Transfer the Load with Winch Challenge

Initial Design

Functions: The robot is required to pick up a weight starting on the floor, and lift the weight to the level of a standing platform. The robot must then rotate and lower the weight onto the platform, then rotate back to the front and lower to pick up another weight. This most all be completed in under one minute.

Systems: The initial design of our robot is stationary and uses two motors. One motor will raise and lower the string that lifts the weight and the other motor will rotate the robot to place the weight on the platform. The design also incorporates a Lego NXT brick to power the motors and the body of the robot is mainly constructed of Lego pieces.

Integration: The robot we built uses the Lego NXT brick as the base to avoid having to counterbalance the weight of the brick. We used long Lego pieces to hold the motors above the brick and to build a bar behind the lifting motor. The bar hold two smaller weights which serve as a counterbalance to the lifted weight. The addition of three gears to the front of the lifting motor assist the motor in turning the string to lift the weight.

Optimization: Our robot uses three gears on the lifting motor. The gears provide a ratio which allows the motor to lift more weight because of the change from a smaller amount of teeth to the larger amount on the gear set with the string wrapped around.

This is what my crane will look like. 

This is how my turntable will be attached.
Another motor will be attached to the lego base,
and the motor will be able to control the turntable.
The turntable as well as the motor are the supports in which
the entire crane will sit upon. 

This is my Gear ratio calculations, as well as a close up of how
the gears will look. Initially I had a larger winch,
but when I began to try using it, the string did not
unwind like I had hoped. I calculated a new gear ratio with
a smaller winch. This also helped give me more variety as well
as freedom with the ratio since one end of the range
ended up being 0.5. I plan to use gears with 10 and 20 teeth.

Daily Log 10/04/2016

Today we got to work on fully developing our concept sketches for our robot to rotate and lower to pick up a weight. We have a rough idea of the outcome that the robot will look like and we began work on construction of the robot. The robot has two motors with one rotating the winch to wind the string and the other to rotate the complete robot body in order to place the weight on the platform. So far, we have attached the winch and gears to one of the motors and are currently working on attaching the brick to the robot as a whole. It was very exciting when we were able to correctly complete the gear ratio and when we tested the fixed gear setup, we were able to move the winch through two gears. We were also happy that we were able to connect the two motors to each other without the contraption falling apart.

Daily Log 10/06/2016

Today we continued construction of our robot and ran into some design flaws with our original layout. One of the largest struggles we had today was that when the robot attempted to lift the weight it would tip and break. This showed us that the structure of the robot was not balanced, but we had a lot of difficulty trying to fix it. Towards the end of our work time, we found that we had designed the robot with the winch and gears off to the side. This caused all the weight to be on one side of the structure and was making the overall product unbalanced. This will be a goal of the next work time to center the weight and provide a balance towards the back of the robot. Evenly though the robot was not yet able to lift the weight, we did create a solid base for the bot to connect to the surface it will be resting on. Previously, we had the motor of the robot resting on the ground, but it was not tall enough to lift the weight onto the higher ground. These were two of the issues that were fixed with the construction of a new, sturdier base that lifted the entire robot, including the motors, higher off the ground. We also started working on the programming of our bot today because we had to do some moves in order to test the strength of the robot.

Daily Log 10/10/16

Today was more about the logistics of the robot. We decided to change the way that the robot stood so that the stability was increased. After we did that, we continued to test and retest the robot's coding. Rather than counting out rotations, the movement up and down was done in seconds. This made it easier to track the robot's speed as well. When turning to put the load on the landing piece, we used degrees. Since the gear that turned was attached to an ouput gear that did the turning, we used the gear ratio to help get a ballpark range of how many degrees the driver gear would need to turn to make the output gear turn at least ninety degrees. In the end, we were able to perfect all of the robot's coding, but we were unable to make it run properly. Our problem was that when the load released onto the block, the counterbalance used to align everything would make the robot lean. This disconnected the driver gear from the turntable's gears so that the robot would be unable to return to the original position and go back down to get another load.

Daily Log 10/13/2016

Today was our final day to work on our robots. We only had a couple small problems left going into class, but the large issue was the turntable. The weight that is being lifted holds two gears against each other that allow the gears to rotate. After the robot places the weight on the platform, it fails to return back to the original direction to lower the string and pick up another weight. We had multiple trials in which the robot would turn back without trouble, but there was no consistency in the success of the rotations. The robot's instability played an important role because it was inconsistent. Throughout the making of the project this was a very important factor that we spent a lot of time working on. As we continued to test, I found that taking away some of the supports helped the robot move more freely, which is how we ended up being able to fix it.

Final Design

We struggled a lot in our last couple days because we were not making much progress with the performance of the robot. In the end, we were able to get the robot to consistently lift the weight and drop it onto the platform and the rate was of mediocre speed. We were really proud of how the final product turned out because we had spent so much time on the project.

The final design of our robot one the last day of project development

Something that we really improved upon during this project was understanding the different necessary roles in a group project. Towards the end, we had one person working on the construction and repair of the robot, while the other partner edited code and worked on documentation of the project. Both people in the group helped the other with comments and feedback, but we were each able to focus on a specific portion of the project without concern of not getting other things done. We also learned a lot about gear ratios and how they can help the speed of a robot, while also lowering the strength. This became relevant in our beginning designs where we struggled with the robot tipping because of the weight. We had to change the gears in order to lift the weight without damaging the robot during a run through.