Visual Tracking on an Autonomous Self-contained Humanoid Robot Mauro Rodrigues, Filipe Silva, Vítor Santos University of Aveiro CLAWAR 2008 Eleventh International Conference on Climbing and Walking Robots and the Support Technologies for Mobile Machines 08 – 10 September 2008, Coimbra, Portugal

Outline Overview Objectives Self-Contained Platform Vision System Experimental Results Conclusions 08-10 September 2008

Overview Humanoid Platform Humanoid Robot developed at University of Aveiro Ambition is participation at Robocup Platform composed of 22 DOF’s Head on a PTU arrangement Up to 70 cm height and a mass of 6,5 kg 08-10 September 2008

Overview Distributed Control Architecture Master/Multi-Slave configuration on CAN Bus Central Processing Unit: Image processing and visual tracking External computer interaction for monitorization, debug or tele-operation Master CPU/Slaves communication interface Slaves Interface with actuators and sensors 08-10 September 2008

Objectives Central Processing Unit Integration Computational autonomy Development environment Vision System Development Visual Tracking Approach Detection and tracking of a moving target (ball) 08-10 September 2008

Self-Contained Platform CPU standard PCI-104 AMD Geode LX-800 @ 500MHz 512Mb RAM SSD 1Gb Video Signal Capture PCMCIA FireWire board Dual PCMCIA PC104 module UniBrain Fire-i @ 30fps (640x480) Camera Development Environment Linux based OpenCV 08-10 September 2008

Vision System 08-10 September 2008

Segmentation - H, S and V Components Vision System Acquisition Segmentation - H, S and V Components Object Location Pre-processing Mask 08-10 September 2008

Vision System Dynamic Region of Interest (ROI) Reduced noise impact Faster calculus No ROI With ROI 08-10 September 2008

Vision System Dynamic Region of Interest (ROI) 08-10 September 2008

Vision System Visual Tracking Approach Keep target close to image centre Image based algorithm Fixed gains proportional law, , joint increment vector , constant gain matrix , error vector defined by the ball’s offset Variable gains nonlinear law, 08-10 September 2008

Experimental Results Self-Contained Platform Acquisition libdc1394 based library Acquisition @ 320x240 with down-sampling: ~24ms Processing Without dynamic ROI: 15ms With dynamic ROI: 11ms Total = ~40ms 25Hz Times (ms)   Max. (ms) Min. (ms) Avg. (ms) St. Dev. acquisition 32,4020 11,8780 13,6820 2,0275 pyr down 25,9050 9,4730 9,8432 1,6330 segmentation 41,6030 9,3320 9,8456 2,4185 centroid location 3,2550 0,3970 1,3079 0,4478 control 0,1590 0,0140 0,0154 0,0093 actuation 37,2460 2,1670 4,4850 2,6913 total 118,6600 35,9060 39,1520 7,1468 08-10 September 2008

Experimental Results Visual Tracking Ball alignment ~1s Stationary error (~7 pixels) 08-10 September 2008

Experimental Results Visual Tracking Pan tracking with fixed gains Error increases in frontal area of the robot 08-10 September 2008

Experimental Results Visual Tracking Fixed Gains Variable Gains Pan tracking with variable gains Frontal area error reduced 08-10 September 2008

Experimental Results Visual Tracking Tilt tracking with variable gains Error similar to the pan tracking Trunk increases the error 08-10 September 2008

Experimental Results Visual Tracking 08-10 September 2008

Conclusions Implemented architecture separates the high-level vision processing from the low-level actuators control Dynamic Region of Interest guarantees a greater noise immunity and faster calculus Low error location and alignment with stationary target, fast convergence Tracking error reveals the need of a more sophisticated control Autonomous Self-Contained Humanoid Platform 25Hz average processing rate, sufficient to deal with fast-stimuli and other quick changing visual entries 08-10 September 2008

Future Work Validate ball detection through shape detection Recognition of other elements, such as the ones present at the Robocup competition Explore alternative techniques of Visual Servoing Study the influence of the robot’s movement on the visual information and on the tracking system’s performance 08-10 September 2008

Thank you for your atention 08-10 September 2008