Stiff-knee gait has been attributed to decreased knee flexion velocity at the initiation of swing phase which may be due in part to inappropriate knee extensor activity and/or impaired hip flexor activity. In response, stroke patients often adopt compensatory strategies including hip circumduction and hip hiking (a combination of hip and pelvic kinematic changes) to ensure toe-clearance. These stereotypical movement patterns involve a relatively tight coupling of motions at the pelvic, hip, and knee across the frontal/sagittal planes of motion. While these kinematic patterns suggest the existence of abnormal muscle synergies, the surprisingly few quantitative studies of these synergies (in terms of joint torque patterns) have yielded conflicting results. Rigid body simulations of the swing phase of gait indicate that inertial interactions between the frontal and sagittal planes are minimal. Therefore, coupling of such movements necessarily requires active generation of torques in both planes. Earlier results from our laboratory showed evidence of abnormal across-joint torque coupling at the hip and knee in a number of swing phase limb configurations in the stroke population. These abnormal torque coupling between the impaired hip and knee are related, at least in part, to the kinematic disturbances post stroke. Our preliminary data suggest that the underlying torque synergies are reflective of abnormal motor commands that potentially originate from the contralateral hemisphere. Given these findings, we argue that primary source of gait dysfunction in many hemiparetic stroke subjects is likely a manifestation of an impaired coordination. Indeed, when the exaggerated muscular activity and weakness at a single joint are treated effectively, or when these impairments resolve spontaneously, gait dysfunction is often still present and severe. Consistent with these observations, our recent investigation indicates that robotic facilitation of knee flexion in individuals with stroke was coupled with a kinematic adaptation constrained largely by the impaired torque couplings observed under isometric conditions at a similar lower limb posture.The knowledge generated by our examination of the underlying neuro-mechanical mechanisms of impaired gait will form a cornerstone for future clinical research and provide a rational scientific basis for the design of contemporary robotic interventions that seek to overcome abnormal across-joint coupling/coordination.

Benjamin Kuipers joined the University of Michigan in January 2009 as Professor of Computer Science and Engineering. Prior to that, he held an endowed Professorship in Computer Sciences at the University of Texas at Austin.  He received his B.A. from Swarthmore College, and his Ph.D. from MIT. He investigates the representation of commonsense and expert knowledge, with particular emphasis on the effective use of incomplete knowledge. His research accomplishments include developing the TOUR model of spatial knowledge in the cognitive map, the QSIM algorithm for qualitative simulation, the Algernon system for knowledge representation, and the Spatial Semantic Hierarchy models of knowledge for robot exploration and mapping.  He has served as Department Chair at UT Austin, and is a Fellow of AAAI, IEEE, and AAAS.

What makes an intelligent robot useful, or even acceptable, as assistive technology? An intelligent robot is an agent. It senses its environment, learns a model of that environment, and uses its knowledge to take actions to achieve its goals. To be able to do this places substantial requirements on the knowledge representation and the perception and learning capabilities of the robot. At the same time, the robot necessarily exercises some degree of autonomy, in order to use its abilities to do anything useful. But a person with disabilities who relies on the robot as assistive technology is likely to be concerned with protecting and extending his or her own sense of autonomy. To be acceptable, an assistive technology must increase, or at least not decrease, the user's sense of autonomy. We consider the case of the intelligent robot wheelchair, that observes its environment and builds a cognitive map, that can help it bring its driver from one place to another. The structure of the knowledge in the cognitive map determines the different ways available to the driver for instructing the wheelchair. This leads us to a conjecture that could shed light on the puzzling lack of acceptance of robotic wheelchairs over the past several decades.

Todd Kuiken, MD, PhD

Todd A. Kuiken received his MD and Ph.D. in biomedical engineering from Northwestern (1990) and his residency in PM&R at the Rehabilitation Institute of Chicago (1995). Dr. Kuiken currently is the Director of the Center for Bionic Medicine. He is a Professor in the Depts. of PM&R, Biomedical Engineering and Surgery of Northwestern University. He is also a practicing physiatrist at the RIC. Dr. Kuiken’s research team is working to develop neural-machine interfaces to improve the function of artificial limbs. A main research focus of the lab is developing a technique to use nerve transfers for improvement of myoelectric prosthesis control. By transferring the residual arm nerves in an upper limb amputee to spare regions of muscle it is possible to make new signals for the control of robotic arms. These signals are be directly related to the original function of the limb and allow simultaneous control of multiple joints in a natural way. This work has now been extended with the use of pattern recognition algorithms, enabling the intuitive control of more functions it the prosthetic limbs. Similarly, hand sensation nerves grow into spare skin so that when this skin is touched, the amputee feels like their missing hand is being touched.


Jessica Presperin Pedersen, MBA, OTR/L, ATP/SMS
Collaboration Between the Clinician and Non-clinical Researcher: Wheelchairs and Robotics What We Need to Know

Jessica Presperin Pedersen has been an OT for 35 years with an expertise in wheelchairs and seating.  She co-developed the first wheelchair clinic in Chicago at the Rehabilitation institute of Chicago and was in the first cohort of people in the United States to become an assistive technology provider. Jessica is a master clinician, educator, and has worked to provide input for product development. She began participating in research in the last ten years, learning from the experts in research as she exchanges her clinical knowledge and skills.

What does the non-clinical research engineer need to know about working with people with disabilities? This session will review people first language, everyday facts about ADLs, transfers, and emergency care that all researchers should know when working with people with disabilities in the research lab.  People with severe impairments can use power wheelchairs with modified alternative controls. Engineers are collaborating with therapists and individuals who use alternative controls to incorporate robotics with a goal of designing a smart wheelchair. Discussion will take place pertaining to ascertain why robotics can be used to increase participation for power wheelchair users.