Hippotherapy (or equine-assisted therapy) was designed and is used by therapists (physical, occupational, recreational and speech) to help those afflicted with neuromuscular disorders, motor functions, walking abilities and speech impediments by riding horses. The movement of the horse affects the rider’s posture, coordination, balance and sensorimotor systems and is thought to help improve the impediments of the riders. By no means are they racing or riding on their own, but rather the horse is controlled by a professional handler.
While there are ranches found all over the U.S. who cater to patients, often times patients are unable to visit those locations for various reasons. To help with that issue, mechanical engineering students from Rice University have designed a six-legged robotic horse (known as Stewie) that can come to them. The robotic horse’s design is based on a robotic concept from the 50’s known as the Stewart platform — a type of parallel robot outfitted with six prismatic actuators to control movement with six-DOF.
The robotic platform is nearly identical to those you would find on the flight simulators pilots use to train to fly aircraft. Like those simulators, Stewie’s precision motors are controlled through a computer that lets the students fine-tune its movements, matching those of real horses. It should probably be said at this point that the robotic horse simulates motion, not actual movement, meaning you can’t ride it to different locations.
To mimic a horse’s movement, the student’s initial plan was to build a complicated accelerometer to simulate the animal’s stride.
“When we started, we were rigging this whole complicated accelerometer thing. Then a professor came by and said, ‘Hey, you have an accelerometer on your phone, right?’” — Kelsi Wicker, senior mechanical engineering student
In the end, the students acquired the motion by using a $1 app and taped a smartphone to the back of a horse’s saddle and then walked the animal around to get their measurements. This was done multiple times using different horses and took that data and injected it into their code that controls the robot. Utilizing the data collected from, different horses will enable therapists to choose the best motion simulation and session length for their patients.
Stewie can support patients that weigh up to 250-pounds, although it’s rated to handle 500, but the students want to make sure it doesn’t break down later on through use. Another significant aspect of their design is that all the schematics and code are open source and will be available online for anyone to use to build their own.