Over the last two weeks, I’ve been working on getting the whole system working together. For mid-review, we were able to get the linear actuators moving such that when we tilted the platform, the IMU was able to detect that once the board was no longer at 0 degrees from the ground, the linear actuators would activate to even out the board. That IMU that we were using ended up breaking, and we knew this because it would get very hot to the touch when just supplying the correct input voltage. We purchased a new IMU, the BNO085, but when trying to read the data with I2C, I realized that it uses Sensor Hub Transport Protocol (SHTP), which is different from the standard I2C. So, when I was trying to access the different registers to get the sensor data, it would not return the correct information. This resulted in having to buy another IMU, the MPU 6050. I decided against buying the original IMU that I was working with because the gyroscope data was oddly inaccurate, and I had previously worked with the MPU 6050. Once the MPU 6050 arrived, through the PYNQ framework, I was able to receive the IMU sensor data and apply a simple complementary filter to get pretty accurate orientation readings.
In order to get the motors running with the PWM signal from the FPGA, I needed to use a logic level shifter since the PWM signal from the FPGA is 1.8V. I was able to successfully get all four wheels running, but just by moving the wires around, it would change behavior of the motors. They would either stop running, or they wouldn’t stop running when they were supposed to. After doing some research, I realize that this is probably because of capacitance coupling that is amplified by the level shifter. Our wires being longer does not help with this behavior, so I got a new level shifter that is supposed to be more resistant. In the meantime, we will be continuing with Arduino, such that we can test our control algorithm.
Throughout the last two weeks, we also decided to just try and get the system running with an Arduino since we were running into some blockers with the FPGA, so while simultaneously trying things with the FPGA, I was working on getting the system working with the Arduino. This was pretty simple since there is a lot of technical support for Arduino.
We are behind schedule, but we are moving along and not letting the blockers get in the way. We are working on tasks with the Arduino that can be replicated on the FPGA, so that we do not fall too far behind while working with the FPGA.
By Monday, I plan to have the whole system running up a ramp for two feet, while adjusting its platform. I will need to change the setup for the Arduino system such that are linear actuators extend halfway at the very start. Then, to make any adjustments, both linear actuators will run, but in opposite directions, so that we can increase the speed at which we change the angle of our platform. Then I will continue working on the control algorithm such that it reacts immediately to any change in slope, and try to reduce any oscillations.