119 lines
3.8 KiB
C++
119 lines
3.8 KiB
C++
/*
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* Copyright (C) 2012 Open Source Robotics Foundation
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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*/
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#include "gazebo/physics/physics.hh"
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#include "gazebo/transport/transport.hh"
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#include "plugins/DiffDrivePlugin.hh"
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using namespace gazebo;
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GZ_REGISTER_MODEL_PLUGIN(DiffDrivePlugin)
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enum {RIGHT, LEFT};
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/////////////////////////////////////////////////
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DiffDrivePlugin::DiffDrivePlugin()
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{
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this->wheelSpeed[LEFT] = this->wheelSpeed[RIGHT] = 0;
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this->wheelSeparation = 1.0;
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this->wheelRadius = 1.0;
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}
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/////////////////////////////////////////////////
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void DiffDrivePlugin::Load(physics::ModelPtr _model,
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sdf::ElementPtr _sdf)
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{
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this->model = _model;
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this->node = transport::NodePtr(new transport::Node());
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this->node->Init(this->model->GetWorld()->GetName());
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this->velSub = this->node->Subscribe(std::string("~/") +
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this->model->GetName() + "/vel_cmd", &DiffDrivePlugin::OnVelMsg, this);
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if (!_sdf->HasElement("left_joint"))
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gzerr << "DiffDrive plugin missing <left_joint> element\n";
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if (!_sdf->HasElement("right_joint"))
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gzerr << "DiffDrive plugin missing <right_joint> element\n";
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this->leftJoint = _model->GetJoint(
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_sdf->GetElement("left_joint")->Get<std::string>());
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this->rightJoint = _model->GetJoint(
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_sdf->GetElement("right_joint")->Get<std::string>());
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if (!this->leftJoint)
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gzerr << "Unable to find left joint["
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<< _sdf->GetElement("left_joint")->Get<std::string>() << "]\n";
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if (!this->rightJoint)
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gzerr << "Unable to find right joint["
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<< _sdf->GetElement("right_joint")->Get<std::string>() << "]\n";
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this->updateConnection = event::Events::ConnectWorldUpdateBegin(
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boost::bind(&DiffDrivePlugin::OnUpdate, this));
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}
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/////////////////////////////////////////////////
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void DiffDrivePlugin::Init()
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{
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this->wheelSeparation = this->leftJoint->GetAnchor(0).Distance(
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this->rightJoint->GetAnchor(0));
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physics::EntityPtr parent = boost::dynamic_pointer_cast<physics::Entity>(
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this->leftJoint->GetChild());
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math::Box bb = parent->GetBoundingBox();
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// This assumes that the largest dimension of the wheel is the diameter
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this->wheelRadius = bb.GetSize().GetMax() * 0.5;
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}
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/////////////////////////////////////////////////
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void DiffDrivePlugin::OnVelMsg(ConstPosePtr &_msg)
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{
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double vr, va;
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vr = _msg->position().x();
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va = msgs::ConvertIgn(_msg->orientation()).Euler().Z();
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this->wheelSpeed[LEFT] = vr + va * this->wheelSeparation / 2.0;
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this->wheelSpeed[RIGHT] = vr - va * this->wheelSeparation / 2.0;
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}
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/////////////////////////////////////////////////
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void DiffDrivePlugin::OnUpdate()
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{
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/* double d1, d2;
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double dr, da;
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this->prevUpdateTime = currTime;
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// Distance travelled by front wheels
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d1 = stepTime.Double() * this->wheelRadius * this->leftJoint->GetVelocity(0);
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d2 = stepTime.Double() * this->wheelRadius * this->rightJoint->GetVelocity(0);
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dr = (d1 + d2) / 2;
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da = (d1 - d2) / this->wheelSeparation;
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common::Time currTime = this->model->GetWorld()->GetSimTime();
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common::Time stepTime = currTime - this->prevUpdateTime;
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*/
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double leftVelDesired = (this->wheelSpeed[LEFT] / this->wheelRadius);
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double rightVelDesired = (this->wheelSpeed[RIGHT] / this->wheelRadius);
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this->leftJoint->SetVelocity(0, leftVelDesired);
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this->rightJoint->SetVelocity(0, rightVelDesired);
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}
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