Chain formation control for a platoon of robots using time-gap separation

Abstract

The main objective of this article is to present a controller capable of maintaining a chain formation of platooning type, among a set of non-holonomic mobile robots, keeping a time-gap separation between each pair of consecutive robots at the platoon. It is intended that the whole set of robots asymptotically follows any feasible trajectory described by the leader robot. Under these conditions, the distance between any pair of consecutive robots, that is, the i-th robot and the ði þ 1Þ-th robot, depends on the velocity of the i-th robot. Only position measurements are available, such that, to avoid using approximate velocity estimations, the chain formation problem is solved by considering a delay observer strategy. Based on the measurements of the positions of the robots, along the platoon, a delay observer is built for the i-th robot that provides a virtual reference for the ði þ 1Þ-th robot, and this reference corresponds to the i-th robot trajectory delayed specific units of time, corresponding to the desired time-gap separation. Convergence of the ði þ 1Þ-th robot to its desired delayed trajectory, which implies convergence of the chain formation, is formally proved by means of a Lyapunov stability approach and supported by numerical simulations and real-time experiments.

Observer-Based Time-Variant Spacing Policy for a Platoon of Non-Holonomic Mobile Robots

“…Notice that in a fixed time-gap strategy reducing the traveling velocity may produce a collision situation, since the inter-vehicle distance also decreases. To avoid such a collision scenario, in this work, a time-varying spacing policy, inversely proportional to the distance between vehicles, is proposed based on the fixed-time spacing policy presented in [24]. It is considered a time-varying gap τ i (t) that increases its magnitude when the distance between vehicles reaches a threshold, which implies that the velocity of the formation is too slow.…”

“…A delay-based spacing policy has been designed in [5] for the control of vehicle platoons considering disturbances and the string stability of the approximated model of the vehicles. Another delay-based spacing policy can be seen in [23,24], where an approach based on an inputdelay observer to obtain a fixed time-gap separation is used for the differential drive of a mobile robot platoon.…”

“…In a time spacing policy, most approaches consider that the velocity of the platoon should not approach zero, since if it is reduced, the vehicle separation will also approach zero and there could be a collision between the vehicles. For this reason, the present paper proposes an extension of the work developed in [23,24] where a fixed time-delay spacing policy is proposed, broadening the work to a time-varying spacing policy inspired by artificial potential fields, which ensures a safe distance between the members of the string, avoiding robots from getting too close to each other. Under these conditions, the work considers a squad of non-holonomic mobile robots, where each robot is intended to follow the position and orientation of its precedent vehicle in the formation, while maintaining a time-varying gap that avoids collisions when the robots approach each other.…”

Platoon Separation Strategy Optimization Method Based on Deep Cognition of a Driver’s Behavior at Signalized Intersections

“…After getting the driving types of the human-driven vehicles, we learn the maximum number of vehicles that can change the lane safely. (6) where Z represents the lane-changing zones and q represents the number of vehicles that can safely move in this zone. If the zone is too short to accept even one vehicle, then q = 0.…”

“…Since the limited green light duration, some vehicles have to cross the intersection in the next green light phase or separate from the platoon and cross the intersection by moving into other lanes. Vehicle separation is one of the most common driving scenarios [4]- [6] for platoon operating in the vicinity of the intersection, which will increase the platoon number and add communication pressure to the infrastructure [7]. The latest statistical data of the National Highway Traffic Safety Administration (NHTSA) indicates that around 40% of all The associate editor coordinating the review of this manuscript and approving it for publication was Maurice J. Khabbaz .…”