Exciting as ever, here at Project MARCH! The electrical team is really shifting from designing and prototyping to actual products. We’ve very much narrowed down what electrical components we will use and build based on the architecture we designed in 2016, and we are now building our own PCBs (Printed Circuit Boards) to fill in those blanks within the architecture.
Currently, we’ve completely assembled two types of our own PCBs which do exactly what we require them to do in our system, these products form the base of what we call an MVP, or Minimum Viable Product. These PCBs have two purposes. On the one hand they are used for initial testing of hardware and software, for example communicating sensor data from one device to another or testing safety features such as the emergency stop. On the other hand, they give us a fall-back option. By producing several versions of our products (we aim for 2 or 3 versions per PCB) we give ourselves space to learn from mistakes in previous versions and also have something to fall back on if a new version does not work as desired.
Now I can already hear you asking, what do these PCBs do? First of all, we have what we call the PDB or Power Distribution Board. The first version (see picture) has the ability to connect to the battery of the exoskeleton (green connector on the right) and distribute the power to both the motors (green connectors on the bottom) and the electronics (white connector on the top right), hence we call it the Power Distribution Board. It includes some safety features such as an emergency switch, which can be controlled by an external button that connects to the board (black connector on the left). It also has replaceable fuses (yellow and brown blocks) which protect the system from drawing excessive amounts of power. Finally, there is the component in the middle, which converts the voltage meant for the motors to a suitable voltage for the electronics. This enables us to use one battery instead of one for the motor and one for the electronics.
But wait, there’s more! The devices you see in the next picture is what we call the GES or General EtherCAT Slave. This is a multi-purpose node that can communicate with almost any kind of sensor and which can also control electronics such as a display. It can then wire to the main communication network, EtherCAT, which connects to all other electronics. Most importantly, it can use EtherCAT to communicate with the Master, the “brain” of the MARCH II exoskeleton.
So why am I not on holiday when we already completed the electronics that we need? In the following versions we want to make the PCBs much more useful by obtaining data of the system. This data is very useful for the following years of Project MARCH. For the PDB we want to include sensors which can register how much power each motor is drawing, for example. We also want to make the PCBs more compact and more suitable for the place they occupy. For the GES we want to integrate the red communication module (this is currently an off-the-shelf piece of electronics) in our PCB to have more flexibility in dimensions and placement of connectors. Electronics in the legs have no room on the sides, for example, because that is where the leg of the exoskeleton ends (they are quite narrow).