สอบถามหน่อยครับ CodeIgniter 3 ผมทำหน้า สมัครสมาชิกแล้ว มันไม่ยอมเซฟลงฐาน ผมต้องใส่โค้ดอะไร

<?php
defined('BASEPATH') OR exit('No direct script access allowed');

class Register extends MY_Controller {

	public function __construct()
	{
        parent::__construct();

        // LOAD MODEL
        $this->load->model('userModel', '', true);
        $this->load->model('productModel', '', true);
		$this->load->model('model_register', '', true);

        // LOAD LIBRARY
        $this->load->library('MyUpload');
        $this->load->library('MyDateSystem');
        $this->load->library('MyExcel');
		
		$this->load->helper(array('form', 'url')); // โหลดเฮลเปอร์ form และ url ของ ci มาใช้งาน
		$this->load->library('form_validation'); // โหลดไลบรารี่ form_validation ของ ci มาใช้งาน
		$this->load->library('session');  // เรียกใช้งาน session
		/*$this->load->library('MyUpload');
        $this->load->library('MyDateSystem');*/
		
	}
	public function index()
    {
        if (!$this->session->userdata('userLogData')) {
            $this->data['title'] = 'ระบบฐานข้อมูลครุภัณฑ์และทรัพย์สินในสำนักงาน';
            $this->content = 'login';
            $this->layout('full-width-no-header');
        } else {
            redirect('register/validate', 'refresh');
        }
    }
	

	public function validate()
	{
		$this->form_validation->set_rules('username','required');
		$this->form_validation->set_rules( 'password','required');
	    $this->form_validation->set_rules( 'name','required');
		//$this->form_validation->set_rules('email', 'Email', 'required');

		if ($this->form_validation->run() == FALSE)
		{
			
				$this->data['title'] = 'สมัครสมาชิก';
				//$this->load->view('register_view');
		        $this->content = 'register/register_view';
				$this->layout();

		}else{
			$this->load->view('register/register_view');
			$username = $this->input->post('text_username');
			$password = $this->input->post('text_password');
			$encodePassword = md5(md5($Password));
			$name = $this->input->post('text_name');
			//$email = $this->input->post('email');
			
			$data = array(
		'text_username'     => $username,
		'text_password'     => $password,
		'text_name'     => $name
	);
		$this->db->insert('users', $data, ['user_id' => $id]);
			
}
		}
	}

<?php
defined('BASEPATH') OR exit('No direct script access allowed');

class Model_register extends CI_Model {

  public function validate($inputs, $id)
    {
        $user = $this->getUserData($id);

        if ($user->password == md5(md5($inputs['txt_current_password']))) {
            if (!empty($inputs['txt_new_password']) && $inputs['txt_new_password'] == $inputs['txt_confirm_password']) {
                $data = [
                    'password' => md5(md5($inputs['txt_new_password'])),
                    //'password_format' => $inputs['txt_new_password']
                ];
 // PUT ALL DATA TO ARRAY
        $insertData = array(
                      
                        'username' => $username,
                        'password' => $password,
                        'name' => $name,
			);
                      
        // INSERT DATA
        $this->db->insert('users', $id);
	}
     
}
	}
}

 <div class="row">
    <div class="col-lg-12">
        <h1 class="page-header"><?php echo $title; ?></h1>
        <ol class="breadcrumb">
            <li class="active">
                <i class="fa fa-dashboard"></i> <a href="<?php echo base_url('dashboard/index'); ?>">หน้าหลัก</a>
            </li>
           
            <li class="active">
                <i class="fa fa-pencil"></i> <?php echo $title; ?>
            </li>
        </ol>
    </div>
</div>
  <div class="row">
  <?php echo form_open('register/validate'); ?>
  <form action="" method="POST" name="register"  id="register">
        <table width="70%" border="0" align="center" cellpadding="0" cellspacing="0">
          <tr>
            <td width="18%" align="right"> ชื่อผู้ใช้งาน &nbsp;</td>
            <td width="31%"><input name="text_username" type="text" id="text_username" class="form-control" placeholder="ภาษาอังกฤษหรือตัวเลข" required> <span id="msg2"></span> </td>
            <td>&nbsp;</td>
            <td>&nbsp;</td>
          </tr>
          <tr>
            <td align="right"> รหัสผ่าน &nbsp;</td>
            <td><input name="text_password" type="password" id="text_password" class="form-control" placeholder="อย่างน้อย 8 ตัว"  required></td>
            <td>&nbsp;</td>
            <td>&nbsp;</td>
          </tr>
          <tr>
            <td align="right">ยืนยันรหัสผ่าน&nbsp;</td>
            <td>
            <input name="txt_confirm_password" type="password" id="txt_confirm_password" placeholder="ยืนยันรหัสผ่าน " class="form-control"  required >        
</td>
            <td>&nbsp;</td>
            <td>&nbsp;</td>
          </tr>
          <tr>
            <td align="right"> ชื่อ &nbsp;</td>
            <td colspan="2">
            <input name="text_name" type="text" id="text_name"  class="form-control" placeholder="ภาษาไทยหรืออังกฤษ" required></td>
            <td>&nbsp;</td>
   
          <tr>
            <td align="center">&nbsp;</td>
            <td colspan="3" align="center">
            </td>
          </tr>
          <tr>
            <td align="center">&nbsp;</td>
            <td colspan="3" align="left">
            <input type="submit" name="regis" id="regis" class="btn btn-info btn-sm" value="สมัครสมาชิก" >
            
            </td>
          </tr>
        </table>
      </form>
      </div>
    </div>
  </div>