Concept Generation & Selection

Subsystem 1: Hopper

The first part of the machine is the Hopper system. This is where the LEGO pieces will be dumped to begin the sorting process. They will then be slowly let out of the hopper and filtered until they make their way on to a conveyor belt headed for the Recognizer. The group considered three different designs for the Hopper system, with the stipulation that it provide a receptacle to insert the LEGO pieces that need to be sorted and control the flow of the pieces into the rest of the device.

The first design that was considered for the Hopper system is Hopper A, the Funnel Door, shown above to the right. LEGO pieces would be dumped into the hopper, and a trap door at the bottom would open on regular intervals to release a small number of pieces onto the ramp below. This trap door effect would be achieved by stationing an actuator at the bottom of the hopper and having it set to swing open on timed intervals. Once released by the trap door, gravity would pull the pieces down the ramp onto a V-shaped separator mechanism. This mechanism functions by having motors attached which constantly shake the separator, forcing the LEGO pieces to both space out and orient themselves ahead of the Recognizer. As each piece funnels through the separator, it is deposited onto a conveyor belt which takes it to the Recognizer.

The second concept that was considered for the system is Hopper B, the Gumball Dropper, shown above in the center. LEGO pieces would be deposited into the hopper at the top and fall onto a rotating disc at the bottom. Holes cut into the disk would regulate the rate at which the LEGO pieces would fall through onto the conveyor belt below. The conveyor would then take the pieces to the Recognizer.

The final concept that was considered for the Hopper system is Hopper C, the Inclined Conveyor, shown above to the right. In contrast to the previous concepts, the hopper was located at the base of the design. Once the LEGO pieces were at the bottom of the hopper, they would be carried up an inclined conveyor belt before being deposited into the V-shaped separator. To ensure that the pieces were caught, the inclined conveyor belt would have ridges at regular intervals to carry the pieces up the steep slope. The V-shaped separator functions in the same way described in Hopper A and delivers the LEGO pieces onto a conveyor belt to be taken to the Recognizer.

After comparing the three concepts, the group opted to utilize Hopper C in the system design. Hopper B was unlikely to work, as the length of rod and beam pieces included in the EV3 kits would force the hopper to be mounted high above the conveyor belt, leaving the opportunity for smaller components to bounce off the conveyor. Furthermore, while the rotating disc would regulate the inflow of pieces to the Recognizer, the group felt that it was not the optimal method of doing so. When comparing the Funnel Door concept to the Inclined Conveyor concept, the group decided that the conveyor method would be easier to regulate the flow of LEGO pieces into the device. Adjusting the speed of the conveyor belt would give the user more control over the rate at which LEGOs enter the main body of the machine, as opposed to gravity determining how many pieces come through the trap door. Given that the rest of the concept was the same for both cases, the group decided that Hopper C would be the most efficient choice for the device.

Subsystem 2: Recognition

The second system in the group’s device is the Recognizer. For this system, the group only generated one concept, as most of the research thus far has been on how to use machine learning for the machine. The group did not wish to be tied down by a specific design until they had figured out how they were going to implement image processing, so the group created an open bay concept that would only be subject to change if the camera needed to be repositioned for optimal imaging. The Recognizer consists of a camera and lighting mounted above the conveyor belt as it carries LEGO pieces towards the Sorter. The Recognizer would identify each piece as it went past, and deliver the necessary information to the Sorter in order to have each piece placed into the correct category.

Subsystem 3: Sorter

The final system in the machine is the Sorter, for which the group developed two different concepts. The purpose of the Sorter is to interpret the information received from the Recognizer and place each piece into the correct bin by its category. Other competing ideas were to either have actuators knock the pieces into bins, or to use a gravitational-based sorting method.

The first concept for the Sorter was Sorter A, the Sorting Conveyor, shown above to the left. Based on the information received from the Recognizer, an actuator will activate, swinging out to divert the LEGO piece into the bin of its category. There are six bins along the side of the conveyor for the categories that the group is planning to sort the pieces into. At the end of the belt is a seventh bin to collect any pieces that fail to be identified or properly sorted. This allows the user to easily place such pieces back into the hopper at the beginning of the machine.

The other concept that was developed is the Gravitational Sorter, shown above to the right. For this system the conveyor belt would terminate at an inclined board. Actuators would rotate to guide pieces into the correct bin as they came off the conveyor.

Ultimately, the group decided that Sorter A would be the best system for the device. The group already required a conveyor belt to move pieces between the different systems, and thought that it would be easier to have actuators filter LEGO pieces off of the conveyor than build a gravity-based board to sort them. Furthermore, the Gravitational Sorter carried a larger risk of the pieces bouncing off of the actuators and landing in the wrong bins or outside the machine entirely.