89 developers aim for most prominently, from R&D through to production. When it comes to engineering new products, the fight for reliability starts at the high level architectures of different controller designs, before filtering down into the board-level components. As a general rule, achieving a holistic integration in which all the components on the board work well together will take an ESC far, as will selection of efficient and long-lasting components. This can mean high-end silicon MOSFETs and low-impedance capacitors, for instance. Beyond that, one architectural approach which has proven effective has been to use over-specced components with current and thermal operating limits considerably higher than expected operating requirements. While that might not sound inherently efficient, given that right-sizing seems to be the name of the game in so many electric and autonomous vehicle projects, one of the leading reasons why hobby-grade ESCs fail to live up to UAVs’ reliability requirements is that they run on parts whose limits run extremely close to where their platforms operate. When no headroom is left for current or heat spikes among the MOSFETs, capacitors and elsewhere, critical failure is likely to follow in short order. Another approach has been to separate hardware and firmware into independently modular and optimisable systems through a chiplet-focused motor control board architecture. Discussed in detail in our last investigation of embedded computing systems (see issue 59), chiplets are, in essence, highly size-optimised devices resembling system-on-chip products that subsume most (if not all) of the central processing functions on a PCB, with secondary and tertiary functions then distributed to other integrated circuits nearby. In this approach, a chiplet featuring a microcontroller, numerous I/Os, and other components (and embedding one universally-applicable firmware platform) sits at the centre of an ESC’s layout, amid the capacitors, MOSFETs, gate drivers, terminals and so forth. Due to its plethora of I/Os and the one-size fits-all way its embedded logic is written, the way that chiplet interfaces with other ESC components is pre-defined for any bridge topology. Hence it can control small, 20 A drives, or a heavy 30 kW system, and anything between seamlessly. This results in several key benefits; for one, lead times for customised motor controllers are considerably reduced (sometimes taking little more than a month), as firmware and central processors need not be created anew or even significantly modified for running a new, bespoke solution. That greatly accelerates product development cycles and makes the motor controller manufacturer more agile in fulfilling the needs of new uncrewed systems and their powertrains. It also makes the firmware itself far easier to test, validate and improve upon, as new fixes or subroutines can be proven out in real-world conditions on small, inexpensive flight test aircraft. Even if unrepresentative of the intended recipient aircraft of a new software fix or add-on, the new functionalities can still be triggered on a smaller platform, with no significant loss if the test drone crashes due to an excessive thrust or overcorrection behaviour. Chiplets for motor controllers are not, as of writing, topologically dissimilar from very small PCBs, or something available off-the-shelf just yet. Those we have seen are proprietary creations which took years of optimisation work on firmware, hardware stamping, SWaP, performance and reliability. For a motor controller manufacturer to produce such a system and hence an ESC architecture around it, takes considerable in-house resources for circuit board assembly and production. Additionally, copious testing hours – running into the hundreds of thousands on bench and aircraft – are vital to affirming that such a chiplet can be trusted as a universal core for different ESC and motor drive permutations. And while high-end motor controllers today are reaching MTBFs of 4000 hours, matching the lengthiest lifespans of e-motors and UAVs in many cases, any further extensions to ESC operating lifetimes remain limited by the capacitors. As we reported in our previous investigation (see issue 35), Motor controllers | Focus Uncrewed Systems Technology | April/May 2025 Prudent integration of high-efficiency power transistors, low-impedance capacitors, and highly optimised firmware are all crucial to reliability and hence certification (Image courtesy of Currawong)
RkJQdWJsaXNoZXIy MjI2Mzk4