Lightweight robots described by low weight, low payload capabilities and high motion dynamics
The challenge of autonomous walking with lightweight robots with a low payload capability is a
sophisticated dynamic problem. All sensor and actuator components as well as the onboard computer
have to selected carefully.
The low additional payload causes all
on board components to be well selected with respect to small
mass and as less as possible additional energy supply to reduce
the mass of the required batteries.
Our legged robots - humanoid and four-legged - are designed in a lightweight
The lightweight aspect here refers to software and
components for sensory, which runs with a good
performance on a robot with usually small payload,
but a sophisticated dynamic behavior. Typical
robots beside our legged robots are air vehicles.
They all have a tailored hardware as a light
on board computer, often with low computational
power, and inertial sensory as gyroscopes and accelerometers.
The mass in the robot, mainly caused by
the motors, is reduced as much as possible.
Our humanoid robot is
equipped with altogether 21 non-redundant servo motors, 6
arranged in each legs, 3 in each arms, 1 in the upper body
and two in the head. The motors are tailored for the challenge
of fast walking: The knees, which are highly stressed, are
equipped with the high-torque motors, the other motors are the conventional
servo motors for humanoid robots.
The robot is extended with two off-the-shelf CCD cameras
with different lenses. The cameras come with a plastic cover,
which is robust and lightweight.
Further on a three axes accelerometer and three one axis
gyroscopes are attached as inertial sensors with 100 Hz for
stabilization during walking motions by correction movements
mainly in the arms.
The control software is executed on a off-the-shelf Pocket
PC with integrated power supply.
The robot is powered by Lithium Polymer batteries, which have a good
The motor batteries are
placed in the feet to lower the center of mass of the robot.
The whole body stabilization is increased, whereas the rules
concerning the foot area with respect to the height of the center
of mass are are still fulfilled.
The robot frame partly consists of aluminum in the legs,
arm, and head holder, partly on carbon fiber reinforced plastic
in the upper body. The metal was chosen to give a basic
stability, whereas the plastic reduces the weight in less stressed
Our four-legged robots are constructed in a similar way.
They have an on board computer,
light servo motors and inertial sensors. The software is adapted
to the limited computational power.