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 for rapid prototyping, equipped with NVIDIA Jetsons, high-end scopes, and 3-D printers.

• 100% Employer-Paid Premiums: We cover 100% of your medical, dental, and vision insurance premiums and cover 50% of healthcare premiums for your dependents.

• Unlimited PTO: We value results, not clock-watching. Take the time you need to stay sharp and recharge.

• Zero Red Tape: You report to the founders. You have the autonomy to make technical decisions that would take months of committee approval at a larger firm.

• Austin-Based Culture: Join an onsite team in Austin, TX, where we prioritize high-bandwidth collaboration and rapid field-testing.

• Relocation Assistance: We want the best talent in the room. If you aren't in Austin yet, we’ll help you get here, to make your transition to the Silicon Hills seamless.

About the Interview

• Virtual interview (45 min via MS Teams)

• Onsite interview in Austin (1.5 hr in-person)