Haptische Informationsübertragung von Drehmomentverläufen im Kontext einer Haupt- und Nebenaufgabe

The steady rise in the amount of controllable functions and control elements of technical
appliances, in particular within the automotive sector and the thereto-relating increase of
visual indications lead to an overload of the human visual perception channel as well as
a negative influence on the operating safety. Consequently, central control elements,
which combine various functions, come into action more and more frequently. The
information display is thereby separated from the information selection. The displays are
positioned in the optimum, mostly peripheral field of view of the driver, whereby, in
theory, allowing the driver to quickly avert their gaze. Nonetheless, a visual and cognitive
distraction occurs during the operation [RASSL 2004, S.65-66], [ZEILINGER 2005,
S. 7]. To remedy this problem new control system are necessary. The distraction of the
driver can be reduced by equipping already existing central control elements, usually a
rotary control element with an active haptic signal. Through a situative and contextdependent
adaption of the controlling torques certain information contents of a display
can be transmitted not only visually but also with a haptic encoding without the need for
turn of the head. It is the key objective of this dissertation to derive design proposals for
controlling torques of rotary control elements, which can be used to transmit information
haptically in the context of a primary and secondary task. Furthermore, this paper
examines how certain information content can be constituted haptically and which
haptic characteristic is preferred by users to code certain information content.
For this purpose basic concepts will be introduced initially (chapter 2), which directly
correlate with the present research topic. In addition to the human-machine interface
and the related displays and control elements, the human being and its capabilities to
perceive and process information will be observed. Therefore, the information transmission
process and the perception process, but also the system boundary of this work, will
be regarded and defined.
Chapter 3 deals with the state of the art and research. Rotary control elements with
haptic signal are introduced and the status in the automotive sector covered. When
presenting the state of research, studies are introduced, which deal with the interpretation
of controlling torques of rotary control elements. Emphasis is hereby placed on
HAMPEL [2011] since this research paper is based on his work. His design recommendations
however rest upon a pure adjusting purpose. Whether his values are also valid in the context of a primary and secondary task, or if other values need to be considered, is
part of this research paper and forms the demarcation to his work.
Chapter 4 concretizes and derives examination parameters relevant to this work. First
visual displays and their information content are analyzed and the contents gradually
selected, which are examined within this work. Subsequently haptic characteristics of a
rotary control element are derived and evaluated considering the chosen information
content and chosen for the examination.
Two test series will be conducted (chapter 5) in which 30 test subjects participated
respectively. The ratio between male and female test persons consists of 60:40 in each
test series. The test subjects mainly come from the university environment (students
and academic employees) and have an average age of 25 years. Aside from typical
data about the test persons (gender, age, occupation, etc.) their motoric capability is
measured. For this purpose a test method of the Vienna Test System is applied. A
standardized driving simulation (Lange Change Test) is used as primary task, which
was developed especially for the examination of in-vehicle human-machine interfaces in
context of primary and secondary task. The secondary task consists of linear actuation
on the torque test bench, with which the to-be examined parameters of the relating test
series can be generated and examined. Figure 1 shows the schematic experimental
setup of the two test series.
The first test series examines 16 different parameter combinations. Further parameter
combinations are derived based on the recommended parameter combination from
HAMPEL [2011] (amplitude 0,09 Nm and rotary angle 24°) and examined with regard to
objective and subjective measuring criteria. Task fulfillment, positioning time, as well as
deviation in the Lane Change Test, belong to the objective criteria. The subjective
criteria include the author’s appraisal of the test subjects regarding the task fulfillment,
the precision, as well as the applied actuating power. The results are evaluated in a
descriptive (bar- and box-plot display) and inferential statistic (primarily via the Friedman-
Test) manner as well as compared to each other. It is shown that an amplitude of
0,09 Nm and a rotary angle of 30° are to be used.
Based on these results the second test series examines how the in chapter 4 derived
information content can be transmitted haptically encoded. For this, the characteristics
of the derived haptic features (amplitude changes, rotary changes, and combinations
thereof) are interpreted first and examined subsequently. 14 different parameters are
defined in total. Under consideration of the derived information content „center mark“,
„preferred value“ and „menu change“ two options occur regarding the potential structure
of the haptic characteristics of these parameters. The haptic feature has to be symmetric
around the relating snap-in point and can only refer to one snap-in point in order to
display a „center mark“ or „preferred value“ through a rotary control element haptically
encoded. However, this type of identification of a „menu change“ is unsuitable. For this
the haptic feature has to have an asymmetrical set up. For this purpose, a duplicate
design consisting of 14 symmetrical and 14 asymmetrical parameters is used to examine
the 14 parameters. The results show that within both test series (symmetrical and
asymmetrical) parameters with a haptic characteristic in the form of an amplitude and
rotary change deliver the best results. In both cases the amplitude change shall show a
scaling factor of 1,9 while the rotary change shall show a scaling factor of 1,56 to the
respective initial value.
Lastly, research concentrates on defining which haptic features are ideally suited to
label the derived information content („center mark“, „preferred value“ and „menu
change“). It is shown that a haptic characteristic in the form of a pure amplitude change
shall be used for the labelling of a „center mark“. However, for the labelling of a „preferred
value“ a haptical characteristic, consisting of an amplitude and rotary change
shall be used. The same applies for a „menu change“ – whereby the construction shall
be asymmetrical. This study concludes with design recommendations in chapter 6.