Finger Exoskeleton for Early Acute Post Stroke Rehabilitation: Control Design and Performance Analysis

According to World Health Organization, the number of stroke patients related to upper extremity hemiparesis increases yearly. Due to this, many types of rehabilitation devices have been invented to help these patients, especially to recover their hand functions. These include exoskeleton devices which aims to deliver high intensity therapy for a longer period. Every exoskeleton rehabilitation device is made up of three components; exoskeleton mechanism, actuator and control system. Control system is central to rehabilitation devices. The accurate control algorithm implementation is very crucial for effective rehabilitation. Therefore, the performance and of the control algorithm for any rehabilitation device must be investigated to assess its efficiency. This study aims to investigate the performance of position control based on a new control strategy system of an index finger exoskeleton namely FiCoPRS, by comparing the Heuristic and Ziegler Nicol method based on various controller configurations. The parameter controlled was position of index finger measured through MCP joint angle. PID parameters were tuned using heuristic method and Ziegler Nichols’ closed loop method. In order to assess the performance of the control system, actual data from position control was compared to reference values. This study suggested that the PID controller managed to control the parameter according to the set point better than P, PI and PD controller. The device could be manipulated to move to any position within the range of exoskeleton motion accurately. The results of the study also suggested that the performance of the control system for rehabilitation was very good as the error was less than 10%. The current findings prove that the study is useful and has contributed significant knowledge in understanding better the control system of an index finger exoskeleton.