In a recent project, the University of Waterloo used MapleSim to develop new model-based controllers for a musculoskeletal model of the human arm for an upper limb rehabilitation robot. This ultimately will help improve the rehabilitation process for post-stroke patients.

Waterloo, Canada August 13, 2015

Movement disorders in the upper extremities, which are common among post-stroke patients, demand effective rehabilitation procedures. Rehabilitation robots are now being used clinically, but because of emerging proposals for motor learning there is still much that can be done to improve the designs and control algorithms of these robots. For example, one of the neglected aspects in the design and development of rehabilitation devices is the modeling of human interaction with the robot.

An emerging area of research is the use of musculoskeletal models to study human movement, making them an appropriate tool to interact with rehabilitation devices in simulations. In this project, researchers at the University of Waterloo, Borna Ghannadi and Dr. John McPhee[used MapleSim from Maplesoft to develop a musculoskeletal model of the human arm that provides the human action for an upper limb rehabilitation robot, in order to develop new model-based controllers for it. The controlled robot is tested in partnership with the Toronto Rehabilitation Institute (TRI) and Quanser Inc.

The TRI/Quanser robot is an end-effector based planar robot, which performs reaching movements in the horizontal plane for therapy of the shoulder and elbow. The team decided that a fitting starting point was to develop a simplified planar 2D musculoskeletal arm model which consists of two hinged links and six muscles, and assumes no tendon compliance.

After evaluating tools from multiple vendors, the team selected MapleSim for their model development work. Describing their choice, Dr. McPhee says "Taking into account simulation times and quality of results, MapleSim, because of its symbolic computation technology together with optimized code generation, performed better than the other software platforms. Therefore, we selected MapleSim for use throughout this project."

The team then developed an impedance controller which can automatically adjust itself in a variable admittance environment, representing the variable levels of movement disorders affecting rehab patients. The controller was simulated running on the 2D model, in 4 different modes. The first two modes, simulating a healthy arm, were used to calibrate and tune the controller, while the second two modes which simulated a post-stroke patients arm, were used to evaluate its performance.

Hand position error and muscle activation levels were measured and compared during simulation runs in the different operating modes. The results were positive, and in line with expectations, demonstrating that it is possible to use musculoskeletal arm models to evaluate the planar robot.

During the next phase of the project, the team will develop an advanced 3D musculoskeletal arm model with integrated muscle wrapping. As musculoskeletal models become more detailed and life-like, engineers are able to enhance the design of control algorithms for upper limb rehabilitation robots, which ultimately improves the rehabilitation process for post-stroke patients.

Additional resources demonstrating how MapleSim and Maple are used in robotics and mechatronics applications are available here.

About Maplesoft
Maplesoft, a subsidiary of Cybernet Systems Co., Ltd. in Japan, has over 25 years of experience developing products for technical education and research, offering a solution that applies to every aspect of academic life. Its product suite reflects the philosophy that given great tools, people can do great things.

Maplesofts core technology is the worlds most advanced symbolic computation engine, which is the foundation for all of its products, including Maple, the technical computing and documentation environment; MapleSim, the high-performance, multi-domain modeling and simulation tool for physical systems; and Maple T.A., a web-based system for creating and assessing online tests and assignments.

Maplesoft also introduced a fundamental shift in technical education through its Clickable Math and Clickable Engineering initiatives. The idea behind this shift is to create technology that will allow students and teachers to focus on the concepts, not the tool. These initiatives deliver powerful mathematics through visual, interactive point-and-click methods in Maple, while the intuitive physical modeling environment of MapleSim helps teachers to quickly demonstrate the connection between modeling concepts and the underlying mathematical theory.

Over 90% of advanced research institutions and universities worldwide, including MIT, Stanford, Oxford, the NASA Jet Propulsion Laboratory, and the U.S. Department of Energy, have adopted Maplesoft solutions to enhance their education and research activities. In industry Maplesofts customers include Ford, Toyota, NASA, Canadian Space Agency, Motorola, and DreamWorks, covering sectors such as automotive, aerospace, electronics, defense, consumer products, and entertainment.

Visit http://www.maplesoft.com to learn more.