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An Integrated, Modular Framework for Computer Vision and Cognitive Robotics Research (icVision)

Authors:
  • LYRO Robotics

Abstract and Figures

We present an easy-to-use, modular framework for performing computer vision related tasks in support of cognitive robotics research on the iCub humanoid robot. The aim of this biologically inspired, bottom-up architecture is to facilitate research towards visual perception and cognition processes, especially their influence on robotic object manipulation and environment interaction. The icVision framework described provides capabilities for detection of objects in the 2D image plane and locate those objects in 3D space to facilitate the creation of a world model.
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An Integrated, Modular Framework for
Computer Vision and Cognitive Robotics
Research (icVision)
J¨
urgen Leitner, Simon Harding, Mikhail Frank, Alexander F¨
orster and J¨
urgen
Schmidhuber
Abstract We present an easy-to-use, modular framework for performing computer
vision related tasks in support of cognitive robotics research on the iCub humanoid
robot. The aim of this biologically inspired, bottom-up architecture is to facilitate re-
search towards visual perception and cognition processes, especially their influence
on robotic object manipulation and environment interaction. The icVision frame-
work described provides capabilities for detection of objects in the 2D image plane
and locate those objects in 3D space to facilitate the creation of a world model.
1 Introduction
Vision and the visual system are the focus of much research in psychology, cogni-
tive science, neuroscience and biology. A major issue in visual perception is that
what individuals ‘see’ is not just a simple translation of input stimuli (compare op-
tical illusions). The research of Marr in the 1970s led to a theory of vision using
different levels of abstraction [11]. He described human vision as processing inputs,
stemming from a two-dimensional visual array (on the retina), to build a three-
dimensional description of the world as output. For this he defines three levels: a
2D (or primal) sketch of the scene (using feature extraction), a sketch of the scene
using textures to provide more information, and finally a 3D model.
Visual perception is of critical importance, as the sensory feedback allows to
make decisions, trigger certain behaviours, and adapt these to the current situation.
This is not just the case for humans, but also for autonomous robots. The visual
feedback enables robots to build up a cognitive mapping between sensory inputs
J¨
urgen Leitner, Mikhail Frank, Alexander F¨
orster and J¨
urgen Schmidhuber
Dalle Molle Institute for Artificial Intelligence (IDSIA), USI/SUPSI, Lugano, Switzerland
e-mail: juxi@idsia.ch
Simon Harding
Machine Intelligence, Ltd UK, e-mail: simon@machineintelligence.co.uk
1
2 Leitner et al.
and action outputs, therefore closing the sensorimotor loop. Thus being able to per-
form actions and adapt to dynamic environments. We are aiming to build a visual
perception system for robots, based on human vision, that allows to provide this
feedback leading to more autonomous and adaptive behaviours.
Our research platform is the open-system humanoid robot iCub [17] developed
within the EU funded ‘RobotCub’ project. In our setup, as shown in Figure 1 (left), it
consists of two anthropomorphic arms, a head and a torso and is roughly the size of
a human child. The iCub was designed for object manipulation research. It also is an
excellent experimental, high degree-of-freedom (DOF) platform for artificial (and
human) cognition research and embodied artificial intelligence (AI) development
[13]. To localise objects in the environment the iCub has to rely solely, similarly
to human perception, on a visual system based on stereo vision. The two cameras
are mounted in the head. Their pan and tilt can jointly be controlled, with vergence
providing a third DOF. The neck provides 3 more DOF for gazing.
We describe a framework, named icVision, supporting the learning of hand-
eye coordination and object manipulation, by solving visual perception issues in
a biologically-inspired way.
2 The icVision Framework
Research on perception has been an active component of developing artificial vision
(or computer vision) systems, in industry and robotics. Our humanoid robot should
be able, like the human mind, learn to perceive objects and develop a representation
that allows it to detect this object again. The goal is to enable adaptive, autonomous
behaviours based on visual feedback by combining robot learning approaches (AI
and machine learning (ML) techniques), with computer vision.
This framework was developed to build a biologically-inspired architecture (in-
line with the description by Marr). It processes the visual inputs received by the
cameras and builds (internal) representations of objects. It facilitates the 3D locali-
sation of the detected objects in the 2D image plane and provides this information
Fig. 1 Left: The iCub humanoid robot. Right: Architecture of the icVision framework.
The icVision Framework 3
to other systems (e.g. motion planner). Figure 1 (right) sketches the icVision ar-
chitecture. The system consists of distributed YARP modules1interacting with the
iCub hardware and each other. The specialised modules can be connected and form
pathways to perform, for example, object detection, similarly to the hierarchies in
human perception in the visual cortex (V1, V2, V3, ...) [6].
The main module, the icVision Core, handles the connection with the hard-
ware and provides housekeeping functionality (e.g., GUI, module start/stop). Im-
plemented modules include object detection (aka filters), 3D localisation and a gaze
controller interface based on the position of the object in the image plane (as pro-
vided by the filters). These are reachable via standardised interfaces allowing for
easy swapping and reuse of modules and extending functionality. For example, other
brain-inspired modules, a saliency & a disparity map, have recently been added.
2.1 Detecting Objects (icVision Filter)
The first thing done by the human visual system, and investigated by us, is the seg-
mentation (detection) in the visual space (the 2D images). There exists a vast body
of work on all aspects of image processing [3], using both classical and machine
learning approaches. The icVision filter modules, which relate to Marr’s first and
second level, provide object detection in the images. As input the filter module pro-
vides the camera image in grayscale and split into RGB and HSV channels. The
result of the filter is a binary segmentation of the camera image for a specific object.
Figure 2 shows a tea box being tracked by the iCub in real-time using a learned
filter. Also in Figure 3 the binary output can be seen.
Using machine learning, more complicated filters can be generated automatically
instead of engineered. We apply Cartesian Genetic Programming (CGP) [14, 15] to
provide automatic generation of computer programs making use of the functional-
ity integrated in the OpenCV image processing library [1], therefore incorporating
domain knowledge. It provides an effective method to learn new object detection
algorithms that are robust, if the training set is chosen correctly [4].
Fig. 2 The detection of a tea box in changing lighting condition performed by a learned filter. The
binary output of the filter is used as red overlay.
1YARP [12] is a middleware that allows easy, distributed access to the sensors and actuators of the
iCub humanoid robot, as well as, to other software modules.
4 Leitner et al.
2.2 Locating Objects (icVision 3D)
To enable the robot to interact with the environment it is important to localise the
object first. Developing an approach to perform robust localisation to be deployed
on a real humanoid robot is necessary to provide the necessary inputs for on-line
motion planning, reaching, and object manipulation.
The icVision 3D localisation module is one of the modules provided by the core
framework. It allows for conversion between camera image coordinates and 3D co-
ordinates in the robot reference frame. Using the objects location in the cameras
(provided by an icVision Filter module) and pose information from the hardware,
this module calculates where the object is in the world. This information is then
used to update the world model. Figure 3 describes the full 3D location estimation
process, starting with the camera images received from the robot and ending with
the localised object being placed in our MoBeE world model [2].
Stereo Vision describes the extraction of 3D information out of digital images
and is similar to the biological process of stereopsis in humans. Its basic principle is
the comparison of images taken of the same scene from different viewpoints. To ob-
tain a distance measure the relative displacement of a pixel between the two images
is used [5]. While these approaches, based on projective geometry, have been proven
effective under carefully controlled experimental circumstances, they are not easily
transferred to robotics applications. For the iCub platform several approaches have
previously been developed. The ‘Cartesian controller module’ [16], for example,
provides basic 3D position estimation functionality and gaze control. This module
works well on the simulated iCub, however it is not fully supported and functional
on the hardware platform, and therefore does not perform well. The most accu-
rate currently available localisation module for the iCub exists in the ‘stereoVision’
module. It provides accuracy in the range of a few centimetres.
The icVision 3D localisation module provides an easy way of swapping between
various localisation implementations, including the two mentioned. We also provide
an implementation estimating the location using machine learning [8, 10].
3 Use Cases and Current Application of the Framework
This framework has already successfully been used in our research. Here we give a
short list of use cases for the icVision framework.
The full system has been used together with a reactive controller to enable the
iCub to autonomously re-plan a motion to avoid an object it sees [2]. The object is
placed into the world model purely from vision, it is able to update the position of
the object in real-time, even while the robot is moving.
The learning of specific filters for certain objects was done using CGP (as men-
tioned above) [4, 9]. To allow for a more autonomous acquisition of object represen-
tations icVision filters are learned from objects perceived by the cameras. By using
a saliency map and standard feature detectors, we were able to provide the needed
The icVision Framework 5
Fig. 3 The 3D location estimation works
the following: At first the camera im-
ages are acquired from the hardware
via YARP. The images are converted
into grayscale, as well as, split into
RGB/HSV channels and distributed to all
active icVision filters.
Each filter then processes the images re-
ceived using OpenCV functions. (ending
with a thresholding operation). The out-
put of this is a binary image, segmenting
the object to be localised.
A blob detection algorithm is run on
these binary images to find the (centre)
location of the detected object in the im-
age frame.
The position of the object in both the
right and left camera images is sent to the
3D localisation module, where together
with the robots pose, i.e. the joint en-
coders, a 3D location estimation is gen-
erated.
As the last step the localised object is
then placed in the existing world model.
inputs to our CGP learner for building robust filters [7]. We are in the process of
learning filters for the robot’s fingers to perform research in how the humanoid can
develop sensorimotor control.
To add our 3D localisation approach to the framework, we used a Katana robotic
arm to teach the iCub how to perceive the location of the objects it sees. The Katana
positions an object within the shared workspace, and informs the iCub about the
location. The iCub then moves to observe the object from various angles and poses.
Its pose and the 2D position outputs provided by an icVision filter are used to train
artificial neural networks (ANN) to estimate the object’s Cartesian location. We
show that satisfactory results can be obtained for localisation [10]. Furthermore,
we demonstrate that this task can be accomplished safely using collision avoidance
software to prevent collisions between multiple robots in the same workspace [2].
6 Leitner et al.
4 Conclusions
We combine the current machine learning and computer vision research to build a
biologically-inspired, cognitive framework for the iCub humanoid robot. The de-
veloped icVision framework facilitates the autonomous development of new robot
controllers. Cognition and perception are seen as the foundation to developmental
mechanisms, such as as sensorimotor coordination, intrinsic motivation and hierar-
chical learning, which are investigated on the robotic platform.
The reason for the focus on vision is twofold, firstly the limited sensing capa-
bilities of the robotic platform and secondly, vision is the most important sense
for humans. As we use a humanoid robot investigating how humans do this tasks
of perception, detection and tracking of objects is of interest. These facilitate the
building of a world model, which is used for tasks like motion planning and grasp-
ing. Realtime, incremental learning is applied to further improve perception and the
model of the environment and the robot itself. Learning to grasp and basic hand-eye
coordination are the areas of research this framework is currently applied.
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