High-precision Torque Research Articles

Contactless Space Debris Detumbling: A Database Approach Based on Computational Fluid Dynamics

This paper aimed to investigate the feasibility of a contactless method to detumble space debris by using thruster plume impingement during proximity operation. To detumble the rotational debris, the force and torque applied to the debris must be precisely estimated by an onboard computer. The high-fidelity computational fluid dynamics (CFD) approach is one of the options for estimating the high precision force and torque applied on the debris, although it entails a huge computational cost. In this study, CFD results, under representative conditions with several relative attitudes and distances, were plotted on a multidimensional map. Then force and torque were derived from the interpolated discrete mapped data, thus reducing the computational time. The present study designed a guidance and control algorithm for debris removal spacecraft, in order to achieve safe and efficient detumbling using estimated force and torque. Dynamics simulations were conducted using this approach to detumble large space debris objects, assuming an upper-stage rocket. The results showed that the contactless detumbling of space debris can be achieved with reasonable fuel consumption and time.

Indirect Measurement of Rotor Dynamic Imbalance for Control Moment Gyroscopes via Gimbal Disturbance Observer.

The high-precision speed control of gimbal servo systems is the key to generating high-precision torque for control moment gyroscopes (CMGs) in spacecrafts. However, the control performance of gimbal servo systems may be degraded significantly by disturbances, especially a dynamic imbalance disturbance with the same frequency as the high-speed rotor. For assembled CMGs, it is very difficult to measure the rotor imbalance directly by using a dynamic balancing machine. In this paper, a gimbal disturbance observer is proposed to estimate the dynamic imbalance of the rotor assembled in the CMG. First, a third-order dynamical system is established to describe the disturbance dynamics of the gimbal servo system, in which the rotor dynamic imbalance torque along the gimbal axis and the other disturbances are modeled to be periodic and bounded, respectively. Then, the gimbal disturbance observer is designed for the third-order dynamical system by using the total disturbance as a virtual measurement. Since the virtual measurement is derived from the inverse dynamics of the gimbal servo system, the information of the rotor dynamic imbalance can be obtained indirectly only using the measurements of gimbal speed and three-phase currents. Semi-physical experimental results demonstrate the effectiveness of the observer by using a CMG simulator.

Torque distribution of The Integrated Magnetically Suspended Inertia Actuator for attitude maneuvers

The Integrated Magnetically Suspended Inertia Actuator (IMSIA), composed of three orthogonal fixed Magnetically Suspended Flywheels (MSFWs) and a Double Gimbal Magnetically Suspended Control Moment Gyros (DGMSCMG), can provide long-term high-precision torque and instantaneous great torque simultaneously. To reduce the electrical energy consumption, a novel torque distribution strategy yielding power optimization is investigated. The proposed scheme adopts the kinetic energy variation of the IMSIA as the cost function and obtains the distribution instructs of the actuators without changing the total torque of the IMSIA. Numerical simulation and tabletop hardware-in-the-loop simulation are carried out to verify the effectiveness of the new strategy. The results show that the new method obviously reduces the energy consumption compared with the traditional minimum-torque strategy.

Fabrication of Microstructured Surfaces by Five-Axis Ultra Precision Machine Tool

In this paper, a five-axis ultra precision machine tool for fabrication of microstructured surfaces is presented. This machine consists of two rotary axes (C&B) and three linear axes (X&Y&Z). High precision aerostatic bearing and torque motor are adopted in C axis (main spindle) and B axis. X axis and Z axis use the hydrostatic guideway and are driven by linear motors. Y axis is driven by torque motor and precision ball screw. This machine is able to realize multiple processing methods, including ultra precision diamond turning, ultra precision milling, fly-cutting, fast tool servo and slow tool servo diamond turning.Furthermore, a large number of experiment researches are carried out. Some typical microstructure surfaces are manufactured, for sinusoidal grid surface, the surface roughness Ra is 11.9nm, which is machined by slow tool servo diamond turning. Micro pyramid array surface is fabricated by using fly-cutting, which performs well both in the profile accuracy and the repeatability. These experiment researches prove that this ultra precision machine is superior in accuracy and system reliability.

Maximum Efficiency Drives of Synchronous Reluctance Motors by a Novel Loss Minimization Controller With Inductance Estimator

This paper presents a method to maximize the driving efficiency of synchronous reluctance motors (SynRMs) having cross-magnetic saturation effects. A novel loss minimization controller that generates the optimum current vector is proposed. In the proposed controller, either an off- or online inductance estimator can be adopted. In both cases, the proposed controller can determine the optimum current vector quickly and automatically, and is capable of both maximizing the driving efficiency and also realizing high-precision torque control. In addition, when the proposed controller with the online inductance estimator is employed, a troublesome offline inductance measurement test is omissible. The validity of the proposed method is verified from simulation and experimental results on a 1.1-kW flux-barrier-type SynRM.

Design and Application of Large Torque Electrical Load Simulator

In order to meet the testing requirement of positive and reverse operation large torque load for new rudder, an electrical load simulator is designed. The system mathematical model is established and the feedforward compensation control of torque and rudder angle is adopted to restrain the surplus torque according to the principle of invariance. The high precision large torque load under positive and reverse operation for rudder is realized by torque and position hybrid control. The practical application shows that the proposed method can effectively restrain surplus torque and the system meets the high precision torque load under positive and reverse operation for rudder very well.

The Measurement and Analysis of Torsional Vibration for Rotating Machinery

In this paper, the virtual instrument technology is used in torsional vibration study to create a set of torsional vibration natural frequency detection scheme for rotating machinery which is based on the characteristics of controllable one-way overrunning clutch. Also, a test system that is highly sampling frequency, good accuracy and fast data processing capability is developed. This system consists of high-precision dynamic torque sensor, microprocessor-based high-speed data relay module, IPC-based workbench. Finally, the measured results and the calculated results were compared, and it shows that the measured and the calculated results come very close.

Range expansion of the reference torque wrench calibration service to 5 kN m at NMIJ

The reference torque wrench (RTW) calibration service within the range from 5Nm to 1kNm has been provided to industry by the National Metrology Institute of Japan (NMIJ) in the National Institute of Advanced Industrial Science and Technology (AIST). Reflecting the strong demand from Japanese industry, the calibration range was extended to 5kNm. First, a high-precision torque transducer in the form of a torque wrench with a rated capacity of 5kNm was developed in order to establish a calibration method for such a large RTW. Second, the calibration method was investigated using a deadweight type torque standard machine with a rated capacity of 20kNm as a reference standard. Aimed expanded calibration range is from 200Nm to 5kNm. As a result of calibration experiment using three transducers having different rated capacities, a relative expanded uncertainty of less than 7.0×10−5 could be obtained at a certain calibration point in the best case.

Design and Research of Hairspring for Portable Online Rotating Viscometer

In the detection of the oil viscosity, rotatory viscometer continues using viscosity-torque transduce principle. Its most trouble of detection structure is the system accuracy problem caused by the elastic element output torque. Development of high precision torque sensor is one of the key technologies to improve the accuracy of torque measurement. This paper, in detail, introduces the detection principle of rotatory viscometer, the working principle of the hairspring, and the specific design of hairspring, which includes the materials, diameter, length, coils of hairspring.

A high performance tilting platform driven by hybrid actuator

Multi-axis controlled machine tools require a tilting rotary table or a tilting spindle head. In order to realize an ultraprecision multi-axis machine tool, it is an important issue to develop a high performance tilting platform. This paper presents a newly developed hybrid actuator-driven tilting platform. The hybrid actuator is constructed by integrating a pneumatic rotary actuator and a couple of voice coil motors. Performance evaluation results confirm that the platform provides high precision and high torque motions.

A note on power-law scaling in a Taylor–Couette flow

Recent studies [Lathrop et al., Phys. Rev. A 46, 6390 (1992); Lewis et al., Phys. Rev. E 59, 5457 (1999)] on Taylor–Couette flow, where the inner cylinder is rotating and the outer one is at rest, show that, despite earlier predictions [Wendt, Ing. Arch. 4, 557 (1933); Tong et al., Phys. Rev. Lett. 65, 2780 (1990)], the non-dimensional torque (G=T/ρν2L) does not follow a fixed power-law scaling (i.e., G∼Reα, where α is a constant value) for 800<Re<1.23×106. Here, we perform simultaneous flow visualization and high precision torque measurements of the same flow configuration using a Haake RS-75 Rheometer to establish if this is also true in the lower Reynolds number range (Re<800). Results show that, although α varies with the Reynolds number, it can be approximated reasonably well with a constant value α=1 for Re/Rec<1 and α=1.5 for 1.5<Re/Rec<6.32. The latter finding is in good agreement with that of Wendt [Ing. Arch. 4, 557 (1933)]. A possible explanation for the differences with the results of earlier studies is provided in this paper.

Sensitivity Evaluation of a Disk-type Torque Transducer Used as a Transfer Device

Abstract A torque transfer device is used for international comparison between torque standard machines or for comparison verification between a torque standard machine and torque calibration machine. This experimental study revealed a problem in the case of using a high-precision torque transducer as the transfer device. For a disk-type torque transducer, it was found that a considerable deviation in the torque output sensitivity occurred depending on the dimensions of the adapter flange and the fastening torque of the screw bolts directly connecting the torque transducer to the adapter flanges. A solution is proposed to overcome this difficulty.

Pseudorotor-flux-oriented control of an induction machine for deep-bar-effect compensation

In an induction machine with deep rotor bars, the rotor parameters change due to skin effect and saturation, and the skin effect is often modeled as a ladder network. For the high-performance drive of an induction machine with deep bars, many sophisticated control strategies and machine models have been discussed. As a control strategy, a complicated airgap flux-oriented control scheme is mostly adopted, because it is not possible to define a unique rotor flux in the deep bar model. However, a unique pseudorotor flux can be defined, and it is straightforward to achieve independent control of pseudorotor flux and torque. This control scheme can be applied to any nth multiple ladder network. In this paper, it is shown how a deep-bar effect of an induction machine can be negligible by performing the proper field-oriented control. By using the concept of pseudorotor flux, the conventional rotor-flux-oriented control using equivalent rotor parameters is effective for deep-bar and/or double-cage machines. The actual insulated gate bipolar transistor (IGBT) inverter systems with a high-precision torque transducer are implemented and thoroughly tested on a 250 hp induction machine and a 5.5 kW double-cage induction machine to confirm their validity.

Phase diagram of Bi2.15Sr1.85CaCu2O8+ delta in the presence of columnar defects.

Using a combination of high-precision torque and SQUID magnetometry we investigate the irreversibility line of single-crystalline ${\mathrm{Bi}}_{2.15}{\mathrm{Sr}}_{1.85}\mathrm{Ca}{\mathrm{Cu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ defected with irradiation-induced columnar pins. We find that the irreversibility line cannot be identified with a shifted melting line but rather follows the crossover line ${B}_{\mathrm{rb}}(T)$ separating the single-vortex strong pinning regime from the collective weak pinning regime. Good agreement is found with a theoretical analysis accounting for the strong layering of the material.

Transition to shear-driven turbulence in Couette-Taylor flow.

Turbulent flow between concentric cylinders is studied in experiments for Reynolds numbers 800R1.23\ifmmode\times\else\texttimes\fi{}${10}^{6}$ for a system with radius ratio \ensuremath{\eta}=0.7246. Despite predictions for the torque scaling as a power law of the Reynolds number, high-precision torque measurements reveal no Reynolds-number range with a fixed power law. A well-defined nonhysteretic transition at R=1.3\ifmmode\times\else\texttimes\fi{}${10}^{4}$ is marked by a change in the Reynolds-number dependence of the torque. Flow quantities such as the axial turbulent diffusivity, the time scales asociated with the fluctuations of the wall shear stress, and the root-mean-square fluctuations of the wall shear stress and its time derivative are all shown to be simply related to the global torque measurements. Above the transition, the torque measurements and observed time scales indicate a close correspondence between this closed-flow system and open-wall--bounded-shear flows such as pipe flow, duct flow, and flow over a flat plate.

High-precision torque control of reluctance motors

A method for the high-precision torque control of a reluctance motor for servo applications is presented. The prototype is a three-phase, eight-pole reluctance motor driven by a MOSFET inverter. The current control as well as the speed control is performed by the software of a digital signal processor. The motor is supplied with sinusoidal current, and two current control methods are proposed. One is based on the vector control principle to achieve linearity between current and torque, and another is developed to obtain the maximum torque/current ratio. Due to the saliency, the instantaneous torque contains a large ripple component. In the case of the test motor, the ripple torque was as much as 26% of the rated torque under the sinusoidal current drive. Experimental results show that the ripple component could be reduced to 6% by superimposing the compensation current component on the current reference. >

DSP-based high precision torque control of permanent magnet DD motor.

Direct drive motor drives the mechanical load without a reduction gear and, therefore, the required precision of torque control is higher than that of the ordinary AC servo motors. The current control is the key technology to realize the high precision torque control.A new software-implemented current control is proposed. Since the proposed method is the extension of the conventional current hysteresis controlled PWM, the algorithm is quite simple and can be implemented within 20 μs using TMS 32010. The processing time is so short that 3-axis control by 1 DSP can be realized.Further, the analysis of the torque ripple due to the non-sinusoidal flux distribution is given and it is shown that the ripple can be compensated by the proposed current control. The additional processing time is 12 μs.Torque ripple is also caused by the offset involved in the current pick up loop. Based on the analysis of torque ripple due to the offset, the compensation algorithm with processing time of 26 μs is proposed and proved to be excellent by experiments. This means the realization of tuning-less drive system.

DSP-based secondary flux controlled high precision torque control of induction motor.

In the field of industrial drives, the vector control of the induction motor has been widely used to achieve the high performance torque control. In this paper, a new high precision torque control of the induction motor has been proposed. The control strategy proposed here is developed according to the conventional vector control law, but it has a feature that the secondary is controlled directly by selecting the appropriate voltage vector of the voltage-fed inverter.The prototype was constructed using a 2.2kW induction motor where the torque control was implemented by software of DSP-TMS 32010. All control processing including the identification of the rotor resistance could be executed within 100μs. From the experimental results, the linear relationship between torque and slip frequency was established for the wide frequency range from rotor rocked condition to 50Hz. Due to identification of rotor resistance, the accuracy of the torque control within ±2% was obtained regardless of the temperature change of the motor.

High precision torque hysteresis measurements on fine particle systems

The application of an automated torque magnetometer to the precise measurement of torque hysteresis is described and results given for magnetic tapes and colloidal cobalt particles set in epoxy resin.

A self-balancing transformer-core-loss bridge

Measuring transformer core loss by impedance bridge methods offers a number of advantages over conventional wattmeter methods, particularly in automation. Human errors are minimized and test accuracy is improved. The bridge is self-balancing and control can be effected either by manual or punched card programming. Direct readings, high precision, and high output torque make the self-balancing bridge particularly suitable for automation.