This week we got a scolding for our teachers because we have not worked a lot so far. We have to stand up and move on.
Now we have to concretize the choice of sensors and study about the regulation of the system.
On my side I will study about regulation. We already know we will use a closed loop because the output feedback on the system. Learn what is already existing. Chose several algotithm PID, SS, SIMO, MIMO, RST, LQR. Then determine the number of instruction to estimate the worst execution time of the loop, and the system’s response.
I know PID is the simple but not the more efficient, to be seen.
Determine what is the input of the regulation, an angle (not necessarly null), a speed. Think wich angle will we use. Absolute horizontal or about the road.
Hi, from now we have to post Wednesday and Sunday for more follow up.
We finally have all our component except the micro-controller. Motors are not final too. Because it is hub. It is compact but not necessarily enough powerful.
For the moment we have :
We are waiting for the teachers agreement to begin our PCB.
Hello every one!
So the challenge of this week was to finalize the choice about batteries and motors. And we did it. First we did again the motors calibration we need for our system. Last week we did simple calculations. Taking all parameters, we conclude that we need two 450w 48v motors. Plus, we choose a hub motor to the gain space. We had to be aware about the function of the engine. We made sure it is a two direction motor with the good controller. I contacted the seller and he confirmed this fact.
Here motor + controller : https://www.aliexpress.com/store/product/8-inch-450W-48V-brushless-non-gear-hub-motor-electric-scooter-electric-motor/1461770_32476560207.html
For batteries, again for gain space, we found batteries kit to build by ourself. One more avantage, its less expensive. LifePO4 48V 15Ah (http://evcomponents.com/diy-battery-kits/48v15ah-headway-lfp-battery-kit.html).
For the next week, finish the list of composents (accelerometer, board, led …). Begin the PCB of our system with Expedition PCB that I installed this weekend.
Have a great week!
Once week after the beginning. Here is where we are.
This week has been used to fix the system’s calibration. In the last post, I determined some values, but I based them on existing projects. I made calculs by myself for more accuracy from existing data such as acceleration (a = 2 m/s²), total weight (100 Kg), spoke of the wheel (r = 0.11 m), rotation per minute (63 ras/s) . To extract resulting data such as couple (C), motors power (P), 48V batteries intensity (I).
C = a * m * r = 22 Nm
P = C * w = 690 W
I = P/U = 15A
The coming week, will be used to identify exactly what components we would use. The main challenge would be about motors and batteries. For motors, hub or not? A hub is space gain but the power delivered by the engine is less than a classic motor. The space is also a problem for batteries. We have to find the most flat as possible. We have to choose betwen several kind of batteries (lithium, lithium-ion, lithium iron posphate, lead …) We need to determine the need. We must not oversize our system because the battery is the most expensive item of the project. If a simple lithium battery is enought, we won’t pick the last lithium iron posphate generation battery.
Ps : A picture to visualize our SKATEway (made by my mate Alban)