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Introduction

The World Robot Olympiad is arguably one of 2 premier international LEGO Robotics competitions (the other being the FIRST Lego League). In this competition, teams are split by age groups, designing robots to complete various challenges around a common theme. This year, the Senior students were tasked to design robots cable of picking up objects representing Nodes and Fiber Optic cable and placing them in a grid.

Node Mission

The nodes (old and new) were differentiated by color, with only the black ones picked up.

When depositing the nodes, teams had to ensure that the nodes were facing a specific orientation determined by a set of randomized color coded blocks placed near the start of the mission

Fiber Optic Mission

The Fiber Optic cables are joined by a long, flexible tube which sagged under the weight of the blocks at each end. This posed the challenge of how robots should manipulate soft objects precisely as teams had to deposit them in the grid with little tolerance to spare.

If that was too much to digest, it would probably help watching a video of how some teams accomplished the tasks.

While these 2 robots look very similar (as a lot of robots do now that Youtube has made sharing so easy), they adopt 2 different mechanisms when dealing with the lifting and rotation of the nodes. Approach 1 rotates the node passively as it is being picked up by offsetting the robot with respect to the node, causing a torque about the center of gravity of the object. Approach 2 rotates the node actively with a Medium Motor attached to the lifting mechanism.

Our Idea

While these 2 approaches are not inherently wrong, both have some shortcomings.

Approach 1 requires the robot to be very precise when approaching the object. Of course, most of the risks that come with this approach can be mitigated by good programming and sensor placement but you can’t have too much robustness to a solution!

Approach 2, utilizing a second motor, results in the robot not being able to collect multiple nodes at the same time since the EV3 has a limited number of ports. Furthermore, adding a motor to the end of the lifting mechanism shifts the Center of Gravity forward which is detrimental to consistent movement.

Hence, we came up with a mechanism that uses a single motor to control both the lifting and the rotating of the node, allowing it to collect all 4 nodes while maintaining control over its orientation.

Iteration 1

The aim of the first iteration was to prove that this was actually doable. While it may seem complex, the underlying principle comprises 2 simple parts.

1. The Lifting action is done by a 4 Bar Lift
2. The Rotating action is done by a Stepping Mechanism

To link them up, the 4 Bar Lift had to be capable of triggering the stepping mechanism, which was done with the D-shaped piece. To improve the reliability of the mechanism, rubber bands were used as a restoring force instead of gravity. This allows a single motor to perform a lifting action through most of its Range of Motion. It is only when the lifting action is complete that the Stepping Mechanism triggers, rotating the object by 90 degrees. Repeated lifting to the top-most position will allow users to rotate the Nodes indefinitely in 90 degree increments.

While the goal was achieved, it would be next to impossible to fit 4 of these huge mechanisms into the size constraints imposed by the WRO Rules. Hence, more work had to be done to simplify and reduce the footprint of the mechanism.

Iteration 2

In the second iteration, we used as few parts as we could to accomplish the same task, using exactly the same concepts.

As can be seen, the huge triggering mechanism from Iteration 1 was discarded. Instead, the Stepping Mechanism was directly connected to the 4 Bar Lift, working based on the relative motion between the linkages of the lift!

Overall, this resulted in a much smaller form factor, allowing 4 of these mechanism to fit easily within the space constraints of a WRO Robot. The level of bracing done on top of this is entirely up to the actual implementation and comfort levels of the user.

Note

If you’ve been following our Facebook Page, you’ll know how much we hate teams that simply copy solutions from Youtube. The amazing thing about joining a competition is exploring the possibilities in a way that traditional classroom approaches cannot. Anyone can, through repetition, build the same chassis and mechanism (which is something we have noticed in students we have taken in from other trainers), but the best Roboticists should be able to come up with approaches based on their own interpretation of problems.

For those who have seen our teams at NRC (Singapore’s qualifier for WRO), each team sports a different design, noticeably different from what you may be able to find online. Sure, their implementations may not be great after just a couple months of training, but we believe that our job as educators is to guide our students in their process of developing solutions and fundamentally switch their mindsets from application to creation.

Our students never see our solutions or creations before competitions. If they do happen to see it, they are immediately barred from using the solution. This is also why we make it a point only to share on our social media platforms after competitions. Through sharing, we hope to show everyone what’s possible, so that the next time they start a project, the spotlight on a single solution turns into a floodlight on the solution space.

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