Wheel Torque Control Research Articles

Active Damping Wheel-Torque Control System to Reduce Driveline Oscillations in a Power-Split Hybrid Electric Vehicle

Power-split hybrid electric vehicles (HEVs) provide a great opportunity to improve fuel economy and emissions. This power-split hybrid system has inherent low damping in driveline since it uses planetary gear sets to directly connect the engine, the generator, and the motor to the driveline for improved vehicle efficiency, thus lacking a clutch or a torque converter that provides the conventional vehicles with driveline damping. When they are subjected to acceleration or disturbances, the low damping in the driveline may cause torsional vibrations. Since the power-split control system is closed loop in nature, these torsional vibrations can result in sustained driveline oscillations. These oscillations can be very objectionable to the driver as they affect the vehicle's drivability. In this paper, we present the design of an active damping wheel-torque control system to suppress such oscillations to improve the drivability of a power-split HEV. To the best of our knowledge, this is the first reported use of an active damping wheel-torque control system to suppress the driveline oscillations in a power-split HEV. Simulations in a power-split HEV environment and experimental tests in the field using a Ford Escape Hybrid demonstrate the effectiveness of the proposed system in suppressing the oscillations. The driveline disturbances are suppressed to below the perceptible level of wheel torque (<100 Nmiddotm). Additional simulations are performed to validate the system to other key factors that can affect its performance. Even with increased motor/generator disturbances by a factor of 2 and change in driveline stiffness of plusmn50%, the proposed control system can still effectively suppress driveline oscillations and thereby improve drivability.

Integrated control of wheel drive—brake torque for vehicle-handling enhancement

Wheel torque control is an effective means of improving vehicle handling and stability. Brake-based electronic stability programs which intervene in extreme situations to regulate vehicle behaviour are the most common form of wheel torque control. With the advent of advanced driveline technologies, wheel torque control can also be achieved by the differential distribution of available drive torque to all four wheels. Similarly, in combined cornering and braking manoeuvres, the applied brake input can be differentially distributed to regulate vehicle handling. This paper proposes an integrated scheme for wheel torque control that combines differential drive or brake torque distribution with the emergency braking control to regulate the vehicle yaw rate and side-slip angle. A wheel torque controller was developed using a non-linear predictive control theory, an eight-degrees-of-freedom vehicle model, and non-linear tyre models. The simulated vehicle responses show improved vehicle-handling performance.

Robust torque tracking control for E-IVT hybrid powertrain

Abstract This study deals with the control of a hybrid vehicle powertrain, composed of three actuators (one engine, two electric machines). This powertrain belongs to the Electric-Infinitely Variable Transmission (E-IVT) class. In order to achieve low fuel consumption, drivability and electric power management, controllers have to achieve simultaneously three specifications, namely engine speed, wheel-torque and battery power references. Decoupled controlled-output behaviors and optimal performances are also required. In order to imitate a classical powertrain, the control structure is split in two parts. The interest is to decouple transmission speed ratio control and wheel torque control. A model-based design approach is proposed, that directly deals with robustness and decoupling, in a full multivariable and frequency-dependent framework (H∞ synthesis). Closed-loop simulations are presented. Stability and performances subject to disturbances and non-linearities are also evaluated, using the theory of linear parameter varying (LPV) systems.

Vehicle rollover recovery using active steering/wheel torque control

It is well understood that the driver's steering input strongly affects lateral vehicle dynamics, and excessive steering command may result in unstable vehicle motion. In a certain driving condition, it is possible for a skilled driver to prevent vehicle rollover with better perceptive capability of judging conditions and responding faster with smooth compensatory actions. This paper investigates the possibility of using active steering and wheel torque control to assist drivers in avoiding vehicle rollovers in emergency situations. The effectiveness of steering control alone and the combination of steering/wheel torque control in recovery from an unstable roll condition were demonstrated through simulation of both low and high vehicle speeds.

Distributed Robust Control of Compliant Framed Wheeled Modular Mobile Robots

A distributed robust controller for Compliant Framed wheeled Modular Mobile Robots (CFMMR) is studied in this paper. This type of wheeled mobile robot uses rigid axles coupled by compliant frame modules to provide both full suspension and enhanced steering capability without additional hardware. In this research, a distributed nonlinear damping controller using backstepping techniques for wheel-torque control is first developed for single-axle unicycle type robots. The controller is then extended to multiple-axle CFMMR configurations and is robust to disturbances created by modeling errors; especially highly nonlinear frame forces caused by axle interaction. In particular, the controller considers time-varying reference velocities and allows the robot to perform posture regulation, path following, or general trajectory tracking. A two-axle scout CFMMR configuration is used to evaluate the controller. Simulation and experimental results verify robust dynamic motion control of path following.

Lane Keeping Control System with Independent Wheel Torque Control of Micro Electric Vehicle

This paper examines the feasibility of Direct Yaw-moment Control (DYC) in the context of lane keeping system. The DYC, which is generated by differential traction force distribution, is designed with consideration of the road image information to assist the driver's steering maneuver for lane keeping task. Consequently, the controller is designed to regulate the lateral deviation based on the lane marker position acquired via CCD camera with on-board image processing system. The effectiveness of the proposed control system was verified by actual driving test with micro electric vehicle equipped with two independent in-wheel-motors for generating DYC.

Independent wheel torque control of small-scale electric vehicle for handling and stability improvement

This paper examines the feasibility of the proposed control in a small-scale electric vehicle with two independent motors equipped at the rear axles. The direct yaw moment control system is designed with the application of model matching control theory. For realizing the proposed system in an actual electric vehicle, it is necessary to estimate the side slip angle instead of measuring it directly. A speed-dependent observer is proposed in this paper. Experiments using actual small-scale electric vehicle are carried out to verify the effectiveness of the proposed chassis control system on lateral stability in a J-turn test and lane change tests.

Improvement of vehicle handling by nonlinear integrated control of four wheel steering and four wheel torque

A nonlinear control system that integrates active four wheel steering and four wheel torque control is introduced in this paper. The theory for continuous time nonlinear predictive control is applied to the design of the control system. The advantages of coordination of four wheel steering and individual wheel torque control are demonstrated through computer simulations. Simulations in which the driver dynamics are taken into account are also carried out. The results of the simulation show that the vehicle maneuverability and stability can be remarkably improved even in a near limit cornering condition by the proposed nonlinear control system.

Effects of Integrated Control of Active Four Wheel Steering and Individual Wheel Torque on Vehicle Handling and Stability - A Comparison of Alternative Control Strategies -

SUMMARYThis paper investigates the effectiveness of several different combinations of control inputs for improvement of vehicle handling and stability. Three combinations of control inputs are considered in this paper; namely, (1) rear wheel steering control with conventional front wheel steering and standard brake system, (2) four wheel torque control plus conventional front wheel steering, (3) front and rear wheel steering control plus four wheel torque control. The focus of this investigation is to clarify the relative merit of the different control strategies to accomplish a given task. The theory for nonlinear predictive control was extended to take into account partially given input and applied to the design of the control system. Simulations of braking combined with steering and braking under μ-split condition indicate that the integrated control of four wheel steering and individual wheel torque control results in a vehicle that can maintain directional control and stability.

Vehicle dynamics and control synthesis for four-wheel steering passenger cars

This paper is concerned with the active robust autopilot design of a four-wheel steering vehicle against external disturbances. Firstly, the effect of four-wheel steering and independent wheel torques for lateral/directional and roll motions is modelled by a set of linear models under proper manoeuvring conditions. To enhance the dynamic performance of an automobile system, a mixed H2/H∞ synthesis with pole constraint is designed on the basis of full state feedback applying linear matrix inequality (LMI) theory. For lateral/directional and roll motions, the steering angles are actively controlled by steering wheel angles through the actuator dynamics. The wheel power and braking are also controlled by independent wheel torques. Simulation results indicate that the proposed control approach can achieve predetermined performance (or acceptable level of disturbance attenuation) and stability as well as robustness even when external disturbances are severe. The active 4WS car along with steering and wheel torque control algorithms allows greater manoeuvrability and improved stability in a wide range of uncertainty.

STEERING OF 4WD VEHICLES WITH INDEPENDENT WHEEL TORQUE CONTROL

This paper investigates the steering performance of a new configuration of automotive vehicles-4WD vehicles with independent wheel torque control (IWTC). The vehicle model has no steer linkages and a turning manoeuvre can be realised by controlling the wheel torque at each wheel to give a tyre speed differential between the outside and inside tyres. The wheel torque difference between the outside and inside tyres, which controls the tyre velocity difference, is a function of the handwheel angle and the error between the expected yaw rate and the measured yaw rate. In order to control steer stability, a stability compensator for tyre/road adhesion limit is developed and the yaw rate and yaw acceleration are used as control variables. This strategy first evaluates the vehicle stability and then reacts depending on whether the stability criteria is satisfied. The study shows that IWTC vehicles can be well steered by applying the methods developed in this research.

STEERING OF 4WD VEHICLES WITH INDEPENDENT WHEEL TORQUE CONTROL

Abstract This paper investigates the steering performance of a new configuration of automotive vehicles-4WD vehicles with independent wheel torque control (IWTC). The vehicle model has no steer linkages and a turning manoeuvre can be realised by controlling the wheel torque at each wheel to give a tyre speed differential between the outside and inside tyres. The wheel torque difference between the outside and inside tyres, which controls the tyre velocity difference, is a function of the handwheel angle and the error between the expected yaw rate and the measured yaw rate. In order to control steer stability, a stability compensator for tyre/road adhesion limit is developed and the yaw rate and yaw acceleration are used as control variables. This strategy first evaluates the vehicle stability and then reacts depending on whether the stability criteria is satisfied. The study shows that IWTC vehicles can be well steered by applying the methods developed in this research.

Model Following Control of Hybrid 4WD Vehicles

This paper presents a method to design a rear wheel torque control system for hybrid four wheel drive vehicles (H4WD) and the results of its construction to an experimental vehicle. In the H4WD the front wheels are driven by an engine and the rear wheels are independently driven by two motors. The rear wheel torque control system employs a model following approach in which the yaw rate of the vehicle is controlled to track a reference yaw rate. The reference yaw rate is produced from a yaw rate reference model, a first order lag system which has a steering angle as the input signal. From results of computer simulations and experiments, this control system has been found to decrease the deflection of the vehicle due to lateral force disturbance such as lateral wind gusts. It also improves both the stahility and the controllability of the vehicle.