1.Virtual reality systems can be used to train pilots, doctors, and engineers. These systems are seen most often in video games.

2. a head-mounted display is made of a headset with a screen for each eye. the display connects to a computer.
3. a tracking device senses the eye movements of the user. tracking devices are usually built into the headset.
4. The computer creates an artificial world that seems real to the user. The images of the two screens are blended by the computer .

I need to combine by inserting participial and absolute phrases.

do these seem correct.

1. Virtual reality systems, which are seen most often in video games, can also be used to train pilots, doctors, and engineers.
2. A head-mounted display connecting to a computer, is made of a headset with a screen for each eye.
3. A tracking device, which is usually built into the headset, senses the eye movement of the user.
4. The images of the two screens are blended together by the computer which creates an artificial world that seems real to the user.

John/Dale/whoever ...

See the prior post.

Your combined sentences with participial and absolute phrases look correct. Here they are:

1. Virtual reality systems, seen most often in video games, can also be used to train pilots, doctors, and engineers.
2. A head-mounted display, connecting to a computer, is made of a headset with a screen for each eye.
3. A tracking device, usually built into the headset, senses the eye movement of the user.
4. The computer, creating an artificial world that seems real to the user, blends the images of the two screens together.