Codeigniter form_open_multipart showing 403 Forbidden (CSRF) - codeigniter

Question

I am trying to post data though ajax post but somehow unable to post . am getting 403 forbidden. Fortunately my other ajax posts are submitting properly as they are getting right re-generated token. But in form_open_multipart it's not working.
CI config
$config['csrf_protection'] = TRUE;
$config['csrf_token_name'] = 'my_token';
$config['csrf_cookie_name'] = 'my_cookie';
$config['csrf_expire'] = 7200;
$config['csrf_regenerate'] = TRUE;
$config['csrf_exclude_uris'] = array();
form_open is working well, but in the case of multi part it's not working well !!!!
my HTML
<?php $parameter = array('id' => 'frm_id', 'class' => 'form-horizontal'); echo form_open_multipart('controller/save',$parameter) ;?>
<div class="form-body">
<div class="form-group">
<label class="col-md-3 control-label">Name</label>
<div class="col-md-6">
<div class="input-icon">
<i class="fa fa-bell-o"></i>
<input type="text" id="catId" class="form-control " placeholder="Type Something..." name='name' />
</div>
</div>
</div>
<div class="form-group">
<label class="col-md-3 control-label">Description</label>
<div class="col-md-6">
<div>
<textarea class="form-control" rows="3" name="description"></textarea>
</div>
</div>
</div>
<div class="form-group">
<label class="col-md-3 control-label">Image 1</label>
<div class="col-md-6">
<div>
<input type="file" name="thumb_image">
</div>
</div>
</div>
<div class="form-group">
<label class="col-md-3 control-label">Image 2</label>
<div class="col-md-6">
<div>
<input type="file" name="banner_image">
</div>
</div>
</div>
</div>
<div class="form-actions">
<div class="row">
<div class="col-md-offset-3 col-md-9">
<button type="submit" class="btn btn-flat green">Submit</button>
<button type="button" class="btn btn-flat grey-salsa">Cancel</button>
</div>
</div>
</div>
<?php echo form_close() ;?>
My JS
<script type="text/javascript">
var frmSave = $('#frm_id');
frmSave.on('submit', function(event){
event.preventDefault();
$form=$(this);
var fd = new FormData($('#frm_id')[0]);
$.ajax({
url: $form.attr('action'),
type: $form.attr('method'),
dataType: 'json',
data: fd,
contentType: false,
cache: false,
processData: false,
success: function(data){
console.log(data)
}
})
});
</script>
Still I am getting this message
An Error Was Encountered. The action you have requested is not
allowed.

Answer 1

var vl = "; " + document.cookie;
var pr = vl.split("; csrf_cookie=");
var obj; if (pr.length == 2) { obj = pr.pop().split(";").shift(); }
using this variable in the ajax body section like
data : '<?php echo $this->security->get_csrf_token_name(); ?>': obj
Now it's working fine.