Linear motors (also known as linear vibrators or linear resonant actuators) have become increasingly popular in handheld devices such as phones and tablets for providing haptic feedback to the device’s user. The typical linear motor design uses a fixed voice coil in conjunction with a moving magnetic mass. A spring is placed between the mass and the motor’s housing to provide compliance to the moving system.
The design goal of linear motor is to create a “High-Q” system so that the device has a very strong resonant frequency across a narrow frequency bandwidth. The motor is then operated at its resonant frequency to produce maximum output (vibration) while having minimal power demands on the portable device. The strength of the vibration is controlled by adjusting the magnitude of the AC signal input to the motor.