###### Abstract  
We introduce a new mechanism and control system for wireless assistive finger training. The proposed mechanism and control system can provide natural finger flexion and extension via magnetic force and torque between a driving coil and a multi-link magnetic assist device placed on the fingers. The proposed mechanism is designed to allow normal movement while maintaining a natural finger shape, even when multiple magnets are applied to the fingers. Anatomical features were considered in the design to accommodate the angular changes between the fingers during hand extension and flexion. The magnetic force between the control system and the device on the hand allows extension and flexion of the fingers without the use of wires and electrical motors. The performance of the driving system and the magnetic device were verified through various simulations and experiments. A control program with motion tracking is also developed using LabView software. Hence, a wireless assistive finger training system is successfully realized.  
multi-link magnetic assist device; electromagnetic manipulation system; wireless finger training; magnetic force and torque +
Footnote †: journal: Applied  
an EMG sensor and generate an external force at the same time has been developed [25; 26]. However, poor usability still remains a problem to be solved.  
To solve these problems, we propose a new method and mechanism for wireless active finger training or rehabilitation, which uses magnetic forces and is based on wireless operation. In our previous study, we realized a wireless driving method involving magnets applied to the fingers [27]. However, because of magnetic interaction force between the magnets on the fingers, the four fingers (excluding the thumb) could not be trained simultaneously [28]. Thus, in this study, we present a new magnetic device for installation on the fingers. The developed device has various advantages, e.g., a simple structure and configuration (minimized mechanical element), high DOF, and good wearability. In particular, the proposed mechanism and configuration allow both active and passive actuations. The developed system consists of a multi-link magnetic assist device for finger flexion and extension, assistive magnet array in the driving coil and on the palm, and a coil-based control system (bipolar controller, DC power supply, cooling system, and 3-DOF armrest). For motion control, we employ a newly developed vision-based motion tracking system using LabView software (Austin, TX, USA).  
The developed multi-link magnetic assist device is comprised of permanent magnets, bearings, and links, and must prevent strong attractive or repulsive force between the permanent magnets to achieve extension and flexion movements. Assistive magnet arrays in the coil and on the palm enhance extension and flexion, respectively. A vision-based motion tracking program is developed, and motion analysis is performed to verify assistive finger movement achieved via the magnetic force. Hence, the proposed method and system are verified. Section 2 mainly deals with the mechanism and operation principle of the proposed device, the control method, and the analysis of the drive system. In Section 3, the proposed method was verified by analyzing the relationship between the hand trajectory according to the change in current and the change in force and hand angle. In Section 4, the main characteristics are reviewed, and future research plans are discussed.