@article{23891,
  abstract     = {{Within a pre-post-design, we scrutinized the effects of normative augmented feedback with positive and negative valence on learning motor accuracy, consistency as well as automaticity by means of a dual-task paradigm. Forty-two healthy physical education students were instructed to produce an arm-movement sequence as precisely as possible with regard to three spatial reversal points within a time limit of 1200 ms. Twenty-eight practiced an elbow-extension-flexion-sequence (690 trials) and 14 participants were tested as a control group without feedback practice. Valence of normative feedback was systematically manipulated by means of reference lines in a visual feedback display. The reference lines indicated performance of a putative peer-group either to be superior (negative valence, Normative-Negative-Group) or inferior (positive valence, Normative-Positive-Group) to participants’ actual performance.

As a result, dual-task costs (n-back error) significantly decreased solely in the Normative-Positive-Group, p = .003, η2p = .51, but in no other group. Surprisingly, the mean absolute error for the motor task significantly decreased (i.e., precision increased) only in the Normative-Negative-Group with a large effect size, but in none of the other groups. Motor consistency was not significantly affected by the valence of normative feedback. According to the hypotheses of error-provoked attentional control, positive feedback-valence appears to enhance skill automatization, while – unexpectedly – only negative feedback-valence seems to enhance movement precision, which may be explained by effects of feedback valence on the learners aspiration level.}},
  author       = {{Zobe, Christina and Krause, Daniel and Blischke, Klaus}},
  journal      = {{Human Movement Science}},
  keywords     = {{Augmented feedback Automaticity Dual task Motor learning}},
  pages        = {{529--540}},
  publisher    = {{Elsevier}},
  title        = {{{Dissociative effects of normative feedback on motor automaticity and motor accuracy in learning an arm movement sequence}}},
  doi          = {{https://doi.org/10.1016/j.humov.2019.06.004}},
  volume       = {{66}},
  year         = {{2019}},
}

@article{9876,
  abstract     = {{Piezoelectric inertia motors use the inertia of a body to drive it by means of a friction contact in a series of small steps. It has been shown previously in theoretical investigations that higher velocities and smoother movements can be obtained if these steps do not contain phases of stiction (''stick-slip`` operation), but use sliding friction only (''slip-slip`` operation). One very promising driving option for such motors is the superposition of multiple sinusoidal signals or harmonics. In this contribution, the theoretical results are validated experimentally. In this context, a quick and reliable identification process for parameters describing the friction contact is proposed. Additionally, the force generation potential of inertia motors is investigated theoretically and experimentally. The experimental results confirm the theoretical result that for a given maximum frequency, a signal with a high fundamental frequency and consisting of two superposed sine waves leads to the highest velocity and the smoothest motion, while the maximum motor force is obtained with signals containing more harmonics. These results are of fundamental importance for the further development of high-velocity piezoelectric inertia motors.}},
  author       = {{Hunstig, Matthias and Hemsel, Tobias and Sextro, Walter}},
  issn         = {{0939-1533}},
  journal      = {{Archive of Applied Mechanics}},
  keywords     = {{Inertia motor, High velocity, Stick-slip motor, Slip-slip operation, Friction parameter identification}},
  pages        = {{1--9}},
  publisher    = {{Springer Berlin Heidelberg}},
  title        = {{{High-velocity operation of piezoelectric inertia motors: experimental validation}}},
  doi          = {{10.1007/s00419-014-0940-0}},
  year         = {{2014}},
}

@inproceedings{9802,
  abstract     = {{It has been shown previously that ``slip-slip'' operation of piezoelectric inertia motors allows higher velocities and smoother movements than classic ``stick-slip'' operation. One very promising driving option is to use a superposition of multiple sinusoidal signals. In this contribution, previous theoretical results are validated experimentally. The results confirm the theoretical result that for a given maximum frequency, usually defined by the actuator characteristics, a signal with high fundamental frequency and consisting of two superposed sine waves leads to the highest velocity and the smoothest motion. This result is of fundamental importance for the further development of high-velocity piezoelectric inertia motors.}},
  author       = {{Hunstig, Matthias and Hemsel, Tobias and Sextro, Walter}},
  booktitle    = {{Proceedings of 10th International Workshop on Piezoelectric Materials and Applications and 8th Energy Harvesting Workshop}},
  keywords     = {{Piezoelectric inertia motor, stick-slip motor, driving signal, velocity, smoothness}},
  pages        = {{16--18}},
  title        = {{{High-Velocity Slip-Slip Operation of Piezoelectric Inertia Motors - Experimental Validation}}},
  year         = {{2013}},
}

@article{9803,
  abstract     = {{Piezoelectric inertia motors, also known as stickslip drives or (smooth) impact drives, use the inertia of a body to drive it by a friction contact in small steps, in the majority of motors composed of a stick phase and a slip phase between the friction partners. For optimizing inertia motors, it is important to understand the friction contact correctly and to measure its properties appropriately. This contribution presents experimental set-ups for measuring the contact force, friction force and relative displacement in an actual inertia motor with a dry friction contact and numerical simulations of the motor operation. The motor uses a pre-stressed multilayer actuator with a displacement in the range of 20 $\mu$ m. It is shown that a previously postulated condition for the applicability of simple kinetic friction models is well fulfilled for the investigated motor. The friction contact in the motor is simulated using different kinetic friction models. The input for the friction models is the measured motion of the rod. The models qualitatively reproduce the measured motion but show quantitative deviations varying with frequency. These can be explained by vibrations of the driving rod that are experimentally investigated.}},
  author       = {{Hunstig, Matthias and Hemsel, Tobias and Sextro, Walter}},
  journal      = {{Journal of Intelligent Material Systems and Structures}},
  keywords     = {{Actuator, friction, motor, piezoelectric}},
  number       = {{11}},
  pages        = {{1380--1391}},
  title        = {{{Modelling the friction contact in an inertia motor}}},
  doi          = {{10.1177/1045389X12474354}},
  volume       = {{24}},
  year         = {{2013}},
}

@article{9804,
  abstract     = {{This contribution provides a systematic investigation and performance comparison of different modes of operation for piezoelectric inertia drives. The movement of these motors is classically assumed to consist of steps involving stiction and sliding, resulting in the term ``stick-slip drives''. In the first part of this contribution it has been found that using ideal driving signals, ``slip-slip'' operation without phases of stiction allows very high velocities, while the maximum velocity is limited principally in stick-slip operation. In this part it is shown that slip-slip operation is also suitable for use with real actuators, driven with frequency-limited versions of the ideal signals presented in part I. The motional performance of the motor as well as its wear and the required electric power are investigated for operation with different signals. It is found that for high velocity inertia motors it is recommendable to use actuators with large stroke and to drive them with a signal consisting of two harmonics at a high fundamental frequency, a result that is supported by similar setups implemented experimentally by other authors. Using Lanczos' \sigma factors to calculate the frequency-limited excitation signals instead of standard Fourier series additionally increases the motor performance significantly. The results help motor designers to choose the appropriate mode of operation and to optimise the motor parameters for their individual applications.}},
  author       = {{Hunstig, Matthias and Hemsel, Tobias and Sextro, Walter}},
  journal      = {{Sensors and Actuators A: Physical}},
  keywords     = {{Inertia motor}},
  pages        = {{79 -- 89}},
  title        = {{{Stick-slip and slip-slip operation of piezoelectric inertia drives - Part II: Frequency-limited excitation}}},
  doi          = {{10.1016/j.sna.2012.11.043}},
  volume       = {{200}},
  year         = {{2013}},
}

@article{9805,
  abstract     = {{Piezoelectric inertia motors, also known as ``stick--slip drives'', use the inertia of a body to drive it in small steps by means of a friction contact. While these steps are classically assumed to involve stiction and sliding, the motors can also operate in ``slip--slip'' mode without any phase of static friction. This contribution provides a systematic investigation and performance comparison of different stick--slip and slip--slip modes of operation. Different criteria for comparing the motional performance of inertia motors are defined: Steady state velocity, smoothness of motion, and start-up time. Using the example of a translational inertia motor excited by an ideal displacement signal, it is found that the maximum velocity reachable in stick--slip operation is limited principally, while continuous slip--slip operation allows very high velocities. For the investigated driving signals, the motor velocity is proportional to the square root of the actuator stroke. The motor performance with these ideal signals defines an upper boundary for the performance of real motors.}},
  author       = {{Hunstig, Matthias and Hemsel, Tobias and Sextro, Walter}},
  journal      = {{Sensors and Actuators A: Physical}},
  keywords     = {{Inertia motor, Stick--slip drive, Mode of operation, Performance indicator, Velocity maximization, Actuator stroke}},
  pages        = {{90 -- 100}},
  title        = {{{Stick-slip and slip-slip operation of piezoelectric inertia drives - Part I: Ideal Excitation.}}},
  doi          = {{10.1016/j.sna.2012.11.012}},
  volume       = {{200}},
  year         = {{2013}},
}

@inproceedings{9784,
  abstract     = {{Piezoelectric inertia motors use the inertia of a body to drive it by means of a friction contact in a series of small steps. These motors can operate in ``stick-slip'' or ``slip-slip'' mode, with the fundamental frequency of the driving signal ranging from several Hertz to more than 100 kHz. To predict the motor characteristics, a Coulomb friction model is sufficient in many cases, but numerical simulation requires microscopic time steps. This contribution proposes a much faster simulation technique using one evaluation per period of the excitation signal. The proposed technique produces results very close to those of timestep simulation for ultrasonics inertia motors and allows direct determination of the steady-state velocity of an inertia motor from the motion profile of the driving part. Thus it is a useful simulation technique which can be applied in both analysis and design of inertia motors, especially for parameter studies and optimisation.}},
  author       = {{Hunstig, Matthias and Hemsel, Tobias and Sextro, Walter}},
  booktitle    = {{Ultrasonics Symposium (IUS), 2012 IEEE International}},
  issn         = {{1948-5719}},
  keywords     = {{friction, ultrasonic motors, Coulomb friction model, efficient simulation technique, friction contact, high-frequency piezoelectric inertia motor, motor characteristics prediction, numerical simulation, slip-slip mode, stick-slip mode, time-step simulation, ultrasonic inertia motor, Acceleration, Acoustics, Actuators, Computational modeling, Friction, Numerical models, Steady-state}},
  pages        = {{277--280}},
  title        = {{{An efficient simulation technique for high-frequency piezoelectric inertia motors}}},
  doi          = {{10.1109/ULTSYM.2012.0068}},
  year         = {{2012}},
}

@article{9571,
  abstract     = {{Several positioning tasks demand translatory drive instead of rotary motion. To achieve drives that are capable, e.g., to drive the sunroof of a car or to lift a car's window, multiple miniaturized motors can be combined. But in this case many other questions arise: The electromechanical behavior of the individual motors differs slightly, the motor characteristics are strongly dependent on the driving parameters and the driven load, many applications need some extra power for special cases like overcoming higher forces periodically. Thus, the bundle of motors has to act well-organized and at last controlled to get an optimized drive that is not oversized and costly.}},
  author       = {{Mracek, Maik and Hemsel, Tobias and Sattel, Thomas and Vasiljev, Piotr and Wallaschek, Jörg}},
  issn         = {{1385-3449}},
  journal      = {{Journal of Electroceramics}},
  keywords     = {{Ultrasonic linear motor, High power, Control, Modeling, Characteristics}},
  number       = {{3-4}},
  pages        = {{153--158}},
  publisher    = {{Springer US}},
  title        = {{{Driving concepts for bundled ultrasonic linear motors}}},
  doi          = {{10.1007/s10832-007-9123-5}},
  volume       = {{20}},
  year         = {{2008}},
}

@article{9539,
  abstract     = {{Classically, rotary motors with gears and spindle mechanisms are used to achieve translatory motion. In means of miniaturization and weight reduction piezoelectric linear motors are of interest. Several ultrasonic linear motors found in literature base on the use of two different vibration modes. Most often flexural and longitudinal modes are combined to achieve an elliptic micro-motion of surface points. This micro-motion is converted to direct linear (or translatory) motion of a driven slider. To gain high amplitudes of the micro-motion and thus having a powerful motor, the ultrasonic vibrator should be driven near the eigenfrequency of its modes. Additionally, low mechanical and electrical losses lead to increased efficiency and large amplitude magnification in resonance. This demands a geometrical design that fits the eigenfrequencies of the two different modes. A frequency-deviation of only a few percent leads to non-acceptable disturbance of the elliptical motion. Thus, the mechanical design of the vibrators has to be done very carefully. Within this contribution we discuss different motor designs based on the coupling of two the same longitudinal vibrations within one structure to generate an elliptic motion of surface points. Different concepts based on piezoelectric plates and Langevin transducers are compared. Benefits and drawbacks against the combination of longitudinal and bending modes will be discussed. Numerical results of the stator vibration as well as motor characteristics are validated by measurements on different prototypes. }},
  author       = {{Hemsel, Tobias and Mracek, Maik and Twiefel, Jens and Vasiljev, Piotr}},
  issn         = {{0041-624X}},
  journal      = {{Ultrasonics}},
  keywords     = {{Piezoelectric linear motor}},
  pages        = {{e591 -- e596}},
  title        = {{{Piezoelectric linear motor concepts based on coupling of longitudinal vibrations}}},
  doi          = {{10.1016/j.ultras.2006.05.056}},
  volume       = {{44, Supplement}},
  year         = {{2006}},
}

@article{9546,
  abstract     = {{Rotary ultrasonic motors have found broad industrial application in camera lens drives and other systems. Linear ultrasonic motors in contrast have only found limited applications. The main reason for the limited range of application of these very attractive devices seems to be their small force and power range. Attempts to build linear ultrasonic motors for high forces and high power applications have not been truly successful yet. To achieve larger force and higher power, multiple miniaturized motors can be combined. This approach, however, is not as simple as it appears at first glance. The electromechanical behaviour of the individual motors differs slightly due to manufacturing and assembly tolerances. The individual motor characteristics are strongly dependent on the driving parameters (frequency, voltage, temperature, pre-stress, etc.) and the driven load and the collective behaviour of the swarm of motors is not just the linear superposition of the individual drive's forces. Thus, the bundle of motors has to be synchronized and controlled appropriately in order to obtain an optimized drive that is not oversized and costly. We have investigated driving and control strategies of a set of linear ultrasonic motors. Our contribution will be divided into three main parts. In part I ultrasonic linear motors will be introduced. In part II driving strategies for a single motor as well as for a bundle of motors will be presented. These concepts will be verified by simulation results and experimental data. In part III a simplified model for the motor's electromechanical behaviour will be given.}},
  author       = {{Mracek, Maik and Hemsel, Tobias}},
  issn         = {{0041-624X}},
  journal      = {{Ultrasonics}},
  keywords     = {{Ultrasonic linear motor}},
  pages        = {{e597 -- e602}},
  title        = {{{Synergetic driving concepts for bundled miniature ultrasonic linear motors}}},
  doi          = {{10.1016/j.ultras.2006.05.201}},
  volume       = {{44, Supplement}},
  year         = {{2006}},
}

@article{6065,
  abstract     = {{In the direct parameter specification (DPS) mode of sensorimotor control, response parameters can be specified by stimuli that are not consciously perceived [Psychological Research/Psychologische Forschung 52 (1990) 207]. DPS is contingent on the current intentions. The invisible stimuli can be processed for the purposes of sensorimotor control only if they match the actual intentions, for example, share task-relevant features. The present experiments explore whether attentional capture by masked abrupt-onset stimuli is mediated via DPS. Participants judged which of two visual targets appeared first. Masked primes preceded one of the targets. The primes were either similar to the targets or not, in shape, or in color. Target-like (task-relevant), but not distractor-like (task-irrelevant), primes facilitated perceptual latencies of targets trailing at their positions. Thus, the latency effects resulted from DPS of an attention shift, rather than from bottom-up capture or from top-down }},
  author       = {{Scharlau, Ingrid and Ansorge, Ulrich}},
  issn         = {{0042-6989}},
  journal      = {{Vision Research}},
  keywords     = {{direct parameter specification, DPS, attention shift, latency priming, sensorimotor control, stimuli, task-relevant features, visual targets, color, shape, latency effects, Adult, Attention, Discrimination (Psychology), Female, Humans, Judgment, Male, Perceptual Masking, Reaction Time, Visual Perception, Attention, Perceptual Motor Processes, Response Latency, Stimulus Onset, Visual Stimulation, Form and Shape Perception, Sensory Adaptation}},
  number       = {{12}},
  pages        = {{1351 -- 1363}},
  title        = {{{Direct parameter specification of an attention shift: Evidence from perceptual latency priming.}}},
  volume       = {{43}},
  year         = {{2003}},
}

@article{8914,
  abstract     = {{Piezoelectric ultrasonic motors have been investigated for several years and have already found their first practical applications. Their key feature is that they are able to produce a high thrust force related to their volume. Beside rotary drives like the travelling wave motor, linear drives have also been developed, but only a few are presently commercially available. In the present paper, we first describe the state of the art of linear piezoelectric motors. The motors are characterized with respect to their no-load velocity, maximum thrust force, efficiency and other technical properties. In the second part, we present a new motor, which is judged to be capable of surpassing the characteristics of other piezoelectric motors because of its unique design which allows the piezoelectric drive elements to be pre-stressed in the direction of their polarization. The piezoelectric elements convert energy using the longitudinal d33 effect which allows an improved reliability, large vibration amplitudes and excellent piezoelectric coupling. Energy loss by vibration damping is minimized, and the efficiency can be improved significantly. Experimental results show that the motor characteristics can be optimized for a particular task by choosing the appropriate operating parameters such as exciting voltage, exciting frequency and normal force. }},
  author       = {{Hemsel, Tobias and Wallaschek, Jörg}},
  issn         = {{0041-624X}},
  journal      = {{Ultrasonics}},
  keywords     = {{Linear motor}},
  pages        = {{37 -- 40}},
  title        = {{{Survey of the present state of the art of piezoelectric linear motors}}},
  doi          = {{10.1016/S0041-624X(99)00143-2}},
  volume       = {{38}},
  year         = {{2000}},
}

@inproceedings{8915,
  abstract     = {{Ultrasonic linear motors have now been investigated for several years. Their key features are high thrust forces related to their volume and good position-accuracy. This contribution consists of two main parts. In the first part we describe the state-of-the-art of linear piezoelectric motors. Characteristics like no-load velocity, maximum thrust force and other technical properties of commercially available devices will be reported as well as those of prototypes. In the second part we report an ongoing research and development project aiming at a linear piezoelectric motor, which is capable of surpassing some of the shortcomings of other piezoelectric motors}},
  author       = {{Hemsel, Tobias and Wallaschek, Jörg}},
  booktitle    = {{Ultrasonics Symposium, 2000 IEEE}},
  issn         = {{1051-0117}},
  keywords     = {{linear motors, ultrasonic motors, linear piezoelectric motor, maximum thrust force, no-load velocity, ultrasonic linear motor, Electromagnetic devices, Electromagnetic fields, Frequency, Friction, Gears, Materials science and technology, Piezoelectric materials, Research and development, Vibrations, Wheels}},
  pages        = {{663--666 vol.1}},
  title        = {{{State of the art and development trends of ultrasonic linear motors}}},
  doi          = {{10.1109/ULTSYM.2000.922635}},
  volume       = {{1}},
  year         = {{2000}},
}