Used the fabs function to compute the velocity of each joint (speed must always be positive).

humanoid_modules/src/joints_cart_module.cpp

@@ -215,7 +215,7 @@ void CJointsCartModule::initialize_action_msg(sensor_msgs::JointState &solution)
       for(j=0;j<this->current_angles.name.size();j++)
       {
         if(this->current_angles.name[j]==this->joints_traj_msg.trajectory.joint_names[i])
-          this->joints_traj_msg.trajectory.points[0].velocities[i]=(this->current_angles.position[j]-this->joints_traj_msg.trajectory.points[0].positions[i])/this->motion_time;
+          this->joints_traj_msg.trajectory.points[0].velocities[i]=fabs(this->current_angles.position[j]-this->joints_traj_msg.trajectory.points[0].positions[i])/this->motion_time;
       }
     }
     this->joint_state_access.exit();