Hope you don’t mind I made a copy of the calc over here:
I used your other page with the formulas written up and just translated them into TS/JS.
Please let me know if I got anything wrong (or if you want me to take your images out of there). Will link back to the site here from the calc there credit where credit is due and so others can join the conversation here.
Awesome! appears to be working again and thanks for the write up on how this is all worked out as well, we’re getting a lidar from you I believe for a side project at work and this will help for finding some rough parameters for the motors.
Excellent, and happy to help. If you follow the tutorial, you can see the limitations of the tool, but also how, if all of the values are needed beforehand, it becomes a bit of a “chicken before the egg” problem.
Thanks for the reply! Its working again the next day. Another question to add, may I know how the equations will differ if the robot were to pull (tow) some of the load? Or will it make no difference? Thanks in advance.
You would add the total weight of the trailer as added payload. You would not include the wheels for the trailer (idler wheels are not counted anyway). What it changes overall is that the robot itself would not need to physically support the weight on its wheels, though that is not factored into the equations.
@jakimovska Given that your calculations are EXCEL-based, free free to make it more accurate by including the moment of inertial of the wheels chosen, the weight of individual components (battery, frame, motors etc.), efficiencies of each component (motor controller, battery, motor, gearing), coefficients of friction etc.
Yes, I will definitely do that. For now I wanted to decide how many drive wheels the locomotion should have which some basic calculations. But from the results that I got I would definitely need four motors, as each motor needs a Torque of 0.301 Nm and Speed of 143.24 rev/m. I checked the motors in the comparison motor link that you shared, however, it was difficult to find one with such characteristics. The closest one I found was this one: https://www.robotshop.com/en/12v-165rpm-6805oz-in-precision-planetary-gearmotor.html#Specifications
A 20Kg robot is very heavy indeed (44 pounds, or the weight of a 4 year old child).
Remember, you need to select the motor based on its maximum continuous torque, as opposed to its stall torque.
In your case, 0.616Nm = 84oz-in, which is acceptable for that motor (if you use four).
Keep in mind that 10 degrees is not a significant angle, so you’re designing for a relatively flat surface.
Yes definitely, the surface is indeed flat, therefore, I was I was even considering lowering the angle to 5 degrees in order to lower the torque required to around 0.3 Nm. But it would be ideal if I design it at 10 degrees for safety. Unfortunately, most of the dc brushless motors I looked at in the RobotShop website that have 84 oz-in do not have the required rpm needed. Initially, I was considering having 2 drive motors and 1 or 2 wheel(s) as support. However, due to the weight and the characteristics needed of the motor I decided to use 4 motors driving each wheel.
Could you please recommend me other acceptable motors that would be suitable, as I struggled in finding motors when searching?
Thank you for all your input so far, it is really helpful!
The MTO9055 motor has KV of 60. Does that means that if I use 24 V, “ideally” I would get 1440 RPM? Also how can I check that this motor meets the torque requirements?
Correct - that’s the theory. Good question about the torque - don’t see any specs, but it can provide up to 800W (don’t push it up to that for long though) and they are intended to move an adult male on a skateboard… If you need specs, I can transfer the post to a tech who can reach out to the manufacturer.