My name is Max Suurland and this year I am the chief powertrain of the Eco-Runner Team 9. I am a second year Nanobiology student, but have been interested in electronics for a long time and therefore the function of chief powertrain fits perfectly. I am responsible for the functioning of the fuel cell, the motor and everything in between. As everything we do in the powertrain directly influences the efficiency of our vehicle it is crucial that everything within the powertrain performs optimally. As both the motor and the fuel cell work efficiently with different voltages, we need some regulators in between. One of these regulators is the FC Link and in this blog, I will try to explain how the FC Link works, how we designed it, and lastly how we produced it. 

FC Link 

The FC Link is the link between the fuel cell and the rest of the system, hence the name. What it basically does is modifying the energy from the fuel cell to the rest of the system. It mainly has two functions: safety and efficiency. The fuel cell in the powertrain will give an unstable voltage, and would provide the system with as much power as is asked by the rest of the system. This could mean that the fuel cell would break down itself if the rest of the system would ask too much power. Hence, the output of the fuel cell needs to be regulated, which is the first task of the FC Link. For the second function, the FC Link is connected via CAN bus to the other systems, such as: the Fuel Cell, the strategy computer and the ground station. With the information provided by the other systems, it can determine what has to be done. We use a technique that is similar to maximum power point tracking used in solar charge controllers. The difference is we try to optimize efficiency over a certain power instead of power over a certain voltage. This means that we try to achieve maximum efficiency by making sure that the FC Link always provides the rest of the system with enough power, while keeping the fuel cell operating at its most efficient point.  

Design

FC Link 3

To start with the design of the FC Link it was necessary to determine the topology of the entire powertrain, to find out what problems we might encounter. After the topology was determined, we looked at the system parameters, most importantly the powers and voltages. Furthermore we needed to define the use cases to find out possible dangers in the system. From this point on we roughly knew what we were looking for and we could start to work out the topology of the FC Link. To realize all the specific functions of your device, you need to find groups of components that are able to execute these functions. In the basics all these components are diodes, resistors and capacitors, but there are millions of different configurations with different varieties of these components. This makes realizing the electrical design a very time-consuming and difficult practice. When the basic electrical design was determined, we could start with the detailed electrical design of the FC Link. This is done in Altium; this highly professional software is sponsored by Altium, for which we are very grateful. In this detailed design you electrically connect all the groups of components on a circuit board. This involves searching for other and more parts, reading datasheets and doing simulations. These circuit boards are sponsored by Eurocircuits, a company which is specialized in producing prototype and small batch circuits boards. During the entire design process Technolution is our technological consult partner. Technolution is specialized in offering solutions in the area of electronics, logic and software, which fits perfectly in the field of designing our FC Link!

Logic

Besides the hardware design, we also need software to execute certain tasks within the FC Link. For this logic we use an ARM based system with all the bells and whistles we need baked into it, such as storage, CAN bus and voltage measurement. This makes it easy for us to design and debug. Also, the programming is easier if we are able to program it like an Arduino. This has advantages for its efficiency, it uses relatively low powers while having relatively a lot of computational power. 

I first started making diagrams of how the control systems should work, and started programming a general system that could be used for the FC Link, as well as for the fuel cell. This was done during the design, so I could make changes in the electrical design to also optimize the workings of the code. This includes making sure the controllers have to do less operations so that less energy is used, and lowering the latency of the system. And even in this phase, we are still coding and optimizing! 

Work in progress @Technolution

Production

For the production of the FC Link, all the different components have to be soldered onto the circuit board.  A great deal of the components we need are sponsored by W├╝rth Elektronik. As all these components are really small, something can go wrong quite fast. This means that the production phase involves a lot of testing. All the different connections need to be measured to make sure everything works as it should. Also in the production phase Technolution assists in finding and solving all the errors of the printed circuit boards, making sure that this crucial part of the powertrain works perfectly!