The Bodie Wheelchair

WINTER 2019 MAE 156B SPONSORED PROJECT

UNIVERSITY OF CALIFORNIA, SAN DIEGO

Sponsored by Dr. Dave Yu

Overview:

Bodie is a paraplegic English bulldog who lost hind-leg mobility due to spinal disease in 2015. Current dog wheelchairs on the market enable walking, but don’t afford sitting or laying down. Bodie’s Wheelchair reimagines the product for everyday extended use: one that enables activity and exercise, and downtime and pet relief, in order to restore independence and quality of life for paraplegic pets and their caring owners. 

The Bodie Wheelchair (Winter 2019).

Background:

Common causes of dog paraplegia are hip dysplasia, intervertebral disc disease, and spinal injuries which can all cause irreparable paralysis and/or immobility of the dog’s hind legs. Dr. Dave Yu is the pet owner of paraplegic English bulldog Bodie, who suffered spinal injuries several years ago. Bodie has lost complete control of his lower body, but still has sensation and will react to pinches or tickles on his hind legs. Despite his disability, Bodie loves swimming and being active.

Current solutions for caring pet owners who seek to improve the quality of life of their dogs are rear-support dog wheelchairs, which offer back-end support and mobility to enable happy, active lives. Dr. Yu has two wheelchairs for assisting Bodie: an industry wheelchair (Eddie’s Wheels) and a previous 156B model wheelchair. The industry wheelchair is robust, fits well, but does not enable Bodie to sit without being removed from the cart. The previous wheelchair folds upon itself to allow Bodie to sit and lay down, but observation of Bodie’s behavior shows discomfort from the frame’s weight distribution on his shoulder. Dr. Yu reimagines an assist device that improves upon the previous design by developing a more comfortable, supportive, sitting wheelchair solution for Bodie's everyday extended use.

Bodie Poot loves swimming! 

Bodie is unable to lay down in industry wheelchair (Eddie's Wheels).                                        Bodie moving from sitting to standing in previous MAE156B wheelchair. 

Final Design

The final design of Bodie's Wheelchair features four wheel stabilization to alleviate poor weight distribution on his body, a linear actuated assist to lower and lift the pet’s paralyzed rear, an integrated retractable harness for free motion in the front, and switch activation for easy operation. Altogether this promoted a full range of activity by making standing, sitting, and laying down positions all possible.

First prototype of final wheelchair design featuring 4-wheel mobility design with linear actuated sit-stand system.

Four Wheels

Four-wheel design improves comfort and stability, while preserving the range of mobility and steering from the two-wheel design.

Four wheels feature two front swivel wheels and two fixed back wheels.

Testing mobility with two added front wheels. Successfully moved over grass and small curbs.

Adding two front wheels redistributed the frame load off the dog’s body. The 360 degree swivel wheels respond immediately to sudden changes in direction; angled struts provide greater stability for uneven surfaces.

Hinging Inner Frame with Brake Lock

An isolated inner frame hinges to lower the rear saddle. A brake lock system is integrated to lock and unlock the retractable front harness when needed. Altogether this enables rear and front to move up and down independently to allow all standing, sitting, and laying down positions.

All three body positions required for wheelchair motion: standing, sitting, laying down.

The sit-stand need was isolated from the mobility need because of their primary physical functional requirements. Sit-stand must allow vertical motion; mobility must allow locomotion. Thus the outer frame is structured to allow mounting of wheel struts while the inner frame hinges to allow the sit-stand motion.

Initial concept testing of actuated motion.

Inner frame hinging motion is linear actuated.

The brake lock was integrated into the hinging inner frame. The frame enables lowering/lifting of the rear; the brake lock enables lowering/lifting of the front. The systems are made co-dependent by sharing the same angle of rotation--when the rear is up the front is fixed, and when the rear is down the front is free.

Inspired by and created with a modified dog walking leash!

Retractable front harness can be fixed for standing/walking, or released for sitting or laying down.

Side view showing shared angle or rotation of the hinging frame and brake lock.

Final Brake Lock with casing, mounted.

Switch-Activated Linear Actuators

Linear actuators providing external force to control the lower and lifting motion of the hinging inner frame.

Up position (left) elevates rear for standing. Down position (right) lowers rear for sitting or laying down.

They are operated by a single DPDT switch. The mount design leveraged the shorter actuator stroke to achieve a greater vertical displacement in the rear. Thus, lighter and smaller actuators could be used to drive the controlled motion. The switch was designed for easy operation for the pet. 

Tests and Performance Results (Prototype of Final Design)

Trial 1 - Linear Actuator Load Testing

• 15 seconds for full cycle of down and up motion.

• Sufficient force supplied to lift without indication of motor stalling.

Sit to Lie Down Test

• Front harness is retractable and allows front to move freely.

Trial 2 - Linear Actuator Load Testing

Bodie Coming Through!