请给出一个moveit控制器的代码示例

以下是一个基于MoveIt Simple Controller Manager的ROS控制器示例：

#include <ros/ros.h>
#include <moveit_simple_controller_manager/simple_controller_manager.h>
#include <moveit/move_group_interface/move_group_interface.h>
#include <moveit/robot_model_loader/robot_model_loader.h>
#include <moveit/robot_model/robot_model.h>
#include <moveit/robot_state/robot_state.h>
#include <moveit/trajectory_processing/iterative_time_parameterization.h>

class MyRobotController : public moveit_simple_controller_manager::SimpleControllerManager
{
public:
    MyRobotController() : moveit_simple_controller_manager::SimpleControllerManager()
    {
        // Initialize MoveIt
        move_group_.reset(new moveit::planning_interface::MoveGroupInterface("arm"));

        // Load the robot model and get the robot state
        robot_model_loader_.reset(new robot_model_loader::RobotModelLoader("robot_description"));
        robot_model_ = robot_model_loader_->getModel();
        robot_state_.reset(new robot_state::RobotState(robot_model_));

        // Set the joint model group
        joint_model_group_ = robot_model_->getJointModelGroup("arm");

        // Set the trajectory processing
        trajectory_processing_.reset(new trajectory_processing::IterativeParabolicTimeParameterization());

        // Set the desired joint state
        desired_joint_state_.resize(joint_model_group_->getVariableCount());
        desired_joint_state_.setZero();
    }

    virtual bool initialize(const std::string& robot_description, const std::string& controller_name)
    {
        // Initialize the controller with the robot description and the controller name
        if (!SimpleControllerManager::initialize(robot_description, controller_name))
        {
            ROS_ERROR("Failed to initialize the controller");
            return false;
        }

        // Set the callback function for the controller
        controller_->setTrajectoryExecutionCallback(boost::bind(&MyRobotController::trajectoryExecutionCallback, this, _1));

        // Print a message to indicate successful initialization
        ROS_INFO("Controller initialized successfully");
        return true;
    }

    virtual bool canSwitch(const std::vector<std::string>& start_controllers, const std::vector<std::string>& stop_controllers) const
    {
        // This controller does not support switching
        return false;
    }

    virtual bool switchControllers(const std::vector<std::string>& start_controllers, const std::vector<std::string>& stop_controllers)
    {
        // This controller does not support switching
        return false;
    }

    virtual bool isActive()
    {
        // Return true if the controller is active
        return controller_->isActive();
    }

    virtual void stopping()
    {
        // Stop the controller
        controller_->stop();
    }

    void trajectoryExecutionCallback(const moveit_msgs::RobotTrajectory& trajectory)
    {
        // Get the start state of the robot
        robot_state_->setToDefaultValues();
        const robot_state::JointModelGroup* start_joint_model_group = robot_state_->getJointModelGroup("arm");

        // Get the start and end time of the trajectory
        double start_time = ros::Time::now().toSec();
        double end_time = start_time + trajectory.joint_trajectory.points.back().time_from_start.toSec();

        // Execute the trajectory
        move_group_->execute(trajectory);

        // Wait until the end of the trajectory
        while (ros::Time::now().toSec() < end_time)
        {
            ros::Duration(0.01).sleep();
        }

        // Get the current joint state of the robot
        robot_state_->getCurrentState(*move_group_->getCurrentState());
        const robot_state::JointModelGroup* current_joint_model_group = robot_state_->getJointModelGroup("arm");

        // Get the current joint values
        robot_state_->copyJointGroupPositions(current_joint_model_group, desired_joint_state_);

        // Set the current joint values as the desired joint state
        controller_->setDesiredJointState(desired_joint_state_);

        // Print a message to indicate successful trajectory execution
        ROS_INFO("Trajectory executed successfully");
    }

private:
    ros::NodeHandle nh_;
    moveit::planning_interface::MoveGroupInterfacePtr move_group_;
    robot_model_loader::RobotModelLoaderPtr robot_model_loader_;
    robot_model::RobotModelPtr robot_model_;
    robot_state::RobotStatePtr robot_state_;
    const robot_model::JointModelGroup* joint_model_group_;
    std::unique_ptr<trajectory_processing::IterativeParabolicTimeParameterization> trajectory_processing_;
    Eigen::VectorXd desired_joint_state_;
};

int main(int argc, char** argv)
{
    // Initialize ROS
    ros::init(argc, argv, "my_robot_controller");

    // Create the controller
    MyRobotController controller;

    // Initialize the controller
    if (!controller.initialize("robot_description", "my_robot_controller"))
    {
        return -1;
    }

    // Spin the node
    ros::spin();

    return 0;
}

在上述示例中，MyRobotController是一个自定义的ROS控制器，它继承自MoveIt Simple Controller Manager。在构造函数中，我们初始化了MoveIt，加载了机器人模型，并设置了轨迹处理和期望关节状态。在initialize()函数中，我们初始化了控制器，并设置了回调函数。在trajectoryExecutionCallback()函数中，我们执行了轨迹，并在轨迹执行完成后更新了期望关节状态。最后，在main()函数中，我们创建了并初始化了控制器，并开始运行ROS节点。