# A Prototype Mechatronic Device for Upper Limb Rehabilitation and Analysis of Its Functionality
## 1 Introduction  
Stroke is among the leading causes of mortality worldwide and simultaneously one of the primary contributors to long-term disability, ranking second or third depending on the data source [1]. It is estimated that one in four individuals will experience a stroke during their lifetime [2]. In Europe, over 2.5 million new stroke cases are recorded annually. More than 400,000 people live with permanent consequences, and over 33 million stroke survivors require rehabilitation [3, 4]. In highly developed countries, between 31% and 50% of stroke survivors do not regain independence due to extensive brain tissue damage [5, 6]. This high proportion is also linked to the lack of adequate diagnostic and rehabilitativemethods [7]. Furthermore, 17% to 25% of stroke survivors require continuous care from third parties [8; 9; 10; 11; 12; 13].  
The scale of this issue, coupled with increasing demand for innovative mechatronic solutions in stroke rehabilitation, is well-documented. Projections suggest that in the next 20 to 30 years, the number of people affected by stroke will double. The majority will require medical treatment or rehabilitation for impairments such as speech disorders, memory deficits, or mobility limitations [3; 14; 15; 16; 17].  
Although stroke is traditionally associated with older adults over the age of 65, its incidence is increasingly observed in younger populations [7]. The World Health Organization (WHO) defines stroke as a sudden focal neurological dysfunction lasting more than 24 h, excluding causes unrelated to cerebral circulation [18]. Stroke, traumatic brain injury, and other neurological conditions are the most common causes of upper limb motor dysfunction. Common symptoms of stroke include [3; 17; 19; 20]  
* Paresis or complete paralysis;
* Altered muscle tone (either increased or decreased);
* Speech disorders or loss of speech;
* Orofacial paralysis (e.g., swallowing and feeding difficulties);
* Psychological issues such as emotional instability, depression, and personality changes;
* Spasticity (exaggerated stretch reflex response).  
As a result of these impairments, abnormal postural patterns and atypical movement mechanics frequently develop [21]. Pronounced temporal and spatial asymmetries between limbs are observed in approximately 48% to 82% and 44% to 62% of post-stroke individuals, respectively [22; 23; 24]. [PERSON] et al. [25] suggest that spatial body perception disturbances partly account for these postural asymmetries.  
Rehabilitation following stroke primarily focuses on motor recovery techniques [26], enabling multidirectional stimulation and function-oriented improvement. Motor rehabilitation is defined as a process engaging stroke survivors in activities aimed at improving motor functions, capabilities, and daily performance [27]. Rehabilitative exercises play a critical role in this recovery process [28; 29; 30; 31]. However, the shortage of therapists and caregivers supporting individuals with physical disabilities is expected to worsen in the coming years, posing a significant challenge [16; 17; 32]. Robotic devices have demonstrated potential in addressing this gap, as noted in recent studies [33], though their availability in both clinical and home environments remains limited--highlighting the need for further development.