High-performance control of continuously variable transmissions

Nowadays, developments with respect to the pushbelt continuously variable transmission (CVT) are mainly directed towards a reduction of the fuel consumption of a vehicle. The fuel consumption of a vehicle is affected by the variator of the CVT, which transfers the torque and varies the transmission ratio. The variator consists of a metal V-belt, i.e., a pushbelt, which is clamped between two pulleys. Each pulley is connected to a hydraulic cylinder, which is pressurized by the hydraulic actuation system. The pressure in the hydraulic cylinder determines the clamping force on the pulley. The level of the clamping forces sets the torque capacity, whereas the ratio of the clamping forces determines the transmission ratio. When the level of the clamping forces is increased above the threshold for a given operating condition, the variator efficiency is decreased, whereas the torque capacity is increased. When the level of the clamping forces is decreased below the threshold for a given operating condition, the torque capacity is inadequate, which deteriorates the variator efficiency and damages the pulleys and the pushbelt. Since this threshold is not known, the level of the clamping forces is often raised for robustness, which reduces the variator efficiency. The challenge for the control system is to reduce the clamping forces towards the level for which the variator efficiency is maximized, although the variator efficiency is not measured. Furthermore, avoiding a failure of the variator in view of torque disturbances and tracking a transmission ratio reference are necessarily required. Two state-of-the-art control strategies are presently used, i.e., safety control and slip control. These control strategies involve limitations that follow from the model knowledge and/or the sensor use that underlies the control design. For this reason, the objectives of the research in this thesis are oriented towards improvements with respect to the model knowledge of both the hydraulic actuation system and the variator, which is subsequently exploited in the control design of both components, to improve the performance. The resources of the control designs are restricted to measurements from sensors that are standard. A cascade control configuration is proposed, where the inner loop controls the hydraulic actuation system and the outer loop controls the combination of the inner loop and the variator. The elements of the cascade control configuration are the subject of the research in this thesis. For the hydraulic actuation system, modeling via first principles and modeling via system identification are pursued. Modeling via first principles provides a nonlinear model, which is specifically suited for closed-loop simulation and optimization of design parameters. A modular approach is proposed, which reduces the model complexity, improves the model transparency, and facilitates the analysis of changes with respect to the configuration. The nonlinear model is validated by means of measurements from a commercial CVT. Modeling via system identification provides a model set, which is subsequently used for the hydraulic actuation system control design. A model set of high-quality is constructed, which is achieved by the design of the identification experiments that deals with the limited signal-to-noise ratio (SNR) that arises from actuators and sensors of low-quality. The hydraulic actuation system control design is multivariable, which is caused by the interaction between the hydraulic cylinders that is inherently introduced by the variator. Stability and performance are guaranteed for the range of operating conditions that is normally encountered, which is demonstrated with the experimental CVT. A variator control design is proposed that deals with both the transmission ratio and the variator efficiency in terms of performance variables, where the transmission ratio is measured, while the variator efficiency is not measured. The variator control design uses the standard measurement of the angular velocities, from which the transmission ratio is constructed, as well as the standard measurement of the pressure. Essentially, the variator control design exploits the observation that the maximum of the transmission ratio and the maximum of the variator efficiency are achieved for pressure values that nearly coincide. This observation is derived from both simulations with a nonlinear model and experiments with the experimental CVT. This motivates the use of the pressure-transmission ratio map, although the location of the maximum is not known. For this reason, the maximum of the input-output map is found by a so-called extremum seeking control (ESC) design, which aims to adapt the input in order to maximize the output. A robustness analysis shows that an input side disturbance that resembles a depression of the accelerator pedal and an output side disturbance that resembles the passage of a step bump are effectively handled. Finally, the ESC design is extended with a so-called tracking control (TC) design, which enables that optimizing the variator efficiency and tracking a transmission ratio reference are simultaneously achieved. The variator control design that is composed of the ESC design and the TC design is evaluated with the experimental CVT. Simulation of a driving cycle shows that the final variator control design outperforms the conventional variator control design in terms of the variator efficiency

Conception et évaluation expérimentale d'un actionneur linéaire entraîné par embrayages magnétorhéologiques(MR) pour suspension automobile active

Les fonctions principales d’une suspension automobile sont d’assurer le confort et la sécurité des passagers, tout en améliorant les performances dynamiques du véhicule. Toutefois, il n’est pas possible de rencontrer toutes ces fonctions à la fois, puisqu’ils demandent des paramètres d’ajustement de suspension opposés. Ce sont ces compromis de design, couplés aux profils irréguliers et non prévisibles des routes, qui induisent des mouvements et des vibrations indésirables dans l’habitacle. De plus, selon la norme ISO-2631, ces vibrations induites aux passagers peuvent causer des problèmes de santé, en plus d’être le principal facteur du mal des transports. Ces problèmes peuvent être résolus par un système de suspension active qui permettrait des corrections de l’assiette du véhicule et une atténuation des vibrations pour augmenter le confort, tout en maximisant la sécurité des passagers et les performances dynamiques du véhicule. Toutefois, les technologies actuelles d’actionneurs actifs pour des applications de suspension automobile ne sont pas encore adoptées commercialement à grande échelle compte tenu de leur grand coût et des lacunes au niveau de leurs performances. Ce mémoire présente une étude de faisabilité évaluant le potentiel des actionneurs à embrayages magnétorhéologiques (MR) glissants pour une application de suspension active pour les automobiles. D’abord, un état de l’art présentant les différentes technologies de suspension active actuelles ainsi que les propriétés intrinsèques des actionneurs MR est présenté. Ensuite, une application représentative est sélectionnée, soit un actionneur avant pour une berline de gamme moyenne (BMW 330ci 2001). Un modèle dynamique complet de la voiture, monté dans le logiciel Siemens Amesim et validé par des tests routiers sur un véhicule instrumenté, est utilisé pour définir des requis de design représentatifs. Un design d’actionneur linéaire possédant un moteur électrique à haute vitesse entraînant deux embrayages MR en rotation opposée est proposé. Ceux-ci permettent de générer les forces nécessaires au mouvement de la roue grâce à un système de doubles pignons et crémaillère supporté par un arbre cannelé à billes. L’actionneur est construit et testé expérimentalement. Les résultats démontrent que tous les requis de design sont atteints, et que l’actionneur peut générer des forces maximales de ±5300 N, une vitesse maximale de ±1.97 m/s et une bande passante de 92 Hz en utilisant un filtre de mise en forme sur la commande. En comparaison avec la jambe de suspension standard du véhicule, l’actionneur MR a une masse ajoutée de 14 kg, avec une masse non suspendue ajoutée de 3 kg. Lorsque comparée à d’autres technologies pertinentes de suspension active, l’approche MR présente simultanément une meilleure densité de force et une meilleure vitesse (bande passante), tout en ajoutant une masse suspendue minime. Les résultats expérimentaux de ce premier prototype non optimisé suggèrent que l’actionnement par glissement d’embrayages MR est prometteur pour les applications de suspensions actives dans le domaine de l’automobile

Component control for the Zero Inertia powertrain

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Integration of Active Systems for a Global Chassis Control Design

Vehicle chassis control active systems (braking, suspension, steering and driveline), from the first ABS/ESC control unit to the current advanced driver assistance systems (ADAS), are progressively revolutionizing the way of thinking and designing the vehicle, improving its interaction with the surrounding world (V2V and V2X) and have led to excellent results in terms of safety and performances (dynamic behavior and drivability). They are usually referred as intelligent vehicles due to a software/hardware architecture able to assist the driver for achieving specific safety margin and/or optimal vehicle dynamic behavior. Moreover, industrial and academic communities agree that these technologies will progress till the diffusion of the so called autonomous cars which are able to drive robustly in a wide range of traffic scenarios. Different autonomous vehicles are already available in Europe, Japan and United States and several solutions have been proposed for smart cities and/or small public area like university campus. In this context, the present research activity aims at improving safety, comfort and performances through the integration of global active chassis control: the purposes are to study, design and implement control strategies to support the driver for achieving one or more final target among safety, comfort and performance. Specifically, the vehicle subsystems that are involved in the present research for active systems development are the steering system, the propulsion system, the transmission and the braking system. The thesis is divided into three sections related to different applications of active systems that, starting from a robust theoretical design procedure, are strongly supported by objective experimental results obtained fromHardware In the Loop (HIL) test rigs and/or proving ground testing sessions. The first chapter is dedicated to one of the most discussed topic about autonomous driving due to its impact from the social point of view and in terms of human error mitigation when the driver is not prompt enough. In particular, it is here analyzed the automated steering control which is already implemented for automatic parking and that could represent also a key element for conventional passenger car in emergency situation where a braking intervention is not enough for avoiding an imminent collision. The activity is focused on different steering controllers design and their implementation for an autonomous vehicle; an obstacle collision avoidance adaptation is introduced for future implementations. Three different controllers, Proportional Derivative (PD), PD+Feedforward (FF) e PD+Integral Sliding Mode (ISM), are designed for tracking a reference trajectory that can be modified in real-time for obstacle avoidance purposes. Furthermore, PD+FF and PD+ISM logic are able to improve the tracking performances of automated steering during cornering maneuvers, relevant fromthe collision avoidance point of view. Path tracking control and its obstacle avoidance enhancement is also shown during experimental tests executed in a proving ground through its implementation for an autonomous vehicle demonstrator. Even if the activity is presented for an autonomous vehicle, the active control can be developed also for a conventional vehicle equipped with an Electronic Power Steering (EPS) or Steer-by-wire architectures. The second chapter describes a Torque Vectoring (TV) control strategy, applied to a Fully Electric Vehicle (FEV) with four independent electric motor (one for each wheel), that aims to optimize the lateral vehicle behavior by a proper electric motor torque regulation. A yaw rate controller is presented and designed in order to achieve a desired steady-state lateral behaviour of the car (handling task). Furthermore, a sideslip angle controller is also integrated to preserve vehicle stability during emergency situations (safety task). LQR, LQR+FF and ISM strategies are formulated and explained for yaw rate and concurrent yaw rate/sideslip angle control techniques also comparing their advantages and weakness points. The TV strategy is implemented and calibrated on a FEV demonstrator by executing experimental maneuvers (step steer, skid pad, lane change and sequence of step steers) thus proving the efficacy of the proposed controller and the safety contribution guaranteed by the sideslip control. The TV could be also applied for internal combustion engine driven vehicles by installing specific torque vectoring differentials, able to distribute the torque generated by the engine to each wheel independently. The TV strategy evaluated in the second chapter can be influenced by the presence of a transmission between themotor (or the engine) and wheels (where the torque control is supposed to be designed): in addition to the mechanical delay introduced by transmission components, the presence of gears backlashes can provoke undesired noises and vibrations in presence of torque sign inversion. The last chapter is thus related to a new method for noises and vibration attenuation for a Dual Clutch Transmission (DCT). This is achieved in a new way by integrating the powertrain control with the braking system control, which are historically and conventionally analyzed and designed separately. It is showed that a torsional preload effect can be obtained on transmission components by increasing the wheel torque and concurrently applying a braking wheel torque. For this reason, a pressure following controller is presented and validated through a Hardware In the Loop (HIL) test rig in order to track a reference value of braking torque thus ensuring the desired preload effect and noises reduction. Experimental results demonstrates the efficacy of the controller, also opening new scenario for global chassis control design. Finally, some general conclusions are drawn and possible future activities and recommendations are proposed for further investigations or improvements with respect to the results shown in the present work

Étude expérimentale de l’impact d’une suspension active à actionneurs magnétorhéologiques glissants sur le confort d’un véhicule automobile

Les fabricants automobiles sont continuellement à la recherche de moyens pour rendre leurs véhicules plus confortables et sécuritaires pour mieux satisfaire leur clientèle. Une suspension active est le moyen le plus efficace d’augmenter le confort d’une voiture tout en maintenant la sécurité de ses occupants. Les systèmes de suspension automobiles conventionnels sont munis d’un amortisseur et d’un ressort montés en parallèle entre chaque roue et la caisse de la voiture. Ils présentent un compromis fondamental entre le confort des usagers et la tenue de route d’un véhicule puisque leurs paramètres de conception (rigidité et amortissement) sont fixes et ne sont pas adaptés à toutes les conditions d’opération. Une suspension active inclut des actionneurs qui modulent la force de suspension pour procurer le comportement idéal au véhicule selon les conditions d’opération, ce qui permet à un véhicule d’atteindre des niveaux supérieurs de confort en conditions d’opérations normales tout en demeurant sécuritaire lors de manœuvres d’urgence. Depuis la fin des années 1980, plusieurs compagnies ont tenté d’implanter des technolo- gies de suspensions actives pour augmenter le confort de leurs véhicules. Des actionneurs hydrauliques, électromécaniques et pneumatiques ont été proposés. Par contre, ces tech- nologies n’ont pas connu un grand succès, ce qui s’explique entre autres par des coûts exorbitants, une masse trop élevée, un coût énergétique trop élevé ou un manque de per- formance du système. La technologie de suspension active à actionneurs à embrayages magnétorhéologiques glissants semble prometteuse sur tous ces plans. Cette technologie n’a toutefois pas encore été validée sur une suspension active de voiture. Cette thèse de doctorat porte sur l’étude de l’effet d’une suspension active à actionneurs à embrayages magnétorhéologiques glissants sur le confort d’un véhicule automobile. Quatre actionneurs à embrayages magnétorhéologiques sont d’abord conçus et validés expérimen- talement. Ils sont ensuite installés sur une voiture d’essais instrumentée (BMW 330Ci). Un contrôleur de suspension active par impédance variable est développé analytiquement avant d’être optimisé expérimentalement et comparé à la suspension d’origine du véhicule sur une route fermée. La suspension active améliore le confort de 67% à 65 km/h et de 61% à 80 km/h. De plus, lors d’essais sur bosses, la suspension active permet de réduire le mouvement de tête des occupants du véhicule d’un facteur 10 et améliore leur confort de 128%. Les données expérimentales de performance d’une voiture munie d’une suspension active complète, le contrôleur par impédance robuste et intuitif à calibrer ainsi que l’analyse détaillée de l’effet d’une suspension active sur le confort d’une voiture représentent d’im- portantes contributions originales dans le domaine des suspensions actives et le domaine automobile en général

DESIGN OF AN ANTI-JERK CONTROLLER FOR BOTH LOCKED AND SLIPPING TORQUE CONVERTER CONDITIONS IN A VEHICLE

With the advancement in the automotive technologies, the customer scrutiny on the ride comfort of automobiles has come to light. Vehicle drivability is one of the important aspects that defines the ride comfort for a vehicle. Drivability of a vehicle is a qualitative measure and may differ from person to person, however, researches have come up to highlight a few parameters that can categorize the drivability performance of a vehicle into good or bad for a majority of the targeted audience. One of those parameters include shuffle, which is defined as the longitudinal oscillations that occurs in the drivetrain when a sudden demand for torque rise or drop is made. Another such parameter is the sluggishness in the delivery of torque at wheels against the requested torque by the driver. This can exist due to the shift in the dynamics during the drivetrain operation from locked torque converter clutch to slipping torque converter clutch. This work addresses both the drivability related issues, namely, shuffle and torque lag mentioned in the preceding para. Initially, the shuffle oscillations generated in a vehicle are analyzed when subjected to a sudden positive to positive driver torque tip-in request. Further, a pre-compensator and feedback controller based control scheme is designed to damp those shuffle oscillations while keeping the torque delivery response fast. This control approach shapes the actuator torque (i.e., an engine or an e-motor) in such a way that the desired response is achieved. Next, the problem of sluggish torque response at wheels due to slipping of the torque converter clutch is addressed. Initially, a model-based feedforward and feedback controller is developed to control the actuator torque such that when the torque converter slips, an extra compensatory torque from the actuator is applied. This compensation torque ensures that the torque response at the turbine and succeeding driveline components up till the wheels is maintained as desired. However, the actuator has some physical limitations in terms of the maximum magnitude and rate of the torque delivery. So, at some instances, the torque request generated by the controller may not be feasible for the actuator to follow. This problem is addressed when another controller, based on model predictive control approach, is proposed. This controller is based on the approach that continuously updates the controller of the torque delivery of the actuator. The controller solves an optimisation problem over the defined constraints of the actuator and plant, and further finds the most feasible response for the actuator to follow within its defined operating range. Later, A comparison between the two controllers showed model predictive controller to be 15.3% better in terms of the propeller shaft torque response than the feedforward and feedback controller, for the problem under discussion

The empact CVT : dynamics and control of an electromechanically actuated CVT

The large ratio coverage of a CVT and the possibility to choose the engine speed in a wide range independently of the vehicle speed enables the ICE to operate at more fuel economic operating points, making the vehicle potentially more fuel efficient. Unfortunately, because the energy dissipation of the CVT itself is higher than that of a manual transmission, this efficiency improvement is partly lost. The main power losses in the CVT are due to the inefficient hydraulic actuation system and the excessive clamping forces used to prevent the belt from excessive slippage. Direct control of the slip can significantly increase the efficiency. Due to the low actuation stiffness at low hydraulic pressures, the hydraulically actuated CVT is not well suited for slip control. The Empact CVT, developed at the TU/e, is an electromechanically actuated pushbelt type CVT, which has a high stiffness at low clamping forces and is suitable for slip control. This system reduces the steady-state losses, which are dominantly present in a hydraulic system. The goals of this research are to achieve optimal efficiency of this system, to obtain good tracking performance and to prevent the pushbelt from slipping excessively. These objectives are experimentally validated at a Empact prototype, which is tested at a test rig and implemented in an Audi A3 2.0 FSI. The Empact CVT uses two servomotors to actuate the moveable pulley sheaves. To decouple the rotation of the input and output shaft from the servomotor rotations, a double epicyclic set is used at each shaft. The system is designed, such that one (primary) actuator accounts for the ratio changes and one (secondary) actuator sets the clamping forces in the variator. To optimally use the efficiency potential of the Empact system, the slip in the variator must be controlled. In this way, the clamping forces reduce to small values, thereby reducing the friction forces in the gears, spindles and bearings. Efficiency improvements of up to 20 [%] can then be reached at partial load (during 75 [%] of the duration of the FTP72 cycle) compared to a conventionally controlled CK2 147 transmission and efficiency gains of up to 10 [%] compared to an optimally, slip controlled CK2. To gain insight in the physical behavior of the Empact CVT, a multi-body model of the system has been developed, which incorporates a dynamical description of all major components of the test setup. Results show a realistic behavior of the system for both stationary and transient situations. Although this nonlinear simulation model gives a basis for control design and yields a realistic description of the closed loop system, for the actual control design an approximate, linear plant model that describes the frequency domain behavior of the system is estimated. These linearized descriptions are obtained from the simulation model using approximate realization from pulse response data. An iterative model identification and control design procedure is used, such that the plant is estimated in closed loop. In this way, the uncertainty in the frequency range of importance for the design of the controllers is reduced, which leads to less conservative control designs. Parallel to the identification and control design with the simulation model, this procedure is also applied for the test setup. Due to high measurement noise and excessive friction in the system, the quality of the approximated plants at the test setup is relatively low. The time responses are however comparable to the results from the simulation model. An important constraint for the controlled system is that slip cannot be controlled under all operating conditions. At low variator speeds and low loads, the slip controller must be switched off. A decentralized control structure is chosen. Pairing of the in- and outputs is primarily based on the mechanical design of the Empact CVT and are supported by a interaction analysis. The controllers are designed using a sequential loop closing procedure, in which the slip loop is closed last, such that stability of other loops is guaranteed independent of the switching of the slip controller. Using manual loop-shaping, decentralized lead-lag controllers are designed. Nominal stability and performance can be guaranteed. To obtain robust performance, gain scheduling of the slip controller is implemented. Resulting closed loop bandwidth is 8-10 [Hz] for both the ratio and slip control loops. Because the slip dynamics is not well defined at low or zero variator speeds, the slip controller is partly switched off below 2 [km/h]. Both the simulation model and the experimental setup show very good results for disturbance rejection and tracking performance. Torque disturbances of up to 100 [Nm], applied at the secondary variator shaft, can be suppressed within 0.2 [sec] for all ratios. The ratio tracking error is very small compared to conventional CVT systems. Experimental evaluation of the Empact CVT at the test rig showed that the average power consumption of the Empact CVT on the FTP72 cycle is 155 [W], whereas conventional hydraulically actuated CVTs consume over 400 [W] on the average at this drive cycle. Efficiencies of 90 [%], which is close to the maximum efficiency of the Empact CVT, are reached during these experiments. Evaluation of the Empact CVT in an Audi A3 2.0 FSI shows similar performance. Overall, an efficiency improvement of up to 10 [%] is obtained with the Empact CVT compared to a comparable size hydraulically actuated CVT

Integrated vehicle dynamics control using active steering, driveline and braking

This thesis investigates the principle of integrated vehicle dynamics control through proposing a new control configuration to coordinate active steering subsystems and dynamic stability control (DSC) subsystems. The active steering subsystems include Active Front Steering (AFS) and Active Rear Steering (ARS); the dynamic stability control subsystems include driveline based, brake based and driveline plus brake based DSC subsystems. A nonlinear vehicle handling model is developed for this study, incorporating the load transfer effects and nonlinear tyre characteristics. This model consists of 8 degrees of freedom that include longitudinal, lateral and yaw motions of the vehicle and body roll motion relative to the chassis about the roll axis as well as the rotational dynamics of four wheels. The lateral vehicle dynamics are analysed for the entire handling region and two distinct control objectives are defined, i.e. steerability and stability which correspond to yaw rate tracking and sideslip motion bounding, respectively. Active steering subsystem controllers and dynamic stability subsystem controller are designed by using the Sliding Mode Control (SMC) technique and phase-plane method, respectively. The former is used as the steerability controller to track the reference yaw rate and the latter serves as the stability controller to bound the sideslip motion of the vehicle. Both stand-alone controllers are evaluated over a range of different handling regimes. The stand-alone steerability controllers are found to be very effective in improving vehicle steering response up to the handling limit and the stand-alone stability controller is found to be capable of performing the task of maintaining vehicle stability at the operating points where the active steering subsystems cannot. Based on the two independently developed stand-alone controllers, a novel rule based integration scheme for AFS and driveline plus brake based DSC is proposed to optimise the overall vehicle performance by minimising interactions between the two subsystems and extending functionalities of individual subsystems. The proposed integrated control system is assessed by comparing it to corresponding combined control. Through the simulation work conducted under critical driving conditions, the proposed integrated control system is found to lead to a trade-off between stability and limit steerability, improved vehicle stability and reduced influence on the longitudinal vehicle dynamics

Multi-Actuated Vehicle Control and Path Planning/Tracking at Handling Limits

The increasing requirements for vehicle safety along with the impressive progress in vehicle actuation technologies have motivated manufacturers to equip vehicles with multiple control actuations that enhance handling and stability. Moreover, multiple control objectives arise in vehicle dynamics control problems, such as yaw rate control and rollover prevention, therefore, vehicle control problems can be defined as multi-actuation multi-objective vehicle control problems. Recently, the importance of integrating vehicle control systems has been highlighted in the literature. This integration allows us to prevent the potential conflicting control commands that could be generated by individual controllers. Existing studies on multi-actuated vehicle control offer a coordinated control design that shares the required control effort between the actuations. However, they mostly lack an appropriate strategy for considering the differences among vehicle actuations in their energy usage, capabilities, and effectiveness in any given vehicle states. Therefore, it is very important to develop a cost-performance strategy for optimally controlling multi-actuated vehicles. In this thesis, a prioritization model predictive control design is proposed for multi-actuated vehicles with multiple control objectives. The designed controller prioritizes the control actuations and control objectives based on, respectively, their advantages and their importance, and then combines the priorities such that a low priority actuation will not kick in unless a high priority objective demands it. The proposed controller is employed for several actuations, including electronic limited slip differential (ELSD), front/rear torque shifting, and differential braking. In this design, differential braking is engaged only when it is necessary, thus limiting or avoiding its disadvantages such as speed reduction and maintenance. In addition, the proposed control design includes a detailed analysis of the above-mentioned actuations in terms of modelling, control, and constraints. A new vehicle prediction model is designed for integrated lateral and roll dynamics that considers the force coupling effect and allows for the optimal control of front/rear torque distribution. The existing methods for ELSD control may result in chattering or unwanted oversteering yaw moments. To resolve this problem, a dynamic model is first designed for the ELSD clutch to properly estimate the clutch torque. This ELSD model is then used to design an intelligent ELSD controller that resolves the issues mentioned above. Experimental tests with two different vehicles are also carried out to evaluate the performance of the prioritization MPC controller in real-time. The results verify the capability of the controller in properly activating the control actuations with the designed priorities to improve vehicle handling and stability in different driving maneuvers. In addition, the test results confirm the performance of the designed ELSD model in ELSD clutch torque estimation and in enabling the controller to prevent unwanted oversteering yaw moments. The designed stability controller is extended to use for emergency collision avoidance in autonomous vehicles. This extension in fact addresses a local path planning/tracking problem with control objectives prioritized as: 1) collision avoidance, 2) vehicle stability, and 3) tracking the desired path. The controller combines a conservative form of torque/brake vectoring with front steering to improve the lateral agility and responsiveness of the vehicle in emergency collision avoidance scenarios. In addition, a contingency MPC controller is designed with two parallel prediction horizons - a nominal horizon and a contingency horizon - to maintain avoidance in identified road condition uncertainties. The performance of the model predictive controllers is evaluated in software simulations with high fidelity CarSim models, in which different sets of actuation configurations in various driving and road conditions are assessed. In addition, the effectiveness of the local path planning/tracking controller is evaluated in several emergency and contingency collision avoidance scenarios