Internal correction of dead-reckoning errors with the smart encoder trailer

This paper presents an innovative method for accurate mobile robot dead-reckoning, called Internal Posi tion Error Correction (IPEC). In previous work, the IPEC method was successfully implemented on a specially designed mobile robot with two differential drive axles, called the Multi-Degree-of-Freedom (MDOF) mobile robot. Experimental results with the MDOF robot showed consistently one to two orders of magnitude better dead-reckoning accuracy than systems based on conventional dead-reckoning. Yet, the IPEC system requires neither external references (such as navigation beacons, artificial landmarks, known floorplans, or satellite signals), nor inertial navigation aids (such as accelerometers or gyros). This paper focuses on our current efforts to implement the IPEC method on a device that can be added to any existing mobile robot. This device, called the "Smart Encoder Trailer" (SET), is a small, single-axle trailer with an incremental encoder on each of its two wheels. Although the SET is not functional yet, recent simulation results combined with experimental results from the (similarly configured MDOF vehicle) strongly suggest the feasibility of the SET implementation.