Optimal Smooth Paths Based on Clothoids for Car-like Vehicles in the Presence of Obstacles

Abstract

Automated Guided Vehicles are increasingly used for material transfer in factory and warehouse environments amongst humans and human operated vehicles. Safe and efficient operation is challenging when there is a mix of human and automated traffic as fixed guide paths can become blocked more frequently. In this work we aim to show smooth and efficient paths based on clothoid curves can be used to automatically plan diversions which can be traversed at high speed by automated fork-lift vehicles, which are car-like in the sense they have a limited turning radius and angular acceleration. The approach, based on numerical optimisation within convex region constraints is described in detail, and numerical results for curvature and sharpness are compared to a cubic spline on a small number of simulated environments. The clothoid spline is less affected, in terms of its objective function, by a shift in the obstacle boundaries than a cubic spline, for obstacle shifts below 0.5m. The clothoid spline takes longer to converge for but the output path has attractive qualities like lower peak sharpness, enabling high speed operation. The method is therefore most useful for applications where path quality is important and updates are required less frequently. Changing the objective function by increasing weighting parameter b allowed the path shape to be tuned to reduce the peak sharpness, at the cost of increasing the total length. With b > 100, convergence was poor because parts of the spline were pushed outside the assigned region, an artefact arising from the constraints only being enforced at the start and end of each segment. The analytical Jacobian of the constraints was effective at reducing the number of function evaluations to reach convergence.

Path Planning and Tracking Control of Tracked Agricultural Machinery Based on Improved A* and Fuzzy Control

“…This path may not necessarily conform to the kinematic principles of the agricultural machinery. Therefore, parametric curves such as Dubins curves [31] and clothoids [32] are used in path planning, as they require less computation. On the other hand, these curves are not practical because they cannot generate closed paths [33].…”

Interaction between a Human and an AGV System in a Shared Workspace—A Literature Review Identifying Research Areas

“…The critical aspect is the navigation system, which allows the AGV to smoothly move along the designated route. For this purpose, appropriate programs, algorithms, and systems are created, responsible for the correct movement of AGVs along fixed routes [108,[113][114][115][116][117][118][119][120][121][122][123][124]. Regarding navigation, it is also crucial that the AGV continues the task in the event of a disturbance (e.g., an obstacle).…”

Smooth Three-Dimensional Route Planning for Fixed-Wing Unmanned Aerial Vehicles With Double Continuous Curvature

“…In [29], [30], clothoids are approximated using Bézier curves to minimize curvature profiles and thus guarantee higher-order geometric continuity while minimizing error. In [31], smooth paths based on clothoid curves are proposed for planning highspeed wheeled vehicle paths, for which a numerical optimization is performed within the constraints of convex regions. In [32], autonomous valet parking service path planning is performed.…”