Play LEGO MindStorms EV3 – Analyze Several WRO 2020 Elementary Group Models

As we know, due to the outbreak of Covid-19, WRO 2020 competition has been cancelled, but it will not influence our enthusiasm in participating in future events. In this post, I will pick up several models from YouTube channels and analyze their advantages and disadvantages. Those models are targeted for the WRO 2020, Regular Category, Elementary age group.

More information about the WRO competition could be found at its official website:

Model 1

This module comes from author: Pavel Tomshin

It has a very flexible front attachment. It could move upward or downward to clamp or loosen the LEGO blocks. It could also turn left or right to pick the LEGO blocks from the side. This feature is really effective. It saves the time for the model to turn, move forward and return. That explains partly why this model could accomplish the mission within such a short time – 33 seconds.

The model uses two medium motors to control its front attachment. One motor is used to control the up-down movement of the hook structure, and the other is used to control the left-right rotation of the hook.

There is a colour sensor mounted on one side, facing outward to scan the colours of LEGO blocks. It is a HiTechnic colour sensor. Compared to LEGO MindStorms colour sensor, the former could read more reliable values when the distance between colour sensor and the colour blocks is a bit far. If you once used LEGO MindStorms colour sensor, you would know that it could not identify colour precisely if it is put 2-3 studs farther from the colour blocks.

The following list compares the performance between LEGO MindStorms colour sensor and HiTechnic sensor, just for reference.


This model has to use HiTechnic colour sensor. Through the video, you could see that all the colour blocks are scanned just once by the HiTechnic sensor when the vehicle passes through those emergency suppliers at the beginning. If using LEGO MindStorms colour sensor, it is highly possible to identify wrong colours.

The designer does not let the model always follow the normal route to accomplish its mission. After getting those emergency supplies, the model will seek the blue colour which represents the position of river. It will go along the “river” for a while, pass through part of the red zone, and then walk along the edge of red zone till it finds the black line again to reach “Residential Area” (to deliver Mega Power Pack block) or “Hospital Area” (to deliver Medical Kit block). This route is irregular but shorter than when it normally follows the black lines.

The model uses three LEGO MindStorms colour sensors to guide itself in the match field. They are attached in the front of the vehicle, side by side, but they may not work all the time. Depending on the shape and colour of the route, there might be one or two of them working simultaneously to provide precise positioning.

Model 2

This module comes from author: Thầy Phong STEM

There are also three colour sensors side by side installed in front of the model. The 4th colour sensor is mounted facing toward the front attachment, so that it will detect the colour of the LEGO blocks when they are caught within the front attachment.

There is one medium motor to drive the front attachment, allowing it to turn upward or downward. When the front attachment is turning upward to the top position, the LEGO block is loosen. When it turns downward to the lowest position, the block is captured inside. When transferring those emergency suppliers, the front attachment is not responsible for lifting the block. Instead, it just drags it to destination.

The design of the front attachment is multi-functional. It could lock the emergency suppliers inside or lift the emergency cable block by using two folk-like parts stretching out from the front attachment.

Compared to the first model, this model generally follow the normal route of black lines. However, there is one point needing attention. When it fetches a Water Tank block, the vehicle passes through the place of school building. At the International Final, physical constructions might be installed on the school building. Therefore, it is better for the robot to change its route at this point to avoid these 3D objects.

Model 3

This module comes from author: TESSLAB Robotics

In this model, the arrangement of colour sensors are similar to that of model 2. There are three colour sensors attached in front of the vehicle. The 4th colour sensor is mounted facing toward the front attachment, so that it will detect the colour of the LEGO blocks when they are captured by the front attachment.

Its front attachment is different from the previous two models. One side of it is a beam which is just a fixed structure, while the other side is driven by a medium motor. When the arm-like attachment rotates, it clamps the LEGO block tightly. A white pointer part (which usually is used on the wheels to indicate rotation) is attached at the tip of the “arm” to prevent LEGO block from sliding out.

Like model 2, this model also follows the normal route in most of cases. In order to position itself precisely, it needs to run to the reference point (close to the base area) to better position itself. However, this consumes extra time. Therefore, the overall completion time is a bit longer than that of model 1 and model 2.


All the three models have their highlights. For model 1, it is innovative to design a front attachment which could fetch LEGO blocks from the side. it is also smart for the model to wiggle through the irregular route to seek the shortest path.

For module 2 and module 3, I like their way to mount colour sensor on one side, so that they could identify the colour of LEGO blocks after “catching” them, without having to use the high-resolution HiTechnic colour sensor. The front attachment of model 2 is able to lift or capture things. Its design could also be applied to other scenarios. The front attachment design of model 3 is concise but effective. I saw some designs which use two arm-like structures (driven by two medium motors, separately) to clamp the LEGO block, but this design could accomplish the same mission by using one “arm”, nice catch!

The purpose of analyzing those example models is not for copying, but getting inspiration from others’ excellent design and learn to build your owns. Hope those models expand your horizon and now you know how to start building your models. Enjoy the building and have fun!

Note: All the analysis articles are copyright products of Anyone re-posting them should credit author and original source. Anyone using them for commercial purposes or translating them into other languages should notify TheCodingFun and get confirmation first. All Rights Reserved.

One thought on “Play LEGO MindStorms EV3 – Analyze Several WRO 2020 Elementary Group Models

  1. Pingback: Play LEGO MindStorms EV3 – Analyze Several WRO 2018 models – The Coding Fun

Comments are closed.