want to learn the sport and it involves a

wide variety of features embedded in it. This model turns out to be a very

economical and useful product to the people of our country.

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CHAPTER 8

38

8. REFERENCE

1. Prince Manufacturing Co., Inc. (1980) “Propulsion device for tennis

balls and like spherical objects having an improved programmed

discharge of the oscillatory type”.

2. United States Machine Works, Inc. (1981) “System and apparatus for

program controlled delivery of game balls”.

3. Eriksen Willy M (1988) “Projector for projecting a tennis ball”

4. Braden Victor K (1989) “Automatic tennis feeding and serving

apparatus”

5. Werner Salansky (1992) “Ball-throwing device for tennis balls”

6. Mattel, Inc. (2003) “Ball launching apparatus”.

7. Unified Solutions, Inc. (2005) “Variable trajectory kit for a ball

pitching mechanism”.

8. Rachel Baurnel (2012) “Metered ball delivery”.

9. Master Pitching Machine, Inc. (1994) “Ball collection and distribution

apparatus”

10. Hurst H Edson (2014) “Tennis ball throwing machine”