NetWrenchObserver.cpp

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/*
 * Copyright (c) 2018-2019, CNRS-UM LIRMM
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
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 * this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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#include <lipm_walking/NetWrenchObserver.h>

namespace lipm_walking
{

NetWrenchObserver::NetWrenchObserver() : sensorNames_({"LeftFootForceSensor", "RightFootForceSensor"}) {}

NetWrenchObserver::NetWrenchObserver(const std::vector<std::string> & sensorNames) : sensorNames_(sensorNames) {}

void NetWrenchObserver::update(const mc_rbdyn::Robot & robot, const Contact & contact)
{
  updateNetWrench(robot);
  updateNetZMP(contact);
}

void NetWrenchObserver::updateNetWrench(const mc_rbdyn::Robot & robot)
{
  netWrench_ = sva::ForceVecd::Zero();
  for(std::string sensorName : sensorNames_)
  {
    const auto & sensor = robot.forceSensor(sensorName);
    if(sensor.force().z() > 1.) // normal force is more than 1 [N]
    {
      netWrench_ += sensor.worldWrench(robot);
    }
  }
}

void NetWrenchObserver::updateNetZMP(const Contact & contact)
{
  const Eigen::Vector3d & force = netWrench_.force();
  const Eigen::Vector3d & moment_0 = netWrench_.couple();
  Eigen::Vector3d moment_p = moment_0 - contact.p().cross(force);
  if(force.dot(force) > 42.) // force norm is more than 5 [N]
  {
    netZMP_ = contact.p() + contact.normal().cross(moment_p) / contact.normal().dot(force);
  }
}

} // namespace lipm_walking