Research on the Vibration Damping Performance of a Novel Single-Side Coupling Hydro-Pneumatic Suspension

A mine dump truck is exposed to heavy load and harsh working environment. When the truck passes over the road bumps, it will cause the body to tilt and the tires to "jump off the ground" (JOTG), which will affect the stability and safety of the truck, and will cause impact damage to the body and suspension system. To avoid this situation, a kind of Novel Single-side Coupling Hydro-pneumatic Suspension (NSCHs) is presented. NSCHs consists of two cylinders in parallel, which are connected to the accumulator by rubber pipes and mounted on the same side of the dump truck. Theoretical analysis and experimental research were respectively carried out under the road and loading experimental condition. The experimental results show that compared to the conventional single cylinder hydro-pneumatic suspension, under the loading experiment condition, the maximum overshoot pressure of the NSCHs was reduced by 0.4 MPa and the impact oscillation time was shortened by 4.13 s, which plays the effective role in reducing vibration and absorbing energy. Further, it is found that the two cylinders are coupled during the working process, and the NSCHs system can achieve uniform loading and displacement compensation, thus the novel dump truck can avoid the occurrence of the JOTG phenomenon

Dynamic impact of ageing dump truck suspension systems on whole-body vibrations in high-impact shovel loading operations

Surface mining operations typically deploy large shovels, with 100+ tons per pass capacity, to load dump trucks in a phenomenon described as high-impact shovel loading operations (HISLO). The HISLO phenomenon causes excessive shock and vibrations in the dump truck assembly resulting in whole body vibration (WBV) exposures to operators. The truck suspension system performance deteriorates with time; therefore their effectiveness in attenuating vibrations reduces. No research has been conducted to study the impact of ageing suspension mechanisms on the magnitudes of WBV in HISLO operations. This study is a pioneering effort to provide fundamental and applied knowledge for understanding the impact of ageing on the magnitudes of WBV exposures. The effects of underlying ageing processes on a suspension performance index are mathematically modeled. The effects of scheduled maintenance and corrective maintenance on improving the performance index (PI) are also modeled. Finally, the proposed mathematical ageing model is linked to the truck operator\u27s exposure to WBVs via a virtual prototype CAT 793D truck model in the MSC ADAMS environment. The effects of suspension system ageing in increasing the WBV levels are examined in the form of both the vertical and horizontal accelerations under HISLO conditions. This study shows that the hydro-pneumatic suspension strut ageing results in deteriorating stiffness-damping parameters. The deteriorating suspension performance (with time) introduces more severe and prolonged WBVs in HISLO operations. The RMS accelerations increase significantly with time (suspension ageing). The vertical RMS accelerations increase to severe magnitudes of over 3.45, 3.75, and 4.0 m/s2 after 3, 5, and 7 years, respectively. These acceleration magnitudes are well beyond the ISO limits for the human body\u27s exposure to WBVs. This pioneering research effort provides a frontier for further research to provide safe and healthy working environments for HISLO operations --Abstract, page iii

An innovative design of actuation mechanism for active seat suspension of an off-road vehicle

In recent years human-machine interaction attracts scientific community attention because of human quality and health issues. Driver seat should be designed so that it would ensure occupational health as well as increase work efficiency. The aim of this research is to maintain seat height at constant level with regard to chassis excitation at different levels of frequency and amplitude by means of new design of pneumatic actuation circuit. Sinusoidal function was used for base vibration since almost all of excitation functions can be derived from it. System response shows in low frequency/high amplitude and high frequency/low amplitude chassis vibration, transmissibility decreased about 60% and 40% compared to solid suspension respectivel

Study on Vibration Characteristics and Human Riding Comfort of a Special Equipment Cab

Special equipment drivers often suffered from vibration which threatened their physical and mental health. In order to study the riding comfort of a special equipment cab, a hammering experiment has been carried out on it by acceleration sensors. According to the test results, the natural frequency has been calculated which was compared with the result analysis by the finite element method. Next, the equipment operating condition test on a flat road was done. The vibration characteristics of the whole vehicle were obtained later. The results show that the cab vibration and the finite element results agree well, but the natural frequency of the cab is close to the vibration frequency of the human body. And this is not conducive to long-term operation of the drivers. In order to improve the human operational comfort, it is necessary to reduce its natural frequency during the cab structure design process. The research in this paper can provide help for the similar human-machine operation comfort study and product design

Theoretical analyses of roll- and pitch-coupled hydro-pneumatic strut suspensions

Vehicle suspension design and dynamics analysis play a key role in enhancement of automotive system performance. Despite extensive developments in actively-controlled suspensions, their commercial applications have been limited due to the associated high cost and weight. Alternative designs in either passive or semi-active suspensions are highly desirable to achieve competitive vehicle performance with relatively lower cost and greater reliability. This dissertation research proposes two hydro-pneumatic suspension strut designs, including a twin-gas-chamber strut, and systematically investigates various concepts in roll- and pitch-coupled suspensions employing hydraulic, pneumatic and hybrid fluidic interconnections between the wheel struts. The proposed strut designs, including single- and twin-gas-chamber struts, offer larger working area and thus lower operating pressure, and integrate damping valves. Nonlinear mathematical models of the strut forces due to various interconnected and unconnected suspension configurations are formulated incorporating fluid compressibility, floating piston dynamics, and variable symmetric and asymmetric damping valves, which clearly show the feedback damping effects of the interconnections between different wheel struts. The properties and dynamic responses of the proposed concepts in roll- and pitch-coupled suspension struts are evaluated in conjunction with in-plane and three-dimensional nonlinear vehicle models. The validity of the vehicle models is demonstrated by comparing their responses with the available measured data. The analyses of the proposed coupled suspensions are performed to derive their bounce-mode, anti-roll, anti-pitch and warp-mode properties, and vehicle dynamic responses to external excitations. These include road roughness, steering and braking, and crosswinds. The results suggest that the fluidically-coupled passive suspension could yield considerable benefits in enhancing vehicle ride and handing performance. Furthermore these offer superior design flexibility. The suspension struts offer a large number of coupling possibilities in the three-dimensions, some of which however would not be feasible, particularly for commercial vehicles where suspension loads may vary considerably. A generalized analytical model for a range of interconnected suspensions is thus developed, and a performance criterion is formulated to assess the feasibility of a particular interconnection in a highly efficient manner. The handling and directional responses of a three-dimensional vehicle model employing X-coupled hydro-pneumatic suspension are evaluated under split-o straight-line braking and braking-in-a-turn maneuvers. The results clearly show that the X-coupled suspension offers enhanced anti-roll and anti-pitch properties while retaining the soft vertical ride and warp properties. Fundamental pitch and vertical dynamics of a road vehicle are also considered to derive a set of essential design rules for suspension design and tuning for realizing desirable pitch performanc

An investigation into hybrid power trains for vehicles with regenerative braking

Imperial Users onl

Tyres / Tyre-Soil-Interaction

Die Neuheiten und Trends auf dem Reifenmarkt werden vorgestellt. Dabei ist die Entwicklung zu intelligenten Reifen mit Sensoren, Reifendruckempfehlungen und Druckregelanlagen zu beobachten.The innovations and trends on the tyre market are presented. The development of intelligent tires with sensors, tire pressure recommendations and pressure control systems can be observed

Enhancement of Ride and Directional Performances of Articulated Vehicles via Optimal Frame Steering and Hydro-Pneumatic Suspension

Off-road vehicles employed in agriculture, construction, forestry and mining sectors are known to exhibit comprehensive levels of terrain-induced ride vibration and relatively lower directional stability limits, especially for the articulated frame-steered vehicles (AFSV). The transmitted whole-body vibration (WBV) exposure levels to the human operators generally exceed the safety limits defined in ISO-2631-1 and the European Community guidelines. Moreover, the directional stability limits are generally assessed neglecting the contributions due to terrain roughness and kineto-dynamics of the articulated frame steering (AFS) system. Increasing demand for high load capacity and high-speed off-road vehicles raises greater concerns for both the directional stability limits and WBV exposure. The criterion for acceptable handling and stability limits of such vehicles do not yet exist and need to be established. Furthermore, both directional stability performance and ride vibration characteristics are coupled and pose conflicting vehicle suspension design requirements. This dissertation research focuses on enhancement of ride, and roll- and yaw-plane stability performance measures of frame-steered vehicle via analysis of kineto-dynamics of the AFS system and hydro-pneumatic suspensions. A roll stability performance measure is initially proposed for off-road vehicles considering magnitude and spectral contents of the terrain elevations. The roll dynamics of an off-road vehicle operating on random rough terrains were investigated, where the two terrain-track profiles were synthesized considering coherency between them. It is shown that a measure based on steady-turning root-mean-square lateral acceleration corresponding to the sustained period of unity lateral-load-transfer-ratio prior to the absolute-rollover, could serve as a reliable measure of roll stability of vehicles operating on random rough terrains. The simulation results revealed adverse effects of terrain elevation magnitude on the roll stability, while a relatively higher coherency resulted in lower terrain roll-excitation and thereby higher roll stability. The yaw-plane stability limits of an AFSV are investigated in terms of free yaw-oscillations as well as transient steering characteristics through field measurements and simulations of kineto-dynamics of the AFS system. It was shown that employing hydraulic fluid with higher bulk modulus and increasing the steering arm lengths would yield higher yaw stiffness of the AFS system and thereby higher frequency of yaw-oscillations. Greater leakage flows and viscous seal friction within the AFS system struts caused higher yaw damping coefficient but worsened the steering gain and articulation rate. A design guidance of the AFS system is subsequently proposed. The essential objective measures are further identified considering the AFSV’s yaw oscillation/stability and steering performances, so as to seek an optimal design of the AFS system. For enhancing the ride performance of AFSV, a simple and low cost design of a hydro-pneumatic suspension (HPS) is proposed. The nonlinear stiffness and damping properties of the HPS strut that permits entrapment of gas into the hydraulic oil were characterized experimentally and analytically. The formation of the gas-oil emulsion was studied in the laboratory, and variations in the bulk modulus and mass density of the emulsion were formulated as a function of the gas volume fraction. The model results obtained under different excitations in the 0.1 to 8 Hz frequency range showed reasonably good agreements with the measured stiffness and damping properties of the HPS strut. The results showed that increasing the fluid compressibility causes increase in effective stiffness but considerable reduction in the damping in a highly nonlinear manner. Increasing the gas volume fraction resulted in substantial hysteresis in the force-deflection and force-velocity characteristics of the strut. A three-dimensional AFSV model is subsequently formulated integrating the hydro-mechanical AFS system and a hydro-pneumatic suspension. The HPS is implemented only at the front axle, which supports the driver cabin in order to preserve the roll stability of the vehicle. The validity of the model is illustrated through field measurements on a prototype vehicle. The suspension parameters are selected through design sensitivity analyses and optimization, considering integrated ride vibration, and roll- and yaw-plane stability performance measures. The results suggested that implementation of HPS to the front unit alone could help preserve the directional stability limits compared to the unsuspended prototype vehicle and reduce the ride vibration exposure by nearly 30%. The results of sensitivity analyses revealed that the directional stability performance limits are only slightly affected by the HPS parameters. Further reduction in the ride vibration exposure was attained with the optimal design, irrespective of the payload variations

Development of Control Algorithm for Tractor Semi-Active Cabin Suspension based on Sliding Mode Control

학위논문(석사) -- 서울대학교대학원 : 농업생명과학대학 바이오시스템공학과, 2022.2. 박영준.트랙터는 불균일한 지면을 주행하며 부하변동이 큰 농작업에 주로 사용된다. 이로 인해 발생하는 트랙터의 승차진동은 작업자의 건강에 위협이 되고 있다. 때문에 트랙터 캐빈의 승차진동을 저감할 수 있는 여러 방안들이 제안되었으나, 아직도 국제적 기준량을 넘는 승차진동이 발생하고 있다. 승차진동을 효과적으로 저감하는 방안으로 캐빈 현가장치가 주목을 받고 있다. 캐빈 현가장치로 사용될 수 있는 수동(passive), 반능동(semi-active), 능동(active) 현가장치 중에서 동력 손실이 적으면서도 승차진동 저감 성능이 뛰어난 반능동 현가장치에 대한 연구들이 수행되어 왔다. 반능동 현가장치를 제어하기 위한 연구들은 승용차를 대상으로 주로 진행되었다. 스카이훅(skyhook), 최적제어, 퍼지 로직, 슬라이딩 모드 제어 등의 다양한 제어 기법을 통해 효과적으로 승용차의 승차진동을 저감한 연구 사례가 다수 수행되었다. 그러나 현가상 질량이 현가하 질량보다 큰 승용차는 시스템 구조적으로 트랙터와 다르기 때문에, 트랙터 구조를 고려한 연구가 필요한 실정이다. 반능동 현가장치가 장착된 트랙터를 대상으로 한 연구는 최적제어 기법을 이용한 연구에 머물러 있다. 그러나 최적제어 기법은 트랙터의 복잡한 시스템을 정확하게 구현하지 못함으로 인해 발생할 수 있는 시스템 모델의 불확실성과 작업 환경이 외란에 노출되기 쉬운 환경이라는 점 때문에 제어 성능이 저하될 수 있다. 따라서 본 연구에서는 트랙터 구조를 고려한 1/2(half-car) 트랙터 동역학 모델을 개발하고 반능동 현가장치의 특성과 비례제어밸브 전류의 동특성을 구현하여 모델의 정확도를 높였다. 개발된 동역학 모델을 대상으로 강인 제어 기법인 슬라이딩 모드 제어를 이용하여 반능동 현가장치 제어 알고리즘을 개발하고 시뮬레이션 결과를 비교하여 제어 알고리즘의 성능을 평가하였다. 시뮬레이션 결과에 따르면 고무마운트를 장착한 트랙터에서 발생하는 캐빈 수직 가속도보다 반능동 현가장치를 장착한 트랙터에서 발생하는 캐빈 수직 가속도가 입력 노면 조건이 계단 입력인 경우 55% 감소하였고, ISO8608 노면 등급인 경우 41% 감소하는 것을 확인하였다. 개발된 제어 알고리즘의 실시간성을 검증하기 위하여 제어기를 대상으로 Hardware-in-the-Loop 시뮬레이션을 진행하였고 노면 조건과 상관없이 캐빈 수직 가속도에서 큰 변화가 나타나지 않아 실시간성을 만족하는 것을 확인할 수 있었다.Tractors travel on uneven ground and are mainly used for agricultural work with large load fluctuations. The resulting ride vibration of the tractor poses a threat to the health of the worker. Therefore, several studies have been done to reduce the ride vibration of the tractor cabin, but there are still ride vibrations that exceed the international standard. Cabin suspension is drawing attention as a way to effectively reduce ride vibrations. Among passive, semi-active, and active suspensions that can be used as cabin suspension, studies have been conducted on semi-active suspension because of its low power loss and excellent ride vibration reduction performance. Studies to control semi-active suspension were mainly conducted on passenger cars. There are many research cases that effectively reduce ride vibration of passenger car through various control techniques such as skyhook, optimal control, fuzzy logic, and sliding mode control. However, since tractor is systematically different from passenger car of which sprung mass is greater than the unsprung mass, research considering the tractor structure is needed. Research on tractors equipped with semi-active suspension remains in research using optimal control techniques. However, the optimal control technique may deteriorate control performance due to the uncertainty of the system parameter that may arise from the failure to accurately measure the complex system of the tractor and the fact that the working environment which is easily exposed to disturbance. Therefore, in this study, a half-car tractor dynamic model considering a tractor structure was developed, and the accuracy of the model was improved by reflecting the dynamic characteristics of the semi-active suspension and the proportional control valve current. And a semi-active suspension control algorithm was developed and applied to the dynamic model, using sliding mode control which is one of the robust control technique. The performance of the control algorithm was evaluated by comparing the simulation results. According to the simulation results, it was confirmed that the vertical acceleration of the cabin in the tractor equipped with the semi-active suspension decreased by 55% when the input road condition was a step input and decreased by 41% when the ISO8608 road level. And Hardware-in-the-Loop simulation was conducted on controllers to verify the real-time property of the developed control algorithm.1. 서 론 1 2. 연구 목적 5 3. 문헌 연구 6 3.1. 트랙터 동역학 모델 6 3.2. 반능동 현가장치 제어 알고리즘 7 4. 1/2 트랙터 동역학 모델 개발 10 4.1. 트랙터 제원 11 4.2. 고무마운트 트랙터 동역학 모델 개발 12 4.3. 현가장치 트랙터 동역학 모델 개발 21 4.3.1. 현가장치 1/2 트랙터 동역학 모델 21 4.3.2. 수동 및 반능동 현가장치 특성 30 4.3.3. 비례제어밸브 모델 33 4.3.4. 현가장치 트랙터 동역학 모델 검증 36 5. 반능동 현가장치 제어 알고리즘 개발 42 5.1. 비례제어밸브 전류 추종 알고리즘 42 5.1.1. PI 제어기 설계 42 5.1.2. 외란관측기 설계 43 5.1.3. 외란관측기 강인성 평가 46 5.2. 슬라이딩 모드 제어 기반 반능동 현가장치 제어 알고리즘 48 6. 트랙터 제어 모델 및 시뮬레이션 54 6.1. 트랙터 제어 모델 54 6.2. Model-in-the-Loop 시뮬레이션 58 6.2.1. 주파수 영역 분석 58 6.2.2. 시간 영역 분석 60 6.3. Hardware-in-the-Loop 시뮬레이션 69 6.3.1. Hardware-in-the-Loop 시뮬레이션 시스템 구축 69 6.3.2. Hardware-in-the-Loop 시뮬레이션 결과 72 7. 결론 77 8. 참고 문헌 79 9. 부록 85석