clear all; clc; du = pi/180; a = [0+0.001, 185+0.0079, 0+0.005, 120+0.12]; alpha = [pi/2+0.003, 0+0.001, pi/2+0.005, pi/2]; d = [0+0.001, 0+0.0079, 90+0.005, 0+0.12]; theta = [90du+0.02, 0, 0.023, 0.08]; beta = zeros(1, 4)+0; L1(1) = Link('d', d(1), 'a', a(1), 'alpha', alpha(1), 'qlim', [180du, 365du], 'modified'); L1(2) = Link('d', d(2), 'a', a(2), 'alpha', alpha(2), 'qlim', [3du, 63du], 'modified'); L1(3) = Link('d', d(3), 'a', a(3), 'alpha', alpha(3), 'qlim', [60du, 120du], 'modified'); L1(4) = Link('d', d(4), 'a', a(4), 'alpha', alpha(4), 'qlim', [230du, 326*du], 'modified'); Needle = SerialLink(L1, 'name', 'Needle'); T1 = DH(1, a(1), alpha(1), d(1), theta(1)+beta(1)); T2 = DH(2, a(2), alpha(2), d(2), theta(2)+beta(2)); T3 = DH(3, a(3), alpha(3), d(3), theta(3)+beta(3)); T4 = DH(4, a(4), alpha(4), d(4), theta(4)+beta(4)); T = T1 * T2 * T3 * T4; % Step 2：利用微分变换原理计算机器人各个连杆机构之间的微小原始偏差 delta_a = 0.001; % a参数的微小偏差 delta_T1 = DH(1, a(1)+delta_a, alpha(1), d(1), theta(1)+beta(1)) - T1; delta_T2 = DH(2, a(2)+delta_a, alpha(2), d(2), theta(2)+beta(2)) - T2; delta_T3 = DH(3, a(3)+delta_a, alpha(3), d(3), theta(3)+beta(3)) - T3; delta_T4 = DH(4, a(4)+delta_a, alpha(4), d(4), theta(4)+beta(4)) - T4; % Step 3：计算误差矩阵 delta_T = delta_T1 * delta_T2 * delta_T3 * delta_T4; % Step 4：将误差矩阵转化为误差值 delta_theta = delta_T * [0; 0; 0; 1]; % 误差值这段代码帮我继续编写得到末端位姿误差，基于修DH模型对机器人进行运行学建模，存在几何参数有a，α，d，θ和β。当这些参数存在微小误差时，机器人的实际相邻连杆之间的变换关系和理论相邻连杆之间变换关系会存在一定的偏差，导致最后实际和理论的末端位姿坐标也存在误差，分别用 Δa、Δα、 Δd,、 Δθ;和 Δβ;来表示MD-H模型中的五个几何参数误差。利用微分变换原理将机器人各个连杆机构之间的微小原始偏差合成积累到末端位姿的误差视为各个连杆机构进行微分变换综合作用导致的结果，基于MD-H运动学模型建立误差模型，由于各个连杆机构都存在几何参数的误差，机器人的相邻连杆之间的变换矩阵也存在着微小偏差，根据微分运动变换原理，连杆之间的实际变换矩阵和理论变换矩阵存在一定关系。 帮我用MATLAB实现结合我做建立的机器人模型和DH参数，建立误差模型。

以下是基于DH参数建立机器人误差模型的MATLAB代码：

% Step 1: 定义机器人模型
clear all; clc;
du = pi/180;
a = [0+0.001, 185+0.0079, 0+0.005, 120+0.12];
alpha = [pi/2+0.003, 0+0.001, pi/2+0.005, pi/2];
d = [0+0.001, 0+0.0079, 90+0.005, 0+0.12];
theta = [90*du+0.02, 0, 0.023, 0.08];
beta = zeros(1, 4)+0;
L1(1) = Link('d', d(1), 'a', a(1), 'alpha', alpha(1), 'qlim', [180*du, 365*du], 'modified');
L1(2) = Link('d', d(2), 'a', a(2), 'alpha', alpha(2), 'qlim', [3*du, 63*du], 'modified');
L1(3) = Link('d', d(3), 'a', a(3), 'alpha', alpha(3), 'qlim', [60*du, 120*du], 'modified');
L1(4) = Link('d', d(4), 'a', a(4), 'alpha', alpha(4), 'qlim', [230*du, 326*du], 'modified');
Needle = SerialLink(L1, 'name', 'Needle');

% Step 2: 计算误差模型
delta_a = 0.001; % a参数的微小偏差
delta_alpha = 0.001; % alpha参数的微小偏差
delta_d = 0.001; % d参数的微小偏差
delta_theta = 0.001; % theta参数的微小偏差
delta_beta = 0.001; % beta参数的微小偏差

% 将机器人的DH参数加上微小偏差
a_delta = a + [delta_a, 0, 0, 0];
alpha_delta = alpha + [0, delta_alpha, 0, 0];
d_delta = d + [0, delta_d, 0, 0];
theta_delta = theta + [delta_theta, 0, 0, 0];
beta_delta = beta + [delta_beta, delta_beta, delta_beta, delta_beta];

% 计算机器人各个连杆机构之间的微小原始偏差
T1 = DH(1, a(1), alpha(1), d(1), theta(1)+beta(1));
T2 = DH(2, a(2), alpha(2), d(2), theta(2)+beta(2));
T3 = DH(3, a(3), alpha(3), d(3), theta(3)+beta(3));
T4 = DH(4, a(4), alpha(4), d(4), theta(4)+beta(4));
T1_delta = DH(1, a_delta(1), alpha_delta(1), d_delta(1), theta_delta(1)+beta_delta(1));
T2_delta = DH(2, a_delta(2), alpha_delta(2), d_delta(2), theta_delta(2)+beta_delta(2));
T3_delta = DH(3, a_delta(3), alpha_delta(3), d_delta(3), theta_delta(3)+beta_delta(3));
T4_delta = DH(4, a_delta(4), alpha_delta(4), d_delta(4), theta_delta(4)+beta_delta(4));
delta_T1 = T1_delta - T1;
delta_T2 = T2_delta - T2;
delta_T3 = T3_delta - T3;
delta_T4 = T4_delta - T4;

% 计算误差矩阵
delta_T = delta_T1 * delta_T2 * delta_T3 * delta_T4;

% 将误差矩阵转换为误差值
delta_X = delta_T * [0; 0; 0; 1];

% 输出末端位姿误差
fprintf('机器人末端位姿误差为：\n');
fprintf('△X = %f mm\n', delta_X(1:3)*1000); % 将单位从m转换为mm
fprintf('△Y = %f mm\n', delta_X(4:6)*1000); % 将单位从m转换为mm