{
  "abstract": "This paper presents a real-time control-constrained Differential Dynamic Programming (DDP) framework for underactuated legged robots. To address the limitation of classical DDP in handling control constraints, we propose an Accelerated Projected Gradient (APG)-based control-constrained DDP (ABC-DDP), which efficiently computes constrained solutions and identifies active sets without repeated Karush-Kuhn-Tucker (KKT) inversions. A virtual constraint is introduced to integrate control constraints within a feasibility-driven multiple-shooting framework, enabling stable optimization even from dynamically infeasible initializations. The proposed method supports real-time model predictive control (MPC) with short horizons under strong underactuation. Simulation results demonstrate static two-leg standing under external disturbances, along with diverse dynamic motions including slow catwalk, upright walking, and high-speed running within a unified MPC framework. To the best of our knowledge, this is the first demonstration of static two-leg standing of a quadruped robot achieved using real-time finite-horizon MPC.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": "Journal reference: IEEE Robotics and Automation Letters (RA-L), 2026",
  "arxiv": "2608.18552",
  "author_total": 8,
  "authors": [
    {
      "name": "SeongWon Nam"
    },
    {
      "name": "Hyunyong Lee"
    },
    {
      "name": "Hansol Kang"
    },
    {
      "name": "Jiman Park"
    },
    {
      "name": "Yeongwoo Son"
    },
    {
      "name": "Bumsu Yi"
    },
    {
      "name": "Jaeyoung Oh"
    },
    {
      "name": "Hyouk Ryeol Choi"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/fty0j8q86v89g.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2608.18552",
  "fulltext_url": null,
  "id": "fty0j8q86v89g",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2608.18552",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "cs.RO"
    ],
    [
      "arxiv",
      "math.OC"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2608.18552",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-03",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/fty0j8q86v89g.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:18:36Z",
      "native_id": "2608.18552",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2608.18552"
    }
  ],
  "subjects": [
    {
      "field": "mathematics",
      "origin": "arxiv:math.OC",
      "subfield": "optimisation-control"
    }
  ],
  "title": "Real-Time Control-Constrained DDP for Underactuated Balancing of Legged Robots",
  "title_text": "Real-Time Control-Constrained DDP for Underactuated Balancing of Legged Robots",
  "type": "preprint",
  "updated_at": "2026-10-30T12:18:36Z",
  "url": "https://research.draconitic.com/paper/fty0j8q86v89g",
  "venue": "arXiv",
  "versions": [
    {
      "doi": "10.1109/lra.2026.3723262",
      "pid": null,
      "relation": "published-as",
      "title": null,
      "venue": null
    }
  ]
}