New Tech Tuesdays: Engineering Reliability into Commercial Drones
Key Highlights
- Motor-current sensing provides feedback on propulsion loads and can help detect overloads, short circuits, and other electrical faults.
- Extending flight time requires managing losses across the power chain, not simply increasing battery capacity.
- Compact, low-resistance magnetic current sensors can help limit heat and conduction losses across multiple propulsion channels.
New Tech Tuesdays
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Remote-controlled (RC) aircraft once meant foam wings, bulky transmitters, and a flight that had a high probability of ending in a tree. Today’s commercial drones—the descendants of those RC aircraft—are much more advanced, offering capabilities such as spreading fertilizer, capturing digital imagery, and transporting packages, among other things. Yet, while the aircraft may be more capable, every additional feature competes for the same limited battery capacity, weight allowance, and space.
Successful commercial drone design requires more than selecting an efficient motor or low-power sensor. This week’s New Tech Tuesdays examines how coordinated power management, propulsion control, and magnetic sensing can support reliable flight, protect critical circuitry, and preserve the energy available for its application-specific functions.
Commercial Drone Design Starts with the Propulsion Chain
A drone’s propeller motors produce the thrust required for vertical lift, directional movement, and attitude control. Each propulsion channel typically combines power conversion, a motor driver, current sensing, and closed-loop motor control. If these elements do not operate together effectively, the result can be wasteful operation, unstable movement, or inadequate protection against electrical faults.
Motor current provides useful feedback because it corresponds to the torque the motor produces. By monitoring current near the motor, the control system gains visibility into changing propulsion loads and can detect overcurrent conditions caused by overloads, short circuits, or other faults.[1] Magnetic current sensors perform this measurement without requiring direct electrical contact between the current-carrying conductor and the sensing circuitry. Depending on the implementation, they can also provide galvanic isolation between the power conductor path and measurement circuitry.
Sensor size and conductor resistance also matter. A compact sensor can fit close to the motor-drive circuitry, while low resistance helps limit conduction losses and heat generation. These characteristics are particularly important in multirotor aircraft because the circuitry is repeated across several propulsion channels.
Flight Time Is a System-Level Challenge
When a drone needs more time in the air, attention typically turns to the battery. Battery capacity is important, but adding a larger battery increases mass, which can require additional thrust and larger propellers, and can consume some of the energy the larger battery was intended to provide.
A more complete approach evaluates losses throughout the power chain. Battery monitoring, direct current-to-direct current (DC/DC) conversion, motor-current sensing, gate driving, lighting, and position sensing all contribute to the total energy budget. Reducing consumption and conduction losses at multiple points may be more practical than relying on a single component change to extend flight time automatically.
Power monitoring also gives the control system better visibility into the battery’s operating state, while efficient voltage regulation supplies lower-voltage electronics without unnecessarily consuming energy reserved for propulsion. The objective is not simply to minimize the power used by each component, but to coordinate the entire chain so that sensing, protection, and control do not impose excessive losses.
Magnetic Sensing Beyond the Propellers
Propulsion may keep a drone airborne, but position sensing helps many of its other functions operate predictably. A camera gimbal, for example, needs to measure angular position so its motors can compensate for aircraft movement and maintain a stable field of view (FOV). Magnetic position sensors can provide contactless angular feedback in compact mechanical assemblies, including configurations that measure movement along one, two, or three axes.[2]
Similar sensing principles apply to handheld controllers. Joysticks, buttons, and triggers experience repeated movement throughout their operating lives. Replacing mechanically contacting position elements with magnetic sensing can reduce wear while maintaining consistent position feedback. Low-power operating modes can further limit controller battery consumption when an input is inactive.
Sensor selection still requires attention to magnetic range, accuracy, linearity, bandwidth, mechanical alignment, and nearby magnetic fields. Contactless operation removes a mechanical wear point, but it does not remove the need for careful design. Physics is still physics.
Sources
[1] https://www.allegromicro.com/en/insights-and-innovations/blogs/current-sensors-in-robotics
[2] https://www.allegromicro.com/en/insights-and-innovations/technical-documents/magnetic-position-sensors-in-robotics
