The upper-limbs involuntary muscles contraction of the neurodegenerative-disordered patients can cause an oscillatory movement of the hand. The nature of the complex joint muscle-tendon system allows the modelling of the tremor oscillatory movement using mass-spring systems. The rest (3-7 Hz) and postural (5-12 Hz) tremors are the most common types of pathological tremor presented in patients suffering from both Parkinson's and essential tremor. Addiction to medication and the drawbacks caused by the non-responding to neurosurgery treatments grow the interest on finding an alternative solution. The design of an attenuator composed of passive vibrating anti-tremor systems operating within the pathological tremor frequency range can thus be a good choice.

Most research papers concentrated on the design and manufacturing of active tremor control devices due to their advantage in producing a counteracting force by adapting the controller's parameters depending on the sensor's feedback information. However, it requires a very large power consumption. The tuned-mass-damper (TMD) is a passive vibration control device widely used to mitigate troublesome resonance and protect the structure from the undesired force transmitted. The attenuation caused by the passive absorber depends on the mass ratio that must allow the TMD to withstand the full excitation muscular force. A passive absorber has fixed characteristics allowing its frequency to be tuned at specified frequencies of the structure. Multiple TMD (MTMD) are used to improve the control efficiency obtained with a Single TMD (STMD) or to reduce the vibration amplitudes of multiple frequencies. However, they increase the number of resonance frequencies of the overall system. Passive vibration absorbers are widely used despite of their shortcomings. Several studies aim to enhance the performance of passive absorbers due to their simple design, low cost, and the lack of external power source. Another important goal is to add optimized MTMD that can reduce the critical amplitudes all over the excitation frequencies bandwidth without causing the addition of resonance frequencies outside the operational bandwidth.

Measured acceleration signals are processed for several Parkinson and essential tremor patients. The acceleration is measured at the hand using tri-axial accelerometer. Electromyography (EMG) is used to obtain information of the extensor carpi Radialis Longus (ECR) and Flexor Carpi Radialis (FCR) active muscles generating the tremor. The tremor frequency range will specify the required bandwidth for the passive MTMD. TMDs are placed on the forearm or palm segments of the modeled upper-limbs. The effect of the TMD position, the number of TMDs, and the total mass ratio of the TMDs on the performance of the MTMD in reducing the involuntary tremor amplitude is studied.