Pull request #256: Fix/zero jacobian calculation

Merge in MOCTRL/libfranka from fix/zero-jacobian-calculation to main

* commit '9e56a6f1ee73e644da38d453c1a49a9ae567803d':
  hotfix/fixes zero Jacobian calculation for robot model

Author: BarisYazici

CHANGELOG.md

@@ -7,6 +7,8 @@ All notable changes to libfranka and pylibfranka will be documented in this file
 ### libfranka - C++
 #### Changed
 - The libfranka library is built with static links - removing the need for dynamic dependencies at runtime
+- Fix the acceleration link addition bug and robot model link parsing [github](https://github.com/frankarobotics/libfranka/issues/213)
+- Update the test urdf with the acceleration links and joint
 
 ### pylibfranka - Python
 #### Added

include/franka/robot_model.h

@@ -228,6 +228,8 @@ class RobotModel : public RobotModelBase {
       const std::array<double, 3>& g_earth,
       std::array<double, 7>& g_ne) const;
 
+  static constexpr const char* kLastLinkName = "link8";
+
   pinocchio::Inertia initial_last_link_inertia_;
   pinocchio::FrameIndex last_link_frame_index_;
   pinocchio::JointIndex last_joint_index_;

src/robot_model.cpp

@@ -8,9 +8,11 @@ namespace franka {
 RobotModel::RobotModel(const std::string& urdf) {
   pinocchio::urdf::buildModelFromXML(urdf, pinocchio_model_);
 
-  last_joint_index_ =                       // NOLINT(cppcoreguidelines-prefer-member-initializer)
-      pinocchio_model_.joints.back().id();  // NOLINT(cppcoreguidelines-prefer-member-initializer)
-  last_link_frame_index_ = pinocchio_model_.getFrameId(pinocchio_model_.frames.back().name);
+  last_link_frame_index_ = pinocchio_model_.getFrameId(kLastLinkName);
+  last_joint_index_ =  // NOLINT(cppcoreguidelines-prefer-member-initializer)
+      pinocchio_model_.frames[last_link_frame_index_]
+          .parentJoint;  // NOLINT(cppcoreguidelines-prefer-member-initializer)
+
   initial_last_link_inertia_ = pinocchio_model_.inertias[last_joint_index_];
 
   cached_f_x_ctotal_.fill(-1.0);