Abstract
An animal with a weakened limb does not necessarily switch its gait, instead it unloads the affected limb, re-coordinates the remaining limbs, and scales its response with injury severity. This graded adaptation allows locomotion to persist despite partial loss of limb strength, rather than requiring a discrete transition between healthy and failed. Inspired by this behavior, we propose SG-CPG, a central pattern generator (CPG) for quadruped locomotion under continuous actuator degradation. SG-CPG preserves a frozen healthy CPG policy and introduces two severity-driven gates: a residual gate that re-coordinates all four legs and an amplitude gate that progressively shortens the weakened leg's stride as degradation increases. We emulate progressive degradation through two mechanisms: lowering the joint torque ceiling (ceiling mechanism) and scaling its low-level controller gains (gain mechanism), representing distinct forms of actuator weakening. Our simulations on a Unitree Go2 show that SG-CPG maintains a trot gait with 100% survival across an omnidirectional command schedule under 95% joint strength loss while tracking commands within 8%. Under a lowered torque ceiling, removing either severity path, the residual's severity observation or the amplitude gate, raises clipping at the weakened joint from 4.4% to 13.6% and 26.3% of steps at an 80% loss. On a real Go2, SG-CPG survives 28 of 29 forward and turning trials with up to 93% calf torque degradation. These results show that severity-gated adaptation can extend a healthy locomotion policy to progressive actuator degradation without treating the fault as a discrete failure.
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Cite this article
APA 7
Kosta, A. K., & Roy, K. (2026). SG-CPG: Severity-Gated Central Pattern Generators for Adaptive Quadruped Locomotion under Continuous Actuator Degradation. https://omanscience.com/en/articles/sg-cpg-severity-gated-central-pattern-generators-for-adaptive-quadruped-locomotion-under-continuous-actuator-degradation
MLA 9
Kosta, Adarsh Kumar, and Kaushik Roy. "SG-CPG: Severity-Gated Central Pattern Generators for Adaptive Quadruped Locomotion under Continuous Actuator Degradation." https://omanscience.com/en/articles/sg-cpg-severity-gated-central-pattern-generators-for-adaptive-quadruped-locomotion-under-continuous-actuator-degradation.
Chicago (author–date)
Kosta, Adarsh Kumar, and Kaushik Roy. 2026. "SG-CPG: Severity-Gated Central Pattern Generators for Adaptive Quadruped Locomotion under Continuous Actuator Degradation." https://omanscience.com/en/articles/sg-cpg-severity-gated-central-pattern-generators-for-adaptive-quadruped-locomotion-under-continuous-actuator-degradation.
Harvard
Kosta, A. K. and Roy, K. (2026) 'SG-CPG: Severity-Gated Central Pattern Generators for Adaptive Quadruped Locomotion under Continuous Actuator Degradation', Available at: https://omanscience.com/en/articles/sg-cpg-severity-gated-central-pattern-generators-for-adaptive-quadruped-locomotion-under-continuous-actuator-degradation.
Vancouver
Kosta AK, Roy K. SG-CPG: Severity-Gated Central Pattern Generators for Adaptive Quadruped Locomotion under Continuous Actuator Degradation. https://omanscience.com/en/articles/sg-cpg-severity-gated-central-pattern-generators-for-adaptive-quadruped-locomotion-under-continuous-actuator-degradation
IEEE
A. K. Kosta, and K. Roy, "SG-CPG: Severity-Gated Central Pattern Generators for Adaptive Quadruped Locomotion under Continuous Actuator Degradation," https://omanscience.com/en/articles/sg-cpg-severity-gated-central-pattern-generators-for-adaptive-quadruped-locomotion-under-continuous-actuator-degradation.