Essays & explorations / 10 essays
Learning robotics.
Experiments, diagrams, and questions from learning how robots move, learn, and make decisions.
Series / 6 parts
From policy to action: the last mile of robotics control
One equation, and every way the arm misses it
Start from torque = inertia × acceleration, then add each term a cheap servo arm really has: gravity, friction, a payload, dead time, a dead band. Each term is one way the arm misses its target.
Seeing finer than the sensor
The sensor side of the joint equation: why differences of encoder ticks explode the noise, and how an observer or a Kalman filter can estimate an angle finer than one tick.
Six ways to choose the goal
One general formula for the goal sent to a servo. Every controller I built, from a plain look-ahead to MPC, is that formula with some terms set to zero.
Learning what the physics misses
Where a neural network fits in a robot controller. A network that learns only what the physics model gets wrong does the same job as a Kalman disturbance estimate, with more freedom, and this is where recent research is going.
A pen holder that shows the arm’s error, not its own
I want to see my SO-101 trajectory errors as ink on paper. For that, the pen must not add an error of its own. I made five holder designs. The one I release is a printed sleeve that slides onto the stock gripper: 4 printed parts, nothing to buy, any pen from 8 to 13 mm.
Where the last millimeter of my drawing arm goes
My SO-101 arm cannot see its own pen tip. A tablet can. Here is what the tablet showed: how much error a learned correction removes, which causes are left, and why the base joint matters most.
A few predictions about robotics
If intelligence keeps getting cheaper, the robotics industry may start to look more like a combination of AI infrastructure, industrial services, and manufacturing.
How robot control is changing
From copying a person to practicing and imagining: how a robot chooses its next movement in 2026, and what is still missing.
Why I am learning robotics
The most impressive robots of the last decade stayed in videos because they could not generalize. Language models changed that, and robotics now looks like language models in 2019.
How an arm moves: joints, geometry, and motor control
From encoder readings to gripper position: a visual guide to robot geometry, servos, and the commands that connect them.