Problem

QUESIION7 Transforming a Vector from World Space to Local Space Choose one $\cdot 5$ points A vector coordinate in world space is $\vec{r}=(1,0,2)$, calculate the vector coordinate in body frame coordinate (rigid body) $\vec{r} 0$ if the orientation of the rigid body is 90 about the global z-axis. Note: use $\overrightarrow{r_{0}}=\boldsymbol{R}^{t} \cdot \vec{r}$ $\left(\begin{array}{l}0 \\ 1 \\ 2\end{array}\right)$ $\left(\begin{array}{l}2 \\ 0 \\ 1\end{array}\right)$ $\left(\begin{array}{c}0 \\ -1 \\ 2\end{array}\right)$

Solution

Step 1 :The problem is asking to transform a vector from world space to local space. This involves rotating the vector by the orientation of the rigid body, which is given as 90 degrees about the global z-axis. The formula given to perform this transformation is \(\overrightarrow{r_{0}}=\boldsymbol{R}^{t} \cdot \vec{r}\), where \(\boldsymbol{R}^{t}\) is the transpose of the rotation matrix and \(\vec{r}\) is the vector in world space.

Step 2 :The rotation matrix for a rotation of 90 degrees about the z-axis is: \[\boldsymbol{R} = \begin{bmatrix} cos(90) & -sin(90) & 0 \\ sin(90) & cos(90) & 0 \\ 0 & 0 & 1 \end{bmatrix} = \begin{bmatrix} 0 & -1 & 0 \\ 1 & 0 & 0 \\ 0 & 0 & 1 \end{bmatrix}\]

Step 3 :The transpose of this matrix is: \[\boldsymbol{R}^{t} = \begin{bmatrix} 0 & 1 & 0 \\ -1 & 0 & 0 \\ 0 & 0 & 1 \end{bmatrix}\]

Step 4 :So, we need to multiply this matrix with the vector \(\vec{r}=(1,0,2)\) to get the vector in the body frame coordinate.

Step 5 :The result of the matrix multiplication gives the vector in the body frame coordinate as (0, -1, 2). This matches one of the options given in the question.

Step 6 :Final Answer: The vector coordinate in body frame coordinate is \(\boxed{\left(\begin{array}{c}0 \\ -1 \\ 2\end{array}\right)}\).

From Solvely APP
Source: https://solvelyapp.com/problems/37717/

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