Suspension Update and Range Modeling Intro

Last week Roberto outlined EVT's new project and how each week a different a different team member will overview the weeks progress and their personal contributions. I'm Rango and this week I'll talk about range modeling but first, the progress of the entire group this week!

Bike trailer with suspension clamp

The trailer that is going to haul our batteries is an unsprung mass so if we run into a bump or a pothole, we are sending a large jolt through the batteries as well as the rider. To prevent this, we are designing a suspension system to dampen these sudden impulses. All of the detailes of this will be better explained by someone on the mechanical engineering team, but for now I just want to share saturday's work in the shop.



The picture shows our fancy trailer and our shock mounting system. Because we don't want to drill into our trailer, the mechanical engineering team designed a neat clamping device using two 90 degree aluminum extrudes. The point is we have a working prototype of part of our suspension made from scrap material and we will soon buy material to machine the final suspension! (Again, the details of the suspension will be described in the near future)

But now, back to range modeling:

New York is a long way away from boston. A very long way. We have 230 miles of road ahead of us so it is important to know our expected battery usage, and not just in a back of the envelope sense. I'm developing a model to determine the state of charge of our system over the course of our journey. Of course, it isn't possible to simulate the exact conditions on the bike or the rider's driving style but we these simulations will lead to insight about average behavior of the bike as wel as optimal driving strategy.

So then the obvious question comes up: how does one actually model this bike system?

The model really breaks down into three coupled systems that can be coded and verified independently.

First, we have the physical forces acting on the bike. The torque applied by our motor through the wheels, aerodynamic drag, rolling resistance, change in elevation, and acceleration are part of this sub-model.

Then, there is the electrical model including our batteries, motor controller and hub motor. This accounts for the inefficiencies involved in electric motors and their control systems.

Finally, we have changes in physical conditions as we travel our route. Changes in elevation over the course of our route as well as traffic conditions fit in here.

Over the next few days I'll detail the model for each of these subsystems