Upper Limb Mechanics Current Projects
Rehabilitation of Reaching in Chronic Stroke using an Anti-Gravity Force Field
Our specific aims are:
- to characterize deficits in post-stroke reaching as a function of movement direction, external load direction, and limb orientation with respect to gravity;
- to investigate potential mechanisms underlying external load effects on reaching kinematics;
- to demonstrate the efficacy of a MACARM-mediated “anti-gravity” force field to rehabilitate reaching in a group of chronic stroke survivors with moderate or severe impairment.
This research is funded by a Field Initiated Research Grant (H133G060169) from NIDRR.
Phase I SBIR - MACARM: a novel cable robot for upper limb neurorehabilitation in stroke survivors
With funding from the NIH (R43 HD055697-01), Intelligent Automation Inc. and RIC are extending the capabilities of the MACARM. Work is focused on methods to obtain joint-based kinematic data, enhancement of the rehabilitation training environment, and control of forearm orientation as well as end-point location.
About the MACARM
The Multi-Axis Cartesian-based Arm Rehabilitation Machine (MACARM) is a new cable robot for upper limb rehabilitation. The MACARM is founded on the Multipurpose, Multiaxial Isokinetic Dynamometer (MMID) developed by Intelligent Automation, Incorporated (opens new window) (IAI) . The MMID technology was originally developed for NASA as a potential exercise system for astronauts onboard the International Space Station. With funding from NIDRR, the RIC and IAI are adapting and evaluating the device for use in physical rehabilitation.
The prototype MACARM is configured with eight Active Modules anchored at the corners of a 234 cm (92 in) cube constructed of extruded aluminum tubing. Each Active Module consists of a high performance motor, a position encoder, a gearbox, a cable spool and a cable fairlead. The cable from each Active Module attaches to the corner of a custom designed end-effector in the center of the work volume. The Active Modules generate forces that interact with the end-effector through cables, and in this manner, produce forces that interact with the user. User-applied forces are measured directly with a 6 degree of freedom load cell mounted on the end-effector. A thermoplastic snap-on orthosis allows the user to interact with the MACARM without grasping.
The MACARM uses a flexible architecture to represent its behavior during runtime. In the simplest approach, the operator can specify a path (in 3 to 6 degrees of freedom) that the end-effector is to follow through the work volume. The path can be any geometric path (such as a line or an arc) or a trained segment (a path input by moving the end-effector by hand). The MACARM can also be operated in a bounded free-motion mode, in which the end-effector moves according to user-specified rules, subject to virtual boundaries. The MACARM software also makes use of the Open Dynamics Engine (ODE) software library for real-time dynamics simulation. Using this library, the MACARM software can simulate any mechanical environment, with the user interacting with the simulated environment via the end-effector. The virtual environment can contain any number of fixed or moveable objects that act according to user-defined physical “laws”.
The MACARM’s 3-D static accuracy (the accuracy of movement to a specified position) is 2 mm. Dynamic accuracy (the accuracy of movement with a specified path and velocity) is 3 mm, and is insensitive to movement velocity. Peak movement velocity is approximately 70 in/s (1.7 m/s). Maximum force is approximately 300 lb.