The paper "Preemptive Foot Compliance to Lower Impact During Biped Robot Walking Over Unknown Terrain" presents a novel method for ankle/foot compliance for biped humanoid robots walking over uneven terrain. Based on distributed plantar proximity sensing, we developed the Preemptive Foot Compliance (PFC) control that generates a Preemptive Ground Reaction Wrench that modifies the foot orientation to maximize the largest contact area to reduce the impact force produced at landing.
J. R. Guadarrama-Olvera, S. Kajita and G. Cheng, "Preemptive Foot Compliance to Lower Impact During Biped Robot Walking Over Unknown Terrain," in IEEE Robotics and Automation Letters, vol. 7, no. 3, pp. 8006-8011, July 2022, doi: 10.1109/LRA.2022.3187253.