Inchworm Motor Research Articles

A Novel Four legged linear piezoelectric inchworm motor with high thrust force

A Novel Four legged linear piezoelectric inchworm motor with high thrust force

Correction to “On learning‐based approaches in power electronics engineering curriculum: A high switching inchworm motor drive case study”

Correction to “On learning‐based approaches in power electronics engineering curriculum: A high switching inchworm motor drive case study”

A compact, friction self-matching, non-inertial piezo motor with scanning capability

Maintaining friction matching is the core issue for non-inertial piezo motors (PMs); this challenge severely limits their application in complex conditions such as variable temperature environments. To address this issue, a compact, optimal friction self-matching PM with non-inertial driving is reported in this paper. The motor is implemented with a narrow 5.5 mm-outer diameter piezoelectric scanner tube (PST) whose outer electrode is equally divided into two independently controllable PSTs. The PST, divided into two parts, clamps a sapphire rod between dual sapphire ball structures at both ends and an elastically supported sapphire ball at the centre. The device features a balanced normal force distribution scheme that allows friction forces acting on the sapphire rod at both ends and on the intermediate section to be approximately equal along the axial direction of the PST, achieving automatic optimal matching of friction, then it can operate like an inchworm motor. The feasibility of this scheme is verified by testing with a low threshold voltage down to 35 V at room temperature and 160 V at liquid nitrogen temperature. The motor dimensions are 5.5 mm × 5.5 mm ×35 mm (length × width × height). At room temperature, step size ranges from 0.1 μm to 1 μm. It has a maximum stroke about 5 mm and a maximum load of 40 g. This PM’s extreme compactness, low machine tolerance requirements, and smooth sequence make it ideally suited for building superior quality, atomically resolved scanning probe microscopy devices compatible with narrow spaces and extreme conditions.

Inchworm Motors and Beyond: A Review on Cooperative Electrostatic Actuator Systems

Having benefited from technological developments, such as surface micromachining, high-aspect-ratio silicon micromachining and ongoing miniaturization in complementary metal–oxide–semiconductor (CMOS) technology, some electrostatic actuators became widely used in large-volume products today. However, due to reliability-related issues and inherent limitations, such as the pull-in instability and extremely small stroke and force, commercial electrostatic actuators are limited to basic implementations and the micro range, and thus cannot be employed in more intricate systems or scaled up to the macro range (mm stroke and N force). To overcome these limitations, cooperative electrostatic actuator systems have been researched by many groups in recent years. After defining the scope and three different levels of cooperation, this review provides an overview of examples of weak, medium and advanced cooperative architectures. As a specific class, hybrid cooperative architectures are presented, in which besides electrostatic actuation, another actuation principle is used. Inchworm motors—belonging to the advanced cooperative architectures—can provide, in principle, the link from the micro to the macro range. As a result of this outstanding potential, they are reviewed and analyzed here in more detail. However, despite promising research concepts and results, commercial applications are still missing. The acceptance of piezoelectric materials in some industrial CMOS facilities might now open the gate towards hybrid cooperative microactuators realized in high volumes in CMOS technology.

Design and experimental analysis of a high force piezoelectric linear motor

In this paper, the design and experimental analysis of a piezo-motor for applications requiring compact size, high blocking and driving forces are presented. Mechanical design addresses difficulties associated with high integration flexibility and high blocking force for the motor. The technology is inspired from a real inchworm motion and is based on Piezoelectric Actuators (PAs). The proposed Inchworm Motor (IM) consists of an extending mechanism (EM) and two doubled clamping mechanisms (CMs). Theoretically and by using Finite Element Analysis (FEA), the CM is designed in order to obtain high clamping forces between rotor and stator (2500N), while the EM is designed for large displacement (free stroke of 0.01mm) and high force (500N) using PAs. Practically and by using a preliminary low power supply (80V, 1Hz), the working principle of the motor is validated under testing conditions of 300N as a clamping force and 5N as a driving force. The fabricated IM achieves speed of 2.25μm/s. Experimental methods for verifying the theoretical force, calibrating the pre-stressing force and measuring the friction coefficient between the stator and the rotor are proposed. A motor with a weight of 78g and dimensions of 100mm×16mm×7mm ensures full clamping ability when not electrically activated.

Robotic multi-probe single-actuator inchworm neural microdrive.

A wide range of techniques in neuroscience involve placing individual probes at precise locations in the brain. However, large-scale measurement and manipulation of the brain using such methods have been severely limited by the inability to miniaturize systems for probe positioning. Here, we present a fundamentally new, remote-controlled micropositioning approach composed of novel phase-change material-filled resistive heater micro-grippers arranged in an inchworm motor configuration. The microscopic dimensions, stability, gentle gripping action, individual electronic control, and high packing density of the grippers allow micrometer-precision independent positioning of many arbitrarily shaped probes using a single piezo actuator. This multi-probe single-actuator design significantly reduces the size and weight and allows for potential automation of microdrives. We demonstrate accurate placement of multiple electrodes into the rat hippocampus in vivo in acute and chronic preparations. Our robotic microdrive technology should therefore enable the scaling up of many types of multi-probe applications in neuroscience and other fields.

Design and experimental evaluation of an inchworm motor driven by bender-type piezoelectric actuators

Piezoelectric actuators (PEAs) are widely used in ultra-precision detection platforms where nano-precision and non-magnetic features are required. With the development of the semiconductor industry, actuators develop toward the tendency of smaller size, higher precision, and longer travel. However, these demands are difficult to meet merely by virtue of a single piezoelectric actuator or a simple structured inchworm piezo motor, which makes it necessary to develop a new drive mode following a different drive principle. In this paper, a novel inchworm piezo motor with bender-type PEAs in phalanx distribution was proposed, which facilitates in reducing the dimension of the motor and enhances the performance and stability of the piezo motor. For the purpose of accommodating the bender-type PEAs and providing the preloads to the bender-type PEAs, a flexible mechanism housing was designed and the modal analysis was finished, avoid resonance and reduce structural vibration. Experimental results show that the resolution of the developed motor is 2 nm or less under the laser interference with an adoption rate of 10 MHz and a resolution of 0.1 nm, while the maximum stroke is over 19 mm at the constant speed of 2.3 mm s−1, and the maximum output force is 41.6 N.

Light-Driven Linear Inchworm Motor Based on Liquid Crystal Elastomer Actuators Fabricated with Rubbing Overwriting.

Linear displacement is used for positioning and scanning, e.g., in robotics at different scales or in scientific instrumentation. Most linear motors are either powered by rotary drives or are driven directly by pressure, electromagnetic forces or a shape change in a medium, such as piezoelectrics or shape-memory materials. Here, we present a centimeter-scale light-powered linear inchworm motor, driven by two liquid crystal elastomer (LCE) accordion-like actuators. The rubbing overwriting technique was used to fabricate the LCE actuators, made of elastomer film with patterned alignment. In the linear motor, a scanned green laser beam induces a sequence of travelling deformations in a pair of actuators that move a gripper, which couples to a shaft via friction moving it with an average speed in the order of millimeters per second. The prototype linear motor demonstrates how LCE light-driven actuators with a limited stroke can be used to drive more complex mechanisms, where large displacements can be achieved, defined only by the technical constrains (the shaft length in our case), and not by the limited strain of the material. Inchworm motors driven by LCE actuators may be scaled down to sub-millimeter size and can be used in applications where remote control and power supply with light, either delivered in free space beams or via fibers, is an advantage.

Investigation of the Dynamics of a 2-DoF Actuation Unit Cell for a Cooperative Electrostatic Actuation System

The mechanism of the inchworm motor, which overcomes the intrinsic displacement and force limitations of MEMS electrostatic actuators, has undergone constant development in the past few decades. In this work, the electrostatic actuation unit cell (AUC) that is designed to cooperate with many other counterparts in a novel concept of a modular-like cooperative actuator system is examined. First, the cooperative system is briefly discussed. A simplified analytical model of the AUC, which is a 2-Degree-of-Freedom (2-DoF) gap-closing actuator (GCA), is presented, taking into account the major source of dissipation in the system, the squeeze-film damping (SQFD). Then, the results of a series of coupled-field numerical simulation studies by the Finite Element Method (FEM) on parameterized models of the AUC are shown, whereby sensible comparisons with available analytical models from the literature are made. The numerical simulations that focused on the dynamic behavior of the AUC highlighted the substantial influence of the SQFD on the pull-in and pull-out times, and revealed how these performance characteristics are considerably determined by the structure’s height. It was found that the pull-out time is the critical parameter for the dynamic behavior of the AUC, and that a larger damping profile significantly shortens the actuator cycle time as a consequence.

Modeling of Motion Characteristics and Performance Analysis of an Ultra-Precision Piezoelectric Inchworm Motor.

Ultra-precision piezoelectric inchworm motor (PIM) is widely used in the optical equipment, microelectronics semiconductor industry and precision manufacturing for motion and positioning, but the multi-physics field simulation model for estimating PIM performance and assisting motor design is rarely studied. The simulation model in this paper aimed to provide researchers with direct and convenient PIM performance evaluation to assist the motor design and development. According to the existing advanced inchworm motor products, a multi-physics field coupling model involving solid mechanics and electrostatics using the finite element method (FEM) was established. The motion gesture and performance (driving force and travel) of the PIM were analyzed, respectively. The simulation results showed that the motion gesture of the inchworm motor was well consistent with that of the actual motor product. The driving force from the simulation was close to that of the actual product, and the maximum error was 2.8%. As for the PIM travel, there was a maximum travel error of 0.6 μm between the simulation and official data. The performance parameters of the piezoelectric materials under certain specifications can be simulated by the multi-physics field coupling model. Therefore, the multi-physics field coupling simulation model is suitable for PIM performance evaluation and assisting motor development.

On learning‐based approaches in power electronics engineering curriculum: A high switching inchworm motor drive case study

AbstractIn industrial electronics domain, power electronics students should have an optimum hardware competence. This study presents the application of computer‐aided design and experimental hands‐on exposure for efficient teaching of power electronics engineering curriculum. Application design of the proposed research centers around effective model of high switching frequency driver circuit for a capacitive piezoelectric inchworm motor based on learning techniques. The sample space comprise 50 undergraduate students, divided into two equal groups, Group A and Group B. Outcome validations testify the pivotal role of the designed course for the optimized piezoelectric driver hardware circuit design with near equivalent characteristics as obtained in simulation model. An evaluation survey was carried out to find if there is a change in attitude of students toward power electronics and allied subjects after attending the program. At the end of the course, opinion of the students were recorded and it was found that the attitude of the students who took the course differed significantly. The differentiation was in favor of the group having undertaken the course with a 91.5% positive response.

A stick-slip/inchworm hybrid rotary piezo motor based on a symmetric triangular driving mechanism

A stick-slip/inchworm hybrid rotary piezomotor based on a symmetric triangular driving mechanism, which can simultaneously achieve the benefits of both stick-slip and inchworm motors, was reported in this letter. It is based on the principle of stick-slip motors, and, inspired by the clamping-releasing actions from inchworm motors, it employs a symmetric triangular driving mechanism to generate a clamping action during the stick phase and a releasing action during the slip phase. Compared with stick-slip motors, it involves a clamping action during the stick phase and a releasing action during the slip phase, thus resulting in a larger driving force. Compared with inchworm motors, which require active control and coordination of clamping/releasing modules with feeding modules, it involves the control and operation of only one feeding piezoactuator without any actively controlled clamping/releasing module. Therefore, the control is easier, and a much larger operation frequency and driving speed can be achieved. Under the sawtooth waveform voltage of 90 V at 2600 Hz with a self-holding torque of 4 N m, the prototype achieved a no-load speed higher than 0.6 rad/s, a load torque capacity larger than 1.8 N m, and a weight carrying capacity more than 100 kg for both clockwise and anticlockwise directions. Compared with load torque capacity and weight carrying capacity in the reported stick-slip and inchworm rotary piezomotors, the current levels in terms of the same driving speed have been improved over 60 times and 12 times, respectively, in the proposed hybrid motor.

Dynamics of three unidirectionally coupled autonomous Duffing oscillators and application to inchworm piezoelectric motors: Effects of the coupling coefficient and delay.

This work deals with the dynamics of three unidirectionally coupled Duffing oscillators and that of three coupled piezoelectric actuators, considering the special case of inchworm motors. Two configurations of the network are studied: ring configuration and chain configuration. The effects of the coupling coefficient and the time delay are analyzed through different bifurcation diagrams and phase difference variation. It is shown that varying the coupling coefficient and the time delay leads to the appearance of different dynamical behaviors: steady states, periodic and quasiperiodic oscillations, chaos, and phase synchronization.

Bidirectional Resonant DC–DC Step-Up Converters for Driving High-Voltage Actuators in Mobile Microrobots

Electroactive polymer (EAP) actuators have been investigated to convert electrical energy into mechanical deformation in autonomous microrobots. The use of dielectric EAP actuators comes with several challenges to address requirements such as high excitation voltages, explicit driving signals, and low conversion efficiency. External bulky and heavy power sources are used to generate and provide required excitation voltages. The development of a miniature, high voltage gain, and highly efficient power electronic interface is required to overcome such challenges and enable autonomous operation of miniature robots. In this paper, a bidirectional single-stage resonant dc–dc step-up converter is introduced and developed to efficiently drive high-voltage EAP actuators in mobile microrobots. The converter utilizes resonant capacitors and a coupled inductor as a soft-switched LC network to step up low input voltage. High-frequency soft-switching operation owing to LC resonance allows small footprint of the circuit without suffering from switching losses, which in turn increases the efficiency. The circuit is capable of generating explicit high-voltage actuation signals, with capability of recovering unused energy from EAP actuators. A 4-mm × 8-mm, 100-mg, and 600-mW prototype has been designed and fabricated to drive an in-plane gap-closing electrostatic inchworm motor. Experimental validations have been carried out to verify the circuit's ability to step up voltage from 2 to 100 V and generate two 1-kHz, 100-V driving voltages at 2-nF capacitive loads.

箝位体刚度平衡对被动箝位压电驱动器性能的影响

箝位体刚度平衡对被动箝位压电驱动器性能的影响

An Ultracompact Dual-Stage Converter for Driving Electrostatic Actuators in Mobile Microrobots

Electrostatic actuators are being widely investigated to convert electrical energy into mechanical deformation in a broad variety of microrobotic applications. Both electrostatic gap closing and comb drive actuators require high excitation voltages for high performance operation. In the majority of applications, external bulky and heavy power supplies are used to provide such high voltages, which inevitably bring limitations on autonomous operation. One of the major challenges toward enabling operation of these systems without a bulky external power source is the development of ultralight and high power density power electronic interfaces (PEIs) with large step-up gains. In this paper, a special circuit topology, controlled by a pulse frequency modulation scheme, is introduced to meet stringent electrical and drive voltage requirements of electrostatic actuators. An ultracompact 63 mg (excluding PCB mass), 31.5 mm 2, and 500 mW PEI has been designed and fabricated. Experimental validations have been carried out to verify the circuit's ability to drive an 110-V-input electrostatic inchworm motor at 1-kHz actuating frequency.

Piezoelectric motor based on synchronized switching control

A novel working principle for piezoelectric motors aimed at high force, speed, and efficiency, as well as long service life is proposed in this paper. The principle is based on the synchronized switching control of harmonic vibration, which is derived from a classical electronic device called silicon controlled rectifier. Unlike the sliding friction coupling mechanism of ultrasonic motors and the quasi-static operation strategies of inchworm and impact motors, the new motor overcomes certain critical disadvantages of traditional piezoelectric motors. A linear piezoelectric motor was designed, fabricated and tested. The prototype reached a maximum speed of 8.2mm/s with a load of 0.5N, and its maximum load capacity reached up to 5N. The motor achieved a net efficiency of 18.5% with a load of 2N.

Optimized electrostatic inchworm motors using a flexible driving arm

ABSTRACTA new motor architecture that uses in-plane electrostatic gap-closing actuators along with a flexible driving arm mechanism to improve motor force density is introduced, optimized, manufactured, and tested. This motor operates similarly to other inchworm-based microactuators by accumulating small displacements from the actuators into much larger displacements in the motor. Using an analytical model of the inchworm motor based on the static force equilibrium condition, optimizations of a full motor design were performed to maximize motor force density. In addition, force losses from supporting flexures were included to calculate the theoretical motor efficiency for different motor designs. This force density optimization analysis of the gap-closing actuators and supporting motor structures provided the basis for designing and manufacturing inchworm motors with flexible driving arms and gap-closing actuators. The motor required only a single-mask fabrication and demonstrated robust performance, a maximum speed of 4.8 mm s−1, and a maximum force on the shuttle of 1.88 mN at 110 V which corresponds to area force density of 1.38 mN mm−2. In addition, instead of estimating motor force based on drawn or measured dimensions which often overestimates force, the demonstrated maximum motor force was measured using calibrated springs. The efficiency of the manufactured motor was measured at 8.75% using capacitance measurements and useful work output.

The Control System of a Distributed Aperture Imaging Testbed

Star-9 is an experimental demonstration of distributed-aperture imaging built at the Lockheed Martin Advanced Technology Center. White light from a scene generator enters an array of nine telescopes and is combined at a focused image plane. Relative aberrations from each telescope are regulated by a control system using phase diversity and active relay mirrors. A Weiner filter is applied to the image, and the resulting angular resolution and image quality are nearly diffraction-limited with the diameter of the array. The control system takes estimates from the phase diversity algorithm and uses them to command mirrors to adjust tip, tilt, and piston in each telescope. Each active mirror has inductive position sensors for local position control. The mirrors are actuated by picomotors and inchworm motors. In addition to tip/tilt/piston errors, the control system is equipped to correct for pupil geometry and rotation errors, and to perform field of regard steering. In this paper, we present details on the control system's local sensing, control law synthesis, and precision actuation methodology. We also describe the incorporation of phase diversity and automated phasing algorithms with the control system and give performance results.

Giant magnetostrictive clamping mechanism for heavy-load and precise positioning linear inchworm motors

This paper focuses on the development of a novel clamping principle and the mechanism that may be used to realize a linear motor capable of performing not only large thrust but also secure movement with high blocked clamping force. To verify this principle, a clamping prototype (size: ϕ32 × 130 mm) is constructed and tested. It generates a clamping force of 1050 N with an initial experimental set-up, and, a clamping force up to 1525 N with a modified set-up employing a hydro-press bench clamp. The theoretical and numerical analyses are carried out and suggest that the mechanism may generate a clamping force up to 2148 N with an adequate rigid guide-way.