Stable Control Performance Research Articles

Stability control for end effect of mobile manipulator in uneven terrain based on active disturbance rejection control

Purpose When the mobile manipulator is traveling on an unconstructed terrain, the external disturbance is generated. The load on the end of the mobile manipulator will be affected strictly by the disturbance. The purpose of this paper is to reject the disturbance and keep the end effector in a stable pose all the time, a control method is proposed for the onboard manipulator. Design/methodology/approach In this paper, the kinematics and dynamics models of the end pose stability control system for the tracked robot are built. Through the guidance of this model information, the control framework based on active disturbance rejection control (ADRC) is designed, which keeps the attitude of the end of the manipulator stable in the pitch, roll and yaw direction. Meanwhile, the control algorithm is operated with cloud computing because the research object, the rescue robot, aims to be lightweight and execute work with remote manipulation. Findings The challenging simulation experiments demonstrate that the methodology can achieve valid stability control performance in the challenging terrain road in terms of robustness and real-time. Originality/value This research facilitates the stable posture control of the end-effector of the mobile manipulator and maintains it in a suitable stable operating environment. The entire system can normally work even in dynamic disturbance scenarios and uncertain nonlinear modeling. Furthermore, an example is given to guide the parameter tuning of ADRC by using model information and estimate the unknown internal modeling uncertainty, which is difficult to be modeled or identified.

Advances in Fault Diagnostics and Post‐Fault Operation of Electrical Drives

Advances in Fault Diagnostics and Post‐Fault Operation of Electrical Drives

반도체 제조공정용 약액 유량 제어장치의 제어 반응속도 개선

Equipment used in the semiconductor manufacturing process generally have a flow rate control system for each nozzle to regulate the flow rate of chemical solution fed to the wafer. In existing flow rate control systems, flow rate overshoots occur because of excess pressure and the control rates of the overshoots are less because additional operation time is required for the electric valves. In this study, to address the shortcomings of existing flow rate control systems, we proposed a method to improve the speed of flow rate control by introducing a constant pressure valve. The constant pressure valve controls the flow path via gas pressure, thereby facilitating prompt control and efficiently improving the flow rate overshoot caused by the pressure overshoot. To improve the control speed and control stability of the constant pressure valve, a three-step automatic control speed application function was developed, and the measured valve, control amount mapping function, and pre-open function were defined to reduce the initial control speed. The experimental results showed a measurement precision within 1% of the target flow rate and stable control performance as well as control speed reduction from 3 seconds in existing systems to 2 seconds or less for the proposed system.

Cascade control for heterogeneous multirotor UAS

PurposeDespite of the numerous characteristics of the multirotor unmanned aircraft systems (UASs), they have been termed as less energy-efficient compared to fixed-wing and helicopter counterparts. The purpose of this paper is to explore a more efficient multirotor configuration and to provide the robust and stable control system for it.Design/methodology/approachA heterogeneous multirotor configuration is explored in this paper, which employs a large rotor at the centre to provide majority of lift and three small tilted booms rotors to provide the control. Design provides the combined characteristics of both quadcopters and helicopters in a single UAS configuration, providing endurance of helicopters keeping the manoeuvrability, simplicity and control of quadcopters. In this paper, rotational as well as translational dynamics of the multirotor are explored. Cascade control system is designed to provide an effective solution to control the attitude, altitude and position of the rotorcraft.FindingsOne of the challenging tasks towards successful flight of such a configuration is to design a stable and robust control system as it is an underactuated system possessing complex non-linearities and coupled dynamics. Cascaded proportional integral (PI) control approach has provided an efficient solution with stable control performance. A novel motor control loop is implemented to ensure enhanced disturbance rejection, which is also validated through Dryden turbulence model and 1-cosine gust model.Originality/valueRobustness and stability of the proposed control structure for such a dynamically complex UAS configuration is demonstrated with stable attitude and position performance, reference tracking and enhanced disturbance rejection.

Screening High-Temperature Foams with Microfluidics for Thermal Recovery Processes

Thermal recovery processes, and in particular, Steam-assisted gravity drainage (SAGD), are the most common and practical in situ technology for bitumen extraction. While SAGD is effective, steam injection results in poor steam chamber growth and distribution with poor conformance specifically in areas with poor formation geology and bedding properties. These factors result in economic and environmental costs. Co-injecting foaming surfactants with noncondensable gases along with steam is an alternative solution to control the steam chamber behavior and its advancement throughout the formation. Selecting appropriate foaming surfactants is essential for successful implementation of a foam-steam processes. Conventional laboratory methods provide some indication of foaming surfactant performance but fail to reflect reservoir conditions and time scales. Microfluidics is well suited to assess the relevant pore-scale performance of foaming surfactants, at relevant conditions, with tight control over experimental parameters. Here, we develop a microfluidic approach to generate nitrogen-foam and assess stability and mobility control performance at relevant temperature (>150 °C) with results compared to those of traditional bulk foam analysis. The microconfinement associated with porous media creates more stable foam at reservoir-relevant temperatures and pressures. Direct visualization of the foaming dynamics, subsequent stability, and mobility testing in porous media provide a rapid assessment of foam performance as well as a diagnostic of surfactant product failures such as precipitation and phase decomposition, findings that directly informed pilot operations here. This screening also enables down-selection of the most promising agents for subsequent testing with candidate reservoir oil, in conventional cores or micromodels.

Simple current sensor fault‐tolerant control strategy for switched reluctance motors in high‐reliability applications

Switched reluctance motors (SRMs) are considered as a potential candidate in many high-reliability demanding applications, including electrical vehicles (EVs), hybrid EVs and more electric aircrafts. For precise and stable control performance, normally an SRM drive requires one current sensor for each phase winding. Failure of any of these sensors will inevitably degrade the system's performance. The behaviour of an SRM drive under current sensor failure is investigated and a fault-tolerant control technique is proposed by changing the current sensor installation scheme without adding extra current sensors. Moreover, through the analysis of the detected currents by the phase current sensors and the dc-link sensor, a diagnostic scheme for current sensors failure is presented. The excitation current in the faulty phase under postfault conditions is reconstructed through a simple calculation without injecting a high-frequency signal or modifying the switching signals, thereby reducing the current distortion and avoiding voltage penalty issues. Motor drive can operate with satisfactory control performance even when all the phase current sensors are in fault conditions. Detailed analysis under both steady state and dynamic conditions through thorough simulations and experiments has been carried out on a three-phase 12/8 SRM. The extensive results validate the effectiveness of the proposed technique.

Model reduction techniques for high-rise buildings andits reduced-order controller with an improved BT method

An AMD control system is usually built based on the original model of a target building. As a result, the fact leads a large calculation workload exists. Therefore, the orders of a structural model should be reduced appropriately. Among various model-reduction methods, a suitable reduced-order model is important to high-rise buildings. Meanwhile, a partial structural information is discarded directly in the model-reduction process, which leads to the accuracy reduction of its controller design. In this paper, an optimal technique is selected through comparing several common model-reduction methods. Then, considering the dynamic characteristics of a high-rise building, an improved balanced truncation (BT) method is proposed for establishing its reduced-order model. The abandoned structural information, including natural frequencies, damping ratios and modal information of the original model, is reconsidered. Based on the improved reduced-order model, a new reduced-order controller is designed by a regional pole-placement method. A high-rise building with an AMD system is regarded as an example, in which the energy distribution, the control effects and the control parameters are used as the indexes to analyze the performance of the improved reduced-order controller. To verify its effectiveness, the proposed methodology is also applied to a four-storey experimental frame. The results demonstrate that the new controller has a stable control performance and a relatively short calculation time, which provides good potential for structural vibration control of high-rise buildings.

Stability Assessment of Current Controller with Harmonic Compensator for LCL-Filtered Grid-Connected Inverter under Distorted Weak Grid

An assessment of the stability and performance of current controllers with harmonic compensators is presented for an inductive-capacitive-inductive (LCL)-filtered grid-connected inverter under distorted weak grid conditions. By using two typical current control schemes which are the direct current controller with the capacitor current-based active damping and integral-resonant state feedback current controller, the closed-loop system stability and current control performance are investigated in the presence of both uncertain grid impedance and distorted grid. Even though the controller stability has been investigated under weak grid in several studies, the stability assessment of the entire current control scheme, including the harmonic resonant controllers, still needs a further comprehensive investigation. The system stability is analyzed by obtaining the movement of the closed-loop poles in the discrete-time domain when the grid impedance varies. To fully study the impact of distorted weak grid condition on the LCL filters, three LCL filter parameter sets giving the resonance frequency in different frequency bands are chosen for the purpose of evaluating the system robustness and grid-injected current quality. In order to support the presented theoretical analyses, comprehensive simulation and experimental results based on 32-bit DSP TMS320F28335 to control 2 kVA grid-connected inverter are presented in terms of grid current quality and control stability in the environment of both uncertain grid impedance and distorted grid.

Global event-triggered inner–outer loop stabilization of under-actuated surface vessels

An event-triggered controller (ETC) for global full-state stabilization of under-actuated surface vessels (USVs) is proposed. Based on an inner–outer loop structure with Lyapunov control design technique, the USV dynamics are separated into two subsystems to facilitate the design and stability analysis. A time-varying variable is constructed to design the desired velocities used as virtual control inputs to stabilize the under-actuated outer loop subsystem. For the fully-actuated inner loop subsystem, the actual control force and moment inputs are designed using a switching threshold event-triggering mechanism (SWT-ETM) to drive the actual velocities to the desired ones, thereby the inner loop subsystem and the closed-loop system are stabilized. The proposed ETC guarantees global asymptotical convergence of the stabilization error by choosing proper control parameters. It also significantly reduces the times for communication and the actuator burden while provides stable and accurate control performance. Simulation results are carried out to illustrate the effectiveness of the proposed scheme.

Modeling and Predictive Control of Shipboard Hybrid DC Power Systems

Although onboard dc power systems bring values for the power and propulsion system of the future hybrid ships, the main barrier for the development of such systems for large-scale vessels is the technical operational issues, such as stability and power quality and how to satisfy the related standards and regulations. In the advanced ship power systems, the conventional diode rectifiers are being replaced with active front-end (AFE) rectifiers providing the control flexibility but at a higher cost. However, to make such devices more profitable, the ship control system can be reconfigured to unlock the potentials of AFEs for the general system stability. This article is dealing with the stability issue of hybrid dc power systems proposing a predictive control approach to improve the voltage regulation and better use of converters. The proposed method replaces the conventional direct power control (DPC) of AFE rectifiers with a model predictive control (MPC) and integrates the dc-dc converters in the same control platform. In this method, optimal control commands for the rectifiers and the dc-dc converter are calculated by the predictive control to minimize the dc bus voltage fluctuations, especially under the fast load changes. The controller is then extended to regulate the load sharing between the different energy units. The effectiveness of the proposed method is evaluated in simulation with a typical shipload profile, as well as a real ship profile, which has several operating modes, such as steep load increase & decrease, high speed, and maneuvering operation. The performance of the proposed control strategy is compared with conventional controllers, and the results show that the new method can provide significant advantages in terms of fast and stable control performance, as well as the steady-state voltage regulation and enhancing the power smoothing function of the battery. Laboratory experimental data are also used for validation.

Linearizing Control of a Distributed Actuation Magnetic Bearing for Thin-Walled Rotor Systems

This paper describes an exact linearizing control approach for a distributed actuation magnetic bearing (DAMB) supporting a thin-walled rotor. The radial DAMB design incorporates a circular array of compact electromagnetic actuators with multi-coil winding scheme optimized for supporting thin-walled rotors. A distinguishing feature is that both the x and y components of the radial bearing force are coupled with all four of the supplied coil currents and so a closed form solution for the linearizing equations cannot be obtained. To overcome this issue, a gradient-based root-finding algorithm is proposed to solve the linearizing equations numerically in real-time. The proposed method can be applied with any chosen constraints on current values to achieve low RMS values while avoiding zero-current operating points. The approach is implemented and tested experimentally on a rotor system comprising two radial DAMBs and a uniform cylindrical shell rotor. The results show that the method achieves more accurate reproduction of demanded bearing forces, thereby simplifying the rotor suspension control design and providing improved stability and vibration control performance compared with implementations based on operating point linearization.

Adaptive Sliding Mode-Based Lateral Stability Control of Steer-by-Wire Vehicles With Experimental Validations

In this paper, a robust adaptive sliding mode (ASM) controller for improving vehicle maneuverability and lateral stability of steer-by-wire (SBW) vehicles. The proposed stability control algorithm is composed of the following three remarkable characteristics: 1) As the vehicle sideslip angle which is very useful in vehicle stability control is often unavailable or unmeasurable for practical applications, a sliding mode-based state observer is proposed to online estimate the actual sideslip angle via the yaw rate and the lateral acceleration measurements. 2) ASM lateral stability controller, as an upper level controller, is designed to calculate the corrected steering angle for driving both the yaw rate and the sideslip angle to achieve their desired values in the presence of modelling uncertainties and external disturbances. Moreover, an adaptive law is incorporated in the control law to estimate the switching gain such that the complex uncertainty bound information can be avoided. 3) The desired steering angle is realized by a lower steering controller via ASM for an SBW system. The hardware-in-the-loop simulation results demonstrate the excellent stability control performance of the proposed control for different steering maneuvers.

A Human-Vehicle Game Stability Control Strategy Considering Drivers’ Steering Characteristics

In order to explore the nature of the human-vehicle game problem and analyze the torque-angle interaction between the two agents, i.e. the driver and advanced driver assistance system (ADAS), a human-vehicle game stability control strategy based on Nash negotiation principle is proposed. First a six-order vehicle dynamic model, a driver neuromuscular (NMS) model, etc., are set up to simulate drivers’ steering characteristics and vehicles’ response to the input of the two agents and external disturbance. Secondly, several significant parameters in NMS model are recognized, and an active rear steering (ARS) controller is designed using the sliding mode variable structure algorithm. Then, the Nash negotiation solution is worked out according to Nash negotiation principle, and a self-tuning method for the weight of ARS controller is put forward employing the fuzzy control theory. Finally simulations are carried out under the standard double-lane change maneuver. The results indicate that the stability control strategy proposed in this paper can effectively solve the game problem and achieve good vehicular stability control performance.

Path tracking framework synthesizing robust model predictive control and stability control for autonomous vehicle

This paper proposes a framework for path tracking under additive disturbance when a vehicle travels at high speed or on low-friction road. A decoupling control strategy is adopted, which is made up of robust model predictive control and the stability control combining preview G-vectoring control and direct yaw moment control. A vehicle-road model is adopted for robust model predictive control, and a robust positively invariant set calculated online ensures state constraints in the presence of disturbances. Preview G-vectoring control in stability control generates deceleration and acceleration based on lateral jerk, later acceleration, and curvature at preview point when a vehicle travels through a cornering. Direct yaw moment control with additional activating conditions provides an external yaw moment to stabilize lateral motion and enhances tracking performance. A comparative analysis of stability performance of stability control is presented in simulations, and furthermore, many disturbances are considered, such as varying wind, road friction, and bounded state disturbances from motion planning and decision making. Simulation results show that the stability control combining preview G-vectoring control and direct yaw moment control with additional activating conditions not only guarantees lateral stability but also improves tracking performance, and robust model predictive control endows the overall control system with robustness.

Comparison of the Effect of Different Physical Therapy Methods on Lumbopelvic Stability among People with Low Back Pain

Research background. The majority of persons suffer from low back pain and prevalence of it seeks about 84%. Chronic low back pain is the second cause for people to go to their general practitioner. Many studies are done about treatment of chronic low back pain; however, complaints about back pain are increasing. Therefore we are going to find out which of the three our applied methods is the best for treating low back pain. The aim of the study was to compare the impact of different physical therapy methods on lumbopelvic stability control among people with chronic low back pain. Methods. 30 people with low back pain were participating in this study. Following factors were estimated before and after eight physical therapy sessions: intensity of pain by using the scale of numbers (SAS); lumbopelvic stability control by using “Stabilizer” pressure biofeedback unit; functional motions performance capacity by doing functional tasks. Results. Statistically significant changes were not found after the evaluation of lumbopelvic stability control under the method of Redcord sliding suspension system, elastic resistance and body weight exercises before and after physical therapy sessions. Statistically significant correlations were found between lumbopelvic stability control and pain intensity in those groups where people were training under the methods of elastic resistance and body weight exercises (p < 0.05). Statistically significant correlations were found between lumbopelvic stability control and functional motions performance capacity in those groups where people were training under the methods of Redcord sliding suspension system and body weight exercises (p < 0.05). Conclusion: statistically significant change was not found between three intervention groups after physical therapy; therefore neither of three methods applied in this study was better than the others.Keywords: chronic low back pain, lumbopelvic stability control, functional movement performance capacity, physical therapy.

Robust motion control for multi-split transmission line four-wheel driven mobile operation robot in extreme power environment

PurposeIn the multi-splitting transmission lines extreme power environment of ultra-high voltage and strong electromagnetic interference, to improve the trajectory tracking and stability control performance of the robot manipulator when conduct electric power operation, and effectively reduce the influence of disturbance factors on the robot motion control, this paper aims to presents a robust trajectory tracking motion control method for power cable robot manipulators based on sliding mode variable structure control theory.Design/methodology/approachThrough the layering of aerial-online-ground robot three-dimensional control architecture, the robot joint motion dynamic model has been built, and the motion control model of the N-degrees of freedom robot system has also been obtained. On this basis, the state space expression of joint motion control under disturbance and uncertainty has been also derived, and the manipulator sliding mode variable structure trajectory tracking control model has also been established. The influence of the perturbation control parameters on the robot motion control can be compensated by the back propagation neural network learning, the stability of the controller has been analyzed by using Lyapunov theory.FindingsThe robot has been tested on a analog line in the lab, the effectiveness of sliding mode variable structure control is verified by trajectory tracking simulation experiments of different typical signals with different methods. The field operation experiment further verifies the engineering practicability of the control method. At the same time, the control method has the remarkable characteristics of sound versatility, strong adaptability and easy expansion.Originality/valueThree-dimensional control architecture of underground-online-aerial robots has been proposed for industrial field applications in the ubiquitous power internet of things environment (UPIOT). Starting from the robot joint motion, the dynamic equation of the robot joint motion and the state space expression of the robot control system have been established. Based on this, a robot closed-loop trajectory tracking control system has been designed. A robust trajectory tracking motion control method for robots based on sliding mode variable structure theory has been proposed, and a sliding mode control model for the robot has been constructed. The uncertain parameters in the control model have been compensated by the neural network in real-time, and the sliding mode robust control law of the robot manipulator has been solved and obtained. A suitable Lyapunov function has been selected to prove the stability of the system. This method enhances the expansibility of the robot control system and shortens the development cycle of the controller. The trajectory tracking simulation experiment of the robot manipulator proves that the sliding mode variable structure control can effectively restrain the influence of disturbance and uncertainty on the robot motion stability, and meet the design requirements of the control system with fast response, high tracking accuracy and sound stability. Finally, the engineering practicability and superiority of sliding mode variable structure control have been further verified by field operation experiments.

Robust LMI-Based H-Infinite Controller Integrating AFS and DYC of Autonomous Vehicles With Parametric Uncertainties

Autonomous vehicles’ dynamics stability control is one key issue to ensure safety of self-driving. However, vehicle uncertainties and time-varying parameters could weaken the performance of autonomous vehicle stability control. Therefore, this article proposes a novel robust linear matrix inequality (LMI)-based <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$H$ </tex-math></inline-formula> -infinite feedback algorithm for vehicle dynamics stability control, and this algorithm controls vehicle steering system and brake system via direct yaw moment control (DYC) and active front steering control (AFS). The presented controller is robust against vehicle parametric uncertainties, including the vehicle mass and vehicle longitudinal velocity. A linear parameter varying lateral model is constructed utilizing polytopic uncertainty method considering time-varying vehicle longitudinal velocity and mass, where a polytope that contains finite vertices is established to contain all of the possible selections for uncertainty parameters. Then, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$H$ </tex-math></inline-formula> -infinite feedback controller integrating DYC and AFS is derived via LMI technique. Finally, experimental results based on hardware-in-the-loop (HIL) platform illustrate that the presented controller has better performance of ensuring autonomous vehicle dynamics stability than other controllers.

Integrated energy-oriented lateral stability control of a four-wheel-independent-drive electric vehicle

Improving the energy efficiency of an electric vehicle (EV) is an effective approach to extend its driving range. This paper proposes an integrated energy-oriented lateral stability controller (IESC) for a four-wheel independent-drive EV (4WID-EV) to optimize its energy consumption while maintaining vehicular stability during cornering. The IESC is a hierarchical controller with two levels. The high-level decision-making controller determines the virtual control inputs, i.e., the desired additional yaw moment and total wheel torque, while the low-level controller allocates the motor torques according to the virtual control inputs. In the high-level controller, the desired additional yaw moment is first calculated using a linear quadratic regulator (LQR) to minimize the control expenditure. Meanwhile, a stability weighting factor (SWF) based on phase plane analysis is proposed to adjust the additional yaw moment, which can reduce the additional energy consumption caused by the mismatch between the reference model and the actual vehicle. In addition to the yaw moment, the desired total wheel torque is calculated using a proportional-integral (PI) controller to track the desired longitudinal velocity. In the low-level controller, a multi-objective convex-optimization problem is established to optimize the motor torque by minimizing the energy consumption and considering the tire-road frictional limit and motor saturation. A globally optimal solution is obtained by using an active-set method. Finally, double-lane change (DLC) simulations are conducted using CarSim and MATLAB/Simulink. The simulation results demonstrate that the proposed controller achieves great lateral stability control performance and reduces the energy consumption by 5.23% and 2.95% compared with the rule-based control strategy for high- and low-friction DLC maneuvers, respectively.

Analysis and Suppression of Slotting and Cross-Coupling Effects on Current Control in PM Synchronous Motor Drives

This paper proposes a d–q cross-coupling current controller for permanent magnet synchronous motor (PMSM) drives. Slotting and cross-coupling effects in PMSMs cause the effective air-gap length to vary with the rotor angle and distort the distribution of the air-gap flux. Such distortions have a significant influence on the current control by changing the relationship between the stator currents and voltages. To investigate their effects, a d–q model is established in this paper, which is suitable for describing the voltage characteristics of the actual PMSMs. The model contains the angle-dependent parameters, the cross-coupling inductance between d–q axes, and the q -axis permanent magnet flux linkage, unlike the ideal d–q model. The transfer function matrix from the d–q currents to d–q voltages of PMSM is newly derived from the model. Based on that, the current controller with the feedback and feedforward terms of 2-by-2 matrix is proposed. It is designed so that the independent gains are in low-pass filter forms and the coupling control gains are zero with eliminating interference between d–q axes. The proposed controller contributes to providing the stable control performance by canceling the slotting and cross-coupling effects. The performance of the proposed current controller is verified by experimental results.

Model Predictive Adaptive Constraint Tracking Control for Underwater Vehicles

In this article, in order to solve the trajectory tracking control problem with the drive saturation (thrust overrun) for the 4500-m human occupied vehicle named “Deep-sea Warrior,” a model predictive adaptive constraint control strategy is put forward. The proposed control strategy mainly consists of two controllers. The first part is a kinematics controller designed by quantum-behaved particle swarm optimization model predictive control method. The second part is a dynamic controller designed by an adaptive algorithm. In order to study the effect of the ocean current disturbance on tracking controller, the ocean current is incorporated into the kinematics and dynamics model of the 4500-m human occupied vehicle. The thrusts of four degrees of freedom under the ocean current are calculated from designed controllers. Then, the thrusts are assigned to six thrusters on the 4500-m human occupied vehicle according to its thruster arrangement. An ocean current observer based on artificial fish proportional-integral control is designed for unknown currents. The simulation results of tracking control in three-dimensional underwater environment are given, which illustrates that the proposed control strategy can not only meet the hardware requirements (drive saturation) but also achieve a stable and efficient tracking control performance because of its constraint to speed and speed increment, the effect of the ocean current on kinematics and dynamics models and the dual feedback mechanism.