Minho@Home
The
robot stands on a metal base locomotion platform and is moved by 4 omni-directional wheels perpendicularly arranged, for
greater manoeuvrability and control. The robot's locomotion module includes
four motors coupled with encoders, two motor controller boards (MD49), and a
main robot locomotion management board.
Figure 1 Ð Locomotion platform
The
robot tries to resemble the human body, in types of segments / members as well
as in terms of proportionality, being dimensioned based on a 1,60 meters tal individual. Its body is made up by segments of
polypropylene type lattice structure, with cover plates of the same material
for aesthetically appealing appearance.
The
activation of the lower limbs is carried out by the application of tension on
straps, recreating the rotational movement of the ankles, knees and basin, just
like a human being. Being the shins, the thighs and the trunk, lattice blocks
pivot in the connecting zones where the movement is made, a degree of freedom
of rotation in each connection, simulating the movement of several leg muscles
between which the twins, Femoral biceps, quadriceps and buttocks.
Figure 2 Ð First sketch of the robotÕs
structure
Also,
identical to a human physiognomy, the upper limbs present 2 degrees of freedom
of rotation from the trunk, i.e., in the shoulder relative to the human
anatomy. Recreating thus, the movement of the contraction of the deltoid
muscles, pectorals, trapezius and great dorsal of the human body. The link
between the forearm and the arm also presents a degree of freedom of rotation,
the elbow, recreating the movement of the biceps and triceps of the human body,
thus obtaining in the segments the main degrees of freedom present in the human
body.
Since the arm
is one of the few ways the robot uses to interact with humans and his
surrounding environment, it is fundamental to bear in mind some characteristics
such as:
á
Versatility
á
Precision
á
Reliability
á
Appearance
The hand
consists of 5 fingers, each one containing pressure sensors at their tips to
provide an additional insight when manipulating object and to allow the robot
to monitor the force exercised by its fingers. To increase the grip, the tip of
each finger is coated with silicone material.
The fingers
are controlled through servo motors, whose function is
to move nylon threads that simulate the tendons of the human arm. Each finger
demands a servo motor and the rotation of the wrist requires an extra one,
making a total of 6 servo motors for each hand-wrist set.
All
structures are made of PLA (polylactic acid) using 3D
printing technology. This method gives us the advantage of being able to
produce a greater number of parts at a reduced price as well as reduce the
waiting time whenever a new concept needs to be tested.
The first
wrist prototype has only roll and pitch axes, but another version which is
under development includes roll, pitch and yaw axes. On top of that, a new DOF
is given to the thumb. These improvements allow higher levels of freedom in the
movements, gives a more realistic look and significantly improves the
performance of object manipulation.
Figure 3 Ð Forearm example
It
is of extreme importance in this type of robots the requirement for voice
recognition, being vital in some cases to successfully perform the tasks for
which it is intended. Having that in mind, the recognition and interpretation
of a natural discourse makes the whole process of communication between the
human and the robot easier.
Currently,
CMU Sphinx tools from Carnegie Mellon University are used for speech
recognition. Essential words and phrases have been added to understand
different and new commands. When the recognition software finds a sequence of
keywords, the robot recognizes the action given by the human and processes acts
accordingly.
In order for the humans
to be able to establish a dialogue with the robot, it was necessary to
implement on the robot a module to allow responding through speech. For this
purpose, an Emic 2 module is used, to perform text to
speech conversion.
Figure 4 Ð Emic 2
For
robot vision a Kinect is used. With it, it is possible to obtain important data
for object recognition, object distance and colour, among others.
This
device is attached to the robotÕs head, making it another characteristic to
approach it to the human physiognomy. To attach the head to the robot body, a
neck has been developed that provides three degrees of freedom, allowing a
versatility of movements for image acquisition as adequate and stable as
possible.
Figure 5 - Kinect
Most
of the Data Processing is carried out by a set of PC, Microprocessor and
Microcontrollers. The Central Computing unit chosen for this task is a MSI Cubi 2, a Mini-Pc that became very advantageous for
numerous reasons namely: its small size, fast processing and integrated
peripherals.
Due
to the amount of different hardware involved in this type of robot, it is
almost a requirement to use ROS (Robotic Operating System). ROS offers a vast
set of out of the package tools.
The
implementation of ROS Nodes makes the intercommunication of all the robot
modules simpler and more reliable.
Figure 6 Ð MSI Cubi
2
A
LIDAR is used as a tool for localization taking into consideration the objects
that surround the robot and for a better perception of those, in order to analyse and decide the best path to travel
between two points.
Several
inertial sensors are used in the different members of the robot, so it can have
information about the position of all the robot members, such as the trunk, the
arms and the legs.
Figure 7 Ð Lidar
Figure 8 Ð First modulation of the structure
of the robot