Action Sloping for Manual Free Robot
Kazuki KOBAYASHI

Seiji YAMADA

Research Center for Human Media
Kwansei Gakuin University
2-1, Gakuen, Sanda Hyogo, Japan
kby@ksc.kwansei.ac.jp

National Institute of Informatics
2-1-2 Hitotsubashi, Chiyoda, Tokyo, Japanseiji@nii.ac.jp

Abstract— In this paper, we deal with the problem that willarise in the near future from robots with a lot of functions. The
problem is that the robot users will have to read thick operation
manuals. We designed an interaction that allows users to easily
notice a robot’s function without reading the manuals. We define
Function Awareness as “to notice the relationship between auser’s action and a robot’s action.” We propose a guideline fordesigning robot’s actions as, “Action Sloping,” which allows arobot to gradually express its internal state and also allows theuser to naturally notice the robot’s function by observing its
actions. We designed the concrete robot’s actions for a sweeping
robot, and the robot changes the velocity of its motion to indicate
its internal state according to the distance between the robot andits user. We develop a robot that can perform Action Sloping
using low-cost infrared sensors and simple rules for actions.
Through experiments, we investigated the users’ behavior andclarify the problems with the proposed method.

I. I NTRODUCTION
Recently, there has been an increase in research focusing onhome robots [1]. For example, an autonomous lawn mower,
Robomow1 and an autonomous sweeping robot, Roomba2 ,have been developed for practical use. It is anticipated thatsuch home robots will become increasingly sophisticated andhave multiple functions like conventional home electric appliances. However, this will cause a usability problem. A robot
with multiple functions can easily confuse its user because
they cannot comprehend all its functions. The user will also
have difficulties in reading its thick operation manuals upon
introduction to them. Such problems are typically found in thelatest mobile-phones with multiple functions.
Therefore, we propose an interaction design for complicatedrobots. It allows a user to become naturally aware of arobot’s function. We call a user’s awareness of the relationshipbetween the user’s actions and robot’s actions as, Function
Awareness. To achieve Function Awareness, we employ anapproach that helps the user become aware of a robot’s function through expression of its internal state. There has beensome research into human robot interaction; however, there
is no research into Function Awareness. Ono et al. [2] havedeveloped a technique for understanding a robot’s internal state
by improving the user’s familiarity with the robot. Komatsu [3]has reported that users can infer a machine’s internal state fromits beeps. Although these researches deal with a machine’s
1 http://www.frietndlyrobotics.com/robomow/
2 http://www.irobot.com/

internal state, they do not mention a way for a user to noticeits functions. The Theory of Mind [4] also relates to our study,
but it is difficult to apply the theory to the problem withcomplicated robots.
In this study we employ a nonverbal way for a robot to
express its internal state because it provides independency
of a specific language and low cost implementations. Some
researches have shown that nonverbal communication provides
rich information. Watanabe et al. [5] have argued on theimportance of nonverbal information in the form of head
movements, such as nodding, in communications in theirvirtual space. Matsumaru et al. [6] have shown that theirmobile robot expresses its direction of movement by a laser
pointer or an animated eye. Nonverbal information is an
essential factor for human-robot social interaction [7] andthe instruction methods in which a robot observes humanactions [8][9]. Therefore, we believe that nonverbal methods
are preferable because of their rich information, simplicity,and no need for additional equipment. In a nonverbal way wecan employ a lot of methods, such as LED flushing or beepsounds. We employ a robot’s movement because Kobayashi
et. al [10] have shown that the robot’s movement encourages
the user to perform a collaborative action in comparison with
the LED flushing and beep sounds.
The important things to consider for achieving the Function
Awareness are how a robot can make a user easily understandits internal state and the performance of a particular action
relating to its function. In this paper, we propose Action
Sloping, which is where a robot expresses its internal state
gradually according to the user’s posture. The rest of this paper
is organized as follows. In Section II we give an overview of
Action Sloping. In Section III our experiments and results arepresented. We discuss the effects of Action Sloping in Section
IV. Finally, we make a brief concluding remark and introduce
future work in Section V.
II. ACTION S LOPING
In this section, we explain a way for users to notice a robot’s
function without reading the manuals.
A. Function Awareness
When a user purchases home electric appliances or uses amachine for the first time, he/she reads the operation manuals
before use to comprehend their functions. However, searchingFig. 1.

Function Awarenessfor the desired functions and studying how to operate it arecomplicated tasks for the user. Therefore, it is better for theuser to comprehend its functions without reading the manuals.
The following three step interaction assists a user in understanding a robot’s function without reading its manuals (Fig.1).
1) Expressing the robot’s internal state:
the robot expresses its internal state and has the user
take some sort of action.
2) Taking a user’s action:
the user understands the robot’s internal state, and thentakes an appropriate action accordingly.
3) Performance of a robot’s function:
the robot performs a function corresponding to the user’s
action.
According to this interaction, the user can take notice of therelationship between his/her actions and the robot’s actions.
We define such user awareness of the relationship as, Function
Awareness.
B. Action Sloping for achieving Function AwarenessThe key technology for achieving Function Awareness is
how a robot helps a user easily understand its internal stateand perform a particular action to trigger a function. Therefore,
we propose Action Sloping, which is the way for a robot to
express its internal state according to a user’s posture. The
robot can gradually express a positive or negative internal state
by applying Action Sloping. When the user makes an action
connecting to a specific robot’s function, the robot expresses a
positive state as feedback. In contrast, when the user makes anaction connecting to none of the robot’s functions, the robot
expresses a negative state.
For example, image a housekeeping robot that performs a
specific function, such as putting something away when theuser places it at a certain distance from its sensors. In thisFig. 2.

user:
robot:
user:
robot:
user:
robot:
user:
robot:An example of Action Sloping

place an object in front of the robot
perform negative expression
place it near to the robot
perform positive expression
place it nearer to the robot
perform positive expression
place it nearer to the robot
take it and then put it away (perform function)
Fig. 3.

Typical interaction by Action Sloping

case, the robot expresses a negative state when the user places
something like a washed dish to far from a designated point,
and expresses a positive state when the user places it neara designated point (Fig.2). The robot gradually expresses its
state from negative to positive. Once the user observes thesegradual attitude changes, he/she can place the dish closer
to the robot. Such action would cause the robot to put itaway. Therefore, the user can perform an appropriate action
without reading the robot’s manual. Figure 3 shows the typicalinteraction we assume.
C. Model of Action Sloping
Figure 4 shows a model for Action Sloping. The horizontal
axis represents a user’s actions, and the vertical axis represents
a user’s awareness of a robot’s function. In the conventionalway, represented by the dotted line, a user can notice a robot’s

Fig. 5.

Fig. 4.

KheperaII

Action Sloping Model

function when he/she makes an action connected to a function(on the center of the horizontal axis), and he/she cannot notice
the function by performing another action (the horizontal partof the line) because no feedback occurs. On the other hand,the proposed way, represented by the solid line, can provide
gradual feedback according to the user’s actions. The line takes
the form of a slope and, therefore, Action Sloping allows theuser to easily notice the function.
D. Designing Robot Behavior
We have developed a design method for producing concrete
robot’s feedback motions according to Action Sloping. The
motions have a strong dependence on its hardware and tasks.
We focused on some common factors for designing a robot.
Two of them are to express comprehensible positive/negative
state and to change the motion gradually but clearly fromnegative to positive. In this paper, we employ speed of motion
for expressing its state. The fast motion represents a negative
state and a slow motion represents a negative one. The fast
motion can express failure. The user will get a negative
impression from a failure motion and a positive impression
from a normal one.
The other important design factor is how to assign a gradualmotion to the user’s action. This factor strongly depends on
the robot’s sensors. The sensor we focus on is an infrared
sensor. It can obtain the distance between a human body anda robot’s body. It is a cheap sensor and easily obtainable. The
robot we assumed performs a specific function when it senses
something at a certain distance by using infrared sensors. Its
state, expressed by fast/slow motions, is assign to the distance
between them, such as in Fig. 2.
Therefore, we can design a robot to express its internal
state by changing its motion speed according to the distance
between the user and the robot. This method encourages theuser to perform an action that triggers a robot’s function.
III. E XPERIMENTS
We performed exploratory experiments to evaluate the effectof Action Sloping. First, we applied Action Sloping to a small

Fig. 6.

Experimental environment

mobile robot on a sweeping task. Next, we investigated users’
reactions to the sweeping robot.
A. Robot and Environment
We used a small mobile robot, KheperaII (Fig.5). The robot
has eight infrared proximity and ambient light sensors withup to a 100 mm range, a Motorola 68331 (25MHz) processor,
512 Kbytes of RAM, 512 Kbytes of flash ROM, and two DC
brushed servo motors with incremental encoders. Its program,
written in C-language, runs on the RAM. We rearranged an
infrared sensor and added an infrared sensor with up to an 800
mm range (SHARP GP2D12) for sensing its overhead.
Figure 6 shows the experimental environment, which had aflat surface (400 mm × 300 mm), a wall surrounding it, andan obstacle. It simulated an ordinary human work space likea desktop. The obstacle corresponded to a pen-holder, remotecontrol, etc., and could easily be moved by a participant. It
had an electric light bulb so that the robot could distinguishit from the wall.
B. Behavior of robot
The robot autonomously swept the floor in the environment.
It performed random turns in front of the wall. It was unable
to clean the floor because it was difficult to implement air
aspiration equipment on the small robot. It moved along theside of the obstacle to encourage the user to move it. When theuser moved the obstacle, the robot stopped and expressed its
internal state by using Action Sloping. It expressed its internal
state by spinning itself. Figure 7 shows a robot’s expression
by a change in its spinning speed according to the distanceLayer 1: Obstacle Avoidance- Stop if something is sensed
in front of the robot and it is going forward.
- Stop if something is sensed
behind the robot and it is backing up.
Layer 2: Random Sweeping and Wall Following- Move forward if the robot senses nothing in front of it.
- Follow the lit object clockwise
if it senses the object on its left.
- Follow the lit object counterclockwise
if it senses the object on its right.
- Turn clockwise in a range from 90◦ to 180◦
if something is sensed on its right.
- Turn counterclockwise in a range from 90◦ to 180◦
if something is sensed on its left.

Fig. 7.

State expression by using Action Sloping

Layer 3: Interaction- Expressing a state if a lit object
is moved and the robot is moving along the side of it.
- Go straight if something is sensed
above the robot’s top and it is expressing a state.
- Go back and turn clockwise in a range from 90◦ to 180◦
if something above the robot’s top is removed.
- Go straight if something is placed close to the robot’s top.

Fig. 9.

Fig. 8.

Cooperative Sweeping

between the obstacle and the sensor on its top. When it sensed
an object close to its top, it spun slowly. When it sensed theobject far from its top, it spun fast. The spinning expression
was performed when the object was placed within a distanceof 20 to 800 mm.
The robot had a specific function. We called it Cooperative
Sweeping [11]. Cooperative Sweeping was performed when
the user placed the obstacle near its top with a range from
5 to 20 mm. This function enabled the robot to sweep thefloor under the obstacle by priority taking while the user held
it. Figure 8 shows this Cooperative Sweeping. It repeatedspinning and going straight under it, and finished Cooperative
Sweeping when the user put the obstacle closer to its top witha range from 0 to 5 mm and then went elsewhere.
C. Implementation of robot’s behavior
We employed subsumption architecture [12] for the
behavior-based approach. Figure 9 shows the three-layered
architecture used for the robot. Each layer asynchronously
checks the applicability of behavior and executes it. The
higher layers suppress the lower layer’s, and the lower layers
have more reactive behavior. The behavior of each layer
consisted of multiple actions. When the system simultaneously
obtained multiple outputs, it generally selected the highest
layer’s action. Each layer had a frequency for action output tosmoothly control the robot. We set 5 msec intervals for the 1st
layer, 10 msec for the 2nd layer, and 5 msec for the 3rd layer.
Obstacle avoidance and interaction occurred most frequently.

Subsumption architecture of robot

The 3rd layer included the state expression by using Action
Sloping and Cooperative Sweeping.
Figure 10 shows snapshots of actual robot’s behavior. Whenthe obstacle was placed at more than 220 mm from the topof the robot (4th), it performed the fastest turn (about a 360◦
roll per second). When the obstacle was placed the nearest (20mm from its top) (6th), it performed the slowest turn (abouta 360◦ roll per 5 seconds).
D. Method
The purpose of the experiment was to investigate participants’ reactions to the sweeping robot and to evaluate theeffect of Action Sloping. We explained to the participants thatthe machine was a sweeping robot, it repeated spinning infront of a wall, and imagined its path was cleaned, because it
could not perform dust collection. In addition, we asked themto help it if necessary.
At the beginning of the experiment, the robot started autonomous sweeping and then followed the object. The robot
begun to express its internal state when the participant moved
the object. If the participants did something for it, it changed
the spin speed or performed the Cooperative Sweeping.
We prepared two robot’s state expressions and three additional explanations. Figure 11 shows the details of theexpressions and the explanations.
E. Results
Four females and three males in their 20’s to 30’s were
the participants for these experiments. Table I shows theexperimental results. In the figure, “No.” is the participants’ID, and “State” and “Explanation” are the ways for the robot’s
state expression and the additional explanation, respectively,

State expressions:
S1: A negative expression is represented by a fast spin;a positive expression is a slow spin.
S2: A negative expression is represented by a stop anda slow spin; the positive expression is a fast spin.
Explanations:
E1: Do not move the robot.
E2: The robot does not easily get broken.
E3: The robot can sense over its head.
Fig. 11.

Fig. 10.

Snapshots of robot’s behavior

outlined in Fig. 11. It shows whether a participant moved the
obstacle (MoveObj), placed it on the robot’s top (TopObj), andnoticed the robot’s function, Cooperative Sweeping (Aware).
Figure 12 shows participant’s behavior.
According to Table I, there was no participant who noticed
the function. However, all participants moved the object and a
few participants placed it on the robot’s top when we explained
to them that it could sense something over it. The actions
performed by the participants will provide helpful information
for the development of Action Sloping.
We did not conduct officially Kansei evaluations in theexperiments. However, we obtained several comments fromthe participants. Some participants felt the robot getting broken
when it performed the fast spin. Others felt it careful cleaning.
IV. D ISCUSSION
A. Participants’ reaction
In the experiments, there was no participant who noticed
the Cooperative Sweeping function. We have taken into consideration that this result would be caused by the timing of
the robot’s state expression. Users often use machines with

Details of state expressions and explanations

Fig. 12.

Snapshots of participant’s behavior

a clear purpose; however, the participants seemed to have noconsciousness of their purpose of action. They just reacted to
the robot without thinking of how efficient it was. We thentook into consideration that the timing is important for users
to perform something associated with their working efficiency.
In the experiments we explained to most of them thatthe robot did not break down easily (E2). We added this
explanation because one participant thought the robot break
down and she fled the room when we explained E1. However,explanation E2 is not preferable for a manual free machine.
An interaction design using a failure expression may have thedisadvantage of making a user nervous.
In the case of explaining to them that the robot could sense
objects above it (E3), two out of three participants placed theobject above the robot. This explanation is also not preferable.
We can deal with this problem by visualizing a sensor on
it. For example, attaching an eye-like picture near a sensor
or having the robot behave autonomously according to the
output of the sensor on its top. The participants without E3
explanation moved the object to the robot’s sides. We took
into consideration that their actions were a result of observing

TABLE I
E XPERIMENTAL R ESULTS

No.
1
2
3
4
5
6
7

State
S1
S1
S1
S1
S1
S2
S2

Explanation
E1
E1,E2
E1,E2
E1,E2,E3
E1,E2,E3
E1,E2,E3

MoveObj
Yes
Yes
Yes
Yes
Yes
Yes
Yes

TopObj
No
No
No
No
Yes
No
Yes

Aware
No
No
No
No
No
No
No

its autonomous behavior, spinning in front of obstacles. If
we make the robot behave autonomously according to the
output of the sensor on its top, users will notice the sensor
without explanation. The most important problem throughout
the experiments was that the participants were unable tonotice the Cooperative Sweeping function. The function would
originally be difficult to notice. It would also be difficult
for them to conceive of holding the object above the robot.
We observed that most of the participants moved the object
horizontally, but they did not move it vertically. Therefore,
better results could be achieved with robot design that gives ademonstration of a vertical movement according to the outputof the top sensor.
In the exploratory experiments we made the robot express
both positive and negative states to encourage its user to dosomething. This was just an illustrative case. We are now
planning different experiments with a different robot and adifferent method of expression. We will compare the efficiencyof the robot with the Actions Sloping and without it byobserving the users’ behavior.
B. Limitation of Action Sloping
In the experiments the robot had only one function, Cooperative Sweeping. The manual free machine solves the problem
in a situation where a user cannot naturally and intuitively
use a robot due to the multitude of functions it has. We arealso planning an experiment with a robot that has multiple
functions. The implementation is heavily dependent on its
hardware. Therefore, we will employ an AIBO instead ofa KheperaII, because an AIBO has a lot of actuators for
performing functions and expressing its state, and many typesof sensors for collecting the user’s actions. In our experiments
we employed distance as a cue to control the robot; however, auser’s touch and voice will be available for the Action Slopingin the next experiment.
In the present state of action sloping, we assume that a
robot has a single function. Thus we can carefully design asingle action sloping to the robot’s function. However, if arobot has several functions, it will be quite difficult to design
action sloping for each function because action sloping may
interfere together.
V. C ONCLUSION
We dealt with the problem that will arise in the near futurefrom robots with a lot of functions. The problem will be that auser will have to read their thick operation manuals. Then, we
designed an interaction where users can easily notice a robot’s
function without reading the manuals. We propose “Function
Awareness”, which is defined as, “to notice the relationshipbetween a user’s action and a robot’s action.” We also proposeda guideline for designing the robot’s actions called “Action
Sloping,” which has a robot gradually express its internal stateand encourages a user to naturally notice a robot’s function
by observing its actions. We designed concrete robot actions
for a sweeping robot, and the robot changed the velocity
of its motion to indicate its internal state according to the
distance between the robot and its user. We developed a robot
performing Action Sloping that used low-cost infrared sensors
and simple rules for actions. In experiments, we investigated
the users’ reactions for the robot and clarified some problems.
We are now planning different experiments with a different
robot and a different method of expression to confirm theeffectiveness of Action Sloping.
R EFERENCES[1] United Nations Economic Commission for Europe and International
Federation of Robotics, World Robotics 2004 – Statistics, Market
Analysis, Forecasts, Case Studies and Profitability of Robot Investment.
Palais des Nations, 2004.
[2] T. Ono, M. Imai, and R. Nakatsu, “Reading a robot’s mind: A modelof utterance understanding based on the theory of mind mechanism,”International Journal of Advanced Robotics, vol. 14, no. 4, pp. 311–
326, 2000.
[3] T. Komatsu, “Can we assign attitudes to a computer based on its beepsounds?” in Proceedings of the Affective Interactions: The computerin the affective loop Workshop at Intelligent User Interface, 2005, pp.
35–37.
[4] S. Baron-Cohen, Mindblindness: An Essay on Autism and Theory of
Mind. MIT Press, 1995.
[5] T. Watanabe, M. Okubo, and M. Inadome, “Virtual communication
system for human interaction analysis,” in Proc. of the 7th IEEE
International Workshop on Robot and Human Communication, 1998,
pp. 21–26.
[6] T. Matsumaru, K. Iwase, K. Akiyama, T. Kusada1, and T. Ito, “Mobile
robot with eyeball expression as the preliminary-announcement anddisplay of the robotrsquos following motion,” Autonomous Robots,vol. 18, no. 2, pp. 231–246, 2005.
[7] T. W. Fong, I. Nourbakhsh, and K. Dautenhahn, “A survey of sociallyinteractive robots,” Robotics and Autonomous Systems, vol. 42, no. 3–4,
pp. 143–166, 2003.
[8] Y. Kuniyoshi, M. Inaba, and H. Inoue, “Learning by watching: extracting reusable task knowledge from visual observation of humanperformance,” IEEE Transactions on Robotics and Automation, vol. 10,
no. 6, pp. 799–822, 1994.
[9] M. Nicolescu and M. Mataric, “Learning and interacting in human-robot
domains,” IEEE Transactions on Systems, Man and Cybernetics, Part A,
vol. 31, no. 5, pp. 419–430, 2001.
[10] K. Kobayashi and S. Yamada, “Informing a user of robot’s mind by actions,” in Proc. of the third International Conference on Computational
Intelligence, Robotics and Autonomous Systems, 2005.
[11] ——, “Human-robot cooperative sweeping by extending commands
embedded in actions,” in Proc. of IEEE/RSJ International Conferenceon Intelligent Robots and Systems, 2005, pp. 1827–1832.
[12] R. A. Brooks, “A robust layered control system for a mobile robot,”IEEE Journal of Robotics and Automation, vol. 2, no. 1, pp. 14–23,
1986.