Distance.cpp

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/* SPDX-FileCopyrightText: 2009 Ruben Smits
 *
 * SPDX-License-Identifier: LGPL-2.1-or-later */
 
#include "Distance.hpp"
#include "kdl/kinfam_io.hpp"
#include <math.h>
#include <string.h>
 
namespace iTaSC
{
// a distance constraint is characterized by 5 values: alpha, tolerance, K, yd, yddot
static const unsigned int distanceCacheSize = sizeof(double)*5 + sizeof(e_scalar)*6;
 
Distance::Distance(double armlength, double accuracy, unsigned int maximum_iterations):
    ConstraintSet(1,accuracy,maximum_iterations),
    m_chiKdl(6),m_jac(6),m_cache(NULL),
    m_distCCh(-1),m_distCTs(0)
{
    m_chain.addSegment(Segment(Joint(Joint::RotZ)));
    m_chain.addSegment(Segment(Joint(Joint::RotX)));
    m_chain.addSegment(Segment(Joint(Joint::TransY)));
    m_chain.addSegment(Segment(Joint(Joint::RotZ)));
    m_chain.addSegment(Segment(Joint(Joint::RotY)));
    m_chain.addSegment(Segment(Joint(Joint::RotX)));
 
    m_fksolver = new KDL::ChainFkSolverPos_recursive(m_chain);
    m_jacsolver = new KDL::ChainJntToJacSolver(m_chain);
    m_Cf(0,2)=1.0;
    m_alpha = 1.0;
    m_tolerance = 0.05;
    m_maxerror = armlength/2.0;
    m_K = 20.0;
    m_Wy(0) = m_alpha/*/(m_tolerance*m_K)*/;
    m_yddot = m_nextyddot = 0.0;
    m_yd = m_nextyd = KDL::epsilon;
    memset(&m_data, 0, sizeof(m_data));
    // initialize the data with normally fixed values
    m_data.id = ID_DISTANCE;
    m_values.id = ID_DISTANCE;
    m_values.number = 1;
    m_values.alpha = m_alpha;
    m_values.feedback = m_K;
    m_values.tolerance = m_tolerance;
    m_values.values = &m_data;
}
 
Distance::~Distance()
{
    delete m_fksolver;
    delete m_jacsolver;
}
 
bool Distance::computeChi(Frame& pose)
{
    double dist, alpha, beta, gamma;
    dist = pose.p.Norm();
    Rotation basis;
    if (dist < KDL::epsilon) {
        // distance is almost 0, no need for initial rotation
        m_chi(0) = 0.0;
        m_chi(1) = 0.0;
    } else {
        // find the XZ angles that bring the Y axis to point to init_pose.p
        Vector axis(pose.p/dist);
        beta = 0.0;
        if (fabs(axis(2)) > 1-KDL::epsilon) {
            // direction is aligned on Z axis, just rotation on X
            alpha = 0.0;
            gamma = KDL::sign(axis(2))*KDL::PI/2;
        } else {
            alpha = -KDL::atan2(axis(0), axis(1));
            gamma = KDL::atan2(axis(2), KDL::sqrt(KDL::sqr(axis(0))+KDL::sqr(axis(1))));
        }
        // rotation after first 2 joints
        basis = Rotation::EulerZYX(alpha, beta, gamma);
        m_chi(0) = alpha;
        m_chi(1) = gamma;
    }
    m_chi(2) = dist;
    basis = basis.Inverse()*pose.M;
    basis.GetEulerZYX(alpha, beta, gamma);
    // alpha = rotation on Z
    // beta = rotation on Y
    // gamma = rotation on X in that order
    // it corresponds to the joint order, so just assign
    m_chi(3) = alpha;
    m_chi(4) = beta;
    m_chi(5) = gamma;
    return true;
}
 
bool Distance::initialise(Frame& init_pose)
{
    // we will initialize m_chi to values that match the pose
    m_externalPose=init_pose;
    computeChi(m_externalPose);
    // get current Jf and update internal pose
    updateJacobian();
    return true;
}
 
bool Distance::closeLoop()
{
    if (!Equal(m_internalPose.Inverse()*m_externalPose,F_identity,m_threshold)){
        computeChi(m_externalPose);
        updateJacobian();
    }
    return true;
}
 
void Distance::initCache(Cache *_cache)
{
    m_cache = _cache;
    m_distCCh = -1;
    if (m_cache) {
        // create one channel for the coordinates
        m_distCCh = m_cache->addChannel(this, "Xf", distanceCacheSize);
        // save initial constraint in cache position 0
        pushDist(0);
    }
}
 
void Distance::pushDist(CacheTS timestamp)
{
    if (m_distCCh >= 0) {
        double *item = (double*)m_cache->addCacheItem(this, m_distCCh, timestamp, NULL, distanceCacheSize);
        if (item) {
            *item++ = m_K;
            *item++ = m_tolerance;
            *item++ = m_yd;
            *item++ = m_yddot;
            *item++ = m_alpha;
            memcpy(item, &m_chi[0], 6*sizeof(e_scalar));
        }
        m_distCTs = timestamp;
    }
}
 
bool Distance::popDist(CacheTS timestamp)
{
    if (m_distCCh >= 0) {
        double *item = (double*)m_cache->getPreviousCacheItem(this, m_distCCh, &timestamp);
        if (item && timestamp != m_distCTs) {
            m_values.feedback = m_K = *item++;
            m_values.tolerance = m_tolerance = *item++;
            m_yd = *item++;
            m_yddot = *item++;
            m_values.alpha = m_alpha = *item++;
            memcpy(&m_chi[0], item, 6*sizeof(e_scalar));
            m_distCTs = timestamp;
            m_Wy(0) = m_alpha/*/(m_tolerance*m_K)*/;
            updateJacobian();
        }
        return (item) ? true : false;
    }
    return true;
}
 
void Distance::pushCache(const Timestamp& timestamp)
{
    if (!timestamp.substep && timestamp.cache)
        pushDist(timestamp.cacheTimestamp);
}
 
void Distance::updateKinematics(const Timestamp& timestamp)
{
    if (timestamp.interpolate) {
        //the internal pose and Jf is already up to date (see model_update)
        //update the desired output based on yddot
        if (timestamp.substep) {
            m_yd += m_yddot*timestamp.realTimestep;
            if (m_yd < KDL::epsilon)
                m_yd = KDL::epsilon;
        } else {
            m_yd = m_nextyd;
            m_yddot = m_nextyddot;
        }
    }
    pushCache(timestamp);
}
 
void Distance::updateJacobian()
{
    for(unsigned int i=0;i<6;i++)
        m_chiKdl[i]=m_chi[i];
 
    m_fksolver->JntToCart(m_chiKdl,m_internalPose);
    m_jacsolver->JntToJac(m_chiKdl,m_jac);
    changeRefPoint(m_jac,-m_internalPose.p,m_jac);
    for(unsigned int i=0;i<6;i++)
        for(unsigned int j=0;j<6;j++)
            m_Jf(i,j)=m_jac(i,j);
}
 
bool Distance::setControlParameters(struct ConstraintValues* _values, unsigned int _nvalues, double timestep)
{
    int action = 0;
    int i;
    ConstraintSingleValue* _data;
 
    while (_nvalues > 0) {
        if (_values->id == ID_DISTANCE) {
            if ((_values->action & ACT_ALPHA) && _values->alpha >= 0.0) {
                m_alpha = _values->alpha;
                action |= ACT_ALPHA;
            }
            if ((_values->action & ACT_TOLERANCE) && _values->tolerance > KDL::epsilon) {
                m_tolerance = _values->tolerance;
                action |= ACT_TOLERANCE;
            }
            if ((_values->action & ACT_FEEDBACK) && _values->feedback > KDL::epsilon) {
                m_K = _values->feedback;
                action |= ACT_FEEDBACK;
            }
            for (_data = _values->values, i=0; i<_values->number; i++, _data++) {
                if (_data->id == ID_DISTANCE) {
                    switch (_data->action & (ACT_VALUE|ACT_VELOCITY)) {
                    case 0:
                        // no indication, keep current values
                        break;
                    case ACT_VELOCITY:
                        // only the velocity is given estimate the new value by integration
                        _data->yd = m_yd+_data->yddot*timestep;
                        // walkthrough for negative value correction
                    case ACT_VALUE:
                        // only the value is given, estimate the velocity from previous value
                        if (_data->yd < KDL::epsilon)
                            _data->yd = KDL::epsilon;
                        m_nextyd = _data->yd;
                        // if the user sets the value, we assume future velocity is zero
                        // (until the user changes the value again)
                        m_nextyddot = (_data->action & ACT_VALUE) ? 0.0 : _data->yddot;
                        if (timestep>0.0) {
                            m_yddot = (_data->yd-m_yd)/timestep;
                        } else {
                            // allow the user to change target instantenously when this function
                            // if called from setControlParameter with timestep = 0
                            m_yddot = m_nextyddot;
                            m_yd = m_nextyd;
                        }
                        break;
                    case (ACT_VALUE|ACT_VELOCITY):
                        // the user should not set the value and velocity at the same time.
                        // In this case, we will assume that he want to set the future value
                        // and we compute the current value to match the velocity
                        if (_data->yd < KDL::epsilon)
                            _data->yd = KDL::epsilon;
                        m_yd = _data->yd - _data->yddot*timestep;
                        if (m_yd < KDL::epsilon)
                            m_yd = KDL::epsilon;
                        m_nextyd = _data->yd;
                        m_nextyddot = _data->yddot;
                        if (timestep>0.0) {
                            m_yddot = (_data->yd-m_yd)/timestep;
                        } else {
                            m_yd = m_nextyd;
                            m_yddot = m_nextyddot;
                        }
                        break;
                    }
                }
            }
        }
        _nvalues--;
        _values++;
    }
    if (action & (ACT_TOLERANCE|ACT_FEEDBACK|ACT_ALPHA)) {
        // recompute the weight
        m_Wy(0) = m_alpha/*/(m_tolerance*m_K)*/;
    }
    return true;
}
 
const ConstraintValues* Distance::getControlParameters(unsigned int* _nvalues)
{
    *(double*)&m_data.y = m_chi(2);
    *(double*)&m_data.ydot = m_ydot(0);
    m_data.yd = m_yd;
    m_data.yddot = m_yddot;
    m_data.action = 0;
    m_values.action = 0;
    if (_nvalues) 
        *_nvalues=1; 
    return &m_values; 
}
 
void Distance::updateControlOutput(const Timestamp& timestamp)
{
    bool cacheAvail = true;
    if (!timestamp.substep) {
        if (!timestamp.reiterate)
            cacheAvail = popDist(timestamp.cacheTimestamp);
    }
    if (m_constraintCallback && (m_substep || (!timestamp.reiterate && !timestamp.substep))) {
        // initialize first callback the application to get the current values
        *(double*)&m_data.y = m_chi(2);
        *(double*)&m_data.ydot = m_ydot(0);
        m_data.yd = m_yd;
        m_data.yddot = m_yddot;
        m_data.action = 0;
        m_values.action = 0;
        if ((*m_constraintCallback)(timestamp, &m_values, 1, m_constraintParam)) {
            setControlParameters(&m_values, 1, timestamp.realTimestep);
        }
    }
    if (!cacheAvail || !timestamp.interpolate) {
        // first position in cache: set the desired output immediately as we cannot interpolate
        m_yd = m_nextyd;
        m_yddot = m_nextyddot;
    }
    double error = m_yd-m_chi(2);
    if (KDL::Norm(error) > m_maxerror)
        error = KDL::sign(error)*m_maxerror;
    m_ydot(0)=m_yddot+m_K*error;
}
 
}