mesmo erro

[eieieiirjrj]

void setup ()
{
  Lcd_1.begin(16,2);
}

void loop()
{
  Lcd_1.clear();
   Lcd_1.setCursor (4,0);
    Lcd_1.setBacklight(1);
     Lcd_1.print("sensor de ar comprimido");
      Lcd_1.setCursor(3,1);
       Lcd_1.setBacklight(1);
        Lcd_1.print("presao 19/2");
 delay (200);
}
 

esta dando erro no lcd_1.clear();

'Lcd_1' was not declared in this scope