Q8bot: Palm-sized quadruped robot jumps, redefines design with no wires

The robot features a custom PCB that serves as its backbone, linking eight servos directly to onboard connectors.

Jijo Malayil

Q8bot is a small, agile quadruped robot powered by eight Dynamixel motors.

Yufeng Eric Wu/YouTube

Meet Q8bot, a palm-sized robot that resembles a miniaturized version of the famous Boston Dynamics’ Spot quadruped.Designed by Eric Yufeng, this small four-legged robot has all its parts, including the actuators, built directly onto its circuit board.

The robot uses a custom PCB as its backbone, connecting eight servos directly to onboard connectors.

The robot also features 3D-printed frames that hold the servos and battery. Its minimalist electronics include an ESP32C3 module, boost converter and battery gauge. Its legs have four 3D-printed segments with press-fit bearings.

The Q8bot stands out for its mechanical simplicity. It has no external wires or cables. All components are plugged directly into a central PCB, minimizing complexity, weight, and cost.

Despite its clean design, Q8bot is agile and capable of movements like jumping and walking, as shown in demonstrations. This project highlights a blend of mechanical design, electronics, firmware development, and robotics skills.

The assembly process is straightforward: two 3D-printed frames hold the central PCB and act as battery holders. Servos attach using internal fasteners, and five-bar linkages serve as the robot’s legs. The only internal wiring is within the motors themselves.

According to its maker, Q8bot’s design prioritizes manufacturing efficiency, with many custom parts mirrored on both sides to reduce unique components, lowering production costs. Standard hardware like M2 self-tapping screws, 3mm dowel pins, and mini ball bearings are used, adding to its practicality.

This minimalistic design doesn’t compromise performance, as Q8bot demonstrates a range of agile movements. The combination of simplicity, cost-effectiveness, and advanced functionality reflects a well-rounded approach to robotics and engineering, making Q8bot a standout example of innovative design in the field.

The idea for a PCB-centered robot came from Robotis’s Dynamixel XL-330 motor. Each motor has a magnetic encoder and a Cortex-M0 microcontroller for position control, with connectors that fit seamlessly into standard headers on the central PCB. To reduce complexity, the designer removed the motor’s bottom housing and directly mounted it to the frame.

To test the motor’s capabilities, a rig with a linear rail was built, allowing for the optimization of the robot’s leg geometry for jumping. The first robot prototype focused solely on mechanical design.

According to Yufeng, the initial PCB included only motor connectors and an input connector for a pre-made motor controller, creating a tethered robot for initial tests. During this phase, basic software for the robot was developed, including movement algorithms and control via a versatile keyboard script.

As the design advanced, standalone electronics and wireless control were added using the Seeed Studio XIAO ESP32C3 module. To power the robot, two AA-sized lithium-ion batteries were mounted with spring contacts to the chassis, eliminating additional wiring.

All PCBs were designed in Altium, ordered from JLCPCB, and assembled using professional techniques for a refined finish. This streamlined approach highlights innovation in robotic design and efficiency.

The Rev 2 update of the quadruped aims to finalize the robot design with key improvements. The changes focus on refining the jumping sequence through software adjustments and joint PID tuning, enabling two-way communication with a laptop using ESPNow.

The PCB now includes a battery fuel gauge IC and a power-saving switch. Improvements to the mechanical structure simplify assembly while modeling optimizes leg geometry. Yufeng says the goal is to reduce weight and modify all 3D-printed parts for injection molding.

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Jijo Malayil Jijo is an automotive and business journalist based in India. Armed with a BA in History (Honors) from St. Stephen's College, Delhi University, and a PG diploma in Journalism from the Indian Institute of Mass Communication, Delhi, he has worked for news agencies, national newspapers, and automotive magazines. In his spare time, he likes to go off-roading, engage in political discourse, travel, and teach languages.

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