physuspension.cpp

/********************************************************************************
 *  WorldSim -- library for robot simulations                                   *
 *  Copyright (C) 2008-2013 Gianluca Massera <emmegian@yahoo.it>                *
 *                                                                              *
 *  This program is free software; you can redistribute it and/or modify        *
 *  it under the terms of the GNU General Public License as published by        *
 *  the Free Software Foundation; either version 2 of the License, or           *
 *  (at your option) any later version.                                         *
 *                                                                              *
 *  This program is distributed in the hope that it will be useful,             *
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of              *
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the               *
 *  GNU General Public License for more details.                                *
 *                                                                              *
 *  You should have received a copy of the GNU General Public License           *
 *  along with this program; if not, write to the Free Software                 *
 *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA  *
 ********************************************************************************/

#include "physuspension.h"
#include "mathutils.h"
#include "private/phyjointprivate.h"
#include "private/phyobjectprivate.h"
#include "private/worldprivate.h"

namespace farsa {

PhySuspension::PhySuspension( const wVector& axis, const wVector& centre, const wVector& x_axis, PhyObject* parent, PhyObject* child, bool cp )
    : PhyJoint( parent, child ) {
    dof = new PhyDOF( this, axis, centre, false );
    dofsv << dof;
    dofv = 1;
    forceOnJoint = wVector(0.0, 0.0, 0.0);

    //--- calculate the localMatrixParent
    //--- supposing that axis and x_axis are ortogonals
    localMatrixParent.x_ax = x_axis;
    localMatrixParent.y_ax = axis * x_axis;
    localMatrixParent.z_ax = axis;
    localMatrixParent.w_pos = centre;
    localMatrixParent.sanitifize();

    //--- calculate the local matrix respect to child object
    if ( parent ) {
        globalMatrixParent = localMatrixParent * parent->matrix();
    } else {
        globalMatrixParent = localMatrixParent;
    }
    localMatrixChild = globalMatrixParent * child->matrix().inverse();
    if ( parent ) {
        globalMatrixParent = localMatrixParent * parent->matrix();
    } else {
        globalMatrixParent = localMatrixParent;
    }

    dof->setAxis( globalMatrixParent.z_ax );
    dof->setXAxis( globalMatrixParent.x_ax );
    dof->setYAxis( globalMatrixParent.y_ax );
    dof->setCentre( globalMatrixParent.w_pos );

    if ( !localMatrixParent.sanityCheck() ) {
        qWarning( "Sanity Check Failed on localMatrixParent" );
    }
    if ( !localMatrixChild.sanityCheck() ) {
        qWarning( "Sanity Check Failed on localMatrixChild" );
    }

    if ( cp ) {
        createPrivateJoint();
    }
}

wVector PhySuspension::centre() const {
    //--- calculate global matrix if necessary
    if ( parent() ) {
        globalMatrixParent = localMatrixParent * parent()->matrix();
    }
    return globalMatrixParent.w_pos;
}

wVector PhySuspension::getForceOnJoint() const
{
    return forceOnJoint;
}

void PhySuspension::createPrivateJoint() {
#ifdef WORLDSIM_USE_NEWTON
    priv->joint = NewtonConstraintCreateUserJoint( worldpriv->world, 6, PhyJointPrivate::userBilateralHandler, 0, priv->child, priv->parent );
    NewtonJointSetUserData( priv->joint, this );
#endif
}

void PhySuspension::updateJointInfo() {
    //--- calculate the global matrices
    //--- if parent doesn't exist, then globalMatrixParent and localMatrixParent coincide and
    //--- there is no need to re-assign it because it was already done in constructor
    if ( parent() ) {
        globalMatrixParent = localMatrixParent * parent()->matrix();
    }
    globalMatrixChild = localMatrixChild * child()->matrix();

    if ( !globalMatrixParent.sanityCheck() ) {
        qWarning( "Sanity Check Failed on globalMatrixParent" );
    }
    if ( !globalMatrixChild.sanityCheck() ) {
        qWarning( "Sanity Check Failed on globalMatrixChild" );
    }

    dof->setAxis( globalMatrixParent.z_ax );
    dof->setXAxis( globalMatrixParent.x_ax );
    dof->setYAxis( globalMatrixParent.y_ax );
    dof->setCentre( globalMatrixParent.w_pos );

    PhyDOF* dof = dofsv[0];
    //--- calculate the rotation assuming the local X axis of joint frame as 0
    //--- and following the right-hand convention
    real sinAngle = (globalMatrixParent.x_ax * globalMatrixChild.x_ax) % globalMatrixChild.z_ax;
    real cosAngle = globalMatrixChild.x_ax % globalMatrixParent.x_ax;
    real angle = atan2( sinAngle, cosAngle );
    real vel;
    // Velocity is computed in two different ways depending on whether the joint is enabled or not:
    // if it is, we use Newton functions to get the angular velocities (for a better result), otherwise
    // we revert to computing the difference with the previous position divided by the timestep
    if (enabled) {
        //--- the velocity is calculated projecting the angular velocity of objects on the main axis (z_ax)
        //    This code is not general, becuase it is not appliable in the case of parent==NULL
        //    and also return different results respect to the kinematic way
        //    Then [Gianluca] comment it and replaced with the same code used in the kinematic mode
        wVector omegaParent, omegaChild;
#ifdef WORLDSIM_USE_NEWTON
        if ( parent() ) {
            NewtonBodyGetOmega( priv->parent, &omegaParent[0] );
        } else {
            omegaParent = wVector(0, 0, 0);
        }
        NewtonBodyGetOmega( priv->child, &omegaChild[0] );
#endif
        real velP = omegaParent % globalMatrixChild.z_ax;
        real velC = omegaChild % globalMatrixChild.z_ax;
        vel = velC - velP;
        //vel = (angle - dof->position()) / (world()->timeStep());
    } else {
        vel = (angle - dof->position()) / (world()->timeStep());
    }
    dof->setPosition( angle );
    dof->setVelocity( vel );
}

void PhySuspension::updateJoint( real timestep ) {
    // If the joint is disabled, we don't do anything here
    if (!enabled) {
        return;
    }

    // Updating the global matrices and the dof
    updateJointInfo();

    // const real angle = dof->position();
    const real vel = dof->velocity();

#ifdef WORLDSIM_USE_NEWTON
    //--- Restrict the movement on the centre of the joint along all tree orthonormal direction
    NewtonUserJointAddLinearRow( priv->joint, &globalMatrixChild.w_pos[0], &globalMatrixParent.w_pos[0], &globalMatrixParent.x_ax[0] );
    NewtonUserJointSetRowStiffness( priv->joint, 0.98f );
    //NewtonUserJointSetRowSpringDamperAcceleration( priv->joint, 20, 10 );
    NewtonUserJointAddLinearRow( priv->joint, &globalMatrixChild.w_pos[0], &globalMatrixParent.w_pos[0], &globalMatrixParent.y_ax[0] );
    NewtonUserJointSetRowStiffness( priv->joint, 1.0f );
    NewtonUserJointAddLinearRow( priv->joint, &globalMatrixChild.w_pos[0], &globalMatrixParent.w_pos[0], &globalMatrixParent.z_ax[0] );
    NewtonUserJointSetRowStiffness( priv->joint, 1.0f );

    //--- In order to constraint the rotation about X and Y axis of the joint
    //--- we use LinearRow (that are stronger) getting a point far from objects along
    //--- the Z axis. Doing this if the two object rotates about X or Y axes then
    //--- the difference between qChild and qParent augments and then Newton Engine will apply
    //--- a corresponding force (that applyied outside the centre of the object will become
    //--- a torque) that will blocks any rotation about X and Y axis
    real len = 5000.0;
    wVector qChild( globalMatrixChild.w_pos + globalMatrixChild.z_ax.scale(len) );
    wVector qParent( globalMatrixParent.w_pos + globalMatrixParent.z_ax.scale(len) );
    NewtonUserJointAddLinearRow( priv->joint, &qChild[0], &qParent[0], &globalMatrixParent.x_ax[0] );
    NewtonUserJointSetRowStiffness( priv->joint, 1.0 );
    NewtonUserJointAddLinearRow( priv->joint, &qChild[0], &qParent[0], &globalMatrixParent.y_ax[0] );
    NewtonUserJointSetRowStiffness( priv->joint, 1.0 );
//  NewtonUserJointAddAngularRow( priv->joint, 0.0f, &globalMatrixParent.x_ax[0] );
//  NewtonUserJointSetRowStiffness( priv->joint, 1.0f );
//  NewtonUserJointAddAngularRow( priv->joint, 0.0f, &globalMatrixParent.y_ax[0] );
//  NewtonUserJointSetRowStiffness( priv->joint, 0.98f );

    //--- The only motion supported is by velocity
    if ( dof->motion() == PhyDOF::vel ) {
        //--- I'm not sure that this implementation is correct
        real accel = 0.8f*( dof->desiredVelocity() - vel ) / ( timestep );
        NewtonUserJointAddAngularRow( priv->joint, 0.0f, &globalMatrixParent.z_ax[0] );
        NewtonUserJointSetRowAcceleration( priv->joint, accel );
        NewtonUserJointSetRowStiffness( priv->joint, dof->stiffness() );
        if ( dof->maxForce() > 0.0 ) {
            NewtonUserJointSetRowMinimumFriction( priv->joint, -dof->maxForce() );
            NewtonUserJointSetRowMaximumFriction( priv->joint, +dof->maxForce() );
        }
    }

    //--- Retrive forces applied to the joint by the constraints
    forceOnJoint.x = NewtonUserJointGetRowForce (priv->joint, 0);
    forceOnJoint.y = NewtonUserJointGetRowForce (priv->joint, 1);
    forceOnJoint.z = NewtonUserJointGetRowForce (priv->joint, 2);
#endif

}

} // end namespace farsa