IMU预积分

https://www.sohu.com/a/242760307_715754

http://www.sohu.com/a/243155537_715754

https://www.sohu.com/a/243601310_715754

http://m.sohu.com/a/244040730_715754

https://search.bilibili.com/all?keyword=vio%E9%A2%84%E7%A7%AF%E5%88%86