Yes manually operated gates can be made automatic but the gate must have certain things in place before this is possible.  If a swing gate drags on the ground so is difficult to open making it automatic won't solve the problem, the gate must first be repaired so it opens freely before it can be automated.

Swing Gates

Must be plumb, level and swing freely in both directions at all times. The gate must move throughout its arc without binding in the hinges or dragging on the ground. Posts should be firm in the ground and not move. The frame of the gate must be rigid with no cracked or rusty welds.

If a gate has a wheel supporting its weight this must be removed and posts and/or hinges replaced to support the weight of the gate adequately. 

Note: gates over 100kg should have ball bearing hinges.

If the gate doesn't swing freely then the posts may need replacing or repaired 

... more about Installing Posts for Automatic Gates

If the hinges are stiff, loosely fitted or rusty they too may need replacing 

... more about Hinges for Swing Gates 

If your gate is on sloping ground causing it to drag on the ground 

... more about Swing Gates on Sloping Ground 

All bolts or catches used to lock a gate must be removed and a hard stop installed for the gate to close against. The Gate Motor will hold the gate firmly against a hard stop when closed but an electric lock is recommended for gates wider than 2m or if the gate has a rigid frame 3m 

... more about Electrically locking Swing Gates

There must be enough space behind the gate when open.  Generally Linear motors require 120mm and articulated arm motors 600mm behind the gate when open.  Check the install manual of a swing gate operator or find out from the seller how much space it requires behind the open gate before buying, because if you don't it may not fit.

Sliding Gates

Must be straight and slide freely throughout their entire length without any grabbing from the guides or track any where along the path of the gate. The gate track must be straight, any sudden dips or rises may prevent the gate motor from working properly. Repair or replace all worn or damaged gate hardware prior to installation.

If the sliding gate has a guide post there must be adequate clearance behind the gate for the rack, which is the tooth length of rod that fits to the gate and connects to the output gear of the motor. 

If a guide post is used behind the gate it must have adequate clearance for rack, which is required by the motor.

You will also need a mounting for the motor, which is normally a concrete pad 

... more about Pads for Gate Motors 

Choosing a Sliding Gate Motor (Operator) Choosing a Swing Gate Operator