{
  "abstract": "Safe rehabilitation is an interaction-dynamics problem: the controller must regulate a prescribed motion while absorbing involuntary spasm, voluntary effort, actuator compliance, and model mismatch as disturbances. This paper instantiates the predictive interaction-dynamics framework of the base pHRI formulation on a SEA knee joint. SEA feedforward reduces the gravity-compensated knee to the same scalar double integrator as the base framework, while a dynamic-residual measurement from spring deflection supplies an interaction-disturbance observation. A steady-state target converts the estimated disturbance into a cancelling input, and a finite-horizon quadratic program regulates deviations from that target under range-of-motion, torque, and velocity constraints. The evaluation matches stiffness and damping across controllers so gains cannot be attributed to higher impedance. Under a motion-opposing $15\\unit{Nm}$ step, classical impedance and MPC without estimation produce about $500\\unit{mrad}$ steady-state error, whereas Kalman-augmented interaction MPC reduces this to $1.17\\unit{mrad}$ at 100~Hz and $0.70\\unit{mrad}$ at 500~Hz; the 500~Hz peak is $7.27\\unit{mrad}$. In 30 randomized trials, the 95th-percentile peak is $21.57\\unit{mrad}$. Bounded Assist-as-Needed scheduling, a corrective-channel energy tank, constrained OSQP stress cases, direct MuJoCo execution, and a posture-clamped MyoSuite knee slice are implemented. The framework holds on a single-mass, closed-inner-loop SEA approximation; an explicit two-mass plant with a finite-bandwidth, pole-placed inner torque loop (Section~VIII) confirms this for nominal tracking but shows delivered torque can overshoot the commanded bound by 21.7\\% near saturation. Scope excludes clinical intent recognition, full-system passivity, safety certification, hardware trials, and multi-joint validation.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2606.13485",
  "author_total": 2,
  "authors": [
    {
      "name": "Yongyan Cao"
    },
    {
      "name": "Jinshan Tang"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/9h0knaqmgbwb9.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2606.13485",
  "fulltext_url": null,
  "id": "9h0knaqmgbwb9",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2606.13485",
  "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.HC"
    ],
    [
      "arxiv",
      "cs.NE"
    ],
    [
      "arxiv",
      "cs.RO"
    ],
    [
      "arxiv",
      "cs.SY"
    ],
    [
      "arxiv",
      "eess.SY"
    ],
    [
      "arxiv",
      "physics.med-ph"
    ],
    [
      "openalex",
      "2204|Prosthetics and Rehabilitation Robotics"
    ]
  ],
  "openalex": "W7164552076",
  "pdf_url": "https://arxiv.org/pdf/2606.13485",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-28",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/9h0knaqmgbwb9.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:25:12Z",
      "native_id": "2606.13485",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2606.13485"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:physics.med-ph",
      "subfield": "biological-medical"
    }
  ],
  "title": "Interaction Dynamics MPC for Knee Rehabilitation Exoskeletons: A Closed-Loop SEA Outer-Loop Study",
  "title_text": "Interaction Dynamics MPC for Knee Rehabilitation Exoskeletons: A Closed-Loop SEA Outer-Loop Study",
  "type": "preprint",
  "updated_at": "2026-10-30T12:25:12Z",
  "url": "https://research.draconitic.com/paper/9h0knaqmgbwb9",
  "venue": "arXiv",
  "versions": []
}