How to use one surface electromyography sensor to recognize six hand movements for a mechanical hand in real time: a method based on Morse code.

Surface electromyography (sEMG) signal is a kind of physiological signal reflecting muscle activity and muscle force. At present, the existing methods of recognizing human motion intention need more than two sensors to recognize more than two kinds of movements, the sensor pasting positions are special, and the hardware conditions for execution are high. In this work, a real-time motion intention recognition method based on Morse code is proposed and applied to the mechanical hand. The short-time and long-term muscle contraction signals collected by a single sEMG sensor were extracted and encoded with the Morse code method, and then the developed mapping method from Morse code to six hand movements were used to recognize hand movements. The average recognition accuracy of hand movements was 94.8704 ± 2.3556%, the average adjusting time was 34.89 s for all subjects, and the execution time of a single movement was 381 ms. The corresponding experiment video can be found in the attachment to show the experiment. The method proposed in this work is a method with one sensor to recognize six movements, low hardware conditions, high recognition accuracy, and insensitive to the difference of sensor pasting position.

Bidirectional motion characteristics of resonant inertial impact rotating piezoelectric motor based on self-clamping structure.

A new working principle for multimodal excitation of a resonant bidirectional rotary inertial impact piezoelectric motor with a self-clamping structure was developed based on previous research on piezoelectric motors. Unlike previous piezoelectric motors that relied on single harmonic waves for unidirectional rotation, in this motor, we can simply change the driving signal characteristics of the motor without changing the structure of the piezoelectric motor to excite multiple vibration modes, thereby achieving rotation in both directions. Compared with other bidirectional resonant motors, the structure and control signal are simpler. The finite element simulation software COMSOL5.5 was used to simulate the working mode of the motor, and the results were in good agreement with the final experiment. During the experiments, the optimal operating frequency of the motor prototype was 900 Hz. The maximum output speed of the motor prototype was 3.9 rad/s, the maximum output torque was 15 N mm, and the maximum resolution was 0.248° under the conditions of 240 Vp-p voltage, 900 Hz frequency, and 7.8 N mm preload torque.

A resonant inertial impact rotary piezoelectric motor based on a self-clamping structure.

A resonant inertial impact rotary piezoelectric motor based on a self-clamping structure is designed, assembled, and tested. The designed piezoelectric motor mainly includes a rotor (two vibrators, preload mechanism, and intermediate connection mechanism), a clamping mechanism, and another auxiliary mechanism. The piezoelectric ceramic sheet on the rotor drives the vibrator to swing under the excitation of a single harmonic wave. Because there is a clamping mechanism formed by the combination of clamp baffle and fixed clamp ring, thus the half-cycle resonant rotation of the rotor can be effectively completed, and repeated harmonic excitation can realize the unidirectional continuous rotation and swing of the rotor. The whole excitation process of the motor is in a resonance state, which has significant advantages, such as low friction and simple structure, compared with the traditional quasi-static piezoelectric motor. The structure of the piezoelectric motor is designed and analyzed using COMSOL5.5 software and then the motor performance is tested and analyzed by building an experimental platform to verify the feasibility of the motor design. The final experimental results show that the optimal working frequency of the piezoelectric motor is 150 Hz, which is consistent with the characteristic frequency of the simulation. When the motor prototype is under the conditions of optimal operating frequency 150 Hz, voltage 240 Vp-p, and preload torque 7.8 N.mm, the maximum angular speed can reach 2.4 rad/s, the maximum load can reach 27.8 N mm and the maximum resolution of the movement angle can reach 0.941°.

Research on the bidirectional motion of resonant single-wing bionic piezoelectric motor based on a biasing self-clamping mechanism.

Based on our previous research, this article adds new research content and further refines the previous research on bionic motors. It is in the form of note as a complementary improvement to the previous article. This article proposes a novel approach to achieving reversal motion in such motors driven by a single harmonic signal, specifically the multimode mode of the vibrator. In contrast to the conventional inertial impact piezoelectric motor, we propose a bidirectional piezoelectric motor that can achieve bidirectional motion only by altering the driving signal characteristics. Compared to other bidirectional piezoelectric motors, this motor features a simpler structure and more convenient control. The COMSOL6.0 finite element analysis software was utilized to optimize the working mode of the piezoelectric motor, and an experimental platform was constructed for testing and verifying the performance of the designed prototype. The final experimental data demonstrate that, with an excitation voltage of 300 Vp-p, a preload of 2 N, and an excitation frequency of 781 Hz, the motor prototype achieves a maximum no-load speed of 12.15 mm/s, a maximum resolution of 15.27 µm, and a maximum load of 14 g. These results confirm the validity of the new working mode.

A resonant single-wing bionic piezoelectric motor based on a biasing self-clamping mechanism.

In this study, a resonant single-wing bionic piezoelectric motor based on a biasing self-clamping mechanism inspired by dragonfly flight was designed, assembled, and tested. The main mechanism of the designed piezoelectric motor includes a mover (including a vibrator, clamping foot, bionic pedestal, etc.), a stator, and other auxiliary components. The clamping foot of the mover contacts the side of the stator to form a biasing self-clamping mechanism, which can achieve a clamping effect within half a cycle of the vibrator's resonant vibration. The piezoelectric plate on the vibrator receives a single harmonic excitation from the signal generator, causing the base plate to bend and distort. The base plate drives the clamping foot to move regularly, causing the mover to perform a linear motion. Moreover, repeated single harmonic excitations can realize the continuous movement of the mover. The structure of the piezoelectric motor was optimized using COMSOL6.0, which is a finite element analysis software. The first-order bending vibration of the vibrator was chosen as the working mode through finite element simulation, and an experimental platform was built. The performance of the prototype piezoelectric motor was tested and verified on the experimental platform. The final experimental data show that under the conditions of 300 Vp-p excitation voltage and 109 Hz driving frequency, the maximum no-load speed of the prototype reaches 6.184 mm/s, and the maximum load of the motor is 4 g.

Bidirectional linear inertial impact piezoelectric motor with multimodal resonance.

A new multimodal bidirectional linear inertial impact motor with bidirectional motion based on self-clamping control driven by a single-harmonic signal was designed and manufactured. By applying driving signals of different resonant frequencies to the piezoelectric plate of a piezoelectric motor combined with the unique structural design of the motor, the piezoelectric motor has multiple modes and has the ability of two-way movement. First, the overall structure of the motor is introduced, and its working principle and theoretical displacement characteristics are presented through the periodic motion diagram of the piezoelectric motor. Second, the simulation analysis is carried out to determine the working modal of the proposed motor with COMSOL5.2. Finally, a motor prototype is developed, and the accuracy of the working principle and the simulation analysis is verified through experimental tests. When the motor has no load, the driving voltage is 200 Vp-p. The maximum speed when moving to the right reached 3.125 mm/s when the preload is 2 N, and the driving frequency is 96 Hz. The maximum speed when moving to the left reached 4.301 mm/s when the preload is 4 N, and the driving frequency is 148 Hz. In the load capacity test of the motor prototype, the maximum load of the piezoelectric motor prototype moving to the right and left can reach 0.4 and 0.6 N, respectively. Compared with similar inertial impact motors, the proposed motor achieves flexible control of driving and switching of two-way movement conveniently and has a certain driving ability.

Resonant-type rotating piezoelectric motor with inchworm-inertia composite impact.

A resonant-type rotating piezoelectric motor with inchworm-inertia composite impact was designed and manufactured. It mainly comprises a stator, rotor, support shaft, and frame. The motor stator includes a clamp, driver, central connecting block, preload structure, and other auxiliary mechanisms. The clamp and driver of the motor work in a resonant state. The motor structure was optimized by using the finite element software COMSOL 5.2. Through the finite element simulation analysis, the first-order bending vibration of the clamp and the driver was selected as the working mode, and the consistency of the resonance frequency coupling was optimized and adjusted. By coordinating the bending vibration of the clamp and driver in the vertical staggered direction, the clamping foot drives the rotor to realize the unidirectional continuous rotation. The motor prototype was designed and processed, while the experimental device platform was established to verify the working principle of the motor, and the comprehensive performance of the motor was analyzed and tested. When the input driving voltage was 240 VP-P, the driving frequency was 161 Hz, and the preload torque of the motor was 6.9 N mm, the maximum no-load speed of the motor reached 3.23 rad/s and the maximum load torque reached 10.35 N mm. Under the same conditions, the maximum resolution of the motor rotation angle was 0.69°.

Bidirectional motion characteristics of a single harmonic-driven self-clamping linear piezoelectric motor.

We propose a multimodal model to realize the bidirectional motion of a self-clamping linear piezoelectric motor driven by a single harmonic signal based on previous motor research. Compared with the previous version, only the characteristics of the drive signal need to be changed in the motor without changing any other conditions to excite multimode and achieve reverse movement. The finite element software COMSOL5.2 was used to simulate the mode of the motor. The prototype has a maximum output speed of 71.5 mm/s, a maximum traction of 0.9 N at a voltage of 220 Vp-p, a frequency of 536 Hz, and a preload of 2 N. The minimum resolution of 26.4 µm was achieved at no-load, a voltage of 120 Vp-p, and a preload of 0 N.

Resonant-type inertial impact piezoelectric motor based on a cam locking mechanism.

A new resonant-type inertial impact piezoelectric motor based on a cam locking mechanism was designed, assembled, and tested. The motor is composed of a stator, a rotor, and other auxiliary components. The cam clamping foot of the stator in contact with the inner surface of the rotor forms a cam locking mechanism, which can make the resonant vibration of the stator effective in a half cycle. By receiving sinusoidal signals, the stator generates bending deformation due to the regular deformation of the piezoelectric plate, which drives the cam clamping foot to move and subsequently causes the rotor to rotate. COMSOL5.4 finite element analysis software was used to design the structure of the piezoelectric motor, and an experimental device was built to evaluate and verify the performance of the motor. The maximum no-load speed of the prototype reached 21.61 rpm and the maximum load torque of the motor was 84 N mm under a driving voltage of 360 Vp-p and a driving frequency of 388 Hz. The motor achieved a net efficiency of 5.6% under a preload torque of 2 N mm with the same condition. The maximum resolution of the motion angle of the new motor prototype was 0.0748° with a driving voltage of 160 Vp-p and the same frequency.

Improving Output Performance of a Resonant Piezoelectric Pump by Adding Proof Masses to a U-Shaped Piezoelectric Resonator.

This study proposes the improvement of the output performance of a resonant piezoelectric pump by adding proof masses to the free ends of the prongs of a U-shaped piezoelectric resonator. Simulation analyses show that the out-of-phase resonant frequency of the developed resonator can be tuned more efficiently within a more compact structure to the optimal operating frequency of the check valves by adjusting the thickness of the proof masses, which ensures that both the resonator and the check valves can operate at the best condition in a piezoelectric pump. A separable prototype piezoelectric pump composed of the proposed resonator and two diaphragm pumps was designed and fabricated with outline dimensions of 30 mm × 37 mm × 54 mm. Experimental results demonstrate remarkable improvements in the output performance and working efficiency of the piezoelectric pump. With the working fluid of liquid water and under a sinusoidal driving voltage of 298.5 Vpp, the miniature pump can achieve the maximum flow rate of 2258.9 mL/min with the highest volume efficiency of 77.1% and power consumption of 2.12 W under zero backpressure at 311/312 Hz, and the highest backpressure of 157.3 kPa under zero flow rate at 383 Hz.

Novel piezoelectric rotary motor on the basis of synchronized switching control.

A novel piezoelectric rotary motor (PRM) on the basis of synchronized switching control was designed, fabricated, and tested to achieve high speed, high efficiency, and high torque. The new motor mainly consists of a vibrator working in the resonance state as the driving element of the PRM and a clutch working in the quasi-static state to control the shaft for unidirectional rotation. The finite element method software COMSOL Multiphysics 5.4 was used to design the structure of the motor and determine the feasibility of the design mechanism of the PRM. Moreover, an experimental setup was built to validate the working principles and evaluate the performance of the PRM. The prototype motor outputted a no-load speed of 7.21 rpm and a maximum torque of 54.4 N mm at a vibrator driving voltage of 120 Vp-p and a clutch driving voltage of 200 Vp-p. The motor achieved a net efficiency of 15.6% under the preload torque of 3 N mm. The average stepping angle of the motor with no-load was 0.068°, when the voltages applied to the clutch and the vibrator were 200 Vp-p and 120 Vp-p, respectively, with the frequency of 512 Hz.

Resonant-type inertia linear piezoelectric motor based on a synchronized switching stimulated by harmonic synthesized mechanical square wave.

A novel resonant linear piezoelectric motor based on a synchronized switching stimulated by harmonic synthesized mechanical square wave was designed in this study. The driving mechanism of the motor was also investigated. The periodic square wave motions of the clutch and the vibrator were generated by composing two sinusoidal resonant bending vibrations with a frequency ratio of 1:3. The linear motion of the motor output shaft can be realized through the cooperation between the clutch and the vibrator. An experimental device was established to validate the working principle and evaluate the performance of the motor. The prototype motor reached the maximum no-load velocity of 16.35 mm/s with a clutch driving voltage of 200 Vp-p and a vibrator driving voltage of 240 Vp-p for a base frequency of 809 Hz. The maximum traction force of 5.64 N was obtained under the clutch driving voltage of 200 Vp-p and the vibrator driving voltage of 160 Vp-p for a base frequency of 809 Hz. The motor achieved a net efficiency of 21.43% with a load of 2.25 N.

Resonant-type piezoelectric linear motor driven by harmonic synthesized mechanical square wave.

In this study, a novel resonant piezoelectric linear motor driven by harmonic synthesized mechanical square waves was designed, fabricated, and tested. The motor consists of a stator, a mover, and auxiliary parts. Periodic square wave motions of the stator and the mover were generated by composing two sinusoidal resonant bending vibrations with a frequency ratio of 1:3. Piezoelectric plates were deformed with a certain regularity to drive the piezoelectric motor. The finite element method software COMSOL was used to design the structure of the motor. An experimental device was established to validate the working principle and evaluate the performance of the motor. The prototype motor reached the maximum no-load velocity of 22.5 mm/s with the stator driven voltage of 140 Vp-p and the mover driven voltage of 180 Vp-p for a base frequency. The maximum traction force of 3.8 N was obtained under a stator driving voltage of 140 Vp-p and a mover driving voltage of 100 Vp-p for the base frequency. The motor achieved a net efficiency of 12.2% with a load of 0.3 N.

Inertial piezoelectric linear motor driven by a single-phase harmonic wave with automatic clamping mechanism.

A novel, single-phase, harmonic-driven, inertial piezoelectric linear motor using an automatic clamping mechanism was designed, fabricated, and tested to reduce the sliding friction and simplify the drive mechanism and power supply control of the inertial motor. A piezoelectric bimorph and a flexible hinge were connected in series to form the automatic clamping mechanism. The automatic clamping mechanism was used as the driving and clamping elements. A dynamic simulation by Simulink was performed to prove the feasibility of the motor. The finite element method software COMSOL was used to design the structure of the motor. An experimental setup was built to validate the working principle and evaluate the performance of the motor. The prototype motor outputted a no-load velocity of 3.178 mm/s at a voltage of 220 Vp-p and a maximum traction force of 4.25 N under a preload force of 8 N. The minimum resolution of 1.14 µm was achieved at a driving frequency of 74 Hz, a driving voltage of 50 Vp-p, and a preload force of 0 N.

Bio-inspired piezoelectric linear motor driven by a single-phase harmonic wave with an asymmetric stator.

A novel, bio-inspired, single-phase driven piezoelectric linear motor (PLM) using an asymmetric stator was designed, fabricated, and tested to avoid mode degeneracy and to simplify the drive mechanism of a piezoelectric motor. A piezoelectric transducer composed of two piezoelectric stacks and a displacement amplifier was used as the driving element of the PLM. Two simple and specially designed claws performed elliptical motion. A numerical simulation was performed to design the stator and determine the feasibility of the design mechanism of the PLM. Moreover, an experimental setup was built to validate the working principles, as well as to evaluate the performance, of the PLM. The prototype motor outputs a no-load speed of 233.7 mm/s at a voltage of 180 Vp-p and a maximum thrust force of 2.3 N under a preload of 10 N. This study verified the feasibility of the proposed design and provided a method to simplify the driving harmonic signal and structure of PLMs.

Note: Arbitrary periodical mechanical vibrations can be realized in the resonant state based on multiple tuning fork structure.

We develop a novel approach to match harmonics and vibration modes based on the mechanism of multiple tuning fork structure (MTFS), through which it is promising to realize arbitrary periodical vibrations in the resonant state. A prototype three-layer MTFS with first three harmonics is presented to verify the feasibility of the proposed principle. The matching process and experimental results confirm the unique advantages of MTFS, as discussed in the theoretical analysis. Typical periodical motions, including sawtooth, square, half-wave rectified, and full-wave rectified waveforms, are achieved by the syntheses of resonant harmonics.