# A Parallel Robot with Torque Monitoring for Brachial Monoparesis Rehabilitation Tasks
## 1 Introduction  
Monoplegia is a type of paralysis that affects one of the limbs (arm or leg), permanently or temporarily [1].When monoplegia is located on one of the upper limbs it is referred to as brachial monoplegia and if it is located on one of the lower limbs it is referred to as crural monoplegia [2].There are several neurological disorders that may cause monoplegia, most common are: stroke, cerebral palsy, Guillain-Barre syndrome, peripheral neuropathy, [PERSON]'s disease, head or spinal trauma, and neuropathy. With respect to the neurological disease that caused the monoplegia, sometimes it can evolve to paraplegia or hemiplegia. A less severe form of monoplegia is called monoparesis and monoparesis of the upper limb is referred as brachial monoparesis. Pure brachial monoparesis is usually caused by stroke [3] and its effects are weakness, spasticity, numbness, paralysis, pain, and headaches. Stroke may occur in any age group, but it is more frequent in ages of 55 tofunctionalities may be regained [5]. Physical therapy of brachial monoparesis implies repetitive motion of the upper limb with motor deficit. With respect to the affected area (shoulder, elbow, wrist, fingers) different rehabilitation motions are used, targeting the specific motion of each articulation, but each motion must be done by special medical personnel. The capability of the NHS (National Health System) to provide medical care for each person in need has been seriously stressed lately. Previous statistics preconized that in 2030 the NHS will be unable to provide medical care for the people in need due to personal shortage [5]; momentarily there is a crisis regarding staff recruiting in the NHS [6] so this prevision seams quite close. All the above data raises a question: Who will provide care for the ones in need in the near future? There is no simple and straight forward answer to this question, but there are research domains trying to overcome the predicted personnel crisis and one of these domains is medical robotics. Developing robotic solutions for the medical care should not imply substituting the medical personnel from the operation/therapy room but providing means for the health careers to deliver a more precise and effective treatment with less effort and allowing them to serve more efficiently a larger number of patients. The effectiveness of the physical therapy when discussing rehabilitation of stroke or other neurological disease survivors is largely dependent on how fast the treatment is delivered to the patient. With the help of robotic devices this treatment may be delivered in the acute phase, immediately after patient stabilization, following a stroke incident. Robotic devices for brachial monoparesis should be able to mold the impaired upper limb and mimic the rehabilitation motion of the targeted anatomical articulation. Several solutions for upper limb rehabilitation have been developed; one can classify these solutions in exoskeletons and end-effectors systems [7]. [PERSON] et al. [8] developed an adaptive 4-DOF exoskeleton for upper limb rehabilitation, mountable on a wheelchair, able to carry the patient throughout daily activities like eating and drinking. The exoskeleton uses an open-chain structure to mimic the anatomy of the upper limb joints and it is divided into three modules: shoulder module, elbow module, and wrist module. The exoskeleton uses a proportional-derivative control method implemented using ROS (Robotic Operating System) and it uses the dynamic model of the mechanism and the weights of the upper limb segments to hold the arm in position during daily tasks. The system has yet to undergo clinical trials and user acceptance. Studies regarding the development of upper limb exoskeletons were also published in [9; 10; 11; 12], some of them being based on the study of the dynamic behavior of the exoskeletons and the possibility to control the robotic solutions to maximize the efficiency of the rehabilitation.