A clipped-optimal control algorithm for semi-active vehicle suspensions: Theory and experimental evaluation

This paper addresses the problem of optimal control for semi-active vehicle suspensions. A specific goal is to develop an algorithm which is capable of optimising ride and handling behaviour simultaneously in an experimental situation. A time-domain optimal control approach is adopted in which ride and handling are modelled as exogenous disturbances acting on the vehicle: road disturbances (modelled stochastically), and driver inputs (treated as deterministic quasi-static disturbances). A control algorithm is derived from a solution of the stochastic Hamilton–Jacobi–Bellman equation for the finite horizon case. The advantages of the approach are demonstrated experimentally on a test vehicle performing a steering manoeuvre on a bumpy roundabout.This work was supported in part by J.S. Latsis Foundation, Greece, EPSRC industrial case studentship (07002200) and EPSRC programme grant EP/G066477/1.This paper was originally published in Automatica (P Brezas, MC Smith, W Hoult, Automatica 2015, 53, 188-194

Improving driver comfort in commercial vehicles : modeling and control of a low-power active cabin suspension system

Comfort enhancement of commercial vehicles has been an engineering topic ever since the first trucks emerged around 1900. Since then, significant improvements have been made by implementing cabin (secondary) and seat suspensions. Moreover, the invention of the air spring and its application to the various vehicle's suspension systems also greatly enhanced driver comfort. However, despite these improvements many truck drivers have health related Problems, which are expected to be caused by their exposure to the environmental vibrations over longer periods of time. The most recent suspension improvements in commercial vehicles date back more than a decade and the possibilities for further improvements using passive devices (springs and dampers) seem nearly exhausted. Consequently, in line with developments in passenger cars, truck manufacturers are now investigating semi-active and active suspension systems. Herein, active suspensions are expected to give the best performance, but also come at the highest cost. Especially the high power consumption of market-ready devices is problematic in a branch where all costs need to be minimized. In this dissertation the field of secondary suspension design and controllable suspensions for heavy vehicles is addressed. More specifically, the possibilities for a low power active cabin suspension design are investigated. The open literature on this topic is very limited in comparison to that of passenger cars. However, as heavy vehicle systems are dynamically more challenging, with many vibration modes below 20 Hz, there is great research potential. The dynamic complexity becomes clear when considering the developed 44 degrees of freedom (DOF) tractor semi-trailer simulation model. This model is a vital tool for suspension analysis and evaluation of various control strategies. Moreover, as it is modular it can also be easily adapted for other related research. The main vehicle components all have their own modules. So, for example, when evaluating a new cabin suspension design, only the cabin module needs to be replaced. The model has been validated using extensive tests on a real tractor semi-trailer test-rig. The control strategy is a key aspect of any active suspension system. However, the 44 DOF tractor semi-trailer model is too complex for controller design. Therefore, reduced order models are required which describe the main dynamic properties. A quarter truck heave-, half truck roll-, and half truck pitch-heave model are developed and validated using a frequency-domain validation technique and the test-rig measurements. The technique is based on a recently developed frequency domain validation method for robust control and adapted for non-synchronous inputs, with noise on the input and output measurements. The models are shown to give a fair representation of the complex truck dynamics. Furthermore, the proposed validation method may be a valuable tool to obtain high quality vehicle models. As a first step, in search of a low power active cabin suspension system, various suspension concepts are evaluated under idealized conditions. From this evaluation, it follows that the variable geometry active suspension has great potential. However, the only known physical realization - the Delft Active Suspension - suffers from packaging issues, nonlinear stiffness characteristics, fail-safe issues and high production cost. Recently, a redesign - the electromechanical Low-Power Active Suspension (eLPAS) - was presented, which is expected to overcome most of these issues. This design is modeled, analyzed and a controller is designed, which can be used to manipulate the suspension force. Feasibility of the design is demonstrated using tests on a hardware prototype. Finally, the validated reduced order models are used to design suitable roll and pitch-heave control strategies. These are evaluated using a combination of the 44 DOF tractor semi-trailer and eLPAS models. Four eLPAS devices are placed at the lower corners of the cabin and modal input-output decoupling is applied for the controller implementation. It is shown, that driver comfort and cabin attitude behavior (roll, pitch and heave when braking, accelerating or steering) can be greatly improved without consuming excessive amounts of energy. So, overall these results enforce the notion that the variable geometry active suspension can be effectively used as low power active cabin suspension. However, there are still some open questions that need to be addressed before this design can be implemented in the next generation commercial vehicles. Durability and failsafe behavior of the eLPAS system, as well as controller robustness to variations in the vehicle parameters and environmental conditions, are some of the topics that require further study

Optimal design of a quadratic parameter varying vehicle suspension system using contrast-based Fruit Fly Optimisation

In the UK, in 2014 almost fifty thousand motorists made claims about vehicle damages caused by potholes. Pothole damage mitigation has become so important that a number of car manufacturers have officially designated it as one of their priorities. The objective is to improve suspension shock performance without degrading road holding and ride comfort. In this study, it is shown that significant improvement in performance is achieved if a clipped quadratic parameter varying suspension is employed. Optimal design of the proposed system is challenging because of the multiple local minima causing global optimisation algorithms to get trapped at local minima, located far from the optimum solution. To this end an enhanced Fruit Fly Optimisation Algorithm − based on a recent study on how well a fruit fly’s tiny brain finds food − was developed. The new algorithm is first evaluated using standard and nonstandard benchmark tests and then applied to the computationally expensive suspension design problem. The proposed algorithm is simple to use, robust and well suited for the solution of highly nonlinear problems. For the suspension design problem new insight is gained, leading to optimum damping profiles as a function of excitation level and rattle space velocity

RAS/MAPK activation is associated with reduced Tumor-infiltrating lymphocytes in Triple-Negative Breast Cancer: Therapeutic Cooperation Between MEK and PD-1/PD-L1 Immune Checkpoint Inhibitors

PURPOSE: Tumor-infiltrating lymphocytes (TIL) in the residual disease (RD) of triple-negative breast cancers (TNBC) after neoadjuvant chemotherapy (NAC) are associated with improved survival, but insight into tumor cell-autonomous molecular pathways affecting these features are lacking. EXPERIMENTAL DESIGN: We analyzed TILs in the RD of clinically and molecularly characterized TNBCs after NAC and explored therapeutic strategies targeting combinations of MEK inhibitors with PD-1/PD-L1-targeted immunotherapy in mouse models of breast cancer. RESULTS: Presence of TILs in the RD was significantly associated with improved prognosis. Genetic or transcriptomic alterations in Ras-MAPK signaling were significantly correlated with lower TILs. MEK inhibition upregulated cell surface MHC expression and PD-L1 in TNBC cells both in vivo and in vitro. Moreover, combined MEK and PD-L1/PD-1 inhibition enhanced antitumor immune responses in mouse models of breast cancer. CONCLUSIONS: These data suggest the possibility that Ras-MAPK pathway activation promotes immune-evasion in TNBC, and support clinical trials combining MEK- and PD-L1-targeted therapies. Furthermore, Ras/MAPK activation and MHC expression may be predictive biomarkers of response to immune checkpoint inhibitors

Mathematical Model Studies on the Optimal Scheduling of the Treatment of Systemic Malignant Disease by Radiation

The work reported in this thesis deals with mathematical model studies on the optimal scheduling of treatment of systemic malignant disease by radiation. To provide the necessary background to the original aspects of the work reviews of several fields are required. Chapter 1 is a general review of normal tissue radiobiology. Chapter 2 is a review of human tumour radiobiology. Chapter 3 focusses on one particular isoeffect model, the linear-quadratic or LQ model, which is employed throughout this thesis to describe the effects of radiation on normal tissues. These basic radiobiological principles are applied to the clinical modalities of total body irradiation (TBI) and biologically targeted radiotherapy (BTR). Chapter 4 reviews the principles of TBI. Chapter 5 is a review of published data on the in-vitro radiosensitivities of human leukaemia/lymphoma and neuroblastoma, two conditions which require a systemic approach to treatment. Chapter 8 is a review of the principles of BTR. The original work is contained in the appendix to chapter 3, which examines the correspondence between the LQ model and CRE models for continuous radiation exposures with constant and exponentially decaying dose-rates; chapter 6, Which examines the question of whether fractionated or low dose-rate TBI is the superior method of treatment; chapter 7, where the optimal scheduling of fractionated TBI is investigated; chapter 9, where the LQ isoeffect model and a dosimetric approach is used for the evaluation of alternative therapeutic strategies for the treatment of widespread micrornetastatic disease by BTR. Finally, in chapter 10 a simple model is used to investigate optimal scheduling of BTR, TBI and marrow rescue. CONCLUSIONS 1/ Comparison of the LQ model and the CRE model for continuous radiation exposures: for constant dose-rates it is found that, when late-effect parameter values are used in the LQ model, there is a correspondence between the models' predictions. There is no correspondence between models when acute-effect parameter values are used in the LQ model. In the case of exponentially decaying dose-rates the predictions of the CRE and LQ models appear more divergent, although again the use of late rather than acute-effect parameter values in the LQ model gives a closer match to the CRE. 2/ Fractionated TBI is predicted to be preferable to low dose-rate TBI treatment. Although theoretically the methods can be equivalent, low dose-rate treatments would have to be over impractically long treatment times. 3/ In the case of external beam TBI, fractionated low dose-rate treatments do not appear to offer a significant improvement over fractionated high dose-rate treatments. This is because in order to achieve a significant increase in dose or reduction in toxicity impractically long exposure times are required. It is expected that this finding will be true in general for external beam radiotherapy, not just in the case of TBI. 4/ Optimal fractionation schedules for the treatment of leukaemia/lymphoma and neuroblastoma by TBI are predicted to be accelerated and hyperfractionated. It is suggested that a two fraction per day schedule of 10 fractions of 1.3-1.5 Gy is a suitable candidate for clinical evaluation. 5/ It is concluded that knowledge of ratios for tumours and normal tissues is, by itself, insufficient information to enable prediction of optimal schedules. 6/ In the case of BTR, dose-rate effects are predicted to be important for late-responding tissues. Tolerance doses may be greater or less than those for fractionated radiotherapy depending on the effective radionuclide half-life. 7/ When injected activities of targeted radionuclide are restricted by haemopoietic tolerance, curative therapy is unlikely. 131-I appears to be a better radionuclide warhead for therapy of micrometastases than 90-Y. 8/ The use of bone marrow rescue in conjunction with BTR seems to offer curative potential, however reasons are presented why a combined strategy using BTR, TBI and marrow rescue is likely to be preferable. 9/ For optimal scheduling of BTR, TBI and marrow rescue, the main characteristics of BTR which determine curative potential are its specificity and sensitivity. Specificity is defined here as the ratio of initial dose-rate at the tumour cells to that in the dose-limiting tissue. Sensitivity is inversely related to the proportion of tumour cells which escape targeting. Where biological targeting is highly specific but some tumour cells escape, a phenomenon of "overkill" will largely determine the optimal schedules. It is predicted that these are likely to consist of combinations of BTR and external beam TBI with the TBI component being the greatest in terms of radiation dose to the whole body

The power of protection: a population-based comparison of native and non-native youth suicide attempters

This study provides actionable information about intervening with American Indian/Alaska Native (AI/AN) youth to prevent suicide. Statewide school survey data were used to model the impact of risk and protective factors on self-reported suicide attempts (both AI/AN and non-AI/AN). The cumulative risk and protective model worked similarly for both groups. AI/AN youth had a higher threshold of risk before making a suicide attempt. Protective factors buffered the impact of risk, particularly for the higher risk youth

IN-WHEEL COUPLED SUSPENISON AND DRIVE SYSTEM FOR ATTITUDE CONTROL AND VEHICLE PROPULSION

The automotive marketplace is a volatile and dynamic system driven by consumer desires, marketing, fuel prices, technology, and legislation. Recently many of these factors have culminated in a common effort to encourage hybrid and electric vehicle development. The technology for electric vehicles has finally found enough maturity to be implemented into consumer based vehicles from hybrid SUVs to high performance sports cars. This expansion in available propulsion systems and vehicle architectures has spurred research and development into new and novel approaches for propulsion as well as systems to provide increased ride comfort. This work presents a dual electric motor drive system that incorporates a mechanism that allows not only longitudinal actuation of the vehicle, but also low frequency vertical actuation of the vehicle. The system is able to achieve this by coupling two motors per wheel and combining them with a new kinematic mechanism that facilitates dual degree of freedom actuation with coupled motors. By utilizing two motors coupled together to actuate the two degrees of freedom, more efficient utilization of resources is possible. Rather than having a motor that provides longitudinal motion and another that provides vertical actuation, the system uses two motors coupled together to provide both. When one degree of freedom doesn\u27t require actuation, the motors can be utilized to provide higher performance in the other degree of freedom. This system is designed, modeled, and actually converted into a prototype design throughout the entirety of this work. Initial conceptual modeling and performance metric definition occurs in a kinematic analysis of a basic mechanism. This is then developed into a more complex three dimensional model, and finally converted into physical hardware. In parallel to the hardware development, the controller that allows the system to operate is also explored. From actuating a single degree of freedom to a linearized coupling algorithm that allows both degrees of freedom to be controlled independently and simultaneously, the control system evolves into a functioning system

Addressing Public Health Risks of Persistent Pollutants Through Nutritional Modulation and Biomimetic Nanocomposite Remediation Platforms

Due to their relative chemical stability and ubiquity in the environment, chlorinated organic contaminants such as polychlorinated biphenyls (PCBs) pose significant health risks and enduring remediation challenges. Engineered nanoparticles (NPs) provide a novel platform for sensing/remediation of these toxicants, in addition to the growing use of NPs in many industrial and biomedical applications, but there remains concern for their potential long-term health effects. Research highlighted herein also represents a transdisciplinary approach to address human health challenges associated with exposure to PCBs and NPs. The objectives of this dissertation research are two-fold, 1) to develop effective methods for capture/sensing and remediation of environmental toxicants, and 2) to better understand associated risks and to elucidate relevant protective mechanisms, such as lifestyle-related modulators of environmental disease. Prevalent engineered nanoparticles, including aluminum oxide and titanium dioxide, have been studied to better understand effective nanoparticle dispersion methods for in vitro nanotoxicology studies. This work has served both to effectively stabilize these nanoparticles under physiological conditions and to better understand the associated mechanisms of toxicity, which links these metal nanoparticles to endothelial oxidative stress and inflammation through phosphorylation of key cellular signaling molecules and increased DNA binding of pro-inflammatory NFκB. Surface functionalization, though, is being found to limit potential toxicity and has been utilized in subsequent research. A novel polyphenol-functionalized, NP-based system has been developed which combines the biomimetic binding capabilities of nutrient polyphenols with the separation and heating capabilities of superparamagnetic iron oxide NPs for the capture/sensing of organic contaminants in polluted water sources. Magnetic nanocomposite microparticles (MNMs) incorporating the fluorescent polyphenols quercetin and curcumin exhibit high affinity for model organic pollutants followed by rapid magnetic separation, addressing the need for sustainable pollutant remediation. Further work has been performed to both better understand health concerns associated with environmental toxicants such as PCBs and to determine effective methods for modulating their toxicity. This research has shown that PCB remediation through dechlorination is a viable technique for decreasing endothelial inflammation, although complete dechlorination to biphenyl is necessary to effectively eliminate superoxide production, NFκB activation, and induction of inflammatory markers. Additionally, the nutrient polyphenol EGCG, found in green tea, has been shown to serve as a biomedical modulator of in vivo PCB toxicity by up-regulating a battery of antioxidant enzymes transcriptionally controlled by AhR and Nrf2 proteins