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has to follow some trajectory, which is usually generated from the configuration of surrounding obstacles;
movements of this type are basically used for reaching a specific pose (position and orientation) or for
passing through a narrow space. Fig. 3(a) shows the diagram for the subtask of moving to the position
where the robot can push a button.
Hand Motions Hand motions are described by its trajectory. They are usually implemented as sensor-
feedback motions. Fig. 3(b) shows the diagram for the subtask of pushing a button.
Sensing Skills A sensing operation is represented by a sensing skill. Sensing skills are used in vari-
ous situations such as detecting and recognizing objects, measuring properties of objects, and verifying
conditions on the geometric relationship between the robot and the objects.
Interactive Teaching Using Task Model
The robot tries to perform a task in the same way even in the case where some pieces of knowledge
are missing. When the robot cannot execute a motion because of a missing piece of knowledge, the robot
pauses and generates a query to the user for obtaining it. By repeating this process, the robot completes
the task model with leading the interaction with the user. It could be possible to examine the whole task
model before execution and to generate a set of queries for missing pieces of knowledge.
ANALYSIS OF TAKE-AN-ELEVATOR TASK
The take-an-elevator task is decomposed into the following steps:
(1) Move to the elevator hall from the current position. This step can be achieved by the free space
recognition and the motion planning ability of the robot (Negishi, Miura, and Shirai 2004), pro-
vided that the route to the elevator hall is given.
(2) Move to the place in front of the button outside the elevator, where the manipulator can reach the
button. The robot recognizes the elevator and localizes itself with respect to the elevator's local
coordinates. For the movement, the robot sets a trajectory from the current position to the target
position, and follows it by a sensory-feedback control.
(3) Localize the button and push it using the manipulator. The robot detects that the button is pushed
by recognizing that the light of the button turns on.
(4) Move to the position in front of the elevator door where the robot waits for the door to open.
(5) Get on the elevator after recognizing the door's opening.
(6) Localize and push the button of the destination floor inside the elevator, as the same as (3).
(7) Get off the elevator after recognizing that the door opens (currently, the arrival at the target floor is
not verified using floor signs inside the elevator).
(8) Move to the destination position at the target destination floor, as the same as (1).
Based on this analysis, we developed the task model for the take-an-elevator task. Fig. 4 shows that the
robot can take an elevator autonomously by following the task model.
TEACHING EXAMPLES
The robot examines the task model, and if there are missing pieces of knowledge in it, the robot
acquires them through the interaction with the user. Each missing piece of knowledge needs the corre-
sponding teaching procedure.
The above steps of the take-an-elevator task are divided into the following two parts. Steps (1) and
(8) are composed of free movements. The other steps are composed of guarded movements near the
elevator and hand motions. The following two subsections explain the teaching methods for the first and
the second parts, respectively.