ilqr_solver.h

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#ifndef EXOTICA_ILQR_SOLVER_ILQR_SOLVER_H_
#define EXOTICA_ILQR_SOLVER_ILQR_SOLVER_H_

#include <exotica_core/feedback_motion_solver.h>
#include <exotica_core/problems/dynamic_time_indexed_shooting_problem.h>
#include <exotica_core/server.h>

#include <exotica_ilqr_solver/ilqr_solver_initializer.h>

namespace exotica
{
// This code is based on:
// W. Li, E. Todorov, Iterative Linear Quadratic Regulator Design for Nonlinear Biological Movement Systems
// https://homes.cs.washington.edu/~todorov/papers/LiICINCO04.pdf
class ILQRSolver : public FeedbackMotionSolver, public Instantiable<ILQRSolverInitializer>
{
public:
    void Solve(Eigen::MatrixXd& solution) override;

    void SpecifyProblem(PlanningProblemPtr pointer) override;

    Eigen::VectorXd GetFeedbackControl(Eigen::VectorXdRefConst x, int t) const override;

private:
    DynamicTimeIndexedShootingProblemPtr prob_;                              
    DynamicsSolverPtr dynamics_solver_;                                      
    std::vector<Eigen::MatrixXd> K_gains_, Ku_gains_, Kv_gains_, vk_gains_;  

    Eigen::MatrixXd best_ref_x_, best_ref_u_;  

    void BackwardPass();

    double ForwardPass(const double alpha, Eigen::MatrixXdRefConst ref_x, Eigen::MatrixXdRefConst ref_u);
};
}  // namespace exotica

#endif  // EXOTICA_ILQR_SOLVER_ILQR_SOLVER_H_