Sr. Mechatronics Engineer - Actuation & Drivetrain

Location : Onsite — Austin, TX

Employment Type : Direct Hire, Full‑Time

Job Title : Senior Mechatronics Engineer - Actuation & Drivetrain

About 9 Mothers

The modern battlefield has changed. Cheap, autonomous suicide drones have turned the tactical advantage upside down, and the world is looking for a solution. At 9 Mothers, we aren’t just "innovating"—we are building the shield.

Backed by top-tier investors, we develop AI powered machines designed to intercept and neutralize Group 1/sUAS threats in real-time. Our flagship product is a low-power, counter-drone system built for the edge—on vehicles, at bases, or in a soldier's pack.

Why 9 Mothers?

While others build for "awareness" or "long-term research," we build for the immediate survival of those in harm’s way. We are a team of hackers, engineers, and mission-driven builders who value field-ready capability over polished slide decks. If you want to see your code or hardware in the field next month—not next year—this is your playground.

Position Summary

EDDA is only as good as its actuators, and we're hiring the person who owns them. You will be our servo wizard: the single owner of every motor, actuator, gearbox and solenoid in the product, from the first torque and inertia calculation through supplier selection, bench characterization, control-loop tuning, abuse testing and production release. You are as fluent in gearbox design — backlash, torsional stiffness, efficiency, lubrication, lifetime — as you are inside the current loop of the servo driving it. And you have lived with motion systems that get rained on, dropped, fired next to and bounced across a field on the back of a truck.

What You'll Own

Everything in the product that converts electrons into motion is yours — the parts, the suppliers, the test data and the tuning.

Motors and actuators: BLDC/PMSM and frameless torque motors, steppers where they earn their place, linear actuators — every axis that moves EDDA's azimuth, elevation and auxiliary mechanisms.

Gearboxes and drivetrain: planetary, strain-wave (harmonic), cycloidal, worm and belt stages; the direct-drive-versus-geared call on each axis; bearing arrangements, preload, backlash and the stiffness budget that sets achievable control bandwidth.

Solenoids and discrete actuators: latches, safeties, indexing and release mechanisms — the fast, simple actuators that must work every time, in the cold, after being dropped.

Motor drives and tuning: drive selection or specification, commutation and feedback (encoders, resolvers, Hall sensors), current/velocity/position loop tuning, feedforward and filtering.

Characterization and test: dynamometer and bench rigs, thermal derating, torque ripple and cogging, efficiency maps, endurance and abuse testing, and the acceptance tests production runs on every unit.

The actuation supply chain: vendor qualification, custom motor and gearbox specifications, second sources, cost-down and the lead times that production depends on.

Essential Duties

Size and select: turn slew-rate, acceleration, pointing-accuracy and duty-cycle requirements into torque, speed, reflected-inertia and thermal budgets; pick or specify the motor, gear ratio and drive that meet them with margin — and show the math.

Design the drivetrain: own the mechanical path from rotor to load — gear stages, couplings, shafts, bearings, preload, lubrication and seals — and the stiffness and backlash budget that determines how hard the loops can be pushed.

Characterize everything: build the rigs and run the tests — torque constant, back-EMF, inductance, cogging and ripple, friction and stiction, efficiency, thermal rise, backlash and lost motion — so tuning starts from a measured plant, not a datasheet.

Tune the loops: commission and tune current, velocity and position loops (PID, feedforward, notch filters, observers) for aggressive high-bandwidth tracking without exciting structural modes or cooking the motor.

Engineer for abuse: design and qualify actuation for shock and vibration from vehicle mounts and weapon firing, dust, mud, water, salt, EMI and temperature extremes; lead failure analysis when hardware comes back from the range broken, and make sure the next revision doesn't.

Own the supply chain: qualify vendors, write motor, gearbox and solenoid specifications, manage second sources and lead times, and drive cost-down for production volumes.

Bridge the teams: be the technical interface between mechanical, electrical, firmware and robotics on anything that moves; triage failures at the hardware-software boundary and call whether a problem is mechanical, electrical or control.

Document and release: derating curves, tuning procedures, acceptance tests and drawings that production and field teams can execute without you in the room.

Requirements

Experience: 10+ years in mechatronics or motion-system engineering with a track record of shipping servo-driven products — ideally pan-tilt units, gimbals, turrets, robotic joints or vehicle-mounted systems.

Servo depth: hands-on selection, commissioning and tuning of BLDC/PMSM servo systems: field-oriented control, current/velocity/position loops, encoder and resolver feedback, drive configuration, and diagnosing instability, resonance and thermal limits on the bench.

Gearbox fluency: working command of planetary, strain-wave, cycloidal and worm drives — ratio selection, efficiency, backlash, torsional stiffness, lubrication and lifetime — and a clear sense of when direct drive beats gearing.

Actuator characterization: you have built test rigs and run dynamometer, thermal, efficiency and endurance tests; comfortable with scopes, current probes, DAQ and Python or MATLAB to extract plant parameters from data.

Drivetrain design: can design and detail the mechanical path from rotor to load — bearings, shafts, couplings, seals, preload — in CAD (SolidWorks or similar) with tolerance analysis.

Programming: enough C/C++ or Python to configure drives, automate tests and prototype control code; comfortable reading motor-control firmware.

Supplier management: have specified custom motors or gearboxes with vendors and run qualification, second-sourcing and cost-down.

Hands-on rigor: you build, break, measure and fix your own hardware.

Compliance: U.S. citizenship and the ability to pass a background check.

Nice‑to‑Have

Harsh-environment qualification: MIL-STD-810 shock and vibration, IP-rated sealing, EMI/EMC, thermal cycling — and the scars from hardware that was abused in the field anyway.

Weapon-mounted, recoil-loaded or vehicle-mounted motion systems.

Custom motor design: frameless, outer-rotor or slotless motors and magnetics; electromagnetic FEA (Ansys Maxwell, JMAG, FEMM).

Solenoid and voice-coil design: force-stroke-thermal trade-offs, PWM hold, fast actuation.

Structural dynamics: modal analysis and designing control around structural modes; stabilization on a moving platform.

Advanced control: model-predictive, adaptive or disturbance-observer control.

Drive ecosystems: CAN, EtherCAT, ROS 2/DDS; hands-on time with ODrive, moteus, Elmo, Copley, Kollmorgen or similar drives.

Production experience: DFM, incoming inspection and acceptance-test procedures for actuators.

Security clearance or the ability to obtain one.

You build robots, race drones or rebuild machinery on your own time.

Benefits

Meaningful Early Equity: You aren't just an employee; you are a foundational owner. Your contributions directly drive the value of your stake in the company.

Direct Roadmap Influence: Forget the bureaucracy of big defense. You will have a seat at the table, directly shaping our product and technology trajectory from day one.

Mission-Critical Work: We don't build for "what if." We build systems the Department of War actively needs to counter immediate, real-world threats.

The Builder's Playground: Work in a brand-new lab fully optimized