Design and analysis of a recoil-type vibrotactile transducer
Vibration Motors and their typical response. (a) Various models from Precision Microdrives Ltd. (b) Chirp-like response of a vibration motor to a step input. (c) Reducing the input amplitude by a factor five renders the motor essentially useless.
Voice Coil Actuators. Sources: (a) Moving Coil (USA Motion), (b) Moving Magnet (H2W Technologies).
Actuator arrangement. (a) Shaded parts are made of non-ferromagnetic material. A magnet is suspended by two rubber membranes in gray. The field lines intersect each half of the coil to create an axial force. The coil is arranged such that the current flows in opposite directions in each half. (b) External aspect of a ‘haptuator’. (c) Measurement setup with purely inertial load. (d) The magnetic field lines emanating from the magnet. The arrows show the forces acting on the coil.
Actuator physics. (a) Free-body diagram of the actuator. The two masses are free-floating. The ‘’ parameters can be set by design. The ‘’ parameters represent the load which must be driven. (b) Electrical circuit.
Equivalent circuit. (a) Using the impedance analogy. (b) Using the mobility analogy.
Block representation of the mechanical components, (a) impedance, (b) mobility.
Circuit representation of the electrical circuit combined with the equivalent circuit of the mechanical system.
System Response. (a) Frequency response of the actuator acceleration to input voltage ratio for three different levels (rms). (b) The magnitude and phase plot of a fitted order model. (c) Plot of the impedance of the suspension, .
Actuator scaling properties.
The magnitude of when the real (top) and the imaginary part (bottom) of vary by 20% around the nominal value.
(a) Acceleration output when the load varies from 15 g to 100 g (lowest) with 5 g increments. The thick line in the magnitude plot with the nominal value of 15 g. (b) Acceleration output for values of 30% higher to 30% lower. Each line represents a 10% increment. The thick line in the magnitude plot with the original value, .
Coil optimization. (a) Values of for different coil positions away from the center position. (b) Actuator drive factor given by different coil configuration.
Electrical equivalents to mechanical elements using the impedance or the mobility analogy.
Summary of the main characteristic figures.
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