Nested Field-of-View Barriers for Teleoperated Multi-Robot Relay Chains
Authors: Arthur Vangasse, Theo Cruz, Thales Soares, André Cid, Vinícius Gonçalves, Gustavo Freitas, Luciano Pimenta
Organizations: The authors are with the Graduate Program in Electrical Engineering, Federal University of Minas Gerais, Belo Horizonte, Brazil · The authors are with the School of Engineering, Federal University of Minas Gerais, Belo Horizonte, Brazil
Teleoperation of mobile robots in communication-denied environments requires maintaining a communication link while allowing the operator to maneuver freely. We propose a shared-autonomy framework in which a teleoperated leader is followed by a chain of autonomous robots that relays a line of sight to a fixed base station, a geometric proxy for the link. Connectivity is enforced geometrically through visibility-based Control Barrier Functions (CBFs), with each agent computing its control input locally through a quadratic program. A strict visibility constraint guarantees connectivity, but a follower with no independent motion objective remains stationary, stalling the leader at the boundary of the safe set. Relaxing it preserves mobility at the cost of the guarantee. Our framework resolves this conflict through nested hard-soft visibility constraints: a full field-of-view (FoV) constraint enforced strictly to guarantee connectivity and a contracted FoV constraint imposed on each follower as a relaxed behavioral objective that drives it inward before the connectivity boundary is reached. We prove feasibility of the local quadratic programs and forward invariance of the connected, collision-free set under the resulting distributed controller. The contraction parameter shapes follower behavior without affecting the guarantee, which follows from the strict constraint alone. The framework is evaluated in confined and cluttered environments on two simulated systems: a kinematic integrator and software-in-the-loop Crazyflie quadrotors. Compared with a baseline tuned to reach the goal in comparable time, the framework keeps the links far closer to the connected set and moves the followers less.
Figures & tables
Fig. 1 : The nested field-of-view framework. A teleoperated leader, a chain of relays each holding its predecessor inside a field of view F that obstacles cut, and a fixed base.
Fig. 2 : A step δ pivots the shadow edge about the corner, sweeping it by (H/c)δ .
Fig. 3 : Nested at the instant the leader reaches the goal, with the waypoints marked ⋄ and the goal ⊗ , each observer’s occluded field of view, and the segment to its nearest obstacle.
Tunnel
Clutter
Strict
Relaxed
Nested
Strict
Relaxed
Nested
hmin [m]
0.000/−0.127
−0.228/−0.201
0.001/−0.070
−0.003/−0.073
−0.397/−0.404
−0.018/−0.078
Vh [m s]
0.000/0.618
0.366/0.209
0.000/0.071
0.001/0.676
2.277/2.014
0.017/0.159
ΔT [s]
–
13.2±0.3/11.9±1.4
12.1±0.3/11.7±1.0
–
10.2±0.5/14.4±2.6
10.2±0.8/10.0±2.0
Ef [m]
0.00/0.41±0.12
7.42±0.15/7.87±0.35
5.95±0.08/5.64±0.20
0.00/0.25±0.08
8.04±0.20/11.68±0.41
5.99±0.18/5.99±0.48
J [m]
0.036/0.113
0.110/0.127
0.110/0.111
0.052/0.107
0.061/0.213
0.089/0.117
TABLE I : Both workspaces, 10 runs per cell, every entry kinematic / SIL. hmin , Vh and J are the worst value over the ten runs, ΔT and Ef their mean and standard deviation.
We investigate the mutual visibility problem for a swarm of n≥3 autonomous mobile robots under the budget-constrained mobility fault model. The robots are opaque, so if three robots are collinear, the middle robot obstructs the visibility between the other two. Each robot is assigned a finite movement budget, reflecting its limited energy, that bounds the total distance it may traverse during the execution. Moreover, an arbitrary number of robots may become permanently immobile due to mobility faults. The objective is to design a distributed algorithm that enables the non-faulty robots to coordinate their movements so that, within a finite time, every non-faulty robot attains unobstructed visibility of all robots in the system, including the faulty ones, while respecting the prescribed movement budget. We consider luminous robots operating under the SSYNC model with non-rigid movements, without any agreement on their local coordinate systems, and equipped only with a {\it common fixed reference point}. We present a deterministic distributed algorithm that solves the problem despite an arbitrary number of mobility faults. The algorithm guarantees mutual visibility for the non-faulty robots, respects the movement budget of every robot, provides collision-free movements for the robots, and uses only 12 light colors.
Prakhar Shukla, Animesh Maiti, Shivam Kumar +1
Department of Mathematics Indian Institute of Technology Jodhpur Jodhpur, Rajasthan, India
Multi-robot systems rely on underlying connectivity to ensure reliable communication and timely coordination. This paper studies the line-of-sight (LoS) connectivity maintenance problem in multi-robot navigation with unknown obstacles. Prior works typically assume known environment maps to formulate LoS constraints between robots, which hinders their practical deployment. To overcome this limitation, we propose an inherently distributed approach where each robot only constructs an egocentric visible region based on its real-time LiDAR scans, instead of endeavoring to build a global map online. The individual visible regions are shared through distributed communication to establish inter-robot LoS constraints, which are then incorporated into a multi-robot navigation framework to ensure LoS-connectivity. Moreover, we enhance the robustness of connectivity maintenance by proposing a more accurate LoS-distance metric, which further enables flexible topology optimization that eliminates redundant and effort-demanding connections. The proposed framework is evaluated through extensive multi-robot navigation and exploration tasks in both simulation and real-world experiments. Results show that it reliably maintains LoS-connectivity between robots in challenging environments cluttered with obstacles, even under large visible ranges and fragile minimal topologies, where existing methods consistently fail. Ablation studies also reveal that topology optimization boosts navigation efficiency by around 20%, demonstrating the framework's potential for efficient navigation under connectivity constraints.
This letter proposes a distributed 3D leader-follower formation (3D-LFF) control framework for multi-UAV systems that achieves formation tracking while enforcing perception safety constraints. Maintaining safe, vision-based 3D-LFF is challenging because onboard cameras impose strict Field-of-View (FOV) limitations, and demanding formation commands can drive the leader outside the follower's camera frustum, resulting in loss of visibility. To address this issue, we develop a perception-aware safe control architecture that guarantees visibility by construction. First, we derive a relative kinematic model in a line-of-sight coordinate representation and design a distributed 3D-LFF tracking controller using only locally available relative states. Next, we embed the nominal formation controller within a Control Barrier Function-based Quadratic Program (CBF-QP) safety filter that minimally modifies the commanded velocities to maintain the leader inside the follower's camera frustum while preserving formation tracking whenever feasible. Gazebo simulations and Crazyflie hardware experiments validate the proposed approach, demonstrating accurate formation tracking and effective FOV enforcement, including scenarios in which the nominal desired formation conflicts with visibility constraints.
Immanuel R. Santjoko, Richie R. Suganda, Miao Pan +1
Department of Electrical and Computer Engineering, University of Houston, Houston, TX 77004, USA · Department of Engineering Technology, University of Houston, Houston, TX 77004, USA