Merge pull request #45 from Simple-Robotics/topic/get_force

Add get force function to extract forces from fulldynamics MPC

Author: EtienneAr

bindings/expose-mpc.cpp

@@ -88,6 +88,7 @@ namespace simple_mpc
         .def("getFootTakeoffCycle", &MPC::getFootTakeoffCycle, ("self"_a, "ee_name"))
         .def("getFootLandCycle", &MPC::getFootLandCycle, ("self"_a, "ee_name"))
         .def("getStateDerivative", &MPC::getStateDerivative, ("self"_a, "t"))
+        .def("getContactForces", &MPC::getContactForces, ("self"_a, "t"))
         .def("getCyclingContactState", &MPC::getCyclingContactState, ("self"_a, "t", "ee_name"))
         .def(
           "getModelHandler", &MPC::getModelHandler, "self"_a, bp::return_internal_reference<>(),

examples/go2_fulldynamics.py

@@ -201,7 +201,7 @@
 L_measured = []
 
 v = np.zeros(6)
-v[0] = 0.
+v[0] = 0.2
 mpc.velocity_base = v
 for t in range(500):
     print("Time " + str(t))
@@ -214,7 +214,6 @@
         str(land_RF) + ", takeoff_LF = " + str(takeoff_LF) + ", landing_LF = ",
         str(land_LF),
     ) """
-
     """ if t == 200:
         for s in range(T):
             device.resetState(mpc.xs[s][:nq])
@@ -238,15 +237,16 @@
     a0 = mpc.getStateDerivative(0)[nv:]
     a1 = mpc.getStateDerivative(1)[nv:]
 
-    FL_f, FR_f, RL_f, RR_f = extract_forces(mpc.getTrajOptProblem(), mpc.solver.workspace, 0)
+    forces_vec0 = mpc.getContactForces(0)
+    forces_vec1 = mpc.getContactForces(1)
     contact_states = mpc.ocp_handler.getContactState(0)
-    total_forces = np.concatenate((FL_f, FR_f, RL_f, RR_f))
-    force_FL.append(FL_f)
-    force_FR.append(FR_f)
-    force_RL.append(RL_f)
-    force_RR.append(RR_f)
 
-    forces = [total_forces, total_forces]
+    force_FL.append(forces_vec0[:3])
+    force_FR.append(forces_vec0[3:6])
+    force_RL.append(forces_vec0[6:9])
+    force_RR.append(forces_vec0[9:12])
+
+    forces = [forces_vec0, forces_vec1]
     ddqs = [a0, a1]
     xss = [mpc.xs[0], mpc.xs[1]]
     uss = [mpc.us[0], mpc.us[1]]

include/simple-mpc/mpc.hpp

@@ -11,6 +11,7 @@
 #include <aligator/fwd.hpp>
 #include <aligator/modelling/dynamics/fwd.hpp>
 #include <aligator/modelling/dynamics/integrator-explicit.hpp>
+#include <aligator/modelling/dynamics/multibody-constraint-fwd.hpp>
 #include <aligator/solvers/proxddp/solver-proxddp.hpp>
 
 #include "simple-mpc/deprecated.hpp"
@@ -22,6 +23,8 @@
 namespace simple_mpc
 {
   using ExplicitIntegratorData = dynamics::ExplicitIntegratorDataTpl<double>;
+  using MultibodyConstraintFwdData = dynamics::MultibodyConstraintFwdDataTpl<double>;
+  using MultibodyConstraintFwdDynamics = dynamics::MultibodyConstraintFwdDynamicsTpl<double>;
 
   struct MPCSettings
   {
@@ -175,13 +178,13 @@ namespace simple_mpc
       }
     }
 
-    const ConstVectorRef getStateDerivative(const std::size_t t)
-    {
-      ExplicitIntegratorData * int_data =
-        dynamic_cast<ExplicitIntegratorData *>(&*solver_->workspace_.problem_data.stage_data[t]->dynamics_data);
-      assert(int_data != nullptr);
-      return int_data->continuous_data->xdot_;
-    }
+    const ConstVectorRef getStateDerivative(const std::size_t t);
+
+    /**
+     * @brief Return contact forces for a full dynamics MPC problem
+     * @warning Only work with fulldynamics OCP handler
+     */
+    const Eigen::VectorXd getContactForces(const std::size_t t);
 
     void switchToWalk(const Vector6d & velocity_base);
 

src/mpc.cpp

@@ -342,6 +342,43 @@ namespace simple_mpc
     return ocp_handler_->getProblem();
   }
 
+  const ConstVectorRef MPC::getStateDerivative(const std::size_t t)
+  {
+    ExplicitIntegratorData * int_data =
+      dynamic_cast<ExplicitIntegratorData *>(&*solver_->workspace_.problem_data.stage_data[t]->dynamics_data);
+    assert(int_data != nullptr);
+    return int_data->continuous_data->xdot_;
+  }
+
+  const Eigen::VectorXd MPC::getContactForces(const std::size_t t)
+  {
+    Eigen::VectorXd contact_forces;
+    contact_forces.resize(3 * (long)ee_names_.size());
+
+    ExplicitIntegratorData * int_data =
+      dynamic_cast<ExplicitIntegratorData *>(&*solver_->workspace_.problem_data.stage_data[t]->dynamics_data);
+    assert(int_data != nullptr);
+    MultibodyConstraintFwdData * mc_data = dynamic_cast<MultibodyConstraintFwdData *>(&*int_data->continuous_data);
+    assert(mc_data != nullptr);
+
+    std::vector<bool> contact_state = ocp_handler_->getContactState(t);
+
+    size_t force_id = 0;
+    for (size_t i = 0; i < contact_state.size(); i++)
+    {
+      if (contact_state[i])
+      {
+        contact_forces.segment((long)i * 3, 3) = mc_data->constraint_datas_[force_id].contact_force.linear();
+        force_id += 1;
+      }
+      else
+      {
+        contact_forces.segment((long)i * 3, 3).setZero();
+      }
+    }
+    return contact_forces;
+  }
+
   void MPC::switchToWalk(const Vector6d & velocity_base)
   {
     now_ = WALKING;

tests/mpc.cpp

@@ -90,6 +90,8 @@ BOOST_AUTO_TEST_CASE(mpc_fulldynamics)
   BOOST_CHECK_EQUAL(mpc.foot_land_times_.at("right_sole_link")[0], 150);
 
   Eigen::VectorXd xdot = mpc.getStateDerivative(0);
+
+  Eigen::VectorXd forces = mpc.getContactForces(0);
 }
 
 BOOST_AUTO_TEST_CASE(mpc_kinodynamics)