Abstract—To provide passive rehabilitation therapy to individuals with deficits in upper-limb function, we have developed a powered exoskeleton robot, named the MARSE-4. The developed exoskeleton is supposed to be worn on the lateral side of the upper limb and will provide passive arm movement assistance at the level of elbow, forearm and wrist joints. The kinematic model of the exoskeleton was developed based on modified Denavit-Hartenberg notations. In experiments, PID controllers were employed where trajectory tracking that corresponds to typical rehabilitation (passive) exercises were carried out to evaluate the performances of the developed exoskeleton and the controller. Experimental results show that the MARSE-4 can efficiently deliver passive therapy for elbow, forearm and wrist joint movements. I. INTRODUCTION N recent years research on assistive technologies [1-6] has drawn significant attraction among the researchers aiming to serve elderly or physically disabled individuals in their daily life. Development of powered exoskeleton robots [7-9] as a rehabilitative or assistive device is one of the notable outcomes of such assistive technologies. Arm impairments are very common in the elderly, adults and in the children due to conditions such as strokes, spinal cord injuries, cardiovascular diseases, trauma, sports injuries, and occupational injuries [10-14]. Rehabilitation programs are the main method to promote functional recovery in these subjects [15], which requires a long time care from a qualified therapist. Unfortunately, the number of such disabled individuals is increasing at an alarming rate; for instance, according to World Health Organization, stroke and cardiovascular diseases affect each year more than 15 million people worldwide [14], among these, 85% of stroke survivors will incur acute arm impairment, and 40% will be chronically impaired [16]. Robot-assisted therapy therefore could be a potential solution to help deal with this problem. Manuscript received July 21, 2011. M.H. Rahman is (Ph.D candidate) with the Electrical Engineering Department, École de Technologie Superieure, Canada, e-mail: mohammad-habibur.rahman.1@ens.etsmtl.ca. T.K Ouimet, is (Master`s student) with the Electrical Engineering Department, École de Technologie Superieure, Canada, e-mail: thierry.kittel-ouimet.1@ens.etsmtl.ca. M. Saad is with the Electrical Engineering Department, École de Technologie Superieure, Canada, e-mail: maarouf.saad@etsmtl.ca. J.P. Kenné is with the Mechanical Engineering Department, École de Technologie Superieure, Canada, e-mail: jean-pierre.kenne@etsmtl.ca. P.S. Archambault is with the School of Physical & Occupational Therapy, McGill University, Canada, e-mail: philippe.archambault@mcgill.ca. Recent studies also revealed that robot-aided therapy and virtual reality-based rehabilitation can significantly reduce arm impairments [1, 17-20]. We therefore have developed a 4DoFs powered exoskeleton robot to rehabilitee elbow, forearm and wrist joint movements. Although much research has been going on to develop such assistive devices, much more is needed in order to reach our goal of restoring body mobility. In our previous research, we have developed a 2DoFs exoskeleton robot for assisting elbow and forearm movements [5]. In a continuing effort later on, we have developed a separate exoskeleton module (2DoFs) for assisting wrist joint movements [6]. In this paper we integrate these two modules in a 4DoFs powered exoskeleton robot, MARSE-4 to assist with human elbow, forearm and wrist joint movement. Note that the developed exoskeleton considers upper-limb biomechanics, and is designed for a typical adult. It is supposed to be worn on the lateral side of the upper-arm and has extended range of movements to provide elbow joint flexion/extension, forearm pronation/supination, radial/ulnar movements and flexion/extension of wrist movements. As a control strategy, we employed a computationally inexpensive PID controller to maneuver the MARSE-4. Note that passive rehabilitation exercises are usually performed at a natural speed of arm movement, or even lower, depending on the patient’s level of arm impairment; therefore, using a PID-based control approach is a reasonable choice for this type of application. Experiments were carried out with healthy human subjects, where typical passive rehabilitation exercises that include single and multi joint movements (at different speeds) were performed by the MARSE-4. The trial results show that the powered exoskeleton robot is efficient in performing these passive therapeutic exercises. In the next section, an overview of the developed MARSE- 4 is presented. Details of its control strategy are described in section III. In section IV, experimental results are presented to evaluate the performance of the MARSE and the controller to provide the passive arm therapy. Finally the paper ends with the conclusion and future works in section V. II. EXOSKELETON ROBOT A. Kinematic Model Modified Denavit-Hartenberg (DH) notations were used to develop the kinematic model of the MARSE-4. The link- frame attachments of the system are depicted in Fig. 1. The joint axes of rotation are indicated by dark black arrow Control of a Powered Exoskeleton for Elbow, Forearm and Wrist Joint Movements Mohammad H. Rahman, Student Member, IEEE, T.K-Ouimet, Maarouf Saad, Senior Member, IEEE, Jean P. Kenné, and Philippe S. Archambault I 978-1-4577-2137-3/11/$26.00 © 2011 IEEE 1561 Proceedings of the 2011 IEEE International Conference on Robotics and Biomimetics December 7-11, 2011, Phuket, Thailand