Abstract:
Spring Loaded Pantographs (SLPs) are mechanisms that are often incorporated in the
design of lightweight legs for multi-legged robots. This is due to the fact that natural
quadruped (Four-Legged organisms) tend to keep the subsequent proximal and distal
seqments, of a 3-segment leg, mostly parallel during their locomotion. Cable-pulled SLP
legs have proven to be highly agile, robust and also depict energy storage capabilities.
However, In such designs the extension of the distal segments via the knee joint of the
leg are dependant upon the length of the cable. This thesis discusses the Elastically
Loaded Scissors (ELS) Mechanism, which is a variant of the SLP and its application in
the actuation of a bio-inspired robotic leg. Driven by ’pulling’ onto the proximal joint
of the scissors as opposed to the distal joint, this proposed leg utilizes the increased
mechanical advantage of the scissors mechanism to ’amplify’ input angles to larger output
displacement by the knee joint. Analysis and Simulations reveal that the proposed
mechanism operates in a larger range of motion as compared to the SLP mechanism.
However, the amplified motion comes at the cost of higher torque requirements of the
knee actuator. However, as the proposed mechanism is tendon actuated, loading due to
the weight of the robot decouple the actuator and shift the load onto the parallel elastic
components in a gravity compensation configuration. The claims made are validated by
experimentation using motion capture and power consumption measurement techniques
of the SLP and ELS configurations in a physical quadruped robot.
