James Bruton, independent robotics creator, explains how to build and balance a five-servo bipedal robot using an ESP32, an inertial measurement unit, and 3D-printed parts.
Bruton presents the robot as the third project in a series of accessible builds, following a mini robot dog and a hexapod. He aims for active balance and clear foot lifts, using five standard RC servos and an ESP32. He provides editable STEP models and open-source code, while excluding AI training from the project.
The frame uses printed parts, 4 mm stainless-steel rods at key pivots, and metal-geared MS62 servos rated at 25 kg·cm and 270 degrees. Parallelogram linkages let two servos drive each leg, while a fifth servo and gears coordinate turning. Bruton stresses accurate alignment and mass distribution, and adds soft TPU feet to cushion contact.
Two ESP32 boards communicate directly through ESP-NOW: one sits in a joystick remote, and the other receives commands on the robot. A SparkFun BNO086 IMU measures the robot's side-to-side tilt. The robot runs from a 2S LiPo battery, with separate switches for servo and controller power.
Bruton uses trigonometry to map desired foot positions to servo angles, then interpolates foot movement with the Arduino Ramp library. Early tests show the robot falling or sticking to one side, so he adds IMU-based corrections and adjusts step timing. Widening the stance, adding nuts for more inertia, and removing a dragging USB cable improve its consistency.
Joystick input controls forward and backward steps, while another axis commands turns; the robot can also combine the motions to walk in a curve. It walks on carpet and a workbench, though smooth tiles expose poor grip and added cushioning changes the dynamics. Bruton finds that two extra nuts restore stability with grippy foot material, and notes that builders may need to experiment with weight and sole surfaces.
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James Bruton, engineer and creator at James Bruton, explains the walking machine’s rotary and sliding systems, controls, and first tests, then demonstrates it at Formnext 2025 in Frankfurt with Matt Denton.
