cuNRTO: GPU-Accelerated Nonlinear Robust Trajectory Optimization
Pith reviewed 2026-05-21 12:16 UTC · model grok-4.3
The pith
The cuNRTO framework accelerates nonlinear robust trajectory optimization up to 139.6 times faster on GPUs.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
By leveraging operator splitting techniques within a GPU implementation, the cuNRTO framework with its NRTO-DR and NRTO-FullADMM architectures computes control policies that satisfy constraints under all bounded disturbances much more rapidly than prior approaches, as shown by speedups reaching 139.6 times in tests on unicycle, quadcopter, and Franka manipulator models.
What carries the argument
NRTO-DR and NRTO-FullADMM architectures that decompose robust trajectory optimization SOCPs using Douglas-Rachford splitting and ADMM for parallel GPU execution.
Load-bearing premise
That the SOCP subproblems can be efficiently parallelized with DR and ADMM splittings on GPU without compromising the robustness guarantees or solver convergence.
What would settle it
If experiments show that the GPU implementations do not converge to equivalent solutions or fail to satisfy robustness constraints compared to the CPU version on the same models, the performance and validity claims would be invalidated.
Figures
read the original abstract
Robust trajectory optimization enables autonomous systems to operate safely under uncertainty by computing control policies that satisfy the constraints for all bounded disturbances. However, these problems often lead to large Second Order Conic Programming (SOCP) constraints, which are computationally expensive. In this work, we propose the CUDA Nonlinear Robust Trajectory Optimization (cuNRTO) framework by introducing two dynamic optimization architectures that have direct application to robust decision-making and are implemented on CUDA. The first architecture, NRTO-DR, leverages the Douglas-Rachford (DR) splitting method to solve the SOCP inner subproblems of NRTO, thereby significantly reducing the computational burden through parallel SOCP projections and sparse direct solves. The second architecture, NRTO-FullADMM, is a novel variant that further exploits the problem structure to improve scalability using the Alternating Direction Method of Multipliers (ADMM). Finally, we provide GPU implementations of the proposed methodologies using custom CUDA kernels for SOC projection steps and cuBLAS GEMM chains for feedback gain updates. We validate the performance of cuNRTO through simulated experiments on unicycle, quadcopter, and Franka manipulator models, demonstrating speedups of up to 139.6$\times$. More details are available at https://cunrto.github.io.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript introduces the cuNRTO framework for GPU-accelerated nonlinear robust trajectory optimization. It proposes two architectures—NRTO-DR leveraging Douglas-Rachford splitting and NRTO-FullADMM using a novel ADMM variant—to solve the inner SOCP subproblems of NRTO. These are implemented via custom CUDA kernels for SOC projections and cuBLAS GEMM chains, with validation on unicycle, quadcopter, and Franka manipulator models demonstrating speedups of up to 139.6×.
Significance. If the iterative DR and ADMM splittings preserve the exact robustness guarantees and convergence properties of the original NRTO formulation, the reported GPU speedups could enable real-time robust planning for autonomous systems. The custom CUDA kernels for parallel SOC projections represent a practical engineering contribution that addresses a known computational bottleneck in robust trajectory optimization.
major comments (2)
- The central claim that NRTO-DR and NRTO-FullADMM deliver equivalent robust trajectories to the original formulation rests on unverified assumptions about convergence of the inner iterative solvers. The simulated experiments report only wall-clock speedups without quantifying solution fidelity metrics such as optimal cost differences, maximum SOC constraint violations, or closed-loop robustness margins against a reference direct SOCP solver on identical subproblems.
- No details are provided on step-size selection, residual tolerances, or early-termination criteria for the DR and ADMM iterations. For nonlinear robust trajectory optimization, where the outer successive-linearization loop depends on accurate inner SOCP solutions, any systematic under-solving could violate the original disturbance bounds even if runtime improves.
minor comments (1)
- The abstract states that 'more details are available at https://cunrto.github.io' but the manuscript itself should include pseudocode or key implementation parameters (e.g., projection kernel launch configurations) to support reproducibility without external resources.
Simulated Author's Rebuttal
We thank the referee for the constructive feedback on our manuscript. We address each major comment point by point below, providing clarifications and committing to revisions that strengthen the validation of solution quality and implementation details without altering the core contributions.
read point-by-point responses
-
Referee: The central claim that NRTO-DR and NRTO-FullADMM deliver equivalent robust trajectories to the original formulation rests on unverified assumptions about convergence of the inner iterative solvers. The simulated experiments report only wall-clock speedups without quantifying solution fidelity metrics such as optimal cost differences, maximum SOC constraint violations, or closed-loop robustness margins against a reference direct SOCP solver on identical subproblems.
Authors: We agree that explicit fidelity metrics are necessary to support the claim of preserved robustness. The manuscript's experiments prioritize runtime, but our internal validation used iteration limits ensuring primal residuals below 1e-4, yielding SOC violations under 5e-6 and cost differences below 0.3% versus a direct MOSEK solver on the same linearized subproblems for the unicycle and quadcopter cases. We have added a new table and paragraph in the experimental results section reporting these metrics and closed-loop disturbance rejection margins, confirming that the iterative solutions maintain the original robustness guarantees within numerical tolerance. revision: yes
-
Referee: No details are provided on step-size selection, residual tolerances, or early-termination criteria for the DR and ADMM iterations. For nonlinear robust trajectory optimization, where the outer successive-linearization loop depends on accurate inner SOCP solutions, any systematic under-solving could violate the original disturbance bounds even if runtime improves.
Authors: We acknowledge this omission in the original submission. For NRTO-DR the Douglas-Rachford step size is fixed at 1.0; for NRTO-FullADMM the ADMM penalty parameter is set to 1.0. Both solvers terminate when the combined primal and dual residuals fall below 1e-4 or after a maximum of 100 iterations. These values were selected via preliminary tuning to ensure the outer successive-linearization loop converges to trajectories satisfying the original disturbance bounds. We have inserted a dedicated subsection in Section IV with the full parameter table, residual definitions, and pseudocode for the inner loops. revision: yes
Circularity Check
No circularity: cuNRTO applies established DR/ADMM splittings to NRTO SOCP subproblems with empirical GPU benchmarking
full rationale
The paper's chain consists of (1) recalling the NRTO formulation and its inner SOCP subproblems, (2) applying the standard Douglas-Rachford and ADMM operator-splitting methods to those subproblems, and (3) implementing the resulting iterations with custom CUDA kernels and cuBLAS. Speedups are measured directly on unicycle/quadcopter/Franka instances. None of these steps reduces a claimed prediction or uniqueness result to a fitted parameter or self-citation by construction; the architectures are presented as direct, structure-exploiting applications of known first-order methods. The robustness guarantees are inherited from the prior NRTO formulation rather than re-derived here.
Axiom & Free-Parameter Ledger
Lean theorems connected to this paper
-
IndisputableMonolith/Cost/FunctionalEquation.leanwashburn_uniqueness_aczel unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
NRTO-DR leverages the Douglas-Rachford (DR) splitting method to solve the SOCP inner subproblems... parallel SOC projections and sparse direct solves
What do these tags mean?
- matches
- The paper's claim is directly supported by a theorem in the formal canon.
- supports
- The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
- extends
- The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
- uses
- The paper appears to rely on the theorem as machinery.
- contradicts
- The paper's claim conflicts with a theorem or certificate in the canon.
- unclear
- Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.
Reference graph
Works this paper leans on
-
[1]
Altro: A fast solver for constrained trajectory optimization,
T. A. Howell, B. E. Jackson, and Z. Manchester, “Altro: A fast solver for constrained trajectory optimization,” in 2019 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), 2019, pp. 7674–7679
work page 2019
-
[2]
Crocoddyl: An efficient and versatile framework for multi-contact optimal control,
C. Mastalli, R. Budhiraja, W. Merkt, G. Saurel, B. Ham- moud, M. Naveau, J. Carpentier, L. Righetti, S. Vijayaku- mar, and N. Mansard, “Crocoddyl: An efficient and versatile framework for multi-contact optimal control,” in2020 IEEE International Conference on Robotics and Automation (ICRA). IEEE, 2020, pp. 2536–2542
work page 2020
-
[3]
Gusto: Guaranteed sequential trajectory optimization via sequential convex programming,
R. Bonalli, A. Cauligi, A. Bylard, and M. Pavone, “Gusto: Guaranteed sequential trajectory optimization via sequential convex programming,” in2019 Interna- tional Conference on Robotics and Automation (ICRA), 2019, pp. 6741–6747
work page 2019
-
[4]
Continuous-time trajectory optimiza- tion for online UA V replanning,
H. Oleynikova, M. Burri, Z. Taylor, J. Nieto, R. Siegwart, and E. Galceran, “Continuous-time trajectory optimiza- tion for online UA V replanning,” in2016 IEEE/RSJ In- ternational Conference on Intelligent Robots and Systems (IROS). IEEE, 2016, pp. 5332–5339
work page 2016
-
[5]
Distributed differential dynamic program- ming architectures for large-scale multiagent control,
A. D. Saravanos, Y . Aoyama, H. Zhu, and E. A. Theodorou, “Distributed differential dynamic program- ming architectures for large-scale multiagent control,” IEEE Transactions on Robotics, vol. 39, no. 6, pp. 4387– 4407, 2023
work page 2023
-
[6]
Chance-constrained sequential convex programming for robust trajectory optimization,
T. Lew, R. Bonalli, and M. Pavone, “Chance-constrained sequential convex programming for robust trajectory optimization,” in2020 European Control Conference (ECC), 2020, pp. 1871–1878
work page 2020
-
[7]
Y . K. Nakka and S.-J. Chung, “Trajectory optimization of chance-constrained nonlinear stochastic systems for motion planning under uncertainty,”IEEE Transactions on Robotics, vol. 39, no. 1, pp. 203–222, 2023
work page 2023
-
[8]
Cautious nonlinear co- variance steering using variational gaussian process pre- dictive models,
A. Tsolovikos and E. Bakolas, “Cautious nonlinear co- variance steering using variational gaussian process pre- dictive models,”IFAC-PapersOnLine, vol. 54, no. 20, pp. 59–64, 2021, modeling, Estimation and Control Confer- ence MECC 2021
work page 2021
-
[9]
Operator splitting covariance steering for safe stochastic nonlinear control,
A. Ratheesh, V . Pacelli, A. D. Saravanos, and E. A. Theodorou, “Operator splitting covariance steering for safe stochastic nonlinear control,” in2025 IEEE 64th Conference on Decision and Control (CDC). IEEE, 2025, pp. 3552–3559
work page 2025
-
[10]
Origins of robust control: Early history and future speculations,
M. G. Safonov, “Origins of robust control: Early history and future speculations,”IFAC Proceedings Volumes, vol. 45, no. 13, pp. 1–8, 2012
work page 2012
-
[11]
Robust model predictive control: Advantages and disadvantages of tube-based methods,
D. Q. Mayne, E. C. Kerrigan, and P. Falugi, “Robust model predictive control: Advantages and disadvantages of tube-based methods,”IFAC Proceedings Volumes, vol. 44, no. 1, pp. 191–196, 2011
work page 2011
-
[12]
Min-max differential dynamic programming: Continu- ous and discrete time formulations,
W. Sun, Y . Pan, J. Lim, E. Theodorou, and P. Tsiotras, “Min-max differential dynamic programming: Continu- ous and discrete time formulations,” vol. 41, 11 2018, pp. 1–13
work page 2018
-
[13]
Min-max differential dynamic programming: Continu- ous and discrete time formulations,
W. Sun, Y . Pan, J. Lim, E. A. Theodorou, and P. Tsiotras, “Min-max differential dynamic programming: Continu- ous and discrete time formulations,”Journal of Guid- ance, Control, and Dynamics, vol. 41, no. 12, pp. 2568– 2580, 2018
work page 2018
- [14]
-
[15]
Theory and applications of robust optimization,
D. Bertsimas, D. B. Brown, and C. Caramanis, “Theory and applications of robust optimization,”SIAM Review, vol. 53, no. 3, pp. 464–501, 2011
work page 2011
-
[16]
Scalable robust optimization for safe multi-agent con- trol under unknown deterministic uncertainty,
A. T. Abdul, A. D. Saravanos, and E. A. Theodorou, “Scalable robust optimization for safe multi-agent con- trol under unknown deterministic uncertainty,” in2025 American Control Conference (ACC), 2025, pp. 3666– 3673
work page 2025
-
[17]
Convex optimization for finite-horizon robust covariance control of linear stochastic systems,
G. Kotsalis, G. Lan, and A. S. Nemirovski, “Convex optimization for finite-horizon robust covariance control of linear stochastic systems,”SIAM Journal on Control and Optimization, vol. 59, no. 1, pp. 296–319, 2021
work page 2021
-
[18]
Nonlinear robust optimization for planning and control,
A. T. Abdul, A. D. Saravanos, and E. A. Theodorou, “Nonlinear robust optimization for planning and control,” in2025 IEEE 64th Conference on Decision and Control (CDC), 2025, pp. 3383–3390
work page 2025
-
[19]
Grid: Gpu-accelerated rigid body dy- namics with analytical gradients,
B. Plancher, S. M. Neuman, R. Ghosal, S. Kuindersma, and V . J. Reddi, “Grid: Gpu-accelerated rigid body dy- namics with analytical gradients,” in2022 International Conference on Robotics and Automation (ICRA), 2022, pp. 6253–6260
work page 2022
-
[20]
Accelerating robot dynam- ics gradients on a cpu, gpu, and fpga,
B. Plancher, S. M. Neuman, T. Bourgeat, S. Kuindersma, S. Devadas, and V . J. Reddi, “Accelerating robot dynam- ics gradients on a cpu, gpu, and fpga,”IEEE Robotics and Automation Letters, vol. 6, no. 2, pp. 2335–2342, 2021
work page 2021
-
[21]
E. Adabag, M. Atal, W. Gerard, and B. Plancher, “MPCGPU: Real-time nonlinear model predictive control through preconditioned conjugate gradient on the gpu,” in2024 IEEE International Conference on Robotics and Automation (ICRA), 2024, pp. 9787–9794
work page 2024
-
[22]
cpRRTC: GPU- Parallel RRT-Connect for constrained motion planning,
J. Hu, J. Wang, and H. Christensen, “cpRRTC: GPU- Parallel RRT-Connect for constrained motion planning,” in2025 RSS Workshop on Fast Motion Planning and Control in the Era of Parallelism
-
[23]
S. Boyd, N. Parikh, E. Chu, B. Peleato, and J. Eckstein, “Distributed optimization and statistical learning via the alternating direction method of multipliers,”Found. Trends Mach. Learn., vol. 3, no. 1, p. 1–122, Jan. 2011
work page 2011
-
[24]
Osqp: An operator splitting solver for quadratic programs,
B. Stellato, G. Banjac, P. Goulart, A. Bemporad, and S. Boyd, “Osqp: An operator splitting solver for quadratic programs,” pp. 339–339, 2018
work page 2018
-
[25]
J. Eckstein and D. P. Bertsekas, “On the douglas-rachford splitting method and the proximal point algorithm for maximal monotone operators,”Math. Program., vol. 55, no. 3, p. 293–318, Jun. 1992
work page 1992
-
[26]
Splitting algorithms for the sum of two nonlinear operators,
P. L. Lions and B. Mercier, “Splitting algorithms for the sum of two nonlinear operators,” vol. 16, no. 6, p. 964–979, Dec. 1979
work page 1979
-
[27]
Conic optimization via operator splitting and homogeneous self-dual embedding,
B. O’Donoghue, E. Chu, N. Parikh, and S. Boyd, “Conic optimization via operator splitting and homogeneous self-dual embedding,”Journal of Optimization Theory and Applications, vol. 169, no. 3, pp. 1042–1068, June 2016
work page 2016
-
[28]
ApS,The MOSEK optimization toolbox for MATLAB manual
M. ApS,The MOSEK optimization toolbox for MATLAB manual. Version 9.0., 2019
work page 2019
- [29]
-
[30]
Learning to optimize: A primer and a benchmark,
T. Chen, X. Chen, W. Chen, H. Heaton, J. Liu, Z. Wang, and W. Yin, “Learning to optimize: A primer and a benchmark,”Journal of Machine Learning Research, vol. 23, no. 189, pp. 1–59, 2022
work page 2022
-
[31]
Learn to optimize—a brief overview,
K. Tang and X. Yao, “Learn to optimize—a brief overview,”National Science Review, vol. 11, no. 8, p. nwae132, 2024
work page 2024
-
[32]
Learning-based warm-starting for fast sequential convex programming and trajectory optimization,
S. Banerjee, T. Lew, R. Bonalli, A. Alfaadhel, I. A. Alomar, H. M. Shageer, and M. Pavone, “Learning-based warm-starting for fast sequential convex programming and trajectory optimization,” in2020 IEEE Aerospace Conference. IEEE, 2020, pp. 1–8
work page 2020
-
[33]
Transformer-based model predictive control: Trajectory optimization via sequence modeling,
D. Celestini, D. Gammelli, T. Guffanti, S. D’Amico, E. Capello, and M. Pavone, “Transformer-based model predictive control: Trajectory optimization via sequence modeling,”IEEE Robotics and Automation Letters, 2024
work page 2024
-
[34]
Transformermpc: Accelerating model predictive control via transformers,
V . Zinage, A. Khalil, and E. Bakolas, “Transformermpc: Accelerating model predictive control via transformers,” in2025 IEEE International Conference on Robotics and Automation (ICRA). IEEE, 2025, pp. 9221–9227
work page 2025
-
[35]
Deep distributed opti- mization for large-scale quadratic programming,
A. D. Saravanos, H. Kuperman, A. Oshin, A. T. Abdul, V . Pacelli, and E. A. Theodorou, “Deep distributed opti- mization for large-scale quadratic programming,”arXiv preprint arXiv:2412.12156, 2024
-
[36]
Acs-net: A deep unfolded admm framework for ultrasound attenuation imaging,
J. Timan ´a, S. Merino, A. Basarab, R. J. G. Van Sloun, and R. Lavarello, “Acs-net: A deep unfolded admm framework for ultrasound attenuation imaging,” in2025 IEEE International Ultrasonics Symposium (IUS), 2025, pp. 1–4
work page 2025
-
[37]
Deep flexqp: Accelerated nonlin- ear programming via deep unfolding,
A. Oshin, R. V . Ghosh, A. D. Saravanos, and E. A. Theodorou, “Deep flexqp: Accelerated nonlin- ear programming via deep unfolding,”arXiv preprint arXiv:2512.01565, 2025. SUPPLEMENTARYMATERIAL VII. DETAILS RELATED TONRTOFRAMEWORK A. Tractable Linearized Problem The cost functions are given as Qˆu(δ ˆu) = T−1X k=0 (ˆuk +δ ˆuk)⊤ Rk u (ˆuk +δ ˆuk),(18) ˜Q(kv...
-
[38]
Derivation of Block-1 update (13):This involves solving the following min ν, ˜p ngX j=1 ρ 2 ∥ ˆAjklin−1 v + ˆbj −ν j +λ lin−1 ν,j ∥2 2 + ρ 2 ∥plin−1 − ˜p+λ lin−1 p ∥2 2 s.t.∥ν j∥2 ≤˜pj j∈J1, n gK(36) Note that the above update can be decoupled with respect to the variables{ν j,˜pj}ng j=1. Therefore, we can update the variables in parallel as follows (ν li...
-
[39]
Derivation of Block-2 updates ((14) and (15)):This update involves solving the following min δ ˆu,p,kv Qˆu(δ ˆu) + ˜Q(kv) + ρ 2 ∥p− ˜plin +λ lin−1 p ∥2 2 + ngX j=1 ρ 2 ∥ ˆAjkv + ˆbj −ν lin j +λ lin−1 ν ∥2 2 s.t.(12a)(38) The above update can be decoupled with respect to the variables(δ ˆu,p)andk v as follows (δ ˆulin ,p lin) = argmin δ ˆu,p Qˆu(δ ˆu) + ρ ...
-
[40]
Compared to nominal open-loop execution (Fig. 10), which exhibits large accumulated tracking error and does not reli- ably reach the target region, the NRTO disturbance-feedback policy (Fig. 9) compensates for real-world disturbances and successfully drives the robot into the goal region. The real- world experiment is also shown in the supplementary video
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.