The difference of new df_dx and df_dw matrix after using ikfom

[daijicheng]

Thanks for your brilliant work. After switching to ikfom, the function df_dx and df_dw in use-ikfom.hpp line 52 and line 71 have changed. However, due to the lack of relevant information about the function predict of ikfom, the current changes are difficult to understand. Is it convenient for the author to give a description of the new matrix.

[Joanna-HE]

In the use-ikfom.hpp, there is also a f function that is defined according to the system. df_dx and df_dw are calculated by differentiating the f function with respect the state. The reason for calculating in this way is that the ikfom give a new formulation to the system, which makes it easy to deploy an iterated EKF for a certain system.

[ZhangZh3ng]

In the use-ikfom.hpp, there is also a f function that is defined according to the system. df_dx and df_dw are calculated by differentiating the f function with respect the state. The reason for calculating in this way is that the ikfom give a new formulation to the system, which makes it easy to deploy an iterated EKF for a certain system.

请问，您能更详细的解释一下df_dx的计算原理吗，代码采用的算法已经与fast-lio论文中的公式7对不上了。

[Joanna-HE]

df_dx的计算就是f函数对x的导数，其中f函数和fast-lio论文中定义的一样，区别在于，df_dx不是最终展示在fast-lio论文中的雅可比矩阵的结果，还需要和ikfom中自行计算的与manifold相关的结果结合起来，才是最终的雅可比矩阵。

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寄件者: Zhang Zheng @.> 寄件日期: 2022年11月16日 下午 03:14 收件者: hku-mars/FAST_LIO @.> 副本: He Dongjiao @.>; Comment @.> 主旨: Re: [hku-mars/FAST_LIO] The difference of new df_dx and df_dw matrix after using ikfom (Issue #94)

In the use-ikfom.hpp, there is also a f function that is defined according to the system. df_dx and df_dw are calculated by differentiating the f function with respect the state. The reason for calculating in this way is that the ikfom give a new formulation to the system, which makes it easy to deploy an iterated EKF for a certain system.

请问，您能更详细的解释一下df_dx的计算原理吗，代码采用的算法已经与fast-lio论文中的公式7对不上了。

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