Quadcopters A CEV Talk

Agenda Flight PreliminariesWhy Quadcopters The Quadcopter SystemStability: The NotionSensors and FusionControl AlgorithmsThe Way Ahead

Flight Preliminaries

4 movements Altitude – Up – Down Roll – Left – Right Pitch – Front – Back Yaw – Heading

Altitude Hover

Altitude Up

Altitude Down

Roll

Pitch

Quick question Correct Wrong

Yaw

Why Quadcopters?

Flight is fun!

Simplicity

However Scaling up, 4 Simple Mechanisms 1 Relatively complex mechanism

4 rotors 4 rotors harder to control than one

Nevertheless Mechanical Simplicity + Electronic Stabilization win

Perks Less stable = learn more control theory. Less kinetic energy per motor(rotor). You wont lose your fingers.

Done Flight Preliminaries Done Why Quadcopters The Quadcopter SystemStability: The NotionSensors and FusionControl AlgorithmsThe Way Ahead Agenda

The Quadcopter System [Q]

Open Loop

Stability: The Notion Mind SenseTake action

Done Flight Preliminaries Done Why Quadcopters Done The Quadcopter System Done Stability: The NotionSensors and FusionControl AlgorithmsThe Way Ahead Agenda

Inertial Measurement Unit (IMU) IMU AccelerometerGyroscope

Angle calculation: Accelerometer Inclination from an axis can be calculated using the component of gravity along that particular axis.

Angle calculation: Gyroscope Gyroscopes provide angular rate in degrees per second. The angle with a certain axis can be calculated by integrating the angular velocity with respect to that axis over the sampling period.

IMUs are not perfect! Accelerometers : When in motion, the acceleration of the robot affects the acceleration measured by the accelerometer. Gyroscopes : Due to manufacturing limitations, signal drift often accompanies MEMS gyros. When integrated over time, this drift leads to considerable error.

Complementary filter Simplest filter for IMUs Corrects Gyro drift by including a certain component of angle measured by the accelerometer in angle measurement Angle= 0.98*(Gyroscope Angle) *(Accelerometer angle)

Kalman filter

Done Flight Preliminaries Done Why Quadcopters Done The Quadcopter System Done Stability: The Notion Done Sensors and FusionControl AlgorithmsThe Way Ahead Agenda

Control Algorithms

Proportional-Integral-Derivative : An Intuition P roportional term generates output based on error I ntegral term generates output based on bias in error D erivative term generates output based on speed of error variation Mathematical procedures to tune PID constants (very hard work): -- Root locus method -- Bode plots -- Nyquist Criterion -- Zeigler Nicols Algorithm Method which usually works: -- Trial and Error (video)

Inside The Controller Set point Filtering and Data fusion PID error Control signals for ESC, which will in turn command motors Computed Angles Measured Angular rates And acceleration

The Closed Loop Quadcopter dynamics Sensors Controller

Done Flight Preliminaries Done Why Quadcopters Done The Quadcopter System Done Stability: The Notion Done Sensors and Fusion Done Control AlgorithmsThe Way Ahead Agenda

Onward we fly…

Quads in aerial photography, delivery systems, search and rescue…

Onward we fly… Better (Nonlinear) Control Accurate estimators SLAM Motion Planning

Better Control Non linear control (V) Robust control Adaptive control Stochastic control

Better Control

Accurate Estimators Implementing Extended Kalman filter Third order stochastic filter Multi state constraint Kalman filter for vision aided navigation

So Far So Good Hardware Stability Movement Interaction?

Quad’s eye view What does the world look like? [MAPPING] Where am I? [LOCALIZATION] A chicken and Egg problem

Some Statistics Vijay Kumar labs – 7 post doctoral researchers – 5 Research scientists – 17 Ph.D. students – Needless to mention masters and undergraduate students Raffaello D’ Andrea (Q) – 17 research students and professors working together

Research Exploration Investigation Experimentation Inquest Fact finding Analysis

“There’s an infectious feeling within us that research can solve almost any problem..” “There’s an infectious feeling in Stanford that innovation can solve almost any problem..”[Q]

Robotics EC Mechanical Engg Computer Science Electrical Engg

Internships Areas of interest – Control Algorithms – State Estimation – SLAM December 11 th to 26 th [tentative] 6 to 12 interns – 3 Paid Link at