Research on the Productization Design of Large-Stroke and High-Precision Non-Resonant Piezoelectric Actuators

Abstract

Stick-slip actuators have emerged as a promising solution for precision positioning, which can help attain a nanometer-scale resolution and large stroke size. This review summarizes recent advances in the design, modeling, and performance enhancement of non-resonant stick-slip actuators systematically. Three fundamental actuation principles, including conventional, parasitic, and hybrid types, are reported, which highlight their respective mechanisms for stepwise motion generation. We examine the development of linear and rotational actuators and reveal the function of compliant amplification mechanisms, asymmetric stiffness configurations, and bio-inspired architectures in improving step consistency, load capacity, and compactness. We also examine the effects of step displacement optimization, active preload control, and advanced dynamic modeling on motion precision. We suggest that future development prioritize enhancing driving force, suppressing backward motion, improving dynamic response, and ensuring long-term reliability.

1. Introduction

The advancement of fields such as aerospace, optics, precision manipulation and manufacturing has posed stringent demands for precision positioning platforms with sub-micrometer- or even nanometer-scale resolution over centimeter-scale travel ranges [1,2,3,4,5]. Conventional motor-driven stages can fulfill the requirements for long travel and high load capacity, while they depend on transmission mechanisms to convert rotary into linear motion. This inherent mechanical transmission introduces backlash, friction, and elastic deformation, which fundamentally limits positioning accuracy on the micrometer level [6,7]. Direct-drive linear motors eliminate these intermediate mechanical components, which can achieve superior motion fidelity, faster dynamic response, and significantly improved accuracy. However, their poor self-locking capability hinders their broader application, which compromises stability and safety in vertical applications [8,9].

For precision positioning applications, electrostatic and electrothermal mechanisms are compatible with MEMS fabrication, which can achieve a compact structure. However, they often struggle with limited force output and slow cooling-dependent recovery cycles, respectively. Piezoelectric actuators (PZT) serve as a foundational ferroelectric ceramic that adopts a perovskite crystal structure. This material is particularly valued because it maintains a morphotropic phase boundary, which allows the polar axes to reorient with minimal energy under an applied electric field. Such unique crystallo-graphic behavior leads to high dielectric constants and electromechanical coupling. PZT actuators utilize the inverse piezoelectric effect to generate precise displacement under applied voltages and have attracted significant attention in the field of precision positioning because PZT actuators possess the advantages of high motion accuracy, fast response, and large driving force [10,11,12,13]. Based on the actuation principle, PZT positioning platforms can be classified into the direct-drive type [14,15], inertial-drive type [16,17], inchworm-drive type [18,19], ultrasonic-drive type [20,21], and stick-slip-drive type [22,23]. To enlarge the output displacement of PZT actuators, direct-drive stages are usually designed with flexible amplification mechanisms. However, the motion strokes in this kind of stage can only reach tens to hundreds of micrometers [24,25]. Inertial-drive platforms can achieve larger motions through repeating step motions; however, controlling complexity and stability are still challenges [26]. Inchworm-type mechanisms enable long-range, high load capacity and high-resolution movement. However, multi-phase control and intricate structural design limit their application [27]. High-frequency vibration is employed in ultrasonic-drive platforms to produce smooth motions. Sophisticated control of its vibration mode and heat generation are two pressing challenges that need to be addressed [28]. In contrast, the stick-slip drive mechanism distinguishes itself by combining a compact structure with relatively simple control signals. Simultaneously, it maintains high positioning accuracy and a substantial force output [29,30]. These advantages make stick-slip actuators particularly suitable for miniaturization, control simplicity, and precision applications.

The structural stability of stick-slip actuators is a critical factor determining attainable speed, load capacity, and motion consistency. Therefore, enhancing the structural rigidity and natural frequency of the drive unit through mechanical design has become an important research focus [31]. Furthermore, the ability to dynamically adjust the normal contact force between the actuating foot and the slider during the stick and slip phases is another pivotal parameter that directly influences the platform’s load capacity and backward motion [32,33]. To address this challenge, several solutions, encompassing both novel mechanical designs and coordinated control strategies, have been proposed [34,35,36,37]. By integrating mechanisms with asymmetric stiffness or specially designed compliant structures, actuators can generate coupled output displacement at the driving foot [38]. This design principle enables the actuating foot to simultaneously generate a forward tangential displacement and an elongating motion in the normal direction during the stick phase, which can be used to actively increase the frictional force between the driving foot and slider to propel the slider more effectively and stably. Conversely, during the slip phase, the foot retracts tangentially while undergoing a contraction in the normal direction, which minimizes the undesired backward motion of the slider by reducing friction. Considering the driving principle of the stick-slip actuator, it is crucial to conduct dynamic characteristic analysis and friction behavior research to reveal its potential working mechanism and provide theoretical guidance for structural design. An accurate dynamic model is essential for stick-slip actuator dynamic characteristic analysis, and suitable friction models should be built to describe the contact interface behavior between the actuating foot and the slider [39]. The dynamic model can reveal how different driving signals, such as sawtooth, asymmetric sinusoidal, or step-like waveforms, and their specific parameters, including voltage amplitude, rising/falling slope, and frequency, influence single-step displacement characteristics.

Existing literature reviews on stick-slip actuators primarily focus on the evolution of piezoelectric driving mechanisms, the systematic classification of mechanical structures, and the evaluation of control strategies. To address the critical challenges of significant backward motion, limited load-carrying capacity, and unpredictable stepping efficiency in stick-slip actuators, this paper surveys their driving mechanisms in conventional, parasitic, and hybrid configurations. The working principles of diverse actuators designed to mitigate these issues are elucidated, complemented by a comprehensive review of their practical applications in both linear and rotary motion systems. This paper is structured as follows: Section 2 analyzes the stick-slip actuating principle; studies on linear stick-slip actuators are introduced in Section 3; Section 4 describes the rotational stick-slip actuator; Section 5 critically examines recent research progress dedicated to enhancing the motion accuracy of stick-slip piezoelectric actuators; we propose some prospects in Section 6; and finally, Section 7 concludes this paper.

2. Stick-Slip Actuating Principle

The concept of stick-slip actuators was first systematically proposed in the 1980s, aiming to fulfill the demand for long-range, nanometric positioning in instruments like scanning tunneling microscopes [40]. Entering the 21st century, with the development of micro-nanomanipulation, precision optics, and semiconductor manufacturing, more and more attention has been attracted to stick-slip technology [16,41,42]. An alternating cycle of interface adhesion and inertial sliding is the basic working principle for achieving large-stroke motion [43]. The preload between the driving foot and slider is a key parameter influencing its performance. Based on the preload adjustment method, existing stick-slip actuators can be divided into three types, named conventional stick-slip actuators [44], parasitic stick-slip actuators [45] and hybrid stick-slip actuators [46]. A comparison of these stick-slip actuators is listed in

Table 1. Comparison of fundamental actuation principles for stick-slip actuators.

Property	Conventional Stick-Slip	Parasitic Stick-Slip	Hybrid Stick-Slip
Drive Mechanism	Inertia & Sawtooth Wave Friction Difference	Structural coupling	Dual-actuation (Parasitic + Active PZT)
Normal Force	Constant (Static preload)	Passive modulation (Coupled with drive)	Active/dynamic adjustment
Backwards	Significant	Effectively suppressed	Minimized/eliminated
Load Capacity	Low to Moderate	High	Maximum
Structure	Simple & Compact	Integrated flexure mechanism	complex (Multiple PZT units)

. The traditional stick-slip actuator has a simple structure and direct control, but it exhibits significant backlash and has a relatively limited load capacity. Parasitic stick-slip actuators generate coupled displacements at the driving foot, which increases the normal pressure between the driving foot and the slider during the stick phase and reduces it during the slip phase. A changing preload can be used to improve the load capacity and minimize backward motion. Hybrid stick-slip actuators integrate additional PZT actuators with parasitic mechanisms, which enable flexible and dynamic adjustment of the pressure between the driving foot and the mover. This configuration can effectively reduce backward displacement and enhance load capacity.

From an industrial application perspective, the selection of stick-slip actuators necessitates a trade-off analysis between kinematic performance and economic costs.

Table 2. Comparative analysis of economic and manufacturing factors.

Actuator Category	Fabrication Complexity	Cost	Control System Overhead
Conventional	Minimal parts; simple sliding contact	Low	Single-channel sawtooth driver
Parasitic (Single PZT)	Requires EDM for monolithic flexure hinges	Low	Single-channel sawtooth driver
Parasitic (Dual PZT Flexure)	Symmetrical machining and assembly	Medium	May require synchronized or differential signals
Hybrid (Multiple PZT)	Multi-stage decoupling structures	High	Requires multi-channel high-bandwidth amplifiers
Multi-DOF Hybrid	Complex 3D compliant mechanisms	Very high	Requires multi-channel high-bandwidth amplifiers

concludes the comparative analysis of economic and manufacturing factors. Conventional direct-drive actuators represent the most cost-effective solution due to their structural simplicity and minimal part count. The introduction of flexure-based parasitic actuators—whether utilizing single or dual PZT configurations—shifts the cost driver toward precision manufacturing, specifically the high-fidelity Wire Electrical Discharge Machining required for monolithic compliant mechanisms. For more complex hybrid and multi-DOF configurations, the economic bottleneck transitions from the mechanical frame to the electronic infrastructure. The requirement for synchronized, multi-channel high-voltage power amplifiers and real-time FPGA-based control systems exponentially increases the total system cost.

The actuating principle of the conventional stick-slip actuator is illustrated in Figure 1a. A single PZT element is adopted to actuate the mechanism by applying an asymmetric triangular voltage signal. The differential response of the friction force between the driving foot and slider to the varying sliding rates of the applied voltage is the key to achieving continuous forward motion [47,48]. The slow elongation of the PZT actuator from t₀ to t₁ results in a coordinated forward motion of the slider. A large displacement, Δx₁, can be achieved in this phase due to the prevailing static friction. In the subsequent rapid ramp-down phase (from t₁ to t₂), the rapid contraction of the PZT actuator causes a small reverse motion, Δx₂. Then, the total forward motion of the slider during one actuating cycle can be calculated by

$$\Delta d=\Delta x_1-\Delta x_2$$

(1)

The motion principle of the parasitic stick-slip actuator is similar to that of its conventional counterpart, and it also features an adjustable preload force [49,50]. The applied voltage and the corresponding slider motion can be depicted in Figure 1a. During the stick phase, the driving foot not only advances forward but also undergoes an extending displacement perpendicular to the direction of motion, which can enhance the frictional force between the driving foot and the slider. As the voltage decreases abruptly, the driving foot retracts to its initial position. In this process, the friction force progressively diminishes, which is conducive to reducing the retracting displacement Δx₂. Hence, many developed innovations have focused on the design of this mechanism to ensure the generation of parasitic displacement.

Distinct from the aforementioned two types of actuators, the hybrid stick-slip actuator usually comprises two PZT units, an actuation mechanism, and a preloading mechanism. Additionally, the actuating voltage signals need to be coordinated [51,52]. The operational principle of this actuator is schematically illustrated in Figure 1b. A square-wave voltage signal is applied to PZT2, while an asymmetric triangular-wave voltage is applied to PZT1. During the interval from t₀ to t₁, a voltage with amplitude V₁ is applied to PZT2. Then, the extension of PZT2 can increase the contact force between the driving foot and the slider. From t₁ to t₂, the voltage applied to PZT1 ramps up gradually from 0 to V₂, while the voltage for PZT2 remains constant at V₁. In this process, the slider will move forward with the extension of PZT1. Subsequently, during the interval from t₂ to t₃, the voltage applied to PZT2 drops abruptly to 0. This retraction is helpful for minimizing the friction between the driving foot and the slider. Concurrently, the voltage applied to PZT1 rapidly decreases to 0, which can ensure a swift retraction of the driving foot to its initial state and reduce the retraction of the slider.

By repeating the actuating cycle, a traveling range on the scale of millimeters or greater can be achieved. The velocity of the motion can be adjusted by controlling the frequency and amplitude of the voltages. Over the past few years, various linear and rotary precision positioning stages have been developed based on the aforementioned stick-slip actuation principles, as summarized in

Table 3. Performance comparison of different types of piezoelectric stick-slip actuators.

Ref	Actuating Principle	Voltage (V)	Frequency (Hz)	Speed	Horizontal Load Capacity (g)	Dimension
[53]	Conventional linear stick-slip actuator	100	600	4.86 mm/s	-	85 mm × 50 mm × 32 mm
[54]	Conventional linear stick-slip actuator	120	150	0.382 mm/s	3.2	Φ32 mm × 230 mm
[55]	Conventional rotational stick-slip actuator	100	380	316.45 mrad/s	-	52.5 mm× 36 mm × 13 mm
[56]	Conventional rotational stick-slip actuator	100	700	231,320 μrad/s	-	38 mm × 23 mm × 8 mm
[57]	Parasitic linear stick-slip actuator	100	159	7.192 mm/s	30	53 mm × 48 mm × 18 mm
[58]	Parasitic linear stick-slip actuator	100	560	19.33 mm/s	180	55 mm × 40 mm × 9 mm
[59]	Parasitic linear stick-slip actuator	100	600	11.44 mm/s	280	33 mm × 31 mm × 9 mm
[60]	Parasitic rotational stick-slip actuator	150	1200	10.66 rad/s	-	75 mm × 60 mm × 20 mm
[61]	Parasitic rotational stick-slip actuator	100	500	1042.99 mrad/s	-	75 mm × 60 mm × 20 mm
[62]	Parasitic rotational stick-slip actuator	100	1400	1452 mrad/s	-	-
[63]	Hybrid linear stick-slip actuator	150	350	4.55 mm/s	170	38 mm × 31 mm × 9 mm
[64]	Hybrid linear stick-slip actuator	100	7000	13.95 mm/s	150	-
[65]	Hybrid linear stick-slip actuator	120/52	500	1.95 mm/s	-	97 mm × 91 mm × 25 mm
[66]	Hybrid rotational stick-slip actuator	100	80	88.68 μrad/s	-	105 mm × 50 mm × 17 mm
[51]	Hybrid rotational stick-slip actuator	150	5	150.17 μrad/s	-	-
[67]	Hybrid rotational stick-slip actuator	150	2000	4491.38 mrad/s	-	Φ36 mm × 10 mm

. These advancements have been extensively integrated into high-speed precision scanning systems, micromanipulation robots, and ultra-precision machining units.

3. Linear Stick-Slip Actuator

Stick-slip actuators have emerged as an important driving solution for high-performance linear platforms to achieve high precision and large strokes [68,69]. Through continuous step-by-step motion, they can achieve nanometer-level resolution within a centimeter-scale range, which means they are suitable for micro-nanomanipulation and precision alignment applications.

Initially, stick-slip actuators employed a single PZT element to drive the slider in a stepwise manner for long-range travel, during which the friction force between the driving foot and the slider remained constant. However, this configuration often induced considerable backward motion, which depressed the positioning accuracy. To address this issue, a second PZT was introduced to actively regulate the normal preload [70], as shown in Figure 2a. For this configuration, two PZT elements were used to actuate the slider and adjust the preload force directly, without compliant amplification mechanisms (CAM). An integrated arc-plate flexible foot, which enlarged the contact area by deforming under the action of the contact force between the driving foot and slider, was used to further enhance the stick-slip actuator’s performance. Another approach introduces a dual-foot architecture, where an active driving foot propels the slider while a passive damping foot secures it during the slip phase [71]. The backward motion can be restrained to less than 1% without sacrificing locking force. In a related design, the preload force is dynamically adjusted by longitudinal transducers during operation [72]. In addition, conventional sinusoidal voltages were replaced with sawtooth signals, which enable the same actuator to achieve a fine resolution of 19 nm. To improve the motion capability, a 2-DOF stick-slip actuated positioning stage was developed, where the driving part and active clamping mechanism for friction control are actuated by separate PZT elements [73], as shown in Figure 2b. The nonlinearity was addressed through advanced compensation techniques and decoupling mechanisms, which improve tracking accuracy without relying on a complex dynamic model. Due to the absence of CAM, the step displacement can only reach a few to ten micrometers, limited by the stroke of the PZT actuator, which affects the moving velocity of the platform. Although motion speed can be increased by raising the input voltage frequency, this frequency cannot be extended indefinitely, as it is restricted by dynamic mechanical constraints.

To overcome the limitation of the stepping stroke, CAMs were subsequently introduced to magnify the output displacement of the PZT actuators. Lever, bridge-type, rhombic, and triangular mechanisms can effectively enhance the stepping stroke. By employing asymmetric structural designs or exploiting the inherent kinematic characteristics of CAMs, parasitic motion can be generated and utilized to actively adjust the preload between the driving foot and slider. Owing to the inherent kinematic coupling at its output, the lever mechanism offers considerable potential for developing stick-slip actuators with integrated parasitic motion, and several relevant innovations have been reported. To improve bidirectional motion consistency, a symmetrically configured rotary mechanism was designed based on the lever principle, as illustrated in Figure 3a, where a single driving foot is designed to reduce discrepancies induced by assembly tolerances [74]. This optimized configuration achieved a notably low velocity deviation rate of 1.6% at 100 V and 10 Hz between two axes, which indicates that the configuration exhibits stable bidirectional performance across a wide frequency range without requiring complex structural modifications. In a different structural approach, an asymmetric lever-based stick-slip actuator was proposed [75]. A dual-foot stator with different stiffness was employed to generate opposing frictional forces to effectively suppress backward motion. This structure enables smooth, non-regressive displacement even under low voltage and frequency excitation, and a motion resolution of 237.6 nm can be achieved. Separately, a low-stiffness contact strategy was introduced by substituting conventional rigid driving feet with flexible ones, which could significantly desensitize the actuator to variations in preload deformation and assembly misalignments [76]. This method allowed a compact stick-slip actuator to achieve high assembly interchangeability, reliable performance over repeated reassembly cycles, and stable long-stroke motion without requiring fine-tuning. Furthermore, a dual-mode stick-slip actuated stage was developed by integrating both long-range coarse positioning and high-resolution scanning within a unified structure [77]. Through active regulation of the contact force during scanning, the motion resolution can be improved from 0.638 nm to 0.192 nm.

Due to its inherent kinematic coupling and exhibition of superior dynamic performance, the triangular CAM offers a viable alternative to the lever-type design for stick-slip actuators. For backward motion compensation, one strategy leverages two sawtooth driving signals with a specific initial time gap [78]. By adopting this method, step size and speed can be significantly improved, particularly at lower frequencies. In contrast, the other strategy is based on structure design to reduce backward motion. A single PZT-actuated dual-driving-foot configuration with asymmetric stiffness was proposed that utilized the intrinsically generated phase difference to suppress backward motion and enhance performance at higher frequencies [79]. For asymmetrically structured actuators, the actuating force can induce parasitic motion at the output end. The parasitic ratio, which influences the preload between the driving foot and slider, can be regulated by optimizing the structural parameters. Based on this principle, a bridge-type CAM with asymmetric hinge stiffness was developed to strategically redistribute the elongation of the PZT to obtain the actuating and parasitic motion [80], as shown in Figure 3b. This design achieved a significantly enlarged stepping stroke of 102 μm, a high velocity of 23.53 mm/s, and nanometer-scale resolution. Further advancing this approach, a systematic topology optimization framework was employed to design a CAM to maximize the displacement amplification ratio in the driving direction while actively constraining parasitic displacement [81]. This driven methodology enabled a high velocity of 15.25 mm/s at a relatively low frequency of 650 Hz. Additionally, several studies leverage specially designed CAMs to develop parasitic motion-based stick-slip actuators to achieve high load capacity and velocity. For instance, one design employed a symmetrical Z-shaped flexure mechanism to achieve bidirectional motion [82]. The stick-slip actuator is activated selectively by two PZT units. The resolutions in the forward and reverse directions can reach 106 nm and 84 nm, respectively. In a parallel development, a compact actuator incorporating a symmetric rhombus-type mechanism was proposed, as shown in Figure 3c, that could generate lateral and vertical motion simultaneously [83]. This design utilized a dual driving-foot configuration to enhance load capacity while ensuring consistent step displacement and high resolution in both motion directions.

Figure 3. Linear stick-slip actuator utilizing parasitic displacement for preload force adjustment. (a) A rotation-structure-based stick-slip actuator with high consistency in forward and reverse motions [74], (b) an asymmetric bridge-type mechanism based on stepping stroke [80], (c) a rhombus-type stick-slip actuator with two driving modes [83].

Figure 3. Linear stick-slip actuator utilizing parasitic displacement for preload force adjustment. (a) A rotation-structure-based stick-slip actuator with high consistency in forward and reverse motions [74], (b) an asymmetric bridge-type mechanism based on stepping stroke [80], (c) a rhombus-type stick-slip actuator with two driving modes [83].

To further enhance the performance of stick-slip actuators, a dual-preload adjustment strategy has been proposed [84]. For these stick-slip actuators, they are composed of both a special mechanism and an auxiliary PZT element. By adopting this approach, the normal force between the driving foot and the slider can be significantly improved, and the reverse motion can be reduced effectively. One representative design features a hybrid architecture that integrates a parasitic displacement mechanism with a dedicated lever amplification mechanism [85]. In this configuration, an additional PZT element actively regulates the normal force at the driving interface. Driven by synchronized waveforms, this dual-mechanism design successfully suppresses backward displacement. At the same time, continuous contact can be maintained to improve stepping efficiency and achieve a maximum speed of 2.26 mm/s under load. Another stick-slip actuator composed of two lever mechanisms, with a flexible driving foot and two separate PZT elements, as shown in Figure 4, can achieve consistent bidirectional motion [86]. The normal force between the driving foot and the slider is adjusted by both the lever mechanism and separate PZT element. This integrated design enhances dynamic control of the contact interface and enables high-speed operation even at low driving frequencies and with small piezoelectric elongations.

In summary, the selection of stick-slip actuator configurations involves a strategic trade-off between structural complexity, output displacement, and motion stability. Direct-driven architectures without CAMs are characterized by high stiffness and compact footprints, which are ideal for high-precision, low-stroke applications. The integration of dual-PZT elements or dual-foot structures can effectively suppress backward motion, which is suitable for heavy-load positioning and high-resolution scanning tasks. Conversely, CAM-based actuators are preferred for high-speed and long-range travel requirements because they can significantly amplify the stepping stroke and velocity. Within this category, asymmetric or parasitic-motion mechanisms offer an autonomous solution for dynamic preload regulation, enhancing bidirectional consistency without complex control algorithms. Finally, hybrid architectures that combine CAMs with auxiliary active clamping represent the most robust solution for high-performance systems requiring both high load-carrying capacity and minimized regressive displacement.

4. Rotational Stick-Slip Actuator

For rotational systems, the stick-slip principle has been successfully adapted to generate continuous rotational motion with an unlimited angular range and micro-arc-level resolution, providing key technological support for precision optical alignment and pointing mechanisms in optical systems and aerospace applications [87,88]. Similarly, load capacity and backward motion are also limitations for their utilization due to the friction-actuating approach. To settle this problem, researchers have paid much attention to the development of advanced friction interface materials, innovative structural designs (e.g., active clamping mechanisms or hybrid actuation modes), and sophisticated driving waveforms to enhance load-bearing performance and minimize unwanted backward motion [89,90,91]. Among these approaches, structural designs and driving signals present distinct advantages over new friction materials. Although advanced materials like diamond-like carbon coatings improve durability and friction, their development involves complex processes and higher costs. In contrast, structural innovations such as active clamping or hybrid actuation directly enhance load capacity and motion stability through mechanical decoupling. Similarly, waveform optimization offers a flexible strategy to precisely control stick-slip dynamics and minimize backward motion without hardware modifications.

Parasitic motion perpendicular to the primary motion direction offers an effective means of regulating the friction between the driving foot and the slider in rotary stick-slip actuators. This approach avoids the need for additional PZT actuators or auxiliary mechanisms. By employing this method, a more compact structure and simplified control strategy can be achieved, which is particularly advantageous for microsystems with stringent size constraints. For instance, a dual-drive rotary platform utilizing a flexure-based mechanism to generate controlled parasitic displacement was proposed, as shown in Figure 5a [92]. By actively modulating the normal force, the configuration enhances static friction during the stick phase to improve thrust while reducing kinetic friction in the slip phase to minimize backward motion. To mitigate performance degradation in stick-slip actuators with low-inertia rotors, an auxiliary friction method was introduced [93]. An additional friction plate applies a counteracting force to suppress reverse motion during slip. This strategy boosted the output torque by a factor of 55, and a high resolution of 1.2 μrad and a speed of 367.5 mrad/s were achieved. Another approach employs an asynchronous-driven dual-stator configuration that incorporates compact force-couple flexure mechanisms [94]. The two stators operate alternately to actively increase static friction in the stick phase and counteract reverse sliding friction in the slip phase to suppress backward displacement. Similarly, a compact rotary stick-slip actuator, designed with a symmetrical, flexible mechanism and a connecting ring, was developed, where the four driving feet are actuated via only two PZT actuators [95]. The parasitic motion principle likewise enhances static friction in the stick phase and reduces kinetic friction in the slip phase. A high-speed stepping motion of up to 151.4 mrad/s under non-resonant operation can be obtained. However, as actuators continue to miniaturize, the trade-offs among step resolution, speed, and long-term reliability under high-frequency cycling become increasingly acute. Future research must address the integrated modeling of dynamic friction, wear, and heat dissipation in micro-scale interfaces to improve the performance of the stick-slip actuator fundamentally. Additionally, developing adaptive control algorithms that can compensate for performance degradation over time is another important area.

The core principle of stick-slip actuators is inspired by the locomotion of organisms, where motion is achieved through a controlled cycle of adhesion and release. This natural mechanism is replicated in engineering by mimicking biological structures using compliant mechanisms and smart materials. Recent advances aim to develop actuators that are compact and have high resolution and large strokes for precision robotics and microsystems. For instance, a bio-inspired stick-slip actuator mimicking the articulated joints and curved tibial spur of a mantis foreleg was fabricated [67]. A variable-stiffness flexure hinge that enables in situ adjustment of the contact state with the rotor was employed. This configuration utilizes stored elastic energy to fully suppress backward motion, which obtains smooth, high-speed rotation with ultra-high resolution in a miniaturized footprint. In another approach, as illustrated in Figure 5b, a PZT-and-thermal-combining actuated stick-slip rotary actuator was manufactured, where mantis leg-inspired claws were utilized to improve frictional engagement during motion [96]. A macroscopic resolution of 0.2 μrad through PZT action and a thermal resolution of 0.00073 °/°C were achieved, where the rotational fallback was effectively reduced via structurally optimized compliance. Further extending this biomimetic paradigm, a kangaroo leg-inspired actuator was developed, where an elastic drive mechanism that emulates the tendon–foot function to store and release elastic potential during operation was incorporated [97]. With a single PZT unit and a coupled amplification flexure hinge, the step displacement in both the stick and slip phases were enhanced, reaching a step efficiency of 38.6%.

In addition to the aforementioned approaches, several other strategies have been developed to enhance the performance of stick-slip actuators. A dual-mode excitation strategy for a flexure hinge-type actuator was employed, where auxiliary PZT plates superimpose high-frequency ultrasonic vibration during the slip phase to reduce friction [55]. By introducing the vibration, backward motion is suppressed, and velocity, load capacity, and stepping consistency are improved. Another study utilized a spatial screw compliant mechanism to mechanically amplify the output of a linear PZT actuator [98]. A significantly enlarged stepping angle that enables high rotational speeds at low operating frequencies was created, and backward motion was minimized. Furthermore, a longitudinal-torsional motion conversion mechanism and a threaded transmission were integrated to form a screw-type actuator, which achieved both high thrust force density (384.86 mN/cm³) and passive self-locking within a compact cylindrical footprint [99]. Additionally, an asynchronous driving method with coordinated preload control was proposed, which implemented dual driving units with independent preload modules [100]. Backward motion could be eliminated by dynamically modulating preload via synchronized square and sawtooth waveforms.

Like the selection principle for linear stick-slip actuators, parasitic motion-based designs can miniaturize rotational platforms, since they can achieve dynamic friction regulation without auxiliary PZT actuators. Bio-inspired mechanisms, such as those mimicking mantis or kangaroo limbs, utilize variable-stiffness flexure hinges and elastic energy storage to achieve high step efficiency and ultra-high resolution, which provides a novel design process. Furthermore, hybrid and multi-mode excitation strategies offer a versatile approach to enhance load capacity and bidirectional consistency in complex environments.

5. Motion Precision Improvement

5.1. Step Motion Mechanism

The step displacement of a stick-slip actuator serves as the fundamental unit for achieving large strokes. And its stability and predictability directly determine the overall motion accuracy of the platform. Through precise modeling of the dynamic behavior and active control of the driving frequency, voltage amplitude, and friction force during the single-step motion, the step displacement can be effectively predicted and adjusted in real time. This approach fundamentally suppresses backward motion, eliminates cumulative errors, and significantly improves the resolution, repeatability, and trajectory-tracking accuracy of the positioning platform.

Recently, studies quantitatively analyzing and optimizing single-step motion characteristics have been carried out to enhance the overall performance of the stick-slip actuator, as shown in

Table 4. Methodologies for optimizing single-step motion characteristics.

Methodology	Core Mechanism	Objective	Key Performance Improvement	Ref.
Energy-Based Metric	Critical energy ratio	Establish link between drive signals and motion states	Suppressed backward motion; improved resolution	[101]
Dual-Actuator Coordination	Dual PZT stack modulation	Transform backward motion into a tunable parameter	Controlled hierarchical micro/nanostructures	[102]
ModelBbased GA Optimization	Genetic algorithm + dynamic modeling	Co-optimize mechanism dimensions and signal waves	29.48% velocity increase; higher energy efficiency	[103]
Cascaded Friction Modeling	Analytical scannable trajectory set	Define safe operational bounds for slip-free scanning	1–2 orders of magnitude gain in scanning range	[104]
Gap-Based Dynamic Analysis	Critical initial gap identification	Address system deformation and response lag	Zero backward motion without altering drive signals	[105]

. These studies employ diverse methodologies, from energy-based metrics and dual-actuator control to model-based optimization and dynamic boundary identification, to improve motion consistency, efficiency, and output capability. A critical energy ratio was proposed as a unified metric to regulate single-step motion, where a quantitative link between drive signals and motion states is built to suppress backward motion and improve positioning resolution in micro-nanofabrication [101]. Another method utilizes dual PZT stacks to actively coordinate forward and backward displacement, transforming typically parasitic backward motion into a controllable parameter for creating tunable hierarchical micro/nanostructures, with feature geometry dictated by the backward ratio [102]. Further, a model-based optimization framework combining dynamic modeling and genetic algorithms was developed to co-optimize flexible mechanism dimensions and driving signal shapes [103]. By minimizing slip-phase friction work, energy transfer efficiency is increased, yielding more consistent step displacement and raising velocity by up to 29.48% at high frequencies. Additionally, a cascaded dynamic-friction model analytically determines the actuator’s scannable trajectory set, defining safe operational bounds for slip-free scanning and enabling a large scanning range, achieving a 1–2 order-of-magnitude gain over conventional methods through driving frequency optimization [104]. Finally, systematic investigation into the initial gap reveals its decisive role in single-step behavior [105]. Via modeling step dynamics with system deformation and response lag, a critical gap has been identified to eliminate backward motion (ΔS = 0), offering a simple yet effective means to enhance step efficiency without altering drive signals or control.

5.2. Active Control of Preload

It is known that the contact force between the driving foot and the slider is a critical parameter that affects the step displacement of the stick-slip actuated platform. Several methods have been proposed to adjust the contact behavior, and contact force monitor approaches have also been reported. Active control of the preload between the driving foot and the rail has emerged as a frontier and critical research direction for optimizing the output performance of stick-slip piezoelectric actuators. By precisely regulating this core frictional interface, backward motion can be directly suppressed. At the same time, self-locking stability can be enhanced and speed-load capability can be expanded.

The active monitoring and control of the interfacial preload are two effective approaches to overcome the limitations inherent in conventional static preloading. This is achieved by dynamically regulating the mechanical state at the critical frictional interface. This pathway addresses long-standing inherent challenges, which include motion nonlinearity and backward motion. Furthermore, the traditional trade-off between load capacity and driving speed can be mitigated. A contact force-measuring approach was examined by integrating strain gauges directly into the compliant driving mechanism, which enabled real-time measurement and closed-loop control of the contact force [106]. Disturbances like surface unevenness can be compensated for using this active regulation, significantly improving motion linearity in long-stroke operation. Simultaneously, the linear correlation coefficient can be increased from 0.7545 to over 0.9739. Alternatively, a structurally integrated method was reported, where the deflection of a built-in cantilever beam was used to indirectly quantify the preload [35]. This setup revealed that the preload governs the stepping mode and actively tunes the system’s resonant frequency from 625.6 Hz to 770.6 Hz. The optimized maximum speed could reach 18.37 mm/s, which expands the stable operational bandwidth. Furthermore, through the coordinated actuation of dual PZT stacks, dynamic preload regulation was accomplished within a composite flexible hinge design [107]. This method successfully mitigates inherent backward motion while enhancing the actuator’s load capacity.

5.3. Dynamic Analysis

The accurate dynamic modeling of stick-slip actuators is essential for understanding and mitigating performance-limiting factors such as bidirectional step inconsistency, which directly impact positioning accuracy and repeatability. Recent research has highlighted that this inconsistency stems not merely from friction but critically from the transient contact–separation dynamics between the driving foot and slider. Precise motion state prediction and optimization can be achieved by incorporating these contact behaviors into a comprehensive dynamical framework, which can guide the parameter design of the stick-slip actuator.

Existing dynamic models have advanced beyond modeling basic friction to now representing the intricate multi-physics interactions within the actuator assembly. This progression enables markedly improved predictability in design and more effective performance tuning. For instance, the prevalent issue of bidirectional step inconsistency was tackled by integrating the contact dynamics between the PZT stack and its flexure-based preload mechanism into a comprehensive framework [108]. During the analysis, a distributed-parameter representation was combined with Bouc-Wen hysteresis, Hunt-Crossley contact, and LuGre friction models. This approach successfully explained and reduced the forward–backward step size discrepancy by 33.43%. In a study utilizing the parasitic motion principle, a dynamic model was developed that incorporates the coupling angle and the elastic contact at the driving interface within a lumped-parameter framework [109]. This model facilitates a parametric trade-off analysis between velocity and load capacity by accurately predicting metrics like the backlash ratio. Expanding the scope of the system analysis further, the stiffness and damping of the actuator’s overall support structure was introduced into dynamical equations to account for its non-rigid body deformation [110]. This method enables the successful simulation of three distinct single-step motion modes, including backward motion, smooth motion, and sudden jump, which improves the predictive accuracy for step characteristics and provides vital guidance for application-specific design.

Based on the survey in Section 5, the transition toward deterministic motion control through single-step analysis, active preload regulation, and multi-physics dynamic modeling enables the systematic suppression of backward motion and cumulative errors. While active regulation is effective for enhancing linearity and load capacity in long-stroke operations, predictive dynamic modeling provides essential guidance for mitigating bidirectional inconsistencies and optimizing high-speed trajectory tracking.

5.4. Influence of Piezoelectric Materials

While the structural topology governs the mechanical advantage, the intrinsic properties of the functional ceramic define the ultimate performance ceiling of stick-slip actuators, as summarized in

Table 5. Comparison between different kinds of PZT units.

Property	Soft PZT (PZT-5A/5H)	Hard PZT (PZT-4/PZT-8)	Impact on Stick-Slip
Piezoelectric Constant	High (>500 pC/N)	Low (<300 pC/N)	Affects maximum step size
Dielectric Loss	High (1.5–2.0%)	Low (<0.5%)	Affects high-frequency stability
Mechanical Quality Factor	Low (<100)	High (>1000)	Affects resonance and heat
Hysteresis	Large	Small	Affects open-loop accuracy

. Most modern actuators utilize Lead Zirconate Titanate due to its high electromechanical coupling. However, a critical trade-off exists between ‘soft’ (e.g., PZT-5H) and ‘hard’ (e.g., PZT-8) ceramics. Soft PZT units possess higher constants, facilitating larger step sizes and higher displacement sensitivity, but they are prone to significant hysteresis and non-linearity, which complicate open-loop control in stick-slip motion. Conversely, hard PZT units exhibit lower dielectric loss and superior mechanical quality factors, making them more suitable for the high-frequency excitation typical of rapid stick-slip stepping, as they minimize self-heating and thermal depolarization. Furthermore, in extreme environments such as vacuum or cryogenic stages, the temperature dependence of the piezoelectric coefficient and the Curie temperature become limiting factors for maintaining stable frictional contact.

6. Challenges and Prospective Directions

6.1. Challenges

The advancement of piezoelectric stick-slip actuators is currently limited by the intricate interplay between interfacial tribology and high-frequency electromechanical dynamics. The inherent nonlinearity of friction—manifested as rate-dependent stick-slip transitions and surface-induced wear—leads to motion instability and diminished long-term reliability. This is further compounded by parasitic backward motion and unwanted vibration coupling, which arise from the inertial lag of the mover during the rapid contraction phase of the PZT. Furthermore, the persistent trade-off between high-load capacity and low backward motion, alongside the challenges of modeling complex hysteresis and creep, necessitates the development of sophisticated decoupled compliant mechanisms and adaptive control strategies. Consequently, bridging the gap between theoretical precision and robust industrial performance is still a key challenge for improving the performance of stick-slip actuators.

6.2. Prospective Directions

Stick-slip actuators have attracted considerable attention due to their simple structure, high resolution, and theoretically unlimited travel range. However, their widespread application in advanced micromanipulation and precision machining is hindered by several intrinsic limitations. To address these existing challenges, this section outlines some necessary future research directions.

(1) The driving force and load capacity of stick-slip actuators can be enhanced by optimizing the actuation mechanism and material properties. The output force of current designs is usually no more than 10 newtons, which restricts their application in scenarios requiring substantial load handling. Efforts may include developing novel PZT and electromagnetic hybrid actuation principles, where the contact force between the driving foot and slider can be actively adjusted by controlling the electromagnetic force. Additionally, investigations into surface texture and friction, layer engineering could also be conducted to improve the driving force.

(2) Although much effort has been dedicated to solving the issue of reverse motion, it still exists and remains a major source of positioning error and reduced efficiency in stick-slip actuators. Future studies should aim to develop comprehensive models that accurately predict backward motion based on driving waveform, contact dynamics, and system damping. The integration of auxiliary braking mechanisms can also be employed. Furthermore, employing feedback-controlled clamping elements could minimize or eliminate backward motion, which can improve the overall motion accuracy and load capacity.

(3) Improving the dynamic response and long-term stability is essential for high-speed and high-precision applications. Developing robust compensation algorithms is necessary to enhance actuating stability. Optimizing structural design and improving bandwidth should also be focused on in future works. In addition, by implementing real-time system identification and adaptive tuning, the performance consistency under varying loads or conditions can be maintained.

(4) The long-term reliability and lifespan of stick-slip actuators are critical for practical deployment. Future investigations should pay attention to analyzing failure mechanisms, such as the wear of the friction pair, fatigue, and degradation of mechanical components. Research on durable interface materials, wear-resistant coatings, and low-degradation PZT should be conducted.

7. Conclusions

This review comprehensively examines the development of large-stroke, high-precision, non-resonant stick-slip actuators. It delineates the fundamental actuation mechanisms, including conventional, parasitic, and hybrid. The core of recent advancements lies in sophisticated structural innovations, including CAMs and bio-inspired designs, which have significantly improved the performance of both linear and rotational actuators by mitigating backward motion, enhancing load capacity, and ensuring stepping consistency. Furthermore, substantial progress in motion precision has been achieved through quantitative step optimization, active preload control, and advanced dynamic modeling that integrates friction, contact, and hysteresis phenomena. However, increasing driving frequencies to enhance velocity inevitably exacerbates frictional heat accumulation and interfacial degradation. In the future, hybrid actuation schemes, advanced interface materials, high-fidelity multi-physics models, and adaptive control algorithms can be further studied to fully realize their potential in next-generation precision positioning systems. Additionally, the integration of physics-informed neural networks for sensorless motion estimation offers a promising avenue to bypass the physical constraints of sensors.