Adaptive Wheelchairs

Reprinted from PN June 2012

The second generation of the PerMMA wheelchair will tackle steps as well as challenging terrain.

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Has this ever happened to you? You’re all set for an outing, but as you open the door of your house to leave, you notice a huge ice sheet right in front of you, blocking your way. You’re stuck inside.

Or maybe you’re shopping and see exactly the product you want in a store window, but you can’t get into the store because there’s a step in front of the door.

Both dilemmas are scenarios that many of the 3.3 million Americans who use wheelchairs to get around have faced. Researchers at the Human Engineering Research Laboratories (HERL) in Pittsburgh are working to solve problems like these with a new type of wheelchair.

This new type of wheelchair is from researchers at the Human Engineering Research Laboratories in Pittsburgh.

Step Right Up

The second generation of the Personal Mobility and Manipulation Appliance (PerMMA Gen II) wheelchair will tackle steps as well as challenging terrain.

Like the first generation of PerrMMA, the second generation is supported by the Quality of Life (QoLT) Engineering Research Center (ERC), a National Science Foundation-funded collaboration between the University of Pittsburgh and Carnegie Mellon University.

The secret is in the chair’s six wheels. The large center driving wheels can reposition themselves to simulate front-, mid-, or rear-wheel driving. The four smaller caster wheels are controlled with compressed air and can move up and down freely and independently.

When climbing curbs, the front caster wheels lift up onto the curb; then the driving wheels lift themselves up and forward onto the curb, lifting the chair.

This is done automatically, whenever PerMMA Gen II senses a curb or step. Of course, the ultimate goal is for PerMMA Gen II to climb a set of stairs. HERL researchers have given themselves the task of making PerMMA go up four steps.

Inching Along

The same general function is used to operate on icy or slippery surfaces.

A traditional power wheelchair can get stuck on this kind of terrain. PerMMA Gen II, however, uses its front and rear caster wheels to inch forward on the slick surface by extending its front casters, moving the seat forward, bringing the rear casters forward, and then repeating the process.

During climbing or inching maneuvers, wheelchair users must be kept safe no matter how rough or tilted the terrain might be. PerMMA Gen II uses sophisticated sensors to examine the angle of the ground in relation to the driver. Using specialized algorithms, the PerMMA Gen II stabilization system keeps the seat safely upright automatically.

The Next Step


Currently, PerMMA Gen II is undergoing experimental testing to ensure the design and safety controls are fully operational. Following these tests, clinical trials will begin to evaluate the usability of the system.

HERL researchers continue to test and develop the first generation of PerMMA by improving the dual control of the robotic arms and their gripping and handing-off motions.

Ultimately, the two generations of PerMMA will be combined to create PerMMA Generation III: a wheelchair with fully controllable robotic arms that climbs steps and navigates difficult terrain—a truly all-encompassing robotic appliance for mobility and manipulation.

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