{
  "summary": {
    "ground": {
      "samples": 80,
      "vertical_response_ratio_quantiles": [
        2.849745342357671,
        7.852099859883923,
        10.98498702380813
      ],
      "vertical_effective_mass_kg_quantiles": [
        1.732645168153464,
        4.774076714809425,
        6.678872110475343
      ]
    },
    "sand": {
      "samples": 80,
      "vertical_response_ratio_quantiles": [
        2.3254253594877143,
        7.27477588728712,
        11.341106598511875
      ],
      "vertical_effective_mass_kg_quantiles": [
        1.4138586185685302,
        4.423063739470569,
        6.89539281189522
      ]
    },
    "mud": {
      "samples": 80,
      "vertical_response_ratio_quantiles": [
        2.3630702257756404,
        7.54995217649741,
        13.480644338037047
      ],
      "vertical_effective_mass_kg_quantiles": [
        1.4367466972715892,
        4.5903709233104255,
        8.196231757526524
      ]
    },
    "sand+mud+rocks": {
      "samples": 80,
      "vertical_response_ratio_quantiles": [
        2.3902766463828704,
        6.987376942817255,
        12.017148792949023
      ],
      "vertical_effective_mass_kg_quantiles": [
        1.4532882010007853,
        4.24832518123289,
        7.306426466113006
      ]
    }
  },
  "interpretation": "Compares the isolated-link velocity-unloading approximation with J M^-1 J^T for one hypothetical COM force in the nominal MuJoCo articulation. Omits contact constraints, PD stiffness, simultaneous forces and native PhysX differences. It is not a closed-loop corrected-coupling experiment or proof that this approximation causes failures."
}