运用DH参数法时坐标系建立的两个约定：
（1）x_i与z_(i-1)垂直
（2）x_i与z_(i-1)相交
坐标系i与坐标系i-1的其次变换矩阵为：
a为两z轴的距离，d为两x轴的距离。
alpha与theta的正方向约定为：
下面举三个例子：
a、平面二自由度机器人
clear;
clc;
syms theta1 alpha1 a1 d1 theta2 alpha2 a2 d2 a b theta d;
A1=[cos(theta1),-sin(theta1)*cos(alpha1),sin(theta1)*sin(alpha1),a1*cos(theta1);...
sin(theta1),cos(theta1)*cos(alpha1),-cos(theta1)*sin(alpha1),a1*sin(theta1);...
0,sin(alpha1),cos(alpha1),d1;...
0,0,0,1];
A2=[cos(theta2),-sin(theta2)*cos(alpha2),sin(theta2)*sin(alpha2),a2*cos(theta2);...
sin(theta2),cos(theta2)*cos(alpha2),-cos(theta2)*sin(alpha2),a2*sin(theta2);...
0,sin(alpha2),cos(alpha2),d2;...
0,0,0,1];
L=sqrt(a^2+b^2);
beta=atan(b/a);
a1=L;
alpha1=sym(0);
d1=sym(0);
theta1=theta;
a2=d;
alpha2=sym(0);
d2=sym(0);
theta2=-beta;
T=eval_r(A1*A2)
求得运动学正解为：
b、平面三自由度机器人
clear;
clc;
syms theta1 alpha1 a1 d1 theta2 alpha2 a2 d2 theta3 alpha3 a3 d3 d;
A1=[cos(theta1),-sin(theta1)*cos(alpha1),sin(theta1)*sin(alpha1),a1*cos(theta1);...
sin(theta1),cos(theta1)*cos(alpha1),-cos(theta1)*sin(alpha1),a1*sin(theta1);...
0,sin(alpha1),cos(alpha1),d1;...
0,0,0,1];
A2=[cos(theta2),-sin(theta2)*cos(alpha2),sin(theta2)*sin(alpha2),a2*cos(theta2);...
sin(theta2),cos(theta2)*cos(alpha2),-cos(theta2)*sin(alpha2),a2*sin(theta2);...
0,sin(alpha2),cos(alpha2),d2;...
0,0,0,1];
A3=[cos(theta3),-sin(theta3)*cos(alpha3),sin(theta3)*sin(alpha3),a3*cos(theta3);...
sin(theta3),cos(theta3)*cos(alpha3),-cos(theta3)*sin(alpha3),a3*sin(theta3);...
0,sin(alpha3),cos(alpha3),d3;...
0,0,0,1];
alpha1=sym(0);
d1=sym(0);
a2=d;
alpha2=sym(0);
d2=sym(0);
theta2=sym(0);
alpha3=sym(0);
d3=sym(0);
theta3=-theta3;
T=eval_r(A1*A2*A3)
求得运动学正解为：
c、六自由度机器人
clear;
clc;
syms theta1 alpha1 a1 d1 theta2 alpha2 a2 d2 theta3 alpha3 a3 d3 ...
theta4 alpha4 a4 d4 theta5 alpha5 a5 d5 theta6 alpha6 a6 d6;
A1=[cos(theta1),-sin(theta1)*cos(alpha1),sin(theta1)*sin(alpha1),a1*cos(theta1);...
sin(theta1),cos(theta1)*cos(alpha1),-cos(theta1)*sin(alpha1),a1*sin(theta1);...
0,sin(alpha1),cos(alpha1),d1;...
0,0,0,1];
A2=[cos(theta2),-sin(theta2)*cos(alpha2),sin(theta2)*sin(alpha2),a2*cos(theta2);...
sin(theta2),cos(theta2)*cos(alpha2),-cos(theta2)*sin(alpha2),a2*sin(theta2);...
0,sin(alpha2),cos(alpha2),d2;...
0,0,0,1];
A3=[cos(theta3),-sin(theta3)*cos(alpha3),sin(theta3)*sin(alpha3),a3*cos(theta3);...
sin(theta3),cos(theta3)*cos(alpha3),-cos(theta3)*sin(alpha3),a3*sin(theta3);...
0,sin(alpha3),cos(alpha3),d3;...
0,0,0,1];
A4=[cos(theta4),-sin(theta4)*cos(alpha4),sin(theta4)*sin(alpha4),a4*cos(theta4);...
sin(theta4),cos(theta4)*cos(alpha4),-cos(theta4)*sin(alpha4),a4*sin(theta4);...
0,sin(alpha4),cos(alpha4),d4;...
0,0,0,1];
A5=[cos(theta5),-sin(theta5)*cos(alpha5),sin(theta5)*sin(alpha5),a5*cos(theta5);...
sin(theta5),cos(theta5)*cos(alpha5),-cos(theta5)*sin(alpha5),a5*sin(theta5);...
0,sin(alpha5),cos(alpha5),d5;...
0,0,0,1];
A6=[cos(theta6),-sin(theta6)*cos(alpha6),sin(theta6)*sin(alpha6),a6*cos(theta6);...
sin(theta6),cos(theta6)*cos(alpha6),-cos(theta6)*sin(alpha6),a6*sin(theta6);...
0,sin(alpha6),cos(alpha6),d6;...
0,0,0,1];
a1=sym(0);
alpha1=sym(-pi/2);
alpha2=sym(0);
d2=sym(0);
a3=sym(0);
alpha3=sym(-pi/2);
d3=sym(0);
a4=sym(0);
alpha4=sym(-pi/2);
d4=sym(0);
a5=sym(0);
alpha5=sym(pi/2);
d5=sym(0);
a6=sym(0);
alpha6=sym(0);
T=simplify(eval_r(A1*A2*A3*A4*A5*A6))
注：以上的eval_r为eval（不知道为什么，保存后“eval”就变成“eval_r”了）
from:http://blog.sina.com.cn/u/2707887295