Shaft Torque Measurement Research Articles

Blade pressure loading and torque measurement in a transonic linear cascade

Experimental results of a transonic compressor blade pressure loadings and blade shaft torque measurements are presented in this paper. Data were acquired for the cascade middle blade being set to a number of incidence angle offsets to simulate phases of a blade flutter oscillatory motion. This paper should be viewed as a progress report on the ongoing larger research effort on blade flutter in transonic flow regimes.

Influence of drivetrain efficiency determination on the torque control of wind turbines

Decreasing the levelized cost of energy is a major design objective for wind turbines. Accordingly, the control is generally optimized to achieve a high energy production and a high-power coefficient. In partial load range, speed and torque are controlled via the generator torque but the rotor torque determines the power coefficient of the turbine. High uncertainties for the uncalibrated low-speed shaft torque measurement and varying drivetrain efficiencies which depend on the speed, load and temperature lead to a torque control error that reduces the power coefficient of the wind turbine. In this paper the rotor torque control error and the impact on the power coefficient of wind turbines is quantified. For this purpose, the variation of drivetrain efficiency is analyzed. An efficiency model for the wind turbine drivetrain is build and validated on the test bench. Then, the influence of the drivetrain speed, torque loads, non-torque loads, and temperature on the efficiency is quantified. Finally, the influence of the rotor torque control error on the power coefficient was simulated with an aerodynamic model. The results show that of all examined influences only torque and temperature significantly impacting the efficiency leading to rotor torque control errors that reduce the power coefficient and consequently increase the levelized cost of energy. Improved efficiency measurement on WT test benches or drivetrain efficiency modelling can reduce the rotor torque control error and therefore decrease the LCOE.

Shifting Process Optimization of Dedicated Hybrid Transmission

The shifting process of a hybrid electric vehicle (HEV) could be implemented by a motor to simplify the control requirement when the clutch is engaged. In order to reduce the vehicle jerk and simplify the clutch control requirement during the shifting process, this paper introduces a 3-speed dedicated hybrid transmission (3DHT) with P1/P3 configuration and a power shift control strategy. A finite-time linear quadratic regulator (LQR) is proposed to smoothly transfer torque and suppress driveline oscillations during the torque transfer process with a maximum jerk of 5.6 m/s³. Since the clutch stays engaged, a predictive sliding mode control (SMC) is proposed to track the speed of the sleeve quickly and precisely during the synchronization process, which takes 0.18s and maintains a speed difference of around 1 rpm. Furthermore, a Kalman Filter is utilized to overcome the difficulties associated with side shaft torque measurement and low wheel speed resolution. A simulation is performed in MATLAB/SIMULINK, and the powershift (2nd -> 3rd) is compared with other methods. The comparison indicates that the proposed power shift strategy can reduce the maximum jerk from 14.8 m/s3 to 5.6 m/s3, while the entire shifting process lasts for 0.71s. Therefore, the proposed power shift control strategy effectively improves the shift quality.

Kalman filter-based loading rate-dependent hysteresis compensation of flexoelectric torsional responses in polyvinylidene fluoride films for shaft torque sensors

This paper presents a new method of dynamic shaft torque measurement using polyvinylidene fluoride (PVDF) films, one of the new polymer type piezoelectric conversion materials. The measurement method is based on the shear strain gradient and the flexoelectric torsional response of the PVDF films. The loading rate-dependent hysteresis associated with viscoelastic behavior of PVDF film was modeled to estimate the torque input. The torque estimated by the proposed hysteresis model and optimization algorithm (genetic algorithm) can be implemented by the discrete Kalman filter. Because the torque estimated by the real-time Kalman filtering matches well with the actual torque input measured by the commercial in-line torque transducer, a new method of sensing the dynamic shaft torque using the PVDF output signal has been experimentally validated. This study offers potential applications for the development of new torque sensing technology to be widely used in a variety of mechanical engineering areas such as turbines, rotors, automobiles, and robotics.

A statistical approach to zero adjustment in torque measurement of ship propulsion shafts

Abstract Propulsion shaft torque measurement is essential in ship energy efficiency evaluation and emission control. Its accuracy and uncertainty influence decision making in terms of voyage optimisation and fuel consumption. For best results, the measuring device should be adjusted and calibrated adequately. This paper analyses the problem of ship propulsion shaft torque meter zero adjustment. Presented results of initial investigation suggest significant unrepeatability of the torque observed when the propulsion unit is at a standstill. Using a recently designed telemetry torque meter and an older analogue device a series of experimental research was conducted on board of a ship and on marine propulsion units installed in a laboratory. A new statistical method for zero adjustment is proposed and evaluated against methods commonly used on ships. The survey results suggest that the new method is burdened with a lower random error compared to presently used methods and uniquely allows for uncertainty evaluation.

몬테카를로 시뮬레이션을 이용한 시운전 선속-동력 성능에 대한 불확실성 해석

The speed and power performance of a ship is not only a guarantee issue between the ship owner and the ship-yard, but also is related with the Energy Efficiency Design Index (EEDI) regulation. Recently, International Organization for Standardization (ISO) published the procedure of the measurement and assessment for ship speed and power at sea trial. The results of speed and power performance measured in actual sea condition must inevitably include various uncertainty factors. In this study, the influence for systematic error of shaft power measurement system was examined using the Monte Carlo simulation. It is found that the expanded uncertainty of speed and power performance is approximately ±1.2% at the 95% confidence level(k=2) and most of the uncertainty factor is attributed to shaft torque measurement system.

A comparison of wake measurements in motor-driven and flow-driven turbine experiments

We present experimental data to compare and contrast the wake characteristics of a turbine whose rotation is either driven by the oncoming flow or prescribed by a motor. Velocity measurements are collected using two-dimensional particle image velocimetry in the near-wake region of a lift-based, vertical-axis turbine. The wake of this turbine is characterized by a spanwise asymmetric velocity profile which is found to be strongly dependent on the turbine tip speed ratio (TSR), while only weakly dependent on Reynolds number (Re). For a given Re, the TSR is controlled either passively by a mechanical brake or actively by a DC motor. We find that there exists a finite region in TSR versus Re space where the wakes of the motor-driven turbine and flow-driven turbine are indistinguishable to within experimental precision. Outside of this region, the sign of the net circulation in the wake changes as TSR is increased by the motor. Shaft torque measurements show a corresponding sign change above this TSR threshold set by circulation, indicating a transition from net torque due to lift to net torque due to drag produced by the turbine blades, the latter of which can give wake measurements that are inconsistent with a flow-driven turbine. The results support the claim that the turbine kinematics and aerodynamic properties are the sole factors that govern the dynamics of its wake, irrespective of the means to move the turbine blades. This has significance for both experimental and computational studies where it may be necessary, or perhaps more economical, to prescribe the turbine kinematics in order to analyze its aerodynamic characteristics.

Measurements and modelling of the power performance of a model floating wind turbine under controlled conditions

AbstractThis paper describes power performance measurements undertaken on a model floating wind turbine installed on a tension‐leg platform (TLP) in a wind/wave generator facility. Initially, the surge of the platform was measured under different rotor and wave conditions. The surge behaviour depended considerably on the rotor tip speed ratio and the wave frequency and amplitude. High‐frequency data sampling techniques were then used to derive the instantaneous power coefficient and tip speed ratio directly from the measurements, together with the surge velocity of the floating system. The power measurements were compared with those predicted by three independent numerical models, two of which are based on the blade element momentum approach and the third involving a lifting‐line free‐wake vortex model. The fluctuations of the power coefficient with time predicted by the three models were in close agreement; however, these were all significantly larger than those derived from the rotor shaft torque measurements. This was found to be due to the limitations of the torque measurement technique. Although being accurate in measuring the time‐averaged torque, the sensor was incapable of measuring the high‐frequency low‐amplitude fluctuations in the rotor shaft torque induced by the TLP surge. This was confirmed using an alternative experimental technique involving hot‐wire near‐wake measurements. The study also investigated the influence of the platform surge motion on the time‐averaged power coefficients. Both the measurements and the free‐wake vortex model revealed marginal deviations in the time‐averaged power coefficients when compared with those obtained for a fixed, non‐surging rotor. Copyright © 2014 John Wiley & Sons, Ltd.

Contactless Shaft Torque Detection for Wide Range Performance Measurement of Exhaust Gas Turbocharger Turbines

Turbochargers develop away from an auxiliary component—being “off the shelve”—towards an integrated component of the internal combustion engine. Hence, increased attention is paid to the accuracy of the measured turbine and compressor maps. Especially turbine efficiency measurement under engine-relevant operating conditions (pulsed flow) is recently receiving increased attention in the respective research community. Despite various turbine map extrapolation methods, sufficient accuracy of the input test data is indispensable. Accurate experimental data are necessary to achieve high quality extrapolation results, enabling a wide range and precise prediction of turbine behavior under unsteady flow conditions, determined by intermittent operation of the internal combustion engine. The present work describes the first application of a contactless shaft torque measurement technique—based on magnetostriction—to a small automotive turbocharger. The contactless torque measuring system is presented in detail and sensor principle as well as sensor calibration are illustrated. A sensitivity study regarding sensor position influences onto sensor signal proves the robustness and very good repeatability of the system. In the second part of the paper, steady state experimental results from operation on a conventional hot gas test stand over a wide map range are presented. These results are validated against full turbine stage (adiabatic as well as diabatic) CFD results as well as against “cold” efficiency measurements, based on measured inlet and outlet temperatures. The influence and relevance of bearing friction for such measurements is underlined and the improvements on this matter—achieved by direct torque measurement—are demonstrated.

Cost‐effective shaft torque observer for condition monitoring of wind turbines

AbstractImprovement of condition monitoring (CM) systems for wind turbines (WTs) and reduction of the cost of wind energy are possible if knowledge about the condition of different WT components is available. CM based on the WT drive train shaft torque signal can give a better understanding of the gearbox failure mechanisms as well as provide a method for detecting mass imbalance and aerodynamic asymmetry. The major obstacle preventing the industrial application of CM based on the shaft torque signal is the costly measurement equipment which is impractical for long‐term use on operating WTs. This paper suggests a novel approach for low‐cost, indirect monitoring of the shaft torque from standard WT measurements. The shaft torque is estimated recursively from measurements of generator torque, high speed shaft and low speed shaft angular speeds using the well‐known Kalman filter theory. The performance of the augmented Kalman filter with fading memory (AKFF) is compared with the augmented Kalman filter (AKF) using simulated data of the WT for different load conditions, measurement noise levels and WT fault scenarios. A multiple‐model algorithm, based on a set of different Kalman filters, is designed for practical implementation of the shaft torque estimator. Its performance is validated for a scenario where there are frequent changes of operating points. The proposed cost‐effective shaft torque estimator overcomes all major problems, which prevent the industrial application of CM systems based on shaft torque measurements. Future work will be focused on validating the method using experimental data and developing suitable signal processing algorithms for fault detection. Copyright © 2013 John Wiley & Sons, Ltd.

차량 출력 토크 측정 시스템의 시스템 식별

This paper presents a study on the system identification of the in-situ output shaft torque measurement system using a non-contacting magneto-elastic torque transducer installed in a vehicle drivline. The frequency response (transfer) function (FRF) analysis is conducted to interpret the dynamic interaction between the output shaft torque and road side excitation due to the road roughness. In order to identify the frequency response function of vehicle driveline system, two power spectral density (PSD) functions of two random signals: the road roughness profile synthesized from the road roughness index equation and the stationary noise torque extracted from the original torque signal, are first estimated. System identification results show that the output torque signal can be affected by the dynamic characteristics of vehicle driveline systems, as well as the road roughness.

Direct shaft torque measurements in a transient turbine facility

This paper describes the development and implementation of a shaft torque measurement system for the Oxford Turbine Research Facility (formerly the Turbine Test Facility (TTF) at QinetiQ, Farnborough), or OTRF. As part of the recent EU TATEF II programme, the facility was upgraded to allow turbine efficiency measurements to be performed. A shaft torque measurement system was developed as part of this upgrade. The system is unique in that, to the authors’ knowledge, it provided the first direct measurement of shaft torque in a transient turbine facility although the system has wider applicability to rotating test facilities in which power measurement is a requirement. The adopted approach removes the requirement to quantify bearing friction, which can be difficult to accurately calibrate under representative operating conditions. The OTRF is a short duration (approximately 0.4 s run time) isentropic light-piston facility capable of matching all of the non-dimensional parameters important for aerodynamic and heat studies, namely Mach number, Reynolds number, non-dimensional speed, stage pressure ratio and gas-to-wall temperature ratio. The single-stage MT1 turbine used for this study is a highly loaded unshrouded design, and as such is relevant to modern military, or future civil aero-engine design. Shaft torque was measured directly using a custom-built strain gauge-based torque measurement system in the rotating frame of reference. This paper describes the development of this measurement system. The system was calibrated, including the effects of temperature, to a traceable primary standard using a purpose-built facility. The bias and precision uncertainties of the measured torque were ±0.117% and ±0.183%, respectively. To accurately determine the shaft torque developed by a turbine in the OTRF, small corrections due to inertial torque (associated with changes in the rotational speed) and aerodynamic drag (windage) are required. The methods for performing these corrections are described.

IDENTIFICATION OF DRIVE TRAIN SYSTEMS WITH SHAFT TORQUE MEASUREMENTS

This paper studies the problem of estimating mechanical parameters in drive trains. The task is to fit a two-mass model with backlash to experimental data. Normally in, for example, rolling mill applications the measured output is just the motor speed. However, for situations with a light load in comparison to the motor, measurement of motor speed only is insufficient to reach good estimates of all parameters in a two-mass model. As a potential solution we advocate use of a shaft torque measurement in addition to the motor speed.The suggested approach is to use a procedure based on three dedicated experiments: 1) One experiment with a sequence of setpoint steps while maintaining the controller in automatic. This enables estimation of the static gain yielding the total inertia damping and static friction. 2) Then an experiment tailored to guaranteeing that no gap openings are encountered, thus enabling estimation of the other mechanical parameters using linear black-box techniques. 3) Finally yet another experiment that with certainty contains gap openings. A non-linear mechanical model is then used, in combination with a numerical search method to also estimate the gap size.The developed procedure has then been tested successfully on real data from a test rig.

Improved Performance of Motor-Drive Systems by SAW Shaft Torque Feedback

The paper describes the application of a non-contact, high bandwidth, low cost, SAW-based torque measuring system for improving the dynamic performance of industrial process motor-drive systems. Background to the SAW technology and its motor integration is discussed and a resonance ratio control (RRC) technique for the coordinated motion control of multi-inertia mechanical systems, based on the measurement of shaft torque via a SAW-based torque sensor is proposed. Furthermore, a new controller structure, RRC plus disturbance feedback is proposed, which enables the controller to be designed to independently satisfy tracking and regulation performance. A tuning method for the RRC structure is given based on the ITAE index, normalized as a function of the mechanical parameters enabling a direct performance comparison between a basic proportional and integral (PI) controller. The use of a reduced-order state observer is presented to provide a dynamic estimate of the load-side disturbance torque for a multi-inertia mechanical system, with an appraisal of the composite closed-loop dynamics. The control structures are experimentally validated and demonstrate significant improvement in dynamic tracking performance, whilst additionally rejecting periodic load side disturbances, a feature previously unrealisable except by other, high-gain control schemes that impose small stability margins.

An Investigation of the Steady-State Performance of a Pivoted Shoe Journal Bearing with ISO VG 32 and VG 68 Oils

This article presents a report on an investigation into the performance characteristics of a steadily loaded pivoted shoe journal (PSJ) bearing that is lubricated with ISO VG 32 and VG 68 oils. The article describes a testing machine on which the experimental investigation was performed. Measurements of shaft torque, pad temperature distributions, oil inlet and outlet temperatures, oil flow rate, and eccentricity have all been recorded as functions of load and speed. The experimental results from both test oils are presented in graphical form and are compared with theoretical predictions obtained from the author's computer model of the PSJ bearing. These results showed that the thicker ISO VG 68 oil provided thicker oil films. However, it also had higher bearing temperatures and power losses. A good correlation between the theoretical and experimental results has been found. Theoretical analysis of the bearing friction losses indicate that shear losses predominate and churning losses account for approximately 20% of the total losses.

A capacitor-based device for the measurement of shaft torque

This paper describes a capacitor technique for the measurement of torque in a rotating shaft. The passive rotating part incorporates a capacitor bridge which is connected capacitively to the static part. This device is simple in operation and is relatively easy to manufacture.

Micro torque measurements for a prototype turbine

Many applications for microengineered devices can be envisaged for actuators capable of doing work or transferring power. Millimetre order turbines are considered in this study for the development of torque and the possibilities for the delivery of work. A prototype microturbine, with overall thickness of less than a millimetre, was studied for its torque capabilities. The initial prototype was realized using precision mechanics although implementation of the turbine is planned using microengineering techniques. A viscous braking method was developed to measure the shaft torque of the turbine, demonstrating shaft coupling and the possibilities for power transfer. In order to validate the viscous braking method for torque measurement, a mechanical friction brake (dynamometer) was developed to compare the measurements obtained for a miniature electric motor of known characteristics. The results from this series of calibration experiments were then used to evaluate the performance of a microturbine prototype. The dynamometer torque measurements were found to closely agree with the manufacture's stated stall torque for the miniature motor of 1.8*10-4 N m. The viscous brake torque measurements were found to underestimate the motor torque by around 20% with slight variation related to the angular velocity of the shaft. Shaft torque measurements for the prototype microturbine were possible using the viscous brake but not the dynamometer. It was felt that 10-5 N m represented the lower limit for the dynamometer torque measurement while the viscous brake could address torques down to 10-8 N m. The fluid brake produced measurements of torque in the range of 10-7 N m for the microturbine. At this level only an order of magnitude accuracy is claimed because of some uncertainties with the fluid model used for the viscous brake torque calculation. The shaft torque range for the viscous brake was from 10-4 N m down to 10-8 N m; this might be extended by optimizing the fluid model.

Torque calculations of current-source induction machines using the 1-2-0 coordinate system

The authors extend the use of the classical induction motor equations obtained through the 1-2-0 coordinate system to cover situations with nonsinusoidal, chopped current sources. Detailed analysis is demonstrated through the widely used six-pulse, current-source-inverter-fed induction machines. The derivations of two different types of analytical torque equation (time-domain and frequency-domain series equations) are given. Their results are compared with each other and with results obtained from extensive air-gap and shaft torque measurements. The only difference in results between the frequency- and time-domain methods is that the voltage pulse corresponding to the switching is not included in the time-domain method; however, a voltage spike, as indicated by the frequency-domain-series method, would be expected at each switching point because of the rapid change of flux linkage. Test results agree with calculated results. >

Control of surge phenomenon in diesel vehicles. 3rd report. Detection of the shaft torque by an observer and proposal of a new speed control system.

In the preceding report was shown the effectiveness of the new control scheme in which wheel speed is detected to suppress the power-train's torsional vibration called 'surge'. However, the time lag compensation method used therewith was a little too poor to confirm its general efficiency. In the present work was contrived a new lag compensation method in which the shaft torque is taken into consideration, and it is shown that the shaft torque could be indirectly detected through an observer based on the state equation of the engine-vehicle system. An analog circuit observer makes the shaft torque measurement quite successful. Finally is proposed a new speed-control system which is particular to the control of torsional vibration and not that of rotation speed. The new system is expected to improve the driveability of a diesel vehicle since the driver's command directly corresponds to the engine output torque. Engine test demonstrated the validity of the new lag compensation, as well as the effectiveness of the new system.

Development of a rotating-shaft torque sensor for automotive applications

Measurements of the torque in a rotating shaft are often required for automotive powertrain and engine control systems. Conventional shaft torque measurement techniques involve strain gauges and slip rings. While this approach is often used for prototypes and vehicles under development, it is too expensive and not rugged enough for production vehicles. The Ford Motor Company has supported work at Southampton University with the aim of producing a rugged noncontact shaft torque sensor, at a cost which will allow its use for automotive applications. The system described in the paper uses a novel capacitive torque sensor, which is attached to the rotating shaft. The capacitive sensor forms part of a rotating resonant circuit, which is excited across an airgap by means of inductive coupling. Variations in torque cause changes in the resonance frequency of the tuned circuit. The resonance frequency is detected as a change in referred impedance at the exciting coil. Considerable effort has been put into the design of the capacitive torque transducer. A number of practical problems have to be overcome, such as finding a suitable method of adhesion and optimising the capacitor geometry. A satisfactory sensor has now been produced, and work is now being concentrated on improving the passive telemetry system. The torque sensor is currently the subject of a patent application by the Ford Motor Company.