Thrust Testing
To provide Vertiq’s partners and those interested in our propulsion modules with the most relevant data possible, we conduct and publish thorough thrust testing data using many different third-party propellers.
First, we must determine what sizes of propellers we want to collect and publish data for each specific module. We’ve used all of our previous testing data to develop our own internal program to simulate props on our motor modules at different supply voltages, so this step is relatively straightforward. Props that are too large for the module will hit its previously determined continuous torque limit at a low velocity and low commanded voltage. Props that are too small for the module will hit the maximum commanded voltage and max velocity without creating much thrust or getting near the continuous torque limit.
Once we have determined the appropriate range of propellers to test for a specific motor module, we prepare the test on our internally developed thrust test stand. Our motor/ESC module gets mounted to an ATI Mini85 Force/Torque sensor. This F/T sensor is sensitive to temperature change, so we avoid mounting our module to the sensor directly. We also avoid mounting it to thermally conductive materials that would transfer the heat from the motor/ESC to the sensor. Instead, we fasten the module to a thick nylon mounting plate that sits between the module and the sensor. This non-conductive surface protects our F/T sensor from drastic temperature changes. It also keeps our data as honest as possible. Because our mounting plate is not a thermally conductive surface, we are not adding any additional heat sinking or cooling to our setup.
While mounting the motor module to the stand, we also attach a small IR sensor with a mount that is specifically designed for the exact module we are testing. The mount ensures the IR sensor barrel is pointed directly at one of the coils. We use this coil temperature data specifically for tuning our coil temperature estimator model. While this exact coil temperature data is not shared on the website, it is helpful for us to understand everything that was going on while testing different propellers.
We also keep a temperature, pressure, and humidity sensor in the testing room while conducting tests and note these conditions at the top of all our published data. Everything feeds back to a National Instruments DAQ.
Once the motor module and IR sensor are mounted correctly, we mount the first propeller using the proper adapters. Next, we configure our power supplies to the appropriate voltage for the test we are about to run. For larger propellers, we can supply a lower voltage since they will hit our continuous torque limit at a lower velocity. For smaller props, we typically supply the highest recommended operating voltage for that module in order to spin as fast as possible in our test.
For example, you can see when testing a 28” propeller on our 60-08 150Kv G2 Module, we supplied 24V. When testing a 20” propeller on that same module, we supplied 48V. Both hit the modules continuous torque limit of 1.05Nm, just at different commanded voltage steps/velocities. There was no need to supply 48V during the 28” propeller test since the module hit its continuous torque limit around 22V Commanded Voltage.
We do not publish steps in the test that occurred, but pushed the motor module beyond what we have determined to be its continuous torque limit. These numbers were able to be hit, but would not be sustainable for a customer without the module derating to protect itself from overheating to the point of damage.
Once we connect power and comms to the motor module, it is time to get spinning. For our test script, we use Voltage Mode and IQUART to communicate. We step the Commanded Voltage in increments of 1 or 2V from 0V to supply voltage. We spin at each voltage for a sufficient amount of time to collect smooth data.
After the final step of the test (either max voltage commanded or derating above max continuous torque ), we run a continuous, steady state test. The purpose of this steady state portion is to collect the Convection Thermal Conductivity Coefficient for that specific propeller on that specific motor module. This value helps keep our internal coil temperature estimator model as accurate as possible and should be adjusted for different props because of the different airflow and cooling they create. We populate the Convection Thermal Conductivity Coefficient along with velocity feed forward values (collected from the voltage sweep) as default configuration files on IQ Control Center. Because we’ve already done the work in collecting these values, the end user can simply select what propeller they are using and have these typically tricky to determine values auto-populate for them.
We currently have ~100 different propeller thrust tests with our different motor/ESC options published on our website. As we continue to release new modules, this number will continue to grow. If there is a specific prop/module combo that you would like to see tested, please reach out to us.
