1. Quad-Copter Group 3 Fall 2010 David Malgoza Engers F Davance Mercedes
Stephen Smith
Joshua West

2. 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)

6. 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)

7. Quad-Copter Concept

8. Frame

9. 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

10. 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.

11. 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.

12. Diagram of Frame

13. Motors/ESC

14. 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

15. Brushless Motor Advantages Less friction on the rotor
Typically faster RPM.
PWM or I2C controlled by an electronic speed control (ESC) module.
Disadvantages
Require more power.
Sensorless motors are the standard
Typically more expensive

16. 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.

17. 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.

18. Power Supply System

19. 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

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

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

22. 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:

23. Sensors

24. 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

25. 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

26. 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

27. 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

28. 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

29. 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 > 50Hz
X, Y, Z outputs to MCU A/D converters
S1 self test switch

30. 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

31. IMU Code Get sensor data from ADC’s:
accel[ROLL] = convertADC(4);
accel[PITCH] = convertADC(5);
accel[YAW] = convertADC(6);
gyro[ROLL] = convertADC(0);
gyro[PITCH] = convertADC(1);
Find adjustments for each axis (accelerometer):
Motor_Adj_Y = PID(&Y, angle[PITCH], 504, G_dt);
Motor_Adj_X = PID(&X, angle[ROLL], 502, G_dt);

32. 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 = gyro[PITCH] - 418;
Gx_Adj = gyro[ROLL] - 417;
Gy_Adj = Gy_Adj / gyro_divisorY; // 3
Gx_Adj = Gx_Adj / gyro_divisorX; // 3

33. 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 + idkno yawAdj - Motor_Adj_Y - Gy_Adj),560,800);

34. 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

35. 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.

36. 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).

37. 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 < -1800)
yaw_temp += 3600;
error = yaw_temp;
} …

38. HMC6352 – Code Yaw_PID (cont) else if (yaw_temp > 1800){
error = yaw_temp;}
else
error = yaw_temp;
dTerm = PID_Status->D*((PID_Status-> lastError - error));
temp = (PID_Status->P*error + dTerm);
PID_Status->lastError = error;
return temp; }

39. Proximity Sensors (future application)
Bottom and forward sonar application using the Maxbotix LV-EZ2 ultrasonic sensor
Detect the ground at 1-15 feet
Obstacles 30˚ arc forward 1- 8 feet
6 inches resolution

40. 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.

41. Microcontroller

42. Specifications/Requirements
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)

43. ATmega2560 Specs 0 – 16Mhz @ 4.5 – 5.5 volts 256 KB Flash memory
4 KB RAM
4 16-bit timers
16 10-bit ADC
4 UART
TWI (I2C)

44. 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

45. Code

46. 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.

47. PID Loop error = desiredValue - value;
PID_Status->integratedError += error*dt;
dTerm = PID_Status->D*((error)/dt);
(PID_Status->P*error + PID_Status- >I*PID_Status->integratedError + dTerm);

48. 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.

49. PID Controller ConstantsKp Ki Kd
X-Axis
1.809
0.0699
Y-Axis
0.1099
Yaw
0.1

50. 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();

51. 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);

52. Code: Digital Sensors
I2C will be used to retrieve data from the compass
MCU – master
Compass – slave
Functions:
initI2C( );
ISR(TWI_vect);

53. 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);

54. 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

55. Code: Overview IMU PWM Compass Wireless Comm I2C UART UART PIDs Update
ADCs
IMU
PWM

56. Wireless Communication

57. 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.

58. 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.

59. 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.

60. 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.

61. 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 device’s channel
bit2: if set the coordinator will allow end devices to associate to it.

62. PCB Hardware Layout

63. 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

64. Main Board - Initial

65. 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.

66. Main board - Final

67. Project Management

68. Wireless Communication
Project Distribution
Subsystem
Responsible
Main Software
Josh
Linear Control System
Engers
Frame
All
Motors
David
Power Supply
Microcontroller
Sensors
Steve
Wireless Communication
Video System
PBC Board
Autonomous Algorithm

69. Project Finance Goal was to be under $700
Unfortunately the group did not meet this goal.
Estimated spent: ~$
Reason: Underestimated the amount of parts that would need to be replaced and shipping costs

70. Problems I2C not working on main board
Fix: Use another MCU that it was tested with

71. 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)

72. Problems Sensor fusion algorithms not working.
Starlino’s 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.

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

74. Questions, Comments, Concerns?