Under-actuated bipod walking robot hip-joint mechanism

The invention relates to a hip joint mechanism of an underactuated biped walking robot, which can conveniently realize the smooth switch of an on-line driving state and an off-line no-driving state and is beneficial to the high-efficiency walking control of the underactuated biped walking robot. The technical proposal is as follows: an angular bisector mechanism (1) which consists of two sets of positive and reversed gear-chain groups and a free transmission shaft (9) leads the rotational motions of the two legs around the hip joints to be linked with the motion of the upper body, and limits the upper body at the angular bisector of the two legs; a hip joint device mounting plate (2) is fixed with the upper body of the robot; a bidirectional drive system (3) consists of two sets of driving motors which finally convert the output moment of a motor into the relative moment between the two legs, a transmission shaft and a steel rope; and an incomplete gear transmission system (4) comprises a driving motor (13) as well as a reducer and an incomplete driver gear (12) which are arranged on the output shaft of the driving motor.