Haptic Actuators: Principle of Operation
Haptic Actuators consist of two poles set at a specific and fixed air gap which are mechanically fasted together through a spring and/or housing. One of the pole pieces is trapped inside of a wound coil assembly. This pole piece is the stationary pole piece which will remain static while the actuator is energized.
When the coil assembly is energized, the magnetic field produced is transferred through the stationary pole piece, focused across the air gap and attracts the second, dynamic pole piece toward the stationary pole. When enough power is passed through the coil assembly, the magnetic field produced through the pole pieces will overcome the spring force which holds them in balance. Once this happens, the two pole pieces will collide sending a vibration through the assembly. This vibration is defined as the haptic effect.
The haptic effect can be varied based on the amplitude of the power put into the coil and the duty cycle of this input signal. Once power is removed from the coil assembly, the magnetic field will deteriorate leaving the spring force to re- establish the preset air gap and render the pole pieces, once again, in balance.
As with all electromechanical devices, this actuator is affected by temperature due to its influence on the resistance of the copper magnet wire. Generally speaking, these devices are rated at 20°C These units will have higher strength effects at colder temperatures and lower strength effects at warmer operating temperatures given the same operating conditions otherwise.