Control Systems for a Coal Mine Tunnelling Machine

Physical and mental strain at work: Relationships with onset and persistent of multi-site pain in a four-year follow up

Field-oriented control (FOC) is a widely used strategy that allows independent control of torque and flux in induction motor systems. By applying Park transforms to convert three-phase signals into a dq reference frame, accurate motor speed regulation is achieved while maintaining constant flux for optimal performance and efficiency. Traditional field-oriented control (TFOC) assumes constant rotor resistance; however, variations in this parameter can degrade control accuracy and stability. This research presents an enhanced field-oriented control (EFOC) system that effectively compensates for rotor resistance variations by directly regulating the flux vector in the dq frame, ensuring flux stability and reducing reactive power consumption. Additionally, sliding mode control (SMC) is applied to the outer and inner loops to enhance system robustness, minimise torque ripples and improve dynamic response. Simulation results confirm that the proposed EFOC maintains the flux at its nominal value under resistance changes, achieving a 20% reduction in reactive power, approximately 6% improvement in power factor and reducing torque ripples from 13 N · m −1 to 0.3 N · m −1 , demonstrating superior performance compared with conventional proportional-integral (PI)-based FOC systems.

The design of suitable control algorithms for induction motors (IM) has been widely investigated for more than two decades. Since the beginning of field oriented control (FOC) of AC drives, seen as a viable replacement of the traditional DC drives, several techniques from linear control theory have been used in the different control loops of the FOC scheme, such as Proportional Integral (PI) regulators, and exact feedback linearization (Bose, 1997, 2002; Vas, 1998). Due to their linear characteristics, these techniques do not guarantee suitable machine operation for the whole operation range, and do not consider the parameter variations of the motor-load set.

Rock slopes stability is important for personnel and equipment safety in the open-pit mine. Instability and failure of slope occur due to many factors such as unsuited slope geometry, geological discontinuities, weak slope material due to weather influences. External loads such as high rainfall and seismicity could play an essential role in slope failure. Consequently, a precise classification of rock mass is needed for the basis of determining technical policy. Rock slopes in open pit coal mining areas, especially in Indonesia, are characterized by applying various rock mass classification systems, such as Rock Mass Rating (RMR) and Geological Strength Index (GSI), because the study area comprises well-exposed rock formations. In the RMR system, there are five main parameters i.e. Rock Quality Designation (RQD), Uniaxial Compressive Strength (UCS) of rocks, discontinuity spacing, discontinuity and groundwater conditions were considered. Several rock mass classification systems developed for the assessment of rock slope stability were evaluated with the condition of rock slopes in the tropics, especially Indonesian region, particularly in sedimentary rocks in the open pit coal mining area in order to get the corrected GSI equation used to characterize rock slopes based on rock mass structure quantitative analysis and discontinuities surface conditions. This paper provides correlation between the GSI and RMR for sediment rock in coal mines.

The efficiency of control systems in permanent magnet synchronous motors (PMSM) is crucial, especially for applications in physiotherapy robots. Previous studies have demonstrated that an open-loop field-oriented control (FOC) driver using BTS7960 outperforms the commonly used electronic speed controller (ESC). This research addresses the challenge of further improving efficiency by employing a closed-loop FOC driver with the BTS7960. The research methodology involves two main stages. First, a PSIM software simulation of a closed-loop FOC using a proportional integral (PI) controller is conducted. The aim is to determine the P and I parameters that result in the smallest settling time, steady-state error, and overshoot in controlling the PMSM motor's rotation per minute (RPM). The second stage involves hardware implementation with the BTS7960, where the PMSM motor RPM is compared under various loads ranging from 10-gram to 60 gram. RPM results from both open-loop and closed-loop configurations are compared. The results show that the closed-loop FOC driver has improved system transient response compared to the previous open-loop FOC driver, notably reducing the settling time from 2.24 seconds to 1.45 seconds for a 60 gram load. Therefore, this research concludes that a closed-loop configuration with well-tuned PI parameters can deliver better performance compared to open-loop methods, as clearly demonstrated.

This paper represents a comprehensive analysis of Field-Oriented Control (FOC) technique for Permanent Magnet Synchronous Motors (PMSM) employing Space Vector Modulation (SVM) and Sinusoidal Pulse Width Modulation (SPWM). A comprehensive dynamic model of the PMSM is created, integrating mechanical dynamics and d-q axis equations to construct proportional integral (PI) controllers for speed and current management. The performance of SPWM and SVM is studied under two operational modes: constant speed and constant torque, focusing on transient response, steady-state accuracy, and harmonic distortion. The performance of both modulation strategies is evaluated using a Proportional-Integral (PI) controller designed and implemented in MATLAB/Simulink. Simulation results show that compared to SPWM, SVM achieves superior dynamic performance, with faster settling time, lower torque ripple, and improved DC bus voltage utilization. SVM reduces fluctuations in speed in the constant torque mode, but SPWM shows more harmonic distortion in the stator currents. The study underscores the importance of modulation strategy selection in optimizing PMSM drives for electric Vehicles.

Oscillation of torque and speed occurs in the electric powertrain based on permanent magnet synchronous motor under field-oriented control when we set an unreasonable proportional control parameter of proportional–integral regulator. Thus, it influences the stability and reliability of electric powertrain. The objectives of this article are to study nonlinear dynamics of electric powertrain under various complex operating conditions and settle a minimum stable range of proportional control parameter of proportional–integral regulator. To achieve these goals, nonlinear dynamic model of electric powertrain was established. Then, we solved equilibrium points and analyzed the stability of equilibrium points. Finally, we set different control parameters of proportional–integral regulator and various complex working conditions of electric powertrain to simulate nonlinear dynamics of electric powertrain. The simulation results show the electric powertrain operates stably when the control parameter is set in the area where there is only one stable equilibrium point. Chaos do exist in the electric powertrain with field-oriented control under different working conditions. Our analysis reveals the dynamics of electric powertrain are dependent on proportional control parameters of proportional–integral regulator and electric powertrain performs unstably most likely under the operating condition with no-load and zero reference rotational speed.

The authors have previously shown that field-oriented controllers for induction motors preserve stability under a wide range of variations of the motor and controller parameters. However, as is well known, the transient performance critically depends on the tuning of the gains of the proportional-integral (PI) velocity loop, a task which is rendered difficult because of the high uncertainty on the rotor resistance. The problem we address in this paper is how to develop an offline procedure to choose these gains. The main contribution of our work is a very simple frequency-domain test that, for each setting of the PI gains, evaluates the maximum range of the relative rotor resistance estimate for which global stability is guaranteed. In this way, we provide a quantitative estimate of the performance of the PI controller. The stability result may also be used in a dual manner, fixing now the range of the rotor resistance, and estimating an admissible interval for the PI gains that preserves global stability. Instrumental for our study is the exploitation of an energy dissipation (strict passivity) property of the system.

The chipping and grinding processes are the basis for understanding rock cutting during TBM excavation in hard rock conditions. The chips are produced when tensile fractures created by adjacent cutters propagate parallel to the tunnel face and coalesce whereas grinding occurs when fractures do not fully propagate through the rock and only fines are generated. Chipping is the normal and efficient boring process using machines equipped with disc cutters. Consequently, almost all of the models proposed for predicting the TBM penetration have been developed by the assumption that chipping is the dominant mode. It is obvious that these models are unable to predict correctly TBM performance when grinding is dominated in the rock cutting process. In this study, the relationships between engineering geological properties of the rock units (Cretaceous limestones) and operating and performance parameters of a refurbished EPB-TBM, employed for completion of SEL6 (the Southern Extension of Line 6, Tehran Metro) tunnel, were evaluated and analyzed. In this project due to limitations in the load capacity of the employed cutters and insufficient initial penetration in rock, the excavation was mostly carried out on grinding-dominated mode. So, the suitable data for establishing a special database and consequent analyses were provided. The established database composed of actual operating and performance parameters of the machine (i.e., cutterhead penetration and RPM and cutter load) and also engineering geological properties (i.e., UCS, alpha angle, GSI, and RQD) of limestone strata. Finally, by statistical analyses performed on collected and screened data (41 data sets), some simple, site-specific, empirical equations were developed to predict the TBM performance on grinding mode. In addition, according to the multivariate regression method, a significant relationship between the cutterhead penetration (PRev), the cutter load (Fn), intact rock strength (UCS), and geological strength index (GSI) was established, statistically. The obtained results demonstrate that this engineering geological-based model could provide a new applicable equation for accurately predicting TBM performance for similar geological conditions where grinding is dominant.

For many people it is impossible to imagine working life today without a computer. What the increase of the use of computers means for the quality of the work, is still under discussion. The object of this study is to show the recent developments (1992 - 2000) in the use of computers among the working population in the European Union and its impact on the quality of working life. The data used for these analyses were collected on a five-year basis by means of a questionnaire. Results show that the use of computers has increased between 1992 and 2000. The increase in computer use is almost completely the result of developments within white-collar occupations. In general, the use of a computer results in more qualified work and less physical strain. However, those who work with a computer permanently, clearly show more signs of physical and mental strain than those who use the computer only part of the time. This could mean that adding other tasks than computer tasks could improve the working conditions of those using the computer permanently. These results suggest that the increase of the use of computers will further improve the quality of work except when one neglects the dangers connected with a permanent use of computers.

In-depth cross-coupling analysis in high-performance induction motor control

Seismic bearing capacity of rock foundations subjected to seepage by a unilateral piece-wise log-spiral failure mechanism

The wide use of induction motors in high-precision drives calls for more advanced control architectures. Probably the greatest progress made in recent years is the field oriented control (FOC) which allowed the induction motor to move beyond the variable-speed control of Volts per Hertz drives. This work proposes the development of an adaptive neuro-fuzzy inference system (ANFIS) angular rotor speed estimator applied to a FOC sensorless drive. An innovative multi-frequency training of ANFIS is proposed initially for an volts per hertz scheme and when the best inputs of ANFIS were chosen a drive system with magnetizing flux oriented control was proposed using the ANFIS estimator. Simulations to evaluate the performance of the estimator considering the volts per hertz and vector drive system were realized using the Matlab/Simulink software. For future validation of the proposed ANFIS estimator a bench test was constructed.

<div class="section abstract"><div class="htmlview paragraph">As the automotive industry progresses towards electrification, driven by need for sustainability and reduced emissions, the traction inverter emerges as pivotal component of electric vehicles (EVs). Serving as the interface between the vehicle’s control systems, motor and battery. The traction inverter’s performance directly impacts the efficiency, sustainability and overall functionality of electric drive systems. A critical function of the traction inverter is measurement of phase currents in each motor phase, enabling precise control of the motor’s torque and rational speed. This capability is essential for optimizing efficiency, enhancing performance and ensuring safety key aspects of modern electric vehicle technology. This paper introduces method for measuring phase currents in Permanent Magnet Synchronous Motors (PMSM) utilizing the Enhanced Versitile Analog-Digital-Converter (EVADC) integrated within Infineon’s Aurix Tricore. This technology preferred for its rapid conversion speed and advanced features for synchronization and parallel sampling. This approach facilitates synchronous three phase motor current measurement at the midpoint of the Pulse Width Modulation (PWM) trigger signal. By capturing data at this critical point, we effectively eliminate current ripples, which is crucial for accurate motor control technique such as Field Oriented Control (FOC), thereby enhancing the management of torque and rotational speed. Moreover, this work adheres to redundancy principles aimed at preventing single point failures. By implementing critical safety metrics and confirmations measures (SPFM and LFM) necessary for compliance with ISO26262 standards. Redeundnacy checks on measured phase currents support error mitigation, fault detection and overall system safety. This comprehensive approach contributes to advancement of electric vehicle technology but also emphasizes the importance of robust phase current measurement techniques achieving greater reliability and efficiency in electric vehicle operation.</div></div>

Field-oriented control has made permanent magnet synchronous motor drives possible for the high performance applications. With a high-performance field oriented control system, the torque and flux producing components of the stator current are decoupled so that the independent torque and flux controls are possible as in DC motors. Thus, a high quality control of the stator current vector is essential for the successful implementation of the field-oriented control since the current controller has a direct influence on the drive performance. The current control schemes for a voltage source inverter-fed PMSM drive can be classified as hysteresis control, ramp comparison control, synchronous frame proportional-integral (PI) control, and predictive control. Among them, the predictive control is known to give a superior performance. However, this control scheme requires the information on the machine parameters and operation conditions with the sufficient accuracy, and cannot give a satisfactory response under parameter mismatch. To overcome such a limitation, the robust speed control of a PMSM using sliding mode control with load torque estimation is presented. The load disturbance is detected by the observer of an unknown and inaccessible input, and is compensated by the feedforward current. The proposed control schemes are applied to PMSM driven by a three-phase voltage-fed PWM inverter and the effectiveness is verified through the comparative simulations.