[Feature] Export chainable state interfaces from chainable controllers

controller_interface/include/controller_interface/chainable_controller_interface.hpp

@@ -55,6 +55,9 @@ class ChainableControllerInterface : public ControllerInterfaceBase
   CONTROLLER_INTERFACE_PUBLIC
   bool is_chainable() const final;
 
+  CONTROLLER_INTERFACE_PUBLIC
+  std::vector<hardware_interface::StateInterface> export_state_interfaces() final;
+
   CONTROLLER_INTERFACE_PUBLIC
   std::vector<hardware_interface::CommandInterface> export_reference_interfaces() final;
 
@@ -65,8 +68,19 @@ class ChainableControllerInterface : public ControllerInterfaceBase
   bool is_in_chained_mode() const final;
 
 protected:
-  /// Virtual method that each chainable controller should implement to export its chainable
-  /// interfaces.
+  /// Virtual method that each chainable controller should implement to export its read-only
+  /// chainable interfaces.
+  /**
+   * Each chainable controller implements this methods where all its state(read only) interfaces are
+   * exported. The method has the same meaning as `export_state_interfaces` method from
+   * hardware_interface::SystemInterface or hardware_interface::ActuatorInterface.
+   *
+   * \returns list of StateInterfaces that other controller can use as their inputs.
+   */
+  virtual std::vector<hardware_interface::StateInterface> on_export_state_interfaces() = 0;
+
+  /// Virtual method that each chainable controller should implement to export its read/write
+  /// chainable interfaces.
   /**
    * Each chainable controller implements this methods where all input (command) interfaces are
    * exported. The method has the same meaning as `export_command_interface` method from
@@ -114,6 +128,9 @@ class ChainableControllerInterface : public ControllerInterfaceBase
   virtual return_type update_and_write_commands(
     const rclcpp::Time & time, const rclcpp::Duration & period) = 0;
 
+  /// Storage of values for state interfaces
+  std::vector<double> state_interfaces_values_;
+
   /// Storage of values for reference interfaces
   std::vector<double> reference_interfaces_;
 

controller_interface/include/controller_interface/controller_interface.hpp

@@ -42,6 +42,14 @@ class ControllerInterface : public controller_interface::ControllerInterfaceBase
   CONTROLLER_INTERFACE_PUBLIC
   bool is_chainable() const final;
 
+  /**
+   * A non-chainable controller doesn't export any state interfaces.
+   *
+   * \returns empty list.
+   */
+  CONTROLLER_INTERFACE_PUBLIC
+  std::vector<hardware_interface::StateInterface> export_state_interfaces() final;
+
   /**
    * Controller has no reference interfaces.
    *

controller_interface/include/controller_interface/controller_interface_base.hpp

@@ -224,11 +224,20 @@ class ControllerInterfaceBase : public rclcpp_lifecycle::node_interfaces::Lifecy
   CONTROLLER_INTERFACE_PUBLIC
   virtual std::vector<hardware_interface::CommandInterface> export_reference_interfaces() = 0;
 
+  /**
+   * Export interfaces for a chainable controller that can be used as state interface by other
+   * controllers.
+   *
+   * \returns list of state interfaces for preceding controllers.
+   */
+  CONTROLLER_INTERFACE_PUBLIC
+  virtual std::vector<hardware_interface::StateInterface> export_state_interfaces() = 0;
+
   /**
    * Set chained mode of a chainable controller. This method triggers internal processes to switch
    * a chainable controller to "chained" mode and vice-versa. Setting controller to "chained" mode
-   * usually involves disabling of subscribers and other external interfaces to avoid potential
-   * concurrency in input commands.
+   * usually involves the usage of the controller's reference or state interfaces by the other
+   * controllers
    *
    * \returns true if mode is switched successfully and false if not.
    */

controller_interface/src/chainable_controller_interface.cpp

@@ -44,6 +44,42 @@ return_type ChainableControllerInterface::update(
   return ret;
 }
 
+std::vector<hardware_interface::StateInterface>
+ChainableControllerInterface::export_state_interfaces()
+{
+  auto state_interfaces = on_export_state_interfaces();
+  // check if the "state_interfaces_values_" variable is resized to number of interfaces
+  if (state_interfaces_values_.size() != state_interfaces.size())
+  {
+    RCLCPP_FATAL(
+      get_node()->get_logger(),
+      "The internal storage for exported state values 'state_interfaces_values_' variable has size "
+      "'%zu', but it is expected to have the size '%zu' equal to the number of exported state "
+      "interfaces. No state interface will be exported. Please correct and recompile "
+      "the controller with name '%s' and try again.",
+      state_interfaces_values_.size(), state_interfaces.size(), get_node()->get_name());
+    state_interfaces.clear();
+  }
+
+  // check if the names of the controller state interfaces begin with the controller's name
+  for (const auto & interface : state_interfaces)
+  {
+    if (interface.get_prefix_name() != get_node()->get_name())
+    {
+      RCLCPP_FATAL(
+        get_node()->get_logger(),
+        "The name of the interface '%s' does not begin with the controller's name. This is "
+        "mandatory for state interfaces. No state interface will be exported. Please "
+        "correct and recompile the controller with name '%s' and try again.",
+        interface.get_name().c_str(), get_node()->get_name());
+      state_interfaces.clear();
+      break;
+    }
+  }
+
+  return state_interfaces;
+}
+
 std::vector<hardware_interface::CommandInterface>
 ChainableControllerInterface::export_reference_interfaces()
 {

controller_interface/src/controller_interface.cpp

@@ -28,6 +28,11 @@ ControllerInterface::ControllerInterface() : ControllerInterfaceBase() {}
 
 bool ControllerInterface::is_chainable() const { return false; }
 
+std::vector<hardware_interface::StateInterface> ControllerInterface::export_state_interfaces()
+{
+  return {};
+}
+
 std::vector<hardware_interface::CommandInterface> ControllerInterface::export_reference_interfaces()
 {
   return {};

controller_interface/test/test_chainable_controller_interface.cpp

@@ -16,6 +16,9 @@
 
 #include <gmock/gmock.h>
 
+using ::testing::IsEmpty;
+using ::testing::SizeIs;
+
 TEST_F(ChainableControllerInterfaceTest, default_returns)
 {
   TestableChainableControllerInterface controller;
@@ -31,6 +34,26 @@ TEST_F(ChainableControllerInterfaceTest, default_returns)
   EXPECT_FALSE(controller.is_in_chained_mode());
 }
 
+TEST_F(ChainableControllerInterfaceTest, export_state_interfaces)
+{
+  TestableChainableControllerInterface controller;
+
+  // initialize, create node
+  const auto node_options = controller.define_custom_node_options();
+  ASSERT_EQ(
+    controller.init(TEST_CONTROLLER_NAME, "", 50.0, "", node_options),
+    controller_interface::return_type::OK);
+  ASSERT_NO_THROW(controller.get_node());
+
+  auto exported_state_interfaces = controller.export_state_interfaces();
+
+  ASSERT_THAT(exported_state_interfaces, SizeIs(1));
+  EXPECT_EQ(exported_state_interfaces[0].get_prefix_name(), TEST_CONTROLLER_NAME);
+  EXPECT_EQ(exported_state_interfaces[0].get_interface_name(), "test_state");
+
+  EXPECT_EQ(exported_state_interfaces[0].get_value(), EXPORTED_STATE_INTERFACE_VALUE);
+}
+
 TEST_F(ChainableControllerInterfaceTest, export_reference_interfaces)
 {
   TestableChainableControllerInterface controller;
@@ -44,14 +67,14 @@ TEST_F(ChainableControllerInterfaceTest, export_reference_interfaces)
 
   auto reference_interfaces = controller.export_reference_interfaces();
 
-  ASSERT_EQ(reference_interfaces.size(), 1u);
+  ASSERT_THAT(reference_interfaces, SizeIs(1));
   EXPECT_EQ(reference_interfaces[0].get_prefix_name(), TEST_CONTROLLER_NAME);
   EXPECT_EQ(reference_interfaces[0].get_interface_name(), "test_itf");
 
   EXPECT_EQ(reference_interfaces[0].get_value(), INTERFACE_VALUE);
 }
 
-TEST_F(ChainableControllerInterfaceTest, reference_interfaces_storage_not_correct_size)
+TEST_F(ChainableControllerInterfaceTest, interfaces_storage_not_correct_size)
 {
   TestableChainableControllerInterface controller;
 
@@ -65,10 +88,14 @@ TEST_F(ChainableControllerInterfaceTest, reference_interfaces_storage_not_correc
   // expect empty return because storage is not resized
   controller.reference_interfaces_.clear();
   auto reference_interfaces = controller.export_reference_interfaces();
-  ASSERT_TRUE(reference_interfaces.empty());
+  ASSERT_THAT(reference_interfaces, IsEmpty());
+  // expect empty return because storage is not resized
+  controller.state_interfaces_values_.clear();
+  auto exported_state_interfaces = controller.export_state_interfaces();
+  ASSERT_THAT(exported_state_interfaces, IsEmpty());
 }
 
-TEST_F(ChainableControllerInterfaceTest, reference_interfaces_prefix_is_not_node_name)
+TEST_F(ChainableControllerInterfaceTest, interfaces_prefix_is_not_node_name)
 {
   TestableChainableControllerInterface controller;
 
@@ -83,7 +110,10 @@ TEST_F(ChainableControllerInterfaceTest, reference_interfaces_prefix_is_not_node
 
   // expect empty return because interface prefix is not equal to the node name
   auto reference_interfaces = controller.export_reference_interfaces();
-  ASSERT_TRUE(reference_interfaces.empty());
+  ASSERT_THAT(reference_interfaces, IsEmpty());
+  // expect empty return because interface prefix is not equal to the node name
+  auto exported_state_interfaces = controller.export_state_interfaces();
+  ASSERT_THAT(exported_state_interfaces, IsEmpty());
 }
 
 TEST_F(ChainableControllerInterfaceTest, setting_chained_mode)
@@ -98,12 +128,15 @@ TEST_F(ChainableControllerInterfaceTest, setting_chained_mode)
   ASSERT_NO_THROW(controller.get_node());
 
   auto reference_interfaces = controller.export_reference_interfaces();
-  ASSERT_EQ(reference_interfaces.size(), 1u);
+  ASSERT_THAT(reference_interfaces, SizeIs(1));
+  auto exported_state_interfaces = controller.export_state_interfaces();
+  ASSERT_THAT(exported_state_interfaces, SizeIs(1));
 
   EXPECT_FALSE(controller.is_in_chained_mode());
 
   // Fail setting chained mode
   EXPECT_EQ(reference_interfaces[0].get_value(), INTERFACE_VALUE);
+  EXPECT_EQ(exported_state_interfaces[0].get_value(), EXPORTED_STATE_INTERFACE_VALUE);
 
   EXPECT_FALSE(controller.set_chained_mode(true));
   EXPECT_FALSE(controller.is_in_chained_mode());
@@ -116,6 +149,7 @@ TEST_F(ChainableControllerInterfaceTest, setting_chained_mode)
 
   EXPECT_TRUE(controller.set_chained_mode(true));
   EXPECT_TRUE(controller.is_in_chained_mode());
+  EXPECT_EQ(exported_state_interfaces[0].get_value(), EXPORTED_STATE_INTERFACE_VALUE_IN_CHAINMODE);
 
   controller.configure();
   EXPECT_TRUE(controller.set_chained_mode(false));
@@ -147,27 +181,31 @@ TEST_F(ChainableControllerInterfaceTest, test_update_logic)
     controller_interface::return_type::OK);
   ASSERT_NO_THROW(controller.get_node());
 
+  EXPECT_FALSE(controller.set_chained_mode(false));
   EXPECT_FALSE(controller.is_in_chained_mode());
 
   // call update and update it from subscriber because not in chained mode
   ASSERT_EQ(
     controller.update(rclcpp::Time(0), rclcpp::Duration::from_seconds(0.01)),
     controller_interface::return_type::OK);
   ASSERT_EQ(controller.reference_interfaces_[0], INTERFACE_VALUE_INITIAL_REF - 1);
+  ASSERT_EQ(controller.state_interfaces_values_[0], EXPORTED_STATE_INTERFACE_VALUE + 1);
 
   // Provoke error in update from subscribers - return ERROR and update_and_write_commands not exec.
   controller.set_new_reference_interface_value(INTERFACE_VALUE_SUBSCRIBER_ERROR);
   ASSERT_EQ(
     controller.update(rclcpp::Time(0), rclcpp::Duration::from_seconds(0.01)),
     controller_interface::return_type::ERROR);
   ASSERT_EQ(controller.reference_interfaces_[0], INTERFACE_VALUE_INITIAL_REF - 1);
+  ASSERT_EQ(controller.state_interfaces_values_[0], EXPORTED_STATE_INTERFACE_VALUE + 1);
 
   // Provoke error from update - return ERROR, but reference interface is updated and not reduced
   controller.set_new_reference_interface_value(INTERFACE_VALUE_UPDATE_ERROR);
   ASSERT_EQ(
     controller.update(rclcpp::Time(0), rclcpp::Duration::from_seconds(0.01)),
     controller_interface::return_type::ERROR);
   ASSERT_EQ(controller.reference_interfaces_[0], INTERFACE_VALUE_UPDATE_ERROR);
+  ASSERT_EQ(controller.state_interfaces_values_[0], EXPORTED_STATE_INTERFACE_VALUE + 1);
 
   controller.reference_interfaces_[0] = 0.0;
 
@@ -181,6 +219,8 @@ TEST_F(ChainableControllerInterfaceTest, test_update_logic)
     controller.update(rclcpp::Time(0), rclcpp::Duration::from_seconds(0.01)),
     controller_interface::return_type::OK);
   ASSERT_EQ(controller.reference_interfaces_[0], -1.0);
+  ASSERT_EQ(
+    controller.state_interfaces_values_[0], EXPORTED_STATE_INTERFACE_VALUE_IN_CHAINMODE + 1);
 
   // Provoke error from update - return ERROR, but reference interface is updated directly
   controller.set_new_reference_interface_value(INTERFACE_VALUE_SUBSCRIBER_ERROR);
@@ -189,4 +229,6 @@ TEST_F(ChainableControllerInterfaceTest, test_update_logic)
     controller.update(rclcpp::Time(0), rclcpp::Duration::from_seconds(0.01)),
     controller_interface::return_type::ERROR);
   ASSERT_EQ(controller.reference_interfaces_[0], INTERFACE_VALUE_UPDATE_ERROR);
+  ASSERT_EQ(
+    controller.state_interfaces_values_[0], EXPORTED_STATE_INTERFACE_VALUE_IN_CHAINMODE + 1);
 }

controller_interface/test/test_chainable_controller_interface.hpp

@@ -29,24 +29,28 @@ constexpr double INTERFACE_VALUE = 1989.0;
 constexpr double INTERFACE_VALUE_SUBSCRIBER_ERROR = 12345.0;
 constexpr double INTERFACE_VALUE_UPDATE_ERROR = 67890.0;
 constexpr double INTERFACE_VALUE_INITIAL_REF = 1984.0;
+constexpr double EXPORTED_STATE_INTERFACE_VALUE = 21833.0;
+constexpr double EXPORTED_STATE_INTERFACE_VALUE_IN_CHAINMODE = 82802.0;
 
 class TestableChainableControllerInterface
 : public controller_interface::ChainableControllerInterface
 {
 public:
-  FRIEND_TEST(ChainableControllerInterfaceTest, reference_interfaces_storage_not_correct_size);
+  FRIEND_TEST(ChainableControllerInterfaceTest, interfaces_storage_not_correct_size);
   FRIEND_TEST(ChainableControllerInterfaceTest, test_update_logic);
 
   TestableChainableControllerInterface()
   {
     reference_interfaces_.reserve(1);
     reference_interfaces_.push_back(INTERFACE_VALUE);
+    state_interfaces_values_.reserve(1);
+    state_interfaces_values_.push_back(EXPORTED_STATE_INTERFACE_VALUE);
   }
 
   controller_interface::CallbackReturn on_init() override
   {
     // set default value
-    name_prefix_of_reference_interfaces_ = get_node()->get_name();
+    name_prefix_of_interfaces_ = get_node()->get_name();
 
     return controller_interface::CallbackReturn::SUCCESS;
   }
@@ -63,13 +67,24 @@ class TestableChainableControllerInterface
       controller_interface::interface_configuration_type::NONE};
   }
 
+  // Implementation of ChainableController virtual methods
+  std::vector<hardware_interface::StateInterface> on_export_state_interfaces() override
+  {
+    std::vector<hardware_interface::StateInterface> state_interfaces;
+
+    state_interfaces.push_back(hardware_interface::StateInterface(
+      name_prefix_of_interfaces_, "test_state", &state_interfaces_values_[0]));
+
+    return state_interfaces;
+  }
+
   // Implementation of ChainableController virtual methods
   std::vector<hardware_interface::CommandInterface> on_export_reference_interfaces() override
   {
     std::vector<hardware_interface::CommandInterface> command_interfaces;
 
     command_interfaces.push_back(hardware_interface::CommandInterface(
-      name_prefix_of_reference_interfaces_, "test_itf", &reference_interfaces_[0]));
+      name_prefix_of_interfaces_, "test_itf", &reference_interfaces_[0]));
 
     return command_interfaces;
   }
@@ -78,6 +93,7 @@ class TestableChainableControllerInterface
   {
     if (reference_interfaces_[0] == 0.0)
     {
+      state_interfaces_values_[0] = EXPORTED_STATE_INTERFACE_VALUE_IN_CHAINMODE;
       return true;
     }
     else
@@ -107,21 +123,22 @@ class TestableChainableControllerInterface
     }
 
     reference_interfaces_[0] -= 1;
+    state_interfaces_values_[0] += 1;
 
     return controller_interface::return_type::OK;
   }
 
   void set_name_prefix_of_reference_interfaces(const std::string & prefix)
   {
-    name_prefix_of_reference_interfaces_ = prefix;
+    name_prefix_of_interfaces_ = prefix;
   }
 
   void set_new_reference_interface_value(const double ref_itf_value)
   {
     reference_interface_value_ = ref_itf_value;
   }
 
-  std::string name_prefix_of_reference_interfaces_;
+  std::string name_prefix_of_interfaces_;
   double reference_interface_value_ = INTERFACE_VALUE_INITIAL_REF;
 };