Controllable sprag clutch and bidirectional overrun clutch thereby

The invention discloses a controllable sprag clutch and a bidirectional overrun clutch thereby. The controllable sprag clutch comprises an outer ring, an inner ring and a plurality of wedge blocks, wherein the inner ring and the outer ring are coaxially assembled; the plurality of wedge blocks are arranged between the outer ring and the inner ring to transfer power in one direction along a uniformdirection; two ends of each wedge block are independently provided with a cam structure abutted against the outer ring and the inner ring; and the outer ring or the inner ring is provided with a positioning groove for the cam of the wedge block on one end to be embedded and positioned by corresponding to a wedge block abutting position, and the wedge block swings around the cam on the end part and is pressed into the positioning groove through an elastic element. The controllable sprag clutch also comprises a control frame which pulls all wedge blocks to synchronously swing towards the same direction. The controllabl