Skyhook surface sliding mode control on semi-active vehicle suspension systems for ride comfort enhancement

A skyhook surface sliding mode control method was proposed and applied to the control on the semi-active vehicle suspension system for its ride comfort enhancement. A two degree of freedom dynamic model of a vehicle semi-active suspension system was given, which focused on the passenger’s ride comfort perform-ance. A simulation with the given initial conditions has been devised in MATLAB/SIMULINK. The simula-tion results were showing that there was an enhanced level of ride comfort for the vehicle semi-active sus-pension system with the skyhook surface sliding mode controller

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

Regenerative Suspension System Modeling and Control

Many energy indicators show an increase in the world’s energy deficit. Demand for portable energy sources is growing and has increased the market for energy harvesters and regenerative systems. This work investigated the implementation of a regenerative suspension in a two-degree-of freedom (2-DOF) quarter-car suspension system. First, an active controller was designed and implemented. It showed 69% improvement in rider comfort and consumed 8 – 9 W of power to run the linear motor used in the experiment. A regenerative suspension system was then designed to save the energy normally spent in active suspensions, approximately several kilowatts in an actual car. Regenerative suspension is preferable because it can regenerate energy. Experimental investigations were then conducted to find generator constants and damping coefficients. Additionally, generator damping effects and power regeneration in the quarter-car test bed were also investigated. The experiments showed that a linear regenerative damper can suppress up to 22% of vibrations and harvest 2% of the disturbance power. Since both harvesting and damping capabilities were noticeable in this test bed, it was used to implement regenerative suspension, and a regenerative controller was developed to provide riders with additional comfort. To implement this regenerative controller, an electronic interface was designed to facilitate controlling the regenerative force and storing energy after the rectification process. The electronic interface used was a symmetrical-bridgeless boost converter (SBBC) due to its few components and even fewer control efforts. The converter was then modeled in a manner that made the current and voltage in phase for the maximum power factor. The converter control allowed the motor’s external load to be presented as of variable resistance with the unity power factor. The generator was then considered a voltage source for energy regeneration purposes. The controller was designed to control regenerative force at a frequency of 20 kHz. This frequency was sufficient to enable another controller to manipulate the desired regenerative damping force, which was chosen to be 1 kHz. The input to this controller was the generator voltage used to determine the polarity of pulse-width modulation (PWM). Therefore, a combination of converter and controller was able to take the place of an active controller. A different controller was then designed to manipulate the desired damping force. This regenerative controller was designed in a manner similar to that of a semi-active controller. It improved vibration suppression and enhanced harvesting capabilities. The regenerative suspension showed better results than a passive suspension. The improvements are minimal at this time, but there is the potential for greater improvement with a more efficient controller. The harvested energy was so small in this experiment because the damper was inefficient. In practice, the damper’s efficiency should be improved. A regenerative damper will be more economical than a passive damper, and suppress more vibration at the same time. The active suspension system showed superior performance. Conversely, the regenerative system showed only modest performance but also regenerated energy. However, a regenerative suspension can be combined with an active suspension to enhance the rider’s comfort and provide energy regeneration

Modelling and control of semi active suspension system incorporating magnetorheological damper for generic vehicle

This study presents the simulation and experimental works for Magnetorheological (MR) semi active suspension system in generic vehicles. In simulation study, a seven degree of freedom (7-DOF) vehicle model was developed using MATLAB-Simulink and verified using TruckSim. A semi active controller with road friendliness oriented was developed to reduce vehicle tire force; besides, ride comfort becomes the secondary objective of the proposed controller. The proposed semi active controllers which are Tire Force Control (TFC), Aided Tire Force Control (ATFC) and ground Semi Active Damping Force Estimator (gSADE) and simulation results were compared with existing controller known as Groundhook (GRD) and passive suspension system. Then, these controllers were applied experimentally using generic quarter vehicle model. The overall results showed gSADE is the most effective controller in reducing vehicle tire force and improving ride comfort. Both reduction of gSADE vehicle tire force and ride comfort compared with passive system are similar about 14.2%. In the simulation study, ideal and real cases (using MR damper model) were conducted. In the ideal case, two bump profiles were used to test the effectiveness of the controller and the results showed gSADE recorded the highest improvement of the tire force followed by ATFC, TFC, GRD and passive system. The maximum improvement of gSADE control compared with passive system is about 21% in reduction of tire force and 22% in improving ride comfort. A similar test was conducted using MR damper model, and the overall result showed gSADE recorded almost similar improvement of the tire force compared with TFC. The maximum reduction of vehicle tire force and improvement of ride comfort using gSADE control compared with passive are 15% and 30%, respectively

Advanced Sensing and Control for Connected and Automated Vehicles

Connected and automated vehicles (CAVs) are a transformative technology that is expected to change and improve the safety and efficiency of mobility. As the main functional components of CAVs, advanced sensing technologies and control algorithms, which gather environmental information, process data, and control vehicle motion, are of great importance. The development of novel sensing technologies for CAVs has become a hotspot in recent years. Thanks to improved sensing technologies, CAVs are able to interpret sensory information to further detect obstacles, localize their positions, navigate themselves, and interact with other surrounding vehicles in the dynamic environment. Furthermore, leveraging computer vision and other sensing methods, in-cabin humans’ body activities, facial emotions, and even mental states can also be recognized. Therefore, the aim of this Special Issue has been to gather contributions that illustrate the interest in the sensing and control of CAVs

Fully pneumatic semi-active vibration isolator design and analysis

The research presented in this thesis provides a methodology of designing, modeling and controlling a fully pneumatic semi-active vibration isolator system. The prototype vibration isolator system has the ability to adjust the damping and natural frequency characteristics of the system. It consists of an air spring, a variable orifice valve, and an accumulator. In this conguration, the spring characteristics are provided by the air spring and accumulator, while the variable orifice valve provides the damping characteristics. The valve is computer regulated according to the innovative control laws that were developed for the pneumatic system. The vibration isolator system is designed to work in the vibration environment that is typically observed in the case of Class 7 and 8 vehicles as dened by the U.S Department of Transportation Federal Highway Administration. In order to design a vibration isolator system for the intended application, a benchmarking study was conducted to gain additional insight on OEM vibration isolator systems features and limitations. Based on the insights obtained from this study, the design requirements for the system were dened. This paper presents a methodology of producing a plant model that is based on supplier\u27s engineering specications and experimental characterization. The plant model includes a complete characterization of nonlinear pressure to volume and eective area to ride height relationships. A detailed design process of selecting and implementing components to optimize system performance is also provided. The plant model was then used to design three semiactive controllers that use position and pressure feedback signals that exploit the nonlinear characterizations to measure direct force generation. The semi-active controllers that were designed for this novel pneumatic vibration isolator system include: a LQI (Linear Quadratic Impulse) optimal controller, Modied Skyhook controller, and a Relative Displacement controller. This vibration isolator system was designed, fabricated, and tested using a prototype electronic height control system. A comprehensive design process for the specialized height control system is also presented.The performance of the system was evaluated using a custom testing apparatus that was built specically for this vibration isolator research. The testing apparatus was designed to accommodate dierent isolator systems and excite them with simulated road disturbances to obtain head-to-head system comparisons. This research presents a comparison between the system performances of an OEM Peterbilt cab suspension unit and the innovative fully pneumatic semi-active vibration isolator prototype using the three dierent control laws. It was found that the properly tuned controllers were able to provide desired dynamic characteristics over the range of common ride frequencies

Hybrid fuzzy sliding mode control for motorised space tether spin-up when coupled with axial and torsional oscillation

A specialised hybrid controller is applied to the control of a motorised space tether spin-up space coupled with an axial and a torsional oscillation phenomenon. A seven-degree-of-freedom (7-DOF) dynamic model of a motorised momentum exchange tether is used as the basis for interplanetary payload exchange in the context of control. The tether comprises a symmetrical double payload configuration, with an outrigger counter inertia and massive central facility. It is shown that including axial and torsional elasticity permits an enhanced level of performance prediction accuracy and a useful departure from the usual rigid body representations, particularly for accurate payload positioning at strategic points. A simulation with given initial condition data has been devised in a connecting programme between control code written in MATLAB and dynamics simulation code constructed within MATHEMATICA. It is shown that there is an enhanced level of spin-up control for the 7-DOF motorised momentum exchange tether system using the specialised hybrid controller. hybrid controller

State of the art of control schemes for smart systems featuring magneto-rheological materials

This review presents various control strategies for application systems utilizing smart magneto-rheological fluid (MRF) and magneto-rheological elastomers (MRE). It is well known that both MRF and MRE are actively studied and applied to many practical systems such as vehicle dampers. The mandatory requirements for successful applications of MRF and MRE include several factors: advanced material properties, optimal mechanisms, suitable modeling, and appropriate control schemes. Among these requirements, the use of an appropriate control scheme is a crucial factor since it is the final action stage of the application systems to achieve the desired output responses. There are numerous different control strategies which have been applied to many different application systems of MRF and MRE, summarized in this review. In the literature review, advantages and disadvantages of each control scheme are discussed so that potential researchers can develop more effective strategies to achieve higher control performance of many application systems utilizing magneto-rheological materials

Enhanced active front steering control using sliding mode control under varying road surface condition

In vehicle lateral dynamic control, the handling quality or steering ability of the vehicle is determined by the yaw rate response performances. The uncertainty of tire cornering stiffness due to varying tire-road adhesion coefficient, u caused by road surfaces perturbation during cornering manoeuvre may influence the transient performances of yaw rate response. Therefore, in this research, the enhanced control law of robust yaw rate tracking controller using the Sliding Mode Control (SMC) algorithm is proposed for active front steering (AFS) control strategy to improve the yaw rate response as desired. The vehicle lateral dynamics behaviors are described using the linear and nonlinear vehicle models. The linear 2 degree-of-freedom (DOF) single track model is used for controller design while the nonlinear 7 DOF two-track model is used for simulation and controller evaluations. The sliding surface of SMC is design based on yaw rate tracking error information. The control law equation is enhanced by integrating the uncertainty of cornering stiffness at the front wheels and to ensure the controller stability, the Lyapunov stability theory is applied. The transient performances and performance indices of AFS control responses are evaluated using the step steer and single lane change cornering manoeuvres test for varying values of u at dry, wet and snow or icy road surfaces. The simulations results demonstrated that the proposed enhanced control law using SMC is able to track the reference yaw rate with similar transient response performances. The proposed enhanced control law also provided low performance indices of ITAE and IAE compared to the conventional control law using SMC and robust CNF control for lower value of u at wet and snow or icy road surface. In terms of percentage of differential performance indices, the proposed control law has a better tracking ability of up to 58.45% compared to two other control laws. Therefore, this research concluded that the proposed enhanced control law using SMC has overcome the cornering stiffness uncertainty in AFS control strategy for different road surfaces during cornering manoeuvre and this enhancement is expected as a knowledge contribution to vehicle lateral dynamic study