Positioning Method of Four-Wheel-Steering Mobile Robots Based on Improved UMBmark of Michigan Benchmark Algorithm

To reduce the error of the odometer positioning sys-tem and improve the positioning accuracy of four-wheel-steering mobile robots, three types of coupling errors are considered, based on the University of Michigan Benchmark (UMBmark) method: unequal track width, unequal wheel diameter, and speed dif-ference of ipsilateral wheels. A "dual direction square path experiment" is designed to decouple the error, a new system error model is defined, and an improved UMBmark method for a four-wheel mobile robot is proposed. In the mobile robot positioning system, a laser tracker is used to measure the absolute positions of the starting and ending points of the robot. The po-sitioning test results of the robot using the improved UMBmark method show that the odometer system er-ror is 69.103 mm, which is 2.6 times less than that in the traditional UMBmark method. Hence, the im-proved UMBmark can better compensate for the sys-tem error of four-wheel-steering mobile robots.