Method for tracking movement of a mobile robotic device

A robotic device, comprising:

• a chassis;
• a set of wheels coupled to the chassis;
• one or more electric motors for rotating the set of wheels;
• one or more tools for performing work coupled to the chassis;
• a processor electronically coupled to a plurality of sensors;
• and
• a tangible, non-transitory, machine readable medium storing instructions that when executed by the processor effectuates operations comprising:
• capturing, with a visual sensor, visual readings to objects within an environment of the robotic device as the robotic device moves within the environment;
• capturing, with an encoder sensor, readings of wheel rotation indicative of displacement of the robotic device;
• capturing, with an optoelectronic sensor, readings of a driving surface of the environment of the robotic device;
• capturing, with a depth sensor, distances to obstacles as the robot moves within the environment;
• determining, with the processor, displacement of the robotic device in two dimensions based on the optoelectronic sensor readings of the driving surface;
• determining, with the processor, a difference in displacement between the displacement determined based on the encoder sensor readings and the displacement determined based on the optoelectronic sensor readings of the driving surface, the difference in displacement being indicative of slippage;
• estimating, with the processor, a corrected position of the robotic device to replace a last known position of the robotic device, wherein:
• estimating a corrected position of the robotic device occurs if the processor loses or reduces knowledge of a current position of the robotic device in relation to a global frame of reference of the environment of the robotic device when the robotic device moves along a path from the last known position to a new intended position while performing work using the one or more tools;
• the processor creates or updates an ensemble of simulated positions of possible new locations of the robotic device wherein some elements of the ensemble are based on the readings of wheel rotation from the encoder sensor and the displacement readings determined from the optoelectronic sensor readings;
• determining, by the processor, a most feasible element in the ensemble based on the visual readings;
• and
• determining, by the processor, a most feasible position of the robotic device as the corrected position based on the most feasible element in the ensemble and the visual readings.