PhoneBot humanoid runs on a $50 Android phone and $400 of parts

Researchers at the University of California, Los Angeles have unveiled PhoneBot, an open-source humanoid robot that relies on an ordinary Android smartphone for vision, sensing and walking control. The robotic hardware costs approximately $400, excluding the phone, according to techradar.com.

PhoneBot stands 483 mm tall and weighs 1.8 kg, with 13 servo motors driving its legs and a rotating torso. Each leg has six actuated joints covering hips, knees and ankles, and a single joint rotates the torso and the mounted phone. The handset's camera handles person tracking, while its inertial measurement unit supplies the motion data used for balance and walking. A separate onboard computer receives wireless commands from the phone over Wi-Fi and converts them into joint movements.

The team tested four Android handsets, including a 2017 Honor 9 and three phones costing about $50 to $80. Locomotion policies run through TensorFlow Lite, and the phone camera supports person detection and pose estimation.

Training also addressed symmetry problems common in low-cost builds. Mirrored training samples cut joint-angle symmetry error from 0.254 to 0.003 radians across five training runs, left-right torque imbalance fell from 0.205 to 0.034 and mechanical-power imbalance dropped from 0.339 to 0.040.

In demonstrations the robot walked, recovered from a face-down position and aimed its phone camera at people without turning its feet. The researchers note several limits: low-powered servos, a controller trained only on flat ground and no arms for object manipulation. The work is currently published on arXiv.