What you need is to implement a global planner plugin that has service client built-in. Then, in a different node you implement a service server which is responsible for calculating the path each time it gets a service request.
ROS Services are explained Here
This is how to add a service client to the code shown by the Writing A Global Path Planner As Plugin in ROS tutorial:
Class Header
// SOME OTHER INCLUDE STATEMENTS
#include "***YOUR MESSAGE TYPE HERE***"
namespace global_planner {
class GlobalPlanner : public nav_core::BaseGlobalPlanner {
public:
// SOME CODE TO DECLARE PUBLIC MEMBERS
private :
// SOME CODE TO DECLARE PRIVATE MEMBERS
// service client declaration
ros::ServiceClient service_;
};
};
Class Implementation
void GlobalPlanner::initialize(std::string name, costmap_2d::Costmap2DROS* costmap_ros){
// OTHER INITIALIZATION CODE
// create a client for the path planning service
service_ = private_nh.serviceClient<***YOUR MESSAGE TYPE HERE***>("plan");
// wait for the service to be advertised and available
service_.waitForExistence();
}
then send a service request from inside of the body of the function GlobalPlanner::makePlan(), like so:
bool GlobalPlanner::makePlan(const geometry_msgs::PoseStamped& start, const geometry_msgs::PoseStamped& goal, std::vector<geometry_msgs::PoseStamped>& plan ){
// initialize a message of your custom message type
**YOUR MESSAGE TYPE** message_name;
// CODE TO FILL IN YOUR CUSTOM MESSAGE
// call the path planning service
service_.call(message_name);
// you must also process the service response (not shown here)
}
Don't forget to process the service response and store it to the variable name plan which is one of the parameters of the function GlobalPlanner::makePlan().
You will also have to modify your CMakeLists.txt file to include your custom message type. All about how to create a custom service message is explained here: Creating a ROS msg and srv tutorial
Note that this is not a cut-and-paste ready-to-go example. You will have to additionally:
- define a custom message
- create a service server
- fill in the service request, and
- process the service response
Hopefully this information is enough to get you started and that it also answers your question.
