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Quad-Copter

Quad-Copter. Group 3 Fall 2010. David Malgoza  Engers F Davance Mercedes               Stephen Smith Joshua West. Project Description. Design a flying robot Robot must be able to: Autonomously Fly Communicate Wirelessly Wireless Manual Control. Project Motivation.

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Quad-Copter

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  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

  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

  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 • Analog output

  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_Adjeffectively 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);

  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(structPID_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){ yaw_temp -= 3600; 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 MaxbotixLV-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. Goals/Objectives • Able to produce PWM signal • Send/Receive UART signals • Hardware ADCs not just comparators • I2C capability • 16-bit timers with 4 output compare registers • 2 UART ports • 8 ADC ports (minimum 10-bit accuracy) Specifications/Requirements

  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 Constants

  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();

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