The application discloses a multi-
sensor fusion SLAM positioning method based on a direct method, and relates to the field of
mobile robot positioning and navigation. The direct method is used for
camera tracking by using the pixel point information with obvious gradient in an image, IMU pre-integration information is used as an initial
pose, and the direct method is provided with an initial value. According to whether tracking is successful, the
image frame is divided into a
key frame and a non-
key frame. A visual
factor graph is constructed, an IMU residual term and a GPS residual term are inserted into the visual
factor graph to construct a new fusion
factor graph, and the optimization process of the
system algorithm is completed through fusion factor
graph optimization. A rear-end optimization strategy based on a sliding window optimization is used, the calculation complexity of rear-end
pose optimization is fixed, a multi-sensor tight
coupling fusion strategy is used, the advantages of marginalization are retained and the defects of marginalization are made up by using old information, and the
system accuracy is improved. The
system can work in a pure vision mode. Even if a GPS
signal cannot be normally received, the system can continue to work in a vision inertial
odometer mode.