Stair-climbing wheelchair

Overview

I have been developing a driver-assisted stair-climbing platform (for wheelchairs, and potentially other applications) built around a 4WD articulated chassis with a passive yaw joint. The yaw joint allows the chassis to curve around turning stairs while keeping all four soft airless wheels in contact with the steps. On flat ground, the vehicle can drive in a slipless regime within a 1 m turning radius. Tighter turns (up to pure rotation) are also possible with a hybrid skid-steer mode. All modes are unified under a single control interface for seamless driving.

I built this entire project from scratch. This includes mechanical design, fabrication, ROS 2 software architecture, control systems, and computer vision.

Off-the-shelf components include: onboard computer, motors and motor controllers, camera, IMU, encoders, and electrical components.

Subscale platform

I built a subscale (1/4-scale) platform to validate the kinematics and the articulated-chassis concept.

Full-scale platform

Mechanical, electrical and software integration

• kinematics and control systems
• simulation in Gazebo to support development and testing
• user interface
• stair climbing capabilities

Demonstration of the full-scale platform capabilities to climb stairs and maneuver.

Wheelchair integration

• wheelchair mechanism design and optimization
• chair auto-leveling

Demonstration of the wheelchair integration with the platform. The wheelchair is mounted on a self-leveling mechanism that keeps the seat horizontal while climbing or descending stairs.

Advanced Driver-Assistance System (ADAS)

• classical computer vision for stair detection and collision avoidance
• machine learning for general ADAS features and to improve performance of stair navigation
• the machine learning stack uses YOLO26 trained on the ADE20K dataset for semantic segmentation

The platform can detect stairs, and assist with stair climbing and descending (seat leveling auto-engages and vehicle remains square with the leading step) and avoid collisions with obstacles. Work in progress.

Hardware upgrades

I am in the process of doing a number of hardware upgrades:

• Wheels: the original wheels had very uneven radial stiffness, which made for a bumpy ride and poor handling. The new wheels have proven to be a significant upgrade for higher speed driving and general smoothness.
• Seat: the original seat was a quick proof of concept, meant to be replaced, which finally happened! Armrests are on the way.
• Linear actuator: the current solution with the rotary actuator has poor rigidity (largely from the gear train). I will be testing a linear actuator to allow for higher overall chair stiffness and a self-locking mechanism, for safety and power efficiency.
• Onboard controls: I am adding a joystick and a small touch screen for full control by the user.