# Developing an Assisting Device to Reduce the Vibration on the Hands of Elders
## 3 Proposed Approach
### Gyroscope-Enabled Framework of Wearable Device to Suppress Vibration  
The concept of this paper was to investigate a novel wearable device to suppress the uniaxial tremor on one hand of [PERSON]'s patients. Based on the fundamental principle of the gyroscope, the analysis of the dynamic model was accomplished. When wearing the proposed design, a human hand with a single degree of freedom at the wrist and a gyroscope-based anti-tremor device mounted on the back of the hand become a rigid body. The system performance was validated to examine the gyroscope's parameters and orientation, which affects tremor suppression.  
From the above modeling and analysis, we were motivated to carry out a feasible and innovative design. Due to the wearable characteristic, the structure must be compact and lightweight to ensure the comfort of the patient, as shown in Figure 7. The direct connection from the flywheel to the motor gives assistance to lessen the total weight of the device. The shape of the flywheel must be symmetrical, and its material should be distributed uniformly. Later, the driving motor type might be brushless DC, since it rapidly rotates around the radial axis. Both the flywheel and motor are linked to the internal frame,  
Figure 6: Illustration of system responses for input torques of (**a**) 2 Hz, (**b**) 4 Hz, and (**c**) 6 Hz.  
which ought to be light and concentric. Moreover, it is noted that the amplitude of the vibration could be enlarged in a low-frequency zone, although it would suppress tremors in higher-frequency regions. Henceforth, to improve the system response, several control methods were considered such as precession state control [37], the extended Jacobian method [38], or approximate control [39]. In this work, we evaluated the proper approach to control the precession axis. Equation (38) could be re-written as  
\[\ddot{\theta}k_{8}+D_{w}\dot{\theta}+K_{w}^{\prime}\theta=T_{w}-K_{g}\dot{\phi} \tag{39}\]  
\[\ddot{\phi}k_{7}+D_{P}\dot{\phi}+K_{p}^{\prime}\phi=T_{P}+K_{g}\dot{\theta} \tag{40}\]  
where:  
\[K_{g}=I_{yf}\Omega\ K_{p}^{\prime}=K_{p}-g\Big{(}m_{m}r_{m}+m_{f}r_{f}\Big{)}\]  
\[K_{w}^{\prime}=K_{w}-m_{f}g\Big{(}r_{f}+y_{P}\Big{)}+m_{w}gy_{w}+m_{m}g(r_{m}+ y_{P})\]  
In [37], the max value of the moment on the precession axis is:  
\[T_{g}=k_{s}K_{g}\dot{\theta}=k_{s}I_{yf}\Omega\dot{\theta}=1.2\times 4.3\times 1 0^{-5}\frac{2500\times 2\pi}{60}\times 1.4=0.019(\mathrm{Nm}) \tag{41}\]  
Remember that the desired velocity \(\dot{\theta}\) that rotates around the precession axis in a range of \(\pm 20^{\circ}\) for 0.5 s, \(k_{s}\) which is 1.4 rad/s, is the safe threshold due to the tolerance of the ball-screw, since the driving motor is attached to the mechanical part. The concept of our proposed device was simulated in three-dimensional space, as shown in Figure 8. As everyone has different hand sizes, the base should be curved and tied to the hand via a fastener.  
Figure 8: The conceptual 3D design of the proposed approach.  
Figure 7: Theoretical design of the wearable device when the flywheel is directly attached to the motor (**a**), the internal frame of the motor–flywheel connection (**b**), and the 3D model showing the external frame and driving mechanism (**c**).