Electric Power Steering Research Articles

Torque Ripple and Radial Force Minimization of Fractional-Slot Permanent Magnet Machines Through Stator Harmonic Elimination

This article proposes a torque ripple minimization strategy based on minimizing interactive space harmonics of fractional-slot permanent magnet (PM) machines using a space-shifted wye–delta stator winding. A radial force analysis has also been carried out, which showed a substantial reduction in the second-order mode for these space-shifted wye–delta wound machines; this will improve the noise and vibration performance. The effectiveness of the proposed method is shown by analyzing the performances of a low-power surface-mounted permanent magnet (SPM) machine for the electric power steering (EPS) applications and a high-power interior permanent magnet (IPM) machines for the hybrid electric vehicle (HEV) applications on the 12-slot/10-pole (12 S/10 P) configuration. The proposed winding doubles the stator slot number of the base model, and as a result, the base 12 S/10 P configuration becomes 24-slot/10-pole (24 S/10 P) combination. Compared with the existing ripple minimization techniques of magnet shaping or rotor skewing, the proposed stator winding-based strategy achieves better torque ripple performance and magnet utilization leading to an improvement in average torque while reducing the amplitude of the low-order radial force. A 10-pole SPM machine has been built and tested for experimental validation of both the concept and the finite element analysis (FEA) simulation results.

극 슬롯 조합에 따른 영구자석 표면 부착형 동기전동기의 특성 분석 연구

In this paper, the characteristics of SPMSM (Surface mounted Permanent Magnet Synchronous Motor) applied to EPS(Electric Power Steering) systems were analyzed according to the combination of pole slots. In general, fractional-slot permanent magnet synchronous motors using concentrated windings have advantages such as being more economical than distributed windings, having shorter end windings, and high copper fill factor. However, traditional permanent magnet synchronous motor having the fractional slot has a relatively low winding factor due to the slot pitch and pole pitch ratio. One way to compensate for this is to use a modular motor with fewer slots for a given number of poles. The modular motor is a motor with the number of slots per pole per phase less than 0.5, and the winding factor is larger than that of the traditional motor. Therefore, in this paper, three types of motors: fractional slot modular motors, traditional motors, and integer slot motors, were analyzed and the power characteristics were compared using the FEM(Finite Element method).

Displacement characteristics hierarchical control of electro-hydraulic compound steering for commercial vehicle

The electro-hydraulic compound steering combines the function of electric power steering and hydraulic power steering, which can reduce the energy consumption of steering, ensure the stability of vehicles, and meet the steering demand under unmanned driving. In order to fully coordinate the steering stability and path tracking requirements in the unmanned steering process, this paper proposes a hierarchical control strategy of displacement characteristics for commercial vehicle electro-hydraulic compound steering. The mixed H2/H∞ controller for the vehicle stability is designed in the upper layer, which takes the vehicle yaw rate as the control variable. Based on the motor model and sliding-mode control theory, the sliding-mode variable structure controller of motor angle is designed in the lower layer, and the hydraulic power distribution is completed by estimating the steering resistance torque. Simulation results show that the designed controller can effectively track the yaw rate on the premise of ensuring path tracking effect. Combined with steering torque estimation and hydraulic power distribution rules, it can effectively realize the coordinated control of hydraulic power and motor rotation angle.

Diagnosis and analysis of electric power steering rattle noise based on multiple coherence method

Electric power steering (EPS) system is becoming the primary source of Electric Vehicle (EV) noise due to absence of classic power train. The rattle noise produced by EPS, which is easily discernible when driving. Since the conventional subjective evaluation approach makes it difficult to identify the source, it is required to establish an objective way to solve such an issue. In this paper, the principle of multiple coherence method is first addressed analytically, and then is employed to analyze the vibration signal acquisition from EPS different points, meanwhile, combine with in-car sound signal, to accurately identify the specific location.

Integrated optimization design of electric power steering and suspension systems based on hierarchical coordination optimization method

Integrated optimization design of electric power steering and suspension systems based on hierarchical coordination optimization method

Stability modelling and control algorithm of electric vehicle power steering

Stability modelling and control algorithm of electric vehicle power steering

Stability modelling and control algorithm of electric vehicle power steering

Stability modelling and control algorithm of electric vehicle power steering

Research on EPS system control strategy of SUV based on CarSim/Simulink

In order to solve the problems existing in traditional electric power steering system control methods, such as poor operation angle control effect, low system control accuracy and long control time, this study designed an electric power steering system control strategy of sports utility vehicle based on CarSim/Simulink. Firstly, the characteristics of electric power steering system are analysed, which provides the basis for subsequent control; then, the dynamic model of sports utility vehicle is constructed. On this basis, vehicle model is abstracted and simplified based on CarSim/Simulink software. Finally, according to the power assist characteristic curve model, the parameters such as steering wheel torque signal and vehicle speed sensor are optimised to complete the research on the control strategy of electric power steering system of sports utility vehicle. Experimental results show that the proposed method has a good effect on the operating angle control of SUV EPS system, the control accuracy of the system is always higher than 90% and the maximum time consumption is only 7 s.

Experimental Validation of Torque-Based Control for Realistic Handwheel Haptics in Driving Simulators

A realistic steering feel is one of the key elements to guarantee fidelity on a driving simulator in general, and in particular to replicate on-centre vehicle handling. This requires precise modelling of the steering dynamics, a high bandwidth control loading system, and coupling of virtual and physical components in agreement with computational requirements and hardware limitations. For such a coupling, the common approach position-based control uses the measured signals of steering wheel angle and steering rate as inputs to the steering system model. This paper proposes an alternative torque-based control scheme using steering torque as an input to the steering system with additional compensation. Torque-based control was designed and evaluated in conjunction with detailed electric power steering models including state-of-the-art friction models, a neuromuscular driver model, and two driver-in-the-loop experiments in a high-end driving simulator. The objective analysis performed by means of the neuromuscular driver model reveals that the driver applies less impedance i.e. the driver is less stiff on a driving simulator when steering feedback is provided with the torque-based control compared to the position-based control. The investigations demonstrate that torque-based control reduces haptic response delay and vibrations caused by friction modelling compared to position-based control. The driver-in-the-loop experiments show significant objective effects on steering performance and subjective evaluation of fidelity and effort. We conclude that the proposed approach closes the vehicle-driver loop with more realism in a driving simulator.

SIMULATION OF TROLLEBUS STEERING SYSTEM WITH ELECTRIC POWER STEERING BASED ON ROLLING ROTOR SWITCHED RELUCTANCE MOTOR

The analysis of power steering which used on modern rolling stock is carried out. Their main shortcomings are identified. Given the requirements for the steering of trolleybuses, a solution to increase its efficiency is proposed. Based on the developed mathematical model and functional diagrams of the trolleybus steering system with a electric power steering based on rolling rotor switched reluctance motor, a simulation model of trolleybus steering was created using the Matlab Simulink package. The peculiarity of the simulation model is taking into account the mass and size characteristics of the rolling stock, the parameters of the suspension of the steered axle, the impact of the road surface and the speed of the trolleybus, changes in the parameters of the electric motor magnetic system during operation. The rolling rotor switched reluctance motor which is offered for use as the electric power steering of the LAZ E183D1 trolleybus is calculated. The calculation of the magnetic system of the engine by the finite element method with the subsequent approximation of the obtained results is carried out. With the help of the developed simulation model the simulation of the trolleybus steering system with electric power steering based on rolling rotor switched reluctance motor was performed. Time diagrams of transients in the trolleybus steering system are obtained and their processing and analysis are carried out.

Design and implementation of human driving data-based lane-keeping assistance system for electric bus

This paper describes design, implementation, and evaluation of human driving data-based Lane Keeping Assistance System (LKAS) for electric bus equipped with a hybrid electric power steering system. The hybrid electric-power steering system used in this study means a steering system in which an Electric Power Steering (EPS) system and an Electro-Hydraulic Power Steering (EHPS) system are integrated into a ball-nut. A dynamic model of hybrid EPS system including EHPS system and EPS system has been developed to generate EPS torque and EHPS force corresponding to the input torque. In order to determine proper timing of LKAS intervention, driving data of electric bus drivers were collected and driving patterns were analyzed using a 2-D normal distribution probability density function. Lane information necessary for the lane-keeping assistance system is obtained from a vision camera mounted on the electric bus. Sliding mode control is used to get a Steering Wheel Angle (SWA) required for LKAS. A Proportional–Integral (PI) control is used to obtain an overlay torque required to track the target SWA. A proposed DLC threshold has been validated using vehicle simulation software, TruckSim, and MATLAB/Simulink. It is shown that the proposed DLC threshold shows good performance in both cases of slow lane departure and fast lane departure. The proposed algorithm has been successfully implemented on the electric bus and evaluated via real-world driving tests. Test scenario setting and the evaluation of performance were carried out by ISO 11270 criteria. It is shown that the algorithm successfully prevented the electric bus from unintended lane departure satisfying ISO 11270 criteria.

Electric power steering systems: Electronic control strategies for enhanced performance and efficiency

This research paper explores advancements in electric power steering (EPS) systems, focusing on electronic control strategies that enhance vehicle performance and energy efficiency. EPS has become a crucial technology in modern vehicles, offering significant benefits over traditional hydraulic systems, including reduced energy consumption and greater integration potential with advanced driver assistance systems (ADAS). This study examines the evolution of steering systems, highlighting the transition from manual to hydraulic and eventually to EPS, as well as the key components and architecture of modern EPS systems.The paper further delves into innovative control algorithms, such as model-based, adaptive, and robust control strategies, which contribute to precise steering control and improved driving experience. In addition, it discusses performance enhancement techniques, including variable steering ratio and disturbance rejection, alongside energy-efficient motor control techniques and power-on-demand strategies that optimize system efficiency.Finally, this paper addresses the integration of EPS with ADAS and autonomous driving technologies, reliability and fault-tolerance measures, and the challenges and future trends shaping the next generation of steering systems. Through an analysis of current research and industry developments, this study provides a comprehensive overview of EPS technology and its future prospects.

Electric Power Steering Power Circuit Health Assessment and Mitigation Strategy

With recent developments of energy efficient design and control for electric motors, electrical subsystems and components have become integral parts of main actuators in vehicle systems (e.g., steering and propulsion systems). To ensure proper vehicle operations, it is important to make sure that electrical power is properly transmitted through the power circuit from vehicle power source to the electric motor. However, degradation in the power circuit health, which often manifests itself as increased resistance, may affect power transmission and degrade the system performance. For example, in Electric Power Steering (EPS) systems, if the EPS power circuit resistance is increased and the EPS is drawing power to assist the driver, voltage at the EPS module will drop significantly, causing the EPS to reset and, consequently, Loss of Assist (LOA) incidents. Due to compliance in the steering system and suspension design, drivers often feel that the steering system is fighting back when an LOA incident occurs. While previous work has partially addressed this issue by developing algorithms that estimate resistance increase in EPS power circuits, this paper further validates and refines the algorithms for vehicle on-board and off-board implementations using test drive data collected. Since on-board and off-board implementations impose different limits on signal sampling rates, a total of 250 and 465 minutes of data are respectively collected with various vehicle speeds and steering maneuvers. Moreover, a supervisory control solution, referred to as EPS Anti-Loss-of-Assist (ALOA), is proposed that gradually and proactively reduces EPS torque assist as resistance in the EPS power circuit increases so that the EPS voltage is kept above a resetting threshold. Stationary steering tests of the proposed solution as well as demonstrations on parking lot maneuvers at General Motors Milford Proving Grounds are conducted. The stationary steering tests and demonstrations show that, with the proposed supervisory control, negative effects of increased EPS power circuit resistance can be mitigated without noticeable changes in normal driving experience.

Towards a security‐driven automotive development lifecycle

AbstractCybersecurity has become one of the most crucial challenges in the automotive development lifecycle. The upcoming ISO/SAE 21434 standard provides only a generic framework that is insufficient to derive concrete design methods. This article proposes an actionable cybersecurity development lifecycle model that provides concrete action and work product guidance aligned with the ISO/SAE 21434 and Automotive SPICE® extension for cybersecurity. The model has been inspired by action research in “next” industry practice pilot projects, which ensures that it is actionable. It has been augmented by insights gained from literature research in cybersecurity development for embedded systems. The proposed lifecycle model complements the ISO/SAE 21434 standard and provides the basis for the company‐specific process and practice specifications. It has been validated through the integration of cybersecurity‐related aspects in an electric power steering system. A core characteristic of the model is the central role of threat modeling, vulnerability analyses, and cybersecurity requirements derivation on both system and subsystem levels. Without concrete practice guidelines, the ISO/SAE 21434 is very difficult to understand and apply at this stage. This contribution aims to fill this gap through a model inspired by cutting‐edge embedded cybersecurity practices interpreted for the current and near‐future automotive electronic architectures.

Model-based feedforward control for suppressing torque oscillation of electric power steering system

Oscillation suppression is essential for the stability design of electric power steering (EPS) systems. The stability controller module in EPS controller is the key to solve the stability control problem of EPS system. This paper proposes a new method of stability analysis and stability controller module design for EPS systems. Furthermore, the dynamic characteristics of the EPS system are analyzed, and two critical factors on the resulting EPS stability, that is, large assist and variable assist gain are investigated experimentally. The transfer function from steering torque to sensor torque is redefined. A new transfer function is proposed for measuring the effect of variable assist gain on system performance. Based on the above factors and transfer functions, constraints on the stability controller design are proposed. Then the optimal parameters in the controller are obtained by maximizing an objective function including phase margin, gain margin, and crossover frequency. It is concluded from simulations and bench tests that the proposed stability controller can significantly reduce the torque oscillation of the EPS system.

Hardware-in-the-Loop Simulation of Self-Driving Electric Vehicles by Dynamic Path Planning and Model Predictive Control

This paper applies a dynamic path planning and model predictive control (MPC) to simulate self-driving and parking for an electric van on a hardware-in-the-loop (HiL) platform. The hardware platform is a simulator which consists of an electric power steering system, accelerator and brake pedals, and an Nvidia drive PX2 with a robot operating system (ROS). The vehicle dynamics model, sensors, controller, and test field map are virtually built with the PreScan simulation platform. Both manual and autonomous driving modes can be simulated, and a graphic user interface allows a test driver to select a target parking space on a display screen. Three scenarios are demonstrated: forward parking, reverse parking, and obstacle avoidance. When the vehicle perceives an obstacle, the map is updated and the route is adaptively planned. The effectiveness of the proposed MPC is verified in experiments and proved to be superior to a traditional proportional–integral–derivative controller with regards to safety, energy-saving, comfort, and agility.

Control of a Permanent Magnet Synchronous Motor in Simulink

Abstract Nowadays, before the era of modern Steer-by-wire steering systems, the most widely used steering technology is Electric Power Steering (EPS). This paper contains the developing of a Permanent Magnet Synchronous Motor (PMSM) control circuit for EPS systems, in Matlab Simulink environment. The mathematical model of the Permanent Magnet Synchronous Motor was created via the four equations that represent the relation between the fluxes, voltages and currents in d-q reference frame and the motor torque equation. Mathematical transformations are required to generate the equivalent input values of the model from analog input waves. In this way, the embedded software is able to communicate with the motor through the analog input and output signals. The control model was also tested in a physically implemented system. The control software is executed on a dSpace AutoBox hardware. The output interface block creates the output phase voltages specified by the control module, and the input interface block allows the phase currents generated by the output voltage to be measured back.

EPS System of Tractor Automatic Driving: An Improved LMI with Mixed Sensitivity Control Method

Electric power steering (EPS) is widely used in tractor automatic driving because of its good operation stability. However, there is a lack of research about solving robust problems and response ability simultaneously when the tractor encounters emergency steering in harsh fields. The traditional robust controller has poor tracking performance and antidisturbance ability when encountering emergency steering. This paper proposes to add the corresponding mixed sensitivity operator to the corresponding performance index in the controller. By adjusting the amplitude of the mixed sensitivity operator, the tracking performance and the speed of disturbance attenuation can be both adjusted for the tractor EPS system. Simulation and hardware in the loop experiments verify the antidisturbance ability of the controller and the torque tracking performance. The results show that the control method has strong robustness and robust stability, which can meet the practical requirements. Also, the power steering characteristic of the H∞ controller with hybrid sensitivity design method is better than that of an unoptimized one, and its robustness is better, and under external pavement interference, the following ability is stronger for the ideal hand torque and the steering is more stable.

Actuator-Integrated Fault Estimation and Fault Tolerant Control for Electric Power Steering System of Forklift

For the problem of actuator-integrated fault estimation (FE) and fault tolerant control (FTC) for the electric power steering (EPS) system of a forklift, firstly, a dynamic model of a forklift EPS system with actuator faults was established; then, an integrated FE and FTC design was proposed. The nonlinear unknown input observer (NUIO) was proposed to estimate the system states and actuator faults, and an adaptive sliding mode FTC system was constructed based on it. The gain of the observer and controller is obtained by H∞ optimization and one-step linear matrix inequality (LMI) formula operation in order to realize the overall optimal design of an FTC system. Finally, the experimental results show that when actuator failure occurs, the proposed integrated FE and FTC were more accurate than the decentralized design to estimate the system states and the actuator faults. The proposed fault-tolerant controller can more effectively restore the power assist performance of the steering power motor in case of failure and effectively ensure the safety and reliability of the forklift EPS system.

Steering feel improvement by mathematical modeling of the Electric Power Steering system

Currently, the Electric Power Steering (EPS) system is an essential component of the vehicle because it provides assistive steering torque to the driver. To ensure a faster steering response, the position of the EPS in some vehicles is moved closer to the tire rather than the steering wheel. The steering torque, which is provided by the EPS in the steering system, mainly affects the driver’s feel while steering. Therefore, the driver often feels uncomfortable owing to such positioning of the EPS in the steering system. In particular, the nonlinearity of the Universal Joint (UJ), which is one of parts of the steering system, can be felt at the steering wheel side.In this paper, we proposed an algorithm based on the mathematical model of the steering torque in the steering system to improve the steering feel. The mathematical model is structured using parameters that can be obtained from the information of the steering system. Moreover, the formulation of the steering torque consists of the two parts, namely the deformation part, which describes the propagation inside the steering system, and the friction part that describes the inherent friction in the UJ.Simulation and experiments were conducted to verify the proposed mathematical model with similar conditions to the real tire load during the steering motion. Furthermore, to improve the driver’s feel during steering, a torque compensation algorithm is proposed and verified through experiments.