Big Yard? Get in Line for an RC Riding Lawnmower

Jesse Brockmann has set out to make a John Deere tractor autonomous.

Cabe Atwell
3 years agoRobotics

Inspired by an attendee at a STEM event, senior software engineer, Jesse Brockmann, set out to convert a John Deere riding lawnmower to autonomous. Because, why not? Autonomous vehicles are designed and engineered with the ability to drive from point A to point B without external (e.g. human) assistance. Features such as “sensors, adaptive cruise control, active steering (steer by wire), anti-lock braking systems (brake by wire), GPS navigation technology, lasers and radar” make this possible.

While Brockmann’s ultimate goal is to create a fully autonomous riding lawnmower, he first set out to build a remote-controlled riding lawnmower in phase one of his project. This first phase includes the following components:

  • Braking: 35-pound linear actuator with a built-in potentiometer for feedback.
  • Throttle: Remove friction; use standard RC car servo to move throttle; attach wire to potentiometer signal to get feedback on throttle value as safety feature; linkage used to connect servo horn to carburetor.
  • Steering: Motor with 680 ounce/inch and 160 RPM ratings; gear ratio of 1:3 between motor and steering shaft; potentiometer for position feedback on front steering knuckle; size #25 chain to connect geared motor to steering sprocket.
  • Shifting: Custom mount to shift between second gear, neutral, and reverse.
  • Kill switch: Relay across ignition switch wires.
  • Controller: First-generation rover board with Teensy 3.2, car-style transmitter, and receiver; new circuit breaker with fuse block and switches to power the new control systems.

With the above parts assembled, Brockmann ran an initial test of the new components. He then set to work on developing the code and software for the remote-controlled system with these modes: INIT, START, STOP, RUNNING, FAILSAFE, MANUAL, and KILL. Next, he tested the logic behind switching to different modes and then tested control systems in isolation. Then he tested the entire system on the mower without driving it. Finally, he used the remote control to drive the riding lawnmower.

During this stage, Brockmann also made several modifications:

  • Resolved an issue with the gas engine;
  • Added a heat shield to the muffler to prevent damage to the servo;
  • Attached a guard to the brake’s linear actuator;
  • Installed guides for the shifter to promote accuracy and prevent jamming;
  • Added a steering guard to protect the chain; and
  • Installed a kill switch with tether to the back of the mower.

He even plans to use a current sensor to detect when an actuator stalls.

When time permits, Brockmann hopes to transition from remote-controlled phase, to autonomous phase testing with 1/10th or 1/5th scale rovers with u-blox ZED-F9P RTK GPS and sensors, to a fully autonomous riding lawnmower.

You can follow along with his progress on the SparkFun blog.

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