Advanced hydraulic systems for next generation of skid steer loaders

Fluid power systems have been extensively used in off highway applications like skid steer loaders, wheel loaders, excavators since many years. Work has been done by both industry and academia to improve efficiency, reduce noise and leakages in these systems. With increasing competition in the market, importance is now also given to operator comfort and machine productivity in off highway applications. Mobile, off – highway vehicles like Skid-steer loaders are widely used in labour saving applications like loading earth into a truck, dig and move material on construction sites to, clean roads, clear snow from roads etc. To carry out these jobs in limited spaces, skid steer loaders need tight turning radius. For this reason, these machines have a short wheelbase which prevents the use of suspensions in these vehicles. The absence of a suspension system exposes the vehicle to ground vibrations of high magnitude and low frequency. Vibrations reduce operator comfort, productivity and life of components. This thesis will discuss control strategies for vibration damping of skid steer loader using the hydraulic boom cylinder as the active suspension element, which is equivalent to a spring–damper. Along with vibrations, the machine productivity is also hampered by material spillage which is caused by the tilting of the bucket due to the extension of the boom. This dissertation will discuss the development of a robust path-planning control algorithm which adapts to the position of the boom to maintain a level load to achieve bucket self-leveling. Another reason for reduced productivity in skid steer loaders is slow in site travel speeds. This dissertation also concentrates on reducing the in-job cycle time by developing a control strategy to smooth speed shift the drive motors keeping the pump flow constant. To synthesize these proposed control algorithms, high fidelity hydraulic and mechanical models of the skid steer loader are created. Ultimately, the control algorithms derived in this dissertation help in improving operator comfort and machine productivity

FORCE PLATE RELIABILITY AND DYNAMICS FOR AMBULANCE VIBRATION SUPPRESSION

This Major Qualifying Project used experimental methods and mathematical analysis tools to determine the dynamic characteristics of a force plate design as a solution to attenuate harmful road-induced vibrations experienced in the patient-care compartment of an ambulance

VHDL-AMS modeling of an automotive vibration isolation seating system

This paper presents VHDL-AMS model of an automotive vibration isolation seating system with an active electromechanical actuator. Five control algorithms for the actuator are implemented and their efficiencies are investigated by subjecting the system to a number of stimuli, such as a single jolt or noisy harmonic excitations. Simulations were carried out using the SystemVision simulator and results are shown to compare the relative performance merits of the control methods

Development and Assessment of a Virtual Reality Forklift Simulator as a Research Tool to Study Whole-Body Vibration

Operators of forklifts and other heavy machinery are exposed to whole-body vibration as a result of their daily work routine. Lower-back pain and other health risks have been linked to whole-body vibration exposure. A virtual reality simulator has been developed as a tool to study the effects of whole-body vibration and other risk factors associated with forklift operation. This study aims to demonstrate that the vibration exposure during simulation can be adjusted, and to compare the chassis accelerations to those of a real forklift. A sensitivity analysis examined three key parameters to determine their effect on the vibration properties of the simulator chassis. A comparison of field chassis accelerations during a standard work task revealed that the simulator better replicated accelerations for events involving transient surface irregularities, but the simulator had smaller vibrations when traveling across the relatively smooth warehouse floor. The simulator in its current state is a functional tool for evaluating the ergonomics of forklifts; however, further adjustment is required before the system can be considered a viable platform for whole-body vibration research

Ambulance Reliability Problems and Potential Technological Advancements to Solve Them

The goal of this IQP project was to discover flaws within the current ambulance design and outline solutions to fix them. The IQP team conducted interviews, polling, and participated in data collection. Through these methods it was discovered that the main problems in ambulance design are associated with the lack of dampening of road surface induced vibrations transmitted into the patient compartment. These vibrations decrease the ability of paramedics to perform the tests and treatments needed while simultaneously increasing the stress experienced by patients. The IQP focuses on technological advancements and design alternatives which may be implemented to decrease the road induced vibrations and increase ambulance efficiency

Ambulance Vibration Suppression via Force Field Domain Control

This PhD dissertation experimentally characterized the vibration amplitude, frequency, and energy associated with ambulance travel and defined the relationship of the vibration to safety, comfort and care of ambulance patients. Average vertical vibration amplitudes of .46 to 2.55 m/sec2 were recorded in the patient compartment of four ambulances over four road surfaces at three speed settings. Power spectrum analysis of the data revealed that the vibration energy and resulting vertical acceleration forces were concentrated in the .1 to 6 Hz range. Relationships between the measured ambulance vibration and the impact of whole body vibration on human physiology and performance were quantified. It was found that the accelerations measured in the ambulances were in excess of what is considered to be a normal human comfort level. Furthermore, the vibration measured was in a spectrum which could present physical impediments to optimum task performance for the on-board medical team. Phase portrait analysis combined with the power spectrum data revealed the presence of nonlinearities, stochastic fluctuations and time delays inherent in the data. The ambulance vibration data was then used to create a unique analytical model and library of forcing functions corresponding to the vehicles, road surfaces and vehicle speeds that were tested. Using the example of a vibration absorbing force plate fit over an existing ambulance floor, it was demonstrated how the model and forcing functions could be used to develop a control law equation to select parameters for active control of vibration to produce sustainable regions of patient safety, comfort and care

Smart Traction Control Systems for Electric Vehicles Using Acoustic Road-type Estimation

The application of traction control systems (TCS) for electric vehicles (EV) has great potential due to easy implementation of torque control with direct-drive motors. However, the control system usually requires road-tire friction and slip-ratio values, which must be estimated. While it is not possible to obtain the first one directly, the estimation of latter value requires accurate measurements of chassis and wheel velocity. In addition, existing TCS structures are often designed without considering the robustness and energy efficiency of torque control. In this work, both problems are addressed with a smart TCS design having an integrated acoustic road-type estimation (ARTE) unit. This unit enables the road-type recognition and this information is used to retrieve the correct look-up table between friction coefficient and slip-ratio. The estimation of the friction coefficient helps the system to update the necessary input torque. The ARTE unit utilizes machine learning, mapping the acoustic feature inputs to road-type as output. In this study, three existing TCS for EVs are examined with and without the integrated ARTE unit. The results show significant performance improvement with ARTE, reducing the slip ratio by 75% while saving energy via reduction of applied torque and increasing the robustness of the TCS.Comment: Accepted to be published by IEEE Trans. on Intelligent Vehicles, 22 Jan 201

Defensive Surface Roadway Vibration Dampening Inertia Wave

The goal of this project is to investigate the amplitude, energy, and frequency of vibrations in the typical ambulance and the effects of these vibrations on the quality, comfort, and efficiency of care. Working with current Emergency Medical Technicians, and studying past research work on vibrations and ambulance care, this project developed an overview of implications related to vibrations during transport. The team proposed a means to diminish the transfer of road vibrations into the ambulance

Series active variable geometry suspension application to comfort enhancement

This paper explores the potential of the Series Active Variable Geometry Suspension (SAVGS) for comfort and road holding enhancement. The SAVGS concept introduces significant nonlinearities associated with the rotation of the mechanical link that connects the chassis to the spring-damper unit. Although conventional linearization procedures implemented in multi-body software packages can deal with this configuration, they produce linear models of reduced applicability. To overcome this limitation, an alternative linearization approach based on energy conservation principles is proposed and successfully applied to one corner of the car, thus enabling the use of linear robust control techniques. An H∞ controller is synthesized for this simplified quarter-car linear model and tuned based on the singular value decomposition of the system's transfer matrix. The proposed control is thoroughly tested with one-corner and full-vehicle nonlinear multi-body models. In the SAVGS setup, the actuator appears in series with the passive spring-damper and therefore it would typically be categorized as a low bandwidth or slow active suspension. However, results presented in this paper for an SAVGS-retrofitted Grand Tourer show that this technology has the potential to also improve the high frequency suspension functions such as comfort and road holding