Mechanical Department RoboCup 19 September, 2005 The University of Adelaide Copyright © 2005Slide Number 1 David Jackson Nathan Simmonds Robert Stewart

19 September, 2005 The University of Adelaide Copyright © 2005 Slide Number 1

Mechanical Department RoboCup

David JacksonNathan Simmonds

Robert StewartSupervisor: Dr. Frank Wornle



RoboCup Organisation

Research initiative in the fields of robotics and artificial intelligence Soccer environment includes friendly, neutral and adversarial agents RoboCup aim: To beat the human world champions by 2050

(www.robocup.org)



Project Aim

To develop skills such as ball collection, obstacle avoidance and kicking

Intelligence SystemDecision making algorithmsPath Planning

Vision Processing

Camera Motors

Controller

KickerCamera



A

xa

Robot Body

B

xb

Vision System

Rotationally symmetric, three-part mirror with a camera for 360° vision

x

Sensor

y

Robot Body

C

xc



Constant Curvature Discontinuity

y

x

Image continuity is not preserved Vision of the constant curvature

section overlaps the isometric This error was caused by an

assumption made about the camera focal length

Maximum range: 8.5m



Vision Calibration

CMVision – Classifies pixels as a YUV colour CMVision returns pixel information of colour regions Obtaining the physical distance of an object requires mirror calibration Obtain the pixel distance and map this to the measured physical distance



Pixel-Distance Transformation



Localisation

Locate blue and green goalposts The centre of the goal-line is the

global origin The robot orientation is the slope of

the goal-line Using the global position and

orientation of the robot, the global position of an obstacle may be obtained from its position relative to the robot



Localisation

The projection of the ball causes the red region to be returned

The blue region represents the coordinates of interest

Using a compensation function, the ball may be located with an error of less than 8cm



Intelligence System

Controls and maintains links between vision system and controller Responsible for receiving and transmitting data from the subsystems Decides robots next location and/or action Uses path planner to obtain intermediate goals Determines if intermediate goals have been reached through a combination of

vision updates and encoder odometry Updates camera at timed intervals Transmits commands to controller on demand



Decision making process

Single player state Retrieve ball Goal is set behind ball on line from

goal Shoot for goal In case of obstacles between the

ball and goal, pass towards danger zones and/or team mates



Heuristic

Possession of ball Ball in view Robot orientation Angle to goal Distance to goal Obstacles in path



Future Versions

Multiplayer state Wireless communication between

teammates More complex decisions eg

Pass/Shoot/Dribble Player modes

– Defender– Goal keeper– Attacker– Midfielder

Players controlling field zones

Game modes– Man on Man – Offensive– Defensive– Long range shots– Space seeking– Time wasting– Aggressive



Path Planning

Receives position and geometric information about every object in the global frame

This module must produce a route that:

1. Avoids all obstacles

2. Accurately and reliably finds the destination

3. Minimises the path distance

4. Is computed in minimal time



Geometric Algorithm

Uses geometry to find the optimal path using via-points The red circle is the obstacle, the blue circle is the minimum allowable

distance from the obstacle and the crosses are via-points

Start

Goal

VP 1 VP 2

o g

VP 1

VP 2

Start

Goal



Geometric Algorithm



Evaluation

Can solve complex paths Near optimal path generation Not infallible Computation Time < 150ms Does not yet account for moving

obstacles



Navigation System

Omnidirectional Two configurations Allows rotation in conjunction with translation Encoder feedback

120 degree configuration

150 degree configuration

(Weber, 2004)



Controller

Designed on the DRAGON12 Development Board

Commands received from laptop via serial port (RS-232)

Responsible for controlling the three motors to move at specified velocities through the implementation of three separate PID feedback loops

Responsible for controlling the inlet/outlet valves of the kicker and its clutch release

(http://www.evbplus.com/dragon12.html)



PWM for Motor3

PWM for Motor2

PWM for Motor1Encoder feedback for Motor2

Encoder feedback for Motor3

Controller Plant+ -

Motor Speed PID Control

Controller

Responsible for generating PWM signals and Direction bits to motor driver

Responsible for reading Motor Encoder input

Responsible for PID feedback loop using Encoder

Responsible for controlling the inlet/outlet valves of the kicker and its clutch release

Air InletAir Outlet

Clutch



Controller

Encoder Feedback:2 16-Bit Pulse Accumulators1 Rising-Edge Accumulator

ParseCommand

SCI_ISR() -Command over serial port Raise flag

Heartbeat

overflow_ISR() –Timer overflow

dir_ISR()-Counter overflow

Increment Counter

Lower flag

If flag raised

main

Kicker Control

PID Feedback

Examples

Velocity Command“V 1024 -512 0 \n”

Kicker Rod Pullback Command

“T 3\n”

Release Clutch“K \n”

Discrete Time Interval for Information Processing

Information Processing

-Calculate the period of the encoder pulses for PID feedback loop

-Kicker Control - inlet/outlet of air to muscle

-Heartbeat – if no signal been received by controller, switch off motors

Calculate period of encoders

pulses



Kicker System Designed in 2004 by George Osborne and Christian Weber Based on a combination of a tension spring and an air muscle

using a spring clutch mechanism.

(Weber, 2004)



Kicker System

The air muscle contracts when it is pressurized, pulling the tension spring back by the length of contraction of the air muscle.

Air is released from the muscle The spring clutch mechanism

stops the kicker spring from relaxing when the muscle is relaxed.

Necessary because the muscle cannot provide enough displacement to pull back the spring back in one stage.

Clutch Release

To kick the ball, the on-off clutch is operated which

releases the kicker spring

Air InletAir Outlet

Once the muscle is fully relaxed, the clutch assembly is ready for the

next air intake.Repeat until fully retracted for goal

kicking or specified position for passing

(Weber, 2004)



Summary The project aims to integrate these hardware units into a reliable and

intelligent software system capable of deriving an optimal solution to the tasks of avoiding obstacles, and of finding, collecting and kicking the ball.

Currently, the vision, kicker, and controller system have been developed in low level software.

Current goals to achieve project aims Integration of individual software components. Testing and tuning for obstacle avoidance. Testing and tuning for ball collection and kicking during navigation.



Acknowledgements

Dr. Frank Wornle Project Supervisor

Mr. Silvio De Ieso Electronics and Instrumentation

Mr. George Osborne Kicker Instrumentation



Questions?



(Weber, 2004)

Slides for questions:Kicker Shot

Documents

Mechanical Department RoboCup 19 September, 2005 The University of Adelaide Copyright © 2005Slide Number 1 David Jackson Nathan Simmonds Robert Stewart