Revolutionizing our gear and optimizing driving strategy

If you watched our latest vlog about the new gearing system (you can watch the video here or at the bottom at the page) you probably noticed that we are currently working on improving our gearing system. The reason for this is that simulations done for “Driving Strategy Optimization” has shown us that a adding a new gear and manipulating the gear ratio will make our car even more efficient during the competition. We’ll dig a little bit deeper on this topic, so first off all, let’s start with the new and improved gearing, or at least the concept of the gearing.

The 2018 transmission  system had only one gear and was based on the concept of an internal spur gear. The gear was placed in the inside of the wheel, while the motor was mostly stagnant – it could be put in free however – and was connected to the gear. Thanks to an efficient motor this system was able to utilize the torque created by the motor for a fast and energy efficient acceleration for lower and higher velocities. However; now we’re going to modify the first gear and add another gear so that our first gear will work even better on driving and accelerate at lower velocities, while the second gear will work great on accelerations and driving at constant speed in higher velocities.

Here is a picture of how the 2018 transmission system was. The smallest gear was driven by the motor while the biggest was connected to the inside of the wheele

However, to become even more energy efficient than the previous years, one of our engineering students, Christian André Pettersen, came up with the idea to add another gear to the car. This gear will be used to cruise on higher speeds (more than 30 km/h) and for acceleration in high speed, if needed.

The new gear will be placed in the middle of the wheel, which will help us utilize even more of the force and energy created by the motor. Combined with the well-developed tooth profile, a perfect gear ratio and a optimized number of teeth at the second gear, we will be able to create an even greater torque from the motor and that will allow us to drive even more energy efficient at higher velocities.

Here a lego model of the new gearing system. The yellow one is the outer gear (first gear) the small grey one is the gear conectet to out motor and the black one in the midle is our second gear.

The need for another gear occurred when the mechanical group was researching and planning how to optimize our driving strategy, and a well-developed driving strategy combined with the perfect gear ratio will lead us to achieve an even more energy efficient result.

To simulate and optimize our driving strategy the group had to developed some “rules” to drive by. These rules were inspired from looking at and studying the track from 2018.

Here an illustration of the 2018 track, which we have based our driving strategy on

As you can see, the track has three major turns, which will largely influence the velocity of the car, which again will influence how much we’ll have to accelerate. The “rules” created from watching the 2018 track would be based on where we’ll accelerate, the intensity of the acceleration and the duration of the acceleration.

The acceleration profile, which is all the three mentioned points, would then largely affect our energy consumption and speed profile. The speed profile would also influence the energy consumption during the race, and also affect the total time the car uses to complete one lap (and the whole competition).

A short summary from how we’re using the driving strategy optimization to achieve even greater results: the two major factors we’re taking to consideration for the energy consumption is acceleration profile and speed profile. for what our total energy use will be, based on driving strategy. These two factors are again divided into smaller factors. Take these factores and combine them with some ideas from our student and you’ll get a second gear.

Here the student who came up with the idea for the new system. His name is Christian André Coldevin Pettersen and is a first year mechanical engenieer student

To minimize our energy consumption we have to optimize our driving strategy, which leads us to focus on the acceleration profile and speed profile. Our first gear will still be used to acceleration and driving when the car is at a lower speed. For the second gear, it will mainly be used for high speed driving, and with the right technology it will help us to minimize the energy consumption the speed profile creates.

The second gear will make it possible to approaching the maximal energy efficiency that our motor permits even more. The number of gear teeth and the radius of the second gear will make the torque created from the motor even greater. Since the torque is greater, the motor won’t need to use as much energy as it would with only one gear. With only this new and improved gearing system we’re expecting to save up to 6 percent energy from our past results.

What remains now it to produce the new gears, which will hopefully be done in the middle of march. Then we have to mount the gears to the car and test if it works as expected and as it’s supposed to do. Our mechanical group is even considering to make the gears interchangeable, however this idea it remains to see if this idea will be realized for the 2019 Eco Shell Marathon.

Watch the vlog where Christian demonstrates the lego modell here: