is_battery_low_condition.cpp

// Copyright (c) 2020 Sarthak Mittal
// Copyright (c) 2019 Intel Corporation
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
 
#include <string>
 
#include "nav2_behavior_tree/plugins/condition/is_battery_low_condition.hpp"
 
namespace nav2_behavior_tree
{
 
IsBatteryLowCondition::IsBatteryLowCondition(
  const std::string & condition_name,
  const BT::NodeConfiguration & conf)
: BT::ConditionNode(condition_name, conf),
  battery_topic_("/battery_status"),
  min_battery_(0.0),
  is_voltage_(false),
  is_battery_low_(false)
{
  initialize();
 
  // Spin multiple times due to rclcpp regression in Jazzy requiring a 'warm up' spin
  callback_group_executor_.spin_some(std::chrono::nanoseconds(1));
}
 
void IsBatteryLowCondition::initialize()
{
  getInput("min_battery", min_battery_);
  getInput("is_voltage", is_voltage_);
 
  createROSInterfaces();
}
 
void IsBatteryLowCondition::createROSInterfaces()
{
  std::string battery_topic_new;
  getInput("battery_topic", battery_topic_new);
 
  // Only create a new subscriber if the topic has changed or subscriber is empty
  if (battery_topic_new != battery_topic_ || !battery_sub_) {
    battery_topic_ = battery_topic_new;
    node_ = config().blackboard->get<rclcpp::Node::SharedPtr>("node");
    callback_group_ = node_->create_callback_group(
      rclcpp::CallbackGroupType::MutuallyExclusive,
      false);
    callback_group_executor_.add_callback_group(callback_group_, node_->get_node_base_interface());
 
    rclcpp::SubscriptionOptions sub_option;
    sub_option.callback_group = callback_group_;
    battery_sub_ = node_->create_subscription<sensor_msgs::msg::BatteryState>(
      battery_topic_,
      rclcpp::SystemDefaultsQoS(),
      std::bind(&IsBatteryLowCondition::batteryCallback, this, std::placeholders::_1),
      sub_option);
  }
}
 
BT::NodeStatus IsBatteryLowCondition::tick()
{
  if (!BT::isStatusActive(status())) {
    initialize();
  }
 
  callback_group_executor_.spin_some();
  if (is_battery_low_) {
    return BT::NodeStatus::SUCCESS;
  }
  return BT::NodeStatus::FAILURE;
}
 
void IsBatteryLowCondition::batteryCallback(sensor_msgs::msg::BatteryState::SharedPtr msg)
{
  if (is_voltage_) {
    is_battery_low_ = msg->voltage <= min_battery_;
  } else {
    is_battery_low_ = msg->percentage <= min_battery_;
  }
}
 
}  // namespace nav2_behavior_tree
 
#include "behaviortree_cpp/bt_factory.h"
BT_REGISTER_NODES(factory)
{
  factory.registerNodeType<nav2_behavior_tree::IsBatteryLowCondition>("IsBatteryLow");
}