Robot joint with output end encoder and control method

The invention discloses a robot joint with an output end encoder and a control method. According to the robot joint with the output end encoder, a synchronous motor, a planetary reduction gearbox and the output end encoder arranged in a machine shell are integrated together to form the robot joint; meanwhile, a motor end encoder magnet is fixedly connected to the outer rotor holder, the angular displacement of the outer rotor holder can be measured through a motor controller, an output end encoder magnet in an output end encoder is fixedly connected to an encoder output gear, the angular displacement of an output flange is measured through an output end encoder circuit board, and the output end encoder magnet and the output end encoder circuit board are fixedly connected to the outer rotor holder. When the synchronous motor starts to start, the relative position of the output flange relative to the zero position is obtained, the relative position of the output flange cannot be lost even if the synchronous mot