Abstract—This study is about the optimal strategy of restoring hand functions of the quadriplegics by functional electrical stimulation (FES). Nowadays, there are many assistive devices developed for restoring the quadriplegics’ lost functions by FES. If patients can use their residual capabilities to control these devices, it will be very exciting thing for them. However, the input sources or the command controller are usually complicated or inconvenient for them to use. If there is the optimal strategy of controlling built, the quadriplegics will benefit much from it. In this study, we had designed the optimal strategy of the patient-driven command controller for restoring their lost hand functions by FES. The proposed optimal control strategy can also be modified and applied for different rehabilitation applications. Keywords—Optimal Strategy, Command Controller, Hand Function, Quadriplegics, Functional Electrical Stimulation I. INTRODUCTION Quadriplegics, with hand paralysis who were due to spinal cord injuries (SCI) or other neurological impairments, lost their ability to grasp objects for activities of daily life (ADL), such as eating, drinking, writing, brushing teeth, etc. They are unable to perform these activities independently, and it may also increase the loading to their families both economically and mentally. Apparently, it is very desirable and urgent to develop a practical system that can be used by the quadriplegics to restore their hand functions. There are many assistive devices developed for restoring the lost functions of quadriplegics in the recent decade [1-5]. Functional electrical stimulation (FES) and neural prostheses are very popular in clinic applications. Although these systems are highly developed, the input sources or command controller are very complicated and inconvenient for the patients to use. If there is existed an optimal strategy for the input source or command controller, it will be very helpful for them to restore their lost functions. Besides, from the aspects of rehabilitation and psychology, they will benefit more if they could use their residual capabilities to control these assistive devices. In this study, we will have discussions on the optimal strategy of the patient-driven command controller in rehabilitation applications, and we will take the restoration of hand functions by functional electrical stimulation for example. II. METHODOLOGY It is very important to design the optimal strategy for restoring hand functions by FES. In order to find the optimal strategy of different input sources before the paralyzed hand muscles can be actually controlled by a command controller, there are several essential issues need to be dealt with. Firstly, it is necessary to systemically profile the muscle groups that perform hand functions when applying the electrical stimulation for individuals. These parameters include threshold, saturation, spillover, recruitment curves of position and force. Secondly, since each individual will have different stimulating parameters, we need to develop a systematic procedure and related devices to identify them. These parameters could be as a base on the development of stimulating template. Combining with FES, the stimulating template can be tuned to get the best available grasp function. Besides, we also need to synthesize the stimulation template to get the so-called multi-state setting of the hand motion. To analyze the hand motions, there are multi-state settings such as the neural position of the hand, hand opening, grasping, etc. Thirdly, in order to find proper electrical stimulation parameters during different hand motions, there needs the optimal stimulation template. After finding the profiles of targeted muscle groups and the proper electrical stimulation parameters, the motions would be produced by FES more smoothly. On the other hand, the aim of this study is to develop a patient-driven command controller for the quadriplegics, too. With their residual capabilities, they can control the assistive devices better using this optimal strategy. The flowchart of optimal strategy for FES is showed in Fig. 1. To begin with this study, we will have normal people to build the electrical stimulating templates and muscle profiling system. When they have been done well and also have some preliminary results, the quadriplegics, such as the C5/C6 patients, will be involved in the following study. In the next several parts, there are some results and discussions of the optimal strategy design for FES. Optimal Strategy of the Patient-Driven Command Controller for Restoring Hand Functions by Functional Electrical Stimulation Y. H. Chiou 1 , J. J. Luh 2 , S. S. Chen 3 , J. S. Lai 2 , T. S. Kuo 1, 4 1 Department of Electrical Engineering, National Taiwan University, Taiwan, R.O.C. 2 Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital, Taiwan, R.O.C. 3 Department of Physical Medicine and Rehabilitation, Taipei Medical University Hospital, Taiwan, R.O.C. 4 Graduate Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan, R.O.C. 0 1 E