RigidBodyPlanningWithIK.cpp

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/* Author: Ioan Sucan */
 
#include <ompl/base/spaces/SE3StateSpace.h>
#include <ompl/geometric/SimpleSetup.h>
#include <ompl/base/goals/GoalLazySamples.h>
#include <ompl/geometric/GeneticSearch.h>
 
#include <ompl/config.h>
#include <iostream>
 
namespace ob = ompl::base;
namespace og = ompl::geometric;
 
// describe an arbitrary representation of a goal region in SE(3)
class MyGoalRegion : public ob::GoalRegion
{
public:
 
    MyGoalRegion(const ob::SpaceInformationPtr &si) : ob::GoalRegion(si)
    {
        setThreshold(1e-2);
    }
 
    double distanceGoal(const ob::State *state) const override
    {
        // goal region is given by states where x + y = z and orientation is close to identity
        double d = fabs(state->as<ob::SE3StateSpace::StateType>()->getX()
                        + state->as<ob::SE3StateSpace::StateType>()->getY()
                        - state->as<ob::SE3StateSpace::StateType>()->getZ())
            + fabs(state->as<ob::SE3StateSpace::StateType>()->rotation().w - 1.0);
        return d;
    }
 
};
 
// Goal regions such as the one above cannot be sampled, so
// bi-directional trees cannot be used for solving. However, we can
// transform such goal regions into ones that can be sampled. The
// caveat is that it should be possible to find states in this region
// with some other algorithm. Genetic algorithms that essentially
// perform inverse kinematics in the general sense can be used:
 
bool regionSamplingWithGS(const ob::SpaceInformationPtr &si, const ob::ProblemDefinitionPtr &pd, const ob::GoalRegion *region, const ob::GoalLazySamples *gls, ob::State *result)
{
    og::GeneticSearch g(si);
 
    // we can use a larger time duration for solve(), but we want to demo the ability
    // of GeneticSearch to continue from where it left off
    bool cont = false;
    for (int i = 0 ; i < 100 ; ++i)
        if (g.solve(0.05, *region, result))
        {
            cont = true;
            break;
        }
 
    if (cont)
    {
        std::cout << "Found goal state: " << std::endl;
        si->printState(result);
    }
 
    // we continue sampling while we are able to find solutions, we have found not more than 2 previous solutions and we have not yet solved the problem
    return cont && gls->maxSampleCount() < 3 && !pd->hasSolution();
}
 
void planWithIK()
{
    // construct the state space we are planning in
    auto space(std::make_shared<ob::SE3StateSpace>());
 
    // set the bounds for the R^3 part of SE(3)
    ob::RealVectorBounds bounds(3);
    bounds.setLow(-1);
    bounds.setHigh(1);
 
    space->setBounds(bounds);
 
    // define a simple setup class
    og::SimpleSetup ss(space);
 
    // create a random start state
    ob::ScopedState<ob::SE3StateSpace> start(space);
    start->setXYZ(0, 0, 0);
    start->rotation().setIdentity();
    ss.addStartState(start);
 
    // define our goal region
    MyGoalRegion region(ss.getSpaceInformation());
 
    // bind a sampling function that fills its argument with a sampled state
    // and returns true while it can produce new samples we don't need to
    // check if new samples are different from ones previously computed as
    // this is pefromed automatically by GoalLazySamples
    ob::GoalSamplingFn samplingFunction = [&ss, &region](const ob::GoalLazySamples *gls, ob::State *result)
        {
            return regionSamplingWithGS(ss.getSpaceInformation(), ss.getProblemDefinition(), &region,
                gls, result);
        };
 
    // create an instance of GoalLazySamples:
    auto goal(std::make_shared<ob::GoalLazySamples>(ss.getSpaceInformation(), samplingFunction));
 
    // we set a goal that is sampleable, but it in fact corresponds to a region that is not sampleable by default
    ss.setGoal(goal);
 
    // attempt to solve the problem
    ob::PlannerStatus solved = ss.solve(3.0);
 
    if (solved)
    {
        std::cout << "Found solution:" << std::endl;
        // print the path to screen
        ss.simplifySolution();
        ss.getSolutionPath().print(std::cout);
    }
    else
        std::cout << "No solution found" << std::endl;
 
    // the region variable will now go out of scope. To make sure it is not used in the sampling function any more
    // (i.e., the sampling thread was able to terminate), we make sure sampling has terminated
    goal->as<ob::GoalLazySamples>()->stopSampling();
}
 
int main(int /*argc*/, char ** /*argv*/)
{
    std::cout << "OMPL version: " << OMPL_VERSION << std::endl;
 
    planWithIK();
 
    return 0;
}