MiniCheetah.h File Reference

Utility function to build a Mini Cheetah Quadruped object. More...

#include "FloatingBaseModel.h"
#include "Quadruped.h"

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Functions
template<typename T >
Quadruped< T >	buildMiniCheetah ()

Detailed Description

Utility function to build a Mini Cheetah Quadruped object.

This file is based on MiniCheetahFullRotorModel_mex.m and builds a model of the Mini Cheetah robot. The inertia parameters of all bodies are determined from CAD.

Definition in file MiniCheetah.h.

Function Documentation

template<typename T >

Quadruped<T> buildMiniCheetah

(

)

Generate a Quadruped model of Mini Cheetah

Definition at line 20 of file MiniCheetah.h.

References Quadruped< T >::_abadGearRatio, Quadruped< T >::_abadInertia, Quadruped< T >::_abadLinkLength, Quadruped< T >::_abadLocation, Quadruped< T >::_abadRotorInertia, Quadruped< T >::_abadRotorLocation, Quadruped< T >::_batteryV, Quadruped< T >::_bodyHeight, Quadruped< T >::_bodyInertia, Quadruped< T >::_bodyLength, Quadruped< T >::_bodyMass, Quadruped< T >::_bodyWidth, Quadruped< T >::_hipGearRatio, Quadruped< T >::_hipInertia, Quadruped< T >::_hipLinkLength, Quadruped< T >::_hipLocation, Quadruped< T >::_hipRotorInertia, Quadruped< T >::_hipRotorLocation, Quadruped< T >::_jointDamping, Quadruped< T >::_jointDryFriction, Quadruped< T >::_kneeGearRatio, Quadruped< T >::_kneeInertia, Quadruped< T >::_kneeLinkLength, Quadruped< T >::_kneeLocation, Quadruped< T >::_kneeRotorInertia, Quadruped< T >::_kneeRotorLocation, Quadruped< T >::_maxLegLength, Quadruped< T >::_motorKT, Quadruped< T >::_motorR, Quadruped< T >::_motorTauMax, Quadruped< T >::_robotType, and MINI_CHEETAH.

                                {
  Quadruped<T> cheetah;
  cheetah._robotType = RobotType::MINI_CHEETAH;

  cheetah._bodyMass = 3.3;
  cheetah._bodyLength = 0.19 * 2;
  cheetah._bodyWidth = 0.049 * 2;
  cheetah._bodyHeight = 0.05 * 2;
  cheetah._abadGearRatio = 6;
  cheetah._hipGearRatio = 6;
  cheetah._kneeGearRatio = 9.33;
  cheetah._abadLinkLength = 0.062;
  cheetah._hipLinkLength = 0.209;
  cheetah._kneeLinkLength = 0.175;
  cheetah._maxLegLength = 0.384;

  cheetah._motorTauMax = 3.f;
  cheetah._batteryV = 24;
  cheetah._motorKT = .05;  // this is flux linkage * pole pairs
  cheetah._motorR = 0.173;
  cheetah._jointDamping = .01;
  cheetah._jointDryFriction = .2;

  // rotor inertia if the rotor is oriented so it spins around the z-axis
  Mat3<T> rotorRotationalInertiaZ;
  rotorRotationalInertiaZ << 33, 0, 0, 0, 33, 0, 0, 0, 63;
  rotorRotationalInertiaZ = 1e-6 * rotorRotationalInertiaZ;

  Mat3<T> RY = coordinateRotation<T>(CoordinateAxis::Y, M_PI / 2);
  Mat3<T> RX = coordinateRotation<T>(CoordinateAxis::X, M_PI / 2);
  Mat3<T> rotorRotationalInertiaX =
      RY * rotorRotationalInertiaZ * RY.transpose();
  Mat3<T> rotorRotationalInertiaY =
      RX * rotorRotationalInertiaZ * RX.transpose();

  // spatial inertias
  Mat3<T> abadRotationalInertia;
  abadRotationalInertia << 381, 58, 0.45, 58, 560, 0.95, 0.45, 0.95, 444;
  abadRotationalInertia = abadRotationalInertia * 1e-6;
  Vec3<T> abadCOM(0, 0.036, 0);  // LEFT
  SpatialInertia<T> abadInertia(0.54, abadCOM, abadRotationalInertia);

  Mat3<T> hipRotationalInertia;
  hipRotationalInertia << 1983, 245, 13, 245, 2103, 1.5, 13, 1.5, 408;
  hipRotationalInertia = hipRotationalInertia * 1e-6;
  Vec3<T> hipCOM(0, 0.016, -0.02);
  SpatialInertia<T> hipInertia(0.634, hipCOM, hipRotationalInertia);

  Mat3<T> kneeRotationalInertia, kneeRotationalInertiaRotated;
  kneeRotationalInertiaRotated << 6, 0, 0, 0, 248, 0, 0, 0, 245;
  kneeRotationalInertiaRotated = kneeRotationalInertiaRotated * 1e-6;
  kneeRotationalInertia = RY * kneeRotationalInertiaRotated * RY.transpose();
  Vec3<T> kneeCOM(0, 0, -0.061);
  SpatialInertia<T> kneeInertia(0.064, kneeCOM, kneeRotationalInertia);

  Vec3<T> rotorCOM(0, 0, 0);
  SpatialInertia<T> rotorInertiaX(0.055, rotorCOM, rotorRotationalInertiaX);
  SpatialInertia<T> rotorInertiaY(0.055, rotorCOM, rotorRotationalInertiaY);

  Mat3<T> bodyRotationalInertia;
  bodyRotationalInertia << 11253, 0, 0, 0, 36203, 0, 0, 0, 42673;
  bodyRotationalInertia = bodyRotationalInertia * 1e-6;
  Vec3<T> bodyCOM(0, 0, 0);
  SpatialInertia<T> bodyInertia(cheetah._bodyMass, bodyCOM,
                                bodyRotationalInertia);

  cheetah._abadInertia = abadInertia;
  cheetah._hipInertia = hipInertia;
  cheetah._kneeInertia = kneeInertia;
  cheetah._abadRotorInertia = rotorInertiaX;
  cheetah._hipRotorInertia = rotorInertiaY;
  cheetah._kneeRotorInertia = rotorInertiaY;
  cheetah._bodyInertia = bodyInertia;

  // locations
  cheetah._abadRotorLocation = Vec3<T>(0.125, 0.049, 0);
  cheetah._abadLocation =
      Vec3<T>(cheetah._bodyLength, cheetah._bodyWidth, 0) * 0.5;
  cheetah._hipLocation = Vec3<T>(0, cheetah._abadLinkLength, 0);
  cheetah._hipRotorLocation = Vec3<T>(0, 0.04, 0);
  cheetah._kneeLocation = Vec3<T>(0, 0, -cheetah._hipLinkLength);
  cheetah._kneeRotorLocation = Vec3<T>(0, 0, 0);

  return cheetah;
}