Browse Topic: Power steering
Precision control in Level 4 Automated Vehicles is essential for enhancing operational efficiency, accuracy, and safety. This work, conducted as part of ARPA-E’s NEXTCAR program, focuses on developing a robust hardware and software control solution to enable drive-by-wire functionality. A previous publication by the authors presented the hardware solutions for overtaking stock vehicle controls. This paper focuses on a model-based and data-driven control algorithm to enable drive-by-wire functionality for longitudinal and lateral motion control for a 2021 Honda Clarity Plug-In Hybrid Electric Vehicle. This vehicle was equipped with a set of sensors and an onboard processing unit to enable Level 4 automation. For lateral controls, an algorithm was developed to command steering torque to the electronic power steering module, ensuring the vehicle could attain the desired steering angle position at varying speeds. The system leveraged feedforward and feedback mechanisms. Feedback controller gains were identified through frequency response analysis of the steering torque assist electric motor and were further refined during track testing. To optimize the controller’s response time, a feedforward function was developed using a physics-aware model of the vehicle's steering system. The independent feature selection for the model was guided by using the physics of the system. For longitudinal control, the control inputs included the positions of the brake and accelerator pedals sent to the stock ECU, with the desired speed as the setpoint. The setup used a combination of feedforward and feedback control to achieve the target acceleration or deceleration. These algorithms underwent extensive dynamometer and track testing to perform various maneuvers in conjunction with the automated driving system.
The high-pressure steering hose in a hydraulic steering system carries pressurized hydraulic fluid from the power steering pump to the steering gear (or steering rack). Its main function is to transmit the force generated by the pump so that the hydraulic pressure assists the driver in turning the wheels more easily. The high-pressure hydraulic pipeline in the power steering system is a vital component for ensuring optimal performance. During warranty analysis, leakage incidents were observed at the customer end within the warranty period. The primary factors contributing to these failures include pipe material thickness, material composition, mechanical properties, and engine-induced vibrations. This study investigates fatigue-related failures through detailed material characterization and Computer-Aided Engineering (CAE) based on real world usage road load data collected. The objective is to identify the root causes by examining the influence of varying pipe thickness on fatigue life. The investigation discovered that crack initiation predominantly occurred on the concave side of bent pipe sections, specifically on the engine-side high-pressure steering line, which is connected to the power steering pump mounted on the engine. Fracture surfaces exhibited characteristics consistent with fatigue failure, with crack propagation primarily oriented longitudinally along the pipe. The highest tangential stresses were observed on the out word, resulting from the combined effects of internal hydraulic pressure and vibrational loads. Fatigue cracks originated from the inner surface and propagated outward under cyclic stresses induced by pressure fluctuations and engine vibrations during vehicle operation on the road. Computer-Aided Engineering (CAE) simulations indicated that the failure mechanism was primarily attributable to an incorrect material thickness selection during the development phase. Modifications to the pipe design, including increased material thickness, were implemented, leading to improved performance in subsequent testing. The high-pressure hydraulic pipeline exhibits decreased failure rates and improved reliability and durability following the implementation of the revised design.
The aim of this study is to develop a validated simulation method that accurately predicts vehicle behavior during a sudden loss of assist while cornering. The method also evaluates the steering effort required to return the vehicle to its intended path during failure scenarios, isolating the impact of uncertainties arising from driver performance. To illustrate the simulation methodology, the study involved testing various vehicles under conditions replicating sudden EPS assist loss during cornering. These tests captured the vehicle’s response, and the steering effort needed to correct its path. Different parameters affecting the vehicle behavior were studied and a validated method of simulation was developed.
To reduce the harm caused by the failure of electronic and electrical system, the application of ISO 26262 functional safety standard in the automotive industry is more and more widespread. As a critical safety-related electronic and electrical system in automobile, electric power steering is very important and necessary to meet the requirements of functional safety. This paper introduces the main development activities of functional safety at software level. In order to realize the purpose of freedom from interference in memory, the safety mechanism of memory protection is proposed in software safety analysis. The memory protection is realized in AUTOSAR architecture by configuration.
The flight area of drones and other unmanned aerial vehicles (UAVs) had been highly restricted but has been relaxing, including flights beyond the scope of sight. Deregulation without aircraft-reliability improvement increases the risk of accidents. However, demanding high reliability for all aircraft leads to an increase in the price of the aircraft. Therefore, if airspace restrictions are relaxed for more reliable aircraft, the cost of higher reliability and its benefits can be balanced. This will improve efficiency and optimize cost-effectiveness. The purpose of this proposal is to balance the cost of aircraft-reliability improvement (which allows flight to continue in the event of a failure) and its advantages. Specifically, the author proposes rules that apply more relaxed airspace restrictions to UAVs with higher FCLs (Flight Continuity Possibility Levels) and stricter airspace restrictions to those with lower FCLs. The FCL does not only refer to the distance or time that can be flown but also includes the ability to reduce the descent rate or lessen the impact on landing using the remaining flight resources at the time of failure. Technological development has also been underway to ensure that automobile powertrain systems and electric power-steering systems continue to operate in the event of failure, and by using these technologies, it is possible to increase the FCL at lower cost.
If you accept that the oddball and odd-sized Journey never was a legit rival for the likes of the Honda CR-V, Toyota RAV4 and Ford Escape - and it wasn't - Stellantis' Dodge brand hasn't played in the compact SUV segment, one of the largest and most competitive in the U.S. That strategic gap is set to be filled by the 2023 Hornet, Dodge's performance-slanted attempt to peel out some sales volume from among the C-segment utilities that are typified by mundane and softly-tuned top-sellers. The Hornet's not just about having a little more engine power, either. Its platform is shared with the Alfa Romeo Tonale. Like Hornet, the Tonale slated to be in showrooms sometime in spring 2023 and incorporates chassis finery such as standard Koni-supplied Frequency Selective Damping (FSD) dampers. Specifically tuned, genuine by-wire braking (for the R/T trim) reduces curb weight by 9 lb. (4 kg) and improves steering feel via direct-action ratios from the electronic power steering; Stellantis claimed the Hornet GT's ratio, at 13.6:1 (shared with the Tonale) is the most direct in the segment.
The present article related to the investigation of fluid bore noise in the power steering pump which is the major source of noise generation in hydraulic power steering system due to the flow ripple and pressure pulsation. In this article, the different parameters (Pump operating speed, operating pressure, bypass hole dimensions and bypass hole orientation) has been investigated and its contribution to the fluid borne noise has been analyzed through Computational Fluid Dynamics (CFD) methods. The design optimization has been done on the power steering pump on the basis of CFD results and the physical sample was made for the same to validate the CFD results. The results show that the pump operating speed is more significant in the fluid borne noise generation followed by the operating pressure, bypass hole angle and diameter. The fluid borne noise increases as the operating speed and operating pressure increases. Conversely the fluid borne noise decreases as the bypass hole angle and diameter increases. Since the operating speed and pressures are functional requirement, optimization has been done on bypass hole angle and diameter through CFD. The experimental results show that the fluid borne noise in the power steering pump was reduced about 5% ~16% through angular bypass hole optimization.
The steering system is to provide the driver with the possibility of lateral vehicle guidance, i.e. to influence the lateral dynamics of the vehicle; moreover, it is crucial to promptly translate the steering input to have the vehicle in high-quality directional stability. An electrical power assisted steering (EPAS) system is the sophisticated variant to meet higher requirements for vehicle safety, ride comfort, and driver-assist. This research is to investigate if a CAE methodology could be innovated to better simulate the durability of a steering system under various working scenarios; figure out the critical features of the modeling; conduct a correct analysis procedure for validating the modeling and collecting data for evaluation. With step by step in modeling and analysis, a well-established example of CAE model of EPAS is enabled to highlight the novelty of steering vehicle level CAE methodology and therefore achieve the research goal.
This paper is an application of ISO 26262 functional safety standards for fail-safe design, development and validation of Electric Power Assisted Steering (EPAS) System. As part of safety feature to save lives, prevent injuries and reduce economic loss due to accidents, many research institutes are working to ensure the safety and reliability of emerging safety-critical Electronic Control Systems in automobile applications. As, Advanced Driver Assistance Systems (ADAS) and other emerging technologies are introduced in the automobile application, the overall safety of these advanced electronic systems relies on the vehicle safety systems, such as steering systems. This paper outlines the approach of performing the Hazard Analysis & Risk Assessment (HARA) and developing a Functional Safety Concept. This approach incorporates several analysis methods, including Hazard and Operability study, Functional Failure Modes and Effects Analysis. This approach is then applied to the Electric Power Assisted Steering (EPAS) system to identify vehicle-level hazards, and derive safety goals and functional safety requirements. This paper presents the vehicle-level hazards, and safety goals derived from the analysis and includes a discussion of “fail-safe” and “fail-operational” needs, which results in the derivation of functional safety requirements. The results of this study may serve as an example of how different analytical methods could be applied to develop a functional safety concept.
Steering system is responsible for providing a precise directional control to the vehicle. The Hydraulic Power Assisted Steering (HPAS) system is commonly used in passenger cars and commercial vehicles due to low cost. Power steering pump develops and delivers required pressure to provide assistance while steering. It reduces the effort required to steer the vehicle. Steering pump (generally vane type) is a critical part providing hydraulic pressure assistance to rack and pinion or gear box. Basically the hydraulic pump noise can be classified as ‘Moan Noise’ and ‘Whine Noise’. The noise generated by power steering pump pressure pulsation is termed as ‘Moan’ and ‘Whine’ based on operational induce frequency. As power train becomes quieter, it becomes more perceivable at typical engine operating speed range and gives impression of poor refinement and quality. This abstract describes the experimental measurement technique to investigate, analyze and quantify the moan noise and elaborate on design of experiments along with its effect on steering system’s moan noise and performance. It also covers the comparative benchmark analysis of different power steering pump designs and its contribution in the moan noise. This research work has helped us to come out with new test method to assess different steering system noises at component, system and vehicle level. Measurements revealed a strong correlation between pump pressure pulsation and steering system moan noise. The subject research work has resulted in elimination of moan noise to achieve better NVH performance in passenger car by optimizing the steering pump and steering line design.
In the current customer centric automotive market, NVH is one of the prime focus for the automotive industry. Almost all light commercial vehicles in the market are with hydraulic power steering system. Hydraulic power steering pump is heart of the steering system which circulates the hydraulic oil to steering gear for assisting the driver. One of the NVH problem which is inevitable with the hydraulic vane pump is humming noise and this is perceived as an irritant by end user. This paper describes a novel technique for reducing the humming noise which is perceived at driver ear level. Base vehicle level objective measurements is carried out to set the acceptance criteria. Existing design is optimized as per CAE iterations and vehicle updated with the multiple solutions and objective measurements are recorded. Driver ear level noise reduction upto 4 dB(A) perceived which meets acceptance criteria. This technique can be used for resolving all hydraulic power steering pump related noise issues.
Hardware-in-the-loop (HIL) test benches are indispensable for the development of modern vehicle dynamics controllers (VDCs). They can be regarded as a standard methodology today, because of the extremely safety critical nature of the multi-sensor and multi-actuator systems used in vehicle dynamics control. The required high quality standards can only be ensured by systematic testing within a virtual HIL environment before going into a real car. The steering system is an important aspect of the automobile from operational safety and driver enjoyment perspectives. Current Problem/Opportunity is realistic subjective steering feel prediction before vehicle build. And upfront predict the handling characteristics more accurately with subjective feel before proto build. Current Issue is difficult to convert the objective data into subjective feel and difficult to incorporate the nonlinear steering characteristics with hysterics, friction and power assist curves using virtual simulation. Solution is HIL system with hardware steering should give realistic torque feedback while steering input is given manually to the hardware steering system. It will enable to achieve the desired vehicle dynamic characteristics before proto build. The objective of this study is HIL Simulator of steering has to provide realistic torque feedback with manual steering input to the hardware steering system. The steering input (steering wheel angle) provided by actuator for open/closed loop manoeuvre will predict the realistic vehicle handling behavior in the CAE model. The system has to have capability to tune the steering system for different design parameters (PAS, friction, gear ratio, etc.). The validation of the HIL setup with real vehicle data need to have more than 85% correlation. The development of advanced EBS and vehicle dynamics control systems requires significant resources and testing. Even in the most controlled environment, on-track vehicle tests are not repeatable. This tool is useful for control system development and electro-mechanical actuator development. In this paper, to accelerate the EPS development for compact SUV, a Hardware in the Loop (HIL) simulator with EPS system is presented. The developed HIL simulator environment is employed to implement, develop and evaluate steering effort and steering feel in different vehicle dynamics maneuver. The prepared simulator allows realistic, real-time evaluation of mobility and performance benefits over simulated actual routes in a safe lab setting before actual deployment in an experimental vehicle. To show the capabilities of the designed HIL simulator with Carsim vehicle dynamic model, which reduce the development time, cost and improves performance of the vehicle.
The current simulation models of EV and ICE Vehicles are well known in industry for their use in estimating the fuel economy or Range benefits because of controller calibrations and component sizing. However, there is a gap in understanding the behavior of accessories such as HVAC, power steering and other such auxiliary loads and the energy losses associated with them. Impact of thermal behavior of electronics on vehicle range also needs to be studied in detail. These kinds of studies help OEM and tier 1 manufactures in improving their design concepts significantly with minimum cost and development time. Hence, the focus of this study is on building simulation models of thermal, electrical, traction and control circuits of a typical electric vehicle. These models are then integrated, and analysis is performed to understand vehicle system level performance metrics. Individual models have been built for HVAC and thermal circuit of on EV in AMESim, HV and LV electrical power distribution in Simulink and for vehicle powertrain using powertrainblockset in Simulink. The aim of this paper is to demonstrate the importance of simulation models that capture both traction, accessories and energy consumption split between them. Different challenges in building, integrating and cosimulation of models, impact of model fidelities on runtimes and accuracy of results have been discussed. Modelling aspects related to HVAC, cooling and heating loops of electronics devices, battery and traction control, are also included. Finally, the results over a typical drive cycle are presented.
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