Nonlinear air-to-fuel ratio and engine speed control for hybrid vehicles

Internal combustion spark ignition engine management systems regulate the fuel, spark, and idle air subsystems to achieve sufficient engine performance at acceptable fuel economy and tailpipe emission levels. Engine control units also monitor other engine processes, using a suite of sensors, and periodically check the system actuators' operation to satisfy legislated onboard diagnostics. The majority of production engines regulate the air-to-fuel ratio using a speed-density, or air-flow, control strategy. In this approach, the mass of air drawn into a given cylinder is calculated using the engine speed, manifold absolute pressure, and inlet air temperature. Based on the air mass, appropriate fuel amounts are injected to achieve stoichiometric operation. However, the wide range of operating conditions, inherent induction process nonlinearities, and gradual component degradations due to aging have prompted research into model-based algorithms. In this paper, a nonlinear model-based control strategy will be proposed for simultaneous air-to-fuel ratio control and speed tracking in hybrid electric vehicles. The motivation for engine speed management resides in the integrated control of the engine and a continuously variable transmission for increased efficiency. The proposed backstepping controller uses an observer to reduce the inputs to manifold air mass (e.g., manifold absolute pressure and inlet air temperature) and engine speed. The underlying engine model describes the air intake, fuel injection, and rotational dynamics. For comparison purposes, an existing multisurface sliding mode controller and an integrated speed-density air-to-fuel controller with attached engine speed regulation have been implemented. The performance of each controller is studied using an analytical engine model with representative numerical results presented and discussed to provide insight into the overall performances.     

Constrained real-time control of hydromechanical powertrains – methodology and practical application

Axial piston motors and pumps are core components in many hydromechanical systems as for instance the powertrain of wheel loader vehicles. The optimal performance of the individual components as well as the entire powertrain requires a fast and exact control of both the motor’s swivel angle as well as the pressure difference over the pump by means of the currently available information and despite their respective a-priori unknown reference signal generated by the driver with a joystick or gas pedal operation. Therefore, it is essential that the swivel angle and pressure controllers fully exploit the possible dynamics and the constrained resources of the nonlinear swivel angle displacement and the pressure adjustment system, respectively. In this work, a flatness-based feedforward control strategy for the motor’s swivel angle as well as a flatness-based tracking two-degree-of-freedom controller for the pump pressure are proposed. For the realization of the flat feedforward and the tracking controller, a constrained online trajectory generation by means of a nonlinear (switched) state variable filter is designed for each. Therefore, both controllers are capable of considering the relevant state and input constraints in real-time and without relying on an online optimization. The proposed control algorithms are both discussed and their performance is illustrated with measurement data from a wheel loader vehicle.     

A voltage control strategy for current-regulated PWM inverters

Alternative voltage control strategies for current-regulated PWM inverters are analyzed, including previously established feedforward and feedforward/feedback controllers and a newly proposed decoupling feedback control strategy. The steady-state and dynamic characteristics of each of these control methods are illustrated and compared for a selected inverter design. It is shown that the feedforward controller exhibits steady-state error and an undesirable overshoot of the output voltages during startup. The addition of a feedback loop eliminates the steady-state error and reduces the overshoot; however, the natural response is underdamped regardless of the choice of feedback gains. A decoupling feedback control strategy that eliminates the disadvantages of the feedforward and feedforward/feedback controllers is described. Using the decoupling feedback controller, it is possible to eliminate the steady-state error and place the closed-loop poles wherever desired. Moreover, if the closed-loop poles are selected appropriately, it is possible to eliminate the overshoot of the output voltages during startup transients     

Contouring control of biaxial systems based on polar coordinates

A contouring controller for biaxial systems that integrates the effects of feedback, feedforward, and cross-coupled control is proposed in this study. Conventional approaches to contouring control suffer from the complicated contour-error model and from lack of a systematic way for controller design. The integrated controller is based on polar coordinates under which a relatively simple contour-error model can be obtained. Taking the simple contour error as a state variable, the contouring-control problem is transformed into a stabilization problem. The feedback-linearization technique incorporated with linear feedback or robust control (such as sliding-mode control) can then yield the integrated controller. The proposed method is verified both numerically and experimentally and is compared with the conventional approach. It is found that the proposed controller is better for high speed and/or noncircular contouring. In addition, it can be applied to either linear plants or nonlinear plants (like linear motors).     

Pressure observer-controller design for pneumatic cylinder actuators

Recent research has shown that robust and precise high-speed control of pneumatic actuators is practicable, by application of advanced control techniques such as model-based adaptive and sliding-mode control. However, the resulting need for full state-based feedback and feedforward control-in particular, the measurement of air pressures-increases both the cost and complexity of the overall system. In this paper, we consider the problem of design of observers to estimate the chamber pressure variables in a cylinder actuator. Since the cylinder pressures are not simultaneously observable because of the nature of cylinder dynamics, we first propose a continuous gain observer in which the pressure on one side of the cylinder is measured and the pressure on the other side is estimated. Next, we propose a sliding-mode observer where numerically estimated acceleration is used in order to observe both pressures, with ultimate bounded stability. A sliding-mode controller is proposed, whose sensitivity to errors under the sliding-mode observer is studied. The proposed observers are simple, effective and easy to implement. Results of experimental implementation illustrate the practical effectiveness of the new observers.     

Coordinated Nonlinear Speed Control Approach for SI Engine With Alternator

In the paper, the speed control problem for spark-ignition (SI) engine with alternator is investigated. The problem is addressed from the engine side and the alternator side, respectively, and two coordinated control schemes are proposed for two different operating modes. From the engine side, the torque produced by the alternator is treated as the external disturbance, and a state feedback controller with the magnetic torque feedforward is designed for regulating the engine speed. And from the alternator side, the engine torque ripple is considered as the external disturbance of the alternator rotational dynamics. A disturbance rejection method is proposed to achieve the L ₂-gain performance for the speed servo error. Finally, to demonstrate the validity of the proposed approaches, some simulation results will be shown     

Controller design and implementation for industrial robots withflexible joints

A control strategy which consists of feedforward and feedback compensation loops is proposed to improve the performance of industrial robots. The feedforward loop is similar to the usual inverse-dynamics compensation. The feedback control loop uses a frequency-domain optimal controller. The design starts from the single-link case and is extended to the control of multilinkage flexible-joint robots. An experimental system consisting of a single-link robot is constructed for verifying the proposed control strategies. Experiments show good performance of the proposed control strategy in stiffening the flexible joint and in tracking desired polynomial-type trajectories     

Reference feedforward in the idle speed control of a direct-injection spark-ignition engine

The direct-injection spark-ignition engine has emerged as a focus of research in improving fuel economy and controlling emissions. This engine can operate in multiple modes, including a stratified charge mode with an air-fuel ratio as large as 50:1. Operating in stratified mode results in improved fuel economy and reduced CO/sub 2/ emissions. The stratified charge mode is employed during low speed and load conditions, such as during engine idle. The idle speed control problem is cast as a two-input-two-output control problem and a baseline feedback controller is developed based on an existing topology from the literature. Significant delays, however, inhibit our ability to improve the transient response via feedback alone. An improved scheme employing reference feedforward is proposed and several potential topologies are presented. A reference feedforward algorithm is derived and nonlinear simulation results are shown in which the system transient responses are improved considerably.     

Application of electrically peaking hybrid (ELPH) propulsion systemto a full-size passenger car with simulated design verification

An electrically peaking hybrid electric (ELPH) propulsion system is being developed that has a parallel configuration. A small engine is used to supply power approximately equal to the average load power. The operation of the engine is managed by a vehicle controller and an engine controller such that the engine always operates with nearly full load-the optimal fuel economy operation. An induction motor is used to supply the peaking power required by the electrically peaking load. The motor can also absorb the excess power of the engine while the load power is less than the peak. This power, along with the regenerative braking power, can be used to charge the batteries on board to maintain the battery state-of-charge (SOC) at a reasonable level. With the electrically peaking principle, two control strategies for the drive train have been developed. One is called maximum battery SOC control strategy, by which the engine and electric motor are controlled so that the battery SOC is maintained at its top level as much as possible. This control strategy may be used in urban driving in which accelerating and decelerating driving is common and high-battery SOC is absolutely important for normal driving. The other control strategy is called engine turn-on and turn-off control by which the engine is controlled to operate in a turn-on and turn-off manner. This control strategy may be used in highway driving. Based on the ELPH principle and the drive train control strategies, a drive train for a full-size five-seat passenger car has been designed and verified using the V-ELPH computer simulation package     

Methods for engine supervision and control based on cylinderpressure information

The increasing demands for low emissions and low fuel consumption in modern combustion engines require improved methods for online diagnosis and best possible control of the combustion process. It is demonstrated that the cylinder pressure signal can successfully be used for this task. After introduction of some theoretical background, several application examples are presented: an online supervision of fuel injection, some results on feedforward emission control, and a concept for feedback control of spark timing. Experimental results obtained from stock car diesel and spark ignition engines are included to support the automation concepts     

Precise position control of shape memory alloy actuator using inverse hysteresis model and model reference adaptive control system

Position control of Shape Memory Alloy (SMA) actuators has been a challenging topic during the last years due to their nonlinearities in the governing physical equations as well as their hysteresis behaviors. Using the inverse of phenomenological hysteresis model in order to compensate the input–output hysteresis behavior of these actuators shows the effectiveness of this approach. In this paper, in order to control the tip deflection of a large deformation flexible beam actuated by an SMA actuator wire, a feedforward–feedback controller is proposed. The feedforward part of the proposed control system, maps the beam deflection into SMA temperature, is based on the inverse of the generalized Prandtl–Ishlinskii model. An adaptive model reference temperature control system is cascaded to the inverse hysteresis model in order to estimate the SMA electrical current for tracking the reference signal. In addition, a closed-loop proportional–integral controller with position feedback is added to the feedforward controller to increase the accuracy as well as eliminate the steady state error in position control process. Experimental results indicate that the proposed controller has great accuracy in tracking some square wave signals. It is also experimentally shown that the suggested controller has precise tracking performance in presence of environmental disturbances.     

A novel AQM algorithm based on feedforward model predictive control

Developing feedforward model predictive controller as an active queue management (AQM) scheme is studied in this paper. MPC is an advanced control strategy for AQM. However, the conventional MPC is usually an implementable form of feedback MPC. In this paper, a feedforward and feedback optimal control law is presented. It is a clean, easily implementable, version of model predictive control that incorporates feedforward. Firstly, we use the nominal fluid model to design the feedforward control input so that the output tracks the given queue length with small error. Furthermore, in order to achieve robust performance and to reject the (unmeasured) disturbance, the feedback component is designed. In particular, a disturbance observer is incorporated into the prediction output in standard feedback MPC. This framework can significantly improve performance in the presence of measurement noise and certain types of model uncertainty. Finally, the simulation results show the effectiveness of FF‐AQM algorithm.     

Perfect tracking control based on multirate feedforward controlwith generalized sampling periods

In this paper, a novel perfect tracking control method based on multirate feedforward control is proposed. The advantages of the proposed method are that: (1) the proposed multirate feedforward controller eliminates the notorious unstable zero problem in designing the discrete-time inverse system; (2) the states of the plant match the desired trajectories at every sampling point of reference input; and (3) the proposed controller is completely independent of the feedback characteristics. Thus, highly robust performance is assured by the robust feedback controller. Moreover, by generalizing the relationship between the sampling period of plant output and the control period of plant input, the proposed method can be applied to various systems with hardware restrictions of these periods, which leads to higher performance. Next, it is shown that the structure of the proposed perfect tracking controller is very simple and clear. Illustrative examples of position control using a DC servomotor are presented, and simulations and experiments demonstrate the advantages of this approach     

Gas supply control and experimental validation for polymer electrolyte membrane fuel cells

Gas supply system control, which consists of air and hydrogen supply control, are two basic and crucial topics for proton exchange membrane fuel cell (PEMFC) control. To protect the PEM and improve the performance of the PEMFCs, the air pressure and flow of the cathode, and the hydrogen pressure of the anode should be precisely controlled. In this paper, we primarily research the modelling of the cathode and anode and the nonlinear controller design for pressure control, as well as air flow control. In detail, control-oriented models are established for cathode and anode controller design. Owing to the existence of model uncertainty and disturbances, such as humidity, temperature, and water vapour, an extended state observer (ESO) is designed to estimate and compensate for these influences. Cathode and anode pressure controls are synthesized in the uniform control scheme. For air flow control, a feedforward channel based on the air flow model of the compressor and a feedback channel based on the proportional–integral (PI) controller are proposed to regulate air flow. The proposed control methods are validated by experiments under different operating conditions of PEMFCs.     

Robust controller design for PTP motion of vertical XY positioning systems with a flexible beam

This paper presents a point-to-point (PTP) motion control method for accurate positioning and vibration suppression of a vertical XY positioning system with a flexible beam. The proposed method is composed of a feedforward and feedback controller. The input preshaping based on the analytic modeling and frequency equation of the system is proposed as a feedforward controller to produce the desired responses. The feedback controller based on a robust internal-loop compensator is designed to meet the specified performance and to stabilize the whole system in the presence of uncertainties and disturbances. By integrating the input preshaping controller and feedback controller, it is shown that the system is stable and the vibration of the flexible beam is suppressed. The proposed algorithm is demonstrated experimentally on an XY positioning system which consists of a base cart, elastic beam and moving mass.     

On-line cylinder fault diagnostics for internal combustion engines

The ability to continuously monitor internal combustion engines for the existence and location of faults can improve engine reliability and reduce operating costs. The diagnostics method is based on recording the engine speed fluctuations at the flywheel and at the front end of the engine over one combustion cycle. From the speed fluctuations, the cylinder-to-cylinder variations of the net engine torque are computed. The performance deterioration of an individual cylinder is detected as a drop of computed torque. The diagnostic hardware consists of a digital engine speed data acquisition system and an embedded controller and is suited for in-vehicle installation. The method, suited for any multicylinder engine, detects the location and severity of faults during normal engine operation. Adjustments for individual engines of the same class are not required     

Adaptive gain scheduling with feedforward control system based on system model for PMSM

A feedforward controller for permanent magnet synchronous motor (PMSM) has been proposed in this study, and proportional and integral gain could be self-adaptive under different operating conditions. The control structure used in the feedforward system is the same as in the feedback control system. This control structure could guarantee independence of the speed command input to output with the disturbance input to output, which makes the system have better reference trajectory tracking and disturbances rejection. In order to obtain optimal control performance when the parameters are uncertain, a gain scheduling adaptive controller is used in the feedforward system. The proposed controller has been verified by the experimental and simulation results with less steady-state error and better dynamic response than the controllers without it under the condition of external load torque disturbance and PMSM parameter uncertainties.     

Neural network control of functional neuromuscular stimulationsystems: computer simulation studies

A neural network control system has been designed for the control of cyclic movements in functional neuromuscular stimulation (FNS) systems. The design directly addresses three major problems in FNS control systems: customization of control system parameters for a particular individual, adaptation during operation to account for changes in the musculoskeletal system, and attaining resistance to mechanical disturbances. The control system was implemented by a two-stage neural network that utilizes a combination of adaptive feedforward and feedback control techniques. A new learning algorithm was developed to provide rapid customization and adaptation. The control system was evaluated in a series of studies on a computer simulated musculoskeletal model. The model of electrically stimulated muscle used in the study included nonlinear recruitment, linear dynamics, and multiplicative nonlinear torque-angle and torque-velocity scaling factors. The skeletal model consisted of a one-segment planar system with passive constraints on joint movement. Results of the evaluation have demonstrated that the control system can provide automated customization of the feedforward controller parameters for a given musculoskeletal system. It can account for changes in the musculoskeletal system by adapting the feedforward controller parameters on-line and it can resist the effects of mechanical disturbances. These results suggest that this design may be suitable for the control of FNS systems and other dynamic systems     

基于labview的压力反馈和控制系统研究

在labview软件环境下,本文设计了一种压力反馈和控制系统.而该系统能够利用模糊PID控制器实现气缸压力跟踪和反馈,并通过控制气动阀实现气缸压力精确调节,因此能够满足压力反馈和控制要求.     

Random vibration test control of inverter-fed electrodynamic shaker

The random vibration control of an inverter-fed electrodynamic shaker is presented in this paper. First, the dynamic model of the shaker is found and a current-controlled pulsewidth modulation inverter is designed and implemented. The feedback controller is augmented with a command feedforward controller and a disturbance feedforward controller to let the armature exciting current have low harmonic content and possess excellent waveform tracking performance. Then, an acceleration controller and its random vibration command are arranged. In the proposed acceleration control scheme, a command feedforward controller and a robust disturbance feedforward controller are also employed to let the shaker have close random acceleration command waveform tracking control performance, and the performance be insensitive to the system parameter variations. It follows that the acceleration control with desired frequency response in a vibration test could be achieved through properly setting the command signal. The effectiveness of the proposed control scheme is verified by simulation and measured results