I worked on picking out the specific hardware components for this project. This included the robot chassis, wheels, motors + encoders, H-bridges, transformer/buck convertor, and power supply.
For the robot chassis, I looked into kits that could support 30 lbs of load, but unfortunately, none of them would come promptly. I had to compromise and picked a chassis that can hold 22 lbs, and I am planning on reinforcing the chassis and axles if needed. The robot kit I settled on includes 4 omni wheels and motors with encoders.
When deciding the motor used, I also looked into the motor’s torque and rpm and did calculations to ensure the max speed can reach 4 mph (calculated using the robot kit’s wheel diameters and motor’s rpm) and that the torque of the motor should be greater than ~3N of force (calculated using the max load of groceries). I found some motors that fit this specification, but since the robot kit includes motors and the new motors have other factors to consider – such as how to attach them to the robot (which motor brackets) and axles (differing axle sizes), and if the H-bridge can power them safely – I decided not to immediately order them. Instead, I am planning on testing the initial PID and motor movement using the motors given in the kit and upgrading to the new motors once I figure out the solutions to this problem.
As previously mentioned, I researched H-bridges to power the motors. I had to ensure they could safely handle a peak of 28A if the motors from the robot kit stalled.
My progress is on track this week. Since I can test the robot’s motor control and PID with the motors given in the kit and upgrade to better motors later, I am still on track.
Next week, I will be doing the design presentation. I will also be looking more into the motor issue and hopefully solving that by the end of the week.