CENTRA is an active stability module for manual wheelchairs. It mounts between the wheelchair frame and a side-mounted power-assist wheel using two tool-free adapters, and installs in about five minutes without modifying the chair. The adapters fit frame tubes from 19 to 25 mm, covering most manual wheelchair models. An IMU, load cell and rotary encoder track the chair's pitch and roll. When terrain moves the centre of gravity toward the edge of the support base, a motor-driven crank repositions each drive wheel relative to the frame, changing the wheelbase so the seat stays close to level. Left and right cranks are driven independently, so the module responds to cross-slopes as well as inclines and obstacles. Correction runs without user input, and manual override remains available at all times. The same sensors record vibration, shock and gradient along the route travelled, which the companion application uses to map surface hazards.