S16: Motion Copy Bot

Grading Criteria

• How well is Software & Hardware Design described?
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• Code Quality
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  • Software Block Diagrams
  • Hardware Block Diagrams

    Schematic Quality

  • Quality of technical challenges and solutions adopted.

Project Title

Motion Copy Bot

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Abstract

Motion Copy Bot aims to copy the motion of the user. Robot mimics the direction of the user's movement. The Bot moves only when the user is in motion and stops as soon as the user halts. The user's wearable device communicates with the Bot and co-ordinates its movement. When the Bot detects an obstacle on its path it notifies the user and stops. Upon this alert, the user determines the alternate path for the Bot.

Objectives & Introduction

Project Objectives:

• Wireless Communication between user and Bot using Xbee.
• Determining direction and movement of the user with the help of Magnetometer and Accelerometer.
• Controlling the steering and throttle of the Bot.
• Obstacle Detection using Ultrasonic sensor.

Team Members & Responsibilities

• Ankita Singhal
  • Wireless communication, Speed and Direction sensor module
• Manali Deshmukh
  • Hardware Design and assembling, Motor Driver, Obstacle Avoidance
• Shaurya Jain
  • Hardware Design and assembling, Motor Driver, Obstacle Avoidance
• Sukriti Choudhary
  • Wireless communication, Speed and Direction sensor module

Schedule

Week#	Date	Task	Actual	Status
1	3/18/2016	Team discussion on understanding the requirements and deciding on how to proceed with the project. Assigning responsibilities to each team member.	Discussed about requirements. Assigned module wise responsibilities.	Completed
2	3/29/2016	Finalizing the bill of material. Ordering the components.	Finalized the components. Ordered the components.	Completed
3	4/04/2016	Hardware Design of Robot assembly and motor driver. Follow up on component procurement.	All components received. Initiated Hardware design of robot assembly.	Completed
4	4/11/2016	Assembling the parts of Robot and motor driver. Capturing the data from LSM303.	All parts of Robot and Motor Driver assembled. Accelerometer and Magnetometer data successfully captured.	Completed
5	4/18/2016	Establishing basic wirelesss communication between two SJOne Boards. Interfacing the motor with SJOne board and controlling the speed and direction.	Successful transmission of data from one board to another using Xbee. Successfully able to control the motor's direction using SJOne Board.	Completed
6	4/25/2016	Testing of wireless transmission for actual data between two nodes. Calibration of linear accelerometer and magnetometer sensors. Interfacing of the obstacle avoidance module.	Able to transmit direction and motion from the user node to the slave node via Xbee. Calibrated LSM303 sensor. Slave is able to detect obstacles using Ultrasonic sensor.	Completed
7	5/05/2016	Integration of all the modules. Testing and Debugging.	Successfully integrated all the modules. Minor issues in copying the motion.	Completed
8	5/12/2016	Final testing of the Motion copy Bot.		In Progress

Parts List & Cost

Item#	Part Description	Vendor	Qty	Cost
1	SJ One Board (LPC 1758)	From Preet	2	$160
2	RC Car	Sheldon Hobbyist	1	$110
3	Accelerometer/Magnetometer LSM303	Adafruit	2	$40.00
4	Wireless Module XBee S1	From Preet	2	$0
5	Motor Driver IC	From Amazon	1	$7
6	Battery Pack	From eBay	1	$17.99
7	Ultra Sonic Sensor	From Preet	2	$0

Design & Implementation

Master Side Block Diagram

Bot Side Block Diagram

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Hardware Design

Car Assembly

Magnetometer

LSM303

LSM303 is a triple-axis Accelerometer+Magnetometer (Compass) Board. It has a magnetic field full scale of ±1.3 / ±1.9 / ±2.5 / ±4.0 / ±4.7 /±5.6 / ±8.1 gauss. The system senses the magnetic field applied to it and generates a corresponding digital output. It includes an I2C serial bus interface that supports standard and fast mode 100 kHz and 400 kHz.

The structure of magnetometer is etched with microscopic coils. An excitation current is passed through the coils, and the Lorentz Force due to the magnetic field causes the structure to deflect. Once again the deflection is converted to an output voltage proportional to the strength of the magnetic field in that axis.

We use two magnetometers, one for obtaining the orientation of the user and the other for orientation of the Bot. The Bot aligns itself to match the user's orientation based on the error computed by comparison of the two orientations.

Accelerometer

The MMA8452Q is a smart low-power, three-axis, capacitive micro-machined accelerometer with 12 bits of resolution.The MMA8452Q has user selectable full scales of ±2g/±4g/±8g with high pass filtered data as well as non filtered data available real-time.

The internal structure of accelerometer are suspended by polysilicon springs which allow them to deflect when subject to acceleration in the X, Y and/or Z axis. Deflection causes a change in capacitance between fixed plates and plates attached to the suspended structure. This change in capacitance on each axis is converted to an output voltage proportional to the acceleration on that axis.

The movement of the user is sensed by the accelerometer sensor on the wearable device. This data is transmitted to the Bot, which in turn determines the start and stop motion of the Bot.

XBee Module

The XBee Modules meet IEEE 802.15.4 standards. The module operates within the ISM 2.4 GHz frequency band.The XBee®/XBee-PRO® RF Modules interface to a host device through a logic-level asynchronous serial port. Through its serial port, the module can communicate with any logic and voltage compatible UART. Devices that have a UART interface can connect directly to the pins of the RF module as shown in the figure. Data enters the module UART through the DI pin (pin 3) as an asynchronous serial signal.

Two Xbee Modules are being used in the project. One on the user side and the other on the Bot. Both act as transceivers and full duplex communication is established. The magnetometer and accelerometer data is transmitted over Xbee modules from user and Bot.

Ultrasonic Sensor

Ultrasonic sensors use high frequency sound to detect and localize objects in a variety of environments. Ultrasonic sensors transmits sound and measures the time interval between transmission and its reflection back from nearby objects. Based upon this time interval, it outputs a corresponding range reading.

LV-MaxSonar-EZ1 is an ultrasonic sensor IC that provides very short to long-range detection.It detects objects from 0-inches to 254-inches (6.45-meters) and provides sonar range information from 6-inches out to 254-inches with 1-inch resolution. It works on 2.5V to 5.5V and 2mA supply to generate a sound wave every 50ms. This sensor uses 3 protocols i.e. Pulse Width Modulatiom(PWM), ADC, serial communication to output the readings out of which we are using the ADC protocol.

Two ultrasonic sensors are used for this project which detects any obstacle that occurs in the path of the robot. As soon as the obstacle is detected, the robot stops.

DC Motor

The brushed DC motor is the classic motor which is useful for providing high speed and power in a relatively small package. It provides forward and backward movement of the robot. These movements are controlled by the SJOne board using PWM signals which are provided to the motor controller IC.

Servo Motor

Servo Motor is controlled using PWM through wire controls. It can turn 90 degrees in either of the directions for a total of 180 degree movement. It is used to control the steering according to the commands given by the SJOne board. In this project, we are using SG90 Micro servo Motor which is tiny and lightweight with high output power.

Servo Motor

Pin configuration for the servo motor is as follows:

Sl. No	Servo Pin Color	Purpose
1	Brown	Ground
2	Red	VCC (max 4.8 Volts)
3	Yellow	PWM input to motor

Below figure depicts the timing diagram of 1 cycle PWM for servo motor.

Sg90 Servo requires 50 Hz of frequency to drive its shaft. It means that the 1 PWM cycle is 20mS out of which 1 to 2 mS of duty cycle is required to drive the servo.
1mS duty cycle rotates the motor 90 degrees in anti-clockwise direction.
2mS duty cycle rotates the motor 90 degrees in clockwise direction.
1.5mS duty cycle brings the shaft at the center position.

Motor Driver Controller

L298N is a high voltage, high current dual full-bridge driver designed to accept standard TTL logic levels and drive inductive loads like DC and stepping motors. Dual-channel H-bridge Motor Shield is composed of 2 discrete MOSFET H-bridge, designed to drive two DC motor with max current 7.2 A.

H Bridge configuration is used in electrical applications where the load needs to be driven in either direction. The H-bridge has four switching elements at the corners of the H and the motor forms the cross bar. A typical H-Bridge structure is shown below:

In the above figure, if only S1 and S4 switches are closed then the motor rotates clockwise and if S2 and S3 switches are closed then the motor rotates aniticlockwise. L298N is an H-Bridge motor driver IC uses MOSFET transistors for switching purposes. It controls the direction of two motors by driving the current in either polarity. It is controlled by PWM (Pulse Width Modulation).

The directions to the motor are given by the SJOne board through the input pins of L298N and the output is given to the motor through the output pins. The speed of the motor is controlled using PWM which is given to the Motor IC through the Enable pin. A power supply of 5V is given to the IC which drives the the output of the motor.

Hardware Interface

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schematic pin connection table 3 4 lines explain

Software Design

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software description with flowchart algo of each module

Implementation

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system algorithm pics of small implementations like led color when obstacle detected.

Testing & Technical Challenges

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magnetic sensor obstacle accleration staright movement turns

My Issue #1

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Conclusion

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Project Video

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Project Source Code

• Sourceforge Source Code Link

References

Acknowledgement

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References Used

https://cdn-shop.adafruit.com/datasheets/LSM303DLHC.PDF

http://www.nxp.com/files/sensors/doc/data_sheet/MMA8452Q.pdf

https://www.sparkfun.com/datasheets/Wireless/Zigbee/XBee-Datasheet.pdf

https://www.sparkfun.com/datasheets/Components/General/L298N.pdf

http://www.maxbotix.com/documents/LV-MaxSonar-EZ_Datasheet.pdf

https://learn.adafruit.com/lsm303-accelerometer-slash-compass-breakout/overview

Appendix

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