The batteries have arrived and they’re heavy! They weight about 24 kg each, witch gives almost 100 kg in total.
During this week the following tasks took place:
- Check the 20 year old battery charger: clean it and test it;
- Look for the best setup for the batteries and gather the necessary material to do it;
- Creation of a ROS node (client) to communicate via Ethernet to the Arduino Leonardo ETH in a private network: this step was implemented successfully and now messages can be sent from ROS to the Arduino;
- Integration of doxygen in the ROS envoirenment;
- Tutorial in ROS and C++ (1 day).
This week was dedicated for two main tasks:
- Choosing and ordering batteries for the platform
- ROS and C++ tutorials with professor Miguel Oliveira
For the first task a lot of research was needed to choose the batteries. There are numerous battery types on the market and choosing the right one for the right job is no easy task. For this particular application there were several aspects took into consideration such as size, weight, capacity, discharge rate and as in every project, price.
We are aware that lithium batteries have more energy density, witch means they have more energy per kg. But these batteries also are more expensive and have a more sophisticated way of charging.
On the other hand, since this project is about retrofitting, the existing equipment was analyzed. There were 4 batteries of Lead, each with 12V and 60Ah. To hold this batteries there are 2 cases that have an open space measuring [210x340x140]mm and a set of wheels underneath them witch makes operating the batteries easier.
After conducting the research, discuss budgets and analyze the up and downs of each solution, the ordered batteries were similar to the previous ones but with bigger capacity (watch in image below).
The main reasons for this solutions were:
- The increasing of the platform’s capacity in 25% (total energy of 3.6 kWh)
- The batteries are the same size, witch means the existing cases and the charger can be used
- The price is significantly lower than a lithium solution
- The weight of the 4 batteries is useful to balance the platform and lower it’s center of mass. This is important because it’s expected to place a robotic arm on top of the platform and it will to counterbalance it.
As previously referred, a ROS and C++ tutorial took place. The duration was one and half day and was important to get familiarized with ROS environment and C++ programming. This learning will continue during the next weeks since it’s needed to the rest of the project.
In the beginning of this week there was already a functional setup to test the platform, but the connections were all messed up because of the numerous wires needed. The used setup can be seen in the pictures below:
Despite this functional setup, a lot of time was wasted connecting each time a test was performed. Therefore it was needed to solve this problem. All the material was identified in order to start the rewiring and the problem fix.
Before the intervention, all the necessary material was gathered:
- Wires and cables
- Label sockets to identify each wire
- Nylon clamps and support to hold wires together
- 2 Fans to replace the older and noisy 4 existing fans
Everything was disassembled from the main box to start rewiring and soldering.
After testing different configurations and fixing every element, the final result can be observed in the picture below.
Note that the wire colors were changed in order to have a clear view of the voltages running each wire : Orange 48V; Blue 12V; Red 5V; White PWM signal and Black 0V.
This week was dedicated to learn about Robuter II platform and write an intermediate report so that future work could be pointed out more easily.
The remaining tasks were identified and analyzed individually to understand and distribute them.