Abstract: The present application discloses an adjustment assembly and a headrest. The adjustment assembly includes: a guiding rod; a fixing member, fixed to an end of the guiding rod; a driving portion, movably connected to the fixing member; and a first screw, engaged to the fixing member with threads, and the driving portion is connected to the fixing member by the first screw, wherein the driving portion includes a first motor, and the first motor is used to drive the driving portion to linearly move in respect to the fixing member along a direction close to or away from the fixing member. The adjustment assembly of the application can be adjusted electrically, such that the operation is convenient, and the structure is simple and reliable.

Abstract: The present application discloses a locking device comprising: a housing; a plunger inserted into the housing, movable and rotatable to transit between a locking position and an unlocking position, wherein when the plunger is in the unlocking position, the plunger is in a first rotating position and a first axial position, when the plunger is in the locking position, the plunger is in a second rotational position and a second axial position; a rotor accommodated in the housing and rotatable around a rotor rotation axis relative to the plunger between a engaged position and a disengaged position, wherein when the plunger is in the locking position, the rotor is rotatable to the engaged position to prevent the plunger from moving; and a motor accommodated in the housing and configured to drive the rotor to rotate. The present application further discloses a locking system.