Hello Sumitha,
In order to use servo motors with National Instruments motion controllers, you must have some form of position feedback. This is required due to the PID control loop implemented on the controller. Without some kind of control loop, there is no way to guarantee that the motor will get to the commanded position following the specified trajectory. Servo Tune is a tool used to adjust the PID parameters, which in turn control the stability of your system.
If you do not have any way of adding position feedback (such as a quadrature encoder), you will not be able to make full use of your motion controller. It is possible to simply read a voltage in and output a specified voltage from the motion controller. However, you lose all hardware timed control and all the benefits of a motion controller. If you are interested in that option, a DAQ board might work better for you. Otherwise, I highly recommend looking into adding a quadrature encoder to your system.
Best Regards,
Jesse D.
Applications Engineering
National Instruments