Question

我试图模拟一个蹦极跳，给定主体的质量，弹力绳的弹簧常数，绳索的初始长度，以及找到加速度，速度和距离下降所需的其他值。学科。我必须使用基本类和算术才能完成这个项目。

这是我创建的课程：

#include "FallingObject.h"
#include <cmath>
#include <iostream>

using namespace std;

FallingObject::FallingObject(float mass, float surfaceArea, float bungeeSpringConstant, float      bungeeUnstretchedLength) {
    this->mass = mass;
    this->surfaceArea = surfaceArea;
    this->bungeeSpringConstant = bungeeSpringConstant;
    this->bungeeUnstretchedLength = bungeeUnstretchedLength;
}
float FallingObject::getMass(){
    return this->mass;
}
float FallingObject::getSurfaceArea(){
    return this->surfaceArea;
}
float FallingObject::getBungeeSpringConstant(){
    return this->bungeeSpringConstant;
}
float FallingObject::getBungeeUnstretchedLength(){
    return this->bungeeUnstretchedLength;
}
void FallingObject::simulateTimeStep(float deltaT){

    float g = 9.81, timeStep = 0.0;
    float fWeight, fFriction, fSpring, fTotal;
    float currentV, currentD, currentA;
    velocity = 0.0;
    distance = 0.0;
    acceleration = 0.0;


    //Acceleration @ timeStep = 0:
    fWeight = mass * g;
    fFriction = (-0.65) * surfaceArea * velocity * abs(velocity);
    fSpring = (-1) * bungeeSpringConstant * distance;
    fTotal = fWeight + fFriction + fSpring;
    currentA = fTotal / mass;


    //Velocity @ timeStep = 0
    currentV = acceleration * timeStep;


    //Distance @ timeStep = 0
    currentD = velocity * timeStep;


    //increment values
    timeStep += deltaT;
    acceleration += currentA;
    velocity += currentV;
    distance += currentD;


}
float FallingObject::getFallDistance(){
    return this->distance;
}
float FallingObject::getVelocity(){
    return this->velocity;
}
float FallingObject::getAcceleration(){
    return this->acceleration;
}

这是主要功能：

int _tmain(int argc, _TCHAR* argv[])
{
   // arguments in order:
   // mass (70kg)
   // surface area (0.2m^2)
   // spring constant for the bungee cord (21.7)
   // unstretched length of bungee cord (30m)
   FallingObject fallingObject(70.0f, 0.2f, 21.7f, 30.0f);

   vector<float> elapsedTimes;
   vector<float> distances;
   vector<float> velocities;
   vector<float> accelerations;

   ofstream outFile("bungee_data.txt");

   // time step zero
   elapsedTimes.push_back(0.0f);
   distances.push_back(fallingObject.getFallDistance());
   velocities.push_back(fallingObject.getVelocity());
   accelerations.push_back(fallingObject.getAcceleration());

   float simulationTime = 60; // 60 seconds
   float deltaT = 0.01;       // 0.01 seconds
   int timeSteps = (int)(simulationTime / deltaT);

   for (unsigned int t = 1; t < timeSteps; t++) {
       fallingObject.simulateTimeStep(deltaT);
       elapsedTimes.push_back(t * deltaT);
       distances.push_back(fallingObject.getFallDistance());
       velocities.push_back(fallingObject.getVelocity());
       accelerations.push_back(fallingObject.getAcceleration());


   }

   for (int i = 0; i < timeSteps; i++){
       outFile << elapsedTimes[i] << ",";
       outFile << distances[i] << ",";
       outFile << velocities[i] << ",";
       outFile << accelerations[i] << endl;
   }



   return 0;
}

我遇到的问题是值没有更新，我无法确定原因。

任何人都可以对此问题提供一些帮助吗？

Answer 1

您正在使用timeStep执行计算，deltaT是函数的本地计算，并且每次调用时都设置为零。

由于currentV = acceleration * deltaT; currentD = velocity * deltaT; 是时间步，所以只需使用：

deltaT

（如果您要继续将velocity = 0.0; distance = 0.0; acceleration = 0.0;添加到＆＃34;时间步骤＆＃34;，它将不是一个步骤，而是总耗用时间。）

您还会在每次通话时重置这些变量：

{{1}}

Answer 2

每次FallingObject::simulateTimeStep来电，您都会重置状态描述值velocity和distance。你必须永久保存它们。

模拟蹦极跳[C ++]

2 个答案: