Embedded Motion Control 2014 Group 1

Group Info

Name:	Student id:	Email:
Groupmembers (email all)
Sander Hoen	0609581	s.j.l.hoen@student.tue.nl
Marc Meijs	0761519	m.j.meijs@student.tue.nl
Wouter van Buul	0675642	w.b.v.buul@student.tue.nl
Richard Treuren	0714998	h.a.treuren@student.tue.nl
Joep van Putten	0588616	b.j.c.v.putten@student.tue.nl
Tutor
Sjoerd van den Dries	n/a	s.v.d.dries@tue.nl

Meetings

Weekly meetings are planned during the course. Every Wednesday a standard meeting is planned to discuss progress with the group and with the tutor. Presentations from these weekly meetings can be found with the presentation links below. Important meeting decissions can be found with use of the meeting liks below. Next to the standard weekly meetings evening meetings are planned to work as a group on the software design.

1. Meeting - 2014-05-02
2. Meeting - 2014-05-12
3. Meeting - 2014-05-14
4. Meeting - 2014-05-15
5. Meeting - 2014-05-16
6. Meeting - 2014-05-21
7. Meeting - 2014-05-23
8. File:Presentatie week 3.pdf
9. File:Presentation week 4.pdf

Time Table

Fill in the time you spend on this course on Dropbox "Time survey 4k450.xlsx"

Planning

Week 1 (2014-04-25 - 2014-05-02)

• Installing Ubuntu 12.04
• Installing ROS
• Following tutorials on C++ and ROS.
• Setup SVN
• Plan a strategy for the corridor challenge

Week 2 (2014-05-03 - 2014-05-09)

• Finishing tutorials
• Interpret laser sensor
• Positioning of PICO

Week 3 (2014-05-10 - 2014-05-16)

• File:Presentatie week 3.pdf
• Starting on software components
• Writing dedicated corridor challenge software
• Divided different blocks
  • Line detection - Sander
  • Relative distance - Richard
  • Drive - Marc
  • Situation - Wouter
  • State generator - Joep

Week 4 (2014-05-17 - 2014-05-25)

• File:Presentatie week 4.pdf
• Finalize software structure maze competition
• Start writing software for maze competition

Week 5 (2014-05-26 - 2014-06-01

• Test first maze competition software in practice
• Determine bottlenecks for maze competition
• Start with arrow detection
  • Arrow detection - Wouter

Software architecture

We decided to use a architecture as shown in the following figure:
THIS FIGURE HAS TO BE ADAPTED!!!

I/O structure

The different components that are visualized in the software architecture scheme are elaborated here

Node	Subscibes topic:	Input	Publishes on topic:	Output	Description
Line detection	/pico/laser	Laser scan data	/pico/line_detection	Lines consisting out of start and end point [math]\displaystyle{ (x_1,y_1),(x_2,y_2) }[/math] etc.	Transformation of raw data to lines with use of the Hough-transform
Arrow detection	/pico/camera	Camera images	/pico/vision	Arrow detected to the left of the right	Detection of arrows pointing to left or right.
Odometry	/pico/odom	Quaternion matrix	/pico/yaw	float with yaw angle	Transform Quaternion in roll, pitch and yaw angles. Only yaw angle is send because roll and pitch are zero.
Distance	/pico/line_detection	Line coordinates	/pico/dist	[math]\displaystyle{ (y_{left}, y_{right}, x, \theta_{left}, \theta_{right}) }[/math] also known as'relative position'	Determine distance to wall to left, right and front wall. Also determines angle left and right with respect to the walls.
Drive	/pico/state /pico/dist	[math]\displaystyle{ (y_{left}, y_{right}, dy, }[/math] [math]\displaystyle{ x, dx, \theta_{left}, \theta_{right},d\theta) }[/math]	/pico/cmd_vel	Pico moving	Move pico in the desired direction
Situation	/pico/line_detection /pico/laser /pico/vision	Line data, vision interpretation and possibly laser data.	/pico/situation	The situation where pico is in. For example corridor to the right, T-junction, etc.	Situation parameters.
State generator	/pico/situation /pico/yaw	Situation and yaw angle of Pico.	/pico/state	[math]\displaystyle{ dx,dy, d\theta }[/math]	Based on the situation Pico needs to go through different states and continue to drive. Every state defines an action that Pico needs to do.

PICO messages

The different nodes are communicating with each other by sending Messages. Each nodes sends a set of messages with use of a publisher. The Message that are sends between the nodes are defined in this section.

Line

The line message includes two points, p_1[math]\displaystyle{ =(x1,y1) }[/math] and p_2[math]\displaystyle{ =(x2,y2) }[/math], which are defined by the geometry messages package. A point consists of (x,y,z) coordinate. For points [math]\displaystyle{ p_1 }[/math] and [math]\displaystyle{ p_2 }[/math] the z-coordinate is set to zero.

   geometry_msgs/Point32 p1                                                        
   geometry_msgs/Point32 p2

Line detection

inputs: --
function: transformation of raw data to lines by use of hough-transform
output: lines consisting out of start and end point (x_1,y_1),(x_2,y_2) etc.

convert laser data to points (x,y)
use hough transform
filter lines

data output format: (richard + sander)

topic: /pico/lines

msg: lines

---

Arrow detection

Relative distance

input topic: /pico/lines
function: Determine distance to wall to left, right and front wall. Also determines angle theta with respect to the corridor.
output: (Y_left, Y_right, X, theta)
output topic: /pico/dist

msg: dist


The angle theta can be calculated with the next fomula:

[math]\displaystyle{ \theta = atan((y2-y1)/(x2-x1)) }[/math]

the position perpendicular to the line/wall is calculated with the next formula:

[math]\displaystyle{ X_r = x2 - ((y2-y1)/(x2/x1))*y2*sin(\theta_1) }[/math]

[math]\displaystyle{ X_l = x4 - ((y4-y3)/(x4/x3))*y4*sin(\theta_2) }[/math]

theta is average of left and right or only left or right depending on situation

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Drive

This node sends velocity commands to Pico based on input from the state generator node and relative position node. The state generator node sends a velocity in x and theta based on the state it is in. The relative position node sends the distance and angle relative to the left and right wall with Pico as the centre. When possiblethis information is used for the orientation and positioning of Pico.

---

Situation

inputs: lines, vision, relative position

Two different approaches are taken into account, a simple approach in which only is detected if the left, front and right side of pico are 'free' of walls/obstacles. But also a more elaborate approach in which situations are detected like, junctions, T-junctions, crossings and dead ends.

Lines can be categorized in two types of lines:
Longitudinal lines: y-coordinates of begin and end point are similar
Lateral lines: x-coordinates of begin and end point are similar

Situations to be recognized:

- inbetween two walls
No obstacles in front, no lateral line detected within X meter.
2 longitudinal lines are detected.

- Junction
3 lines are detected. From which two are longitudinal lines and one is lateral within (X meter).
Detect direction of juction by comparing the x -values of the longitudinal lines with the x-value of the lateral line.
Left junction: When the x value of the left line (the line with the smallest Y values) is 'minimum corridor width' smaller then the x value of the lateral line a gap on the left side is recognized.
Right junction: When the x value of the right line (the line with the smallest Y values) is 'minimum corridor width' smaller then the x value of the lateral line a gap on the left side is recognized.

- Dead end
3 lines are detected. From which two are longitudinal lines and one is lateral within (X meter).
Detect direction of dead end by comparing the x -values of the longitudinal lines with the x-value of the lateral line. When the x values of both longitudinal lines are similar to those of the lateral line a dead end can be recognized.

- T junction: 3 situations named T-right, T-left, T-right-left.
T-right: 3 longitudinal lines are detected, 1 lateral lines detected on the right side of pico.
T-left: 3 longitudinal lines are detected, 1 lateral lines detected on left side of pico.
T-right-left: 2 longitudinal lines are detected: 4 lateral lines are detected

- X junction
4 longitudinal and 4 lateral lines are detected

---

State generator

input: Situation, relative position
input topic: /pico/sit

function: Create setpoint for position of pico by use of state. (determine wanted position and speed).
output:
output topic: /pico/

msg:

PICO states corridor challenge

For the robot, the internal states can be visualized as in the following figure: