$jquery con codeigniter non capisco la chiamata URL non funziona.

[marcopa]

Salve a tutti,
come da titolo, ho un problema nel capire il percorso della chiamata URL in $ajax, non riesco a far eseguire delle funzioni dentro un controller chiamate da uno script di Fullcalendar.
lo script ha questo codice :
ho il calendario in /view/calendar/fullcalendar.php
il controller in /controllers/Fullcalendar.php
il model in /models/Fullcalenda_model.php

    <script>
    $(document).ready(function(){
        
        var calendar = $('#calendar').fullCalendar({
            editable:true,
            header:{
                left:'prev,next today',
                center:'title',
                right:'month,agendaWeek,agendaDay'
            },
            events:"<?=base_url();?>fullcalendar/load" ,

            selectable:true,
            selectHelper:true,
    
    
            select:function(start, end, allDay)
            {
                var title = prompt("Scrivi un Titolo ");
                if(title)
                {
                    var start = $.fullCalendar.formatDate(start, "Y-MM-DD HH:mm:ss");
                    var end = $.fullCalendar.formatDate(end, "Y-MM-DD HH:mm:ss");
                    $.ajax({
                        url: "<?=base_url();?>fullcalendar/insert",
                        type:"POST",
                        data:{title:title, start:start, end:end},
                        success:function(data)
                        {
                            calendar.fullCalendar('refetchEvents');
                            alert("Aggiunto correttamente");
                        },
                         error : function(){
                                       alert(events);
                                }
                    })
                }
            },
            
          
             
            editable:true,
            eventResize:function(event)
            {
                var start = $.fullCalendar.formatDate(event.start, "Y-MM-DD HH:mm:ss");
                var end = $.fullCalendar.formatDate(event.end, "Y-MM-DD HH:mm:ss");

                 var title = event.title;
                 var id = event.id;

                $.ajax({
                    url:"<?php echo base_url(); ?>fullcalendar/update",
                    type:"POST",
                    data:{title:title, start:start, end:end, id:id},
                    success:function()
                    {
                        calendar.fullCalendar('refetchEvents');
                        alert("Event Update");
                    }
                })
            },
            eventDrop:function(event)
            {
                var start = $.fullCalendar.formatDate(event.start, "Y-MM-DD HH:mm:ss");
                //alert(start);
                var end = $.fullCalendar.formatDate(event.end, "Y-MM-DD HH:mm:ss");
                //alert(end);
                var title = event.title;
                var id = event.id;
                $.ajax({
                    url:"<?php echo base_url(); ?>fullcalendar/update",
                    type:"POST",
                    data:{title:title, start:start, end:end, id:id},
                    success:function()
                    {
                        fullcalendar.fullCalendar('refetchEvents');
                        alert("Event Updated");
                    }
                })
            },
            eventClick:function(event)
            {
                if(confirm("Sei sicuro di voler cancellerare ?"))
                {
                    var id = event.id;
                    $.ajax({
                        url:"<?php echo base_url(); ?>fullcalendar/delete",
                        type:"POST",
                        data:{id:id},
                        success:function()
                        {
                            calendar.fullCalendar('refetchEvents');
                            alert('Event Removed');
                        }
                    })
                }
            }
        });
    });
             
    </script>

ci sto girando intorno da ieri, provo a modificare i percorsi anche estendendo il tutto da
application/controllers/fullcalendar ma non ottengo nessun risultato.
Qualcuno che mi pu� dare una delucidazione? Grazie mille.