Active Vibration Cancellation for Handheld Linear Oscillating Actuator

For medical and cosmetic skin treatment, handheld devices are applied which use an oscillating needle to punctuate the human skin repetitively. A novel approach for actuating the needle is based on an electromagnetic linear actuator excited in resonance, whose slider is suspended to the stator via springs. In contrast to conventional devices, this allows an independent control of the oscillation amplitude, enhancing the usability for the operator. However, the oscillating mass is considerably higher than in current handheld devices, leading to increased axial vibrations. These vibrations not only hinder an accurate operation of the device but can have a fatiguing or in the long-term even harmful effect on the user's hand. To reduce the vibrations, a second, independently actuated mass is integrated inside the actuator's drive system. Thereby, an oscillation mode is established where the housing vibrations are substantially reduced. This contribution presents the layout of the linear actuator with to sliders operated in resonance as well as experimental data exhibiting the huge potential for vibration reduction.