Yes, You are still a permanent resident if your card expires.
It just means you didn't renew it. You can renew it even after it expires if you satisfy all the conditions including the residency obligation that you mentioned.
You are still a Permanent Resident until you lose your PR status by following methods.,
- an adjudicator determines you are no longer a permanent resident after an inquiry or PRTD appeal;
- you voluntarily renounce your permanent resident status;
- a removal order is made against you and comes into force; or
- you become a Canadian citizen.