Proceedings of the 2019 IEEE/SICE
International Symposium on System Integration
Paris, France, January 14-16, 2019

Development of an Inflatable Robotic Arm on Mobile Platform
for Fetch-and-Give Tasks
Ryosuke Tatara1 , Naoki Nomaguchi1 , Akihiro Kawamura2 , Ryo Kurazume2 and Sadao Kawamura3
Abstract— This paper proposes a novel inflatable robotic arm
on a mobile platform. To date, inflatable structures have beenutilized for robotic arms to provide the workforce in the welfare
and nursing care fields. In these fields, inflatable robots, which
is lightweight, soft and compactable, is suitable to performdaily tasks near humans and things because of safe contact.
In our research group, an inflatable robotic arm consisting ofinflatable links, inflatable actuators and a gripper with pleatedsheet structures have been developed.
In this paper, the robotic arm is utilized in combination witha mobile platform in order to realize practical daily tasks. As
an example of the task, a fetch-and-give task is demonstrated.
The posture of the robotic arm and the position of the mobileplatform is measured by a motion capture system. The wholesystem is controlled based on the visual information. Finally, it
is confirmed that the inflatable robot has sufficient performancefor a daily task in living space.

I. INTRODUCTION
To date, inflatable structures have been utilized for roboticarms to provide the workforce in the welfare and nursing care fields. In these fields, robotic arms composedof inflatable structures is suitable to perform daily tasks
near humans and things due to their features: lightweight,
soft and safe. Therefore, many robotics researchers havedeveloped inflatable robotic arms [1]–[7]. Sanan et al. havedeveloped inflatable link and proposed a method to control
its contact force [1], [2]. Viosembert et al. have proposeda mechanical design using an inflatable structure whichconnects links and joints continuously [3], [4]. Ronghuai etal. have developed a telepresence robot that has inflatablerobotic arms for human-robot interaction [5]. The robot isable to mimic human behavior and realize remote interaction.
In particular, manipulation tasks with the use of a mobile
platform such as fetch-and-give tasks have been conductedby some researches. A compactable inflatable robotic arm
on a mobile platform which is called AIRarm prototype
has been proposed by iRobot in DARPA challenge [8].
However, experimental verification of practical usefulness
and detail of the performance of the robot has not beenreported sufficiently.
1 Ryosuke

Tatara and Naoki Nomaguchi are with Graduateof Information Science and Electrical Engineering,University, Fukuoka, JAPAN tatara, nomaguchi

SchoolKyushu@irvs.ait.kyushu-u.ac.jp
2 Akihiro Kawamura and Ryo Kurazume are with Faculty of Information
Science and Electrical Engineering, Kyushu University, Fukuoka, JAPANkawamura, kurazume@ait.kyushu-u.ac.jp
3 SadaoandKawamura is with Graduate School ofEngineering,
Ritsumeikan
University,Shiga,

kawamura@se.ritsumei.ac.jp

978-1-5386-3615-2/19/$31.00 ©2019 IEEEScienceJAPANFig. 1.

Inflatable robotic arm on a mobile platform in living space

Our research group has been focusing on inflatable structure and developed an extremely lightweight and soft inflatable robotic arm using plastic materials for all components[9], [10]. However, the performance of the robot has been
evaluated by simple PTP control. The performance of daily
practical tasks has not been discussed and confirmed. Therefore, the purpose of this paper is to experimentally verify
the practical performance of the robot. A mobile platform
is attached to the robotic arm to extend its range of motion
and to perform various tasks. The whole system is controlled
by using Robot Operating System (ROS) and illustrated inFig. 1. Finally, it is confirmed that the inflatable robot has
sufficient performance for daily tasks in living space by thefetch-and-give task as an example of a practical experiment.
In the following, we first introduce the whole system
including the inflatable robotic arm and a mobile platform.
Next, the control method of the robot system is proposed.
Finally, the fetch-and-give task experiments are reported.
II. OVERALL SYSTEM
This section introduces the overall system composed of an
inflatable robotic arm and a mobile platform. The appearanceof the system is shown in Fig. 1.
A. Inflatable robotic arm
The robotic arm consists of pneumatic bag actuators, links
with an inflatable structure, a robotic gripper with pleatedsheet structures. All of them are made of plastic materials
which have many advantages such as lightness, softness andsafety. The weight of a link is about 50 g and the weightof an actuator is from 90 g to 120 g which depends on thenumber of bags. The total weight of the robotic arm and707

Fig. 4.

Fig. 2.

Robotic gripper using a pleated sheet structure

Inflatable links and actuators, and the robot’s size

Fig. 5.
Fig. 3. DOF configuration of the inflatable robotic arm (In this research,θ0 is constant value 45◦ .)the gripper excluding the pedestal is only 340 g. Significantweight reduction is achieved compared with a conventional
robotic arm made of metal.
The actuators and the links are made by welding polylaminated sheets and low-density polyethylene (LDPE)
sheets. The poly-laminated airbag has high-pressure resistance and is laminated outside of a LDPE airbag. The
pressure resistance of the overlaid structure is approximately
300 kPa.
The links maintain rigidity by pressurizing in a cylindricalshape. The actuator is constructed by accumulating from 6
to 8 pouch-shaped inflatable bag unit. The joint torque isgenerated by two actuators arranged antagonistically insideand outside of each joint. Figure 2 shows the links andactuators. The DOF configuration of the robotic arm is shownin Fig. 3. The robotic gripper is made by using pleated sheet
structures. Figure 4 shows the gripper. The pleated structure
is a bag-like structure, where the back side of the gripper isfolded. Different expansion ratio between the flat part and thefolded part enables it to grasp objects and release by its own
plasticity. The load capacity of the gripper is approximately700 g. The position of the gripper is measured by a motion
capture system Vero (Vicon Motion Systems Ltd.).
B. Mobile platform
In this research, a mobile platform, Chairbot (SustainableRobotics Inc.), is installed. This platform is a two-wheeled

Whole hardware systemvehicle and controllable by using ROS. The position of themobile platform is also measured by the motion capturesystem Vero.
Totally, the overall system architecture is illustrated in Fig.
5.
III. CONTROL METHODSThis section shows the control method of the robot system
which consists of the inflatable robotic arm and the mobileplatform.
A. Inflatable robotic arm
The inflatable robotic arm is controlled by the combinationof pressure and visual feedback controls. In visual feedback
control, the position of the robotic gripper r is controlledusing the following equations∫{}dτv = J T (θ) KP v ev (t)+KIv ev (t)dt+KDv ev (t) (1)dteV (t) = rt − r

(2)

where
τv = (τv1 , τv2 , τv3 , τv4 )T : Desired torque for visual feedback control
J 3×4 (θ) : Jacobian matrix
rt = (xt , yt , zt )T : Target gripper positionr = (x4 , y4 , z4 )T : Current gripper position
KP v , KIv , KDv : Proportional, integral and differential gainof pressure feedback control.
The gripper position is measured by tracking reflection708

markers using the motion capture system as shown in Fig.
4.
The desired torque is calculated by adding the gravity
compensation torque τg to the PID torque τv asτ = τv + τg(3)whereτ = (τ1 , τ2 , τ3 , τ4 ) : Desired torque.
Then, the torque-pressure conversion is performed using aconversion function A(θ) acquired from preliminary experiments. The conversion from desired torque to target pressure
is calculated as
1
Pt = Pb ± A(θ)τ
2Fig. 6.

Experimental environment(4)

whereA(θ) : Conversion function
Pt : Target pressure
Pb : Base pressure.
Finally, the compensated target pressure by pressure feedback control are given as follows:∫d
P = Pt +KP p ep (t)+KIp ep (t)dt+KDp ep (t) (5)dtep (t) = Pt − Ps(6)where
P : Compensated target pressure
Ps : Pressure acquired by a pressure sensor
KP p , KIp , KDp : Proportional, integral and differential gainof pressure feedback control.
B. Mobile platform

Fig. 7.

The self-position of the mobile platform is acquired by
the motion capture system installed in the experimental room
imitating living space. The environmental map of the room
is obtained previously. The target position of the mobile
platform needed for manipulation is calculated using target
position for robotic arm rt = (xt , yt , zt )T as follows:(xmym)(=1 00 1−lm cos θm−lm sin θm)xt
 yt 1(7)whererm = (xm , ym )T : Target position for the mobile platform
lm : Target distance from the center of the mobile platform
to the object
θm : Target angle for the mobile platform.
In this system, a global path is generated by means of Dijkstra method before moving. When the robot is moving, thelocal path is generated in real time using Dynamic Window
Approach (DWA). This platform is basically operated byusing ROS (Robot Operating System).

Snapshot of the fetch-and-give task

IV. EXPERIMENTS
In this section, a fetch-and-give task in living space isperformed as an example of daily practical applications. In
the experimental environment in Fig. 6, eight motion capture
camera are mounted up to surround the room. The target
object is a plastic bottle whose weight is 100 g, and it isplaced on the table. The reflective markers attached to theobject is traced by the motion capture system. The robot
starts from the initial position, moves to the table, picks thebottle up, moves to the bed and gives it to the target person
sitting on the bed, as shown in Fig. 7. Figures 8 and 9
show the global paths of the mobile platform using Dijkstra
method. Figure 10 shows the actual trajectory from theinitial state to the goal state. In these figures, the red arrows,
green lines and black dots represent the target postures,
global paths and actual trajectory respectively, which arevisualized by RViz. Furthermore, Fig. 11 show the time
variation of the position of the robotic gripper. The bluelines and the orange lines show the desired position and709

Fig. 8.

Global path to the tableFig. 9.

Fig. 11.

Global path to the bedFig. 10.

Trajectory of the mobile platform

Time variation of the position of the robotic gripper

the actual trajectory respectively. It is confirmed that theposition of the gripper converges to the desired position ineach motion. Finally, it is verified that the performance of thenewly developed robot is adequate to execute the fetch-andgive task. The experiment is repeatedly executed ten times.
As a result, the fetch-and-give task is achieved nine times.
The one failure is caused in the moving phase of the mobileplatform. Therefore, the usefulness of the inflatable roboticarm to realize manipulation tasks in daily life is verified by
the results.
V. CONCLUSIONSIn the paper, we proposed an inflatable robotic arm on amobile platform. The purpose of this paper is to experimentally verify the performance of the inflatable robotic arm forapplications in daily lives. The performance was confirmedby experiments of a practical daily task, fetch and give task.
The proposed robot system is able to move and manipulate
objects appropriately.
In future work, we will build a self-contained robot systemequipped with an air tank and a communication module.
Moreover, we will realize more diverse applications suchas manipulation of various things and assistance for people
with disabilities.
ACKNOWLEDGEMENTS
This research is supported by the Japan Society for thePromotion of Science Grant-in-Aid for Basic Research (B)(JP18H03764).

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