Biomedical Engineering Reference
In-Depth Information
Finally, there is the IIT compliant humanoid COMAN which uses a combined
active and passive approach (Tsagarakis et al.
2009
,
2011b
; Li et al.
2012
).
The following sections will explore the design and construction of two robots
developed at IIT that have compliance at their heart: the electrically power passive/
active compliant humanoid COMAN and the actively compliant hydraulic
quadruped HyQ.
5.4 Humanoid and Quadruped Design and Construction
5.4.1 COMAN Humanoid Robot
The COMAN is derived from previous work on the lower body of the iCub
humanoid and the compliant biped cCub (Tsagarakis et al.
2007
,
2011a
,
2013
),
Fig.
5.7
. The height, at the neck, is 945 mm, although with a head this increases to
1.1 m (approx. the size of a 4-year-old child). The width and depth at the hips is
147 mm and 110 mm, respectively, and the distance between the centres of the
shoulders is 312 mm. The total weight of the robot is 34 kg with the legs/waist
weighing 18.5 Kg and the torso and the arms weighing 15.5 Kg.
COMAN has 31 DOF distributed across the body. Each leg has 6 DOF: 3 DOF at
the hip, 1 DOF at the knee level and 2 DOF at the ankle. For the trunk there is a
3 DOF waist, which gives greater flexibility than that provided by 1 or 2 DOF waist
mechanisms used in the majority of humanoids. Each arm has currently 7 DOF:
3 DOF at the shoulder, 1 DOF at the elbow level and 3 DOF at the wrist/forearm
(Table
5.1
; Figs.
5.8
and
5.9
).
Previous generations of humanoids have been position controlled robots with
excellent accuracy in the control of joint motions. This means that with accurate
models of carefully controlled environments, it is possible to achieve highly effec-
tive walking and even running, but when the contacts are unexpected or poorly
modelled, which are the prevailing conditions in most aspects of daily activity, the
robot can be unstable leading to damage to the robot or the environment (including
people). COMAN has the traditional high-fidelity joint position sensing but in
addition has high-fidelity torque sensors integrated in the motors of every joint
giving full active torque (compliance) regulation. This means that the robot can
respond precisely to the unmodelled contacts and collisions, but the use of active
torque sensing means that there are control bandwidth limitations which can still
cause impact problems. To further enhance the interaction capacity, passive com-
pliance based on series elastic actuation (SEA) is incorporated in 14 of the 25 DOF
including all flexion/extension DOF of the legs, the 3 DOF of the waist, the flexion/
extension of the shoulder and elbow and the shoulder abduction/adduction. This
gives COMAN unequalled tolerance to single and multiple, sequentially and simul-
taneously impacts and disturbances over all of the body [Li12]. The current system
does not have a head although a 2 DOF powered neck is included within the torso.
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