基于二进制编码遗传算法的 PID 整定是通过二进制字符串表示 KpK_pKp、KiK_iKi、KdK_dKd 参数的优化方法。该方法利用遗传算法优化性能指标,从而整定 PID 控制器。
1. 方法原理
遗传算法的核心包括:
- 编码方式:使用二进制字符串表示 PID 参数。
- 目标函数:定义一个性能指标(如 ITAE)来评估 PID 控制器的效果。
- 遗传操作:包括选择、交叉、变异,逐步改进种群的适应度。
2. 实现步骤
3. C++ 实现代码
头文件与全局变量
#include <iostream>
#include <vector>
#include <string>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <algorithm>
using namespace std;
const int bitLength = 10; // 每个参数的二进制长度
const int populationSize = 50; // 种群规模
const int maxGenerations = 100; // 最大代数
const double crossoverRate = 0.8; // 交叉概率
const double mutationRate = 0.05; // 变异概率
// PID 参数范围
const double Kp_min = 0.1, Kp_max = 10.0;
const double Ki_min = 0.1, Ki_max = 5.0;
const double Kd_min = 0.01, Kd_max = 1.0;
编码与解码
// 二进制编码为实数
double binaryToReal(const string& binary, double minVal, double maxVal) {
int decimal = stoi(binary, nullptr, 2);
return minVal + (maxVal - minVal) * decimal / (pow(2, bitLength) - 1);
}
// 实数编码为二进制
string realToBinary(double value, double minVal, double maxVal) {
int decimal = round((value - minVal) / (maxVal - minVal) * (pow(2, bitLength) - 1));
string binary = bitset<bitLength>(decimal).to_string();
return binary;
}
个体与目标函数
struct Individual {
string Kp_binary;
string Ki_binary;
string Kd_binary;
double fitness;
};
// 模拟目标函数计算 ITAE
double objectiveFunction(double Kp, double Ki, double Kd) {
// 示例:假设一个误差模型
double e = 0.0;
double ITAE = 0.0;
for (double t = 0; t <= 10.0; t += 0.1) {
e = exp(-Kp * t) * sin(Ki * t) + cos(Kd * t);
ITAE += t * fabs(e) * 0.1;
}
return ITAE;
}
初始化种群
void initializePopulation(vector<Individual>& population) {
for (int i = 0; i < populationSize; ++i) {
double Kp = Kp_min + (Kp_max - Kp_min) * rand() / RAND_MAX;
double Ki = Ki_min + (Ki_max - Ki_min) * rand() / RAND_MAX;
double Kd = Kd_min + (Kd_max - Kd_min) * rand() / RAND_MAX;
population.push_back({
realToBinary(Kp, Kp_min, Kp_max),
realToBinary(Ki, Ki_min, Ki_max),
realToBinary(Kd, Kd_min, Kd_max),
0.0
});
}
}
遗传算法主循环
void geneticAlgorithm() {
vector<Individual> population;
initializePopulation(population);
for (int generation = 0; generation < maxGenerations; ++generation) {
// 评估适应度
for (auto& individual : population) {
double Kp = binaryToReal(individual.Kp_binary, Kp_min, Kp_max);
double Ki = binaryToReal(individual.Ki_binary, Ki_min, Ki_max);
double Kd = binaryToReal(individual.Kd_binary, Kd_min, Kd_max);
individual.fitness = 1.0 / (1.0 + objectiveFunction(Kp, Ki, Kd));
}
// 选择(轮盘赌)
vector<Individual> newPopulation;
while (newPopulation.size() < populationSize) {
int i = rand() % populationSize;
int j = rand() % populationSize;
newPopulation.push_back(population[i].fitness > population[j].fitness ? population[i] : population[j]);
}
// 交叉
for (int i = 0; i < newPopulation.size(); i += 2) {
if (rand() / double(RAND_MAX) < crossoverRate && i + 1 < newPopulation.size()) {
int crossoverPoint = rand() % bitLength;
swap_ranges(newPopulation[i].Kp_binary.begin() + crossoverPoint,
newPopulation[i].Kp_binary.end(),
newPopulation[i + 1].Kp_binary.begin() + crossoverPoint);
}
}
// 变异
for (auto& individual : newPopulation) {
if (rand() / double(RAND_MAX) < mutationRate) {
int mutationPoint = rand() % bitLength;
individual.Kp_binary[mutationPoint] = individual.Kp_binary[mutationPoint] == '0' ? '1' : '0';
}
}
population = newPopulation;
}
// 输出最优解
auto best = *max_element(population.begin(), population.end(),
[](const Individual& a, const Individual& b) { return a.fitness < b.fitness; });
double Kp = binaryToReal(best.Kp_binary, Kp_min, Kp_max);
double Ki = binaryToReal(best.Ki_binary, Ki_min, Ki_max);
double Kd = binaryToReal(best.Kd_binary, Kd_min, Kd_max);
cout << "Optimal PID parameters: Kp=" << Kp << ", Ki=" << Ki << ", Kd=" << Kd << endl;
}
运行程序
int main() {
srand(time(nullptr));
geneticAlgorithm();
return 0;
}
4. 总结
- 二进制编码优势:简单易实现,适合标准遗传算法框架。
- 参数优化:通过 ITAE 等性能指标优化 KpK_pKp、KiK_iKi、KdK_dKd。
- 扩展性:可以调整目标函数和遗传参数适应不同场景。