Piezoelectric stick-slip actuator integrated with ultrasonic vibrator for improving comprehensive output performance

Abstract

In this paper, a novel compact piezoelectric stick-slip actuator integrated with ultrasonic vibrator based on ultrasonic anti-friction effect is proposed. Based on inverse piezoelectric effect, the piezoelectric stack generates the axial vibration under the excitation of asymmetric sawtooth wave, the ultrasonic vibrator is composed of a brass block and four piezoelectric plates, which is used to excite the ultrasonic longitudinal vibration mode in the fast deformation phase of piezoelectric stack. Due to ultrasonic anti-friction effect, the backward displacement of the actuator is effectively suppressed, and the bidirectional comprehensive output performance is improved. The prototype is fabricated and the operating principle of hybrid excitation is introduced, then the frequency of the first-order longitudinal vibration mode is explored by finite element analysis and impedance test, and the systematic experimental test is conducted. The test results show that when the sawtooth frequency is 300 Hz, comparing with the traditional sawtooth excitation mode, the proposed hybrid excitation mode can improve the velocities of the forward and backward directions by 30% and 26.7%, and the bidirectional maximum vertical mass loads are increased by 44.4% and 50%. This work provides a design concept that uses ultrasonic vibrator to improve the bidirectional comprehensive output performance of the piezoelectric stick-slip actuator.

Research on Fast and Precise Positioning Strategy of an Ultrasonic Motor Based on the Ultrasonic Friction Reduction Theory

“…Figure 18 shows the measurement chart of the position value and the angular velocity as a function of time based on TPSPM at different initial angular velocities. Based on the values of Δ𝛾 𝑜 and Δ𝛾 𝑜𝑙𝑐 obtained from Equations ( 27) and ( 29), respectively, and the changing trend of 𝑇 𝑑𝑗 and Δ𝛾 𝑜𝑐 with the increasing initial angular velocity obtained by Equation (28), the results obtained from the experimental measurements are shown in Figure 19. Figure 19 shows that Δ𝛾 𝑜𝑐 , Δ𝛾 𝑜 , 𝑇 𝑑𝑗 , and Δ𝛾 𝑜𝑙𝑐 are positively correlated with the initial angular velocity, which confirms that the sliding displacement, Δ𝛾 𝑧𝑤 , is the reason for the large deviation of the theoretical displacement reservation value.…”

“…Figure 19 shows that Δ𝛾 𝑜𝑐 , Δ𝛾 𝑜 , 𝑇 𝑑𝑗 , and Δ𝛾 𝑜𝑙𝑐 are positively correlated with the initial angular velocity, which confirms that the sliding displacement, Δ𝛾 𝑧𝑤 , is the reason for the large deviation of the theoretical displacement reservation value. In addition, the experimentally measured positioning time and the variation trend of Equation ( 16) are Based on the values of ∆γ o and ∆γ olc obtained from Equations ( 27) and ( 29), respectively, and the changing trend of T dj and ∆γ oc with the increasing initial angular velocity obtained by Equation (28), the results obtained from the experimental measurements are shown in Figure 19. Based on the values of Δ𝛾 𝑜 and Δ𝛾 𝑜𝑙𝑐 obtained from Equations ( 27) and ( 29), respectively, and the changing trend of 𝑇 𝑑𝑗 and Δ𝛾 𝑜𝑐 with the increasing initial angular velocity obtained by Equation (28), the results obtained from the experimental measurements are shown in Figure 19.…”

“…When the signal-driving time is in the time period 𝑡 𝑠𝑑 , the rotation angle changes from 𝛾 𝑟𝑜 (𝑡 02 ) to 𝛾 𝑟𝑜 (𝑡 03 ). The control system keeps the stator and the friction material in the ultrasonic friction reduction by controlling the driving circle frequency, 𝜔 𝑢 [28,29], such that the equivalent friction coefficient, 𝜇 𝑤 ̅̅̅̅, (Equation (S.1) in the Supplementary Material) is smaller than the sliding friction coefficient, 𝜇 0 . The sliding friction force, 𝑓 𝑠𝑙𝑖𝑑𝑐 , and the maximum static friction force, 𝑓 𝑠𝑐𝑚𝑎𝑥 , in the case of ultrasonic friction reduction can be obtained by multiplying both sides of Equation (S.1) by the pre-pressure, 𝐹 𝑐 , as follows: The control system keeps the stator and the friction material in the ultrasonic friction reduction by controlling the driving circle frequency, ω u [28,29], such that the equivalent friction coefficient, µ w , (Equation (S1) in the Supplementary Material) is smaller than the sliding friction coefficient, µ 0 .…”

“…The control system keeps the stator and the friction material in the ultrasonic friction reduction by controlling the driving circle frequency, 𝜔 𝑢 [28,29], such that the equivalent friction coefficient, 𝜇 𝑤 ̅̅̅̅, (Equation (S.1) in the Supplementary Material) is smaller than the sliding friction coefficient, 𝜇 0 . The sliding friction force, 𝑓 𝑠𝑙𝑖𝑑𝑐 , and the maximum static friction force, 𝑓 𝑠𝑐𝑚𝑎𝑥 , in the case of ultrasonic friction reduction can be obtained by multiplying both sides of Equation (S.1) by the pre-pressure, 𝐹 𝑐 , as follows: The control system keeps the stator and the friction material in the ultrasonic friction reduction by controlling the driving circle frequency, ω u [28,29], such that the equivalent friction coefficient, µ w , (Equation (S1) in the Supplementary Material) is smaller than the sliding friction coefficient, µ 0 . The sliding friction force, f slidc , and the maximum static friction force, f scmax , in the case of ultrasonic friction reduction can be obtained by multiplying both sides of Equation (S1) by the pre-pressure, F c , as follows:…”

An umbrella-shaped flexible mechanism piezoelectric actuator with driving foot trajectory control

“…Stepping piezoelectric actuators accumulate tiny displacements to achieve centimeter-level stroke [12]. Stepping piezoelectric actuators according to the principle of motion is divided into friction inertia piezoelectric actuators [12], inchworm piezoelectric actuators [13][14][15], ultrasonic piezoelectric actuators [16,17] and so on. Among them, the parasitic inertia type piezoelectric actuator in the friction inertia piezoelectric actuator can realize the precision displacement output of large stroke by using the simple structure, and its control strategy is also relatively simple, which has been widely concerned by researchers and scholars [18].…”