SpaceTimePlanning.cpp

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/* Author: Francesco Grothe */
 
#include <ompl/base/SpaceInformation.h>
#include <ompl/base/spaces/SpaceTimeStateSpace.h>
#include <ompl/geometric/planners/rrt/RRTConnect.h>
#include <ompl/geometric/planners/rrt/STRRTstar.h>
#include <ompl/geometric/SimpleSetup.h>
 
#include <ompl/config.h>
#include <iostream>
 
namespace ob = ompl::base;
namespace og = ompl::geometric;

 
bool isStateValid(const ob::State *state)
{
    // extract the space component of the state and cast it to what we expect
    const auto pos = state->as<ob::CompoundState>()->as<ob::RealVectorStateSpace::StateType>(0)->values[0];
 
    // extract the time component of the state and cast it to what we expect
    const auto t = state->as<ob::CompoundState>()->as<ob::TimeStateSpace::StateType>(1)->position;
 
    // check validity of state defined by pos & t (e.g. check if constraints are satisfied)...
 
    // return a value that is always true
    return t >= 0 && pos < std::numeric_limits<double>::infinity();
}
 
class SpaceTimeMotionValidator : public ob::MotionValidator
{
public:
    explicit SpaceTimeMotionValidator(const ob::SpaceInformationPtr &si)
      : MotionValidator(si)
      , vMax_(si_->getStateSpace().get()->as<ob::SpaceTimeStateSpace>()->getVMax())
      , stateSpace_(si_->getStateSpace().get()) {};
 
    bool checkMotion(const ob::State *s1, const ob::State *s2) const override
    {
        // assume motion starts in a valid configuration, so s1 is valid
        if (!si_->isValid(s2))
        {
            invalid_++;
            return false;
        }
 
        // check if motion is forward in time and is not exceeding the speed limit
        auto *space = stateSpace_->as<ob::SpaceTimeStateSpace>();
        auto deltaPos = space->distanceSpace(s1, s2);
        auto deltaT = s2->as<ob::CompoundState>()->as<ob::TimeStateSpace::StateType>(1)->position -
                      s1->as<ob::CompoundState>()->as<ob::TimeStateSpace::StateType>(1)->position;
 
        if (!(deltaT > 0 && deltaPos / deltaT <= vMax_))
        {
            invalid_++;
            return false;
        }
 
        // check if the path between the states is unconstrained (perform interpolation)...
 
        return true;
    }
 
    bool checkMotion(const ompl::base::State *, const ompl::base::State *,
                     std::pair<ob::State *, double> &) const override
    {
        throw ompl::Exception("SpaceTimeMotionValidator::checkMotion", "not implemented");
    }
 
private:
    double vMax_;                 // maximum velocity
    ob::StateSpace *stateSpace_;  // the animation state space for distance calculation
};
 
void plan(void)
{
    // set maximum velocity
    double vMax = 0.2;
 
    // construct the state space we are planning in
    auto vectorSpace(std::make_shared<ob::RealVectorStateSpace>(1));
    auto space = std::make_shared<ob::SpaceTimeStateSpace>(vectorSpace, vMax);
 
    // set the bounds for R1
    ob::RealVectorBounds bounds(1);
    bounds.setLow(-1.0);
    bounds.setHigh(1.0);
    vectorSpace->setBounds(bounds);
 
    // set time bounds. Planning with unbounded time is also possible when using ST-RRT*.
    space->setTimeBounds(0.0, 10.0);
 
    // create the space information class for the space
    ob::SpaceInformationPtr si = std::make_shared<ob::SpaceInformation>(space);
 
    // set state validity checking for this space
    si->setStateValidityChecker([](const ob::State *state) { return isStateValid(state); });
    si->setMotionValidator(std::make_shared<SpaceTimeMotionValidator>(si));
 
    // define a simple setup class
    og::SimpleSetup ss(si);
 
    // create a start state
    ob::ScopedState<> start(space);
    start[0] = 0;  // pos
 
    // create a goal state
    ob::ScopedState<> goal(space);
    goal[0] = 1;  // pos
 
    // set the start and goal states
    ss.setStartAndGoalStates(start, goal);
 
    // construct the planner
    auto *strrtStar = new og::STRRTstar(si);
 
    // set planner parameters
    strrtStar->setRange(vMax);
 
    // set the used planner
    ss.setPlanner(ob::PlannerPtr(strrtStar));
 
    // attempt to solve the problem within one second of planning time
    ob::PlannerStatus solved = ss.solve(1.0);
 
    if (solved)
    {
        std::cout << "Found solution:" << std::endl;
        // print the path to screen
        ss.getSolutionPath().print(std::cout);
    }
    else
        std::cout << "No solution found" << std::endl;
}
 
int main(int /*argc*/, char ** /*argv*/)
{
    std::cout << "OMPL version: " << OMPL_VERSION << std::endl;
 
    plan();
 
    return 0;
}