Effect Of Load Torque Research Articles

Adaptive fast terminal sliding mode control of robotic manipulators based on joint torque estimation and friction compensation

AbstractIn this work, an adaptive fast terminal sliding mode control (AFSMC) approach based on joint torque estimation and friction compensation is proposed to enhance the trajectory tracking accuracy of robotic manipulators under variable load conditions. The joint torque estimation utilizes an improved harmonic drive compliance model and adaptive low‐pass filtering, and friction compensation employs a hybrid model accounting for velocity and load torque effects. These compensations reduce the upper bound of the uncertainty, while AFSMC further reduces dependency on upper uncertainty bounds and minimizes the chattering. The stability analysis using the Lyapunov method confirms the effectiveness of this approach. Experimental results demonstrate that the proposed controller achieves smaller root mean square and maximum error of trajectory tracking, thus significantly improving trajectory tracking accuracy under variable load conditions.

Nonlinear control of coaxial double rotor magnetic gear based on high gain observer in wind turbine

AbstractThis paper proposes a nonlinear control law with a dynamic controller based on high gain observer (HGO) for a co‐axial double rotor magnetic gear (CADRMG) based on Halbach array used in wind turbines. The generalized canonical form (GCF) is used to normalize the nonlinear augmented system to achieve the dynamic control signal with a chain of integrator of system output. In addition, a tracking problem is defined to track high speed rotor (HSR) with respect to GCF. On the other hand, the HGO is used to estimate the error tracking at the expense of nonlinear terms. Furthermore, the nonlinear system observability of the augmented system is evaluated. A dynamic control law is used to solve the tracking problem based on HGO. This controller can eliminate the effect of load torque as a constant and unknown disturbance in the closed‐loop system. Moreover, the closed‐loop stability of the system under dynamic signal control is guaranteed. The system states estimation is calculated by recursive equations from tracking error estimations. Finally, numerical simulations are given to illustrate the theoretical results of proposed system.

An improved iterative approach with a comprehensive friction model for identifying dynamic parameters of collaborative robots

AbstractCollaborative robots are becoming intelligent assistants of human in industrial settings and daily lives. Dynamic model identification is an active topic for collaborative robots because it can provide effective ways to achieve precise control, fast collision detection and smooth lead-through programming. In this research, an improved iterative approach with a comprehensive friction model for dynamic model identification is proposed for collaborative robots when the joint velocity, temperature and load torque effects are considered. Experiments are conducted on the AUBO I5 collaborative robots. Two other existing identification algorithms are adopted to make comparison with the proposed approach. It is verified that the average error of the proposed I-IRLS algorithm is reduced by over 14% than that of the classical IRLS algorithm. The proposed I-IRLS method can be widely used in various application scenarios of collaborative robots.

Numerical Study on the Torsional and Lateral Vibrations of Double Universal Joint Driveline System

Utilizing a universal joint can lead to significant vibration within a driveline system. This study presents a model for analyzing the torsional and lateral vibrations of a driveline connected by a double universal joint. The governing equations of motion are derived, and the Runge-Kutta method computes steady-state responses across a spectrum of input rotational speeds. The focus is to examine the effect of system parameters, including static angular misalignment, load torque, and lateral stiffness. Relative amplification is used to analyze the effects of parameters on system vibration. Results indicated that the second-order component of input rotational speed induced by the universal joint was the factor that caused the vibrations. For the considered system, static angular misalignment significantly impacts both the torsional and lateral vibrations. Increasing the angular misalignment from 15° to 30° results in a threefold increase in lateral vibration amplification, while torsional vibration amplification is increased by nearly two times. The effect of load torque is almost linearly proportional to torsional vibration but is nonlinear to lateral vibration. Thus, lateral vibration is significantly impacted compared to torsional vibration for higher load torque. Changing the stiffness leads to a modification of the natural frequency. Increasing the lateral stiffness shifts the critical speed to a higher speed range, resulting in reduced lateral vibration amplitude. It is demonstrated that a slight fluctuation in angular misalignment due to lateral vibration will not affect the torsional vibration even if both vibrations are coupled. The findings may enhance understanding of how changing system parameters affects vibration.

Design and Implementation of a Novel Intelligent Strategy for the Permanent Magnet Synchronous Motor Emulation

In this paper, an intelligent neural network‐based controller is designed and implemented to control the speed of a permanent magnet synchronous motor (PMSM). First, the exact mathematical model of PMSM is presented, and then, by designing a controller, we apply the wind turbine emulation challenges. The designed controller for the first time is implemented on a Arm Cortex‐M microcontroller and tested on a laboratory PMSM. Since online learning neural network on a chip requires a strong processor, high memory, and convergence guarantee, this article uses the offline method. In this method, first, for different work points, the neural network is trained by local controllers, and then, the trained network is implemented on the chip and used. Uncertainty in the parameters and the effect of load torque as challenges of control systems are applied in the proposed method, and a comparison with other methods is performed in the implementation results section.

IPMSM Speed and Current Controller Design for Electric Vehicles Based on Explicit MPC

The difficulties in implementing the model predictive control (MPC) in interior permanent-magnet synchronous motors (IPMSMs) consist of the nonlinear behavior of IPMSMs and the computational effort required by MPC. This paper presents an IPMSM controller design method for electric vehicles based on explicit MPC (EMPC), which uses a different linearization method. The proposed controller combines the speed and current controllers and replaces the traditional cascade structure. First, the nonlinear terms in the system model are added into the control input as voltage compensation to obtain a simple linear model. Next, the proposed controller based on MPC is designed, which considers the effects of load torque and uses an increment model. Furthermore, the controller applies both current and voltage constraints. The EMPC method based on a binary search is used to accelerate the solution of the optimization problem. Finally, the simulation results show the validity and superiority of the proposed method.

Disturbance Observer Based Robust Sliding Mode Control of Permanent Magnet Synchronous Motor

This paper addresses speed control of permanent magnet synchronous motor under load torque perturbations. The mathematical model is derived using park’s transformation. The load torque disturbance is considered unknown bounded, and states variables are available in feedback. In order to achieve robust speed performance, sliding mode control (SMC) is introduced. However, it is noted that conventional SMC does not provide satisfactory performance under load torque disturbances. To end this, a novel control strategy called disturbance observer SMC (DOSMC) is formulated. It includes an observer that offers a tool to vanish the effect of load torque. The DOSMC technique has two distinguished characteristics: first, the design gains are needed to be greater than the maximum limit of disturbance estimation error instead of disturbances, second; the proposed observer estimates load disturbances and provide a compensator to update sliding surface and control input. The stability analysis of overall control system is verified using Lyapunov theorem. Simulations in MATLAB/Simulink proves efficacy of the proposed scheme.

Effective damping of the torsional vibrations of the drive system with an elastic joint based on the forced dynamic control algorithms

The paper aims to present the novel control structures for a drive system with an elastic connection. Two control structures based on forced dynamic control (FDC) laws are investigated. The first one is based on the state controller approach, the second one on cascade methodology. These two approaches ensure different dynamic properties of the drive system. In the first approach, called full-FDC, the ability to remove the effect of the load torque from the load speed is assured, but the shaft torque cannot be directly limited. In the second approach the possibility of fast elimination of the load torque effect is limited, yet the shaft torque can be fully controlled. The detailed design methodology of both control structures is presented in the paper. Their properties are analyzed through simulation and experimental studies.

Study of the Effect of Load Torque on the Iron Losses of Permanent Magnet Motors by using Finite Element Analysis

Study of the Effect of Load Torque on the Iron Losses of Permanent Magnet Motors by using Finite Element Analysis

Impact analysis and vibration reduction design of spiral bevel gears

To minimize the running vibration of spiral bevel gear, an optimization design method for vibration control is presented with the model of meshing impact. Firstly, based on the impact model of spiral bevel gears considering tooth deformation, the initial meshing position, meshing stiffness, and the meshing impact is studied. Secondly, the effects of load torque and rotation speed on meshing impact are analyzed. Thirdly, a mathematical model for pinion generator is built with following parameters: tool parameters, initial machine settings, and polynomial coefficients of auxiliary flank modification motion. The polynomial coefficients of the auxiliary flank modification motion are determined by optimizing the minimum impact velocity. Finally, a numerical simulation is performed. The results shows that load torque and pinion rotational speed impose significant influences on the impact. The impact velocity increases with the increase of load torque and pinion rotation speed. With load torque increasing, impact force tends to increase first and then decrease because of meshing stiffness changes, finally impact force increases dramatically due to additional load. The advantages of spiral bevel gear under the optimization of impact velocity in meshing impact are obviously. The accuracy and scientificity of the method presented in the paper for calculating the initial meshing point and meshing stiffness of complicated tooth surfaces is verified. The optimized gear obtained by the optimization method presented in the paper is also proved that owns the lowest meshing impact in the design load range. The proposed optimization method can reduce meshing impact and improve the dynamic meshing performance of spiral bevel gear. This method also can be used for optimum design of other types of gears.

Neural Network Based Control of a Two-Mass Drive System

In this paper, two-mass drive system is modelled and speed control of the two-mass system is presented. The speed control of the system offers the challenge due to handle torsional vibrations. In the control structure, Particle Swarm Optimization (PSO) based conventional Proportional-Integral-Derivative (PID) controller and single-layer, feed-forward Neural Network controller with back-propagation learning algorithm are proposed. NN control is investigated to show the effectiveness of the control performance compared with the designed PID control. In order to have a fair comparison, PSO method is used to determine the optimum PID parameters and NN controller is designed with online learning algorithm. In the NN learning, back-propagation, which is the most preferred method, is adapted. Simulation studies are performed in different two parts to examine the performance of the proposed controller. In the first part, the controllers are tested for different step references and comparative results of the optimized PID and NN controllers are illustrated. In the second part, the effect of load torque is explored with proposed NN control method. According to the obtained simulation results, it can be seen that the designed NN controller provides better performances without and with load speeds.

Analysis on Load Torque Effect for Assistive Robotic Arms

Analysis on Load Torque Effect for Assistive Robotic Arms

Optimization methodology for coasting operating point of high-speed train for reducing power consumption

As an effective way to reduce power consumption, coasting has been widely used during the operation of high-speed train. However, as a typical electromechanical coupling system, the different speed of inert point may lead to complex dynamic behavior of high-speed train and affect the safety operation. Based on this, this paper proposes an optimization methodology of the coasting point to simultaneously ensure the safety operation and energy saving of the train. A mathematical model of permanent magnet synchronous motor (PMSM) during coasting is established, and the local stability and bifurcation conditions are derived based on Routh-Hurwitz criterion and the bifurcation theory. And the influence of load torque variation on bifurcation characteristics of equilibrium point and stable operation domain of the system is studied. Moreover, detailed numerical simulations are carried out to analyze the effect of load torque on the coasting point, and an optimization methodology is proposed. Experimental platform is set up to verify the correctness and the effectiveness of the proposed optimization methodology. The results show that the variation of the motor parameters may the occurrence of Fold and Hopf bifurcations, and the increase of load torque may change the bifurcation characteristics and lead the system to transit into a chaotic state and lose stability. The experimental results show that the optimization method proposed in this paper can effectively reduce the energy consumption by 7.7 percent.

A contact model of traveling-wave ultrasonic motors considering preload and load torque effects

A contact model of traveling-wave ultrasonic motors considering preload and load torque effects

Multi- objective optimization of switched reluctance motor drive in electric vehicles

Switched reluctance drive (SRD) has become one of the best choices for electric vehicle drive because it exhibits prominent advantages over other kinds of electric drive system. In this paper, the effects of load torque, turn-on and turn-off angle on the torque ripple and electric efficiency of the SRD are thoroughly analyzed based on the nonlinear dynamic model of switched reluctance motor (SRM). To reduce the torque ripple and improve the electric efficiency, a novel double-index synchronous optimization policy is proposed. Under different load torques and speeds, the model of adjustable turn-on and turn-off angle is established using the proposed optimization policy. Compared with conventional optimization strategies, the proposed method is verified to be effective for torque ripple suppression and electric efficiency improvement of the SRD simultaneously.

Comparative investigation of diagnosis media for induction machine mechanical unbalance fault

For an induction machine, we suggest a theoretical development of the mechanical unbalance effect on the analytical expressions of radial vibration and stator current. Related spectra are described and characteristic defect frequencies are determined. Moreover, the stray flux expressions are developed for both axial and radial sensor coil positions and a substitute diagnosis technique is proposed. In addition, the load torque effect on the detection efficiency of these diagnosis media is discussed and a comparative investigation is performed. The decisive factor of comparison is the fault sensitivity. Experimental results show that spectral analysis of the axial stray flux can be an alternative solution to cover effectiveness limitation of the traditional stator current technique and to substitute the classical vibration practice.

Effect of load torque on the stability of overhung rotors

The dynamic stability of overhung flexible rotors subjected to load torques has been studied analytically. Other factors, such as external damping, distributed shaft mass, and gyroscopic moments, are considered. For the analyses, the transfer matrix is developed to include the effect of the applied torque and then integrated into a computer program to investigate the stability of overhung rotor systems under both tangential and axial load torques. Two overhung rotor systems are considered: the cantilevered rotor and the overhung rotor with an intermediate support. The ratio of the load torque to the damping for the stability is presented for the various locations of the intermediate supports. It was found that stability depends strongly on both the mode shape and the dimensionless torque to damping ratio.

Motion control of the 2-DOF parallel manipulator of a hybrid machine tool

SUMMARYThis paper focuses on the motion control of the two-degree-of-freedom (2-DOF) planar parallel manipulator of a hybrid machine tool. On the basis of the performance analysis of the kinematic control system, a parameter-tuning method is proposed for regulating the control parameters. To improve the response performance, the proportional-derivative control and a low-pass filter are introduced to the position-loop controller. The simulation shows that the response speed is increased and that the tracking error is reduced. Furthermore, the effect of load torque on the contour error is investigated, and the dynamic feedforward control is used to control the parallel manipulator. On the basis of the principle of dual-channel compensation, the feedforward compensator is designed. The simulations, that the moving platform moves along a linear trajectory and circular trajectory, show that the dynamic feedforward control can reduce the effect of load torque on contour error.

Multiharmonic Adaptive Vibration Control of Misaligned Driveline via Active Magnetic Bearings

Active magnetic bearings (AMBs) have been proposed by many researchers and engineers as an alternative to replace traditional contact bearings in rotor and driveshaft systems. Such active, noncontact bearings do not have frictional wear and can be used to suppress vibration in sub- and supercritical rotor-dynamic applications. One important issue that has not yet been addressed by previous AMB-driveline control studies is the effect of driveline misalignment. Previous research has shown that misalignment causes periodic parametric and forcing actions, which greatly impact both driveline stability and vibration levels. Therefore, in order to ensure closed-loop stability and acceptable performance of any AMB controlled driveline subjected to misalignment, these effects must be accounted for in the control system design. In this paper, a hybrid proportional derivative (PD) feedback/multiharmonic adaptive vibration control (MHAVC) feedforward law is developed for an AMB/U-joint-driveline system, which is subjected to parallel-offset misalignments, imbalance, and load-torque operating conditions. Conceptually, the PD feedback ensures closed-loop stability while the MHAVC feedforward suppresses steady-state vibration. It is found that there is a range of P and D feedback gains that ensures both MHAVC convergence and closed-loop stability robustness with respect to shaft internal damping induced whirl and misalignment effects. Finally, it is analytically and experimentally demonstrated that the hybrid PD-MHAVC law effectively adapts to and suppresses multiharmonic vibration induced by imbalance, misalignment, and load-torque effects at multiple operating speeds without explicit knowledge of the disturbance conditions.

Load Torque Effects on the Critical Speeds of a Continuous Rotor

The paper deals with the influence of the load torque on the critical velocities of a shaft mounted on short bearings. While in most works on this subject the load torque is taken as axial, it is shown here that, provided the external torque does not change its initial direction as the shaft is deformed and is applied through an ideal spherical coupling—the assumption of a semitangential mode is the correct one. Revised values of the critical torques and velocities are calculated accordingly and compared to those based on the conventional assumption.