Intelligent vehicles and road transportation systems (ITS) Week 3 : - PowerPoint PPT Presentation

ME470 Intelligent vehicles and road transportation systems (ITS) Week 3 : Positioning and navigation systems and sensors Denis Gingras Winter 2015 D Gingras – ME470 IV course CalPoly Week 3 1 13-janv.-15

Course outline  Week 1 : Introduction to intelligent vehicles, context, applications and motivations  Week 2 : Vehicle dynamics and vehicle modelling  Week 3: Positioning and navigation systems and sensors  Week4: Vehicular perception and map building  Week 5 : Multi-sensor data fusion techniques  Week 6 : Object detection, recognition and tracking  Week 7: ADAS systems and vehicular control  Week 8 : VANETS and connected vehicles  Week 9 : Multi-vehicular scenarios and collaborative architectures  Week 10 : The future: toward autonomous vehicles and automated driving (Final exam) 2 13-janv.-15 D Gingras – ME470 IV course CalPoly Week 3

Week 3 outline  Brainstorming and introduction  Context, history and importance of vehicle positioning in IVs and ITS  Navigation system basic architectures  Coordinate reference frames  Global navigation satellite systems (GNSS)  GPS and GLONASS  Galileo and BeiDou  Inertial navigation systems  Accelerometers  Gyrometers  Compass  Odometers  Vehicle navigation states  Maps and map matching  Vehicle positioning via wireless telecommunications D Gingras – ME470 IV course CalPoly Week 3 3 13-janv.-15

Brainstorming Brainstorming Open questions and introductory discussion What is navigation ? D Gingras – ME470 IV course CalPoly Week 3 4 13-janv.-15 4

Brainstorming Brainstorming Open questions and introductory discussion Define the following words: Positioning, heading, localization, pose, dead reckoning D Gingras – ME470 IV course CalPoly Week 3 5 13-janv.-15 5

Brainstorming Brainstorming Open questions and introductory discussion What is a coordinate reference frame ? Name a few. D Gingras – ME470 IV course CalPoly Week 3 6 13-janv.-15

Brainstorming Brainstorming Open questions and introductory discussion Name a few technologies used for positioning of vehicles. D Gingras – ME470 IV course CalPoly Week 3 7 13-janv.-15

Brainstorming Brainstorming Open questions and introductory discussion Is the position accuracy requirement the same for all intelligent vehicle applications? Explain your answer. D Gingras – ME470 IV course CalPoly Week 3 8 13-janv.-15 8

Brainstorming Brainstorming Open questions and introductory discussion From a systemic point of view, what are the roles of positioning in intelligent vehicles? D Gingras – ME470 IV course CalPoly Week 3 9 13-janv.-15

Brainstorming Brainstorming Open questions and introductory discussion Name a few applications of vehicle positioning and car navigation systems D Gingras – ME470 IV course CalPoly Week 3 10 13-janv.-15 10

Brainstorming Brainstorming Open questions and introductory discussion What are the main building blocks of a in-car navigation system? D Gingras – ME470 IV course CalPoly Week 3 11 13-janv.-15

Brainstorming Brainstorming Open questions and introductory discussion Navigation is much easier since the 1960s and 70s. Why ? D Gingras – ME470 IV course CalPoly Week 3 12 13-janv.-15

Brainstorming Brainstorming Open questions and introductory discussion What is a sensor ? What kind of sensors do we find in IVs? D Gingras – ME470 IV course CalPoly Week 3 13 13-janv.-15 13

Brainstorming Brainstorming Open questions and introductory discussion What makes position estimates and localisation imperfect ? D Gingras – ME470 IV course CalPoly Week 3 14 13-janv.-15 14

A brief history of navigation History Originally, navigation tools were developed for sailors. They could use the following tools: Compass: needle giving the direction of the magnetic North of the Earth. Astrolab: You lined it up so the sun shone through one hole onto another, and the pointer would show your latitude. Quadrant: A sailor would The North see the North Star along Star , also one edge, and where the known as string fell would tell Polaris, helped approximately the ship’s sailors to latitude. figure out their position. Chronometer (Clock) : In 1764, John Harrison created a very accurate chronometer that would keep time at sea. Finally sailors had a tool to measure longitude at sea. D Gingras – ME470 IV course CalPoly Week 3 15 13-janv.-15

A brief history of navigation History Current handheld devices to provide absolute position of the vehicle Mission Localization Navigation D Gingras – ME470 IV course CalPoly Week 3 16 13-janv.-15

Reference Reference frames frames To achieve navigation in a general way; a coordinate system is needed that allow quantitative calculations (dixit Claudius Ptolemy, ~130AD) A Reference Frame describes the coordinate system basis deploying the space in which we navigate. The definition of a 3D set of axes requires: An origin (3 quantities) An orientation (3 quantities) A scale (1 quantity) (A “ Helmert ” transformation estimates these 7 quantities to relate two reference frames). For the Earth: Terrestrial frames come in two forms: Geometric (mathematical description) Potential field based (gravity and magnetic) D Gingras – ME470 IV course CalPoly Week 3 17 13-janv.-15

Reference Reference frames frames To navigate, one needs coordinates set-up in a reference frame. Several reference frames have been proposed, however three frames are typically used in intelligent vehicle positioning applications: 1) The Global frame , denoted E, called the Earth-Center, Earth-Fixed (ECEF) frame where the origin is at the center of mass of the earth; is used as the reference frame in the position estimation framework; 2) The Navigation frame , denoted N, which coincides with a local tangent frame with axes pointing along North, East, and Down (NED), is used to describe the trajectory in a results which is easier for human to process; 3) The Body frame is used to represent the sensor suite coordinates embedded in the vehicle. D Gingras – ME470 IV course CalPoly Week 3 18 13-janv.-15

Reference Reference frames frames ECEF Simple Global Reference Frame Z  Geometric: Origin at the center of mass of the Earth; Orientation defined by a Z-axis near the Greenwich rotation axis; one “Meridian” Meridian (plane containing the Z-axis) Center of Mass defined by a convenient location such as Greenwich, England. Y  Coordinate system would be X Cartesian XYZ. D Gingras – ME470 IV course CalPoly Week 3 19 13-janv.-15

Reference Reference frames frames Conventional coordinate system in navigation  Until the mid-1950s, we used conventional coordinate systems (CCS) which rely on the direction of the gravity vector of the Earth. We had 2 different systems: A horizontal one (how far away is something) and a vertical one (height differences between points).  Conventional coordinate systems are a mix of geometric systems (geodetic latitude and longitude) and potential based systems (orthometric heights). The origin of conventional systems are also poorly defined because determining the position of the center of mass of the Earth was difficult.  Therefore, CCS were much more complicated to use than the simple global reference frame we use today. But how come this is simpler today ? Do you know why ? D Gingras – ME470 IV course CalPoly Week 3 20 13-janv.-15

Reference Reference frames frames The global reference frame and the vehicle reference frame are represented by XgOgYg and XvOvYv , respectively. Vehicle pose is expressed by ( x, y, θ ) in the global reference frame, representing the position and orientation of a vehicle. The relationship between the global coordinates ( x g , y g ) and vehicle coordinates ( x v , y v ) of feature point P , can be expressed by: D Gingras – ME470 IV course CalPoly Week 3 21 13-janv.-15 21

State space model for positioning History In the next few slides we will look at a general state space model for the vehicle position and velocity relating it to the on-board proprioceptive measurements. We distinguish two kinds of sensors: Attitude sensors Compasses and gyroscopes: provide angular and or angular velocity informations defining the attitude of the vehicle with respect to a fixed external global reference frame. Linear displacement sensors Accelerometers and wheel odometers: provide information about the longitudinal acceleration velocity and distance travelled of the vehicle with respect to an internal body frame. D Gingras – ME470 IV course CalPoly Week 3 22 13-janv.-15

State space model for positioning History Vehicle global position measured in the external frame:   T  x x y z E E E E Vehicle linear velocity along each coordinate of the external frame   T      x x y z E E E E Vehicle linear velocity along each coordinate of the body frame   T  v v v v b b b b Heading (yaw) pitch and roll angles measured in the body frame frame   T      b b b b Heading (yaw), pitch and roll angular velocities measured in the body frame T              b b b b D Gingras – ME470 IV course CalPoly Week 3 23 13-janv.-15