INTERNAL CORRECTION OF DEAD-RECKONING ERRORS WITH A DUAL-DRIVE COMPLAINT LINKAGE MOBILE ROBOT

This paper presents internal position error correction (IPEC)-a new method for accurate and reliable dead-reckoning with mobile robots. The IPEC method has been implemented on our recently developed multi-degree-of-freedom (MDOF) mobile platform, a vehicle in which two differential-drive mobile robots (called ''trucks'') are physically connected through a compliant linkage. In addition to its four wheel encoders, the MDOF platform has one linear and two rotary internal encoders, which allow measurement of the relative distance and bearing between the two trucks. During operation, both trucks perform conventional dead-reckoning with their wheel encoders. But, in addition, the IPEC method uses information from the internal encoders to detect and correct dead-reckoning errors as soon as they occur. Our system, called compliant linkage autonomous platform with position error recovery (CLAPPER), requires neither external references (such as navigation beacons, artificial landmarks, known floorplans, or satellite signals), nor inertial navigation aids (such as accelerometers or gyros). Nonetheless, the experimental results included in this article show one to two orders of magnitude better positioning accuracy than systems based on conventional dead-reckoning. The CLAPPER corrects not only systematic errors, such as different wheel diameters, but also non-systematic errors, such as those caused by floor roughness, bumps, or cracks in the floor. These features are made possible by exploiting the new growth-rate concept for dead-reckoning errors that is introduced in this article for the first time. The growth-rate concept distinguishes between certain dead-reckoning errors that develop slowly and other dead-reckoning errors that develop quickly. Based on this concept, truck A frequently measures a property with slow-growing error characteristics on reference truck B (thus admitting a small error) to detect a fast-growing error on truck A (thus correcting a large error), and vice versa. (C) 1995 John Wiley & Sons, Inc.