Meng He

Smooth impact drive mechanisms (SIDMs) are widely used in micro/nano positioning owing to their simple structure and high precision. The conventional linearly rising sawtooth waveform fails to account for the nonlinear characteristics of SIDMs, including hysteresis and friction, thereby limiting the net stepping performance. To address this issue, this paper proposes an optimized rising-edge method based on a normalized power function, which generates a driving-force evolution more compatible with the dynamic response of SIDMs. An integrated Bouc–Wen hysteresis model and a LuGre friction model are employed to establish the system dynamics, and the exponent parameter of the power function is offline optimized using a particle swarm optimization algorithm with the objective of maximizing the net stepping size. Experimental results indicate that the proposed waveform enhances the net stepping performance under driving voltages of 30 V, 50 V, and 80 V and frequencies of 100 Hz, 150 Hz, and 200 Hz, achieving a maximum improvement of 105.2%. Load robustness is further demonstrated under different loads (2 g, 3 g, 5 g, and 8 g), with a 33.2% improvement in load capacity at 8 g. Without changing the actuator structure or introducing complex control schemes, the proposed method substantially improves the net stepping behavior by reshaping the rising-edge waveform, offering simple implementation, explicit parameterization and potential for engineering applications.

Piezoelectric linear actuators (PLAs) have emerged as a promising technology for ultrahigh-accuracy positioning applications. This study proposes a PLA design capable of bidirectional motion through stick-slip/slip-stick dual actuation mechanisms. The proposed mechanism distinguishes itself from conventional counterparts by achieving motion direction reversal through strategic phase modulation of driving signals. Finite element analysis (FEA) quantitatively resolves the stick-slip transitions and interfacial transitions in friction dynamics, with the developed dynamic model further revealing hysteresis nonlinearities through systematic characterization of contact mechanics. Experimental results demonstrate frequency-dependent velocity characteristics with maximum forward/reverse velocities of 2.83−3.02 mm/s at 350/400 Hz (100 V_p-p), revealing structural frequency thresholds. Model validation shows 0.1548 μm maximum root mean square error (RMSE), confirming nanometer-scale agreement between simulations and experimental data. The proposed fuzzy proportional-integral-derivative (PID)-regulated hybrid control strategy achieves a 49% reduction in error compared to conventional PID control and maintains an accuracy of 0.11 μm during reverse actuation through real-time parameter adaptation. Furthermore, the system achieves nanometer-level dual-positioning accuracy through the proposed control methodology.

Piezoelectric actuators are widely employed in micro-precision applications due to their fast response and high resolution. This paper investigates the trajectory tracking control of a cantilever piezoelectric stack actuator (CPSA) under external perturbations and hysteresis. A control scheme is proposed that effectively compensates for hysteresis by employing an asymmetric Bouc–Wen model, integrated with a non-singular fast terminal sliding mode control (NFTSMC) featuring a variable convergence law. This methodology guarantees finite-time convergence and robustness, thereby enhancing the overall control performance of the CPSA. Experimental results reveal that the proposed control algorithm significantly improves control accuracy and speed, achieving stable closed-loop system performance and maintaining bounded closed-loop signals within a finite time frame. The effectiveness and superiority of the NFTSMC method are validated through comprehensive experimental studies.

Energy harvesting devices made of piezoelectric material are highly anticipated energy sources for power wireless sensors. Tremendous efforts have been made to improve the performance of piezoelectric energy harvesters (PEHs). Noticeably, topology optimization has shown an attractive potential to design PEHs with enhanced energy conversion efficiency. In this work, an alternative yet more practical design objective was considered, where the open-circuit voltage of PEHs is enhanced by topologically optimizing the through-thickness piezoelectric material distribution of plate-type PEHs subjected to harmonic excitations. Compared to the conventional efficiency-enhanced designs, the open-circuit voltage of PEHs can be evidently enhanced by the proposed method while with negligible sacrifice on the energy conversion efficiency. Numerical investigations show that the voltage cancellation effect due to inconsistent voltage phases can be effectively ameliorated by optimally distributed piezoelectric materials.

This article presented a new type of stick-slip piezoelectric actuator based on an asymmetrical flexure hinge driving mechanism. The key of the driving mechanism was a four-bar mechanism with different minimum thicknesses of right-circle flexure hinges. Combined with a symmetrical indenter, the asymmetrical flexure hinge driving mechanism generated controllable tangential displacement by changing the locking force. Therefore, the simple structured stick-slip piezoelectric actuator achieved considerable improvements especially in output speed and efficiency. In order to obtain improved actuator properties, the minimum thicknesses of asymmetrical flexure hinge driving mechanism, the tangential and normal displacements of the indenter were analyzed and investigated by finite element method. A prototype was fabricated and experiment investigation of the actuator characteristics was presented. Testing results indicated that the actuator achieved the maximum velocity of 15.04 mm/s and its maximum load reached 440 g under a voltage of 100 V_p-p and a frequency of 490 Hz. The maximum efficiency of the actuator was 3.66% with a load of 280 g under a locking force of 5 N and the actuated velocity of 10.17 mm/s.