Quad-Copter

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Quad-Copter

• Group 3
• Fall 2010

David Malgoza  Engers F Davance Mercedes         
     Stephen Smith Joshua West
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Project Description

• Design a flying robot
• Robot must be able to
• Autonomously Fly
• Communicate Wirelessly
• Wireless Manual Control

3
Project Motivation

• The Big Question, WHY?
• Wanted to design an aerial vehicle with
  autonomous features
• Wanted to do a project with fair amount of
  hardware and software
• Most of all wanted to do something cool and fun!

4
Project Overview

• To do this we must
• Design and code a control system for the
  Quad-Copter (move up, take-off, etc)
• Design and code a sensor fusion algorithm for
  keeping the copter stable
• Design and build a power distribution system
• Design and build a chassis

5
Goals/Objectives

• FLY
• The Quad-copter must be able to remain stable and
  balance itself.
• The copter must be able to rise and descend
• The copter must be able to signal when power is
  running low (audible and visual)

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Specifications/Requirements

• Lift at least 2 kg of mass
• Must be able to hover at least 6 inches from the
  ground
• The Quad-Copter must communicate wirelessly at
  least 100m
• The Quad-Copter must be able flight for a minimum
  of 5 minutes (battery power)

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Quad-Copter Concept
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Frame
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Frame

• Goals
• Create a lightweight chassis for the Quad-Copter
• The chassis must support all batteries, external
  sensors, motors, and the main board
• Cost Effective
• Requirements
• Create a chassis with a mass of 800g or less
• The area the Quad-Copter cannot exceed a radius
  of 18in.
• Must be able to support at least a 1.2kg load

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Materials Comparison

• There were 2 lightweight materials we considered
  for the chassis Aluminum and Carbon Fiber
• Both have capabilities of being entirely used as
  a chassis and meet the maximum mass requirements

Carbon Fiber Aluminum
Advantages Excellent Strength and Stiffness. Durable. Easily Replaceable. Less Costly.
Disadvantages Can chip or shatter. More costly. Can easily bend or dent.
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Design of Frame

• 2 aluminum square plates will be used as the main
  structural support
• 4 rods will be screwed to the top square plate at
  and secured at the corners
• Below the plate, two additional aluminum rods
  will be used to support the battery. Landing gear
  will be shaped as standard helicopter legs.
• 4 coat hangers will be used as landing gear.

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Diagram of Frame
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Motors/ESC
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Motors

• Goals
• To use lightweight motors for flight
• The motors must be cost effective
• Requirements
• Use motors with a total mass of 300g
• Each motor must be able to go above 2700 rpm
• Each motor is to be controlled via PWM signal
  from the processor

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Brushless Motor

1. Advantages
2. Less friction on the rotor
3. Typically faster RPM.
4. PWM or I2C controlled by an electronic speed
   control (ESC) module.
5. Disadvantages
6. Require more power.
7. Sensorless motors are the standard
8. Typically more expensive

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TowerPro 2410-09Y BLDC

• Minimum required voltage 10.5V
• Continuous Current 8.4A
• Maximum Burst Current 13.8A
• Mass 55g
• Speed/Voltage Constant 840 rpm/V
• Sensorless ESC required for operation.

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Sensorless ESC

• The ESC translates a PWM signal from the
  microprocessor into a three-phase signal,
  otherwise known as an inverter.
• Based on a duty cycle between 10 and 20, the
  ESC will have operation.
• Based on the requirements given by the
  manufacturer, the PWM frequency will be 50Hz.

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Power Supply System
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Power

• Goals and Objectives
• The ability to efficiently and safely deliver
  power to all of the components of the quadcopter
• Requirements
• The total mass of the batteries should be no more
  than 500g
• A total of 3 low-power regulators are to be used
• Must be able to sustain flight for at least 1
  minute

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Power Distribution
9V Battery
Digital Compass
LM7805
GPS
Main Processor
LD1117V33
Wireless Processor
Transceiver
11.1V LiPo
Motor
LM317
Ultrasonic
Motor
Ultrasonic
Motor
Gyroscope
Accel.
Motor
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LiPo Battery

• Specifications on the EM-35
• Rated at 11.1V
• Charge Capacity 2200mAH
• Continuous Discharge 35C, which delivers 77A,
  typically.
• Mass 195g

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Logic Converter

• Allows for step-up and step-down in voltage when
  data travels between a lower referenced voltage
  signal to a higher referenced voltage signal.
• This will be used to communicate the GPS and the
  wireless communication system with the main
  processor

Source http//www.sparkfun.com/commerce/product_info.php?products_id8745
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Sensors
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Sensor Subsystems/Functions

• Flight stability sensors
• Monitor, correct tilt
• Direction/Yaw sensor
• Maintain stable heading, establish flight path
• Proximity sensors (future application)
• Detect obstacles, ground at low altitude
• Navigation/Location sensor (future application)
• Monitor position, establish flight path
• Minimize cost and weight for all choices

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Flight Stability Sensors

• Goals/Objectives
• A sensor system is needed to detect/correct the
  roll and pitch of the quad-copter, to maintain
  a steady hover.
• Specifications/Requirements
• Operational range 3.0 3.3 V supply
• Weigh less than 25 grams
• Operate at a minimum rate of 10 Hz

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Flight Stability Sensors

• Options (one or more)
• Infrared horizon sensing
• Expensive, unpractical, interesting
• Magnetometer (3-axis)
• Better for heading than tilt, little expensive
• Accelerometer
• Measures g-force, magnitude and direction
• Gyroscope
• Measure angular rotation about axes

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Flight Stability Sensors

• IMU (Inertial Measurement Unit)
• Combination of accelerometer and gyroscope
• ADXL335 - triple axis accelerometer (X, Y, Z)
• Analog Devices
• IDG500 dual axis gyroscope (X and Y)
• InvenSense
• 5 DoF (Degrees of Freedom) IMU
• Sensor fusion algorithm
• Combines sensor outputs into weighted average
• More accurate than 1 type of sensor

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IMU Hardware

• ADXL335 - triple axis accelerometer
• /- 3 g range adequate
• 50 Hz bandwidth adequate, adjustable
• 1.8 3.6 V supply
• Analog output
• IDG500 dual axis gyroscope
• Measures /- 500 º/s angular rate
• 2 mV/deg/s sensitivity
• 2.7 3.3 V supply
• Analog output

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ADXL335 PCB Layout

• Surface mount soldered to main PCB
• 3.3 V supply filtered by .1µf cap
• .1µf caps at C2, C3, C4 that filter gt 50Hz
• X, Y, Z outputs to MCU A/D converters
• S1 self test switch

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IDG500 Board Layout

• Soldered to main PCB
• 3.0V supply
• X Y gyro outputs with low pass filter, to A/D
• C5-C6 for internal regulation

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IMU Code

• Get sensor data from ADCs
• accelROLL convertADC(4)
• accelPITCH convertADC(5)
• accelYAW convertADC(6)
• gyroROLL convertADC(0)
• gyroPITCH convertADC(1)
• Find adjustments for each axis (accelerometer)
• Motor_Adj_Y PID(Y, anglePITCH, 504, G_dt)
• Motor_Adj_X PID(X, angleROLL, 502, G_dt)

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IMU Code

• Find an adjustment based on the magnitude and
  direction of the gyro data that is used to dampen
  movement/ inertia about the axes
• Gy_Adj gyroPITCH - 418
• Gx_Adj gyroROLL - 417
• Gy_Adj Gy_Adj / gyro_divisorY // 3
• Gx_Adj Gx_Adj / gyro_divisorX // 3

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IMU Code

• Gy_Adj effectively dampens oscillations of the P
  term of the PID loop by acting in opposition to
  it
• MOTOR_R (int)limitRange((hover_speed idkno2
  yawAdj - Motor_Adj_Y - Gy_Adj),560,800)

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Direction sensor (Compass)

• Goals/Objectives
• Establish an external reference to direction
• For maintaining a stable heading, turning,
• The module should not suffer from excessive
  magnetic interference (compass)
• The module should be placed away from interfering
  fields and metals (compass)
• Specifications/Requirements
• Accurate to within 3 degrees

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HMC6352 Compass Module

• 3.3 V supply
• I 2Cserial interface
• .5 degree resolution
• 1 to 20 Hz adjustable update rate advertised but,
  higher update rate difficult to encode with
  current hardware layout.

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HMC6352 Compass Module

• In coding the I2C interface for the HMC6352, a
  data update rate of only 2 Hz. was achieved
• As a result, the Yaw_PID function produced a
  loose heading.
• This limitation was addressed by adding a
  dampening term (to the P term).

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HMC6352 Code

• Yaw PID function using compass
• float YAW_PID(struct PID_Data PID_Status, float
  value, float desiredValue, float yaw_dt)
• float error, temp, dTerm, yaw_temp 0.0
• yaw_temp desiredValue - value
• if (yaw_temp lt -1800)
• yaw_temp 3600
• error yaw_temp

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HMC6352 Code

• Yaw_PID (cont)
• else if (yaw_temp gt 1800)
• yaw_temp - 3600
• error yaw_temp
• else
• error yaw_temp
• dTerm PID_Status-gtD((PID_Status-gt
  lastError - error))
• temp (PID_Status-gtPerror dTerm)
• PID_Status-gtlastError error
• return temp

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Proximity Sensors (future application)

• Bottom and forward sonar application using the
  MaxbotixLV-EZ2 ultrasonic sensor
• Detect the ground at 1-15 feet
• Obstacles 30 arc forward 1- 8 feet
• 6 inches resolution

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GPS - future application

• Goals/Objectives
• Needed for autonomous flight mode
• The system could establish an external reference
  to position (latitude and longitude)
• The system would have a serial output
• Should be compact, requiring minimal external
  support (internal antenna)
• Requirements/Specifications
• The system would need to be accurate to within 3
  meters (latitude and longitude).
• The update rate should be at least 1Hz.

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Microcontroller
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Goals/Objectives

• Able to produce PWM signal
• Send/Receive UART signals
• Hardware ADCs not just comparators
• I2C capability

Specifications/Requirements

• 16-bit timers with 4 output compare registers
• 2 UART ports
• 8 ADC ports (minimum 10-bit accuracy)

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ATmega2560 Specs

• 0 16Mhz _at_ 4.5 5.5 volts
• 256 KB Flash memory
• 4 KB RAM
• 4 16-bit timers
• 16 10-bit ADC
• 4 UART
• TWI (I2C)

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Microcontroller Information

• The main MCU will be programmed through the SPI
  pins using the AVRISP-MKII.
• AVRStudio 4.18 is the IDE that will be used for
  development
• The main MCU will be responsible for the
  obtaining sensor data, updating the control
  system, and talking to the wireless communication
  unit

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Code
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Code Linear Control System

• struct PID_Data
• float P
• float I
• float D
• float lastError
• float integratedError
• void initPID(struct PID_Data PID_Status, float
  kp, float ki, float kd)
• float PID(struct PID_Data PID_Status, float
  value, float desiredValue, float dt)
• In addition to this the gyro is used to slow down
  the momentum of the Quad-Copter.

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PID Loop

• error desiredValue - value
• PID_Status-gtintegratedError errordt
• dTerm PID_Status-gtD((error)/dt)
• (PID_Status-gtPerror PID_Status-gtIPID_Status-gti
  ntegratedError dTerm)

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Testing the PID

• Trail and error
• The Ziegler-Nichols method
• Center of gravity
• The testing procedure is as follow
• Isolate an axis
• Increase P gain until oscillation occur
• Increase D gain until it dampens the oscillation
• Increase the effect of the gyro to slow the speed
  of rotation
• Increase I just enough so that it corrects steady
  errors slowly.

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PID Controller Constants
Kp Ki Kd
X-Axis 1.809 0.0699 -0.0409
Y-Axis 1.809 0.1099 -0.0429
Yaw 0.1 0 0
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Code Motor Control

• A PWM signal will be produced by the MCU to
  control the motors
• Once the PWM signal is setup, they run
  independent of the MCU
• Functions
• initPWM( )
• updateMotor()

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Code Analog Sensors

• The ADC will be used to retrieve data from the
  sensors.
• A switch statement will be used to gather data
  correctly
• Functions
• initADC ( )
• convertADC(uint8_t value)

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Code Digital Sensors

• I2C will be used to retrieve data from the
  compass
• MCU master
• Compass slave
• Functions
• initI2C( )
• ISR(TWI_vect)

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Code Communication

• UART is going to be used to retrieve data from
  GPS module and send/receive data from the
  wireless communication module
• Functions
• UART_Setup( )
• ISR(USART0_RX_vect)
• ISR(USART0_TX_vect)
• ISR(USART2_RX_vect)
• ISR(USART2_TX_vect)

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Code C GUI

• C will be used for coding the GUI
• Standard Libraries for serial port communication
• Easy to learn
• Function of GUI
• Retrieve sensor data and display to user

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Code Overview
Compass
I2C
Wireless Comm
UART
IMU
PWM
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Wireless Communication
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Requirements

• Work on the 2.4 GHz band.
• Data rate of minimum 56 Kbs.
• To have a range of 100 meters.
• To cost less than 70.

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Xbee Module

• The Xbee module is a Zigbee compatible device.
• Zigbee meets all the requirements of the wireless
  communication.
• Xbee will be used to control and get status
  messages from the Quad-Copter.
• Xbee modules can be setup as end device or
  coordinator.

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Xbee Setup

• PANID This is the ID of the network
• MY Is the 16 bit address of the source device
• DL Is the 16 bit address of the destination
  device.
• A1 Register that controls who the end device can
  talk to.
• A2 Register that controls how the Coordinator
  manages the network.

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Xbee A1 Register

• A1 has three bits that decide how the end device
  connects to a network
• bit0 if set it will allow the end device to join
  any network
• bit1 if set it the end device will allow the
  channel to be change by a coordinator
• bit2 if set the end device will try to auto
  associate.

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Xbee A2 register

• A2 has three bits that decide how the coordinator
  manages a network
• bit0 if set it will allow the coordinator to
  look for a free PANID
• bit1 if set it will allow a coordinator to
  change the end devices channel
• bit2 if set the coordinator will allow end
  devices to associate to it.

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PCB Hardware Layout
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Requirements

• Must be able to mount the MCU, the wireless
  system, and the IMU components
• For easy plug-and-play, the level logic
  converters are to be mounted for all UART
  connections
• Power distribution for the digital section of the
  board is to be distributed using a star design
• IMU components must be relative central to the
  Quad-Copter for the most accurate readings
• Male header pins are to be used for connecting to
  all external components
• Due to time and cost, through-hole parts are
  preferred for all passive components

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Main Board - Initial
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Modifications

• Design flaws in the schematic for the level logic
  converters created a setback in implementing UART
  devices were fixed.
• All voltage regulators are connected to the main
  power lines to prevent voltage dropout effects
• All regulators were exchanged to TO-220 packaging
• Xbee module is mounted.

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Main board - Final
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Project Management
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Project Distribution
Subsystem Responsible
Main Software Josh
Linear Control System Engers
Frame All
Motors David
Power Supply David
Microcontroller Josh
Sensors Steve
Wireless Communication Engers
Video System Steve
PBC Board All
Autonomous Algorithm All
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Project Finance

• Goal was to be under 700
• Unfortunately the group did not meet this goal.
• Estimated spent 1500.00
• Reason Underestimated the amount of parts that
  would need to be replaced and shipping costs

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Problems

• I2C not working on main board
• Fix Use another MCU that it was tested with

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Problems

• Accelerometer is susceptible to vibration noise
• The vibration from the motors induces oscillation
  on the accelerometer.
• Fix Use a software low-pass filter
• y(nT) y(nT T)
• (dt/(dt RC))(x(nT)-y(nt-T)

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Problems

• Sensor fusion algorithms not working.
• Starlinos sensor fusion algorithm would get
  stuck on a angle.
• Kalman filter would get stuck on a angle.
• Fix Instead of using a combination of
  accelerometer and gyro to get a better estimate
  of position, we used the accelerometer value and
  passed it through a low pass filter.

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Problems

• Grounding on our first PCB was problematic.
• Fix Designed a new PCB with wider ground traces

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• Questions, Comments, Concerns?