Technology
Prosthesis is an art project but its medium is engineering, and engineering is enabled by technology. Nothing like Prosthesis has ever been built before and in order to safely achieve the extrememly demanding performance criteria set out for the project, it must be engineered using state of the art methods and materials. The following is a brief overview of some of the technology that will be employed in order to successfully execute the project. For a brief overview of its specifications, you can download the tech brief.
Control System
At the heart of Prosthesis is the control system. It is what connects the pilot to the machine and it is entirely mechanical. It uses no electronics, no gyros, and has no autonomy. The machine is completely passive and immobile without the human operator. In order to pilot the machine the operator sits on a saddle in the centre of the body and their upper body is secured with a five-point harness. Surrounding them is an exo-skeletal interface which attaches to thier arms and legs and translates the movements of thier limbs to the four legs of the machine. Each leg has two degrees of freedom: planar knee motion and planar hip motion. That means that the legs only move in a forward/backward motion, with no sideways movement possible.
The exo-frame relays positional and force feedback to the operator. This means that the position of the pilots limbs will be directly linked to the position of the machines legs. The pilot will also know the forces on the machines joints because the exo-frame will become harder to move if there is more load on the joints. The harder the pilot pushes, the harder Prosthesis pushes. Since the pilot will not be able to clearly see the limbs except when they are in front of the machine, they will literally have to operate the machine by feel.
The positional feedback system uses hydraulic cylenders mounted on the legs that are linked to similar cylenders on the control frame. These cylenders relay not only powered hydraulic movement to the user, but also suspension movement, so the user knows exacly how hard each foot hits the ground. Input porportionality is achieved by a set of balanced biasing springs on the valve that make it necessary to push significantly harder in order to open the valve. The harder the pilot pushes, the harder Prosthesis pushes. Force feedback is achieved in the hip joints by using the differential pressure in the powered hip actuator to off-set the biasing springs. This makes is harder to activate the hydraulics in the direction opposing the force and easier in the direction that the force is pushing.
Suspension
Prosthesis has a real-time user controlled suspension system. The suspension system includes both active and passive components and can actually be considered an extension of the control system. Not only does the massive, fourty-plus centimeters of suspension movement get transmitted to the user through the control-frame, but the user also has real-time control over the response of the suspension system
Each leg will be outfitted with a custom engineered, coil-over damper, with stroke dependant adjustble impact and rebound damping. These will be tunable in the lab, along with spring rate preload, to optimize control and energy return efficiency over various gates and user abilities. But the most innovative component will be the real-time, pilot controled air spiring which will be in parallel with the passive coil-over damper. The pilot will have 4 triggers at their finger tips. Each trigger will control a valve an air spring that will affect the working volume of the unit and change the suspension reponse of that leg. Depending on when the trigger is pulled in the stride, the leg will store and return impact energy differently and the pilot will be able to tune every step of every leg to optimze walking efficiency on-the-fly. As pilots become more skilled and agressive, they can stiffent the suspension at will. This will be the pinnacle of mastery.
Hydraulics
Moving the 250kg legs and keeping the machine level will be the job of eight, high pressure, high linear velocity hydraulic cylenders. Each leg will have a knee cylender and a hip cylender that will be controled by the movements of the user. The 150kw (200hp) system will use super high efficiency DC brushless motors to operate pumps at a max working pressure of 140kPa (3000psi). Light weight aluminum radiators will endurue the working fluid does not overheat under the intense operating conditions.
Leg and Foot Architecture
The Leg architecture is based on a simple, planar, two degree of freedom knee and hip configuration with back bending knees. The foot is extended, like the rear legs of most fast running quadraped mammals and the ankle is stabilized and controled by a secondary link, making the lower portion of the leg a symetrical 4-bar linkage. What looks like the “foot” is actually the toe. I will be attached using heavy-duty universal joints with a passive self centering sytem. This joint will be self centering allow only supination/pronation (rolling your ankle) and extension/flexion (pointing your toe) and a small amount of rotation of the whole foot to facilitate turning the machine.
Each toe will be mounted on a super-high load sphearical plane bearing (ball joint) allowing the three toes to conform to uneven surfaces. The toe pads will have high durometer polyurethane cast in place to absorb sharp impact and ensure proper contact with the ground. The toe pads will be wrapped with recycled tire fragments, allowing the tread to be changed for different operating conditions.
Powertrain
Coming soon…
HUD Interface
Coming soon…
High Performance Components
Coming soon…
