This article from Tyto Robotics explores key considerations when deciding between constructing your own drone test stand or opting to buy one for your project.
Each year, we encounter clients who have attempted to create their own test stands to evaluate their drone motors and propellers. While some clients report achieving their goals, many express that the resources spent were disproportionate to the outcomes, leading them to lose sight of their primary project objectives.
If you find yourself in a similar dilemma—debating whether to build or buy a test stand—this article aims to shed light on factors you may not have considered.
In a highly competitive industry, time to market is crucial. Our test stands are typically available for immediate shipment, allowing you to commence testing within days of placing your order.
(This article focuses on professional drone builds and associated test stands.)
Figure 1: Progression from an early Series 1580 prototype (left) to the latest Flight Stand 15/50
1. Electromagnetic Interference (EMI)
Drone motors produce important electromagnetic interference, which can introduce noise into measurements and potentially cause USB data loggers to malfunction, as we’ve learned through our research and development. Identifying these issues can be challenging, so it’s advisable to meticulously design and simulate electrical connections from the outset. Allocating time for diagnosing EMI problems is essential, and consulting an electronics engineer with expertise in power electronics, EMI, and grounding is recommended.
2. Selecting Appropriate Load Cells
Our findings indicate that sourcing a commercial multi-axis load cell capable of measuring both torque and thrust simultaneously, with the correct thrust-to-torque ratio, is quite challenging. This often results in one of the measurements not utilizing the load cell’s full scale, leading to reduced accuracy. Additionally, our load cells are engineered to minimize airflow restrictions while maintaining a slim profile for testing coaxial systems, a level of specialization not typically found in commercially available options.
3. Calibration and Validation
Acquiring the right load cells is merely the frist step; designing a calibration method and validating it is another significant task. In powertrain testing,thrust and torque rarely occur in isolation; thus,it’s vital to calibrate the load cells under operational conditions,accounting for crosstalk when generating the calibration polynomial. Without a calibration machine, re-calibrating after extensive use becomes unachievable. That’s why we calibrate all our load cells in-house to ASTM standards and offer clients the option for annual re-calibration of their force measurement units.
4. Software Development
In creating our latest generation of test equipment, the software redesign was as time-consuming as the hardware overhaul. The complexity of the software is contingent on the desired features, but at a minimum, it must control the test stand and log data effectively.
The flight Stand software (see figure 2) manages the test stand through both manual and automated testing, displays real-time data on customizable graphs, stores and presents saved data, prepares data for export, and includes numerous additional data processing features (refer to part 5).Notably, it performs all these functions simultaneously at a sampling rate of 1,000 Hz.
Figure 2: User Interface of the Flight Stand Software
5. Data Management
Beyond mere data recording, the processing of that data can significantly influence your workload. We have integrated several features into our software to streamline data handling and analysis:
- Incorporating a low-pass filter option to smooth data
- Resampling data at various frequencies
- Mapping powertrain performance
While these features require programming time, they ultimately save users time and enhance practicality.
6. Safety and Mechanical testing
Designing a test stand can present unexpected challenges,such as identifying the stand’s resonance frequencies and mitigating vibrations. Without knowledge of these frequencies, you risk damaging both the stand and the propulsion system. Balancing stability and measurement accuracy in the face of vibration can be a complex task.
7. Coaxial Testing Setups
Once you have mastered a single-rotor testing configuration, you may wish to explore testing dual motors in coaxial or offset arrangements. While face-to-face propeller setups are relatively straightforward, back-to-back configurations, common in many quadcopters, pose greater challenges. Achieving a close rotor proximity requires meticulous design and planning. our Flight Stand 15/50 (see figure 3) allows coaxial setups to operate safely in a back-to-back configuration with only 9 mm of separation, translating to approximately 91 mm between motors.
Figure 3: Flight Stand 50 in a back-to-back coaxial configuration
8.Creating a Compact Solution to Minimize Airflow Disruption
Another critical aspect that demands considerable development time is crafting a compact test solution. If the test stand interferes excessively with the airflow generated by your propellers, it can skew your readings. Designing a compact solution that maintains stability without compromising performance is a time-intensive process.
A key focus during the redesign of our test stands was to achieve a compact form that minimally disrupts airflow, ideally less than or only slightly more than the motor itself.
9. Performance Issues Due to Inaccurate Measurements
This is a scenario that all drone developers fear: constructing an aircraft based on data believed to be reliable, only to discover that the prototype’s performance falls short of expectations.
Our test stands boast an error rate of less than 0.5%, ensuring that the results are highly precise.
Conclusion
While our test stands may not always align perfectly with your project needs, we hope this article equips you with the insights necessary to make an informed decision about whether to build your own test stand or purchase one for your project.
