Preface

 

The story starts with this picture

After choosing the energy storage car with power generation function in question I, I drew this soul drawing that morning:

 

 

 

I joked that Guoyi was stable (directly confident)

The two teammates were already laughing when they saw it.
However, at this time, I had already selected all the accessories.

I built the 3D model in the evening:

 

 

(First version, later the wheelbase of the driving wheel was changed)

The teammate who was on the previous cover didn’t understand my idea at first. When she saw this picture, she said directly:

Can it still be like this?

When the teacher saw it, he said:

Ha ha ha ha

Final product:

 

 

 

Curious? Continue reading~

 

Team introduction

 

Project Analysis

 

After reading the title, I started brainstorming.

      According to my understanding, the focus of this question is to maximize the power generation, because the car uses wheels to travel.

Because the impact of friction caused by weight is small, at this time, to a certain extent, you should try to choose a high-power generator to bring higher benefits.

     Secondly, the power generation part and the driving part must be separated (don’t doge me)

     Because the generator requires a higher speed and a larger deceleration, the generator is used to drive it at this time.

Not to mention that the motor parameters required for power generation and drive are very different, and the efficiency of the gearbox with a large reduction ratio is also very low.

    When I first saw the title, I first thought of a one-way clutch, using the same wheel to generate electricity and drive, and using two sets of gearboxes and motors (later I didn’t think about the structure carefully)

Then it suddenly occurred to me that the title didn't say it couldn't be separated. Then I thought that the generator mechanism could be placed on the top of the car and the driving motor on the bottom. This solved the problem very well (I suddenly felt confident) and I drew this soul drawing.

    Next is the time to find a generator. I feel that if the structure is arranged properly, a hand-operated generator is a very good choice.

Using a 7CM diameter wheel, the sliding speed is very close to the normal hand cranking speed. After some searching,

    I found a great motor (later it turned out that the power generation power was seriously falsely marked). The standard one was 5w (the final calculation was 0.75W) gan!

Then I thought of a structure that can face the generators, so that the number of generators can be increased.

It is driven by a wheel in the middle. I searched the size chart and found that it can fit on a 10*15cm perforated board.

I immediately customized 20*60*1mm aluminum with unequal corners to fix the generator.

The next step is to design a specific plan

 

Control circuit selection

Option 1: Use ARM - 3 28 series as the control core.

Advantages: This type of microcontroller is cheap, has abundant network resources and is easy to find relevant information, is easy to develop and integrate, has low power consumption, and is easier and more convenient to use.

Option 2: Use the STM32 series as the control core.

Advantages: strong computing power, high stability, large number of ports, suitable for engineering applications.

Disadvantages: high cost, high operating threshold and a certain amount of knowledge required.

Option 3: Use RP2040 chip as the control core

Advantages: It has two fast CPU cores , a large amount of RAM , which can make full use of system performance, flexible I/O , and is petite and powerful.

Disadvantages: Large power consumption, relatively new product release time, stability not fully verified, few resources about this chip

In the end we chose 328 as the main controller

Charging solution selection

Power generation method selection

  Option 1: Simultaneous charging and discharging (using the same set of motors to generate electricity and drive the car)

  Option 2: Use two different sets of motors for power generation and driving

(1)  Use the clutch to switch two sets of motors

(2)  Two sets of motors are placed on both sides of the car to generate electricity and drive respectively.

In the end we chose to place it on both sides

1.2.2 Generator model selection

     Option 1: T T motor

 Disadvantages: The motor has small power generation capacity, low voltage, low efficiency, and serious magnetic leakage.

   Option 2: Three-phase AC brushless motor ( 0 19 - 026 )

 Advantages: The motor is small in size, lighter in weight, has a large power generation capacity and is more efficient. Brushless makes the loss lower and reduces the electrical loss.

In the end we chose a brushless generator

Energy storage solution selection

  Option 1: Supercapacitors in parallel (low voltage)

 Charging the capacitor requires reducing the voltage, while discharging the capacitor requires increasing the voltage. This solution increases the loss of electrical energy.

In addition, the input voltage threshold of commercially available boost chips is generally 2 V , which will cause insufficient discharge of the capacitor and waste available power.

  Option 2: Supercapacitors in series (high voltage)

By selecting a supercapacitor that matches the generator voltage of the motor,

There is no need to reduce the voltage during the charging process, which improves the efficiency of electric energy utilization.

Finally we chose the high voltage solution (16.5v 1f)

Coin detection circuit selection

 Solution 1: Capacitive proximity switch

Advantages : high accuracy, large-scale measurement with high resolution, dynamic measurement, easy automation of measurement and data processing, and strong anti-interference ability.

  Option 2: Inductive proximity switch

Advantages: simple structure, stable and reliable, high sensitivity.

Disadvantages: The sensor response frequency is low and is not suitable for fast dynamic measurement. The resolution is greatly affected by the measurement range.

  In the end, we chose inductive proximity, because we could keep the sensor attached to the line, and the range was small, so it could detect coins placed close to each other (we also considered putting two coins together at the time)

Car material selection

 Option 1: Use copper materials to make models

Advantages: good stability and strong support.

Disadvantages: Increases the weight of the vehicle body, reduces vehicle speed, and increases power consumption.

  Option 2: Use aluminum materials to make models

Advantages: small weight, less load on the car, making the car body lighter, high stability and strong fixation.

  this. . . If you have the money, just install aluminum screws (a sequelae of playing time travel). I have to say that the anodizing is really nice. The green and purple color scheme of Unit 1 hehehe

Overall solution description

In this design, power generation and driving are divided into two parts, with independent functions. The drive uses a three-phase AC brushless motor.

The weight of the car body is reduced, the power generation capacity is expanded, and the power loss is reduced. In terms of energy storage, supercapacitors are connected in series.

Greatly improves power utilization, the coin detection circuit uses capacitive proximity switches.

It has a simple structure, high sensitivity when identifying coins, and the detection circuit and tracking are both controlled by a single-chip microcomputer. This design optimizes all aspects of functionality to the highest level.

Theoretical analysis and calculation

The following methods are used to improve system efficiency:

 Voltage matching

The power generation part is designed to use a three-phase AC brushless motor ( 019-026 ) . According to experiments, the rated power generation voltage of the generator is 15V .

After consulting the information, the supercapacitor charging voltage must not exceed 5% of the rated voltage (minimum capacitor voltage: 14.3V ),

因此我们选择将6枚2.7V超级电容串联为16.2V超级电容作为本设计的储能元件。

由于单片机控制系统工作电压为5V，选择高效率的LM2596降压模块给超级电容进行降压。

驱动部分设计采用空心杯减速电机（GA1215R），额定功率0.65W，额定转速89RPM。

根据

Tn=6.974N

电容容量匹配

设计采用四个三相交流无刷电机（019-026），满载功率为2.5W，故总发电功率为10W。在理想工作状态下，发电时间为20S。

所以可得

W=Pt

W_理想=1020S=200J

 根据理想发电能量及电容器能量计算公式得

C=1.52F

由于电容器为6枚2.7V3F超级电容串联根据

C=0.5F

所以可得选择电容器参数应为2.7F

（3）检测电路的低功耗设计

检测电路采用在同等精度下功耗更低的电容式接近传感器，及红外对射循迹模块，

同时因为在测试过程中，部分传感器仅在短时间需要工作，

在本项目中，针对性设计了检测完成后完全断电的电路系统，避免了传感器在不工作的状态下继续耗电的情况。

（4）结构轻量化设计

由于本设计功能较多，需要安装的零件多，为提高小车的效率，需要对车体进行减重，

因此采用铝合金来固定车身（若使用螺丝重量为73g，铝合金为20g）

 

原理电路分析

 

主电路图

驱动电路

检测电路

 

PCB分析

 

我们的主控核心板是自己打样制作的，具体的电路和PCB放在了工程文件，需要可以自取

其实用普通的NANO同样可以实现控制功能

单纯为了好看

 

实物展示

 

程序设计

 

部分代码展示

void loop()

{

  if(s>s_old)

  {

    sp=90;

    s_old=s;

    t[2]=millis();

  }

  else if((millis()-t[0])>100)

  {

    sp+=5;

    t[2]=millis();

  }/////////////////////////////判断小车是否启动

  if(moto==0)

  {

    delay(800);

    moto=1;

    li[0]=digitalRead(8);

    li[1]=digitalRead(7);

    if(!li[0] && !li[1] )  //左右都没有检测到黑线

    {

      analogWrite(9,sp);

      analogWrite(10,sp);

    }

 

     if(li[0])           //右边检测到黑线

    {

      analogWrite(9,sp);

      analogWrite(10,0);

    }

 

    if(li[1])           //左边检测到黑线

    {

      analogWrite(9,0);

      analogWrite(10,sp);

    }

    if(li[0] && li[1] )  //左右都没有检测到黑线

    {

      analogWrite(9,0);

      analogWrite(10,0);

    }

    

  }

  else

  {

    li[0]=digitalRead(8);

    li[1]=digitalRead(7);

    if(!li[0] && !li[1] )  //左右都没有检测到黑线

    {

      analogWrite(9,sp);

      analogWrite(10,sp);

    }

 

    if(li[0])             //右边检测到黑线

    {

      analogWrite(9,sp);

      analogWrite(10,0);

    }

 

    if(li[1])            //左边检测到黑线

    {

      analogWrite(9,0);

      analogWrite(10,sp);

    }

    if(li[0] && li[1])  //左右都没有检测到黑线

    {

      analogWrite(9,0);

      analogWrite(10,0);

    }

  }////////////////////////////////////延时启动程序段

  if(j>x)

  { digitalWrite(4, HIGH);

    t[3]=millis();

    if((millis()-t[3])>300)

    {

      digitalWrite(4, LOW);

      x=j;

    }

  }////////////////////////////////////识别硬币点亮LED

  lcd.setCursor(3,0);

  lcd.print(j);

  Serial.println(j);///////////////////显示硬币数量

  lcd.setCursor(3,1);

  int d=s*3;

  lcd.print(d);

  Serial.println(d);///////////////////显示行进距离

 

}

 

材料清单

 

元件名称	数量（个）
三相交流无刷电机（019-026）	4
空心杯减速电机（GA1215R）（淘宝搜索型号购买即可）	2
LJC18A3电容式接近传感器（淘宝搜索型号购买即可）	1
2.7V10F超级电容（淘宝搜索型号购买即可）	6
LM393N电机驱动（淘宝搜索型号购买即可）	1
LCD1602灰膜（淘宝搜索型号购买即可）	1
TK-01循迹模块	2
3D printed power wheel (STL file attached)	2
Rubber wheels (Buy TT motor rubber wheels on Taobao and use them to remove the rubber skin)	2
bull's eye caster	1
Silicone Line	several
Aluminum alloy column	several
Aluminum alloy screws	several
perforated board	3

Summarize

 

After four days and three nights of hard work, the three members of the team reasonably allocated tasks and worked together to help each other, and finally completed this design project.

Through continuous testing and debugging, this system has completed the three basic requirements and functional parts of the design.

During this design process, we faced many emergencies and various difficulties.

For example, the selection of the driving circuit method and the matching of capacitance and voltage have been carefully considered for many times.

In order to improve the efficiency of the system, we changed the plan many times, but after careful analysis and self-adjustment by the team, we finally solved the problem and chose the optimal plan.

A relatively satisfactory result was achieved.

After this electronic design competition, we have further improved our circuit design and debugging skills.

At the same time, I also deeply realized the importance of collaboration and team spirit.

And the program considerations should be more comprehensive.

There are still deficiencies in the design, which will be paid attention to in future study work.

Finally, we would like to thank the organizers of the competition for giving us this opportunity to exercise.

We find our own shortcomings, but we will use our spare time to continue to conduct in-depth research to find better solutions!

 

Attached are test results

 

basic part

(1) The car can light up the LED indicator light during charging.

After five rolling charges, the capacitor voltage can reach about 15V.

Passed the test and met the question requirements.
    (2) Place the charged car at the designated starting point on the ground.

With one button start, the car can move forward after a delay of 1 second.

And the straight-line distance of the car from the starting point to the stopping point is 750cm. After testing, it meets the question requirements.
    (3) While the car is driving, the LCD screen can display the distance traveled by the car in real time.

After one week of driving, the distance displayed is 190.2cm, and there is a small error.
play part

    (4) During the circular tracking process, due to the too fast starting speed, the car easily rushes out of the circular track after tracking for a short distance.

However, after reducing the pwm, the starting speed of the car becomes slower. Due to the certain weight of the car body, it is difficult for the car to start.

After many tests and modifications to pwm, the car can achieve tracking.

However, due to the influence of the universal wheel, the car's tracking is somewhat unstable.

After modification, the car traced successfully and met the requirements of the question.
(5) The car starts after a delay of 1s, and six coins are placed on the track. Whenever a coin is detected, the LED light turns on.

After one week of driving, the coin count stops and the screen shows only five coins.

It was checked that there was an error in the interrupt part of the function. After modifying the code, it was checked again and again.

The screen displays six. After the coin count ends,

The car continues to trace for 4.2 circles until it comes to a complete stop, meeting the question requirements.