**5. Experiments**

#### *5.1. The Experiments on the Sliding Friction of the Cantilever Touch Beam*

A cantilever touch beam with a ciliary body spacing of 1 mm was used as the experimental object. One sine signal with a voltage amplitude of 100 V and a frequency of 23,200 Hz was supplied to the touch beam. An acrylic touch block with a weight of 0.56 N was slowly moved on the touch beam from left to right. The real-time friction force change of the block on the touch beam was measured by a digital dynamometer. The test environment is shown in Figure 15.

**Figure 15.** The sliding friction force test.

From Figure 16, the following observations were worth noting:

By comparing the results of local-coverage tactile theory calculations with the experimental test results, the variation trend of the equivalent friction coe fficient obtained from the experiment is very close to that of the theoretical calculation. The test results are very similar to the theoretically calculated positions, except that there is a slight error between the theoretical value and the test value at the first trough, while the value of second trough and third trough are very close to the calculated result. However, the error between the test value and the theoretical value is larger at the two peaks of the equivalent friction coe fficient, which we think was caused by the jitter of the thrust of the block when the friction coe fficient increases. In general, however, the overall trend of change in the test data shows the validity of the theoretical analysis.

**Figure 16.** The comparison of the theoretical and experimental data.

#### *5.2. The Experiments of Human Factor*

In order to verify the tactile perception effect of the piezoelectric tactile feedback device, nine of the subjects were invited to perform a touch operation on the tactile device, and the tactile perception effect was evaluated. The subjects were random personnel unrelated to the study. The test environment is shown in Figure 17, and the experimental steps were as follows:


**Figure 17.** The experiments of human factor.

In order to make the test more accurate and comprehensive, the five parameters of operating frequency, operating voltage peak, beam structure, touch direction, and touch pressure were changed in step 3. The specific test methods for the five parameters were as follows:


The scoring guidelines were as follows:

The score was 0 to 10 points, with 0 being no e ffect; 1–4 being very weak; 5–7 being general; and 8–10 being very e ffective.

After the tests, nine subjects felt that the touch beam became smoother after the signal was applied, and the tactile sensation scores of the five important parameters are shown in Table 4.


**Table 4.** The result of the human factor behavior e ffect experimental test scores.

From Table 4, the following observations were worth noting:

