Mutual Telexistence robot gTELESAR 2h


 Mutual Telexistence robot gTELESAR 2h is a master-slave robot composed
of the slave humanoid robot (Figure 1) that has the same size and structure
as human body and the exoskeleton type master cockpit (Figure 2) that controls
the slave humanoid robot.

 The size of the slave robot is 600mm in width, 600mm in depth, and 1,650mm in height. 
Its weight is 82kg.



  Figure 1  Slave humanoid robot


 The slave arm we developed was designed to be as light as possible in order
to move quickly and to be safe for human use. 

 By uniting the housing parts of the harmonic drive gear system with other
parts such as the rotational axes of joints, we made the whole mechanism of
the slave arm very light. 

 Moreover, by this design, we succeeded in making the arm mechanism as slim
as the outer human arm. 

 The distribution of the joints of the arm replicates the human arm's structure
in order to make it easy to be operated by telexistence using kinaesthetic 
sensation. 
 
 This structure is also useful for interaction with people without a sense of
incongruity.

 The force feedback is realized with the actuators distributed to each joint
of the master arm. The operator can feel the external power applied to the 
slave arm. 

 This robot system follows and enhances the concept of  gTELESARh developed
in this laboratory in 1989.

 In this research, as the best bilateral control method, the impedance control
type master-slave system is applied to the robot system.  



  Figure 2  Exoskeleton type master cockpit


 To facilitate the operator's arm motions, the master arm was designed as a
6-degree-of-freedom (DOF) structure, thus avoiding interference with the
operator's arm, particularly the elbow. 

 Since the measurable movement of the master arm that follows the operator's
hand has 6 DOF, we decided to use a new lightweight posture sensor composed of
an acceleration sensor to measure the final DOF, which is critical to identify
the posture of the operator's whole arm.

 The posture sensor is placed on the operator's upper arm.
 
 Altogether, the master arm serves as a master system of 7 DOF for measurement
of the arm's posture, and 6 DOF for force presentation. 

 Since the posture sensor is very light compared with mechanical restraints on
the operator's elbow, the sensor enables much freer movement of his or her arm
without any undesirable load on it. 

 We decided to use the exoskeleton structure because we considered that it could
be widely adapted for movement of an operator with minimal size requirements,
which is an essential characteristic to correspond to a human's various actions
in everyday life.

 The master hand of TELESAR 2 also has the exoskeleton type structure as shown
in Figure 3. We have developed an encounter-type master hand using circuitous 
joints to avoid collision with the operatorfs finger while the slave hand moves
in free space without touching outer environment. 

 The circuitous joint has a structure that extends the link length in proportion
to the joint angular displacement. When a finger of the slave hand touches some 
object, the finger of the master hand also touches the operatorfs finger to
provide force feedback.

 We derive a model to calculate motor torque in order to provide an operator with
desirable resistive forces for precise force feedback. 



  Figure 3  Left: Master hand   Right: Slave hand




  Figure 4  Three-dimensional displays for the master cockpit


 This master-slave robot system was presented as gTELEsarPHONEh at 
Prototype Robot Exhibition, EXPO2005 AICHI JAPAN.

 The exhibition booth for the slave robot is composed as shown in Figure 5.
There are two Retro-reflective projectors in this photograph. 



  Figure 5  Exhibition booth for the slave robot


 By peeping these projectors as shown in Figure 6, visitors can see the real
image of the operator on the body of the slave robot as shown in Figure 7 and
Figure 8.



  Figure 6  Visitor who looks into the Retro-reflective Projector




  Figure 7  Image of the operator that is projected to the slave robot




  Figure 8  Left: Master cockpit   Right: Slave robot


 The principle of Retro-reflective projection technology (RPT) is shown
in Figure 9. Under the RPT configuration, a projector is arranged at the
axial symmetric position of a userfs eye with reference to a half-mirror,
with a pinhole placed in front of the projector to ensure adequate of focus,
as shown in Figure 9. Image of the operator of the robot is projected onto
a screen that is covered with retro-reflective material. In the case of 
TELESAR 2, the screen is a face and a part of the robotfs body. 




  Figure 9  The principle of Retro-reflective projection technology (RPT)


 Figure 10 shows how a retro-reflective surface behaves. It is covered with
microscopic beads of about 50 micrometers in diameter, which reflect the 
incident light back to the incident direction. 
 The retro-reflector screen, together with the pinhole, ensures that the user
always sees images with accurate occlusion relations.



  Figure 10  Retro-reflective surface densely covered with microscopic beads


 In the future, we are going to make a small glass-size Retro-reflective
projector for Mutual Telexistense, and very smooth remote communications
with high sense of the operator's existence will be taken with this 
technology as shown in Figure 11.



  Figure 11  Image of Mutual Telexistence in the future






The video of TELESAR 2


1. Master-slave system of TELESAR 2(AVI format, 7.6MB)


2. Slave robot of TELESAR 2(AVI format, 3.2MB)


3. View of TELESAR 2 from Retro-reflective projector(AVI format, 9.5MB)


4. View of TELESAR 2 from Retro-reflective projector(AVI format, 5.6MB)


5. Mutual Telexistence(AVI format, 2.9MB)


6. Mutual Telexistence(WMV format, 7.7MB)






Future of TELESAR 2








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