Rehabilitation Robotics Newsletter

Project Showcase

Spring/Summer 1997

MULOS: Motorized Upper Limb Orthotic System

The MULOS project, funded by the EU Telematics Programme, involves the development of a 5-degree-of-freedom powered orthosis for the upper limb. The basic configuration allows the powered movement of the joints of the shoulder (3 degrees of freedom), the elbow, and forearm. The applications of this system are threefold:

  1. It can be used as an assistive device to provide upper limb motion for people with severe weakness of the upper limbs caused, for instance, by muscular dystrophy or high-level spinal cord injury;
  2. It can be used to provide Continuous Passive Motion therapy to selected joints of the arm. The modular approach to design makes it possible to separate the shoulder, elbow, and wrist units;
  3. It will be possible to use the system to provide graded resistance in order to allow exercise therapy for people with muscle weakness. It is not intended as an exercise system for the fit adult.

diagram of MULOS

What are the major design features?

The orthosis consists of three modules-shoulder, elbow and forearm. The shoulder is a 3-degree-of-freedom mechanism having intersecting axes to allow it to behave as a spherical joint with a center approximately coincident with that of the user's shoulder. We have shown, in experimental studies that, provided there is sufficient compliance, this mechanism will allow a full range of motion at the shoulder. In addition, the shoulder joint mechanism has been oriented in such a way as to minimize the problems of singularities. Power to these three joints is applied by cable drives in such a way as to keep the electric motors as near to the first joint as possible. This keeps the required torques to a minimum. The elbow joint mechanism is a self-contained unit having its own gearbox and electric motor as is the pronation/supination mechanism. Control hardware is mounted at the back of the wheelchair.

At the current stage of development, work has concentrated on the Assistive mode version, and three wheelchair-mounted prototypes are under construction.

How is it controlled?

Clearly, this is one of the key issues in rehabilitation robotics. It has been decided that, depending on the mode of operation, the orthosis should be controlled by one of the following modes:

  1. Point-to-point control with the hand remaining in a vertical position to allow grasping of an object (e.g. glass) using a specially designed 4-degree-of-freedom joystick;
  2. Joint-by-joint control;
  3. Walk-through programming in which trajectories can be pre-programmed by an attendant moving the orthosis through a particular trajectory on a passive mode.

The project has not been concerned with the design of control interfaces except for the development of the 4-degree-of-freedom joystick. We have shown in experimental studies that many people with severe disabilities have the ability to use such an input device. However, the modes of control described above should, in the long term, be suitable for control from a number of interfaces. Such work is outside the scope of the current research program.

What is the current stage of development?

A working demonstration prototype has now been completed and two further prototypes are at an advanced stage of construction. Over the next three months, extensive safety testing will be carried out, followed by initial user studies.

Who are the members of the project team?

The work is being performed by a European Consortium under the EU TIDE Programme. The lead partner is the Centre for Rehabilitation and Engineering Studies (CREST), University of Newcastle upon Tyne, UK. The other members are: 1) University of Abertay, Dundee, UK, 2) TVI Europe Ltd., Dundee, UK, 3) SM Scienzia Machinale, Pisa, Italy, and 4) Free University of Berlin, Germany.

Written by Garth Johnson, Centre for Rehabilitation and Engineering Studies, University of Newcastle upon Tyne

For more information, contact: Professor Garth R. Johnson, CREST, Stephenson Building, University of Newcastle upon Tyne, Newcastle upon Tyne NE1 7RU email:, tel: +44 191-222-6196 fax: +44 191-222-8600, URL:

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Last updated: November 1997
Copyright © Applied Science and Engineering Laboratories, 1997.