REVIEW 3 major objections 4 minor 37 references
Dynamical Vehicle Orienteering Problem for Multi-Rotor Unmanned Aerial Vehicles
T0 review · 3 major / 4 minor · reviewed 2026-08-02 · deepseek-v4-flash
Pith's one-line read A new drone-routing problem that respects acceleration and gravity can be solved exactly by branch-and-bound, with a fast heuristic that stays within 18% of optimal and beats prior methods by up to 37%.
desk verdict A solid new problem formulation and heuristic with a clever MILP bound, but the 'exact BnB' label doesn't survive contact with IPOPT's local solutions and the n_sub=5 cap. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The load-bearing mechanism is the MILP relaxation of the vehicle dynamics, built from time-optimal trajectory primitives through target triplets (eq. 32). A primitive is the minimum flight time from one target to another while passing through a third, computed offline by solving a small NLP; these precomputed costs become coefficients of binary decision variables in the MILP. Because three targets are the minimum that forces a velocity change, triplet primitives encode the acceleration constraint (2b) that a graph with pairwise distances would miss. The MILP cost function $\hat{C}(X)$ is a valid lower bound on the true relaxed travel cost—each consecutive-target edge cost is taken as an averag
What would settle it
Take any DVOP instance and compare the primitive costs $C_{NLP}(q_A,q_B,q_C)$ from eq. (51) against a certified global solution—for example, a dense grid over switch times and axis-wise bang-bang structures, or a rigorous global NLP solver. If even one primitive cost exceeds the certified global minimum, the BnB's upper bound is invalid for that instance. A simpler empirical test: run the authors' implementation with the number of switches raised to 6, 8, and 10, and check whether any best-known solution's reward increases; if it does, the fixed cap of five switches was cutting off time-optimal traje
Extended reading notes
Core claim
The central claim is that the DVOP—maximise reward collected by a point-mass quadrotor under velocity, acceleration and gravity constraints within a flight-time budget—can be solved exactly by a branch-and-bound procedure whose upper bounds are computed by a novel MILP relaxation. The relaxation represents travel cost through triples of targets using precomputed time-optimal trajectory primitives, so the acceleration constraint enters the combinatorial model through the primitive costs rather than through edge distances. The paper shows experimentally that the MILP upper bound is tight (mean reward gap under 8% over all valid solution-tree nodes in the evaluated scenarios) and that the BnB c
Load-bearing premise
The branch-and-bound's claim to exactness rests on the nonlinear trajectory optimisations (eqs. 48–51) being solved to global optimality, but they are solved with a local NLP solver and the control parameterisation is capped at five input switches; if a true time-optimal trajectory needs more switches or the solver stops at a local minimum, the planned travel times are overestimated, the remaining budget is understated, and the BnB can prune the optimal sequence.
Editorial extensions
If this is right
- If correct, the BnB returns the globally optimal visit sequence on instances it can terminate, giving a reference standard for the DVOP and for the Kinematic Orienteering Problem under magnitude constraints.
- The LNS heuristic yields near-optimal solutions within seconds and therefore a practical anytime planner for larger instances, where the exact method requires hours.
- The MILP relaxation based on trajectory primitives can be transferred to other second-order vehicle routing settings, replacing pairwise graph costs wherever acceleration matters.
- The reported 37% improvement over prior KOP solutions indicates that modelling full thrust and gravity changes which targets a drone can visit, not just the path between them.
- The real-world flight tests show the planned point-mass trajectories are trackable within about 0.3 m horizontally, so the improved plans are executable, not just theoretical.
Reading between the lines
- A natural extension would be to replace the local NLP solves with a certified global solver (or a fine grid of switch times) to remove the gap between 'claimed exact' and 'numerically global'—the authors do not prove the NLP subproblems reach the true global minimum.
- The LNS's removal of velocity sampling suggests a cheap improvement for other Dubins-style orienteering solvers: maintain continuous heading/speed optimisation at targets instead of discretising them.
- The gap between LNS and BnB (up to 17.3%) could be closed online by using the MILP bound as a certificate: run LNS, compute the bound for its sequence, and only degrade to speculation when the bound is loose.
- The triplet-primitive idea might scale to higher-order dynamics or to multi-vehicle versions, though the precomputation cost grows cubically with the number of targets.
Signed reviews
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper introduces the Dynamical Vehicle Orienteering Problem (DVOP), a generalization of the Orienteering Problem in which travel costs are minimum-time trajectories of a three-dimensional point-mass model with velocity and acceleration magnitude constraints under gravity. The authors propose two solvers: an LNS metaheuristic that optimizes target order and entry velocities via limited-thrust-decomposition trajectory planning, and a Branch-and-Bound (BnB) procedure that combines NLP trajectory optimization with a MILP relaxation based on trajectory primitives through target triplets. The BnB is claimed to be exact, returning the globally optimal DVOP target sequence. The paper reports KOP benchmark improvements up to 37% over prior work, evaluates the LNS/BnB gap on randomized 3D instances, and validates the planned trajectories on a real multirotor UAV.
Significance. The DVOP is a natural and useful extension of the KOP/OP family, and the proposed two-level solution architecture is sensible. If the exactness of the BnB could be certified, the paper would be a substantial methodological contribution to the orienteering/VRP literature, since it couples combinatorial selection with continuous time-optimal control. The heuristic LNS with LTD-based insertion and refinement appears credible and is supported by reproducible experiments, a public code repository, and real-flight validation. The MILP primitive-based bounding idea is novel, but its validity as a rigorous reward upper bound is not established. The reported KOP improvements and the real-world tracking demonstration are valuable independent of the exactness claim.
major comments (3)
- [Sec. 5.2, Alg. 4 and Sec. 5.4, eqs. (48)-(51)] The central claim 'We propose an exact Branch-and-Bound (BnB) procedure' is not supported. The optimality certificate depends on solving eq. (4) and its relaxations (22), (24) exactly, but Sec. 5.4 states that C_NLP is 'locally optimal', is solved with IPOPT, and that n_sub is set to 5 empirically because 'increasing the switches beyond 5 did not improve quality'. If IPOPT returns a local minimum, or if the true time-optimal trajectory needs more than five input switches per pair, then C_NLP(S) and C_NLP_rel(S) overestimate the true minimal travel times. Eq. (21) then underestimates the remaining budget, and the MILP constraint (37) can exclude rewards still reachable, so Alg. 4 can prune the globally optimal sequence. Consequently, the LNS-BnB gaps in Table 3 are not certified distances to the true optimum. This needs either a global-optimality certificate for the NLPs on the tested ins
- [Sec. 5.3, eq. (35)] The assertion that the averaged primitive cost C_hat(X) is a valid lower bound on C_hat_rel is not proved. The text says the cost is valid 'as the travel cost incurred for each consecutive pair of targets in S_hat is bounded by an average value of two elements of C, which themselves are lower-bounds on time-optimal travel costs.' Averaging lower bounds does not in general produce a lower bound on the quantity being relaxed; the 1/2 factor and the overlapping triplet primitives require a formal inequality proof. If C_hat(X) ever exceeds the true C_hat_rel(S_hat), the reward upper bound in eqs. (36)-(37) is invalid and the BnB can prune the optimum even when the trajectory NLPs are solved exactly. Please provide a rigorous derivation or a concrete counterexample.
- [Sec. 5.4, eq. (47)] Even if the NLPs were solved to global optimality, the discrete model (47) with at most n_sub input-switching steps per target pair is a restricted trajectory family. The paper itself notes that the velocity bound (2a) can produce singular arcs requiring infinitely many input switches, yet n_sub=5 is chosen empirically. No theorem is given showing that five switches per pair is sufficient for the full 3D model with magnitude constraints and target sequences. Therefore the computed C_NLP and its relaxations are not necessarily the exact continuous-time costs C(S) of eq. (4). The exactness claim requires a representation theorem for the trajectory model, not an empirical cap.
minor comments (4)
- [Sec. 7 vs Sec. 6.5, Table 5] The conclusion states a '3D RMS tracking error below 0.5 m' during agile flight at 21 m/s, but Table 5 reports RMSE = 0.671 m at that speed. The number or the wording should be corrected.
- [Sec. 1 and Sec. 5] The paper calls the BnB 'exact' in the introduction while Sec. 5 says C_NLP is 'locally optimal' and that 'no exact time-optimal point-mass planner exists'. This terminological contradiction should be resolved.
- [Sec. 5.3, eq. (35)] The indexing in eq. (35) is difficult to follow: the ranges of j and k, the meaning of x_{i,j,k}, and the factor 1/2 deserve a clearer derivation or a small worked example.
- [Sec. 6.2, Table 3] Many rows at high Tmax report reward equal to the total available reward (15.00) with PDB=0.0, indicating instance saturation. This should be stated explicitly when discussing the PDB trend.
Circularity Check
No significant circularity: the MILP reward upper bound and BnB pruning logic are self-contained; the exactness claim is weakened by IPOPT-local and empirical n_sub=5 assumptions, which is a soundness risk rather than a circular derivation.
full rationale
The derivation chain is not circular in the sense defined here. The DVOP cost C(S) is introduced as a continuous-time minimum over trajectories in eq. (4), and the BnB upper bound is built from two relaxations, C_rel(S) in eq. (22) and C_hat_rel(S_hat) in eq. (24), with the monotonicity inequalities (23), (25), and (26) establishing that the relaxed costs lower-bound the true costs. The MILP cost C_hat(X) is then constructed independently from lower-bound trajectory primitive costs in eqs. (32)-(34), so the reward upper bound (27)-(30) is a genuine relaxation and not a fitted quantity renamed as a prediction. The LNS supplies a feasible lower bound, not a fitted input to the claimed upper-bound result. There is substantial reuse of prior work by the same research group—notably Teissing et al. (2024) for LTD trajectories and Nekovář et al. (2023) for KOP-NLP formulations—but these are published building blocks and are not invoked as an author-specific uniqueness theorem or ansatz; the central MILP-bound argument does not reduce to a self-citation. The most serious caveat in the paper is not circularity but soundness: Sec. 5 states that 'no exact time-optimal point-mass planner exists', eq. (48) is solved with IPOPT to obtain 'locally optimal' C(S), and Sec. 5.4 admits 'increasing the switches beyond 5 did not improve quality, so we set n_sub=5 empirically'. If IPOPT returns local minima, or the true time-optimal trajectory needs more than five switches, the cost lower bounds can be violated and the BnB may prune an optimal sequence. That is an unproven correctness assumption, not an equivalence-by-construction between input and output, so it does not raise the circularity score beyond the low range; I assign 2 only for the notable same-author citation reuse while recognizing that the central claim has independent content.
Assumptions & free parameters
free parameters (2)
- n_sub (input-switching sub-steps) =
5
- LNS/refinement hyperparameters =
N_iter=200, N_keep=20, eta=2/3, rho start 0.1 step 0.1 max 0.8
assumptions (6)
- domain assumption The point-mass model (1)-(2), with velocity bound ||v||<=Vmax and thrust bound ||a-g||<=Amax, adequately describes multi-rotor flight for route planning.
- standard math One-dimensional minimum-time point-mass trajectories are bang-zero-bang (accelerate, cruise, decelerate), so eq. (6) covers all optimal single-axis motion.
- domain assumption Synchronizing per-axis bang-zero-bang segments with Limited Thrust Decomposition gives a deterministic near-optimal 3D trajectory and a valid upper bound C_tilde(S) >= C(S).
- ad hoc to paper At most n_sub=5 input-switching sub-steps are sufficient for time-optimal point-mass trajectories through multiple targets.
- ad hoc to paper IPOPT solutions of the nonconvex NLPs (48)-(51) are global minima, so C_NLP, C_NLP_rel, C_hat_NLP_rel and c_NLP equal the true optimal travel costs.
- ad hoc to paper The averaged primitive cost C_hat(X) in eq. (35) is a valid lower bound on the start-relaxed cost C_hat_rel.
Cite this review
Pith. "Pith review of Dynamical Vehicle Orienteering Problem for Multi-Rotor Unmanned Aerial Vehicles." pith.science (2026). https://pith.science/paper/NYO7YQC5
@misc{pith2026260713789,
author = {Pith},
title = {Pith review of: Dynamical Vehicle Orienteering Problem for Multi-Rotor Unmanned Aerial Vehicles},
year = {2026},
howpublished = {\url{https://pith.science/paper/NYO7YQC5}},
note = {Machine review of arXiv:2607.13789}
}
read the original abstract
This paper introduces the Dynamical Vehicle Orienteering Problem (DVOP), a generalization of the Orienteering Problem (OP). The OP maximizes the reward collected from spatial targets under a limited travel budget; the DVOP extends it by accounting for both external and vehicle-actuated forces. We study the DVOP in the context of multi-rotor Unmanned Aerial Vehicle (UAV) flight planning, using a three-dimensional Point-Mass Model (PMM) constrained by maximum velocity and acceleration magnitudes and subject to gravitational acceleration, with the travel budget expressed as a maximum flight time. Because the DVOP couples reward maximization with time-optimal trajectory planning, it cannot be formulated as a simple graph problem and solved exactly without relaxing or under-actuating the vehicle dynamics. We therefore propose two solution approaches: a Branch-and-Bound (BnB) procedure that combines Non-Linear Programming (NLP) and Mixed-Integer Linear Programming (MILP) to provide high-quality solutions, and a Large Neighborhood Search (LNS) metaheuristic that supplies an initial reward bound and scales to instances intractable for the BnB. The BnB relies on a novel MILP formulation of travel costs based on minimum-time trajectory primitives through target triplets, yielding a tight reward upper bound, while the LNS uses limited thrust decomposition to compute fast, high-quality PMM trajectories. Experiments on benchmark instances show improvements of up to 37 % over state-of-the-art solutions for the Kinematic Orienteering Problem, and a real-world deployment on a multi-rotor UAV verifies the proposed PMM solution trajectories.
Figures
Figures from the paper (7 more)
Reference graph
Works this paper leans on
- [6]
-
[9]
Alphapilot: autonomous drone racing. Autonomous Robots 46, 307–320. doi:10.1007/s10514-021-10011-y. Ghotavadekar, A., Nekovář, F., Saska, M., Faigl, J.,
-
[11]
European journal of operational research 255, 315–332
Orienteering problem: A survey of recent variants, solution approaches and applications. European journal of operational research 255, 315–332. doi:10.1016/j.ejor.2016.04.059. Gurobi Optimization, LLC,
-
[16]
IEEE Robotics and Automation Letters 7, 11402–11409
Kinematic orienteering problem with time-optimal trajectories for multirotor uavs. IEEE Robotics and Automation Letters 7, 11402–11409. doi:10.1109/LRA.2022.3194688. Meyer, F., Glock, K., Sayah, D.,
arXiv 2022
-
[17]
Top-uav: Open-source time-optimal trajectory planner for point-masses under acceleration and velocity constraints, in: 2023 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), IEEE. pp. 2838–2845. doi:10.1109/IROS55552.2023.10342270. Mladenović, N., Hansen, P.,
arXiv 2023
-
[18]
Annals of Operations Research 314, 255–275
Vehicle routing problems over time: a survey. Annals of Operations Research 314, 255–275. doi:10.1007/s10479-021-04488-0. Morandi, N., Leus, R., Yaman, H.,
-
[19]
Transportation Science 58, 240–256
The orienteering problem with drones. Transportation Science 58, 240–256. doi:10.1287/ trsc.2023.0003. Nekovář, F., Faigl, J., Saska, M.,
arXiv 2023
-
[20]
IEEE Robotics and Automation Letters 8, 6323–6330
Multi-vehicle dynamic water surface monitoring. IEEE Robotics and Automation Letters 8, 6323–6330. doi:10.1109/LRA.2023.3304533. Pěnička, R., Faigl, J., Saska, M.,
arXiv 2023
Show all 37 references
-
[22]
IEEERoboticsandAutomationLetters2, 1210–1217
Dubinsorienteeringproblem. IEEERoboticsandAutomationLetters2, 1210–1217. doi:10.1109/LRA.2017.2666261. Peyman, M., Martin, X.A., Panadero, J., Juan, A.A.,
2017
-
[24]
Springer, Cham
Large Neighborhood Search. Springer, Cham. International Series in Operations Research & Management Science, pp. 99–127. doi:10.1007/978-3-319-91086-4_4. Psaraftis, H.N.,
-
[26]
Romero, A., Penicka, R., Scaramuzza, D.,
Time-optimal planning for long-range quadrotor flights: An automatic optimal synthesis approach.arXiv:2407.17944. Romero, A., Penicka, R., Scaramuzza, D.,
-
[27]
IEEE Robotics and Automation Letters 7, 7730–7737
Time-optimal online replanning for agile quadrotor flight. IEEE Robotics and Automation Letters 7, 7730–7737. doi:10.1109/LRA.2022.3185772. Shaw, P.,
2022
-
[30]
EURO Journal on Transportation and Logistics 11, 100070
A branch-and-price algorithm for a team orienteering problem with fixed-wing drones. EURO Journal on Transportation and Logistics 11, 100070. doi:10.1016/j.ejtl.2021.100070. Teissing, K., Novosad, M., Penicka, R., Saska, M.,
2021
-
[31]
IEEE Robotics and Automation Letters 9, 10351–10358
Real-time planning of minimum-time trajectories for agile uav flight. IEEE Robotics and Automation Letters 9, 10351–10358. doi:10.1109/LRA.2024.3471388. Tsiligirides, T.,
2024
-
[34]
Variable-speed dubins orienteering problem, in: 2024 Latin American Robotics Symposium (LARS), pp. 1–6. doi:10.1109/LARS64411.2024.10786481. Váňa, P., Faigl, J., Sláma, J., Pěnička, R.,
2024
-
[35]
Data collection planning with dubins airplane model and limited travel budget, in: 2017 European Conference on Mobile Robots (ECMR), pp. 1–6. doi:10.1109/ECMR.2017.8098715. Wächter, A., Biegler, L.T.,
2017
-
[37]
Route planning for teams of unmanned aerial vehicles using dubins vehicle model with budget constraint, in: Modelling and Simulation for Autonomous Systems, Springer International Publishing, Cham. pp. 365–389. doi:10.1007/978-3-030-14984-0_27. 28
- [200]
-
[1956]
Operations research 4, 61–75
The traveling-salesman problem. Operations research 4, 61–75. doi:10.1287/opre.4.1.61. Foehn, P., Brescianini, D., Kaufmann, E., Cieslewski, T., Gehrig, M., Muglikar, M., Scaramuzza, D.,
-
[1957]
American Journal of Mathematics 79, 497–516
On curves of minimal length with a constraint on average curvature, and with prescribed initial and terminal positions and tangents. American Journal of Mathematics 79, 497–516. doi:10.2307/2372560. Faigl, J.,
-
[1960]
Econometrica 28, 497–520
An automatic method of solving discrete programming problems. Econometrica 28, 497–520. doi:10.2307/1910129. Meyer, F., Glock, K.,
-
[1984]
The Journal of the Operational Research Society 35, 797–809
Heuristic methods applied to orienteering. The Journal of the Operational Research Society 35, 797–809. 27 doi:10.2307/2582629. Vansteenwegen, P., Souffriau, W., Oudheusden, D.V.,
-
[1988]
Vehicle routing: Methods and studies 16, 223–248
Dynamic vehicle routing problems. Vehicle routing: Methods and studies 16, 223–248. Pěnička,R.,Faigl,J.,Váňa,P.,Saska,M.,2017. Dubinsorienteeringproblemwithneighborhoods,in: 2017InternationalConference on Unmanned Aircraft Systems (ICUAS), pp. 1555–1562. doi:10.1109/ICUAS.2017...
2017
-
[1996]
European Journal of Operational Research 88, 475–489
A fast and effective heuristic for the orienteering problem. European Journal of Operational Research 88, 475–489. doi:10.1016/0377-2217(95)00035-6. Dasdemir, E., Batta, R., Köksalan, M., Öztürk, D.T.,
-
[1998]
Using constraint programming and local search methods to solve vehicle routing problems, in: International conference on principles and practice of constraint programming, Springer. pp. 417–431. doi:10.1007/3-540-49481-2_30. Souffriau, W., Vansteenwegen, P., Vanden Berghe, G.,...
-
[2001]
3rd ed., Springer Berlin, Heidelberg
Self-Organizing Maps. 3rd ed., Springer Berlin, Heidelberg. doi:10.1007/978-3-642-56927-2. Kolesar, P.J.,
-
[2006]
Mathematical programming 106, 25–57
On the implementation of an interior-point filter line-search algorithm for large-scale nonlinear programming. Mathematical programming 106, 25–57. doi:10.1007/s10107-004-0559-y. Zahrádka, D., Pěnička, R., Saska, M.,
-
[2008]
A greedy randomised adaptive search procedure for the team orienteering problem, in: EU/MEeting 2008 on metaheuristics for logistics and vehicle routing, pp. 23–24. Sundar, K., Sanjeevi, S., Montez, C.,
2008
-
[2011]
European Journal of Operational Research 209, 1–10
The orienteering problem: A survey. European Journal of Operational Research 209, 1–10. doi:10.1016/j.ejor.2010.03.045. Vinícius Faria, L.C., Caio Ribeiro, C.G., Macharet, D.G.,
2010 doi
-
[2012]
Autonomous Robots 33, 69–88
Performance benchmarking of quadrotor systems using time-optimal control. Autonomous Robots 33, 69–88. doi:10.1007/s10514-012-9282-3. 26 Hert, D., Baca, T., Petracek, P., Kratky, V., Penicka, R., Spurny, V., Petrlik, M., Vrba, M., Zaitlik, D., Stoudek, P., Walter, V., Stepan, ...
-
[2016]
001315–001321
Self-organizing map-based solution for the orienteering problem with neighborhoods, in: 2016 IEEE International Conference on Systems, Man, and Cybernetics (SMC), pp. 001315–001321. doi:10.1109/SMC.2016. 7844421. Faigl,J.,Váňa,P.,Pěnička,R.,2019.Multi-vehiclecloseenoughoriente...
2016
-
[2017]
Self-organizing map for orienteering problem with dubins vehicle, in: 2017 12th International Workshop on Self-Organizing Maps and Learning Vector Quantization, Clustering and Data Visualization (WSOM), pp. 1–8. doi:10.1109/ WSOM.2017.8020017. Faigl, J., Pěnička, R.,
2017
-
[2019]
European Journal of Operational Research 276, 816–825
Variable neighborhood search for the set orienteering problem and its application to other orienteering problem variants. European Journal of Operational Research 276, 816–825. doi:10.1016/j.ejor.2019.01.047. Pěnička, R., Faigl, J., Váňa, P., Saska, M.,
2019 doi
-
[2021]
Journal of Intelligent & Robotic Systems 102, 1–28
The MRS UAV System: Pushing the Frontiers of Reproducible Research, Real-world Deployment, and Education with Autonomous Unmanned Aerial Vehicles. Journal of Intelligent & Robotic Systems 102, 1–28. doi:10.1007/s10846-021-01383-5. Boussier, S., Feillet, D., Gendreau, M.,
-
[2022]
Computers & Operations Research 145, 105882
Uav routing for reconnaissance mission: A multi-objective orienteering problem with time-dependent prizes and multiple connections. Computers & Operations Research 145, 105882. doi:10.1016/j.cor.2022.105882. Dubins, L.E.,
2022
-
[2023]
Journal of Intelligent & Robotic Systems 108, 1–34
MRS Drone: A Modular Platform for Real-World Deployment of Aerial Multi-Robot Systems. Journal of Intelligent & Robotic Systems 108, 1–34. doi:10.1007/s10846-023-01879-2. HSL,
-
[2024]
IEEE Robotics and Automation Letters doi:10.1109/LRA.2024.3518096
Variable time-step mpc for agile multi-rotor uav interception of dynamic targets. IEEE Robotics and Automation Letters doi:10.1109/LRA.2024.3518096. Golden, B.L., Levy, L., Vohra, R.,
2024
Reviewed August 2, 2026 · model on record in the stance chip above.
Discussion (0). Continue with ORCID to comment.