Biomedical Engineering Reference
In-Depth Information
Ethernet network. Data are acquired and synchronized (and time stamped) before
being made available on the network. We designed the software middleware that
supports data acquisition and control of the robot as well as all the firmware that
operates on the microcontrollers which eventually drive each single transistor that
moves the motors.
The software middleware is called YARP (Fitzpatrick et al.
2008
). YARP is a
thin library that enables multi-platform and multi-IDE development and collabo-
ration by providing a layer that shields the user from the quirks of the underlying
operating system and robot hardware controllers. The complete design of the iCub
(drawings, schematics, specifications) and its software (both middleware and con-
trollers) is distributed according to the GPL and LGPL licenses.
6.2.1
iCub 2.0
More recently we released an updated version of the iCub which shares some of the
advanced mechatronic solutions for the bodyware already described in Chap.
5
for
the compliant robot Coman (such as the new legs with series-elastic actuators—
SEAs), a new industrially viable version of the skin sensors, and a new version of
the microcontroller cards with Ethernet connectivity [for a complete description,
see Parmiggiani et al. (
2012b
)]. Almost all subsystems were affected including a
new head design, a consistent revision of the hands especially in the routing of the
cables for improved durability, a new version of the skin, and electronics with
Ethernet connectivity. Simultaneously we “ported” certain features of Coman,
more specifically the SEAs, to the iCub. We included a SEA joint at the knee and
ankle, high-resolution encoders in the SEA for torque control, the removal of the
cable at the ankle, and an overall improvement by simplifying the design with
respect to both the original iCub and Coman.
Previous experiments with Coman allowed determining a suitable value for the
torsional stiffness of the elastic modules. The optimal value was found to be in the
range of 300-350 [Nm/rad]. Being the maximum leg actuator torque in the ballpark
of 40 [Nm], the required passive angular deflection of the SEA which permits the
delivery of the peak torque within the elastic deflection range is in the order of
0.1333 [rad]. The elastic module of Coman however did not allow to obtain such
torsional stiffness values. During experimentation, the elastic deflection limit was
reached at about 50 % of the maximum torque, canceling the benefits of the
integration of the SEA modules. We therefore considered possible alternative
designs of the elastic components. As described in Tsagarakis et al. (
2011
), the
elastic module of Coman comprises three pairs of opposing helical springs. We
considered the substitution of the springs with a different set of helical springs, disk
springs, and volute springs while keeping the overall mechanics as close as possible
to the original size. We considered a different design comprising leaf springs. The
“stiffness envelopes” of the different alternatives are represented in Fig.
6.2
panel
(a). None of them allowed obtaining the desired torsional rigidity. The selection of
Search WWH ::
Custom Search