mirror of
https://github.com/bulletphysics/bullet3
synced 2024-12-15 06:00:12 +00:00
362 lines
11 KiB
C++
362 lines
11 KiB
C++
#include "invdyn_bullet_comparison.hpp"
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#include <cmath>
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#include "BulletInverseDynamics/IDConfig.hpp"
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#include "BulletInverseDynamics/MultiBodyTree.hpp"
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#include "btBulletDynamicsCommon.h"
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#include "BulletDynamics/Featherstone/btMultiBodyConstraintSolver.h"
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#include "BulletDynamics/Featherstone/btMultiBodyDynamicsWorld.h"
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#include "BulletDynamics/Featherstone/btMultiBodyLinkCollider.h"
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#include "BulletDynamics/Featherstone/btMultiBodyPoint2Point.h"
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namespace btInverseDynamics
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{
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int compareInverseAndForwardDynamics(vecx &q, vecx &u, vecx &dot_u, btVector3 &gravity, bool verbose,
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btMultiBody *btmb, MultiBodyTree *id_tree, double *pos_error,
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double *acc_error)
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{
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// call function and return -1 if it does, printing an bt_id_error_message
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#define RETURN_ON_FAILURE(x) \
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do \
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{ \
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if (-1 == x) \
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{ \
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bt_id_error_message("calling " #x "\n"); \
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return -1; \
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} \
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} while (0)
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if (verbose)
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{
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printf("\n ===================================== \n");
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}
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vecx joint_forces(q.size());
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// set positions and velocities for btMultiBody
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// base link
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mat33 world_T_base;
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vec3 world_pos_base;
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btTransform base_transform;
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vec3 base_velocity;
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vec3 base_angular_velocity;
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RETURN_ON_FAILURE(id_tree->setGravityInWorldFrame(gravity));
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RETURN_ON_FAILURE(id_tree->getBodyOrigin(0, &world_pos_base));
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RETURN_ON_FAILURE(id_tree->getBodyTransform(0, &world_T_base));
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RETURN_ON_FAILURE(id_tree->getBodyAngularVelocity(0, &base_angular_velocity));
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RETURN_ON_FAILURE(id_tree->getBodyLinearVelocityCoM(0, &base_velocity));
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base_transform.setBasis(world_T_base);
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base_transform.setOrigin(world_pos_base);
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btmb->setBaseWorldTransform(base_transform);
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btmb->setBaseOmega(base_angular_velocity);
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btmb->setBaseVel(base_velocity);
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btmb->setLinearDamping(0);
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btmb->setAngularDamping(0);
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// remaining links
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int q_index;
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if (btmb->hasFixedBase())
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{
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q_index = 0;
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}
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else
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{
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q_index = 6;
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}
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if (verbose)
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{
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printf("bt:num_links= %d, num_dofs= %d\n", btmb->getNumLinks(), btmb->getNumDofs());
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}
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for (int l = 0; l < btmb->getNumLinks(); l++)
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{
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const btMultibodyLink &link = btmb->getLink(l);
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if (verbose)
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{
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printf("link %d, pos_var_count= %d, dof_count= %d\n", l, link.m_posVarCount,
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link.m_dofCount);
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}
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if (link.m_posVarCount == 1)
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{
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btmb->setJointPosMultiDof(l, &q(q_index));
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btmb->setJointVelMultiDof(l, &u(q_index));
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if (verbose)
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{
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printf("set q[%d]= %f, u[%d]= %f\n", q_index, q(q_index), q_index, u(q_index));
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}
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q_index++;
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}
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}
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// sanity check
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if (q_index != q.size())
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{
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bt_id_error_message("error in number of dofs for btMultibody and MultiBodyTree\n");
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return -1;
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}
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// run inverse dynamics to determine joint_forces for given q, u, dot_u
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if (-1 == id_tree->calculateInverseDynamics(q, u, dot_u, &joint_forces))
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{
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bt_id_error_message("calculating inverse dynamics\n");
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return -1;
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}
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// set up bullet forward dynamics model
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btScalar dt = 0;
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btAlignedObjectArray<btScalar> scratch_r;
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btAlignedObjectArray<btVector3> scratch_v;
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btAlignedObjectArray<btMatrix3x3> scratch_m;
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// this triggers switch between using either appliedConstraintForce or appliedForce
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bool isConstraintPass = false;
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// apply gravity forces for btMultiBody model. Must be done manually.
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btmb->addBaseForce(btmb->getBaseMass() * gravity);
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for (int link = 0; link < btmb->getNumLinks(); link++)
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{
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btmb->addLinkForce(link, gravity * btmb->getLinkMass(link));
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if (verbose)
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{
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printf("link %d, applying gravity %f %f %f\n", link,
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gravity[0] * btmb->getLinkMass(link), gravity[1] * btmb->getLinkMass(link),
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gravity[2] * btmb->getLinkMass(link));
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}
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}
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// apply generalized forces
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if (btmb->hasFixedBase())
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{
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q_index = 0;
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}
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else
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{
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vec3 base_force;
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base_force(0) = joint_forces(3);
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base_force(1) = joint_forces(4);
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base_force(2) = joint_forces(5);
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vec3 base_moment;
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base_moment(0) = joint_forces(0);
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base_moment(1) = joint_forces(1);
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base_moment(2) = joint_forces(2);
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btmb->addBaseForce(world_T_base * base_force);
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btmb->addBaseTorque(world_T_base * base_moment);
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if (verbose)
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{
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printf("base force from id: %f %f %f\n", joint_forces(3), joint_forces(4),
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joint_forces(5));
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printf("base moment from id: %f %f %f\n", joint_forces(0), joint_forces(1),
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joint_forces(2));
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}
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q_index = 6;
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}
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for (int l = 0; l < btmb->getNumLinks(); l++)
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{
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const btMultibodyLink &link = btmb->getLink(l);
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if (link.m_posVarCount == 1)
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{
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if (verbose)
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{
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printf("id:joint_force[%d]= %f, applied to link %d\n", q_index,
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joint_forces(q_index), l);
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}
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btmb->addJointTorque(l, joint_forces(q_index));
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q_index++;
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}
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}
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// sanity check
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if (q_index != q.size())
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{
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bt_id_error_message("error in number of dofs for btMultibody and MultiBodyTree\n");
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return -1;
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}
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// run forward kinematics & forward dynamics
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btAlignedObjectArray<btQuaternion> world_to_local;
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btAlignedObjectArray<btVector3> local_origin;
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btmb->forwardKinematics(world_to_local, local_origin);
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btmb->computeAccelerationsArticulatedBodyAlgorithmMultiDof(dt, scratch_r, scratch_v, scratch_m, isConstraintPass, false, false);
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// read generalized accelerations back from btMultiBody
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// the mapping from scratch variables to accelerations is taken from the implementation
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// of stepVelocitiesMultiDof
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btScalar *base_accel = &scratch_r[btmb->getNumDofs()];
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btScalar *joint_accel = base_accel + 6;
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*acc_error = 0;
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int dot_u_offset = 0;
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if (btmb->hasFixedBase())
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{
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dot_u_offset = 0;
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}
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else
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{
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dot_u_offset = 6;
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}
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if (true == btmb->hasFixedBase())
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{
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for (int i = 0; i < btmb->getNumDofs(); i++)
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{
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if (verbose)
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{
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printf("bt:ddot_q[%d]= %f, id:ddot_q= %e, diff= %e\n", i, joint_accel[i],
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dot_u(i + dot_u_offset), joint_accel[i] - dot_u(i));
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}
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*acc_error += BT_ID_POW(joint_accel[i] - dot_u(i + dot_u_offset), 2);
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}
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}
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else
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{
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vec3 base_dot_omega;
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vec3 world_dot_omega;
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world_dot_omega(0) = base_accel[0];
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world_dot_omega(1) = base_accel[1];
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world_dot_omega(2) = base_accel[2];
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base_dot_omega = world_T_base.transpose() * world_dot_omega;
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// com happens to coincide with link origin here. If that changes, we need to calculate
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// ddot_com
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vec3 base_ddot_com;
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vec3 world_ddot_com;
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world_ddot_com(0) = base_accel[3];
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world_ddot_com(1) = base_accel[4];
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world_ddot_com(2) = base_accel[5];
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base_ddot_com = world_T_base.transpose() * world_ddot_com;
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for (int i = 0; i < 3; i++)
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{
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if (verbose)
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{
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printf("bt::base_dot_omega(%d)= %e dot_u[%d]= %e, diff= %e\n", i, base_dot_omega(i),
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i, dot_u[i], base_dot_omega(i) - dot_u[i]);
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}
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*acc_error += BT_ID_POW(base_dot_omega(i) - dot_u(i), 2);
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}
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for (int i = 0; i < 3; i++)
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{
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if (verbose)
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{
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printf("bt::base_ddot_com(%d)= %e dot_u[%d]= %e, diff= %e\n", i, base_ddot_com(i),
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i, dot_u[i + 3], base_ddot_com(i) - dot_u[i + 3]);
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}
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*acc_error += BT_ID_POW(base_ddot_com(i) - dot_u(i + 3), 2);
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}
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for (int i = 0; i < btmb->getNumDofs(); i++)
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{
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if (verbose)
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{
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printf("bt:ddot_q[%d]= %f, id:ddot_q= %e, diff= %e\n", i, joint_accel[i],
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dot_u(i + 6), joint_accel[i] - dot_u(i + 6));
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}
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*acc_error += BT_ID_POW(joint_accel[i] - dot_u(i + 6), 2);
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}
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}
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*acc_error = std::sqrt(*acc_error);
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if (verbose)
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{
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printf("======dynamics-err: %e\n", *acc_error);
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}
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*pos_error = 0.0;
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{
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mat33 world_T_body;
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if (-1 == id_tree->getBodyTransform(0, &world_T_body))
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{
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bt_id_error_message("getting transform for body %d\n", 0);
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return -1;
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}
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vec3 world_com;
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if (-1 == id_tree->getBodyCoM(0, &world_com))
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{
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bt_id_error_message("getting com for body %d\n", 0);
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return -1;
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}
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if (verbose)
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{
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printf("id:com: %f %f %f\n", world_com(0), world_com(1), world_com(2));
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printf(
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"id:transform: %f %f %f\n"
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" %f %f %f\n"
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" %f %f %f\n",
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world_T_body(0, 0), world_T_body(0, 1), world_T_body(0, 2), world_T_body(1, 0),
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world_T_body(1, 1), world_T_body(1, 2), world_T_body(2, 0), world_T_body(2, 1),
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world_T_body(2, 2));
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}
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}
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for (int l = 0; l < btmb->getNumLinks(); l++)
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{
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const btMultibodyLink &bt_link = btmb->getLink(l);
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vec3 bt_origin = bt_link.m_cachedWorldTransform.getOrigin();
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mat33 bt_basis = bt_link.m_cachedWorldTransform.getBasis();
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if (verbose)
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{
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printf("------------- link %d\n", l + 1);
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printf("bt:com: %f %f %f\n", bt_origin(0), bt_origin(1), bt_origin(2));
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printf(
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"bt:transform: %f %f %f\n"
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" %f %f %f\n"
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" %f %f %f\n",
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bt_basis(0, 0), bt_basis(0, 1), bt_basis(0, 2), bt_basis(1, 0), bt_basis(1, 1),
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bt_basis(1, 2), bt_basis(2, 0), bt_basis(2, 1), bt_basis(2, 2));
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}
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mat33 id_world_T_body;
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vec3 id_world_com;
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if (-1 == id_tree->getBodyTransform(l + 1, &id_world_T_body))
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{
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bt_id_error_message("getting transform for body %d\n", l);
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return -1;
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}
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if (-1 == id_tree->getBodyCoM(l + 1, &id_world_com))
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{
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bt_id_error_message("getting com for body %d\n", l);
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return -1;
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}
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if (verbose)
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{
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printf("id:com: %f %f %f\n", id_world_com(0), id_world_com(1), id_world_com(2));
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printf(
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"id:transform: %f %f %f\n"
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" %f %f %f\n"
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" %f %f %f\n",
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id_world_T_body(0, 0), id_world_T_body(0, 1), id_world_T_body(0, 2),
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id_world_T_body(1, 0), id_world_T_body(1, 1), id_world_T_body(1, 2),
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id_world_T_body(2, 0), id_world_T_body(2, 1), id_world_T_body(2, 2));
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}
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vec3 diff_com = bt_origin - id_world_com;
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mat33 diff_basis = bt_basis - id_world_T_body;
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if (verbose)
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{
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printf("diff-com: %e %e %e\n", diff_com(0), diff_com(1), diff_com(2));
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printf("diff-transform: %e %e %e %e %e %e %e %e %e\n", diff_basis(0, 0),
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diff_basis(0, 1), diff_basis(0, 2), diff_basis(1, 0), diff_basis(1, 1),
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diff_basis(1, 2), diff_basis(2, 0), diff_basis(2, 1), diff_basis(2, 2));
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}
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double total_pos_err =
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BT_ID_SQRT(BT_ID_POW(diff_com(0), 2) + BT_ID_POW(diff_com(1), 2) +
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BT_ID_POW(diff_com(2), 2) + BT_ID_POW(diff_basis(0, 0), 2) +
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BT_ID_POW(diff_basis(0, 1), 2) + BT_ID_POW(diff_basis(0, 2), 2) +
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BT_ID_POW(diff_basis(1, 0), 2) + BT_ID_POW(diff_basis(1, 1), 2) +
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BT_ID_POW(diff_basis(1, 2), 2) + BT_ID_POW(diff_basis(2, 0), 2) +
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BT_ID_POW(diff_basis(2, 1), 2) + BT_ID_POW(diff_basis(2, 2), 2));
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if (verbose)
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{
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printf("======kin-pos-err: %e\n", total_pos_err);
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}
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if (total_pos_err > *pos_error)
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{
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*pos_error = total_pos_err;
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}
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}
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return 0;
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}
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} // namespace btInverseDynamics
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