EscapeModel.cpp

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/*
 * Copyright © 2012, United States Government, as represented by the
 * Administrator of the National Aeronautics and Space Administration.
 * All rights reserved.
 * 
 * The NASA Tensegrity Robotics Toolkit (NTRT) v1 platform is licensed
 * under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * http://www.apache.org/licenses/LICENSE-2.0.
 * 
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific language
 * governing permissions and limitations under the License.
*/

// This module
#include "EscapeModel.h"
// This library
#include "core/tgBasicActuator.h"
#include "core/tgRod.h"
#include "tgcreator/tgBuildSpec.h"
#include "tgcreator/tgBasicActuatorInfo.h"
#include "tgcreator/tgRodInfo.h"
#include "tgcreator/tgStructure.h"
#include "tgcreator/tgStructureInfo.h"
// The Bullet Physics library
#include "LinearMath/btVector3.h"
// The C++ Standard Library
#include <stdexcept>

namespace
{
    // see tgBaseString.h for a descripton of some of these rod parameters
    // (specifically, those related to the motor moving the strings.)
    // NOTE that any parameter that depends on units of length will scale
    // with the current gravity scaling. E.g., with gravity as 98.1,
    // the length units below are in decimeters.

    // Note: This current model of the SUPERball rod is 1.5m long by 3 cm radius,
    // which is 0.00424 m^3.
    // For SUPERball v1.5, mass = 3.5kg per strut, which comes out to 
    // 0.825 kg / (decimeter^3).

    // similarly, frictional parameters are for the tgRod objects.
    const struct Config
    {
        double density;
        double radius;
        //double stiffness_passive;
        double stiffness;
        double damping;
        double rod_length;
        double rod_space;    
        double friction;
        double rollFriction;
        double restitution;
        bool   hist;
        double rotation;  
        double maxTens;
        double targetVelocity;
    } c =
    {
       0.40374,   // density (kg / length^3)
       0.40,      // radius (length)
       //998.25,    // stiffness_passive (kg / sec^2)
       3152.36,   // stiffness_active (kg / sec^2)
       50.0,      // damping (kg / sec)
       17.00,     // rod_length (length)
       17.00/4,   // rod_space (length)
       0.99,      // friction (unitless)
       0.01,     // rollFriction (unitless)
       0.0,      // restitution (?)
       0,                                       // History logging (boolean)
       0,        // rotation
       100000,   // maxTens
       10000,    // targetVelocity
#if (0) // Acceleration limit removed 12/10/14
       5000     // maxAcc
#endif
       //100000,   // maxTens
       //10000,    // targetVelocity
       //20000     // maxAcc

           // Use the below values for earlier versions of simulation.
           // 1.006,    
           // 0.31,     
           // 300000.0, 
           // 3000.0,   
           // 15.0,     
           // 7.5,      
   };

} // namespace

EscapeModel::EscapeModel() : tgModel() 
{
}

EscapeModel::~EscapeModel()
{
}

void EscapeModel::addNodes(tgStructure& s)
{
    const double half_length = c.rod_length / 2;

    s.addNode(-c.rod_space,  -half_length, 0);            // 0
    s.addNode(-c.rod_space,   half_length, 0);            // 1
    s.addNode( c.rod_space,  -half_length, 0);            // 2
    s.addNode( c.rod_space,   half_length, 0);            // 3
    s.addNode(0,           -c.rod_space,   -half_length); // 4
    s.addNode(0,           -c.rod_space,    half_length); // 5
    s.addNode(0,            c.rod_space,   -half_length); // 6
    s.addNode(0,            c.rod_space,    half_length); // 7
    s.addNode(-half_length, 0,            c.rod_space);   // 8
    s.addNode( half_length, 0,            c.rod_space);   // 9
    s.addNode(-half_length, 0,           -c.rod_space);   // 10
    s.addNode( half_length, 0,           -c.rod_space);   // 11
}

void EscapeModel::addRods(tgStructure& s)
{
    s.addPair( 0,  1, "rod");
    s.addPair( 2,  3, "rod");
    s.addPair( 4,  5, "rod");
    s.addPair( 6,  7, "rod");
    s.addPair( 8,  9, "rod");
    s.addPair(10, 11, "rod");
}

// 24 muscles in total
void EscapeModel::addMuscles(tgStructure& s)
{
    s.addPair(0, 4,  "muscle");
    s.addPair(0, 5,  "muscle");
    s.addPair(0, 8,  "muscle");
    s.addPair(0, 10, "muscle");

    s.addPair(1, 6,  "muscle");
    s.addPair(1, 7,  "muscle");
    s.addPair(1, 8,  "muscle");
    s.addPair(1, 10, "muscle");

    s.addPair(2, 4,  "muscle");
    s.addPair(2, 5,  "muscle");
    s.addPair(2, 9,  "muscle");
    s.addPair(2, 11, "muscle");

    s.addPair(3, 7,  "muscle");
    s.addPair(3, 6,  "muscle");
    s.addPair(3, 9,  "muscle");
    s.addPair(3, 11, "muscle");

    s.addPair(4, 10, "muscle");
    s.addPair(4, 11, "muscle");

    s.addPair(5, 8,  "muscle");
    s.addPair(5, 9,  "muscle");

    s.addPair(6, 10, "muscle");
    s.addPair(6, 11, "muscle");

    s.addPair(7, 8,  "muscle");
    s.addPair(7, 9,  "muscle");

}

void EscapeModel::setup(tgWorld& world)
{

    const tgRod::Config rodConfig(c.radius, c.density, c.friction, 
                                                                c.rollFriction, c.restitution);
    
    tgBasicActuator::Config activeMuscleConfig(c.stiffness, c.damping, c.hist, c.rotation,
                                                                                    c.maxTens, c.targetVelocity);
/*
    tgBasicActuator::Config passiveMuscleConfig(c.stiffness_passive, c.damping, c.hist, c.rotation,
                                                                                    c.maxTens, c.targetVelocity, 
                                                                                    c.maxAcc);*/
            
    // Start creating the structure
    tgStructure s;
    addNodes(s);
    addRods(s);
    addMuscles(s);
    s.move(btVector3(0, 10, 0));

    // Add a rotation. This is needed if the ground slopes too much,
    // otherwise  glitches put a rod below the ground.
    btVector3 rotationPoint = btVector3(0, 0, 0); // origin
    btVector3 rotationAxis = btVector3(0, 1, 0);  // y-axis
    double rotationAngle = M_PI/2;
    s.addRotation(rotationPoint, rotationAxis, rotationAngle);

    // Create the build spec that uses tags to turn the structure into a real model
    tgBuildSpec spec;
    spec.addBuilder("rod", new tgRodInfo(rodConfig));
    spec.addBuilder("muscle", new tgBasicActuatorInfo(activeMuscleConfig));
    //spec.addBuilder("active muscle", new tgBasicActuatorInfo(activeMuscleConfig));
    //spec.addBuilder("passive muscle", new tgBasicActuatorInfo(passiveMuscleConfig));
    
    // Create your structureInfo
    tgStructureInfo structureInfo(s, spec);

    // Use the structureInfo to build ourselves
    structureInfo.buildInto(*this, world);

    // We could now use tgCast::filter or similar to pull out the
    // models (e.g. muscles) that we want to control. 
    allMuscles = tgCast::filter<tgModel, tgBasicActuator> (getDescendants());

    // call the onSetup methods of all observed things e.g. controllers
    notifySetup();

    // Actually setup the children
    tgModel::setup(world);
}

void EscapeModel::step(double dt)
{
    // Precondition
    if (dt <= 0.0)
    {
        throw std::invalid_argument("dt is not positive");
    }
    else
    {
        // Notify observers (controllers) of the step so that they can take action
        notifyStep(dt);
        tgModel::step(dt);  // Step any children
    }
}

void EscapeModel::onVisit(tgModelVisitor& r)
{
    tgModel::onVisit(r);
}

const std::vector<tgBasicActuator*>& EscapeModel::getAllMuscles() const
{
    return allMuscles;
}
    
void EscapeModel::teardown()
{
    notifyTeardown();
    tgModel::teardown();
}
           
// Return the center of mass of this model
// Pre-condition: This model has 6 rods
std::vector<double> EscapeModel::getBallCOM() {   
    std::vector <tgRod*> rods = find<tgRod>("rod");
    assert(!rods.empty());

    btVector3 ballCenterOfMass(0, 0, 0);
    double ballMass = 0.0; 
    for (std::size_t i = 0; i < rods.size(); i++) {   
        const tgRod* const rod = rods[i];
        assert(rod != NULL);
        const double rodMass = rod->mass();
        const btVector3 rodCenterOfMass = rod->centerOfMass();
        ballCenterOfMass += rodCenterOfMass * rodMass;
        ballMass += rodMass;
    }

    assert(ballMass > 0.0);
    ballCenterOfMass /= ballMass;

    // Copy to the result std::vector
    std::vector<double> result(3);
    for (size_t i = 0; i < 3; ++i) { result[i] = ballCenterOfMass[i]; }
    //std::cout<<"COM: (" << result[0] << ", " << result[1] << ", " << result[2] << ")\n";

    return result;
}