"A New Approach for Canceling Turning Motion in the Locomotion Interface, ATLAS",
Proc of ASME-DSC-Vol.67, pp.405-406,1999

A New Approach for Canceling Turning Motion in the Locomotion Interface, ATLAS
Haruo Noma
Tsutomu Miyasato
ATR Media Integration and Communications Research Laboratories
Hikaridai, Seika-cho, Kyoto, 619-0288, Japan
E-mail: noma@mic.atr.co.jp

Introduction
We are concerned with communication media, especially media fordaily communication. Let’s consider the case when people want to chat.
For example, when we travel alone in a foreign country or when we see
an impressive painting alone, we may want to enjoy the feeling with ourfamily. We have introduced “Tel-E-Merge” as new communication
system for “I wish you were here” [1]. We coined the term Tel-E-Merge
to have a double meaning, Tele-Merge and Tel-Emerge, which will makeit possible to merge a remotely located person, the tele-visitor, into atele-inviter’s space through VR systems.
In this research, I intend to shape Tel-E-Merge into a media thatallows conversation between remotely separated persons while they walk.
It consists of the locomotion interface ATLAS (ATR Locomotion
Interface for Active Self Motion, Fig. 1) [2] and the mobile TV-phonerobot AIR (ATR Imaging Robot, Fig. 2).
We employ a treadmill and turntable approach to allow ATLAS tocancel walking motion in any direction. The visual sensor on ATLAS
estimates the user’s walking speed and turning motion from the feetmotion, and controls the belt speed and posture of the treadmill to keep
the walker on the belt. AIR is a radio controlled wheeled robot with a TV
phone. The result of the walking motion detection system in ATLAS istransmitted to AIR in a remote real space, and AIR is driven accordingly.
Simultaneously, the TV phone system on AIR feeds back the visual andaudio information of the remote space. Therefore, the users can get the
feeling of actual walking together in the remote large space.
In later sections, we present the details of the locomotion interface
ATLAS, especially how ATLAS is able to cancel turning motions.

Locomotion Interface ATLAS
I define a locomotion interface as one that can measure and cancel
the user’s walking motion: walking forward and turning in any direction.
We employed a treadmill approach to ATLAS. The main advantage of

Fig.1 Locomotion Interface - ATLAS

Fig. 2 Imaging Robot - AIR

the treadmill approach is that it gives the user a very natural feeling ofwalking without any bothersome equipment. However, when using thetreadmill, we are confronted by two difficulties: how to keep the walker
from falling off, and how to allow the walker to change direction.
As a solution for the first point, we have reported an effective methodthat integrates a motor-powered active treadmill with a visual motion
detecting method [2]. The motion detecting method estimates the walking
speed on the belt, and the system controls the belt speed as a result.
Applying the method to ATLAS, the user can walk and stop at any speed
as s/he likes on the belt.
In this paper, we discussed the second point of allowing a user toturn to any direction while walking. If the walker makes turn on an
ordinary treadmill, s/he will lose his/her footing and fall off of the belt.
To keep the user's foot on the belt at that time, we considered a methodthat would cancel the turning motion by rotating the treadmill.
We, first, made observations of ordinary turning motions. The mostimportant advantage of ATLAS is that the user needs to put only two
passive IR-reflecting markers onto the feet (Fig. 1), and they don't disturb
the walking motion. Maintaining this advantage, we tried to use makers
to detect turning motions in the same way as estimating the walking
speed. Then, we will describe implementation of our motion cancelingmethod on ATLAS.

Detection of Turning Motion with Visual Sensor
When we walk straight, we usually put one foot down in front of
the position where the foot took off at the previous step, and its track
makes a slight curve to the outside. On the other hand, when we turn acorner, one foot steps forward obliquely into the turning direction. We
aimed to employ the curved foot tracks for turning motion detection.
We observed the turning motion on a flat floor. Three males wereasked to walk three ways: straight and turning 45° and 90° to the left.
Three magnetic position sensors were put onto the both feet and the waist,

Fig. 3 Length of the step in the lateral direction of
normal walking on a flat floor.

to record these positions at 90 Hz. The subjects were asked to makeeight trials on each path.
We manually worked out the shifted length X of each trial. In thecase of “walking straight,” the shifted length means how much does it
curve compared with the ideal shortest track while walking straight asshown in figure 3. In the case of “turning 45° and 90° to the left,” theshifted length means how long does the subject step forward along alateral axis of the walking direction. This is measured beginning withthe step when the subjects started the turning motion. Since the first stepat each trial controlled whether the right or left foot was used turning, we
obtained four trials for each foot as a result.
The box graph, figure 3, shows that the shifted length was within 8
cm while walking straight, however, it reached about 50 cm when subjects
turned to the left. In the case of “turning 45° and 90° to the felt,” analysisof the variance showed that the conditions of the turning angle and whether
the left or right foot were not significant factors in the shifted length.
Therefore, it follows from what has been shown that the shifted
length of the step can be used to distinguish whether a user is walking
straight or turning into any direction.

Cancellation of Turning Motion
Keeping the user’s feet on the belt while turning, we proposed amethod that cancels the turning motion by using a turntable. In otherwords, we regard the foot in its swinging phase as a swinging pendulum,
and applied Corioli’s force to move the obliquely stepped foot back.
Let us consider the turning motion on the belt. Figure 4 shows a top
4view
Cancelingmethod when
for turning
motionof the treadmill
a walker
starts to turn to the right. The next
step is supposed to be taken with right foot, and the foot will be placed
down at Pr as previously observed. At that time, if the belt is rotated θj1 in
the clockwise direction by the turntable, synchronizing with the footmotion as shown by the dotted line, Pr looks to move only forward in thecoordinate B fixed on the treadmill.
We implemented this method on ATLAS. The visual motion
detecting system on ATLAS can measure the feet's motion in real time.
When a swinging foot moves in a lateral direction more than the a certain
threshold, it detects a turning motion. Simultaneously, the turntable rotates
the treadmill according to the following equation.
ω = α • X1
(1)
Here, we defined X 1 as lateral shift of the oblique step following

the previous step, Pr0, and ω as rotational speed. ‘α’ is the feedback gain
parameter. In this configuration, Corioli’s force and centrifugal force
are applied to the feet. The former force is proportional to the foot speed
and the latter force is proportional to the distance from the center ofturntable B. Since the walker’s position on the belt is controlled to benear B always [2] , we estimated that the centrifugal force is about one
fifth of the Corioli’s force while walking on ATLAS.
Figure 5 shows a typical time series graph of the results. The upper
two lines show the feet’ position along the X-axis in the coordinate B,
and the circled numbers indicate the order of the steps. The subject walked
straight in the first 7 steps during phase (A), then turned into right whilephase (B). He walked straight in phase (C) again and stopped at phase(D). The third line, the rotational angle of the turntable, shows that thetreadmill was rotating according to the turning motion in phase “B”. At
that time, a part of the shifted step was canceled as shown in the 8th 11th steps. One reason why it could not cancel during the motion was
due to the mechanical and the feedback delay of rotation. Revising thedelay, we expect to be able to predict turning motions from the motionof other parts of the body, such as hands, a waist and so on.
Another problem is that our method needs to rotate as the user turns
a corner. If s/he keeps turning right many times, the treadmill has torotate in the same angle also. Mechanical problems, however, limit the
maximum angle. Therefore, the system returns the treadmill to the neutral
angle while the user walks straight as shown in phases “C” and “D”. The
returning speed is slow enough not to affect the walking.

Conclusion
Using a treadmill and a turntable, we proposed a new method thatallows a user to walk in any direction as s/he likes. The trial
implementation could not cancel the entire turning motion because of asystem delay. We must revise the implementation and build into the TelE-merge system.

References[1] Miyasato, Nakatsu, “User Interface Technologies for a Virtual
Communication Space”, IEEE Computer Vision for Virtual Reality Based
Human Communications, pp105-110, 1998
[2] Noma, Miyasato, “Design for Locomotion Interface in a Large
Scale Virtual Environment, ATLAS: ATR Locomotion Interface for
Active Self Motion”, ASME-DSC-Vol.64, pp.111-118, 1998

Pl0,Pr0: Left and right foot positionat the end of n-th step
Pl,Pr: Left and right foot positionat the end of n+1-th stepwith turning motion.
θj1,ω : R o t a t i o n a l a n g l e a n d
speed of the treadmill.
B:
Fixed axis of coordinate on
the treadmill, and thecenter of rotation of thetreadmillFig. 4 Canceling turning motion on the treadmill when auser started turning in the right.

Fig. 5 Typical results on the trial ATLAS

"A New Approach for Canceling Turning Motion in the Locomotion Interface, ATLAS",
Proc of ASME-DSC-Vol.67, pp.405-406,1999

A New Approach for Canceling Turning Motion in the Locomotion Interface, ATLAS
Haruo Noma
Tsutomu Miyasato
ATR Media Integration and Communications Research Laboratories
Hikaridai, Seika-cho, Kyoto, 619-0288, Japan
E-mail: noma@mic.atr.co.jp

Introduction
We are concerned with communication media, especially media fordaily communication. Let’s consider the case when people want to chat.
For example, when we travel alone in a foreign country or when we see
an impressive painting alone, we may want to enjoy the feeling with ourfamily. We have introduced “Tel-E-Merge” as new communication
system for “I wish you were here” [1]. We coined the term Tel-E-Merge
to have a double meaning, Tele-Merge and Tel-Emerge, which will makeit possible to merge a remotely located person, the tele-visitor, into atele-inviter’s space through VR systems.
In this research, I intend to shape Tel-E-Merge into a media thatallows conversation between remotely separated persons while they walk.
It consists of the locomotion interface ATLAS (ATR Locomotion
Interface for Active Self Motion, Fig. 1) [2] and the mobile TV-phonerobot AIR (ATR Imaging Robot, Fig. 2).
We employ a treadmill and turntable approach to allow ATLAS tocancel walking motion in any direction. The visual sensor on ATLAS
estimates the user’s walking speed and turning motion from the feetmotion, and controls the belt speed and posture of the treadmill to keep
the walker on the belt. AIR is a radio controlled wheeled robot with a TV
phone. The result of the walking motion detection system in ATLAS istransmitted to AIR in a remote real space, and AIR is driven accordingly.
Simultaneously, the TV phone system on AIR feeds back the visual andaudio information of the remote space. Therefore, the users can get the
feeling of actual walking together in the remote large space.
In later sections, we present the details of the locomotion interface
ATLAS, especially how ATLAS is able to cancel turning motions.

Locomotion Interface ATLAS
I define a locomotion interface as one that can measure and cancel
the user’s walking motion: walking forward and turning in any direction.
We employed a treadmill approach to ATLAS. The main advantage of

Fig.1 Locomotion Interface - ATLAS

Fig. 2 Imaging Robot - AIR

the treadmill approach is that it gives the user a very natural feeling ofwalking without any bothersome equipment. However, when using thetreadmill, we are confronted by two difficulties: how to keep the walker
from falling off, and how to allow the walker to change direction.
As a solution for the first point, we have reported an effective methodthat integrates a motor-powered active treadmill with a visual motion
detecting method [2]. The motion detecting method estimates the walking
speed on the belt, and the system controls the belt speed as a result.
Applying the method to ATLAS, the user can walk and stop at any speed
as s/he likes on the belt.
In this paper, we discussed the second point of allowing a user toturn to any direction while walking. If the walker makes turn on an
ordinary treadmill, s/he will lose his/her footing and fall off of the belt.
To keep the user's foot on the belt at that time, we considered a methodthat would cancel the turning motion by rotating the treadmill.
We, first, made observations of ordinary turning motions. The mostimportant advantage of ATLAS is that the user needs to put only two
passive IR-reflecting markers onto the feet (Fig. 1), and they don't disturb
the walking motion. Maintaining this advantage, we tried to use makers
to detect turning motions in the same way as estimating the walking
speed. Then, we will describe implementation of our motion cancelingmethod on ATLAS.

Detection of Turning Motion with Visual Sensor
When we walk straight, we usually put one foot down in front of
the position where the foot took off at the previous step, and its track
makes a slight curve to the outside. On the other hand, when we turn acorner, one foot steps forward obliquely into the turning direction. We
aimed to employ the curved foot tracks for turning motion detection.
We observed the turning motion on a flat floor. Three males wereasked to walk three ways: straight and turning 45° and 90° to the left.
Three magnetic position sensors were put onto the both feet and the waist,

Fig. 3 Length of the step in the lateral direction of
normal walking on a flat floor.

to record these positions at 90 Hz. The subjects were asked to makeeight trials on each path.
We manually worked out the shifted length X of each trial. In thecase of “walking straight,” the shifted length means how much does it
curve compared with the ideal shortest track while walking straight asshown in figure 3. In the case of “turning 45° and 90° to the left,” theshifted length means how long does the subject step forward along alateral axis of the walking direction. This is measured beginning withthe step when the subjects started the turning motion. Since the first stepat each trial controlled whether the right or left foot was used turning, we
obtained four trials for each foot as a result.
The box graph, figure 3, shows that the shifted length was within 8
cm while walking straight, however, it reached about 50 cm when subjects
turned to the left. In the case of “turning 45° and 90° to the felt,” analysisof the variance showed that the conditions of the turning angle and whether
the left or right foot were not significant factors in the shifted length.
Therefore, it follows from what has been shown that the shifted
length of the step can be used to distinguish whether a user is walking
straight or turning into any direction.

Cancellation of Turning Motion
Keeping the user’s feet on the belt while turning, we proposed amethod that cancels the turning motion by using a turntable. In otherwords, we regard the foot in its swinging phase as a swinging pendulum,
and applied Corioli’s force to move the obliquely stepped foot back.
Let us consider the turning motion on the belt. Figure 4 shows a top
4view
Cancelingmethod when
for turning
motionof the treadmill
a walker
starts to turn to the right. The next
step is supposed to be taken with right foot, and the foot will be placed
down at Pr as previously observed. At that time, if the belt is rotated θj1 in
the clockwise direction by the turntable, synchronizing with the footmotion as shown by the dotted line, Pr looks to move only forward in thecoordinate B fixed on the treadmill.
We implemented this method on ATLAS. The visual motion
detecting system on ATLAS can measure the feet's motion in real time.
When a swinging foot moves in a lateral direction more than the a certain
threshold, it detects a turning motion. Simultaneously, the turntable rotates
the treadmill according to the following equation.
ω = α • X1
(1)
Here, we defined X 1 as lateral shift of the oblique step following

the previous step, Pr0, and ω as rotational speed. ‘α’ is the feedback gain
parameter. In this configuration, Corioli’s force and centrifugal force
are applied to the feet. The former force is proportional to the foot speed
and the latter force is proportional to the distance from the center ofturntable B. Since the walker’s position on the belt is controlled to benear B always [2] , we estimated that the centrifugal force is about one
fifth of the Corioli’s force while walking on ATLAS.
Figure 5 shows a typical time series graph of the results. The upper
two lines show the feet’ position along the X-axis in the coordinate B,
and the circled numbers indicate the order of the steps. The subject walked
straight in the first 7 steps during phase (A), then turned into right whilephase (B). He walked straight in phase (C) again and stopped at phase(D). The third line, the rotational angle of the turntable, shows that thetreadmill was rotating according to the turning motion in phase “B”. At
that time, a part of the shifted step was canceled as shown in the 8th 11th steps. One reason why it could not cancel during the motion was
due to the mechanical and the feedback delay of rotation. Revising thedelay, we expect to be able to predict turning motions from the motionof other parts of the body, such as hands, a waist and so on.
Another problem is that our method needs to rotate as the user turns
a corner. If s/he keeps turning right many times, the treadmill has torotate in the same angle also. Mechanical problems, however, limit the
maximum angle. Therefore, the system returns the treadmill to the neutral
angle while the user walks straight as shown in phases “C” and “D”. The
returning speed is slow enough not to affect the walking.

Conclusion
Using a treadmill and a turntable, we proposed a new method thatallows a user to walk in any direction as s/he likes. The trial
implementation could not cancel the entire turning motion because of asystem delay. We must revise the implementation and build into the TelE-merge system.

References[1] Miyasato, Nakatsu, “User Interface Technologies for a Virtual
Communication Space”, IEEE Computer Vision for Virtual Reality Based
Human Communications, pp105-110, 1998
[2] Noma, Miyasato, “Design for Locomotion Interface in a Large
Scale Virtual Environment, ATLAS: ATR Locomotion Interface for
Active Self Motion”, ASME-DSC-Vol.64, pp.111-118, 1998

Pl0,Pr0: Left and right foot positionat the end of n-th step
Pl,Pr: Left and right foot positionat the end of n+1-th stepwith turning motion.
θj1,ω : R o t a t i o n a l a n g l e a n d
speed of the treadmill.
B:
Fixed axis of coordinate on
the treadmill, and thecenter of rotation of thetreadmillFig. 4 Canceling turning motion on the treadmill when auser started turning in the right.

Fig. 5 Typical results on the trial ATLAS

"A New Approach for Canceling Turning Motion in the Locomotion Interface, ATLAS",
Proc of ASME-DSC-Vol.67, pp.405-406,1999

A New Approach for Canceling Turning Motion in the Locomotion Interface, ATLAS
Haruo Noma
Tsutomu Miyasato
ATR Media Integration and Communications Research Laboratories
Hikaridai, Seika-cho, Kyoto, 619-0288, Japan
E-mail: noma@mic.atr.co.jp

Introduction
We are concerned with communication media, especially media fordaily communication. Let’s consider the case when people want to chat.
For example, when we travel alone in a foreign country or when we see
an impressive painting alone, we may want to enjoy the feeling with ourfamily. We have introduced “Tel-E-Merge” as new communication
system for “I wish you were here” [1]. We coined the term Tel-E-Merge
to have a double meaning, Tele-Merge and Tel-Emerge, which will makeit possible to merge a remotely located person, the tele-visitor, into atele-inviter’s space through VR systems.
In this research, I intend to shape Tel-E-Merge into a media thatallows conversation between remotely separated persons while they walk.
It consists of the locomotion interface ATLAS (ATR Locomotion
Interface for Active Self Motion, Fig. 1) [2] and the mobile TV-phonerobot AIR (ATR Imaging Robot, Fig. 2).
We employ a treadmill and turntable approach to allow ATLAS tocancel walking motion in any direction. The visual sensor on ATLAS
estimates the user’s walking speed and turning motion from the feetmotion, and controls the belt speed and posture of the treadmill to keep
the walker on the belt. AIR is a radio controlled wheeled robot with a TV
phone. The result of the walking motion detection system in ATLAS istransmitted to AIR in a remote real space, and AIR is driven accordingly.
Simultaneously, the TV phone system on AIR feeds back the visual andaudio information of the remote space. Therefore, the users can get the
feeling of actual walking together in the remote large space.
In later sections, we present the details of the locomotion interface
ATLAS, especially how ATLAS is able to cancel turning motions.

Locomotion Interface ATLAS
I define a locomotion interface as one that can measure and cancel
the user’s walking motion: walking forward and turning in any direction.
We employed a treadmill approach to ATLAS. The main advantage of

Fig.1 Locomotion Interface - ATLAS

Fig. 2 Imaging Robot - AIR

the treadmill approach is that it gives the user a very natural feeling ofwalking without any bothersome equipment. However, when using thetreadmill, we are confronted by two difficulties: how to keep the walker
from falling off, and how to allow the walker to change direction.
As a solution for the first point, we have reported an effective methodthat integrates a motor-powered active treadmill with a visual motion
detecting method [2]. The motion detecting method estimates the walking
speed on the belt, and the system controls the belt speed as a result.
Applying the method to ATLAS, the user can walk and stop at any speed
as s/he likes on the belt.
In this paper, we discussed the second point of allowing a user toturn to any direction while walking. If the walker makes turn on an
ordinary treadmill, s/he will lose his/her footing and fall off of the belt.
To keep the user's foot on the belt at that time, we considered a methodthat would cancel the turning motion by rotating the treadmill.
We, first, made observations of ordinary turning motions. The mostimportant advantage of ATLAS is that the user needs to put only two
passive IR-reflecting markers onto the feet (Fig. 1), and they don't disturb
the walking motion. Maintaining this advantage, we tried to use makers
to detect turning motions in the same way as estimating the walking
speed. Then, we will describe implementation of our motion cancelingmethod on ATLAS.

Detection of Turning Motion with Visual Sensor
When we walk straight, we usually put one foot down in front of
the position where the foot took off at the previous step, and its track
makes a slight curve to the outside. On the other hand, when we turn acorner, one foot steps forward obliquely into the turning direction. We
aimed to employ the curved foot tracks for turning motion detection.
We observed the turning motion on a flat floor. Three males wereasked to walk three ways: straight and turning 45° and 90° to the left.
Three magnetic position sensors were put onto the both feet and the waist,

Fig. 3 Length of the step in the lateral direction of
normal walking on a flat floor.

to record these positions at 90 Hz. The subjects were asked to makeeight trials on each path.
We manually worked out the shifted length X of each trial. In thecase of “walking straight,” the shifted length means how much does it
curve compared with the ideal shortest track while walking straight asshown in figure 3. In the case of “turning 45° and 90° to the left,” theshifted length means how long does the subject step forward along alateral axis of the walking direction. This is measured beginning withthe step when the subjects started the turning motion. Since the first stepat each trial controlled whether the right or left foot was used turning, we
obtained four trials for each foot as a result.
The box graph, figure 3, shows that the shifted length was within 8
cm while walking straight, however, it reached about 50 cm when subjects
turned to the left. In the case of “turning 45° and 90° to the felt,” analysisof the variance showed that the conditions of the turning angle and whether
the left or right foot were not significant factors in the shifted length.
Therefore, it follows from what has been shown that the shifted
length of the step can be used to distinguish whether a user is walking
straight or turning into any direction.

Cancellation of Turning Motion
Keeping the user’s feet on the belt while turning, we proposed amethod that cancels the turning motion by using a turntable. In otherwords, we regard the foot in its swinging phase as a swinging pendulum,
and applied Corioli’s force to move the obliquely stepped foot back.
Let us consider the turning motion on the belt. Figure 4 shows a top
4view
Cancelingmethod when
for turning
motionof the treadmill
a walker
starts to turn to the right. The next
step is supposed to be taken with right foot, and the foot will be placed
down at Pr as previously observed. At that time, if the belt is rotated θj1 in
the clockwise direction by the turntable, synchronizing with the footmotion as shown by the dotted line, Pr looks to move only forward in thecoordinate B fixed on the treadmill.
We implemented this method on ATLAS. The visual motion
detecting system on ATLAS can measure the feet's motion in real time.
When a swinging foot moves in a lateral direction more than the a certain
threshold, it detects a turning motion. Simultaneously, the turntable rotates
the treadmill according to the following equation.
ω = α • X1
(1)
Here, we defined X 1 as lateral shift of the oblique step following

the previous step, Pr0, and ω as rotational speed. ‘α’ is the feedback gain
parameter. In this configuration, Corioli’s force and centrifugal force
are applied to the feet. The former force is proportional to the foot speed
and the latter force is proportional to the distance from the center ofturntable B. Since the walker’s position on the belt is controlled to benear B always [2] , we estimated that the centrifugal force is about one
fifth of the Corioli’s force while walking on ATLAS.
Figure 5 shows a typical time series graph of the results. The upper
two lines show the feet’ position along the X-axis in the coordinate B,
and the circled numbers indicate the order of the steps. The subject walked
straight in the first 7 steps during phase (A), then turned into right whilephase (B). He walked straight in phase (C) again and stopped at phase(D). The third line, the rotational angle of the turntable, shows that thetreadmill was rotating according to the turning motion in phase “B”. At
that time, a part of the shifted step was canceled as shown in the 8th 11th steps. One reason why it could not cancel during the motion was
due to the mechanical and the feedback delay of rotation. Revising thedelay, we expect to be able to predict turning motions from the motionof other parts of the body, such as hands, a waist and so on.
Another problem is that our method needs to rotate as the user turns
a corner. If s/he keeps turning right many times, the treadmill has torotate in the same angle also. Mechanical problems, however, limit the
maximum angle. Therefore, the system returns the treadmill to the neutral
angle while the user walks straight as shown in phases “C” and “D”. The
returning speed is slow enough not to affect the walking.

Conclusion
Using a treadmill and a turntable, we proposed a new method thatallows a user to walk in any direction as s/he likes. The trial
implementation could not cancel the entire turning motion because of asystem delay. We must revise the implementation and build into the TelE-merge system.

References[1] Miyasato, Nakatsu, “User Interface Technologies for a Virtual
Communication Space”, IEEE Computer Vision for Virtual Reality Based
Human Communications, pp105-110, 1998
[2] Noma, Miyasato, “Design for Locomotion Interface in a Large
Scale Virtual Environment, ATLAS: ATR Locomotion Interface for
Active Self Motion”, ASME-DSC-Vol.64, pp.111-118, 1998

Pl0,Pr0: Left and right foot positionat the end of n-th step
Pl,Pr: Left and right foot positionat the end of n+1-th stepwith turning motion.
θj1,ω : R o t a t i o n a l a n g l e a n d
speed of the treadmill.
B:
Fixed axis of coordinate on
the treadmill, and thecenter of rotation of thetreadmillFig. 4 Canceling turning motion on the treadmill when auser started turning in the right.

Fig. 5 Typical results on the trial ATLAS