IEEE Robotics & Automation Magazine - December 2013 - 153

A scenario net consists of a set of individual tasks that are arranged in a flowchart and
may contain loops and branches. The tasks
are arranged in a double nested loop, as
shown in Figure 4, where the outer loop
(gray arrows) relates to all tasks of manipulation of books placed on the book cart, and
the inner one (black arrows) relates the cataloging of one book. The user initializes the
task's sequence execution by giving the ini(a)
(b)
tial high-level command "new book cart";
0100 009809473
after this, the further execution of the inner
0500 Aay
loops also has to be confirmed, i.e., the end
1100 2011
1500 /1ger
user has to decide after one successful cata1700 /1XA-DE
loging whether the system should continue
2000 = 978-3-8007-3342-2
with the manipulation of the next book on
2240 GBV: 009809473
the book cart. In the case of reliable autono3000 Meyer, Sibylle
4000 Mein Freund der Roboter /
mous robot functioning, the end user does
4030 Berlin [u.a.] : VDE Verlag
not need to interfere after initializing the
(c)
(d)
execution; the end user just monitors the
autonomous execution while waiting to perFigure 5. The FRIEND's HMI: (a) scenario initialization, (b) user interaction when
form the cataloging herself.
autonomous execution fails, (c) book cataloging, user's view, and (d) cataloging
The end user can monitor the current task
data as inserted by FRIEND's end user. (The bold numbers indicate fields in
the database, and the text following the bold numbers is the bibliographic
execution either by direct visual observation
information inserted by the user.)
or, when the scene is partially hidden behind
the robot arm, by looking at the live camera
images displayed in the HMI [Figure 5(a)]. This enables the desired target position. (Here, manually is meant figuratively.
user to detect possible critical situations in which the user The user can interfere via the user interface but not with her
should interrupt the execution of the task.
hands, which are paralyzed.). After that, the end user can conThe book taken by the robot from the book cart is placed firm successful autonomous task execution (success) or can
on a special book holder in front of the user's wheelchair. abort the execution (abort) if the task cannot be completed. In
Because of the distance to book holder, the book cannot be the latter case, the execution of that task has to be started
read directly by the end user. Therefore, the hand camera of again. This concept of shared autonomy allows a successful
the robot is used to provide live images of the opened book. task completion when a fully autonomous concept fails.
After the book is placed on the book holder, the robot arm is
moved automatically in front of the opened book such that Safety of the User
the book is partly inside the field of view of the hand camera Safety has been an important consideration during the
[Figure 5(c)]. Using buttons displayed next to the live image, development of FRIEND through its different generathe end user can zoom in and out or can move the robot to tions. The safety hardware and software concept comany direction to read the whole page and to extract the infor- prises a watchdog, an electronic emergency switch,
mation necessary for the cataloging, which is the real profes- reduced power supply if the arm operates close to the
sional task of the end user supported by FRIEND. The cata- user, and a virtual safety curtain between the user and
loging data are inserted by the end user into the library robot realized in the system software. However, in the
software using speech recognition. The result of the catalog- previous generations, FRIEND was tested either by ableing is shown in Figure 5(d).
bodied persons or by disabled individuals with low levels
An autonomous execution of the sequence of tasks cannot of disability. In the presented application, the FRIEND
be guaranteed all the time. This is, for example, the case when user has quadriplegia and is paralyzed from the neck
a book cannot be detected autonomously by the vision system down. In addition, she works for several hours at a time
due to shadows or other very poor illumination conditions with FRIEND. Therefore, safety becomes even more
that cannot be avoided at the workplace. Another case arises if important than it was in previous FRIEND generations.
the trajectory for the manipulator cannot be calculated The complete safety strategy and safety system realization
because the target is out of the working space of the robot and was reconsidered. Hazard and operability analysis
therefore unreachable. In such a case, the end user is requested (HAZOP) and failure mode and effect analysis (FMEA)
to intervene. The system request is displayed in the HMI [Fig- are two commonly used methods to analyze safety critical
ure 5(b)]. This request allows the end user to control the robot situations [5], and they were used to analyze the system
manually using configuration space control to move it to the safety in an iterative systematic approach.
DECEMBER 2013

*

IEEE ROBOTICS & AUTOMATION MAGAZINE

*

153
Table of Contents for the Digital Edition of IEEE Robotics & Automation Magazine - December 2013
