Touch me – feel me!: Page 2 of 5

May 20, 2020 //By Christoph Jehle
Whether for smartphones, vehicles, industrial controls, domestic appliances or gaming consoles, the future belongs to piezo-based push-button solutions with haptic feedback.

Acceleration, force and response time

Fig. 2: Design of square PowerHap actuators.
This family of products includes four types with
edge lengths of between 9.0 mm and 26.0 mm
and insertion heights from 1.1 mm to 2.3 mm.
Thanks to the multilayer technology, forces
in excess of 25 N and displacements of 230 µm
can be achieved.

The actuators of the PowerHap family are based on multilayer piezo plates with copper inner electrodes. Figure 2 illustrates the basic design.  If a voltage is applied to the piezo plate, it only expands minimally in the z axis, but due to the constant volume of the piezo effect it contracts simultaneously in both the x and y axes.

Two titanium cymbals bonded to either side of the plate amplify this contraction by a factor of 15 in the z-axis, achieving a large displacement of up to 230 µm for the largest 2626H023V120 type. The high level of linearity between applied voltage and displacement is advantageous. For this type it is 1.8 µm/V, enabling precise and, at the same time, variable control of both amplitude and signal form.

Fig. 3: Typical acceleration g as a function of the voltage
when a mass of 100 grams is applied. The voltage signal
here is a half-sine with a peak of 120 V and a pulse length
of 5 ms, corresponding to a frequency of 200 Hz.

Thanks to the multilayer piezo technology PowerHap offers unprecedented performance in terms of response time and acceleration. For example, with a rise time of just 1 ms the acceleration of the cymbals is already 15.0 g and attains a maximum value of 35 g when a mass of 100 grams is applied, generating a very large force of up to 25 N. Comparable values cannot be achieved using conventional solutions. Figure 3 illustrates the response time and acceleration for type 2626H023V120.

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