Fault simulator for proportional solenoid valves

Proportional Solenoid Valves (PSV) have been successfully used in the hydraulic industry for many years due to the benefits associated with higher accuracy compared to on/off solenoid valves, and the robustness and cost compared to servo valves. Because the PSV plays an important role in the performance of a hydraulic system, a technique commonly referred to as Condition Monitoring Scheme (CMS) has been used extensively to monitor the progress of faults in the PSV. But before any CMS can be implemented on a system, it needs to be thoroughly tested for its reliability of fault detection since, a failure of the CMS to detect any potential fault can be economically disastrous, and dangerous in terms of the safety of personnel. The motivation of this research was to develop a fault simulator which could reliably and repeatedly induce user defined faults in the PSV and thereby aid in testing the efficacy of the CMS for monitoring such simulated faults.Industry research has revealed that the most common mode of failure in spool valves is an increase in the friction between the spool and valve, due to wear, contamination and dirt, which renders the valve inoperable. In this research, a non-destructive fault simulator was developed which induced artificial friction faults in the PSV. The PSV consisted of two solenoids on the opposite sides of the valve spool by virtue of which, bi-directional position control could be achieved. The PSV with the spool and one of the solenoids was used as the system in which the faults were simulated, and the second solenoid was used an a fault simulator for inducing the desired friction characteristics in the system. The friction characteristics induced in the valve were similar to those in the classical friction curve, i.e., stiction at low velocities and Coulomb and viscous friction at higher velocities. By employing a closed loop position control scheme, one of the solenoids was used to generate a linearly increasing velocity profile by virtue of which the desired friction characteristics could be induced in different velocity regimes. The other solenoid was used to generate the desired friction force. A closed loop force control strategy, which used the feedback from a force transducer, allowed for the accurate control of the friction characteristics. stiction was induced at low velocities by passing the required current in both the solenoids that resulted in no net force on the valve spool. Due to the absence of any driving force the spool was stalled at the desired location, thus achieving the same effect of stiction at low velocities. The coulomb and viscous friction were induced at higher velocities by employing an algorithm which was a function of the spool velocity. Different magnitudes of static, coulomb and viscous friction were induced to achieve the friction characteristics represented by the classical friction curve. Since the change in force characteristics of the valve results in a corresponding change in the current drawn by the position control solenoid, a rudimentary CMS for monitoring the current characteristics is presented. Based on the experimental results and validation using the CMS it was concluded that the fault simulator was able to accurately produce the desired frictional loading on the valve spool and was able to do so with a high degree of repeatability. Proportional Solenoid Valves (PSV) have been successfully used in the hydraulic industry for many years due to the benefits associated with higher accuracy compared to on/off solenoid valves, and the robustness and cost compared to servo valves. Because the PSV plays an important role in the performance of a hydraulic system, a technique commonly referred to as Condition Monitoring Scheme (CMS) has been used extensively to monitor the progress of faults in the PSV. But before any CMS can be implemented on a system, it needs to be thoroughly tested for its reliability of fault detection since, a failure of the CMS to detect any potential fault can be economically disastrous, and dangerous in terms of the safety of personnel. The motivation of this research was to develop a fault simulator which could reliably and repeatedly induce user defined faults in the PSV and thereby aid in testing the efficacy of the CMS for monitoring such simulated faults. Industry research has revealed that the most common mode of failure in spool valves is an increase in the friction between the spool and valve, due to wear, contamination and dirt, which renders the valve inoperable. In this research, a non-destructive fault simulator was developed which induced artificial friction faults in the PSV. The PSV consisted of two solenoids on the opposite sides of the valve spool by virtue of which, bi-directional position control could be achieved.The PSV with the spool and one of the solenoids was used as the system in which the faults were simulated, and the second solenoid was used an a fault simulator for inducing the desired friction characteristics in the system. The friction characteristics induced in the valve were similar to those in the classical friction curve, i.e., stiction at low velocities and Coulomb and viscous friction at higher velocities. By employing a closed loop position control scheme, one of the solenoids was used to generate a linearly increasing velocity profile by virtue of which the desired friction characteristics could be induced in different velocity regimes. The other solenoid was used to generate the desired friction force. A closed loop force control strategy, which used the feedback from a force transducer, allowed for the accurate control of the friction characteristics. stiction was induced at low velocities by passing the required current in both the solenoids that resulted in no net force on the valve spool. Due to the absence of any driving force the spool was stalled at the desired location, thus achieving the same effect of stiction at low velocities. The coulomb and viscous friction were induced at higher velocities by employing an algorithm which was a function of the spool velocity. Different magnitudes of static, coulomb and viscous friction were induced to achieve the friction characteristics represented by the classical friction curve. Since the change in force characteristics of the valve results in a corresponding change in the current drawn by the position control solenoid, a rudimentary CMS for monitoring the current characteristics is presented. Based on the experimental results and validation using the CMS it was concluded that the fault simulator was able to accurately produce the desired frictional loading on the valve spool and was able to do so with a high degree of repeatability

A series elastic brake pedal for improving driving performance under regenerative braking

Electric and hybrid vehicles are favored to decrease the carbon footprint on the planet. The electric motor in these vehicles serves a dual purpose. The use of electric motor for deceleration, by converting the kinetic energy of the vehicle into electrical energy to be stored in the battery is called regenerative braking. Regenerative braking is commonly employed by electrical vehicles to signi cantly improve energy e ciency and to help to meet emission standards. When the regenerative and friction brakes are simultaneously activated by the driver interacting with the brake pedal, the conventional haptic brake pedal feel is disturbed due to the regenerative braking. In particular, while there exists a physical coupling between the brake pedal and the conventional friction brakes, no such physical coupling exists for the regenerative braking. As a result, no reaction forces are fed back to the brake pedal, resulting in a unilateral power ow between the driver and the vehicle. Consequently, the relationship between the brake pedal force and the vehicle deceleration is strongly in uenced by the regenerative braking. This results in a unfamiliar response of the brake pedal, negatively impacting the driver's performance and posing a safety concern. The reaction forces due to regenerative braking can be fed back to the brake pedal, through actuated pedals that re-establish the bilateral power ow to recover the natural haptic pedal feel. We propose a force-feedback brake pedal with series elastic actuation to preserve the conventional brake pedal feel during regenerative braking. The novelty of the proposed design is due to the deliberate introduction of a compliant element between the actuator and the brake pedal whose de ections are measured to estimate interaction forces and to perform closed-loop force control. Thanks to its series elasticity, the force-feedback brake pedal can utilize robust controllers to achieve high delity force control, possesses favorable output impedance characteristics over the entire frequency spectrum, and can be implemented in a compact package using low-cost components. We introduce pedal feel compensation algorithms to recover the missing regenerative brake forces on the brake pedal. The proposed algorithms are implemented for both two-pedal cooperative braking and one-pedal driving conditions. For those driving conditions, the missing pedal feedback due to the regenerative brake forces are rendered through the active pedal to recover the conventional pedal force mapping. In two-pedal cooperative braking, the regenerative braking is activated by pressing the brake pedal, while in one-pedal driving the activation takes place as soon as the throttle pedal is released. The applicability and e ectiveness of the proposed series elastic brake pedal and haptic pedal feel compensation algorithms in terms of driving safety and performance have been investigated through human subject experiments. The experiments have been conducted using a haptic pedal feel platform that consists of a SEA brake pedal, a torque-controlled dynamometer, and a throttle pedal. The dynamometer renders the pedal forces due to friction braking, while the SEA brake pedal renders the missing pedal forces due to the regenerative braking. The throttle pedal is utilized for the activation of regenerative braking in one-pedal driving. The simulator implements a vehicle pursuit task similar to the CAMP protocol and provides visual feedback to the participant. The e ectiveness of the preservation of the natural brake pedal feel has been studied under two-pedal cooperative braking and one-pedal driving scenarios. The experimental results indicate that pedal feel compensation can signi cantly decrease the number of hard braking instances, improving safety for both two-pedal cooperative braking and one-pedal driving. Volunteers also strongly prefer compensation, while they equally prefer and can e ectively utilize both two-pedal and one-pedal driving conditions. The bene cial e ects of haptic pedal feel compensation on safety is evaluated to be larger for the two-pedal cooperative braking condition, as lack of compensation results in sti ening/softening pedal feel characteristics in this cas

The Fourteenth Scandinavian International Conference on Fluid Power, SICFP15: Abstracts

At this time the conference includes various themes like hybrids, drives, digital hydraulics and pneumatics. Special attention in the program is given for energy efficiency, renewable energy production and energy recovery. They are reflecting well the situation, where environmental issues and energy saving are increasingly important issues

Integrated braking control for electric vehicles with in-wheel propulsion and fully decoupled brake-by-wire system

This paper introduces a case study on the potential of new mechatronic chassis systems for battery electric vehicles, in this case a brake-by-wire (BBW) system and in-wheel propulsion on the rear axle combined with an integrated chassis control providing common safety features like anti-lock braking system (ABS), and enhanced functionalities, like torque blending. The presented controller was intended to also show the potential of continuous control strategies with regard to active safety, vehicle stability and driving comfort. Therefore, an integral sliding mode (ISM) and proportional integral (PI) control were used for wheel slip control (WSC) and benchmarked against each other and against classical used rule-based approach. The controller was realized in MatLab/Simulink and tested under real-time conditions in IPG CarMaker simulation environment for experimentally validated models of the target vehicle and its systems. The controller also contains robust observers for estimation of non-measurable vehicle states and parameters e.g., vehicle mass or road grade, which can have a significant influence on control performance and vehicle safety

Performance analysis of variable speed hydraulic systems with large power in valve-pump parallel variable structure control

Aiming at the problems, bad low velocity performance and slow response, existing in variable speed hydraulic systems, this study proposes a variable speed hydraulic system in valve-pump parallel variable structure control, in which control structures vary with control requirement. The leaking parallel valve control is applied to improve low-speed performance at the start and stop stages by increasing damping ratios and compensating the reduction of damping ratios due to the friction negative slop; the replenishing parallel valve control is applied to achieve fast response to load disturbance at the uniform stage with high speed; the variable speed pump control is to make full use its high efficiency at other stages. During the regulation process, these control structures switch smoothly and a good speed tracking is achieved, in addition, the pump provides majority of required flow, so the proposed system still can work efficiently as pump control systems. Therefore, the valve-pump parallel variable structure control establishes a flexible control mechanism by two channels of valve control and pump control, and could improve comprehensive performances of variable speed hydraulic systems with large power, such as low-speed performance, rapid response and high efficiency

Implementation of self-tuning control for turbine generators

PhD ThesisThis thesis documents the work that has been done towards the development of a 'practical' self-tuning controller for turbine generator plant. It has been shown by simulation studies and practical investigations using a micro-alternator system that a significant enhancement in the overall performance in terms of control and stability can be achieved by improving the primary controls of a turbine generator using self-tuning control. The self-tuning AVR is based on the Generalised Predictive Control strategy. The design of the controller has been done using standard off-the-shelf microprocessor hardware and structured software design techniques. The proposed design is thus flexible, cost-effective, and readily applicable to 'real' generating plant. Several practical issues have been tackled during the design of the self-tuning controller and techniques to improve the robustness of the measurement system, controller, and parameter estimator have been proposed and evaluated. A simple and robust measurement system for plant variables based on software techniques has been developed and its suitability for use in the self-tuning controller has been practically verified. The convergence, adaptability, and robustness aspects of the parameter estimator have been evaluated and shown to be suitable for long-term operation in 'real' self-tuning controllers. The self-tuning AVR has been extensively evaluated under normal and fault conditions of the turbine generator. It has been shown that this new controller is superior in performance when compared with a conventional lag-lead type of fixed-parameter digital AVR. The use of electrical power as a supplementary feedback signal in the new AVR is shown to further improve the dynamic stability of the system. The self-tuning AVR has been extended to a multivariable integrated self-tuning controller which combines the AVR and EHG functions. The flexibility of the new AVR to enable its expansion for more complex control applications has thus been demonstrated. Simple techniques to incorporate constraints on control inputs without upsetting the loop decoupling property of the multivariable controller have been proposed and evaluated. It is shown that a further improvement in control performance and stability can be achieved by the integrated controller.Parsons Turbine Generators Ltd

전자유압밸브를 이용한 자율 주행 트랙터 조향성능 향상 연구

학위논문 (석사)-- 서울대학교 대학원 농업생명과학대학 바이오시스템·소재학부, 2017. 8. 김학진.The most common solution to achieving automated steering in an agricultural tractor is the use of an electric motor in parallel with a conventional hydrostatic valve-based hydraulic steering system owing to its simplicity and low cost. However, the existing overlap, or dead band, of a hydrostatic valve has limited its potential benefit to automated tractor steering in terms of providing various agricultural operations, including planting and spraying, at higher speeds. The main objective of this study was to develop an electro hydraulic steering system applicable to an auto-guidance system, and to compare the performance of the developed system with a conventional automatic steering system. A proportional-feedforward control algorithm was implemented to effectively compensate the non-linear behaviors of the hydraulic cylinders used for changing the steered wheel angle of the tractor. A computer-controlled hardware-in-the-loop electro-hydraulic steering simulator consisting of two different types of valve sub-systems s, i.e., hydrostatic valve and EHPV sub-system, was designed and built for the development of the steering control algorithms and to verify the feasibility of the developed steering controller for accurate steering of the system with acceptable response times. A field test was conducted using a Real Time Kinematic GPS based autonomous tractor equipped with the developed EHPV-based steering system and an EPS-based steering system used as a control to compare and investigate their potential in enhancing the path tracking functionality of an auto-guided system. The use of the EHPV-based steering controller was shown to improve the tracking error by about 29% and 50% for straight and curved paths, respectively, as compared to the EPS-based steering system.Chapter 1. Introduction 1 1.1. Study Background 1 1.2. Description of Tractor Steering System 6 1.3. Automatic Steering System 10 1.3.1. Electric Power Steering System 10 1.3.2. Electro Hydraulic Steering System 12 1.4. Review of Literature 13 1.5. Research Purpose 16 Chapter 2. Materials and Methods 17 2.1. Preliminary Performance Test of Conventional Steering System 17 2.1.1. Purpose of Preliminary Test 17 2.1.2. Zero-Load Test 21 2.1.3. Tractor Traveling Test 22 2.2. Hardware-in-the Loop Simulator 24 2.2.1. Hydraulic Circuit 25 2.2.2. Hardware Description 27 2.3. ISO 11783 Network 37 2.3.1. ISO 11783 (ISOBUS) 37 2.4. Steering Control Algorithm 45 2.4.1. Dead Time 48 2.4.2. Dead Band 51 2.4.3. Static Friction 57 2.5. Virtual Terminal 61 2.6. Vehicle Traveling Test 66 2.6.1. Hardware Configurations 66 2.6.2. Trajectory Tracking Control 72 2.6.3. Zero-Load Test 74 2.6.4. Sinusoidal Tracking Test 75 2.6.5. Path-Tracking and Test Methods 76 2.6.6. Evaluation Method of Path Tracking Deviation 79 Chapter 3. Results and Discussion 81 3.1. Preliminary Test Results of EPS-based Hydrostatic Steering System 81 3.2. Experiment Results of Steering Behavior of Hydrostatic Steering System using HIL simulator 85 3.3. Experiment Results of Electrohydraulic Steering System using HIL simulator 81 3.3.1. Dead-Time Approximation 88 3.3.2. Dead-Band Compensation 90 3.3.3. Static Friction Compensation 92 3.3.4. Steering Controller Test under Load Conditions 94 3.4. Performance Evaluation of Tractor Steering System 96 3.4.1. Zero Load Test 96 3.4.2. Sinusoidal Steering Test 96 3.4.3. Path-Tracking Test 99 Chapter 4. Conclusions 107Maste

Automotive suspension system modelling and controlling

In both academic and industrial fields, suspension system modelling and associated control design influence vehicle response. Ideal hydraulic force models have been used in active suspension studies for decades, but few studies have investigated hydraulic effects, which are the core of system force generation. Accurate mathematical subsystem modelling is essential in representing physical subsystems and enhancing design estimation control. This thesis details the mathematical modelling of both passive and active suspension and controller design for a quarter-car test rig. When using a conventional passive model, a significant difference between the experimental and simulation results was found for improved modelling of body movements. This led to an investigation in how to resolve this issue, accordingly, the consideration of a new term (friction force) was researched. Establishing a nonlinear friction force became a vital aspect of this work. In addition, emphasis was placed on hydraulic modelling and unknown model parameters that were experimentally identified. This experimental work is unique and helpful for advancing knowledge of any system. A new approach to implementing the friction force was used to identify the system through the transformation of a ¼ car model to one Degree of Freedom (DOF) and two-DOF models. This reduced the model complexity and allowed the parameters to be identified from a series of transfer functions linking vehicle parts and the hydraulic models. Simulation and experimental results were then compared. The hydraulic component model is crucial to the formulation of accurate active control schemes. Full-state feedback controls were realised by Pole-Assignment (PA) and Linear Quadratic (LQ) optimal method. Simulation results suggest that even though the performance of active suspension designed by the PA method is superior to that of passive suspension, it still possesses a design constraint, similar to a passive system, as the design is a compromise between the effects of natural frequency and transmissibility. With a different design concept, the LQ method provided a better solution as it reduced energy consumption by 65% and effectively shifts the dominant natural frequency to a very low-frequency range. Thus, allowing the damping rate to be increased to its critical value with the smallest effect on transmissibility. iv It was estimated for experimental work that the identified model with the LQ controller might be used to predict the dynamic responses of the actual system within a certain range of the design parameters due to the considerable difference between the initial condition of the test rig and the linearised operating design. The servovalve produced issues that did not allow validation of the controller. Both simulation and experimental results, with several conditions, showed consistent agreement, between experimental and simulation output, consequently confirming the feasibility of the newly approved model for passive and active suspension systems that accounted for the actual configuration of the test rig system. These models, that subsequently implemented the nonlinear friction forces that affect the linear supported body bearings, are entirely accurate and useful. The nonlinear friction model captures most of the friction behaviours that have been observed experimentally. Additionally, the models of the nonlinear hydraulic actuators, covered by the dynamic equation for the servovalve, are moderately precise and practical. The suggested Proportional Integral (PI) control successfully guided the road hydraulic actuator and validated the control strategy. The suggested PA and LQ controllers for active systems successfully guided the system to achieve the targets. Ride comfort and handling response are close to that expected for the passive suspension system with road disturbances, whereas there were clear response enhancements for the active system