Linear Encoder Research Articles

Push-Ups are Able to Predict the Bench Press 1-RM and Constitute an Alternative for Measuring Maximum Upper Body Strength Based on Load-Velocity Relationships.

The aims of this study were firstly to compare the similarity in upper-body muscle activation between the bench press and push-up at similar loads, and secondly to establish a 1-RM prediction equation between the two exercises based upon the load-velocity relationship. Twenty resistance-trained male athletes (age 22.5 ± 5.24 years, body mass 83.7 ± 10.7 kg, body height 1.80 ± 0.06 m) performed push-ups and bench presses with four different loads. Push-ups were performed without a weight vest and with a 10-20-30 kg weight vest. Bench presses were performed at 50-80% of athletes’ assumed 1 repetition max (1-RM) in 10 kg steps, while a linear encoder measured performance during the exercises. A load-velocity relationship was established as a product of the load and velocity for the push-up and bench press per participant and the equation was used to establish a predicted 1-RM. Mean muscle activation of eight upper body muscles was recorded for each exercise and each load. The main findings of this study demonstrate an extremely large association between the predicted 1-RM loads performed with the push-up and bench press (r = 0.93) in experienced resistance trained men. Furthermore, most muscles showed similar activations between the two exercises with the different loads except the deltoid and biceps brachii muscles. It may be concluded that it is possible to predict a cross-over 1-RM between the two exercises based upon the load-velocity relationship in each exercise, and that training push-ups largely targets the same muscles as the bench press except the deltoid and biceps muscles. For coaches and athletes, the use of this method is a low cost and time-effective alternative for standard 1-RM bench press testing to predict maximal upper body strength.

Validity And Reliability Of A Mobile App For Measuring Bar Velocity In The Bench Press Exercise

Velocity based-training (VBT) has been demonstrated to be a valid and useful approach to promote greater neuromuscular adaptations in resistance training (RT). This approach typically requires velocity monitoring during RT sessions for appropriate adaptations. The validity and reliability of a chronometer-based mobile App for RT monitoring in the half-squat exercise have been previously shown with a 10 repetition maximum (RM) load, when compared to a linear encoder. However, no data exist with other exercises and different loads. PURPOSE: To determine the validity and reliability of a chronometer-based mobile App for velocity monitoring in the bench press exercise with different loads. METHODS: Twenty handball players (23.0 ± 2.6 yrs, 1.76 ± 0.06 m, 79.6 ± 13.0 kg) completed, after 1RM determination, 5 repetitions with the 25, 40, 55 and 70% of 1RM in the bench press exercise, with the maximal intended velocity, in 2 days separated by 48-72 hrs. Bar velocity (m·s-1) was monitored simultaneously by means of a linear encoder with a sampling rate of 1,000 Hz (reference method), and a chronometer-based mobile App. Validity was examined through paired samples t-test, the Hedge’s effect size (ES), the Pearson’s correlation coefficient (r), and the standard error of estimate (SEE). Reliability was assessed by the coefficient of variation (CV) and the standard error of measurement (SEM). RESULTS: Regarding validity, all relative loads evaluated demonstrated significant differences (P < 0.05) and small to moderate ES (range: 0.31-1.19) between devices, with the mobile App exhibiting greater bar velocities than the linear encoder. However, bar velocities measured with both devices were highly correlated (r ≥ 0.74) with a very low SEE (≤ 0.09 m·s-1). The App exhibited for all loads a low SEM (≤ 0.11 m·s-1), and acceptable CV (< 10%) with the exception of the highest load (70%1RM) (CV = 12.1%). CONCLUSIONS: A chronometer-based mobile App may be considered a valid and reliable method for VBT monitoring in the bench press exercise.

High-velocity Resistance Training Improves Power Output Across The Entire 1RM Percentage Spectrum In Elderly Individuals

The aging process is related to impairments in several biological systems, such as the neuromuscular system. Of concern, considerable reductions in strength and power output are observed after the sixth decade of life, which are strongly related to declines in functional capacity. High-velocity resistance training (HVRT) is an alternative to counteract these impairments in the elderly population. PURPOSE: To compare the mean and peak power output adaptations to twelve weeks of HVRT. METHODS: Thirteen older adults (69.4 ± 6.2 years; 71.5 ± 16.0 kg; 161.8 ± 8.9 cm) were recruited and, after giving their informed consent, completed two familiarization sessions and, on a separate day (baseline), were assessed for their legpress one repetition maximum (1RM) and mean and peak power output at loads corresponding to 30-90% 1RM using a linear encoder. Four weeks after baseline and prior to the intervention (pre-intervention) both 1RM and power tests were repeated and all participants underwent twelve weeks of HVRT twice per week. The exercise training protocol was comprised of five exercises (legpress, knee extension, seated bench press, seated row and calf raise) and progressed from 1-3 sets of 10 repetitions per exercise at 40-60% 1RM. Tests were repeated post-intervention and mean and peak power comparisons were made using one-way ANOVAs with repeated measures and Bonferroni’s post hoc. RESULTS: Mean and peak power output results are shown in Figure 1. Peak power improved significantly at all loads when compared to both baseline and pre-intervention (all p < 0.05), while mean power output improved from 30-70% 1RM (all p < 0.05) but not at 80 and 90% 1RM. No differences were observed between baseline and pre-intervention measures (all p > 0.05). CONCLUSION: HVRT is an effective alternative to counteract power output declines across a wide range of loads in older adults. This is relevant as different functional tasks seem more associated to muscle power at different percentages of 1RM.

Evaluation of the pitch deviation of a linear scale based on a self-calibration method with a Fizeau interferometer

A self-calibration method, in which the wavefronts of zeroth and first-order diffracted beams from a scale grating measured by a Fizeau interferometer are employed, is applied for the evaluation of the pitch deviation of a reflective-type linear scale with a grating pitch of 2.048 μm used in a commercial interferential scanning-type optical linear encoder. One of the advantages of the self-calibration method is that the pitch deviation of a scale grating can be evaluated while measuring the out-of-flatness of the scale grating under inspection and the Z-directional out-of-flatness (surface profile) of the reference optical flat in the Fizeau interferometer. Meanwhile, in a practical case, the self-calibration method is valid under the condition where the out-of-flatness of the scale grating is on the same order or less than that of the reference optical flat in the Fizeau interferometer. In this paper, theoretical analysis and numerical calculations are thus carried out to investigate the influence of the out-of-flatness of the scale grating on measurement of the pitch deviation and the out-of-flatness of the reference optical flat. Some experiments with a linear scale from a commercial interferential scanning-type linear encoder are also carried out to verify the feasibility of the self-calibration method for the evaluation of the pitch deviation of the scale having an out-of-flatness of approximately 600 nm over the analyzed area.

Towards a Chipless and Wireless Passive System for Real‐Time Encoding of the Bladder Volume

AbstractNeurogenic bladder and other lower urinary tract dysfunctions represent a significant health hazard and life‐quality impairment in individuals suffering from neurological disorders. A few implantable and wearable technologies have been proposed to partially recover bladder functionality, mostly based on resistive and capacitive strain gauges designed to be surgically placed inside the pelvic cavity. In this work, an alternative proof‐of‐concept device for monitoring the volumetric changes of the bladder is presented, where the sensing element is based on a capacitive linear encoder integrated with a passive wireless radio‐frequency resonator, which can be remotely interrogated. The sliding mechanism at the core of the proposed system allows a wide sensing range without stringent requirements on materials properties and overall device stability.

Comparison of linear, hyperbolic and double-hyperbolic models to assess the force–velocity relationship in multi-joint exercises

This study assessed the validity of linear, hyperbolic and double-hyperbolic models to fit measured force–velocity (F–V) data in multi-joint exercises and the influence of muscle excitation on the F–V relationship. The force–joint angle and F–V relationships were assessed in 10 cross-training athletes and 14 recreationally resistance-trained subjects in the unilateral leg press (LP) and bilateral bench press (BP) exercises, respectively. A force plate and a linear encoder were installed to register external force and velocity, respectively. Muscle excitation was assessed by surface EMG recording of the quadriceps femoris, biceps femoris and gluteus maximus muscles during the unilateral LP. Linear, Hill’s (hyperbolic) and Edman’s (double-hyperbolic) equations were fitted to the measured F–V data and compared. Measured F–V data were best fitted by double-hyperbolic models in both exercises (p < 0.05). F–V data deviated from the rectangular hyperbola above a breakpoint located at 90% of measured isometric force (F 0) and from the linearity at ≤45% of F 0 (both p < 0.05). Hyperbolic equations overestimated F 0 values by 13 ± 11% and 6 ± 6% in the LP and BP, respectively (p < 0.05). No differences were found between muscle excitation levels below and above the breakpoint (p > 0.05). Large associations between variables obtained from linear and double-hyperbolic models were noted for F 0, maximum muscle power, and velocity between 25% and 100% of F 0 (r = 0.70–0.99; all p < 0.05). The F–V relationship in multi-joint exercises was double-hyperbolic, which was unrelated with lower muscle excitation levels. However, linear models may be valid to assess F 0, maximal muscle power and velocity between 25% and 100% of F 0.

Fault Tolerant Control Based on an Observer on PI Servo Design for a High-Speed Automation Machine

The fault tolerant control (FTC) technique is widely used in many industries to provide tolerance to systems so that they can operate when a system fault occurs. This paper presents a technique for FTC based on the observer signal application, which is used for a high-speed auto core adhesion mounting machine. The utilization of the observer signal information of the linear encoder fault is employed to adjust the gain parameters to achieve the appropriate gain value while maintaining the required performance of the system. The dynamic modeling of the servo motor system design utilizing a pole placement technique was designed to support the proposed method. A scaling gain fault step size adjustment from −1% to 1% with increments of 0.2% is used to simulate the fault conditions of the linear encoder. The statistical mean value of the observer error signal is used to train the artificial neural network (ANN) model. The results showed that the control system design successfully tracked the dynamic response. Furthermore, the ANN model, with more than 98% confidence, was satisfactory in classifying the linear encoder fault condition. The gain compensation was successful in reducing position error by more than 95% compared with the system without compensated gain.

Design and testing of a linear encoder capable of measuring absolute distance

A linear encoder that can be used for commercial absolute precision-positioning applications was designed and tested. This prototype consists of an improved single-track grating scale and a compact two-probe reading head. The specified grating scale was fabricated in such way that multiple reference codes can be superimposed physically on incremental grooves. The reading head is based on a two-probe design, where one probe is used to read the continuous incremental grooves by grating interferometry, while the other probe identifies the discrete reference codes by superimposing the codes with a stationary mask. In other words, the encoder enables the simultaneous measurement of both displacement and position of a precision stage. The so constructed linear encoder prototype was tested thoroughly. The period of the incremental grating structure was calibrated before the measurement range was set to 20 mm to include the two reference codes. The experimental results were verified, and an accuracy for the measured incremental displacement of at least 1 μm was achieved with comparison with a laser interferometer used as the reference. Especially the distance between two reference codes was calculated to evaluate the positioning accuracy of the grating system. The positioning accuracy exceeds 0.22 μm according to our statistical analysis of 12 groups of repeated measurements.

An FPGA Platform for Next-Generation Grating Encoders.

Among various nanometer-level displacement measurement methods, grating interferometry-based linear encoders are widely used due to their high robustness, relatively low cost, and compactness. One trend of grating encoders is multi-axis measurement capability for simultaneous precision positioning and small order error motion measurement. However, due to both lack of suitable hardware data processing platform and of a real-time displacement calculation system, meeting the requirements of real-time data processing while maintaining the nanometer order resolutions on all these axes is a challenge. To solve above-mentioned problem, in this paper we introduce a design and experimental validation of a field programmable gate array (FPGA)-cored real-time data processing platform for grating encoders. This platform includes the following functions. First, a front-end photodetector and I/V conversion analog circuit are used to realize basic analog signal filtering, while an eight-channel parallel, 16-bit precision, 200 kSPS maximum acquisition rate Analog-to-digital (ADC) is used to obtain digital signals that are easy to process. Then, an FPGA-based digital signal processing platform is implemented, which can calculate the displacement values corresponding to the phase subdivision signals in parallel and in real time at high speed. Finally, the displacement result is transferred by USB2.0 to the PC in real time through an Universal Asynchronous Receiver/Transmitter (UART) serial port to form a complete real-time displacement calculation system. The experimental results show that the system achieves real-time data processing and displacement result display while meeting the high accuracy of traditional offline data solution methods, which demonstrates the industrial potential and practicality of our absolute two-dimensional grating scale displacement measurement system.

Design of low power fault tolerant flash ADC for instrumentation applications

Technological growth has remarkably put their efforts in making the electronic world a powerful one. Analog to digital converter (ADC) is said to be ancestor in the field of transforming analog information into digital form. It is a necessary component in RF and Mixed signal designs. This paper suggests both neither compact NOR based CMOS Linear Tuneable Transconductance Element (NOR-LTE) Comparator and Dynamic Priority Encoder (DPE). The NOR-LTE comparator reduces the power utilization and offset error, which improves the Power Supply Rejection Ratio (PSRR) of an overall circuit design. Dynamic Priority Encoder curtails the transistor count prescribed for Flash ADC. The proposed Fault Tolerant Flash ADC (FT-FADC) framework is implemented using Tanner EDA with 0.25 ​ ​μm CMOS technology. The above suggested FT- FADC achieves 3.44-bit ENOB at 1.5 ​V supply for 500 ​MHz Resolution Bandwidth (RSB). Due to high sampling rate 1.3 ​GS/s it upgrades the throughput rate by 60% and reduces the utilization of power by 47%.

Experimental Investigation of Linear Encoder’s Subdivisional Errors under Different Scanning Speeds

Optical encoders are widely used in applications requiring precise displacement measurement and fluent motion control. To reach high positioning accuracy and repeatability, and to create a more stable speed-control loop, essential attention must be directed to the subdivisional error (SDE) of the used encoder. This error influences the interpolation process and restricts the ability to achieve a high resolution. The SDE could be caused by various factors, such as the particular design of the reading head and the optical scanning principle, quality of the measuring scale, any kind of relative orientation changes between the optical components caused by mechanical vibrations or deformations, or scanning speed. If the distorted analog signals are not corrected before interpolation, it is very important to know the limitations of the used encoder. The methodology described in this paper could be used to determine the magnitude of an SDE and its trend. This method is based on a constant-speed test and does not require high-accuracy reference. The performed experimental investigation of the standard optical linear encoder SDE under different scanning speeds revealed the linear relationship between the tested encoder’s traversing velocity and the error value. A more detailed investigation of the obtained results was done on the basis of fast Fourier transformation (FFT) to understand the physical nature of the SDE, and to consider how to improve the performance of the encoder.

Dynamic Behaviour Analysis of Optical Linear Encoder under Mechanical Vibrations

Mechanical vibrations are probably inevitable and occur in more or less all machine tools and other technological equipment. In case the linear encoder is used for moveable parts positioning in such machines, vibrations could cause additional errors. This paper investigates the dynamic behavior of the optical linear encoder under mechanical vibrations. Potentially the most harmful frequencies are determined experimentally, and the corresponding mode shapes are simulated by using finite element method (FEM). Obtained results describe tested encoder`s construction dynamic response to external excitation and could be used to improve its design.

Experimental Study of Double-Acting Pneumatic Cylinder

In this article, the dynamics of a double-acting pneumatic actuator was experimentally studied. To understand the details of dynamics and provide experimental data for further modeling and numerical simulation of actuators, a special test bench was designed. The bench includes a high-resolution linear encoder as well as a dSPACE 1104 data acquisition board, that permits high-frequency sampling to identify important features in the measured data at different source pressures; it also incorporates two pressure sensors, a solenoid valve, a push button, and a measuring interface to automate the acquisition of data. High precision measurements of the time of displacement and position of the moving elements, piston rod or cylinder body, allowed us to calculate velocity and acceleration. We found that the velocity of the moving element is near constant in a major part of the stroke. The recording of the dynamics of upstream and downstream pressures in the pneumatic cylinder chambers at different source pressure levels permitted us to calculate the force exerting by the piston and to explain the kinematics of the moving element. The matching of the upstream and downstream pressure plots with the displacement of the moving element allowed us to establish the instant when the moving starts, and this way evaluates such an important feature as the static friction force between the piston and cylinder body. Various scenarios were used in the experiments, including the fixing of the piston rod, which allow the cylinder body to move or vice versa, the horizontal or vertical position of the pneumatic cylinder and the forward or backward stroke movement. The results obtained with the proposed experimental bench provide essential information on the dynamics of a double-acting pneumatic cylinder that can be included in the mathematical model of the cylinder and used in mobile robotics.

Relationship Between Bench Press Strength and Punch Performance in Male Professional Boxers.

López-Laval, I, Sitko, S, Muñiz-Pardos, B, Cirer-Sastre, R, and Calleja-González, J. Relationship between bench press strength and punch performance in male professional boxers. J Strength Cond Res 34(2): 308-312, 2020-This study investigated the relationship between punching performance and the velocity at which different loads were lifted during the bench press (BP) exercise in 12 professional boxers (age = 22.6 ± 4 years; height = 177.7 ± 5 cm; body mass 70.6 ± 6.43 kg; years of boxing experience = 6.5 ± 3.5 years; weight class = from light to super welterweight). To determine the maximal punching velocity (PVmax) during both rear arm (RA) and lead arm (LA) punching, an accelerometer (Crossbow; Willow Technologies, Sussex, United Kingdom) was placed inside the boxing glove while executing 3 jabs at a maximal velocity with each arm. Upper-body strength was assessed through the direct 1-repetition maximum (1RM) BP test, and the maximum velocity at different percentages of 1RM was obtained with a linear encoder. The main finding was that RA PVmax was correlated with the BP velocity at all submaximal intensities (p < 0.05). Nevertheless, LA PVmax did not correlate with BP velocity at any intensity. When the correlated BP submaximal intensities were introduced in linear regression models, the velocity at 80% 1RM was the only predictor of RA PVmax (r = 0.75; p < 0.01) in professional boxers. Additional body mass adjustment to the regression model significantly affected the predictive value (r = 0.65; p < 0.005). Results encourage coaches and trainers to use BP exercise with high loads (i.e., 80% of 1RM) because this could be a reliable predictor of performance during the specific boxing action. Future research is needed to determine exercises and intensities that could explain LA PVmax because significant associations were not found.

Effect of Flattening Cracked Medium on Positioning Accuracy of a Linear Magnetic Encoder

Linear magnetic recording medium is a crucial and necessary component in a linear magnetic position sensing system. During the manufacturing of the magnetic medium, shape defects would often be observed due to various manufacturing processes. As a result, shape defects in the magnetic medium would alter the recording accuracy during position measurement of the magnetic reader. Thus, a flattening process is introduced for flattening of curved magnetic medium. Previous studies have demonstrated its effectiveness in flattening of magnetic medium. In this article, a further step is taken to examine the crack formation in the microstructure of the magnetic medium during flattening process to ensure the quality and recording accuracy of the magnetic medium. The experimental results have demonstrated that crack propagation would continue to grow under the influence of flattening process if crack initiation is found prior to the flattening process. Nonetheless, the measured linear position accuracy showed that the accuracy improved after the flattening process despite crack propagation occurring on the mechanical quality of the medium. In other words, the results have demonstrated that the effect of mechanical shape defects on linear position accuracy is more important than that of crack formation on the magnetic medium. Through understanding the crack formation of the magnetic medium, the accuracy of the recording medium can be improved by modification of the magnetic medium and flattening conditions.

The effect of different loads on semi-tethered swimming and its relationship with dry-land performance variables

ABSTRACTSemi-tethered loaded swimming (denoted STLS) has been used widely to develop or test swimmers skills, although its transference to increase performance seems overestimated. In addition, its relationship with dry-land tests remains obscured by imprecise reports. Sixteen competitive male swimmers (age: 18.31 ± 1.42) participated in a two-fold purpose study: Firstly, swimming performance was assessed at different STLS intensities on an adapted Smith Machine. A repeated measures 1-way ANOVA was conducted to find differences between the variables collected through a linear encoder at 15%, 30%, 45% and 60% of the maximal load (ML). Secondly, the relationships between the swimming velocities and the different sorts of variables obtained on a dry-land arm-stroke strength test were studied by Pearson’s correlation coefficient (r). The results showed that less velocity, acceleration and impulse were delivered at high loads (p < 0.001). It increased the velocity fluctuation, affecting the swimming patterns adversely. On the other hand, the correlations between velocity-based dry-land variables and swimming velocities (r = 0.71) seem to be more suitable to predict swimming performance, rather than strength-based variables (r = 0.49). In conclusion, coaches should reconsider using STLS, as little or no benefit may be obtained in performance.

Rate control of tip-tilt mirror using position sensors for an image-based tracking loop

For an image-based tracking loop system of tip-tilt mirror, the traditional control methodologies mainly include a single-position loop or two-position loop. The most effective method for enhancing tracking performance is to increase control gain for a high bandwidth. However, the image sensor sampling rate and time delay engendered by data processing restricts the bandwidth. Therefore, a position-rate control method is proposed to improve the performance of a tip-tilt mirror control system. The angular rate of tip-tilt mirror is calculated from the angular position measured by the linear encoder. The open-loop rate transfer function of tip-tilt mirror features differential in the low-frequency domain because the original tip-tilt control system is zero-type. When the inner rate feedback loop is implemented, an integrator is introduced into the original position loop. A PI (proportional-integral) controller can stabilize the position loop such that two integrators are in the tracking loop, so the low-frequency performance can be improved compared to the original control method. The experimental results coincide with the theoretical analysis and then verify the correctness of the presented theories.

Advanced linear encoder calibration system with sub-nanometer resolution

Calibration of linear encoders has conventionally been performed using an optical interferometer for reference. Calibration using the optical interferometer, however, cannot fulfill the accuracy and stability requirements when the linear encoders exhibit sub-nanometer resolution. This study describes a new calibration method developed using the picometer resolution laser holographic scale as a reference, employing a range-dependent and minimum error-variance algorithm. The method has been evaluated via comparison tests with conventional optical-interferometer-based methods. Moreover, it has also been verified to achieve higher resolution, accuracy, and higher stability during the measurements, even in the atmospheric environment.

Robust Speech Filter and Voice Encoder Parameter Estimation Using the Phase–Phase Correlator

In recent years, linear prediction voice encoders have become very efficient in terms of computing execution time and channel bandwidth usage while providing, in the absence of impulsive noise, natural sounding synthetic speech signals. This good performance has been achieved via the use of a maximum likelihood parameter estimation of an auto-regressive model of order ten that best fits the speech signal under the assumption that the signal and the noise are Gaussian stochastic processes. However, this method breaks down in the presence of impulse noise, which is common in practice, resulting in harsh or non-intelligible audio signals. In this paper, we propose a robust estimator of correlation, the Phase-Phase correlator that is able to cope with impulsive noise. Utilizing this correlator, we develop a Robust Mixed Excitation Linear Prediction encoder that provides improved audio quality for voiced, unvoiced, and transition speech segments. This is achieved by applying a statistical test to robust Mahalanobis distances for identifying the outliers in the corrupted speech signal, which are then replaced with filtered signals. Simulation results reveal that the proposed estimator of correlator outperforms in variance, bias, and breakdown point compared to three other robust approaches based on the arcsin law, the polarity coincidence correlator, and the median-of-ratio estimator without sacrificing the encoder bandwidth efficiency and the compression gain while remaining compatible with real-time applications. Furthermore, in the presence of impulsive noise, the proposed speech encoder speech subjective quality outperforms the state-of-the-art in terms of mean opinion score.

Sensorless Control of Linear Flux-Switching Permanent Magnet Motor Based on Extended Kalman Filter

Linear flux-switching permanent magnet (LFSPM) motors have drawn extensive concern for rail transit drive systems because permanent magnets and armature windings are all located on the short primary, whereas the long secondary is made up of iron only. Thus, the LFSPM motor with low cost and high efficiency is an excellent choice for urban rail transportation system. However, the installation of linear encoders that are expensive and unreliable along with the long stator will bring about increased costs and reduced reliability. To overcome the shortcomings and fully exert the advantages of LFSPM motors, extended Kalman filter (EKF) is adopted to achieve sensorless control of LFSPMs for its better stability, robustness, and low requirements for working environment in this article. An improving tracking performance can be obtained using EKF considering the end effects of LFSPMs and the presence of noise. Both simulation and experimental results indicate that the motor can run reliably from standstill without position sensors, which is advantageous compared with other sensorless control methods based on electromotive force.