Michael E. Holden
California State Maritime Academy Sabbatical Fall 2024
This report shares the results of my Fall 2024 Sabbatical project. It will get into the details pretty thoroughly, with links and files so I can find all the work in one place in the future, so feel free to skip around to the good parts. For a more visual feel you can follow the insta-blog at n3m0_the_robot_boat.
Continue reading “Surface Current Measurement and Route Optimization Using Autonomous Boats”
This report documents the transition of n3m0 the autonomous boat, originally a monohull designed for long-ish range water-quality measuring missions, to n3m02 the autonomous catamaran. The mission was to add a depth sensor to the boat so that it could survey the harbor at Cal Maritime. The harbor silts in pretty quickly and it is an expensive and time-consuming process to dredge, so keeping tabs on the depth over time was the goal. A transom-mount NMEA-1083 speed/depth/temperature transducer was added to the boat, and a raspberry pi was used to log the position of the boat from the autopilot and the depth from the sensor. The data was uploaded in real time to github, which worked quite well! Eventually a second hull was added to allow differential thrust and improve maneuverability when running next to docks and moored vessels. Read on for more information!
Continue reading “n3m02 the Autonomous Boat: Depth Surveys”revisited after 20 years! by Michael E. Holden
Continue reading “Low-Cost Autonomous Vehicles Using Just GPS”Sometimes students or other nice people ask about my Ph.D. thesis. Probably just being polite. Well, here it is.
I earned my Doctor of Philosophy in Aeronautics and Astronautics from Stanford University in 1999
Continue reading “Ph.D.”I built N4N1 to learn the details of the ardupilot sailboat firmware. I have had a few student groups building similar vessels at work, and thought it would be worthwhile to go through the exercise myself. Plus I had a boat gathering dust that needed a job.
N4N1 uses the ardupilot sailboat firmware on a Matek flight controller, with external GPS, compass, and wind vane.
N4N1’s hull was designed and built by me in the previous century, and with the rig from an RC Laser, she sails autonomously on San Francisco Bay.
Continue reading “N4N1 the Autonomous Sailboat”Pet chickens like to run around and scratch up their yard during the day, but must be safely locked away at night to prevent predators from eating them. Most chicken-keepers accept the twice-daily chore of letting the hens out in the morning, and locking them up at night. This is a project to automate that task using an inexpensive sensor, an arduino microcontroller, and a linear actuator. As a bonus this project runs from a solar-charged battery!
This project is pretty hacky looking or you could say it has an agricultural feel to it, but it’s been running solid for over a month so I thought I would record it here. Bring on the bailing wire!
Back in 2019 I made a remote controlled lawnmower. It is not a very original design, it follows closely the mower from Make Magazine and many other youtube videos, with some modifications to suit what parts I could get. I got an electric wheelchair and an electric mower second-hand, bought a speed controller and some relays, and made my own RC controller and receiver with arduinos and nRF24L01 radio set. I tried my best to keep the cost low, using as many second-hand parts or things I already had in my shop. This mower has been mowing my lawn ever since, and makes a tedious chore fun! I highly recommend building one if you still push a mower yourself.
Continue reading “Lawnie the Remote Controlled Lawnmower”
This project documents how to make a windvane to sense the wind direction. It was designed for an autonomous sailboat but could be used in other applications. The structure is mostly 3D printed and uses a gopro mount to attach to the hull. The main sensor is a magnetic encoder that outputs an analog voltage in the 0-5V range. For my application I used a voltage divider to bring that down to 0-2.5V because my autopilot is based on 3.3V logic. I also have an arduino program to output the vane angle as NMEA 0183 serial data; I don’t use this on my boat but it is a standard digital interface that might be helpful for others.
Continue reading “Electronic Windvane”This is mostly just to link the video I made. It shows how to run mission planner (ground control station) and start a simulation of an autonomous sailboat (SITL), and how to run the boat in autonomous modes, including tacking parameters and geofencing. Enjoy!
Using ardupilot with a telemetry radio to send data to your groundstation is the easiest setup and works very well. It is limited by RF range, which is determined by the radio power (more power gives more range but costs more and may require a ham radio license). The range also depends on good line-of-sight between the radios.
It is tempting to take advantage of cellular networks to increase the range. Can a wireless data hotspot on your ardupilot vehicle give “infinite” range? This article shows how to set it up using a raspberry pi as the wifi bridge. You also need a mobile hotspot (either a standalone device or a cell phone in AP mode).
Continue reading “Ardupilot with Mobile Data Telemetry”
