jquery获取文本框值并传递给控制器​​操作

I have two textbox in form.

when i type some value inside textbox and click the button then i want to echo this value in my function.

I want to take value of my textbox and pass this in my controler function on button click using javascript and ajax.

but my script is not working and not showing any value..

 <script>
    $(document).ready(function() {
        $("#subvessels").on('click', function() {
            var shipment_title = $("#shipment_title").val(); //textbox value 
            var shipment_point = $("#shipment_point").val(); //textbox value  
            if (shipment_point) {
                var dataString = 'shipment_title=' + shipment_title;
                var dataString = 'shipment_point=' + shipment_point;
                var values = $(this).serialize();
                ajaxRequest = $.ajax({
                    url: '<?php echo Router::url(array("controller" => "DispatchedJobs", "action" => "approxBudget")); ?>',
                    type: 'POST',
                    data: dataString,
                    dataType: "html",
                    beforeSend: function() {
                        $('.spinicon').show();
                    },
                    success: function(response) {
                        $("#vessels_table").html(response);
                    },
                    complete: function() {
                        $('.spinicon').hide();
                    }
                });
            }
        });
    });
</script>

//controller function
 public function approxBudget($shipment_point,$shipment_title)
    {
        echo $shipment_title;
        echo $shipment_point; exit();

    }