Independent Sleeping

How can I sleep train my son to sleep on his own at night? When he is asleep on our bed, I would trf him to his cot, but he will wake up - somehow knows that he has been shifted to his own bed. He was a great independent sleeper before this. But lately he has been wanting to sleep with us every night. He is 7m. During the day, he has no problem sleeping by himself in his cot. Only at night he wants to be with us on the bed together. My husband and I need space! 😂