Week 7

Successes

Mechanical

This week, we improved some parts of the launch system.

Last week we had broken our pull motor mount and shaft coupler; this was easily done as they were made out of wood or 3D printed PLA. This week we swapped over to metal solutions making our draw back system more rigid and thus more consistent.

We have finally found the correct hook geometry that allows us to unhook from the main carriage without too much push force while also snapping into place capturing the main carriage without too much pull back force. This has taken about 10 iterations to find this working geometry.

HookMovie.MOV

Metal Pull Motor Mount

Shaft Coupler

We have figured out and mostly implemented how we will attach our loader system. It is still not fully working, but we are awaiting a new motor driver that will allow us to drive our motor to its max capacity.

We have mounted the limit switch that will be used to notify our system if the two carriages are connected or not. This will automatically retract the motor pull back carriage once the main carriage is released, while it will also signify to the driver when both carriages are reconnected and ready to start the draw back session.

Electrical

Most of this week was spent cleaning up the electrical system to reduce wire clutter and prevent issues caused by wires coming undone. We added some cable management hooks to keep wires from interfering with each other, give the robot a cleaner look, and make debugging easier as wires can be easily traced between source and receiver. We also added a voltage regulator to drive the launch point adjustment servo separately from the Arduino power supply.

Before clean-up

After clean-up

Software

Minor work was performed in the software this week since the bulk of the software side has already been developed. Some time was spent tuning wheel speeds so that they drive at the same speed for equal input, which is necessary because the motors are driven via open-loop control.

Challenges

Mechanical

In making a metal version of the shaft coupler; we needed to replicate the 9 point star profile that the motor used to drive. This could only be done, through our capabilities, with a CNC. We were unable to locate an end-mill smaller than 1/8" even though internal radii of the profile were much smaller. It took a couple of iterations to find the right amount of relief that we needed to create for the end-mill to create the necessary contact surfaces while minimizing the amount of slop in the gear interface.

The loader system is persistent in its unwillingness to rotate the bean bags. this is both due to mechanical and electrical issues. There is too much friction between the bags and the base plate, thus the motor needs to be able to have high torque. We are trying to attack the problem from both ends, but have yet to realize the full solution yet.

Electrical

We have found that we were not running our loader motor at its max capability; thus we were unable to rotate the bean bags around. We have ordered a new motor driver and are anxiously awaiting its grand arrival.

Plan for Next Week

Mechanical

Next week, we will fully fix and implement the loader and create a phone mount so that we can control the robot while seeing via Facetime. We will then practice driving, shooting, and reloading on the competititon floor so we can get used to it and get used to teleoperation. While this occurs we will be tuning the robot and characterizing of our system. We will find out how repeatable our shooting is and will make anynecessary changes.

Electrical

Attach and rely on all switches (knowing when the bag is on the main carriage) and our main driving camera.

Software

Test Bluetooth module reliability in KEC.

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