Browse Topic: Hydraulic control
High-temperature hydraulic control in a Formula 1 drivetrain requires dimensional stability, controlled sealing force, and resistance to wear under sustained pressure cycling. Inside the limited-slip differential, the sealing architecture plays a defined mechanical role in maintaining consistent torque management under race conditions. In Formula 1, drivetrain reliability and performance are closely linked. The limited-slip differential (LSD) governs torque distribution between the rear wheels, allowing controlled transfer of power to the wheel with greater available grip. By limiting speed difference across the rear axle, the differential contributes directly to traction and cornering behavior, particularly where grip levels vary across the vehicle. At the center of this assembly is a hydraulic actuator that clamps a friction clutch inside the differential. The actuator modulates clutch engagement to redirect torque as grip levels change through corner entry, mid-corner load transfer, and acceleration on exit. Its performance depends on precise hydraulic control, which in turn depends on sealing integrity. Within this system, seal integrity is paramount, as significant leakage could cause a catastrophic loss of system function and force the team to retire the car.
The Tractor is essential in both agriculture and construction, equipped with a variety of implements for different operational conditions. Its hydraulic system is crucial for controlling these implements during fieldwork and transport. The quadrant assembly is a key part of the tractor’s hydraulic control system, allowing the operator to manage important functions. This includes hydraulic control and draft control, enabling the farmer or operator to use the PC and DC levers to adjust the movement of implements during various tasks. Tractors are commonly used in fields and farms where the soil can be loose and muddy, particularly during wet puddling operations. In these muddy conditions, tractors can accumulate mud in critical components, such as the quadrant assembly. This can lead to functional issues, increased friction, and problems within the hydraulic system, especially affecting the controls for hydraulics and lever shifting for implement handling. As a result, operators may need to exert more manual effort to operate the lever due to the added frictional forces. This paper addresses the challenges encountered with the current quadrant design and presents an innovative solution to resolve these issues. The existing quadrant assembly consists of a PC tube and DC shaft mounted on the same axis, while the proposed design utilizes a tandem or split shaft arrangement. This new configuration minimizes relative motion between moving linkage parts and facilitates easier maintenance access. Virtual simulations using CAE tools were conducted to validate the new design’s components, and multiple design iterations were performed to meet durability standards. Ultimately, the final innovative tandem quadrant assembly design has been filed for an Indian patent grant. This approach can be applied to all tractor quadrant assemblies to achieve optimal designs that reduce manual effort and improve the system’s mechanical advantage.
In recent days the usage of Electro - Hydraulic Control Unit (EHCU) is increased acutely in light passenger vehicle applications apart from the passenger cars. The main advantage of using electro - Hydraulic control unit (EHCU) is operational flexibility, consistent performance customization, increase durability and lower running cost. During running, the mechanical load is converted into the electronic signal by using transmitter. The electronic devices are highly responsive when compared with mechanical devices, so, it is necessary to reduce the Noise, Vibration and Harshness (NVH) in the system. As per the recent trend, the NVH pollution should be as low as possible in the vehicle. It is necessary to maintain the NVH in minimum level in the electronic device to meet the overall performance of the system. The vibrational isolator is one of the key components used in Electro – Hydraulic Control Unit to reduce the noise and vibration implication of the system. The process of using vibration isolator with hyper-elastic material is highly nonlinear dynamic and complex in nature. It acts as an insulation between EHCU and external system. In this study, vibration characteristics of the EHCU is determined using Finite Element Analysis (FEA) considering rubber isolator which is made up of hyper-elastic material. In this study there are two damping factors like material damping and structural damping are considered to predict the vibrational behavior of the system. Also, the results are compared with lab validation test results and the damping factors are standardized for future reference.
This SAE Aerospace Information Report presents the following factors that affect hydraulic pump life and performance: a The need to supply hydraulic fluid at the correct pressure and quality to the pump inlet port b Considerations for the pump output c Factors to be considered for the pump case drain lines d The mounting of the hydraulic pump e Hydraulic fluid properties, including cleanliness
This SAE Standard includes only those towing winches commonly used on skidders and crawler tractors. These winches are used on self-propelled machines described in SAE J1057, J1116, and J1209. Specifically excluded are those winches used for hoisting operations.
Dual Clutch Automatic Transmission (DCT) has the characteristics of light weight, fast shift speed and high transmission efficiency. Electric vehicles equipped with dual clutch transmission can effectively improve vehicle power performance and economy. Electro-hydraulic control system, as a key component of transmission, determines the quality of shift. In this paper, an electro - hydraulic control system is designed based on two - speed dry dual clutch transmission of electric vehicle. Firstly, the hydraulic components of the system were selected and calculated based on the vehicle parameters. Secondly, the electro-hydraulic control system of the dual clutch transmission was established according to the transmission control strategy and the matching hydraulic valve body assembly was designed. Then, the key components of the system were simulated to analyze their dynamic shift characteristics and response characteristics. Finally, through various tests, it is verified that the designed electro-hydraulic control system and transmission meet the design requirements. The results show that the electro-hydraulic control system can meet its working characteristics and shift requirements.
In order to meet upcoming emission targets, an increasing number of ships using Liquefied Natural Gas (LNG) as fuel have been put into service. In this context, many shipowners are particularly interested in the dual-fuel (DF) large-engine technology, which enables ships to operate with both gaseous and conventional liquid fuels. The use of different combustion principles in DF engines requires a layout of the base engine with a relatively low compression ratio (CR) for the gas mode to prevent unstable combustion (knocking). However, this layout leads to disadvantages in the Diesel operation mode, which requires a higher CR for optimal fuel efficiency. Therefore, a two-stage variable compression ratio (VCR) system is a technology particularly suitable for DF engines. It allows to reduce fuel costs by approximately 5.5%. This article presents an innovative VCR connecting rod (conrod) design for modern DF engines that adapts the piston position by changing the effective conrod length. The VCR system is developed by the Institute for Combustion Engines of the Rheinisch-Westfälische Technische Hochschule (RWTH) Aachen University together with Forschungsgesellschaft für Energietechnik und Verbrennungsmotoren (FEV) Europe GmbH. It is equipped with a novel functional principle inside the conrod’s small eye specifically tailored to large engine boundary conditions. The system includes an advanced hydraulic circuit combining the function of a hydraulic freewheel, the oil supply for piston cooling, and a mechanical locking device (LD) for both CRs. In a comprehensive simulation study, the layout and the system behavior of the new hydraulic circuit are presented using a one-dimensional (1D) hydraulic-mechanical simulation model, which was validated in advance with measurement data from a passenger car (PC) engine. The study intends to examine the functional behavior of the VCR system during engine operation. The focus is on the switching process between the two CRs, as well as on the fixed CR operation. The aim is to provide a deeper understanding of the hydraulic-mechanical behavior and to identify special requirements on the system.
With the development of intelligent and electric vehicles, higher requirements are put forward for the active braking and regenerative braking ability of the braking system. The traditional braking system equipped with vacuum booster has difficulty meeting the demand, therefore it has gradually been replaced by the integrated braking system. In this paper, a novel Integrated Braking System (IBS) is presented, which mainly contains a pedal feel simulator, a permanent magnet synchronous motor (PMSM), a series of transmission mechanisms, and the hydraulic control unit. As an integrative system of mechanics-electronics-hydraulics, the IBS has complex nonlinear characteristics, which challenge the accurate pressure control. Furthermore, it is a completely decoupled braking system, the pedal force doesn’t participate in pressure-building, so it is necessary to precisely identify driver’s braking intention. To improve the control accuracy of the system, this paper proposed a novel pressure control strategy based on driver braking intention identification. Firstly, the structure and working principle of the novel integrated braking system was introduced. Secondly, the driver's braking intention identification strategy was designed. Thirdly, Considering the nonlinear and dynamic characteristics of the system, a cascade closed-loop control strategy including a pressure loop by the feedforward-feedback method, a position loop by the sliding-mode control method, and current loop with friction compensation was proposed. Finally, based on dSPACE products, a hardware-in-the-loop (HiL) experimental bench was built for algorithm verification. The HiL experiment results show that the pressure control strategy has the advantages of accurate response, the braking system pressure follows the driver's expected pressure well.
The RADIALcvt is a traction drive continuously variable transmission (CVT) implemented in a new novel radial configuration mechanical assembly. The RADIALcvt functions as a multi-parallel power path (at least six) type of CVT, which consists of only one steel-on-steel, line contact, traction drive interface in each power path. A constant input radius on the traction drive input makes it possible to use a constant clamping force, which is provided by mechanical springs, thus eliminating the need for a hydraulic control system. The RADIALcvt has a very large radius variation on the traction drive output, which provides the ratio variation. The test and simulation results of the first RADIALcvt prototype was published in [1] and presented mechanical efficiencies above 90%. This article presents the simulation and test results of the second-generation RADIALcvt prototype, which presents mechanical efficiencies above 94% and includes measured parameters of mechanical efficiency, slip, traction curves, and ratio torque at different loads while providing excellent partial load versus mechanical efficiency properties. A methodology for predicting the efficiency map using the no load torque loss is also proposed.
This study aims to solve the problem of impact in a parallel hybrid electric system based on the continuously variable transmission (CVT) during switching from pure electric mode to engine-driven, power-generating mode. Taking into account the torque response characteristics of the engine and motor and the dynamic characteristics of the wet clutch hydraulic control system, the mode switching process is divided into six stages, namely, pure electric mode, wet-clutch free travel, engine start-up, engine speed synchronization, clutch combination, and engine intervention drive. A coordination control strategy is developed based on the model predictive control algorithm to ensure smooth mode switching. The effectiveness of the control algorithm is verified using Matlab/Simulink and the AMESim co-simulation platform. Results show that with the mode switching coordination control strategy, the components of the system work harmoniously. The maximum impact is reduced by 52.0% at the speed synchronization stage and by 84.3% at the clutch coupling stage compared with the uncoordinated control situation.
The latest trend in transmission hydraulic controls development ise body integrated direct acting control solenoid, ted by multiple automotive OEMs. The advantages of integrated direct acting control solenoids are key enablers for OEMs to meet more and more stringent fuel economy requirement and competitive environment. In the meantime, there are unique challenges in both designing and manufacturing of such solenoids, due to the fact the solenoid armature can only push the spool valve with limited force and limited stroke. Through analytical methods, this paper explains design guidelines to overcome the challenges and quantifies the impact of design decision to critical functional objectives. Multiple valve design configurations, including both normally low and normally high functionality, are covered in the analysis. Unique manufacturing process concerns are also addressed.
SAE J1939-2 specifies the requirements for application of SAE J1939 in agricultural and forestry equipment. This document specifies the series of documents within the set of SAE J1939 documents that are applicable to agricultural and forestry equipment and provides further requirements for this industry. The SAE and ISO groups have cooperated to define agricultural and forestry networks in a manner to allow compatibility of ECUs and messaging protocols between the A&F and the T&B networks.
In the process of ABS control, the Anti-lock braking system (ABS) of the vehicle adjusts the wheel cylinder brake pressure through the hydraulic actuator so as to control the movement of the wheel. The high-speed on-off valve (HSV) is the key components of the Anti-lock braking system. HSV affects the performance of the hydraulic actuator and the valve response characteristics affects the Anti-lock braking system pressure response as well as braking effect. In this paper, the electromagnetic field theory and flow field theory of HSV are analyzed, and simulation analysis of electromagnetic field characteristics of HSV is done by ANSYS. Combined with the ANSYS analysis results, a precise physical model of HSV is constructed in AMESim. Meanwhile, the valve response characteristics are analyzed. Moreover, the influence of different wheel cylinder diameter and PWM carrier frequency on hydraulic braking force characteristics are analyzed. The open-loop control methods of hydraulic braking force based on Look-up tables and T-S fuzzy structure are comparatively analyzed. The results show that T-S fuzzy controller can be more direct and rapid training to obtain buck-boost surface without fitting and interpolation of data surface, it is more adaptable. The single-wheel model and ABS sliding mode control module are established in Simulink. The inner ring of the module is hydraulic brake force controller, it is used to control hydraulic braking force precisely. The outer ring of the module is a sliding mode controller to control the wheel slip rate. Based on the above two open-loop control strategies, ABS control can be better achieved to realize anti-lock control of the vehicle in the emergency braking conditions.
An investigation was completed into the power loss associated with a rotating feed-through (RFT) design feature used to transfer lubrication and a hydraulic control signal from the static reference frame to a rotating reference frame in the NASA GRC two-speed transmission tests conducted in the Variable-Speed Drive Test Rig. The RFT feature, not commercially available, was created specifically for this research project and is integral to all two-speed transmission configurations tested, as well as a variant concept design for a geared variable-speed transmission presented at AHS Forum 71 in 2015. The experimental set-up and results from measurements in the isolated rotating-feed-through (RFT) experiments are presented. Results were used in an overall power loss assessment for a scaled conceptual 1,000 horsepower inline concentric two-speed transmission to support a NASA Revolutionary Vertical Lift Technologies (RVLT) Technical Challenge, demonstrating 50% speed change with less than 2% power loss while maintaining current power-to-weight ratios.
This SAE Standard includes only those towing winches commonly used on skidders and crawler tractors. These winches are used on self-propelled machines described in SAE J1057, J1116, and J1209. Specifically excluded are those winches used for hoisting operations.
Fuel economy regulations have forced the automotive industry to implement transmissions with an increased number of gears and reduced parasitic losses. The objective of this research is to develop a high fidelity and a computationally efficient model of an automatic transmission, this model should be suitable for controller development purposes. The transmission under investigation features a combination of positive clutches (interlocking dog clutches) and conventional wet clutches. Simulation models for the torque converter, lock-up clutch, transmission gear train, interlocking dog clutches, wet clutches, hydraulic control valves and circuits were developed and integrated with a 1-D vehicle road load model. The integrated powertrain system model was calibrated using measurements from real-world driving conditions. Unknown model parameters, such as clutch pack clearances, compliances, hydraulic orifice diameters and clutch preloads were estimated and calibrated. Simulation results, such as vehicle acceleration, turbine speed, and output shaft speed, are reported and compared with the measured data to validate the transmission model. Subsequently, the transmission model was coupled with internal combustion engine and road load models. This arrangement permitted investigating the dog clutch engagement dynamics under transient conditions. The relative speed of the dog clutch halves was found to be highly sensitive to the transmission input torque, which indicates that a precise engine torque control schemes are necessary for successful engagement.
Tractor hitch control system is used for attaching and operating various Agricultural Implements and for operating tipping trailer. The system has also got provision to attach additional Aux valves for rear and front mounted attachments. The rear mounted implements are coupled to the tractor using Three Point Linkage (3PL) System. The hitch hydraulics system consists of hydraulic pump, filter, piping’s, fittings and hydraulics lift unit. Hydraulics lift unit consists of a proportional control valve, cylinder, piston and power linkages. Conventional control valve is hydro mechanical part operated by mechanical linkages. The control valve and linkages plays major role in performance of hydraulics system. Hydraulics is required to operate in extreme conditions of soils such as very soft like sand to very hard like black cotton sand. These two extreme conditions makes linkage and control valve optimization work very challenging and very difficult to get single solution for soft and hard conditions. In addition to best performance requirements, lesser power loss and operating effort are also important for customer satisfaction. To meet this challenge of high on performance in all soil conditions, effortless operation, high on efficiency (less hydraulics power loss) and aesthetics, Electro Hydraulics Hitch is the best solution. In the present work, Electro Hydraulics Hitch System is designed and developed for Agricultural Tractor to replace conventional hydro mechanical hitch. This system consists of specially made control valve manifold using Solenoid Valves, Hydraulic Control Unit (HCU), Position Sensor, Draft Sensor (Load Cell) and input levers with sensors. They are connected by using suitable wiring harness. The system is having all features functions i.e. Position Control (PC), Draft Control (DC) and Quick Lift (QL) of conventional system. The basic common valves like, Pressure Relief Valve (PRV), Check Valve (CV), Shock Load relief Valve (SLRV), Isolator valve and Tipping trailer port are adopted from current design. The customer touch points are maintained same as that of conventional type i.e. PC, DC levers and QL button. The work also includes analysis and optimization using Simulink Matlab, performance tests in lab and fields for proving in various soil conditions.
The use of hybrid, fuel cell electric, and pure electric vehicles is on the increase as part of measures to help reduce exhaust gas emissions and to help resolve energy issues. These vehicles use regenerative-friction brake coordination technology, which requires a braking system that can accurately control the hydraulic brakes in response to small changes in regenerative braking. At the same time, the spread of collision avoidance support technology is progressing at a rapid pace along with a growing awareness of vehicle safety. This technology requires braking systems that can apply a large braking force in a short time. Although brake systems that have both accurate hydraulic control and large braking force have been developed in the past, simplification is required to promote further adoption. This paper describes the following three items: (1) an examination of the brake system functions that realize the regenerative-friction brake coordination and collision avoidance support functions, (2) considerations and a proposal for a brake system that achieves the functions described in item (1) with a simple structure, and (3) development of core technology for controlling the wheel cylinder pressure in a brake system equipped with a hydraulic regulator.
With the development of vehicle electrification, electronic hydraulic brake system is gradually applied. Many companies have introduced products related to integrated electronic hydraulic brake system (I-EHB). In this paper, an I-EHB system is introduced, which uses the motor to drive the reduction mechanism as a power source for braking. The reduction mechanism is composed of a turbine, a worm, a gear and a rack. A control method based on command feed-forward is proposed to improve the hydraulic pressure control of I-EHB. Based on previous research, we simplify the system to first order system, and the theoretical design of the command feed-forward compensator is carried out. The feed-forward controller is applied, including the velocity feed-forward and the acceleration feed-forward, to improve the response speed and tracking effect of the system. Then, related experiments were carried out on test bench to track three different types of target signal (different amplitude and frequency), step signal, sine wave signal and triangular wave signal. Compared with the test result of PID control method, the proposed method has the advantages of fast response and short regulation time. And the Control error at low frequency of the method is about 2 bar - reduced by 56% compared with PID control. Therefore, this method can effectively control the Hydraulic pressure of integrated electronic hydraulic brake system.
With the electrification and intelligentialization of vehicle, requirements on more intelligent and integrated brake system are put forward. A novel integrated-electro-hydraulic brake system (I-EHB) for automotive is presented to fulfill these requirements. I-EHB is consisted of active power source (APS), pedal feel emulator (PFE), electro control unit (ECU) and hydraulic control unit (HCU). The system characteristics of I-EHB are tested through test rig. According to characteristics experiments, friction and non-linear phenomena in hydraulic pressure control are found. In order to overcome these phenomena in control of I-EHB, chatter-compensation is adopted based on experiment analysis. Algorithm are tested and optimized through test rig. As a result, through chatter-compensation the hydraulic pressure is controlled accurately and chatter-compensation is optimized for different working conditions.
During the vehicle braking, the Regenerative braking system (RBS) transforms the kinetic energy into electric power, storing it in the power sources. To secure the baking process, it is required to use hydraulic braking pressure to coordinately compensate the regenerative braking pressure. The traditional hydraulic pressure control algorithm which is used in regenerative braking system coordinated control has obvious laddering effect in braking. Unit control cycle pressure deviations seriously affect the comfort and the braking feeling on the vehicle. In order to ensure the accurate implementation of the brake pressure on the wheel cylinder, according to the hardware configuration of regenerative braking system, this paper analyzes the active pressurization state of RBS during braking, acquires the overflow characteristics of the switch valve in ESP hydraulic control unit by designing of high frequency characteristic test experiment, the control range of valve core displacement in the state of inlet valve differential pressure balanced and the relationship between pressure growing rate and inlet valve control duty ratio under the different states of wheel cylinder pressure. On this basis, this paper finishes the development of algorithm of active pressurization control, building the hardware-in-loop testing platform. The test result shows that the actual wheel cylinder pressure can follow the aiming wheel cylinder well, the differential of wheel cylinder can be controlled in the range from −5Bar to 5Bar, the whole pressurization rate follows well compared with traditional control algorithm, justifies the feasibility of the active pressurization control algorithm through the virtual cycle.
High speed on-off valve is applied widely in vehicle control systems. When high speed on-off valve is controlled by Pulse Width Modulation (PWM) of high frequency, the valve core can float at a certain position which is adjusted by changing the duty ratio within a certain effective range. Then the high speed on-off valve can control the flow and pressure linearly like proportional valve. Thus it is essential to extend the effective range of duty ratio to improve the linear control performance of high speed on-off valve. In this paper, the high speed on-off valve of the automotive Electronic Stability Program (ESP) is the focus, and its flow force is analyzed in detail to get the effects of hydraulic parameters on the valve performance. The mathematic model of the high speed on-off valve is derived. Then the valve structural parameters are optimized according to the Genetic Algorithm(GA), offering the theoretical references for extending the effective duty ratio of PWM. Besides, the simulation model of high speed on-off valve is established in MATLAB/Simulink, and then embedded in the Hydraulic Control Unit (HCU) simulation model established in AMESim, resulting in the co-simulation model of hydraulic actuator. Finally the simulation model is verified by the hardware-in-loop tests. Based on theoretical analysis, simulations and tests, it is critical to increase the range of flow force for extending the effective range of duty ratio. The pressure difference, the valve seat angle and the throttle diameter of the high speed on-off valve have great effects on the flow force. At last the effects of structural parameters of the high speed on-off valve on extending the range of the linear control are proposed, serving as references for improving the linear control performance of high speed on-off valve.
The permanent-magnet DC motor, which is directly connected to the hydraulic pump, is a significant component of hydraulic control unit (HCU) in an anti-lock braking system (ABS). It drives the pump to dump the brake fluid from the low-pressure accumulator back to master cylinder and makes sure the pressure decreases of wheel cylinder in ABS control. Obviously, the motor should run fast enough to provide sufficient power and prevent the low-pressure accumulator from fully charging. However, the pump don't need always run at full speed for the consideration of energy conservation and noise reduction. Therefore, it is necessary to accurately regulate the speed of the DC motor in order to improve quality of ABS control. In this paper, an accurate speed control algorithm was developed for the permanent-magnet DC motor of the ABS to implement the performance of the system, reduce the noise and save the energy in the meanwhile. Firstly, the hydraulic brake system and the DC motor models of the ABS were established in the AMESim and Matlab/Simulink respectively, and the data exchange was realized through AMESim special interface module and MATLAB S function. Then, the co-simulation model was validated by the experiment data. Furthermore, an accurate speed control algorithm for DC motor was developed based on the charging state of the low-pressure accumulator, and a pulse width modulation (PWM) method was proposed to control the speed of DC motor. Finally, the proposed algorithm was simulated in the co-simulation platform to verify the decompression response speed of the wheel cylinder and the energy consumption of the DC motor. The results show that accurate speed control algorithm can effectively reduce the power consumption of the motor, at the same time ensure the performance of ABS control system.
A new electrohydraulic steering technology offers energy efficiency improvements, increased productivity, enhanced safety, and adaptability to operating conditions, while also providing the capacity to support remote operation of a compact wheel loader. Remotely operated machines have been researched and developed in various industry sectors including military, automotive, agriculture, aerospace, and construction, to name a few. Remote operation is desired where conditions are deemed too hazardous for human operators to perform, as is the case with explosive mines, radioactive sites, outer space missions, and oil drilling structures. On the other hand, when the nature of the work performed is repetitive and requires less complex decision-making and problem-solving skills, autonomous operation can provide a viable alternative. Multiple researchers, in both academia and industry, have probed remote and autonomous operation of machines over the past few decades. A tele-operated skid steer loader was developed with two operator-machine interfaces and compared against a manually operated machine. Testing results demonstrated acceptable performance of the first interface employing a laptop computer with a steering wheel. Testing also showed that the operator-machine interface choice was task dependent, and handheld-computer control yielded good results in specific cases only.
Programs are helping hydraulic systems do more while reducing operator workloads. Digital controls continue to expand their reach, impacting everything from the intricacies of engine operations to the interactions between operator and machine. This takeover has driven an explosion in the amount of software running on all types of electronic control units (ECUs). Electrohydraulic systems have seen significant growth as most vehicles' overall volume of software soared. Programs control valves and other equipment, interact with operators, and ensure that safety regulations are met.
Closer links between powertrains and hydraulic systems cut fuel usage and emissions while improving efficiency. As regulations including Tier 4 further restrict fuel consumption requirements, design teams are tightening the links between powertrains and hydraulic systems. Improving communications between the two can bring significant savings while also reducing size and weight. Advanced electronics permit matching the hydraulics demand and the engine load, which cuts fuel usage while improving hydraulic performance. Engines can run in their sweet spots longer and hydraulic systems can deliver power more quickly when they don't have to wait for engines to rev up. These revisions also help trim emissions.
Modern on-road vehicles have been making steady strides when it comes to employing technological advances featuring active safety systems. However, off-highway machines are lagging in this area and are in dire need for modernization. One chassis system that has been receiving much attention in the automotive field is the steering system, where several electric and electrohydraulic steering architectures have been implemented and steer-by-wire technologies are under current research and development activities. On the other hand, off-highway articulated steering vehicles have not adequately evolved to meet the needs of Original Equipment Manufacturers (OEM) as well as their end customers. Present-day hydrostatic steering systems are plagued with poor energy efficiency due to valve throttling losses and are considered passive systems relative to safety, adjustability, and comfort. This paper introduces a novel scheme of an electro-hydraulic power steering system that utilizes a proven energy-saving technology, pump displacement control, which eliminates throttling losses associated with hydraulic control valves by controlling the displacement of a variable displacement pump. This new architecture lends itself to high energy efficiency resulting in lower fuel consumption and reduced emissions, higher machine productivity and reduced operator fatigue, and active safety functions that counteract instabilities and reject disturbances.
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