1、A precise curved motion planning for a differential driving mobile robotabstract A single curvature trajectory with a fixed rotation radius is proposed for an optimal trajectory plan for a differential driving mobile robot to capture a moving object. Generally, when the differential driving mobile r
2、obot moves along a path whose rotation radius is not constant, the tracking error of the mobile robot increases with the travel distance. Also, tracking errors increase greatly when the mobile robot follows a trajectory, with a small rotation radius. Based on these two observations, a single curvatu
3、re trajectory, which has a constant and large rotation radius, is proposed as an optimal trajectory, in order to minimize the tracking error of the differential driving mobile robot. This paper first reviews the characteristics of a single curvature trajectory. Next, an algorithm to capture a moving
4、 object precisely is proposed using the single curvature trajectory. With the pre-determined initial states (i.e., position and orientation of the mobile robot and the final states), the mobile robot is made to capture a moving object.Through simulations and real experiments using a two DOF wheel-ba
5、sed mobile robot, the effectiveness of the proposed algorithm is verified.1. Introduction Research on mobile robots can be globally classified into three categories: path planning, position estimation, and driving control. The trajectory planning of a mobile robot aims at providing an optimal path f
6、rom an initial position to a targetposition. Optimal trajectory planning for a mobile robot provides a path, which has minimal tracking error and the shortest driving time and distance. Tracking errors of mobile robots cause collisions with obstacles due to deviations from the planned path and also
7、cause the robot to fail to accomplish the mission successfully. Tracking error can be reduced through feedback control. However, this requires excessive control efforts due to high control gains. Tracking errors also cause an increase of traveling time, as well as travel distance, due to the additio
8、nal adjustments needed to satisfy the driving states. Therefore, trajectory planning to decrease tracking error is very important and needs to be handled carefully. One of the major reasons for tracking error is the discontinuity of the rotation radius on the path of the differential driving mobile
9、robot. The rotation radius changes at the connecting point of the straight line route and curved route, or at a point of inflection. At these points, it can be easy for the differential driving mobile robot to secede from its determined orbit due to the rapid change of direction. Therefore, in order
10、 to decrease tracking error, the trajectory of the mobile robot must be planned so that the rotation radius is maintained at a constant , if possible. The increase of tracking error due to the small rotation radius interferes with the accurate driving of the mobile robot. The path of the mobile robo
11、t can be divided into curved and straight-line segments, globally. While tracking error is not generated in the straight-line segment, significant error is produced in the curved segment due to centrifugal and centripetal forces, which cause the robot to slide over the surface. Also, tracking error
12、increases when the rotation radius is small. In fact, the straight line segment can be considered as a curved segment whose rotation radius is infinity. As the tracking error becomes larger at the curved segment, the possibility of a tracking error increases with the decrease of the rotation radius
13、of the curved path. Note that a relatively small error occurs at the straight-line path. Therefore, it is important to maintain simultaneously a large and constant rotation radius in order to decrease the tracking error of the differential driving mobile robot. This paper proposes a single-curvature
14、 trajectory, which has a constant and large rotation radius. In view of the size and discontinuity of the rotation radius,a single-curvature trajectory and a double-curvature trajectory are compared to show that the tracking error increases with the decrease of the rotation radius. Through the track
15、ing experiments along each trajectory, it is proved that a single-curvature trajectory has the least tracking error. With precise trajectory planning, an algorithm for the mobile robot to capture a moving object is proposed. With the pre-specified initial position and orientation of a mobile robot a
16、nd the final states, and assuming that the velocity of the moving object is pre-estimated, an optimal capturing path of a mobile robot is produced as a result of this research. In Section 2, the driving characteristics of a mobile robot are analyzed using a kinematics analysis while the mobile robot is making curved motions. The single-curvature trajectory and double-curvature trajectory are described in detail in Sect
