SCCRUB-a-Dub-Dub

It scrubs! It shines! And if engineers at Northeastern University have their way, SCCRUB will be the only brush you'll ever need to make your home sparkle like new! No, SCCRUB is not a gimmicky gadget from a 1990s infomercial. It is a robotic arm that was designed to automate household chores. Household robots, aside from vacuums and mops, have yet to really materialize, so the team decided to focus their attention on a particularly unpleasant task to help move the field forward — scrubbing.

SCCRUB, or Surface Cleaning Compliant Robot Utilizing Bristles, is a soft robotic arm capable of deep-cleaning surfaces by delivering both pressure and torque, which are two of the most important ingredients for removing sticky, greasy, or burnt-on messes. Unlike traditional rigid robots that risk injury or damage in spaces shared with people, SCCRUB combines power with safety, making it ideal for home environments.

The robot features what are called torsionally rigid universal couplings (TRUNC) cells, which allow the arm to bend and flex while still transmitting rotational force. This enables it to press firmly into surfaces, much like a human arm, without sacrificing safety or control. By chaining and nesting these TRUNC cells, the researchers created an arm that is lightweight, compliant, and capable of delivering torque comparable to a hand drill.

To convert that torque into cleaning action, SCCRUB uses a specially designed counter-rotating brush head. The team built a custom planetary gearbox that splits a single motor input into two opposing brush rotations. This clever mechanism drastically reduces the reaction moment (that is, the force that pushes back against the robot when it scrubs) by 85% compared to a standard unidirectional brush. That reduction allows SCCRUB to apply more pressure without compromising stability or control.

To control this flexible arm, the team trained a neural network to learn the robot’s inverse kinematics and elasticity. The controller plans trajectories based on the forces involved, enabling open-loop control of both position and pressure. During testing, SCCRUB demonstrated impressive effectiveness, cleaning 99.7% of contaminants like burnt ketchup on a plate and sticky blueberry preserves from a toilet seat. This is well beyond the 47.1% achieved by wetting and rinsing alone.

With a global cleaning robot market projected to reach $40.8 billion by 2032, the researchers hope their design will help shift robotic cleaning from the floor to the rest of the home. From stubborn stove stains to dirty countertops, SCCRUB might soon be lending a helping hand.