In my previous posts, I introduced models in the WRO elementary age group. In this post, I will analyze several models used in WRO 2017 Junior age group. Each model is unique and has its advantages and disadvantages, so keep objective, and let’s go!

The game description, rules and scoring could be found at WRO website: https://wro-association.org/competition/previous-challenges

Model 1

This model is very impressive. It has a compact structure. When it starts off from the base, it drives alone the wall of the competition field, which ensures that it runs through the Impacting Cubes Area completely straight without touching those blocks. This is crucial because white blocks have to be kept in the initial positions to get points. If the robot deviates the planned route a bit and touches the white blocks, it is highly possible that the white block will be moved out of the position.

When the robot model runs through the Impacting Cubes Area, those blocks except white ones will be collected and then move together with the robot. This is the most efficient way for the mission because the robot does not need to recollect those blocks later. This method has been utilized by almost all the robot models.

The front attachment is a clip-like structure. One medium motor is used to control the tightening and loosing of the clip, while the other medium motor is responsible for lifting and putting down of the clip.

A color sensor is tilt mounted over the clip to identify the colour of the tree blocks. The other color sensor is installed in front of the vehicle to identify the black line and guide the vehicle on the field.

The route planning of this model is widely used in the competition. It could be summarized as the following:

1. Scan the blocks in Impacting Cubes Area and collect the yellow, red and green ones.
2. Transfer the two solar panels to yellow area.
3. Transfer the tree blocks one by one to the area which is indicated by the scanning result of step 1.
4. Go to Finish Area.

Model 2

This model is much similar to the Model 1. The difference lies in the design of front attachment. In the Model 1, the clip is made up of beams, while in this model, the clip is made of axles. It looks not as strong as the beam. Therefore, the designer uses two pairs of axles to enhance the structure.

The route planning is totally the same as that of Model 1. As I mentioned before, it is the most popular route for WRO 2017 Junior age group.

Model 3

For this model, its front attachment is just like a fork lifter. When it lifts the solar panel or tree blocks, the fork keeps horizontal. Since the front attachment is only responsible for lifting/putting down action, a medium motor is enough to drive the front attachment.

In terms of route planning, this model follows the similar route to that of previous two models. The difference lies in two areas. One is that it carries solar panel to yellow area twice, each time for one panel, which influences its speed negatively. This weakness is caused by the short fork, because two solar panels could not sit on it at the same time. The fork structure uses a special shaped LEGO part, so upgrading needs to find a suitable part to replace the existing one.

The other difference in route planning is that the robot follows the black lines more rigidly. When it approaches solar panel or tree block, it turns 90 degree clockwise (or counter-clockwise) from main route, and then turn another 90 degree counter-clockwise (or clockwise) to face right in front of the block. This behavior is also related to the structure of front attachment. The lifting structure is short and has not clipping functionality, so it has to face straight toward the solar panel or tree block in order to lift them successfully.

In comparison, Model 1 and Model 2 could run tilt toward the solar panel or tree block to clip and lift them up, which will save a few seconds for those models in the competition.

This model has one colour sensor mounted above the front attachment, responsible for checking the color of tree blocks. Another two colour sensors are installed in front of the vehicle to guide it run on the field.

Model 4

This model is unique in its design. Its front attachment is like an arm of crane. One medium motor is responsible for tightening and loosing of a pair of clamps. The other big motor is responsible for the movement of the arm. Here it uses big motor because the “arm” structure looks big and needs big torque to be driven. The mechanical structure is designed in a way that when upper arm spins, the lower arm and clamps could keep horizontal. In this way, the front attachment could lift and put down blocks stably.

When moving solar panel and tree blocks, the robot model chooses to carry three blocks each time. To accommodate storing multiple blocks, the robot has to vacate its front part of the body. How does it realize? It puts two colour sensors on the far ends to identify black lines. The third colour sensor is mounted at a position a bit higher and the base of front attachment is installed a bit backward, so they will not obstruct the blocks taken in.

When the robot passes through the Impacting Cubes Area, those colour cubes are stored in a tunnel at the bottom of the vehicle. When the robot carries solar panel and tree blocks, the clamps of front attachment will hold the blocks and then slip them into the same tunnel. When it is going to dismount, the “arm” will fetch the blocks and put them into the destination area.

The purpose of carrying multiple blocks is to reduce time spent on transportation and increase efficiency. However, since the colour of tree blocks is random, the robot still needs to go back and forth among different destination zones to dismount blocks one by one. This feature actually offsets the time it saves through storing multiple blocks.

Although it might not be the most efficient solution for the mission, its design is definitely innovative. The model might have much better performance when used to accomplish more challenging tasks.

So which model is your favorite? Learn from those sample models and create your own unique one. Don’t forget to enjoy the design and have fun!

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