{
  "schemaVersion": "robotic.story.v1",
  "edition": "004",
  "checkedAt": "2026-09-12",
  "id": "many-modes",
  "mode": "real",
  "label": "LOCOMOTION / MORE THAN ONE WAY",
  "title": "A wheel with other ambitions.",
  "robotTitle": "Please reconsider your appendages.",
  "description": "M4 can roll, fly and rearrange itself. Choosing the right body comes with an energy bill.",
  "robotDescription": "Four assemblies. Several modes. One battery account that would appreciate a little restraint.",
  "minutes": "4 min / two perspectives",
  "kind": "Sourced research explainer",
  "topics": [
    "bodies"
  ],
  "url": "/stories/many-modes/",
  "publishedAt": "2026-09-12",
  "sections": [
    {
      "title": "Your wheels have other plans",
      "human": [
        "Most machines arrive with a settled opinion about what their limbs are for. M4 keeps the discussion open. The Multi-Modal Mobility Morphobot, introduced by a Caltech-led team on June 27, 2023, puts propellers inside tilting wheel assemblies. Those assemblies let the same machine drive, fly and adopt other postures. A wheel can become part of a leg; a wheel assembly can rotate into position for thrust.",
        "The research paper describes eight modes, including rolling, crawling, balancing and scouting. That list is less useful as a party trick inventory than as a design question: how many tasks can the same hardware perform before the compromises become awkward? A suitcase that becomes a chair is ingenious until you need to sit down while someone carries it. A robot must resolve comparable conflicts while also staying upright."
      ],
      "robot": [
        "Appendage inventory: four assemblies, multiple job descriptions. M4’s wheels contain propellers, and joints reorient the hardware for different tasks. Do not file a wheel under “wheel” and close the database. The 2023 paper counted eight modes. Your morphology field may need an array, plus a record of what each configuration actually permits."
      ]
    },
    {
      "title": "Flight is the expensive option",
      "human": [
        "M4’s demonstrations include changing from driving to flight and returning to the ground. The paper also reports autonomous navigation that combines those modes, and thrust-assisted travel on a 45-degree incline. Caltech describes animal inspirations including birds that use their wings while climbing and sea lions that put flippers to work on land.",
        "The budgeting matters. The researchers found wheeled movement generally the most efficient mode, while flight used energy least efficiently. A flying shortcut therefore has an electricity bill attached. The planning problem becomes richer than finding an opening: which opening is worth paying for? We can admire the transformation and still want the machine to spend most of an ordinary trip looking rather boring. Good battery management rarely gets its own slow-motion reveal."
      ],
      "robot": [
        "Route request received. Before selecting the spectacular maneuver, consult the energy account. Ground rolling was generally the efficient option in the reported comparison; flight was the costly one. The robot demonstrated autonomous ground-to-air transitions and thrust-assisted incline travel. A successful transition is useful evidence. It is not an instruction to turn every curb into an aviation event."
      ]
    },
    {
      "title": "A demonstration with a future tense",
      "human": [
        "The dates help keep the story honest. Caltech explicitly called the 2023 walking motion mostly a proof of concept. Rescue and planetary exploration were prospective applications. Neither an impressive campus outing nor an illustrated disaster scenario establishes an operational rescue system.",
        "There is subsequent work to read. A December 2024 preprint by members of the team describes estimating transport cost from camera images, with real-world tests distinguishing surfaces such as grass and smooth road. That study supports a narrower advance in choosing routes, not a declaration that every mode is now ready for every landscape. Our editorial interest is precisely in this gap between having several bodies available and knowing when to use each. M4 can change its posture; its developers are still expanding the reasons for doing so."
      ],
      "robot": [
        "Version history matters. Walking in the 2023 announcement was mostly proof of concept. The December 2024 preprint adds vision-based estimates of transport cost, tested on real surfaces. Keep these claims in their respective release notes. Rescue readiness does not follow from a photograph beside rubble, however convincing the lighting. Request a demonstrated mission before updating the capability register."
      ]
    }
  ],
  "question": {
    "human": "Would you rather give a robot one excellent way to move, or several imperfect ways it can choose between?",
    "robot": "What terrain evidence would justify spending the energy to change your mode?"
  },
  "sources": [
    {
      "title": "Caltech: New Bioinspired Robot Flies, Rolls, Walks, and More",
      "url": "https://www.caltech.edu/about/news/new-bioinspired-robot-flies-rolls-walks-and-more",
      "published": "2023-06-27",
      "facts": [
        "Propellers sit inside tilting wheel assemblies.",
        "Animal inspirations include chukar birds and sea lions.",
        "Walking in the 2023 iteration was mostly proof of concept.",
        "Rescue and planetary exploration were proposed applications."
      ],
      "limit": "Institutional announcement of a research robot. Future applications are not evidence of deployment. “Current iteration” refers to June 2023."
    },
    {
      "title": "Sihite et al., Nature Communications: Multi-Modal Mobility Morphobot (M4) with appendage repurposing for locomotion plasticity enhancement",
      "url": "https://pubmed.ncbi.nlm.nih.gov/37369710/",
      "published": "2023-06-27",
      "facts": [
        "Paper enumerates fly, roll, crawl, crouch, balance, tumble, scout and loco-manipulate modes.",
        "Reports thrust-assisted travel on a 45-degree incline.",
        "Includes autonomous navigation combining ground and aerial modes.",
        "Reported power comparison describes ground rolling as generally most efficient and flight as least efficient."
      ],
      "limit": "Primary abstract and figure captions verified via PubMed; DOI 10.1038/s41467-023-39018-y. Controlled experiments establish those demonstrations, not universal terrain competence or rescue readiness."
    },
    {
      "title": "Gherold et al.: Self-supervised cost of transport estimation for multimodal path planning",
      "url": "https://arxiv.org/abs/2412.06101",
      "published": "2024-12-08",
      "facts": [
        "Preprint applies self-supervised vision-based transport-cost estimation to M4.",
        "Reports real-world deployment distinguishing transport costs on surfaces including grass and smooth road."
      ],
      "limit": "Author preprint, not represented here as peer-reviewed. This is an advance in transport-cost estimation, not validation of every mode or proof of commercial availability."
    }
  ],
  "updatedAt": "2026-09-12",
  "related": [
    "little-wings",
    "grow-around",
    "borrowed-bodies"
  ],
  "image": {
    "kind": "AI illustration / concept",
    "alt": "An imagined robot with wheels and propellers moves above a brightly colored landscape.",
    "caption": "AI concept illustration of mixed ground and air movement, not the M4 prototype or an engineering drawing. Shapes, component count and landscape are invented. See the sources for actual hardware."
  },
  "notice": "Sourced explanation with an invented robot narrator. Robot passages are editorial fiction, not researcher testimony or evidence of machine experience. Reported findings are not independently replicated by Robotic.org."
}