A Robot Car That Even a Child Can Operate

Why don’t toddlers drive cars? You may think it is because they lack the dexterity and mental capabilities. But if you ask Robotcus, the answer is much more pragmatic: they can’t reach the pedals. In theory, a small child could drive a car if they weren’t limited by their small stature. To solve that problem, Robotcus decided to create a voice-controlled driving system. But his budget was too limited for a full-size vehicle, so he started on a small scale by building this voice-controlled robot car.

On a mechanical level, this is a pretty simple rover robot similar to an RC car. It borrows many of its parts from Robotcus’s previous Mini Flipper Battlebot project. It has six wheels and the original implementation had each of the four back wheels driven by an electric motor, with the front two wheels spinning freely. Later, Robotcus found that his battery couldn’t supply enough current to drive four motors and so he switched to only two driven wheels. Robotcus also retained the battlebot’s servo-actuated flipper mechanism in the front. We suppose that will let children practice their road rage.

The control method is where this gets interesting. A Raspberry Pi Zero 2 W single-board computer (later replaced by a Raspberry Pi 4 Model B) controls the electric motors through a dual H-bridge driver, so this has differential steering. It decides what to do based on voice commands received through a wireless USB microphone. Robotcus experimented with an onboard USB microphone, but found that it wasn’t able to register voice commands reliably.

The Raspberry Pi is able to recognize voice commands using Google’s cloud speech recognition service. It was necessary to go to the cloud because a lighter, local speech recognition library took too long (15+ seconds) to return a result. Even with the time spent sending data back and forth to the cloud, Google’s service was able to do the same thing in just a few seconds. A Python script looks for the recognized command and then controls the motors accordingly.

It can drive forward until told otherwise, stop, lift the flipper, spin left, spin right, drive slowly, and even dance. We aren’t sure if this would help a toddler navigate city streets or not, but they could certainly control a car using this method. Next, Robotcus plans to build a version that accomplishes the same thing with sign language commands.