Here’s a combination that takes you from an arm bar attempt to a powerful guard sweep from the closed guard, demonstrated by BJJ black belt Andreh Anderson.
Opponent starts in your closed guard.
Reach under his leg to set up your pendulum sweep. Your palm should be facing up. Your other hand controls his sleeve.
Pull your head in close to his knee, careful to keep your legs tight against his body.
Swing your leg out and pull his weight forward to sweep.
Your opponent steps up with his far leg to block the sweep.
Pass your leg over for the armbar.
Switch your grip, squeeze your legs together, and lift your hips to finish the armbar.
Another option instead of the armbar (or if the opponent pulls his arm out of the armbar, is to switch your grip to his other sleeve.
Then roll over your shoulder closest to his knee (the one you underhooked). Maintain your grip on his sleeve and try to get your hips as close to his shoulder as possible.
Continue your roll until you make it to your knees, this should drop him to the mat.
Once you are on your knees and he has hit the mat, keep his arm secured and straighten your body up. The higher you keep his arm raised, the harder it is for him to hip escape and put you back in the guard.
With one hand on the sleeve, plant your other hand on the mat and swing your leg backward over his head to mount. Keep his arm secured and raised throughout the entire movement.