Robotic Exoskeleton with Mechanically Implemented Kinematic Synergy for Quadrupedal Gait of Rats
Takayuki Miyamoto, Andrey Mikhailov, Modar Hassan, Sandra Puentes, Taichi Hiraga, Hideaki Soya, Kenji Suzuki
AI summary
Problem
Existing rat gait-assistive robots often force unnatural upright postures, lack ankle assistance, or lack backdrivability, hindering accurate neurorehabilitation studies and comparative translation to human therapies.
Approach
The system uses a 2-DOF bar mechanism to mechanically replicate the rat's natural kinematic synergy across the hip, knee, and ankle joints, with external direct-drive motors transmitting force via Bowden cables to maintain a quadrupedal posture.
Key results
- Replicated intact rat gait trajectories with minimal deviation and high interjoint coordination fidelity
- Achieved high backdrivability in both powered and unpowered states for safe physical interaction
- Successfully delivered synergistic gait assistance to an anesthetized rat on a treadmill
- Reduced lateral unit weight to 20 g and total wearable system to approximately 80 g
Why it matters
Provides a precise, safe animal testing platform to uncover neural recovery mechanisms and optimize human exoskeleton control strategies.
Abstract
This study introduces a novel kinematic synergy- based exoskeleton designed for gait rehabilitation studies in rats. The exoskeleton assists all three hindlimb joints of the rat (hip, knee and ankle) while ensuring proper interjoint coordination and the natural quadrupedal posture. This assistance is realized through a 2-DOF bar mechanism that emulates the biomechanics of rats. En- gineered to be compact, lightweight, backdrivable, and sufficiently powerful, the proposed system minimizes physical stress on the animal while allowing a wide range of assistive forces to be applied. These features are achieved through a combination of a cable power transmission system and direct-drive motors positioned outside the exoskeletal structure. The desktop experiments demonstrated that the exoskeleton could precisely replicate the rat’s kinematic gait patterns and remain backdrivable whether powered or unpow- ered. The feasibility of gait assistance was further confirmed in an anesthetized rat, where synergistic gait patterns were observed between the joints. Hence, the system holds the potential to enable controlled comparative neurorehabilitation studies in rats. These studies can help unveil neural recovery mechanisms and design optimal exoskeleton control strategies for rehabilitation in humans.