Equivalent Torque Research Articles

An event-triggered approach to torsional vibration control of drill-string system using measurement-while-drilling data

Suppressing torsional vibration of drill-string has great safety and economic importance to drilling process. Note that most existing control methods only measure surface information, their performance are limited, especially for a long drill-string. In this paper, an advanced control system is developed to mitigate torsional vibration of drill-string, using a measurement-while-drilling (MWD) communication tool to collect downhole information. The drill-string is described by a lumped parameter model to include full torsional flexibility modes with less computational complexity. A state observer and a filter are combined to estimate an equivalent control torque to cope with uncertain bit–rock interaction. Considering that the communication and power resources are quite precious for MWD, the downhole state is periodically sampled and an event-triggered mechanism is devised to pick out only some key sampled data for transmission to the surface. Using both the surface continuous measurement and the discrete MWD data with transmission delays, the closed loop of the drill-string and the control system is modeled as a nonlinear time-delay system, based on which sufficient conditions are derived for stability analysis and calculation of gain matrices. A numerical case study is carried out to verify the effectiveness of the approach.

Adaptive Sliding Mode Control Based on Disturbance Observer for Placement Pressure Control System

In the process of composite placement, irregularity and asymmetry pressure fluctuation will affect the density and evenness of composite products, which lead to the inconsistency of interfacial strength and fiber volume fraction. The dynamic performance of placement pressure systems will be affected by external disturbance, mechanism friction and measurement noise. In this paper, an adaptive sliding mode control (ASMC) strategy based on disturbance observer (DOB) is proposed. The disturbance observer is introduced to estimate the equivalent disturbance torque, and the estimation error is compensated by the switching term of sliding mode control. The adaptive method is used to ensure that the switching gain is not overestimated, and then the Lyapunov function is used to verify the stability of the closed-loop control system. The experimental results and simulation analysis show that ASMC-DOB has high control accuracy and good robustness. At the same time, the designed algorithm can effectively reduce the void content of composite products.

Satellite attitude control using a novel Constrained Magnetic Linear Quadratic Regulator

This paper addresses a novel Constrained Magnetic Linear Quadratic Regulator (CM-LQR) scheme that generates a control torque vector on a plane approximately perpendicular to the local geomagnetic field. This control torque nearly precisely guarantees the production of an equivalent mechanical torque. The main ideas in the proposed method are (1) excluding the actuator dynamics from the system dynamics, and (2) incorporating the designed dynamics in the problem formulation using an algebraic mathematical constraint. In this way, a common time-variant system is transformed into a time-invariant system. The proposed CM-LQR generates the control torque via adjusting a time-variant control weighting matrix according to the geomagnetic field feedback. Unlike previous methods, our proposed control torque has a negligible parallel projection to the local geomagnetic field, and thus, it can be utilized fully by the magnetorquers. The hybrid Genetic Algorithm (GA) and Sequential Quadratic Programming (SQP) methods are applied to find an optimum state weighting matrix. Moreover, numerical simulation is performed to evaluate the performance and agility of the closed-loop control system. In addition, the obtained results are compared with a conventional magnetic LQR attitude controller to confirm that the presented scheme results in more agility and lower steady-state error in the attitude maneuver of the magnetically actuated satellites.

Design of a Novel Low-Cost Consequent-Pole Permanent Magnet Synchronous Machine

This article proposes a novel low-cost consequent-pole permanent magnet (CPM) synchronous machine structure, considering the reluctance torque utilization. First, a novel CPM machine with doubled salient ferromagnetic iron poles (ICP-PMSM) is proposed, featuring an N pole - iron - S pole - iron sequence to maximize the reluctance torque utilization and reduce cost. Flux barriers are integrated into the rotor structure to maintain the same magnetic rotor pole number as the conventional CPM synchronous machine (CP-PMSM). Second, for a low torque ripple, soft ferrite is used to replace part of the iron pole in the ICP-PMSM (ISCP-PMSM) to improve the air-gap flux density distribution. Furthermore, the CP-PMSM, ICP-SPMSM, and ISCP-PMSM rotors are optimized for a fair comparison. The electromagnetic performances of all the optimized machines are compared with those of a conventional surface permanent magnet synchronous machine (SPMSM). It is demonstrated that the ISCP-PMSM can obtain an almost equivalent torque and torque ripple, but with reduced PM (NdFeB) usage and cost when compared to the SPMSM.

Автоматизоване управління режимами прокатки на товстолистових станах

Indicators of rolling quality and rolling process are presented, which determine the efficiency of plate mill operation. The purposes of the automated control of rolling which consist in achievement of an optimum ratio of the mentioned indicators, and division of control channels (when it’s possible) achiev-ing the best values of each indicator named above. Control of rolling modes (compression on passes, speeds, cooling) provides the main effect in indicators quality formation of hire and rolling process. The statement of the problem of automated rolling control is given. The choice of the optimized indicator in the problem of automatic rolling control is determined by its economic significance, the nature of the interrelation with the technological parameters and controls. One of the most economically significant for plate mills is the coefficient of metal consumption of the workpiece per ton of rolled product, or the yield, which depends on the accuracy of the implementation of the specified geometric dimensions of the rolling strip. The formulation of the problem of ensuring the minimum value of deviations in the thickness (width) of the strip from the specified value is given. The problem of optimization on one of three indicators of the rolling process is also formulated: the equivalent torque of the main drive, the electricity consumption for rolling and the time consumption of the rolling cycle, which are determined by the entire course of the rolling cycle, i.e. applied management strategy. The principles of solving the problem of automatic control of rolling modes are described. The rolling control strategies used in the ACS TP of plate mills are considered. Methods of constructing mathematical models for ACS TP of plate mills, as well as their adaptation, are described.

Novel servo-feed-drive model considering cutting force and structural effects in milling to predict servo dynamic behaviors

This paper presents an integrated servo-feed-drive model including the cutting force and structural effect to predict tracking errors in an end-milling process. Most conventional approaches consider the cutting force to be an equivalent torque to servo feed drive. However, in addition to acting as the equivalent torque to the servo feed drive, cutting forces also cause the machine table to vibrate. This paper considers the aforementioned cutting-force effects to predict tracking errors and then verifies the tracking errors using experimental results. Experiments are conducted on a 3-axis computer numerical control (CNC) machining center to validate the tracking errors predicted by the proposed servo-feed-drive model. For one case study, the peak-to-peak tracking errors from the experimental, proposed, and traditional models are 3 μm, 2.8 μm, and 0.5 μm, respectively, for the x-axis, and 2.1 μm, 1.7 μm, and 0.4 μm, respectively, for the y-axis. The experimental results illustrate that the tracking errors predicted using the proposed model are more accurate than those predicted using the traditional model without consideration of the transmission path. Therefore, it can be concluded that the proposed integrated model provides much accurate tracking-error prediction, and thus, the ball-screw and machine-table flexibilities should be considered.

Strength analysis of mechanical transmission using equivalent torque of plow tillage of an 82 kW-class tractor

Strength analysis of mechanical transmission using equivalent torque of plow tillage of an 82 kW-class tractor

An Analysis of the Mechanism of the Self-Increasing Brake System

The auxiliary brake is closely associated with the safety of passengers. Despite the issues of insufficient braking torque and excessive impact in the existing auxiliary brake, the self-increasing brake system has the characteristics of stable and reliable braking in favor of passengers’ safety. It is of great significance to study the mechanisms in the self-increasing brake system. In this paper, kinematic analysis along with mechanical analysis is used to study the braking torque under both static and dynamic conditions. The equivalent braking torque test and braking deceleration test are also conducted to evaluate the braking performance. It is shown that the braking in down direction conforms with the regulations. Researches have indicated that, even under the circumstance of a small theoretical value of braking torque, the self-increasing brake still meets the norms with a stable braking process as well as a limited impact, thanks to the combined effect of self-increasing torque. It can be seen that the self-increasing torque can directly influence the braking torque and the maximum deceleration.

Novel Hybrid-Pole Rotors for Consequent-Pole PM Machines Without Unipolar Leakage Flux

This paper presents two novel consequent-pole permanent magnet (PM) machines featuring N-iron-N-iron-N-S-iron-S-iron-S and iron-S-iron-S-iron-iron-N-iron-N-iron sequences. In order to provide assistant flux and suppress the subharmonics of the air-gap flux density, the tangential PMs are embedded into the proposed rotors of the consequent-pole PM (CPM) machines to form the novel hybrid-pole PM (HPM) machines. The principle of eliminating unipolar leakage flux and the performance improvement by hybrid pole are analyzed based on the simplified PM magnetic circuit. Then, the proposed rotors of CPM and HPM machines, as well as their conventional counterpart with an N-iron sequence, are optimized by finite-element analyses. Furthermore, the electromagnetic performances of the proposed machines, including the open-circuit air-gap flux density, average torque, torque ripple, loss, efficiency, unbalanced magnetic force, demagnetization withstand capability, and unipolar leakage flux, are compared with that of the conventional surface-mounted PM (SPM) and CPM machines. It is demonstrated that both the conventional CPM and proposed HPM machines have >20% higher PM material utilization ratio than the SPM machine. The proposed HPM machine can obtain almost equivalent torque and efficiency compared to the conventional CPM machine. Moreover, unipolar leakage flux does not exist in the end shaft, and thus the magnetization of the mechanical components can be effectively eliminated. Finally, a 9-slot/10-pole HPM machine is prototyped and measured to validate the analyses.

Design, modeling and experimental evaluation of a legged, multi-vectored water-jet composite driving mechanism for an amphibious spherical robot

This paper designs a novel legged, multi-vectored water-jet composite driving mechanism (LMWCDM) for the amphibious spherical robot (ASRobot) and presents modeling and experimental evaluation of this composite driving mechanism. In order to crawl on land flexibly, the robot was designed in SolidWorks and simulated in ADAMS environment with the sit to stand motion and a crawling gait. Then the simulation results, such as driving torques, guided the selection of servomotors in different joints. In aquatic environment, the dynamic modeling of ASRobot was analyzed by synthesizing the propulsive vectors of four propellers in each workspace of legs. Simplistically, multiple underwater locomotion, such as longitudinal and lateral motion, rotary motion, sinking and floating motion and cruising motion, were proposed. Thus, using a six-axis force/torque sensor at the equivalent mass center, a force and torque measuring mechanism was developed to obtain the direct propulsive effect and validate the modeling of the driving system. To evaluate the robot design and selection of servomotors, experiments of the sit to stand motion and crawling motion were conducted. Underwater testing experiments of LMWCDM were carried out to verify the modeling of rotary motion, sinking and floating motion. Besides, underwater test of the robot prototype also proved the highly flexible and swift motion.

Range of Motion Testing of a Novel 3D-Printed Synthetic Spine Model.

Study Design:Biomechanical model study.Objective:The Barrow Biomimetic Spine (BBS) project is a resident-driven effort to manufacture a synthetic spine model with high biomechanical fidelity to human tissue. The purpose of this study was to investigate the performance of the current generation of BBS models on biomechanical testing of range of motion (ROM) and axial compression and to compare the performance of these models to historical cadaveric data acquired using the same testing protocol.Methods:Six synthetic spine models comprising L3-5 segments were manufactured with variable soft-tissue densities and print orientations. Models underwent torque loading to a maximum of 7.5 N m. Torques were applied to the models in flexion-extension, lateral bending, axial rotation, and axial compression. Results were compared with historic cadaveric control data.Results:Each model demonstrated steadily decreasing ROM on flexion-extension testing with increasing density of the intervertebral discs and surrounding ligamentous structures. Vertically printed models demonstrated markedly less ROM than equivalent models printed horizontally at both L3-4 (5.0° vs 14.0°) and L4-5 (3.9° vs 15.2°). Models D and E demonstrated ROM values that bracketed the cadaveric controls at equivalent torque loads (7.5 N m).Conclusions:This study identified relevant variables that affect synthetic spine model ROM and compressibility, confirmed that the models perform predictably with changes in these print variables, and identified a set of model parameters that result in a synthetic model with overall ROM that approximates that of a cadaveric model. Future studies can be undertaken to refine model performance and determine intermodel variability.

Comparative Study of Consequent-Pole and Hybrid-Pole Permanent Magnet Machines

This paper presents a novel consequent-pole permanent magnet (PM) (CPM) machine featuring N-S-iron sequences. In order to enhance the output torque and efficiency, the flux barriers are employed to improve the magnetic symmetry and reduce the saturation of the stator yoke. The tangential magnetized PMs are embedded in the flux barriers to form the hybrid-pole PM (HPM) machine, which further improves the output torque and efficiency. The rotor of the proposed CPM and HPM machines, as well as its conventional counterpart which employing N-iron sequences, are optimized by finite element analysis. Furthermore, the electromagnetic performances of the proposed machines, including the open-circuit airgap flux density, back EMF, average torque, torque ripple, efficiency, flux-weakening capability, unbalanced magnetic force, and unipolar leakage flux, are compared with the conventional CPM machine. It is demonstrated that the proposed HPM machine can obtain almost equivalent torque, efficiency, and better flux-weakening capability when compared to the conventional one. Moreover, the proposed HPM machine has no unipolar leakage flux in the end region, and thus the magnetization of the mechanical components can be effectively reduced. Finally, a 9-slot/8-pole HPM machine is prototyped and measured to validate the analyses.

A Simplified Predictive Torque Control Scheme for Open-End Winding Induction Motor Drive

Variable speed induction motor (IM) drives with predictive torque control (PTC) technique is an advancing technology nowadays. The PTC technique is introduced for dual-inverter fed open-end winding IM (OEWIM) configuration owing to its benefits. The conventional PTC requires flux weighting factor assignment because of two different control objectives (torque and flux) in single cost function. This weighting factor selection plays a key role in selecting optimal voltage vector for better torque and flux response. Several analytical and empirical methods are introduced for optimal selection of weighting factor, which demands more computation time. This paper aims to develop modified PTC, eliminating flux weighting factor. The flux control objective is replaced by an equivalent reactive torque control. Thus making two control objectives of the same units and eliminating the requirement of flux weighting factor in cost function. Furthermore, nearest voltage vector selection strategy is introduced to limit the number of prediction voltage vectors in each sampling period. Thus, overall computational burden is reduced achieving minimum torque and flux ripples. The performance of the proposed PTC for multilevel inversion fed OEWIM is evaluated through MATLAB/Simulink simulations and experimental analysis. To highlight its benefits, these results are compared with those of the conventional and recent PTC techniques.

A Study on the Spatial Dependence of a MEMS Electromagnetic Transducer

A MEMS, silicon-based device with a piezoelectric layer and an integrated magnet is presented for magnetic to electrical transduction. The cantilever structure can be configured either as an energy harvester to harvest power from an AC power line or as an AC current sensor. The positioning of the transducer with respect to the conductor is critical in both scenarios. For the energy scavenger, correct positioning is required to optimize the harvested power. For the current sensor, it is necessary to optimize the sensitivity of the sensor. This paper considers the effect of the relative position of the transducer with respect to the wire on the resulting electromagnetic forces and torques driving the device. It is shown in this paper that it is the net equivalent torque at the anchor that must be considered and not just the vertical component of the magnetic force as has been widely assumed heretofore. We show that for single wire conductors, the commonly made assumption that there exists two symmetrical power peaks at 45° either side of the wire is untrue, but rather that the net driving torque on one side of the wire can be more than an order of magnitude greater than the other. [2018-0173]

Study on Low-Speed Steering Resistance Torque of Vehicles Considering Friction between Tire and Pavement

Electric power steering (EPS) systems under existing vehicle power systems cannot provide enough power for heavy-duty commercial vehicles under pivot or low-speed steering conditions. To solve this problem, the paper proposes an EPS system that is based on the hybrid power system constituted by the vehicle power system and the supercapacitor in parallel. In order to provide a theoretical basis for the intervention and withdrawal mechanisms of a super-capacitor in the new EPS, the law of steering resistance torque at a low or extremely low vehicle speed should be explored. Firstly, the finite element model of tire/pavement was established to conduct the simulation and calculation of the low-speed steering friction force between the tire and pavement, and to obtain the fitting expression of the equivalent steering friction coefficient with the running speed of the tire. Secondly, the expression of the steering friction torque was deduced based on the calculus theory and mathematical model of the low-speed steering resistance torque, including the steering friction torque and aligning torques, established to conduct the simulation of the equivalent resistance torque applied on a steering column under low-speed condition. Subsequently, the real vehicle experiments were carried out and comparisons of the experimental results and simulation results was performed. The consistency indicated that the model of low-speed steering resistance torque had a high accuracy. Finally, the law of low-speed steering resistance torque with a vehicle speed and steering wheel angle were analyzed according to the 3D surface plot drawn from the simulation results.

The Use of Joints Force Sensors to Determine the Collision Location and Type for an Industrial Robot

Recent advances in the development of sensors allowed to obtain robots with torque-sensitive sensors in each joint. At the moment, these sensors are used only to detect collision. This work shows the possibility of obtaining information on the collision point and it type. This information can subsequently be used to select the robot’s behavior strategy. The contact point localization is realized using two approaches: the analytical approach and machine learning. Analytical approach is based on finding point on the robot length and direction of applied external force where an equivalent torques will be the same as torques in a real robot. In the machine learning approach various learning technics were tested. For the collision type identification a classification tree was proposed that distinguish soft and hard collision, purposeful and accidental, single and continuous. The algorithm at the first stage detects presence of a collision, and if there is a collision localizes it and identify its type. The described algorithms were tested on an industrial manipulator Kuka iiwa LBR 14 R820, ground truth information about the experiments was obtained using a 3D lidar.

Reversible Swelling and Shrinking of Paramagnetic Nanoparticle Swarms in Biofluids With High Ionic Strength

A microrobotic swarm has drawn extensive attention recently, due to its potential advantages in real-time tracking and targeted delivery in vivo. Herein, we use paramagnetic nanoparticles with a diameter of 500 $\mu \text{m}$ as building blocks to investigate the reversible pattern transformation of a swarm, i.e., swelling and shrinking, in biofluids by simulation and experiments. Three kinds of biofluids, i.e., phosphate buffered saline with Tween-20, simulated body fluid (SBF), and fetal bovine serum, are used, which have much higher ionic strength (up to 0.212 mol/L) and different viscosity compared with deionized water. Our results indicate that, except for the magnetic dipole interactions and hydrodynamic effects, the electrostatic interaction also plays an important role for swarm generation and reconfiguration in biofluids. The equivalent electrostatic torques exerted between nanoparticles, induced by ions, are quantified by an analytical model and are successfully compensated by tuning applied magnetic fields. The input magnetic field has a maximum field strength of 10 mT and a maximum frequency of 40 Hz. The experimental results validate the simulation, and meanwhile, the magnetic particle swarm is capable of performing significant swelling in the biofluids. In addition, by applying rotating magnetic fields, the swelled patterns can be reversibly shrunk into more concentrated regions.

Design, development, and testing of a lightweight hybrid robotic knee prosthesis

We present a lightweight robotic knee prosthesis with a novel hybrid actuation system that enables passive and active operation modes. The proposed hybrid knee uses a spring-damper system in combination with an electric motor and transmission system, which can be engaged to provide a stair ambulation capability. In comparison to fully powered prostheses that power all ambulation activities, a hybrid knee prosthesis can achieve significant weight reduction by focusing the design of the actuator on a subset of activities without losing the ability to produce equivalent torque and mechanical power in the active mode. The hybrid knee prototype weighs 1.7 kg, including battery and control, and can provide up to 125 Nm of repetitive torque. Experiments with two transfemoral amputee subjects show that the proposed hybrid knee prosthesis can support walking on level ground in the passive mode, as well as stair ambulation with a reciprocal gait pattern in the active mode.

Self-adaptive grasp analysis of a novel under-actuated cable-truss robotic finger

This paper presents the self-adaptive grasp of a novel cable-driven finger, which is an underactuated finger comprising cable-truss units. The underactuated cable-truss finger uses tendon-pulley transmission and parallel four-linkage mechanism to realize grasps. The working principle of the underactuated cable-truss finger and the self-adaptation at the grasp-closing stage are introduced. A self-adaptive grasping model is constructed to analyze the self-adaptation, and a new analysis method that considers the position and posture of grasping point in distal phalange is proposed. A new generalized coordinate, which directly shows the contacting position and the relative angular displacement in the distal phalange, is established. The expression of general static grasping force is established by using the virtual work principle, which reveals the relationship among the driving force, the equivalent torques on joints and the grasping forces. The workspace of the underactuated cable-truss finger and distributions of grasping force in new generalized coordinate are assessed through numerical analysis. The balance conditions of the self-adaptive grasp and the corresponding statuses are theoretically illustrated. Valid and adequate self-adaptive grasping experiments are conducted to verify the accuracy of self-adaptive grasping analysis.

UNSTEADY OPERATING MODES OF THE MAIN DRIVE UNIT OF A MACHINE-TOOLS FOR SOLID RAILWAY WHEELS PROCESSING

Purpose. The paper deals with determining the conditions of the dynamic overload formation for a drive unit in the wheel-processing machine in various unsteady operating modes and suggests ways to reduce it. Methodology. The problem was solved by creating a dynamic computational multi-mass chain model followed by modeling of its loading by external force options, the values of which were obtained by analytical and experimental methods. The solution to equations of motion with determining the load of the drive unit in the transient acceleration mode and in the tie-in one was carried out by means of MathCad. Findings. The design scheme for the drive unit of the rotational movement of the machine faceplate is represented by a linear three-mass row system with two elastic connections and with three absolute degrees of freedom. The analytical determination of the cutting force moments takes into account changes in the kinematic parameters of the cutting regime when machining the different sections of the profile with cup-tip tool. The worst case of load application is accepted with simultaneous insertion of tools. The equivalent torque of the cutting forces is defined as the sum of the moments from each of the tools at multi-cut machining. The moments of elasticity of bonds in the steady state of the machine drive unit are determined. Dynamic loads with coefficients of dynamism in the bonds Kd12 = 1.13 and Kd23 = 1.04 are insignificant in the tie-in mode and rapidly decrease their value. Absolute values of the twisting elastic moment in the C23 bond in the start-up mode are insignificant and much less than the values of the steady load. Using the method of calculation and experimental research, a significant dynamic overload of the machine drive unit in the mode of rheostat start-up by a directcurrent motor was established. The reactive elastic moment with the periodic change is 2.7 times higher than the nominal moment of steady processing regime. Originality. Authors created the elastic dynamic model of the machine drive unit for the processing of railway wheels. In accordance with the model, the equations of mass motion and bond loading are compiled and solved. The theoretical conditions for reducing the drive unit loading are determined. Practical value. Based on the simulation of the transient drive start-up process, significant overloads of its elements have been determined. They are several times higher than the response of elastic bonds during cutting. To prevent this, it is recommended to change the mode of multistage starting of the engine with a decrease of the starting current by at least two times up to a value of not more than 1 200 A.