Yamada, H., Kawamura, T., and Ootsubo, K.

Development Report:

Development of a Teleoperation System for a Construction Robot
Hironao Yamada, Takuya Kawamura, and Katsutoshi Ootsubo
Department of Mechanical Engineering, Faculty of Engineering, Gifu University
1-1 Yanagido, Gifu City 501-1194, Japan
E-mail: {yamada, tkz-kawa13, otsubo}@gifu-u.ac.jp[Received October 26, 2013; accepted December 3, 2013]

In this report, we introduce the development of a teleoperation system for a construction robot. The system
is based on master-slave control, and consists of existing hardware, including hydraulic actuators. We propose presentation methods to provide a realistic presence at a real field, and confirm the validity of our system with experiments.

Keywords:
construction robot, hydraulic actuator,
master-slave control, teleoperation, virtual reality
Fig. 1. System framework.

1. Introduction
A construction robot generally includes some actuators,
and has sufficient power to carry out tasks that are difficult for humans. The application of such robots in environments that are dangerous for humans such as disaster scenes, space and the deep sea ground is becoming
more and more important. Teleoperation is the most effective method of controlling these robots, and teleoperation systems are now developed at a variety of research
institutes and companies. However, conventional teleoperation systems do not satisfy requirements of realisticpresence and operability. Therefore, we have developed
a new system based on hydraulic actuators that satisfies
the requirements.

2. Teleoperation SystemThe system hardware consists primarily of a servocontrolled construction robot with hydraulic cylinders,
two joysticks for operating the robot from a remote place,a 3-degree-of-freedom (3-DOF) motion base, and some
type of visual sensor such as a charge-coupled device(CCD) camera or stereo vision camera (Fig. 1). The slaveis the fork glove, and the master is the joysticks handled
by the operator. The operator moves the joysticks whilelooking at visual information provided by the slave. Signals from the master then move hydraulic cylinders todrive the corresponding fork glove, arm, boom and swing.
Fig. 2 shows the present experimental facility.

110Fig. 2. Experimental facilities.

3. Control of the Motion Base System
In order to simulate a kinematic presence in the workarea, we developed a 3-DOF motion base, and propose
a control method based on three acceleration sensors [1].
The motion base has a 3-axis parallel mechanism driven
by a 3-part leg assembly, each leg of which consists of apantographic link and a hydraulic cylinder servo system.
It simulates the posture of the robot by controlling the link
displacement according to acceleration data. This allows
the operator to experience a highly realistic presence as if(s)he were sitting on the seat of the robot.

Journal of Robotics and Mechatronics Vol.26 No.1, 2014

Development of a Teleoperation System for a Construction Robot

4. Master-Slave Control Method
We propose a master-slave control method [2] in orderto create a realistic sense of force in the teleoperation. In
our system, the joysticks have a DC servo motor, and theuser experiences a reaction force via the joysticks whengrasping an object with the fork glove. Each cylinder
is subject to feedback control via a proportional control
valve, and pressure sensors are attached to them. Thesesensors send signals to the master in real time, and thesignals are then converted to force signals. We propose
a variable-gain symmetric-position control in order to robustly obtain a reaction force when grasping objects ofdifferent hardnesses. We also propose control methods
based on the reaction force [3, 4], in order to allow theoperator to experience a reasonable sense of grasping objects.

5. Visual Presentation Method
Conventional teleoperation systems depend solely oncolor video images captured by a normal camera on therobot. Our presentation method is based on computergraphics (CG) images from a stereo vision system on therobot [5], and it provides real-time range images of theremote field. A task object is recognized from the images, and its 3D geometry is reconstructed. The object
and the robot are presented by 3D-CG to the operator. Images can be seen from the desired position and direction inthe virtual space of the remote field. Recently, we developed a presentation method based on augmented reality(AR) [6] (Fig. 3). In its implemented system, a 3D-CG
image that augments the recognition precision of real objects is created by processing a normal video image. The
image overlaps the video image in real time, helping theoperator to perform operations accurately.

6. Conclusion
In this report, we introduce a part of our study on thedevelopment of a teleoperation system for a construction
robot. In future research, we will attempt to augment therealistic presence of its operation by processing the data
provided by a sensor such as a range scanner.

Journal of Robotics and Mechatronics Vol.26 No.1, 2014

Fig. 3. AR presentation for a operational support.

References:[1] D. Zhao, Y. Xia, H. Yamada, and T. Muto, “Control Method forRealistic Motions in a Construction Tele-Robotic System with a
3-DOF Parallel Mechanism,” J. of Robotics and Mechatronics,
Vol.15, No.4, pp. 361-368, 2003.
[2] H. Yamada, H. Kato, and T. Muto, “Master-Slave control for Construction Robot Teleoperation,” J. of Robotics and Mechatronics,
Vol.15, No.1, pp. 54-60, 2003.
[3] L. Huang, T. Kawamura, and H. Yamada, “Master-Slave ControlMethod with Force Feedback for Grasping Soft Objects Using aTeleoperation Construction Robot,” Int. J. of Fluid Power, Vol.13,No.2, pp. 41-49, 2012.
[4] A. A. Yusof, T. Kawamura, and H. Yamada, “Evaluation of Construction Robot Telegrasping Force Perception Using Visual, Auditory and Force Feedback Integration,” J. of Robotics and Mechatronics, Vol.24, No.6, pp. 949-957, 2012.
[5] H. Yamada and T. Muto, “Construction Tele-Robotic System withVirtual Reality (CG presentation of virtual robot and task object
using stereo vision system),” J. of Control and Intelligent Systems,
Vol.35, No.3, pp. 195-201, 2007.
[6] K. Ootsubo, T. Kawamura, and H. Yamada, “Construction TeleRobotics System with AR Presentation,” J. of Physics: Conference
Series, Vol.433-012029, 2013.

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