4.1.A - 习题课

机器人机构学

本文是自由度分析的习题课,逐步演示并联机构中自由度分析、公共约束分析与冗余约束分析三套步骤的实际操作。


本文将演示 Sarrus 机构与 Scott-Russell 机构的两个完整算例。

例 1:Sarrus 机构分析

a. 前置分析

根据图示 Sarrus 机构建立坐标系,写出各运动副的运动旋量,并建立两条支链的运动旋量系与约束旋量系。

Sarrus机构
答案

两条支链的约束旋量系分别为

Sb1r=span⁡{(1,0,0;0,0,0),(0,0,0;0,1,0),(0,0,0;0,0,1)},\mathcal{S}^r_{b1}=\operatorname{span}\left\{(1,0,0;0,0,0),(0,0,0;0,1,0),(0,0,0;0,0,1)\right\},Sb2r=span⁡{(0,1,0;0,0,0),(0,0,0;1,0,0),(0,0,0;0,0,1)}.\mathcal{S}^r_{b2}=\operatorname{span}\left\{(0,1,0;0,0,0),(0,0,0;1,0,0),(0,0,0;0,0,1)\right\}.
解析

此机构可以视为一个含2个支链的并联机构

建系如图,可得运动旋量:

$1=(1,0,0;0,0,0)\boldsymbol{\$_1}=(1,0,0;0,0,0)$2=(1,0,0;0,a,b)\boldsymbol{\$_2}=(1,0,0;0,a,b)$3=(1,0,0;0,c,d)\boldsymbol{\$_3}=(1,0,0;0,c,d)$4=(0,1,0;e,0,f)\boldsymbol{\$_4}=(0,1,0;e,0,f)$5=(0,1,0;g,0,h)\boldsymbol{\$_5}=(0,1,0;g,0,h)$6=(0,1,0;0,0,0)\boldsymbol{\$_6}=(0,1,0;0,0,0)

对于支链1,运动旋量系:

Sb1=span⁡{$1T$2T$3T}=span⁡{(1,0,0;0,0,0)(1,0,0;0,a,b)(1,0,0;0,c,d)}\mathcal{S}_{b1} =\operatorname{span}\left\{\begin{aligned}&\boldsymbol{\$_1}^T \\&\boldsymbol{\$_2}^T\\&\boldsymbol{\$_3}^T\\\end{aligned}\right\}=\operatorname{span}\left\{\begin{aligned}&(1,0,0;0,0,0)\\&(1,0,0;0,a,b)\\&(1,0,0;0,c,d)\end{aligned}\right\}

由SbiΔ$i=0\mathcal{S}_{bi}\boldsymbol{\Delta}\boldsymbol{\text{\textdollar}}_i=\boldsymbol{0},可得支链1约束旋量系:

span⁡{(1,0,0;0,0,0)(0,0,0;0,1,0)(0,0,0;0,0,1)}\operatorname{span}\left\{\begin{aligned}&(1,0,0;0,0,0)\\&(0,0,0;0,1,0)\\&(0,0,0;0,0,1)\end{aligned}\right\}

对于支链2,运动旋量系:

span⁡{$6T$5T$4T}=span⁡{(0,1,0;0,0,0)(0,1,0;g,0,h)(0,1,0;e,0,f)}\operatorname{span}\left\{\begin{aligned}&\boldsymbol{\$_6}^T \\&\boldsymbol{\$_5}^T\\&\boldsymbol{\$_4}^T\\\end{aligned}\right\}=\operatorname{span}\left\{\begin{aligned}&(0,1,0;0,0,0)\\&(0,1,0;g,0,h)\\&(0,1,0;e,0,f)\end{aligned}\right\}

支链2约束旋量系:

span⁡{(0,1,0;0,0,0)(0,0,0;1,0,0)(0,0,0;0,0,1)}\operatorname{span}\left\{\begin{aligned}&(0,1,0;0,0,0)\\&(0,0,0;1,0,0)\\&(0,0,0;0,0,1)\end{aligned}\right\}

b. 自由度分析

根据两条支链的约束旋量系,求动平台的约束旋量系、运动旋量系及自由度。

答案

Sf=span⁡{(0,0,0;0,0,1)}\mathcal{S}_f=\operatorname{span}\{(0,0,0;0,0,1)\},因此 F=1F=1,机构具有一个沿 ZZ 轴平动的自由度。

解析

由支链约束旋量系可得动平台约束旋量系:

Sb1r∪Sb2r=span⁡{(1,0,0;0,0,0)(0,0,0;0,1,0)(0,0,0;0,0,1)(0,1,0;0,0,0)(0,0,0;1,0,0)}\mathcal{S}^{r}_{b1} \cup \mathcal{S}^{r}_{b2}=\operatorname{span}\left\{\begin{aligned}&(1,0,0;0,0,0)\\&(0,0,0;0,1,0)\\&(0,0,0;0,0,1)\\&(0,1,0;0,0,0)\\&(0,0,0;1,0,0)\end{aligned}\right\}

因此,求解 SrΔ$=0\mathcal{S}^r \boldsymbol{\Delta} \boldsymbol{\text{\textdollar}} = \boldsymbol{0},得:

span⁡{(0,0,0;0,0,1)}\operatorname{span}\left\{\begin{aligned}(0,0,0;0,0,1)\end{aligned}\right\}

即,自由度F=dim⁡(Sf)=1F = \dim(\mathcal{S}_f)=1,包含一个沿 ZZ 轴平动的自由度。

c. 公共约束分析

根据两条支链的运动旋量系,求机构的公共约束旋量系与公共约束数。

答案

Sc=span⁡{(0,0,0;0,0,1)}\mathcal{S}^c=\operatorname{span}\{(0,0,0;0,0,1)\},公共约束数为 dim⁡(Sc)=1\dim(\mathcal{S}^c)=1。

解析

总运动旋量系

Sm=Sb1∪Sb2=span⁡{(1,0,0;0,0,0)(1,0,0;0,a,b)(1,0,0;0,c,d)(0,1,0;0,0,0)(0,1,0;e,0,f)(0,1,0;g,0,h)}=span⁡{(1,0,0;0,0,0)(0,1,0;0,0,0)(0,0,0;e,0,f)(0,0,0;g,0,h)(0,0,0;0,a,b)(0,0,0;0,c,d)}\mathcal{S}_m=\mathcal{S}_{b1} \cup \mathcal{S}_{b2}=\operatorname{span}\left\{\begin{aligned}&(1,0,0;0,0,0)\\&(1,0,0;0,a,b)\\&(1,0,0;0,c,d)\\&(0,1,0;0,0,0)\\&(0,1,0;e,0,f)\\&(0,1,0;g,0,h)\end{aligned}\right\}=\operatorname{span}\left\{\begin{aligned}&(1,0,0;0,0,0)\\&(0,1,0;0,0,0)\\&(0,0,0;e,0,f)\\&(0,0,0;g,0,h)\\&(0,0,0;0,a,b)\\&(0,0,0;0,c,d)\\\end{aligned}\right\}

求解 SmΔ$c=0\mathcal{S}_m \boldsymbol{\Delta} \boldsymbol{\text{\textdollar}}^c = \boldsymbol{0},可得:

Sc=span⁡{(0,0,0;0,0,1)}\mathcal{S}^c=\operatorname{span}\left\{\begin{aligned}&(0,0,0;0,0,1)\\\end{aligned}\right\}

即,公共约束数为dim⁡(Sc)=1\dim(\mathcal{S}^c)=1。

d. 冗余约束分析

根据支链约束旋量系与公共约束旋量系,求该机构的冗余约束数。

答案

⟨Scr⟩=Scr\langle\mathcal{S}^r_c\rangle=\mathcal{S}^r_c,故 ν=0\nu=0,该机构无冗余约束。

解析
⟨Sr⟩=Sb1r⊕Sb2r=span⁡{(1,0,0;0,0,0)(0,0,0;0,1,0)(0,0,0;0,0,1)(0,1,0;0,0,0)(0,0,0;1,0,0)(0,0,0;0,0,1)}\langle\mathcal{S}^r\rangle=\mathcal{S}^{r}_{b1} \oplus \mathcal{S}^{r}_{b2}=\operatorname{span}\left\{\begin{aligned}&(1,0,0;0,0,0)\\&(0,0,0;0,1,0)\\&(0,0,0;0,0,1)\\&(0,1,0;0,0,0)\\&(0,0,0;1,0,0)\\&(0,0,0;0,0,1)\end{aligned}\right\}

由Sr=Sc∪Scr\mathcal{S}^r= \mathcal{S}^c \cup \mathcal{S}^r_c,可得

Scr=span⁡{(1,0,0;0,0,0)(0,0,0;0,1,0)(0,0,0;0,0,1)(0,1,0;0,0,0)(0,0,0;1,0,0)}\mathcal{S}^r_c=\operatorname{span}\left\{\begin{aligned}&(1,0,0;0,0,0)\\&(0,0,0;0,1,0)\\&(0,0,0;0,0,1)\\&(0,1,0;0,0,0)\\&(0,0,0;1,0,0)\\\end{aligned}\right\}

由⟨Sr⟩=Sb1r⊕Sb2r\langle\mathcal{S}^r\rangle = \mathcal{S}^{r}_{b1} \oplus \mathcal{S}^{r}_{b2}可得:

⟨Sr⟩=span⁡{(1,0,0;0,0,0)(0,0,0;0,1,0)(0,0,0;0,0,1)(0,1,0;0,0,0)(0,0,0;1,0,0)(0,0,0;0,0,1)}\langle\mathcal{S}^r\rangle=\operatorname{span}\left\{\begin{aligned}&(1,0,0;0,0,0)\\&(0,0,0;0,1,0)\\&(0,0,0;0,0,1)\\&(0,1,0;0,0,0)\\&(0,0,0;1,0,0)\\&(0,0,0;0,0,1)\end{aligned}\right\}

由⟨Sr⟩=Sc∪⟨Scr⟩\langle\mathcal{S}^r\rangle= \mathcal{S}^c \cup \langle\mathcal{S}^r_c\rangle,可得:

⟨Scr⟩=span⁡{(1,0,0;0,0,0)(0,0,0;0,1,0)(0,0,0;0,0,1)(0,1,0;0,0,0)(0,0,0;1,0,0)}\langle\mathcal{S}^r_c\rangle=\operatorname{span}\left\{\begin{aligned}&(1,0,0;0,0,0)\\&(0,0,0;0,1,0)\\&(0,0,0;0,0,1)\\&(0,1,0;0,0,0)\\&(0,0,0;1,0,0)\\\end{aligned}\right\}

因此,⟨Scr⟩=Scr\langle\mathcal{S}^r_c\rangle=\mathcal{S}^r_c,ν=card⁡(⟨Scr⟩)−dim⁡(Scr)=0\nu = \operatorname{card}(\langle\mathcal{S}^r_c\rangle) - \dim(\mathcal{S}^r_c)=0 ,该机构无冗余约束。

例 2:Scott-Russell 机构分析

a. 前置分析

根据图示 Scott-Russell 机构建立坐标系,划分支链,并写出 OO、AA、BB、CC 四处的运动副旋量。

<Image {...scottRussell} />

答案

各运动副旋量为

$A=(0,0,1;−b,c,0)T,\boldsymbol{\text{\textdollar}}_A=(0,0,1;-b,c,0)^T,$B1=(0,0,0;0,1,0)T,$B2=(0,0,1;−2b,0,0)T,\boldsymbol{\text{\textdollar}}_{B1}=(0,0,0;0,1,0)^T,\quad\boldsymbol{\text{\textdollar}}_{B2}=(0,0,1;-2b,0,0)^T,$C1=(0,0,0;1,0,0)T,$C2=(0,0,1;0,2c,0)T.\boldsymbol{\text{\textdollar}}_{C1}=(0,0,0;1,0,0)^T,\quad\boldsymbol{\text{\textdollar}}_{C2}=(0,0,1;0,2c,0)^T.
解析

Scott-Russell 机构存在 1 个冗余约束与3 个公共约束,下面用旋量法验证。

建立OC⃗\vec{OC}为XX轴,OB⃗\vec{OB}为YY轴,垂直纸面向外为ZZ轴。∣OB⃗∣=2b|\vec{OB}|=2b,∣OC⃗∣=2c|\vec{OC}|=2c。

此机构可以视为一个含3个支链的并联机构。

其中第一条支链为:

机架−>C(移动副滑块)−>C(转动副)−>动杆BC机架->C(移动副滑块)->C(转动副)->动杆BC

第二条支链为:

机架−>O(转动副)−>A(转动副)−>动杆BC机架->O(转动副)->A(转动副)->动杆BC

第三条支链为:

机架−>B(移动副滑块)−>B(转动副)−>动杆BC机架->B(移动副滑块)->B(转动副)->动杆BC

将BB与CC两处的移动副与转动副视为单个自由度为2的高副,合并分析,可以得OO、AA、BB、CC四处的运动副旋量如下

$O=(0,0,1;0,0,0)T\boldsymbol{\text{\textdollar}}_O=(0,0,1;0,0,0)^T$A=(0,0,1;−b,c,0)T\boldsymbol{\text{\textdollar}}_A=(0,0,1;-b,c,0)^T$B1=(0,0,0;0,1,0)T(平动),$B2=(0,0,1;−2b,0,0)T(转动)\boldsymbol{\text{\textdollar}}_{B1}=(0,0,0;0,1,0)^T(平动),\$_{B2}=(0,0,1;-2b,0,0)^T(转动)$C1=(0,0,0;1,0,0)T(平动),$C2=(0,0,1;0,2c,0)T(转动)\boldsymbol{\text{\textdollar}}_{C1}=(0,0,0;1,0,0)^T(平动),\$_{C2}=(0,0,1;0,2c,0)^T(转动)

b. 自由度分析

建立各支链的运动旋量系与约束旋量系,求动平台 BCBC 的运动旋量系、自由度及运动形式。

答案

Sf=span⁡{(0,0,1,−2b,2c,0)}\mathcal{S}_f=\operatorname{span}\{(0,0,1,-2b,2c,0)\},因此 F=1F=1;机构绕过点 (−2c,−2b,0)(-2c,-2b,0)、方向向量为 (0,0,1)(0,0,1) 的轴转动。

解析

分析可得,此机构无局部自由度。

对于各支链,建立运动旋量系Sbi\mathcal{S}_{bi}:

Sb1=span⁡{$B1T$B2T}=span⁡{(0,0,0;0,1,0)(0,0,1;−2b,0,0)}\mathcal{S}_{b1} =\operatorname{span}\left\{\begin{aligned}&\boldsymbol{\text{\textdollar}}_{B1}^T \\&\boldsymbol{\text{\textdollar}}_{B2}^T\end{aligned}\right\}=\operatorname{span}\left\{\begin{aligned}&(0 , 0 , 0 ; 0 , 1 , 0)\\&(0 , 0 , 1 ; -2b , 0 , 0)\end{aligned}\right\}span⁡{$OT$AT}=span⁡{(0,0,1;0,0,0)(0,0,1;−b,c,0)}\operatorname{span}\left\{\begin{aligned}&\boldsymbol{\text{\textdollar}}_{O}^T \\&\boldsymbol{\text{\textdollar}}_{A}^T\end{aligned}\right\}=\operatorname{span}\left\{\begin{aligned}&(0 , 0 , 1 ; 0 , 0 , 0)\\&(0 , 0 , 1 ; -b , c , 0)\end{aligned}\right\}span⁡{$C1T$C2T}=span⁡{(0,0,0;1,0,0)(0,0,1;0,2c,0)}\operatorname{span}\left\{\begin{aligned}&\boldsymbol{\text{\textdollar}}_{C1}^T \\&\boldsymbol{\text{\textdollar}}_{C2}^T\end{aligned}\right\}=\operatorname{span}\left\{\begin{aligned}&(0 , 0 , 0 ; 1 , 0 , 0)\\&(0 , 0 , 1 ; 0 , 2c , 0)\end{aligned}\right\}

求解各支链约束旋量系Sbir\mathcal{S}^{r}_{bi}:

根据

可得

Sb1r=span⁡{(1,0,0; 0,0,2b)(0,0,1; 0,0,0)(0,0,0; 1,0,0)(0,0,0; 0,1,0)}\mathcal{S}_{b1}^{r}=\operatorname{span}\left\{\begin{aligned}&(1,0,0;\ 0,0,2b)\\&(0,0,1;\ 0,0,0)\\&(0,0,0;\ 1,0,0)\\&(0,0,0;\ 0,1,0)\end{aligned}\right\}Sb2r=span⁡{(c,b,0; 0,0,0)(0,0,1; 0,0,0)(0,0,0; 1,0,0)(0,0,0; 0,1,0)}\mathcal{S}_{b2}^{r}=\operatorname{span}\left\{\begin{aligned}&(c,b,0;\ 0,0,0)\\&(0,0,1;\ 0,0,0)\\&(0,0,0;\ 1,0,0)\\&(0,0,0;\ 0,1,0)\end{aligned}\right\}Sb3r=span⁡{(0,1,0; 0,0,−2c)(0,0,1; 0,0,0)(0,0,0; 1,0,0)(0,0,0; 0,1,0)}\mathcal{S}_{b3}^{r}=\operatorname{span}\left\{\begin{aligned}&(0,1,0;\ 0,0,-2c)\\&(0,0,1;\ 0,0,0)\\&(0,0,0;\ 1,0,0)\\&(0,0,0;\ 0,1,0)\end{aligned}\right\}

求动平台BCBC约束旋量系:

根据

Sr=Sb1r∪Sb2r∪⋯∪Sbpr\mathcal{S}^r = \mathcal{S}^{r}_{b1} \cup \mathcal{S}^{r}_{b2} \cup \cdots \cup \mathcal{S}^{r}_{bp}

可得:

Sr=span⁡{(0,0,1; 0,0,0)(0,0,0; 1,0,0)(0,0,0; 0,1,0)(1,0,0; 0,0,2b)(c,b,0; 0,0,0)(0,1,0; 0,0,−2c)}\mathcal{S}^r=\operatorname{span}\left\{\begin{aligned}&(0,0,1;\ 0,0,0)\\&(0,0,0;\ 1,0,0)\\&(0,0,0;\ 0,1,0)\\&(1,0,0;\ 0,0,2b)\\&(c,b,0;\ 0,0,0)\\&(0,1,0;\ 0,0,-2c)\end{aligned}\right\}

由于(1,0,0; 0,0,2b)(1,0,0;\ 0,0,2b)、(c,b,0; 0,0,0)(c,b,0;\ 0,0,0)与(0,1,0; 0,0,−2c)(0,1,0;\ 0,0,-2c)线性相关,因此

{(0,0,1; 0,0,0)(0,0,0; 1,0,0)(0,0,0; 0,1,0)(1,0,0; 0,0,2b)(0,1,0; 0,0,−2c)}\left\{\begin{aligned}&(0,0,1;\ 0,0,0)\\&(0,0,0;\ 1,0,0)\\&(0,0,0;\ 0,1,0)\\&(1,0,0;\ 0,0,2b)\\&(0,1,0;\ 0,0,-2c)\end{aligned}\right\}

化简,消去线性相关元素,可得

span⁡{(1,0,0; 0,0,2b)(0,1,0; 0,0,−2c)(0,0,1; 0,0,0)(0,0,0; 1,0,0)(0,0,0; 0,1,0)}\operatorname{span}\left\{\begin{aligned}&(1,0,0;\ 0,0,2b)\\&(0,1,0;\ 0,0,-2c)\\&(0,0,1;\ 0,0,0)\\&(0,0,0;\ 1,0,0)\\&(0,0,0;\ 0,1,0)\end{aligned}\right\}

求动平台运动旋量系

根据

可得

Sf=span⁡{(0,0,1,−2b,2c,0)}\mathcal{S}_f=\operatorname{span}\left\{ (0,0,1,-2b,2c,0)\right\}

即,此机构仅有F=dim⁡(Sf)=1F = \dim(\mathcal{S}_f)=1个自由度,运动形式是绕轴转动。旋转轴过点(−2c,−2b,0)(-2c,-2b,0),方向向量为(0,0,1)(0,0,1)。

c. 公共约束分析

根据各支链的运动旋量系,求机构的公共约束旋量系与公共约束数。

答案
Sc=span⁡{(0,0,1;0,0,0),(0,0,0;1,0,0),(0,0,0;0,1,0)},λ=3.\mathcal{S}^c=\operatorname{span}\left\{(0,0,1;0,0,0),(0,0,0;1,0,0),(0,0,0;0,1,0)\right\},\qquad\lambda=3.
解析

根据上文的Sbi\mathcal{S}_{bi},可得机构总运动旋量系 Sm\mathcal{S}_m:

Sm=span⁡{$B1T$B1T$OT$AT$C1T$C2T}=span⁡{(0,0,0;0,1,0)(0,0,1;−2b,0,0)(0,0,1;0,0,0)(0,0,1;−b,c,0)(0,0,0;1,0,0)(0,0,1;0,2c,0)}\mathcal{S}_{m} =\operatorname{span}\left\{\begin{aligned}&\boldsymbol{\text{\textdollar}}_{B1}^T\\&\boldsymbol{\text{\textdollar}}_{B1}^T\\&\boldsymbol{\text{\textdollar}}_O^T \\&\boldsymbol{\text{\textdollar}}_A^T\\&\boldsymbol{\text{\textdollar}}_{C1}^T \\&\boldsymbol{\text{\textdollar}}_{C2}^T\end{aligned}\right\}=\operatorname{span}\left\{\begin{aligned}&(0 , 0 , 0 ; 0 , 1 , 0)\\&(0 , 0 , 1 ; -2b , 0 , 0)\\&(0 , 0 , 1 ; 0 , 0 , 0)\\&(0 , 0 , 1 ; -b , c , 0)\\&(0 , 0 , 0 ; 1 , 0 , 0)\\&(0 , 0 , 1 ; 0 , 2c , 0)\end{aligned}\right\}

根据:

可得:

Sc=span⁡{(0,0,1; 0,0,0)(0,0,0; 1,0,0)(0,0,0; 0,1,0)}\mathcal{S}^c=\operatorname{span}\left\{\begin{aligned}&(0,0,1;\ 0,0,0)\\&(0,0,0;\ 1,0,0)\\&(0,0,0;\ 0,1,0)\end{aligned}\right\}

公共约束数:

λ=dim⁡(Sc)=3\lambda = \dim(\mathcal{S}^c)=3

d. 冗余约束分析

根据各支链约束旋量系及公共约束旋量系,求该机构的冗余约束数。

答案

card⁡(⟨Scr⟩)=3\operatorname{card}(\langle\mathcal{S}^r_c\rangle)=3,dim⁡(Scr)=2\dim(\mathcal{S}^r_c)=2,故 ν=1\nu=1。

解析

由Sbir\mathcal{S}^{r}_{bi}可得:

⟨Sr⟩=Sb1r⊕Sb2r⊕⋯⊕Sbpr=span⁡{(0,0,1; 0,0,0)(0,0,0; 1,0,0)(0,0,0; 0,1,0)(1,0,0; 0,0,2b)(c,b,0; 0,0,0)(0,1,0; 0,0,−2c)}\langle\mathcal{S}^r\rangle=\mathcal{S}^{r}_{b1} \oplus \mathcal{S}^{r}_{b2} \oplus \cdots \oplus \mathcal{S}^{r}_{bp}=\operatorname{span}\left\{\begin{aligned}&(0,0,1;\ 0,0,0)\\&(0,0,0;\ 1,0,0)\\&(0,0,0;\ 0,1,0)\\&(1,0,0;\ 0,0,2b)\\&(c,b,0;\ 0,0,0)\\&(0,1,0;\ 0,0,-2c)\end{aligned}\right\}span⁡{(0,0,1; 0,0,0)(0,0,0; 1,0,0)(0,0,0; 0,1,0)(1,0,0; 0,0,2b)(0,1,0; 0,0,−2c)}\operatorname{span}\left\{\begin{aligned}&(0,0,1;\ 0,0,0)\\&(0,0,0;\ 1,0,0)\\&(0,0,0;\ 0,1,0)\\&(1,0,0;\ 0,0,2b)\\&(0,1,0;\ 0,0,-2c)\end{aligned}\right\}

因此,由

与

⟨Sr⟩=Sc⊕⟨Scr⟩\langle\mathcal{S}^r\rangle = \mathcal{S}^c \oplus \langle\mathcal{S}^r_c\rangle

可得

Scr=span⁡{(1,0,0; 0,0,2b)(0,1,0; 0,0,−2c)}\mathcal{S}^r_c=\operatorname{span}\left\{\begin{aligned}&(1,0,0;\ 0,0,2b)\\&(0,1,0;\ 0,0,-2c)\end{aligned}\right\}⟨Scr⟩=span⁡{(1,0,0; 0,0,2b)(c,b,0; 0,0,0)(0,1,0; 0,0,−2c)}\langle\mathcal{S}^r_c\rangle=\operatorname{span}\left\{\begin{aligned}&(1,0,0;\ 0,0,2b)\\&(c,b,0;\ 0,0,0)\\&(0,1,0;\ 0,0,-2c)\end{aligned}\right\}

即得冗余约束数ν\nu:

ν=card⁡(⟨Scr⟩)−dim⁡(Scr)=1\nu = \operatorname{card}(\langle\mathcal{S}^r_c\rangle) - \dim(\mathcal{S}^r_c)=1