# Sixth Lichuang Electric Competition# Logistics Weighing Assistant

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* 1. Introduction to project functions

1.1 Overview of Logistics Market

In 2019, my country’s total social logistics volume was 298 trillion yuan;

In 2020, the total social logistics volume in the country was 300.1 trillion yuan;

In the logistics market, through the combination of science and technology such as intelligent hardware, the Internet of Things, and big data, the analysis and decision-making and intelligent execution capabilities of the logistics system have been better improved. The transformation of the logistics model into smart logistics is the current trend.

New technologies in the express delivery (package) industry such as unmanned vehicle delivery, drone delivery, and intelligent sorting systems in logistics centers already exist and are widely used, effectively reducing labor costs and improving efficiency. However, in the traditional logistics industry, the above new technologies cannot be used due to the volume and weight of the goods.

1.2 Logistics market classification

Logistics can be divided into the following 4 categories according to weight:

1. Parcels (0-30 kg/piece), the cargo owners are mainly individuals, enterprises, and merchants, and the main operations are express delivery companies;

2. For small ticket LTL (30-500 kg/piece), the cargo owners are mainly individuals, small workshops, and merchants, and the main operations are logistics companies, dedicated lines, and express companies;

3. For large-ticket LTL (500-3000 kg/piece), the cargo owners are mainly manufacturing companies, third-party logistics, first- and second-level wholesalers, and the main operations are logistics companies, dedicated lines, and express companies;

4. For complete vehicles (over 3,000 kg/piece), the cargo owners are mainly manufacturing companies and third-party logistics companies, and the main operations are logistics companies.

1.3 Road freight market size

The size of the road freight market is as follows:

1.4 Current problems in logistics loading and unloading

In the three cases of small ticket LTL, large ticket LTL and complete vehicle, it is necessary to weigh and use a forklift for loading. There is a special large scale in the logistics park for weighing the whole vehicle. The weighing is generally 2 yuan per ton. The whole vehicle Weighing costs tens of yuan per time. This type of weighbridge occupies a large area and is expensive. It is very inconvenient to weigh the entire vehicle. After it is overloaded, it needs to be driven back to unload. It is especially time-consuming and laborious to turn around for large trucks. If it is not full, it will also affect the transportation capacity. Increased costs due to dissatisfaction;

Large scale weighing charges are expensive, the weight of goods is not displayed in real time during loading, and overloaded unloading is troublesome. Merchants operating on dedicated lines use small 1-3 ton scales for weighing in batches. They manually record the single weight and then calculate the total in writing. The weight of the entire vehicle is obtained. This weighing method solves the problem of overloading, but it has the following shortcomings:

1. It is easy to make mistakes when calculating by hand: Manual calculation of weight is easy to make mistakes;

2. Space occupied: The small weighbridge occupies an area of ​​about 2 square meters, occupying the space for stacking goods. If the annual rent of 30 square meters is 150,000, then the annual rent of these 2 square meters will be 10,000;

3. Unable to weigh: Special-shaped goods such as long iron rods cannot be weighed, or the scale needs to be moved to an open area before weighing;

4. Waste of time: When there are many goods, weighing one goods requires moving other goods away, which is inconvenient to use;

5. Cumbersome use: After the forklift puts the goods on the weighing scale during weighing, in order to prevent the forklift from affecting the weighing result, the forklift needs to be driven out, after recording the weight, drive in again to lift the goods;

1.5 Functional features of the work

Inspired by the above logistics scenarios, this weighing assistant solves the pain points of overloading, underloading, and troublesome pricing when loading and unloading forklifts. It has single weighing, cumulative weight, no volume, single weighing range of 40kg-5000kg, and printing Features such as receipts, automatic sleep, and time and temperature display can be widely used in forklift loading scenarios, such as factories, logistics parks, ports, etc.;

Note: There is no limit to the theme. It can be a solution to a certain problem in life/work, a plan designed for a certain group of people/scenarios, graduation project/course design/DIY project/purely cool project, etc. Mainly talk about what problems you solved by what means.

*2. Project attributes

Note: Please indicate whether the project has been made public for the first time; whether the project is original; whether the project has won awards in other competitions; if so, describe the details of the award; whether the project has participated in a defense in school.

* 3. Open source agreement

3.1 The open source agreement uses GPL3.0 recommended by Lichuang

Note: Altruism means self-interest, please read the following content carefully.

1. Embrace open source and give projects unlimited value. It is recommended that more than 80% of the core functions of the project be open source;
2. If a certain part of the function is irreplaceable and the project cannot solve the corresponding problem after deletion, then the function implemented by this part is the core function of the project; for example, if an electronic load is designed and a host computer software is designed to monitor power changes, the electronic The load is the core function, and the host computer software is the auxiliary function; for example, an isolated 485 module is used in the electronic load to communicate with the host computer, then the communication function implemented by this 485 module is an auxiliary function;
3. Projects should choose an open source agreement that suits them . If the project references other open source projects, the source should be indicated and follow the original author's open source agreement. It is recommended that original projects use the GPL3.0 open source agreement;
4. Functions implemented by directly quoting the original circuits or original codes of open source projects cannot be used as the core functions of one's own projects, and functions directly implemented using common modules on the market cannot be used as core functions of one's own projects.

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*4. Hardware part

4.1. Equipment installation

The installation steps are mainly divided into the following 4 steps:

(1) Fix the host machine on the forklift;

(2) Install sensors;

(3) Install the trigger switch;

(4) Install the power cord;

See the video in the attachment for specific installation.

4.2. Equipment working principle and mechanism

4.2.1 Principle:

The key component of this equipment is the spoke pressure sensor. The pressure sensor is installed on the forklift screw. The main force on the sensor is the pressure caused by the chain pulling the gasket, as shown in the following figure:

The tension on the gasket is the vector sum of the weight of the chain, the weight of the fork, the weight of the cargo, and the friction of the transmission structure;

Since the hydraulic structure will continue to release part of the force when the forklift is stationary, we need to use dynamic weighing, which is Newton's second law.

The weight of the cargo is recorded as

Z can be obtained through analog-to-digital conversion, and Y is the value of the sensor when the forklift is not loading goods, so it is easy to obtain the weight X of the goods.

4.2.2 System block diagram

4.3. Working mechanism

One-time operation weighing process:

When the forklift presses the lifting lever, the trigger switch is pressed, and the device begins to obtain the value of the sensor, which is calculated as weight and displayed on the screen in real time. When the goods are lifted to a certain height at a constant speed, the microcontroller obtains enough data, locks the weight, displays the final calculation result on the screen, and presses the print button to print out the weight.

4.4. Notes:

The equipment needs to be calibrated when used for the first time, see debugging methods;

Equipment needs to be calibrated for use, see debugging methods;

Forklifts are professional construction machinery, so please pay attention to safety when operating them;

4.5. Debugging methods

4.5.1 Calibration (find the weight corresponding to the Z value)

First, perform an empty forklift lift to obtain the value corresponding to Z at constant speed, assuming it is A;

Then put a heavy object, such as 1 ton of goods, and lift it at a constant speed. Record the corresponding value as B;

The value of BA is the corresponding value when the sensor is subjected to 1 ton of pressure;

Because the sensor is linear, the calibration is completed in this way. The corresponding value of 2 tons is 2*(BA), and the corresponding value of 3 tons is 3*(BA);

Any cargo weight X=Z/(BA);

4.5.2 Calibration (finding Y)

When using a forklift, the fork (different weight), lubrication friction factor, different cooling and heating engine power, temperature of the detection circuit and other factors cause the Y value not to remain constant, resulting in zero point drift, so calibration is required. Press and hold the calibration button on the device while the device is in cargo condition, and the screen will prompt it to lift at a constant speed. At this time, the calibration can be completed by lifting.

4.6 Button description

Settings: Enter the setting interface, password 0202;

Set to zero: reset the current weight and accumulated weight to zero;

Accumulation: The current weighing result is included in the total weight;

Print: print receipt;

Note: It is recommended to use Lichuang EDA . If you choose other EDA tools, please upload schematics in PDF format, PCB drawings in PDF format, and PCB files in Gerber format in the attachments. Here you can explain in detail your project implementation principles and mechanisms, precautions, debugging methods, testing methods, etc. It is recommended to introduce your ideas to others in the form of pictures and texts.

*5. Software part

The principle of weighing was introduced earlier, and industrial equipment needs to go through a lot of testing, modification and improvement to achieve stability and reliability; the research and development of this equipment has gone through thousands of times of different lifting speeds for more than 10 forklifts of different brands and models, with different levels of old and new. The weighing test finally achieved satisfactory results after several months of adjustments and modifications.

5.1.Weighing curve

5.1.1 Weight from filtration to weighing stage

The curve of 5 weighings of a certain cargo is printed as shown below.

As can be seen from the above figure, the weight of the cargo is calculated in the part of the figure that fluctuates less, and the approximate range is [80,250].

Since the slope of the curve in the interval [0,45] is large, this part of the value can be filtered through slope judgment during the weighing process. The judgment method is to add the three adjacent values. The last three values ​​are greater than the previous ones. 3 times will be filtered;

5.1.2 Distinguish the differences between different weighing methods

The figure below is the weighing curve of a forklift with 1,600 kg of cargo at different speeds after filtering the weighing weight:

In the above picture, you can see that the three graphics on the left are sparse (Curve 1, Curve 3, Curve 5), and the right is very dense (Curve 2, Curve 4, Curve 6). If the same algorithm is used, the calculation result deviation will be greater than 10 thousandths, so it needs to be distinguished. Different algorithms are used in these two cases;

The yellow part in the picture below is the result of 6 weighings in the picture above after algorithm calculation:

In the picture above, the 6 weighing results are 1607, 1604, 1609, 1608, 1608, 1606, and the error is 2.5 to 5.6 thousandths. avg represents the degree of fluctuation density after screening. Different algorithms are used for different density;

5.2.Weighing algorithm

Delete the first 40 unstable values, because this is the acceleration stage. Calculate the average of the next 100 values, then add every 3 adjacent values ​​and average them. Calculate the number of peaks that cross the average value and record it. The difference between the first highest value and the second highest value, if the difference is within 10% of the average value, and the first lowest value and the second lowest value are within 10% of the average value, you can use this curve , otherwise continue weighing. If the number of acquisitions exceeds 200, this weighing will fail.

As can be seen from the curve on the left, the dense area of ​​curve 3 and curve 5 is below 1600, and the number of peaks is 3. Curve 1 is more evenly distributed, and the number of peaks is 5, so it is distinguished according to the peaks, and the number of peaks is less than or equal to 3 Curves 3 and 5 use the sparse calculation method , and curve 1 uses the dense calculation method when the number of peaks is greater than 3.

5.2.1 Calculation method when sparse

Remove 10% of the maximum value and 10% of the minimum value, and average the remaining values ​​to calculate the weight. Since the dense area below 1600 and the points above 1600 have a larger amplitude, the average rear weight is closer to 1600.

5.2.2 Intensive time calculation method

The waveform when dense oscillates back and forth at 1600, so the wave peak must be greater than 3. If you remove more maximum values ​​and minimum values, the result will be more accurate. I chose to remove 20% of the maximum values ​​and 20% of the minimum values, and the remaining 60% Data are averaged.

5.3 Compilation environment

keil

5.4 Project configuration

cubemx

5.5 Burning method

Burn using swd method

Note: If your project involves software development, please upload the corresponding project source code in the attachment. Here you can describe in detail your software flow chart, functional module block diagram, explanation or popular science of related algorithms, source code structure, construction and configuration of compilation environment, source code compilation method, program burning method, etc. It is recommended to introduce your ideas to others in the form of pictures and texts.

*6. BOM list

Note: BOM list involved in the project. Please upload a screenshot of the BOM at this location. Please upload the list details in PDF format to the attachment. Suggestions include model, brand, name, packaging, procurement channels, usage, etc. The specific content and form should be based on clearly expressing the project composition.

*7. Contest LOGO verification

7.1 pcb photo

Photos of the front and back blank boards of the analog-to-digital conversion board:

Motherboard front photo:

Photo of the reverse side of the motherboard:

7.2 Photos after welding

Photos of the analog-to-digital conversion board after welding:

Front photo of the motherboard after soldering:

Photo of the reverse side of the motherboard after soldering:

Please upload a project picture containing the competition logo. The logo will be printed on the PCB in the form of silk screen printing.

Click the zip to download the competition logo! (Contest logo).zip

* 8. Demonstrate your project and record it as a video for uploading

Video requirements: Please shoot horizontally, with a resolution of no less than 1280×720, in Mp4/Mov format, and the size of a single video is limited to 100M;

Video title: Lichuang Electric Competition: {Project Name}-{Video Module Name}; such as Lichuang Electric Competition: "Autonomous Driving" - Team Introduction.

More details: https://diy.szlcsc.com/posts/06c94d90c2c447dfbd9ed7339ff4a5b1