Technology
Repulsive Magnetic Actuator(RMA)
"RMA(Repulsive Magnetic Actuator) utilizes the magnetic field generated between two magnets of the same polarity facing each other, as well as the Lorentz force produced by the current flowing through the coil-wound magnet."
RMA installation structure and vibration
The lower magnet wound with a coil is attached to the lower frame or PCB of the device, while the upper magnet is attached to the upper frame or diaphragm with a fixed gap maintained between them. The two magnets are arranged so that the same poles face each other, creating a repulsive force that keeps them stably attached to the structure. The upper and lower structures are coupled in a suspended state, and when voltage is applied to the lower coil, electromagnetic force generates vibration that pushes or pulls the upper structure.
Input sensing
A magnetic field is formed between the two magnets of the RMA, and when the distance between them changes due to external input, an electromotive force is generated in the coil by electromagnetic induction.
Changes in the distance between the two magnets, whether caused by a person’s hand or by any material such as plastic or metal, generate an induced voltage signal, which can be used as sensing data.
Touch sensors or pressure sensors used as haptic triggers in electronic devices and various other equipment can be replaced with the RMA sensor.
Vibration for haptic and sound implementation
RMA is an actuator in which two magnets are arranged so that the same poles, such as N-N or S-S, face each other. A repulsive force acts between the two magnets with like poles facing one another. Of these two magnets, the input magnet wound with a coil is firmly fixed to a stationary substrate, while the output magnet without a coil is attached with a high-heat-resistant adhesive to a substrate capable of reproducing haptics and sound.
During operation, when voltage is applied to the coil of the fixed lower magnet, current flows through it. This current modulates the repulsive force acting between the upper and lower magnets by strengthening or weakening it, thereby enabling precise control of the magnitude of both attraction and repulsion.
As a result, by varying the magnitude and duration of the input voltage in different ways, it is possible to simultaneously achieve the sophisticated haptic feedback and audio output intended by the designer.