Contact feedback helps snake robots propel against uneven terrain using vertical bending

Area of Science:

• Robotics
• Biomimicry
• Control Systems

Background:

• Snakes utilize lateral body bending for propulsion on flat surfaces, a mechanism well-replicated in snake robots.
• Vertical body bending enables snakes to traverse highly uneven terrain, but its control in robots remains poorly understood.
• Mechano-sensing feedback is hypothesized to aid snakes in adapting vertical bending for propulsion on varied terrain.

Purpose of the Study:

• To systematically investigate the role of sensory feedback control in snake robot propulsion using vertical body bending on uneven terrain.
• To compare the effectiveness of feedforward versus various feedback control strategies under different terrain conditions and loads.
• To understand how body weight influences propulsion and motor performance during vertical bending locomotion.

Main Methods:

• A snake robot equipped with force sensors was used to study vertical bending propulsion against large bumps.
• Feedforward and four distinct feedback controllers utilizing different sensory information were implemented and compared.
• The robot was subjected to increasing backward loads and novel terrain geometries to assess controller performance and robustness.
• The degree of body bending modulation (conformation vs. pushing) was varied to evaluate its impact on locomotion.

Main Results:

• Feedforward control achieved significant propulsion when bending shape matched terrain but failed under perturbations causing loss of contact.
• Contact feedback control successfully restored terrain contact and propulsion, resolving issues encountered by feedforward control.
• Excessive conformation to terrain interrupted shape propagation, while excessive pushing led to frequent motor stalling.
• Body weight aids contact maintenance but can also overload motors during vertical bending propulsion, unlike in lateral bending.

Conclusions:

• Sensory feedback control is essential for robust vertical bending propulsion in snake robots on uneven terrain.
• Optimizing feedback control strategies, balancing conformation and pushing, is key to efficient and safe locomotion.
• Understanding these principles can inform the design of more capable snake robots and provide insights into biological snake locomotion.