HIL Test Engineer

Mill is a waste prevention technology company reimagining what it means to eliminate waste, starting with food. We build smart systems and infrastructure for homes, businesses, and municipalities that transform food scraps from landfill-bound waste into valuable resources, including chicken feed. Tens of thousands of Mill’s residential food recyclers are already helping households divert millions of pounds of food scraps every year, paving the way for our upcoming launch of Mill Commercial—the industry’s first end-to-end solution for managing, understanding, and preventing food waste in commercial environments (e.g. grocery, restaurants, food services). At Mill, we are passionate about building easy-to-use, beautifully designed technologies that keep food in the food system and out of landfills.

About the Role

We're looking for a Hardware-in-the-Loop (HIL) Test Engineer to own the test station for Mill Commercial's program including hardware, sensor and actuator emulation, and plant models: systems to emulate include safety interlocks, load cells, motor feedback, thermocouples, and heater elements.

This is a hands-on, build-and-maintain role. You'll take the station from vendor commissioning to a working bench, then keep extending it: adding channels and fault-injection paths, writing and tweaking the thermal and torque plant models in Simulink, and turning engineering requirements into automated tests that run in CI. You'll work day to day with Firmware, Systems, Test Engineering and EE, and you'll be the person who knows why a test passed or failed at the signal level.

What You'll Do

• Own the HIL test station end to end: rig hardware, I/O and emulation modules, wiring and harnessing to the DUT, power and reset control, and the bench equipment around it

• Lead vendor commissioning and bring-up, then take over the station as the in-house owner once the vendor hands off

• Build and maintain plant models in Simulink (oil jacket thermal, air heater and airflow, vessel cool-down, grinder load torque) and keep them correlated against real-device data

• Extend the rig to cover new tests: add emulation channels, fault-injection paths (thermocouple open/short/drift, disconnected interlock lines, degraded tach signals) and timing capture as the test plan grows.

• Translate engineering and safety requirements into automated HIL test cases with programmatic pass/fail, and integrate them into the Linux-based CI regression

• Debug failures to root cause across the rig, the plant model and the firmware, working with Firmware and EE to tell a real defect from a test-infrastructure issue

• Keep the station reliable: calibration, spares, documentation, and a known-good configuration that other engineers can run tests on without you

• Partner with SW QA to define test plan based on product requirements and ensure the station can test all cases

• Partner with Systems and Test Engineering on the boundary between HIL coverage, bare-board tests and full-system tests

What We're Looking For

• 4+ years in test, controls or systems engineering on electromechanical products, with at least 2 years hands-on with HIL or real-time simulation rigs

• Strong Simulink and MATLAB: you've built and tuned plant models (thermal, mechanical or electrical) and deployed them to a real-time target

• Able to read and trace C code: you can follow firmware control logic well enough to understand what a test is exercising and where a failure originates

• Comfortable with signal-level work: thermocouples, strain gauges, hall-effect and discrete inputs, PWM drive lines, and the I/O modules that emulate them

• Practical bench skills: wiring, harness build, oscilloscope and DMM work

• Strong documentation and organization skills

• Experience with test automation: scripting test sequences, programmatic pass/fail, results logging, and integrating into a regression pipeline

• Clear, direct communicator: you write test cases others can run and you explain rig behavior to firmware engineers in their terms

Nice to Have

• Hands-on experience with Speedgoat, dSPACE, NI VeriStand or similar HIL hardware, including Simulink Real-Time or an equivalent toolchain

• Experience working with Linux-based embedded systems (Jetson, Yocto or Debian-class targets) and Linux CI tooling

• Familiarity with standard automation APIs such as ASAM XIL, or with Python-based test frameworks and MQTT

• Background in safety and interlock testing, fault injection, or functional-safety test methods

• Experience with thermal or motor-drive systems: heaters, PID loops, DC motor torque and current limiting

• Experience at an early-stage hardware startup, where you set up the process rather than inherit it

The estimated base salary range for this position is $165K to $185K, which does not include the value of benefits or a potential equity grant. A wide range of factors are considered in making compensation decisions, including but not limited to skill sets, market conditions, experience and training, licensure and certifications, and business and organizational needs.