Biomedical Engineering Reference
In-Depth Information
Figure 2
. The mechanical design of the Scorpion legs. This front view of the robot shows
the left and right side legs with the body in the center. Each leg consists of three joints: (i)
thoracic joint, (ii) basilar joint, and (iii) distal joint (right). The distal segment contains a
spring-damped compliant element with a built-in potentiometer to measure contact and load
on individual legs. The most energy-absorbing part in our design is a spring element inte-
grated in the distal segment of the leg. The distal spring element is also used to measure the
ground contact force by means of an integrated linear potentiometer. From this the robot
can compute the load on each leg. This enables us to make use of the principle of "Early
Retraction Acceleration" (described in (2,13)).
2.1. The Sensors
The robot is equipped with the following sensors that sense the internal
state, the so-called proprioceptive sensors:
& Motor encoders for each motor to measure the relative joint angle
& Hall-effect motor current sensors for each motor
& The analogue load/pressure sensor in each foot tip
& Power-management sensors, providing current battery voltage and cur-
rent power drain
& Three-dimensional inclinometers (pitch, roll, and yaw)
The following sensors to obtain information from the environment, so-
called exteroceptive sensors, are integrated:
