Active knee-lock release for passive-dynamic walking machines. - Kalin B. Trifonov; Shuji Hashimoto (ROBIO, 2007)

Active knee-release mechanism for passive-dynamic walking machines and walking cycle research. - Kalin B. Trifonov; Shuji Hashimoto (IROS, 2008)

Incremental development of a passive-dynamics-based walking machine. - Kalin Boykov Trifonov; Shuji Hashimoto (ROBIO, 2008)