Parasitic Motion Principle Research Articles

A piezo-actuated nanopositioning stage based on spatial parasitic motion principle

This paper presents the configuration, design, and characteristic analysis of a novel two-degree-of-freedom stick-slip nanopositioning stage based on the spatial parasitic motion principle. The planar-spatial evolution process is proposed to develop a compliant tripod mechanism by which the spatial parasitic motion can be generated for dual-axis actuation. An X-shaped hinge configuration is designed by freedom and constraint space analysis and introduced to the mechanism to improve the loading capacity of the nanopositioning stage. The actuation principle for driving along X- and Y-directions forward and backward is provided. The chain-based compliance matrix method is adopted for kinematic and static modeling of the compliant tripod mechanism. The dominant parameters are determined based on sensitivity analysis, and the performance of the stage is further studied by finite element method. The nanopositioning stage prototype is fabricated and assembled, and experimental investigations are conducted. The proposed nanopositioning stage has maximum velocities of 0.77 mm/s and 1.03 mm/s along X- and Y-direction, and a loading capacity of 5 kg can be achieved. Furthermore, the coarse-fine positioning experiments are carried out, and the positioning resolution is measured to be 18 nm.

A new symmetrical Z-shaped compliant linear actuator based on parasitic motion principle

To meet the demand of designing piezoelectric actuators with long working stroke and high resolution, a new parasitic motion principle (PMP) linear actuator based on the symmetrical Z-shaped compliant mechanism was proposed in this paper. The mechanism design and the operation principle of the proposed linear actuator were elaborated. The theoretical model of the symmetrical Z shaped compliant mechanism deformation was established, and was verified by the simulation analysis. Experimental studies were conducted on a manufactured prototype to investigate the performances of the proposed linear actuator. The results indicate that a linear actuator with bi-directional motion can be achieved, which has a resolution of 106 nm in the forward direction and 84 nm in the reverse direction. Under the locking force of 0.8 N, the maximum speed of 270 µm s−1 was reached, when the amplitude and the frequency of the driving voltage were set to 60 V and 650 Hz. It is also noted that the proposed linear actuator can work with a loading capacity of 25 g. This study has provided an alternative way for the development of a PMP linear actuator with bi-directional motion.

Analysis and comparison of flexible mechanisms for parasitic motion principle piezoelectric actuator

This paper compares three flexible mechanisms in parasitic motion principle piezoelectric actuator through analytic calculation and experiment investigation. The flexible mechanism used in piezoelectric actuator can be classified into functional shape type and asymmetrical stiffness type. For comparing the benefits of these two types of flexible mechanisms and their hybrid structure, the relation between the force and displacement of three flexible mechanisms are deduced using matrix-based compliance modeling method. Also, the dynamic model of parasitic motion principle piezoelectric actuator is used to explore the influence of dimension of flexible mechanism. After that, a prototype and above-mentioned three flexible mechanisms are manufactured and tested, and the motion characteristics of prototype with different flexible mechanisms are investigated, including the step length, velocity and load capacity under different driving voltage and driving frequency. Based on experiment results, the advantages of three flexible mechanisms are analyzed, the hybrid flexible mechanism can achieve fast velocity at medium driving frequency, but asymmetrical stiffness flexible mechanism shows greater motion efficiency and better performance under high driving frequency.

Development and analysis of a dynamic model for parasitic motion principle piezoelectric actuator

The main goal of this paper is studying characteristics of the parasitic motion principle (PMP) piezoelectric actuator and providing a dynamic model for possible control and optimization in future. Through analyzing motion principle of the PMP piezoelectric actuator and considering elastic deformation between the mover and the flexible mechanism, this paper first presents a dynamic model which is verified to be feasible through fitting experiment data. Then the model is used to analyze influence of the coupling angle, the driving signal symmetry, the mover mass and the preload force on performance of the PMP piezoelectric actuator, including the step length, the backlash ratio and the maximum output force. This research contributes to enhance the understanding of the PMP and provide a guidance for design of the PMP piezoelectric actuators.

Development and analysis of a stick-slip rotary piezoelectric positioner achieving high velocity with compact structure

A high-velocity rotary stick-slip piezoelectric positioner working in non-resonant condition driven by piezo-stacks is proposed in this paper. For improving working performance through the parasitic motion principle, a compact flexible mechanism with rotational symmetric structure is designed. Its special structure can realize self-centering function, thus there is no need to adopt a bearing for the rotor. And in order to reduce the amounts of needed piezo-stacks and achieve synchronous action of four driving feet, a connecting ring is designed to connect four driving feet. A prototype is manufactured and corresponding experiments are carried out, experimental results show the proposed positioner has a good working performance. Its maximum velocity reaches 151.4 mrad/s, which is greater than most existing non-resonant stick-slip piezoelectric positioners driven by piezo-stacks. And a dynamic model is established and calculated in MATLAB/Simulink, a series of simulation are carried out to further investigate influential factors of the proposed positioner.

A linear piezoelectric actuator with high flexibility flexible mechanism designed by the bidirectional parasitic motion principle.

This paper proposes a piezoelectric actuator based on the parasitic motion principle which overcomes the disadvantage that piezoelectric actuators designed by the parasitic motion principle always sacrifice reverse directional performance for improving forward directional performance. The parasitic motion principle based piezoelectric actuator can use two flexible mechanisms to achieve bidirectional motion, but more assembly errors will be introduced. Therefore, the proposed actuator is designed to output bidirectional motion through one flexible mechanism. To this end, two mounting slots with high flexibility are specially designed for improving output displacement. The working principle and design process are elaborated, and experiments are conducted to prove the feasibility of the proposed actuator. The fabricated prototype can achieve a maximum velocity of 1.563 mm/s and 1.054 mm/s, a displacement resolution of 5.8 µm and 6 µm, an operating bandwidth of 1600 Hz and 1200 Hz, and a vertical load capacity larger than 500 g in forward and reverse directions.

Structure dependence of the output performances of a self-deformation driving (SDD) piezoelectric actuator

Pre-loading the driving compliant mechanism is an effective method to improve the self-locking ability of the parasitic motion principle (PMP) piezoelectric actuators, but it may also change the motion mode from the normal PMP to the self-deformation driving (SDD). When the self-deformation is distributed along the whole driving compliant mechanism, the structure design and analysis would be difficult. To facilitate the design and analysis of SDD piezoelectric actuators, following our previous study, an additional flexible hinge was introduced to the lever-amplification compliant mechanism, and thus the self-deformation would be concentrated in the introduced flexible hinge. The maximum one-step displacement of the proposed SDD piezoelectric actuator was analyzed by pseudo-rigid-body method, and the effects of the radius of the introduced right-circular flexible hinge on its compliance were theoretically analyzed. Output performances of the SDD actuator under various radiuses were characterized by experiments. The results showed that the introduced flexible hinge could not only increase the peak motion speed but also increase the adjustable initial gap, i.e. reducing the assembly requirements. Furthermore, when reducing the initial gap to be over the one corresponding to the peak motion speed, the backward motion would become remarkable; however, it would also bring an important advantage, improving the self-locking ability (also the loading capability). These results are expected to provide useful information for the design and application of SDD piezoelectric actuators.

Active suppression of the backward motion in a parasitic motion principle (PMP) piezoelectric actuator

In the piezoelectric driving field, backward motion commonly exists in output displacement curves of the actuators designed by various driving principles, which deteriorates the output performances and increases difficulty in subsequent control. To suppress the backward motion, a synergic motion principle (SMP) was proposed in this paper, which employed two piezoelectric stacks (PESs), one for driving and the other for lifting. By synergic driving of these two PESs, the contact force during the driving process could be effectively controlled and thus the backward motion could be actively suppressed. To verify the feasibility, an actuator prototype was designed and fabricated, and an experimental system was established to test its output performances. By theoretical analysis and experiments, the relationship of the driving voltages for these two PESs was determined. Under the optimized experimental conditions, it showed that the actuator could output stepping displacement without backward motion when working under the SMP. By comparing the results with those obtained when the actuator worked under the parasitic motion principle (PMP), the feasibility and validity of the proposed SMP for suppressing the backward motion were further confirmed.

Design, analysis and experiments of a linear piezoelectric actuator adopting a flexible mechanism with wing skeletal structure

This paper proposes a linear piezoelectric actuator with a flexible mechanism with wing skeletal structure. Besides the compact structure, high location precision and easy control, the main innovation point is that through the flexible mechanism with wing skeletal structure, the proposed actuator solves the problem that existing piezoelectric actuators based on parasitic motion principle must sacrifice motion performance in one direction for improving that in the opposite direction. The design process and operation principle of the proposed actuator is elaborated. And finite element analysis software ABAQUS and mathematical software MATLAB/SIMULINK are used to carry out static and dynamic analysis of the flexible mechanism. Last, a series of experiments are carried out and the results prove the proposed actuator can achieve desired function and show a favorable prospect to develop further.

A new motion mode of a parasitic motion principle (PMP) piezoelectric actuator by preloading the flexible hinge mechanism

For the purpose of increasing the self-locking ability of piezoelectric actuators designed by the parasitic motion principle (PMP), reducing the initial gap and applying a preloading force between the driving mechanism and the mover would be an effective method. By analyzing the contact and deformation status between the flexible hinge driving mechanism and the mover under an initial gap of zero, a new motion mode of PMP actuators was proposed, which would result in movement of the mover along an opposite direction to that under the normal PMP. To explore the transition from the normal PMP to the new motion mode, a piezoelectric actuator was designed by employing a flexible hinge mechanism with the lever-amplification structure. By measuring the output displacement of the mover under various initial gaps, the transition in motion mode was experimentally confirmed and analyzed. The new motion mode was readily activated when preloading the flexible hinge mechanism. The comparison in locking force proved that when the piezoelectric actuator worked under the new motion mode, its self-locking ability was greatly improved. Under the new motion mode, the effects of the initial gap, driving voltage, driving frequency, and vertical load on the output performances of the piezoelectric actuator were further studied. The results indicated that the new motion mode not only improved the self-locking ability of the PMP actuator, but also produced good output performances.

On the Suppression of the Backward Motion of a Piezo-Driven Precision Positioning Platform Designed by the Parasitic Motion Principle

Piezo-driven precision positioning platforms with large stroke are greatly demanded in both scientific research and industrial applications. Although various principles have been proposed to design piezo-driven positioning platforms, the problem of backward motion commonly exists, greatly hindering their applications. To suppress the backward motion, in this paper, an idea by generating a forward frictional force to balance the reversed frictional force was proposed. Correspondingly, a specific arc-shape flexure hinge was designed to generate the forward frictional force via its elastic recovery. To verify the feasibility of the proposed idea, a positioning platform with alterable initial gap between contact surfaces is designed by the parasitic motion principle (PMP). By measuring the output displacement under various initial gaps, a critical initial gap was identified, at which the positioning platform could output stepping displacement without backward motion. Under this critical initial gap, effects of driving voltage and frequency on the backward motion are further investigated. In addition, the natural frequency and loading capacity of the positioning platform are tested. This paper confirms that using PMP, it is feasible to design piezo-driven positioning platforms with completely suppressed backward motion, which would enhance the applications of the PMP and PMP positioning platforms.

Development of a Novel Parasitic-Type Piezoelectric Actuator

A piezoelectric actuator based on parasitic motion principle is proposed and tested. The piezoelectric actuator is explored to simultaneously realize coarse (long stroke) and fine (high accuracy) motions using dual-servo control method. The working principle of the proposed piezoelectric actuator is discussed, and finite-element method is adopted. A dynamic model of parasitic motion based on the LuGre friction model is simulated using matlab /Simulink. A prototype is manufactured to investigate working performance. Experimental results indicate that the maximum speed of the presented parasitic-type piezoelectric actuator is 7.95 mm/s and the resolution is 10 nm. These findings confirm the feasibility of the dual-servo nanopositioning system using piezoelectric stacks and flexure hinges.

On the correlation between the structure and one stepping characteristic of a piezo-driven rotary actuator

The parasitic motion principle was recently proposed to design piezo-driven actuators. Based on this principle, linear and rotary actuators with features of compact structure, large motion range, high velocity and high positioning resolution have been reported. However, some shortcomings such as the backward motion and the nonlinearity still exist and their causes are not clarified. To find potential reasons leading to these shortcomings, one stepping characteristic of a piezo-driven rotary actuator designed by the parasitic motion principle was investigated in this paper, and the correlation between the structure and one stepping characteristic was attempted to be established by theoretical analysis and simulations. Analysis results indicated that the nonlinearity in one stepping characteristic of the rotary actuator was correlated to the small gap between the inner and outer rings of the bearing as well as the self-deformation of the flexible gripper after the contact stiffness between the flexible gripper and the rotor reaches to the maximum value. The backward motion could be mainly resulted from the non-ideal driving wave. These analysis results enhance the understanding of the parasitic motion principle, which are meaningful for design and performance improvement of the parasitic motion principle linear or rotary actuators.

Forward and Reverse Movements of a Linear Positioning Stage Based on the Parasitic Motion Principle

A compact linear positioning stage using one microgripper and one piezoelectric stack is presented based on the parasitic motion principle. Characteristics of the linear positioning stage along the positive y-axis and the negative y-axis are measured and compared with each other. Experimental results indicate that the linear positioning stage has features of the large motion range, various movement velocities and stepping displacement, and forward and reverse movements. Meanwhile, the positioning stage has good resolution and enough load capacity. Possible reasons leading to nonlinearity and velocity difference between forward and reverse movements are discussed. Research results in this paper will make applications of the parasitic motion principle more flexible.

Note: A novel rotary actuator driven by only one piezoelectric actuator

This paper presents a novel piezo-driven rotary actuator based on the parasitic motion principle. Output performances of the rotary actuator were tested and discussed. Experiment results indicate that using only one piezoelectric actuator and simple sawtooth wave control, the rotary actuator reaches the rotation velocity of about 20,097 μrad/s when the driving voltage is 100 V and the driving frequency is 90 Hz. The actuator can rotate stably with the minimum resolution of 0.7 μrad. This paper verifies feasibility of the parasitic motion principle for applications of rotary actuators, providing new design ideas for precision piezoelectric rotary actuators.

Effect of residual chips on the material removal process of the bulk metallic glass studied by in situ scratch testing inside the scanning electron microscope

Research on material removal mechanism is meaningful for precision and ultra-precision manufacturing. In this paper, a novel scratch device was proposed by integrating the parasitic motion principle linear actuator. The device has a compact structure and it can be installed on the stage of the scanning electron microscope (SEM) to carry out in situ scratch testing. Effect of residual chips on the material removal process of the bulk metallic glass (BMG) was studied by in situ scratch testing inside the SEM. The whole removal process of the BMG during the scratch was captured in real time. Formation and growth of lamellar chips on the rake face of the Cube-Corner indenter were observed dynamically. Experimental results indicate that when lots of chips are accumulated on the rake face of the indenter and obstruct forward flow of materials, materials will flow laterally and downward to find new location and direction for formation of new chips. Due to similar material removal processes, in situ scratch testing is potential to be a powerful research tool for studying material removal mechanism of single point diamond turning, single grit grinding, mechanical polishing and grating fabrication.

A novel driving principle by means of the parasitic motion of the microgripper and its preliminary application in the design of the linear actuator

This paper presents a novel driving principle by means of the parasitic motion of the microgripper. Actuators based on this principle can realize the large displacement range and high speed easily. Also the structure can be simple. A parasitic motion principle linear actuator mainly consisting of two piezoelectric stacks, two microgrippers and a mover was designed. Experimental results indicate that at a low driving frequency of 5 Hz, large velocity over 40 μm/s is obtained with the driving voltage of 100 V. Backward motion was observed and analyzed. Experimental results verify the feasibility of the new principle and it can be used to design new linear or rotary actuators.