btMultiBodyJointMotor.cpp

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/*
Bullet Continuous Collision Detection and Physics Library
Copyright (c) 2013 Erwin Coumans  http://bulletphysics.org

This software is provided 'as-is', without any express or implied warranty.
In no event will the authors be held liable for any damages arising from the use of this software.
Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it freely,
subject to the following restrictions:

1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
3. This notice may not be removed or altered from any source distribution.
*/


#include "btMultiBodyJointMotor.h"
#include "btMultiBody.h"
#include "btMultiBodyLinkCollider.h"
#include "BulletCollision/CollisionDispatch/btCollisionObject.h"


btMultiBodyJointMotor::btMultiBodyJointMotor(btMultiBody* body, int link, btScalar desiredVelocity, btScalar maxMotorImpulse)
        :btMultiBodyConstraint(body,body,link,body->getLink(link).m_parent,1,true),
        m_desiredVelocity(desiredVelocity),
        m_desiredPosition(0),
        m_kd(1.),
        m_kp(0),
        m_erp(1),
        m_rhsClamp(SIMD_INFINITY)
{

        m_maxAppliedImpulse = maxMotorImpulse;
        // the data.m_jacobians never change, so may as well
    // initialize them here


}

void btMultiBodyJointMotor::finalizeMultiDof()
{
        allocateJacobiansMultiDof();
        // note: we rely on the fact that data.m_jacobians are
        // always initialized to zero by the Constraint ctor
        int linkDoF = 0;
        unsigned int offset = 6 + (m_bodyA->getLink(m_linkA).m_dofOffset + linkDoF);

        // row 0: the lower bound
        // row 0: the lower bound
        jacobianA(0)[offset] = 1;

        m_numDofsFinalized = m_jacSizeBoth;
}

btMultiBodyJointMotor::btMultiBodyJointMotor(btMultiBody* body, int link, int linkDoF, btScalar desiredVelocity, btScalar maxMotorImpulse)
        //:btMultiBodyConstraint(body,0,link,-1,1,true),
        :btMultiBodyConstraint(body,body,link,body->getLink(link).m_parent,1,true),
        m_desiredVelocity(desiredVelocity),
        m_desiredPosition(0),
        m_kd(1.),
        m_kp(0),
    m_erp(1),
        m_rhsClamp(SIMD_INFINITY)
{
        btAssert(linkDoF < body->getLink(link).m_dofCount);

        m_maxAppliedImpulse = maxMotorImpulse;

}
btMultiBodyJointMotor::~btMultiBodyJointMotor()
{
}

int btMultiBodyJointMotor::getIslandIdA() const
{
        if (this->m_linkA < 0)
        {
                btMultiBodyLinkCollider* col = m_bodyA->getBaseCollider();
                if (col)
                        return col->getIslandTag();
        }
        else
        {
                if (m_bodyA->getLink(m_linkA).m_collider)
                {
                        return m_bodyA->getLink(m_linkA).m_collider->getIslandTag();
                }
        }
        return -1;
}

int btMultiBodyJointMotor::getIslandIdB() const
{
        if (m_linkB < 0)
        {
                btMultiBodyLinkCollider* col = m_bodyB->getBaseCollider();
                if (col)
                        return col->getIslandTag();
        }
        else
        {
                if (m_bodyB->getLink(m_linkB).m_collider)
                {
                        return m_bodyB->getLink(m_linkB).m_collider->getIslandTag();
                }
        }
        return -1;
}


void btMultiBodyJointMotor::createConstraintRows(btMultiBodyConstraintArray& constraintRows,
                btMultiBodyJacobianData& data,
                const btContactSolverInfo& infoGlobal)
{
    // only positions need to be updated -- data.m_jacobians and force
    // directions were set in the ctor and never change.
        
        if (m_numDofsFinalized != m_jacSizeBoth)
        {
        finalizeMultiDof();
        }

        //don't crash
        if (m_numDofsFinalized != m_jacSizeBoth)
                return;

        if (m_maxAppliedImpulse==0.f)
                return;

        const btScalar posError = 0;
        const btVector3 dummy(0, 0, 0);

        for (int row=0;row<getNumRows();row++)
        {
                btMultiBodySolverConstraint& constraintRow = constraintRows.expandNonInitializing();

        int dof = 0;
        btScalar currentPosition = m_bodyA->getJointPosMultiDof(m_linkA)[dof];
        btScalar currentVelocity = m_bodyA->getJointVelMultiDof(m_linkA)[dof];
        btScalar positionStabiliationTerm = m_erp*(m_desiredPosition-currentPosition)/infoGlobal.m_timeStep;
                
        btScalar velocityError = (m_desiredVelocity - currentVelocity);
        btScalar rhs =   m_kp * positionStabiliationTerm + currentVelocity+m_kd * velocityError;
                if (rhs>m_rhsClamp)
                {
                        rhs=m_rhsClamp;
                }
                if (rhs<-m_rhsClamp)
                {
                        rhs=-m_rhsClamp;
                }
        
        
                fillMultiBodyConstraint(constraintRow,data,jacobianA(row),jacobianB(row),dummy,dummy,dummy,dummy,posError,infoGlobal,-m_maxAppliedImpulse,m_maxAppliedImpulse,false,1,false,rhs);
                constraintRow.m_orgConstraint = this;
                constraintRow.m_orgDofIndex = row;
                {
                        //expect either prismatic or revolute joint type for now
                        btAssert((m_bodyA->getLink(m_linkA).m_jointType == btMultibodyLink::eRevolute)||(m_bodyA->getLink(m_linkA).m_jointType == btMultibodyLink::ePrismatic));
                        switch (m_bodyA->getLink(m_linkA).m_jointType)
                        {
                                case btMultibodyLink::eRevolute:
                                {
                                        constraintRow.m_contactNormal1.setZero();
                                        constraintRow.m_contactNormal2.setZero();
                                        btVector3 revoluteAxisInWorld = quatRotate(m_bodyA->getLink(m_linkA).m_cachedWorldTransform.getRotation(),m_bodyA->getLink(m_linkA).m_axes[0].m_topVec);
                                        constraintRow.m_relpos1CrossNormal=revoluteAxisInWorld;
                                        constraintRow.m_relpos2CrossNormal=-revoluteAxisInWorld;
                                        
                                        break;
                                }
                                case btMultibodyLink::ePrismatic:
                                {
                                        btVector3 prismaticAxisInWorld = quatRotate(m_bodyA->getLink(m_linkA).m_cachedWorldTransform.getRotation(),m_bodyA->getLink(m_linkA).m_axes[0].m_bottomVec);
                                        constraintRow.m_contactNormal1=prismaticAxisInWorld;
                                        constraintRow.m_contactNormal2=-prismaticAxisInWorld;
                                        constraintRow.m_relpos1CrossNormal.setZero();
                                        constraintRow.m_relpos2CrossNormal.setZero();
                                        
                                        break;
                                }
                                default:
                                {
                                        btAssert(0);
                                }
                        };
                        
                }

        }

}