Design of a linear-rotary ultrasonic motor for optical focusing inspired by the bionic motion principles of the earthworms

Figures & data

Figure 1. The locomotion mechanism of the earthworm and bonded-type transducer (BT). (a) The longitudinal and circular muscles of earthworm. (b) and (d) The longitudinal motion of the earthworm and BT, respectively. (c) and (e) The bending motion of the earthworm and BT, respectively. (f) The longitudinal and bending PZT plates of BT.

Figure 2. The design flow chart of two-DOF USM.

Figure 3. The metal substrate and the tentative working modes. (a) The structure of the cone-shaped horn substrate. (b) Adjustment of the resonant frequencies for the L_2X and bending modes through changing the length of the metal substrate. (c) The second-order longitudinal mode. (d) Two orthogonal third-order modes. (e) Fifth-order and (f) seventh-order bending modes, respectively.

Figure 4. Configurations of the developed two-DOF BT.

Figure 5. Schematic of exciting signals and desired working modes. (a) The exciting signals for two-DOF driving. (b) The electrical wiring diagram of B_5Y mode, (c) B_5Z mode, and (d) L_2X mode.

Figure 6. Schematic illustration of the working principle of two-DOF USM. (a) The linear motion of the proposed motor in one period. (b)The rotary motion of the proposed motor in one period.

Figure 7. Influences of main geometric parameters of BT on B-B frequency. (a) Geometric dimensions of BT. (b) B-B frequency under different h₂. (c) Resonant frequency under different d₁, d₂, and d₃, where the decisive values are marked with light blue stars. (d) Resonant frequency under different h_1.

Figure 8. FEM results of the proposed two-DOF BT. (a) Three desired working modes. (b) The transient analysis results of motion trajectories of the driving surface (at steady state).

Figure 9. Fabrication, assembling process and weight distribution of fully assembled BT.

Figure 10. Testing results of vibration characteristics. (a) Schematic diagram of vibration test of the BT. (b) Vibration characteristics of the L_2X mode. (c) Vibration characteristics of the B_5Z mode. (d) Vibration characteristics of the B_5Y mode.

Figure 11. Experimental setup and results for USM’s speed measurement. (a) Experimental setup for two-DOF speed tests. (b) Frequency sensitivity results for the rotary and linear speeds of the mover.

Figure 12. Relationships between the rotary and linear speeds and the voltage under no-load conditions.

Figure 13. Experimental setup and results for USM’s load/torque measurement. (a) Experimental setups for two-DOF load tests. (b) Two-DOF speeds of prototype under different weights.

Figure 14. Transient response characteristics of linear motion.

Table 1. Comparison of multi-DOF ultrasonic motors in recent years.

Parameters	Liu et al. [39]	Wang et al. [45]	Mashimo et al. [37]	This work
Size (mm)	196 × 57 × 35	86 × 86 × 10.3	14 × 14 × 14	18 × 18 × 108.8
DOF	X,Y	θx,θy,θz	X, θx	X, θx
Voltage (Vp-p)	300	200	118.8	150
Speed	572 mm/s and 543 mm/s	363 rpm, 342 rpm, and 171 rpm	160 rpm and 63 mm/s	3319.6 rpm and 57.6 mm/s
Force/Torque	24 N and 22 N	0.52 N, 0.52 N, and 0.28 N	Not given	0.14 mN·m and 0.06 N

Figure 15. Relationships between the step displacements and the duty factor.

Figure 16. Demonstration of two-DOF motions. (a) Experimental setup for two-DOF motion tests. (b) The demonstration of two-DOF motions.

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