Active Torque Distribution Research Articles

Automatic determination of directional stability parameters of an electric vehicle with a two-motor scheme as part of the torque distribution controller

In case if the front and rear axle of the electric vehicle are not mechanically linked, the presence of automatic torque distribution to the axles or wheels becomes not only an addition to increase the level of consumer properties, but also a necessity. A method for determining the directional stability condition of an electric four-wheel drive vehicle is developed as part of the research by comparing the target and measured yaw rate, and is based on the formulated conditions of drift, skid, and counter steer registration. A method for detecting slipping of the driving wheels of an electric vehicle with a dual-motor scheme is developed, which is based on comparing the target and measured velocity differences of the front and rear axle and includes an auto oscillation detection function. A method for determining the target front and rear axle speed difference in a corner is described. Based on the tests performed, it is concluded that the proposed methods are applicable to the active torque distribution function between the axles of an all-wheel drive electric vehicle being developed by the authors of the paper, which provides improved directional stability and controllability, and counteracts slipping of the drive wheels.

Predictive handling limits monitoring and agility improvement with torque vectoring on a rear in-wheel drive electric vehicle

This work presents a predictive torque vectoring controller that optimally monitors the vehicle limits of handling using active torque distribution in the rear axle of a fully electric vehicle. It works in combination with a feedforward controller designed to improve the vehicle's agility. The overall torque vectoring strategy is described together with the vehicle lateral dynamics, sideslip angle estimator, and torque allocation method. Numerical simulations for various scenarios and road profiles show the benefits of predicting the vehicle's handling limits and the enhancement of vehicle stability in terms of reduced vehicle sideslip angle and driver effort. The proposed optimal control method for predicting vehicle handling limit violations does not require a dedicated solver, making it a promising candidate for real-time applications. The case study is a vehicle equipped with two rear in-wheel motors in the framework of HiPERFORM, an ECSEL Joint Undertaking (JU) European research project. Hardware-in-the-loop (HiL) tests were performed on a dedicated e-axle test bench to integrate the torque vectoring controller with the real e-motors and a dual inverter. The results of the HiL testing demonstrate that the torque-vectoring requirements are satisfied by the hardware configuration in use.

Improved Deep Reinforcement Learning Decision for Integrated Control of Distributed Drive Electric Vehicle Dynamics

To solve the problem of nonlinear coupling with longitudinal and lateral tire forces in the integrated control of distributed driving electric vehicles, an improved SAC reinforcement learning algorithm is proposed to coordinate the control method of active front steering (AFS) and torque distribution. The coordinated control adopts a layered structure, and the upper layer adopts the LQR controller to determine the additional front wheel rotation angle and yaw moment required for stability control. The three-level reward function is designed with the goal of vehicle stability and state tracking and is determined by the reinforcement learning algorithm. For the weight factors of the two optimization objectives, the SAC reinforcement learning algorithm is used to coordinate the decision-making of the active front wheel steering and the additional yaw moment; the lower controller uses the comprehensive utilization rate of the tire as the objective function to perform the optimal torque distribution. A co-simulation platform is established in MATLAB/Simulink and CarSim software. The results show that compared with AFS control, SAC coordinated control can not only ensure the stability of the vehicle and achieve accurate tracking of the reference state but also effectively reduces the comprehensive utilization rate of tires and the effectiveness of coordinated control.

A joint control method considering travel speed and slip for reducing energy consumption of rear wheel independent drive electric tractor in ploughing

Improving tractor traction efficiency is greatly important in increasing energy efficiency and reducing fossil fuel consumption. However, the wheeled tractors have problems with low traction energy efficiency and severe energy consumption due to excessive wheel slip in ploughing. This paper proposed a joint control method considering the travel speed and slip based on the active torque distribution, which is applied to the independent drive electric tractors. Considering the influence factors of time-varying resistance and terrain elevation in ploughing, a time-varying dynamical model for the tractor-implement combination was established to reveal the load transfer rules. Then the optimal slip values of the driving wheels were solved in real-time, and a sliding mode algorithm was used to control the motor torque for efficient tractor operation. Moreover, a hardware-in-the-loop platform was built, and ploughing tests were performed. The results indicated that the tractor slip, traction energy efficiency and motor energy consumption of the tractor were optimal in the torque active distribution mode. Compared to the torque average distribution mode, the proposed method reduced the tractor slip by 14.1%, the motor energy consumption by 6.8% and increased the traction energy efficiency by 6.8%. This study provided technical support for reducing energy dissipation in ploughing.

A sensorless traction strategy for all-wheel drive electric motorcycles

Motorcycle designers aim to enhance vehicle performance, stability, and safety, especially when the vehicle is approaching the tyres' friction limit. A strategy to achieve these purposes is to design All-Wheel Drive (AWD) vehicles with active torque distribution. Nowadays, effective technical solutions for powering the front wheel of a motorcycle have been proposed. The use of traction on both front and rear wheel is convenient when tyre friction is low, enhancing vehicle safety and performance. In this context, this paper presents a sensorless, open-loop traction strategy for AWD motorcycles that improves performance and stability both in straight running and in cornering, without requiring the knowledge of road-tyre adherence. This novel traction distribution strategy is based on the idea of maximising the area of the motorcycle performance envelope, also known as g-g diagram. A simplified mathematical model is used to find closed-form solution to this problem, then converted into a control algorithm for the front and rear driving torques. The performance of the proposed method is assessed with simulations: a detailed model of a light electric motorcycle is used for calculating the non-linear vehicle performance envelope, the acceleration response in straight running and cornering, and the response to road irregularities. Moreover, a comparison with feedback slip-based traction control system is conducted. Simulation results indicate that the AWD motorcycle outperforms the conventional rear wheel drive motorbike almost in all situations, especially when road-tyre adherence is low, and that no counter-indication for the adoption of the AWD architecture exists.

Interacting multiple model-based adaptive control system for stable steering of distributed driver electric vehicle under various road excitations

Distributed driver electric vehicle (DDEV) works under various road excitations in practice, which may cause the changes in steering performance significantly. However, the various road excitations are not a priority for stable steering problem of DDEV, and this possibly leads to unstable steering performance, particularly oversteer or tail flick. To solve this problem, an interacting multiple model-based adaptive control system (IMM-ACS) is presented in this work. The proposed IMM-ACS integrates an interacting multiple model controller (IMMC) and a stable steering controller (SSC). The IMMC is designed to establish an adaptive vehicle model based on four typical road models, and to improve the adaptability of control system to various road excitations by the model interaction method. The SSC is designed to guarantee the yaw and longitudinal stability based on the adaptive vehicle model, by the active steering and torque distribution, and the SSC is realized by the model predictive controller (MPC). Besides, this work establishes a Carsim-Matlab co-simulation platform, where the simulation is designed and the results show that the proposed IMM-ACS can achieve excellent steering performance for DDEV with the adaptive capacity.

DLMPCS‐based improved yaw stability control strategy for DDEV

The yaw stability of distributed drive electric vehicle (DDEV) can be guaranteed by the active steering and torque distribution systems. Conventional yaw stability control strategy mainly focuses on the study of yaw moment, while the tyre lateral saturation and excessive longitudinal skid problems are difficult to be solved efficiently. This may lead to the unstable yaw phenomenon of the vehicle such as the sideslip or tail flick. To improve the yaw stability of DDEV under the tyre lateral saturation and excessive longitudinal skid situations, a double-layer model predictive control system (DLMPCS) is presented in this work. The proposed DLMPCS consists of an anti-saturation yaw stability controller (AYSC) and an anti-slip torque distribution controller (ATDC). The AYSC is designed to guarantee the vehicle yaw stability under the tyre lateral saturation situation, through the active steering and yaw moment. The ATDC is designed to realise the torque distribution and keep the longitudinal slip ratio within the stable zone; then, the vehicle can be prevented from the excessive skid phenomenon. The simulation results confirm the improved yaw performance of the DLMPCS for DDEV under different situations.

Active torque distribution strategy for electric vehicle independent axle drive

Vehicles equipped with an electric independent axle drive have different properties compared to conventional vehicles. Distribution of driving or braking torque can be achieved by the proper control of the operation of electric machines without applying additional mechanisms. In this paper a method of active torque distribution between front and rear axles is presented. The method allows to use the maximum tyres adhesion and minimize slips. The results of simulation tests are presented, in which the active torque distribution with evenly torque distribution were compared.

Reliable Integrated ASC and DYC Control of All-Wheel-Independent-Drive Electric Vehicles Over CAN Using a Co-Design Methodology

This paper deals with the negative effects of the in-vehicle network on the integrated anti-slip control (ASC) and direct yaw-moment control (DYC) of all-wheel-independent-drive electric vehicles (AWID-EVs). In the integrated control design of the modern AWID-EVs, increasing control components, e.g., sensors, controllers, and actuators, are usually connected via an in-vehicle network, such as a controller area network (CAN), rather than the traditional point-to-point communication. However, the application of CAN would also bring about unexpected problems, e.g., signal asynchrony, multiple-package transmission, and signal delay, which may degrade the control performance and even destroy the stability of the system. This paper presents a co-design methodology to deal with all these challenges caused by CAN and guarantees a satisfactory vehicle dynamics performance. First, a hierarchical structure is designed for the integrated ASC and DYC control of AWID-EVs over CAN, and an active torque distribution strategy based on a well-known maximum transmissible torque estimation approach is adopted. Then, a scheduling-based communication idea is introduced to deal with all these problems caused by CAN. Third, a Lyapunov-based pole assignment theory is applied to estimate the parameter values in the scheduling design and to guarantee the satisfactory dynamic performance of the control system. A generalized linear quadratic regulator controller is designed for the system synthesis to ensure the tracking control of the vehicle. Finally, simulations and preliminary hardware-in-loop tests indicate that the proposed co-design methodology can deal with the negative effects of the in-vehicle network and ensure reliable vehicle dynamics performance.

Multibody dynamics simulation of an all-wheel-drive motorcycle for handling and energy efficiency investigations

ABSTRACTIt is now possible, through electrical, hydraulic or mechanical means, to power the front wheel of a motorcycle. The aim of this is often to improve performance in limit-handling scenarios including off-road low-traction conditions and on-road high-speed cornering. Following on from research into active torque distribution in 4-wheeled vehicles, the possibility exists for efficiency improvements to be realised by reducing the total amount of energy dissipated as slip at the wheel–road contact. This paper presents the results of an investigation into the effect that varying the torque distribution ratio has on the energy consumption of the two-wheeled vehicle. A 13-degree of freedom multibody model was created, which includes the effects of suspension, aerodynamics and gyroscopic bodies. SimMechanics, from the MathWorks, is used for automatic generation of equations of motion and time-domain simulation, in conjunction with MATLAB and Simulink. A simple driver model is used to control the speed and yaw rate of the motorcycle. The handling characteristics of the motorcycle are quantitatively analysed, and the impact of torque distribution on energy consumption is considered during straight line and cornering situations. The investigation has shown that only a small improvement in efficiency can be made by transferring a portion of the drive torque to the front wheel. Tyre longevity could be improved by reduced slip energy dissipation.

Vehicle handling control of an electric vehicle using active torque distribution and rear wheel steering

Vehicle handling control of an electric vehicle using active torque distribution and rear wheel steering

Vehicle handling control of an electric vehicle using active torque distribution and rear wheel steering

There are two objectives of this work. First is to develop a detailed mathematical model of a vehicle. The second is to develop a controller which makes the vehicle follow desired dynamic characteristics. Suspension kinematics and compliance characteristics have been obtained from the complex suspension models developed in Adams Car®. Vehicle roll-pitch interactions and variations of roll and pitch centres with respect to wheel travel are considered. The controller is developed as a combination of force allocation control and active rear wheel steering control. Reference trajectories of vehicle velocity, path geometry and vehicle slip angle are the inputs. The controller transforms these user inputs and generates wheel torques and steering commands. A desired value of yaw rate is maintained by generating a restoring yaw moment from unequal torque distribution, and side slip is substantially reduced by active rear wheel steering controller. Finally simulation results illustrate the suitability of the controller.

MPC-based yaw stability control in in-wheel-motored EV via active front steering and motor torque distribution

This paper focuses on yaw stability control of in-wheel-motored electric vehicle (EV), and a model predictive controller is designed based on holistic control structure via active front steering and motor torque distribution. By designing a suitable reference model, the controller stabilizes a vehicle along the desired states while rejecting skid and fulfilling its physical constraints, so this is described as a constrained tracking problem. To solve this, the holistic control scheme is built to simplify the hierarchical structure of the controller and directly optimize the control inputs of system. Based on holistic control structure and MPC method, an objective function with constraints is designed over a receding horizon to meet the control requirements. Finally, the proposed nonlinear model predictive controller is evaluated on eight degrees of freedom (8DOF) EV model offline simulation platform. Simulation results of different road maneuver on slippery surfaces show the benefits of the control methodology used.

On the multi-wheeled off-road vehicle performance and control

For off-road vehicle applications, the construction of drivetrain system has usually been largely dominated by the mobility requirements. With the growing demand to have a multi-purpose on/off road vehicle with improved manoeuvrability over deformable soil, particularly at higher speed, the challenges opposing vehicle designers have become more complex. In addition to the conventional mechanical torque distribution devices, active torque distribution (ATD) systems utilise active differentials to control the drive torque independently distributed to each driving wheel and accordingly provide active control of traction and yaw moment. In this paper the multi-wheeled off-road vehicle performance and control is presented and different critical aspects are summarised and critically discussed.

Autonomous vehicle collision avoidance system using path planning and model-predictive-control-based active front steering and wheel torque control

Autonomous vehicles have attracted more attention in recent years as vehicle applications are evolving to a more intelligent and autonomous stage. This paper presents the development of a collision avoidance system for an autonomous vehicle application which consists of a motion planner and model-predictive-control-based active vehicle steering and active wheel torque control. A motion planner, based on polynomial parameterization, determines a collision-free trajectory when a vehicle collision with obstacles is likely to happen. Then an MPC-based control system controls the front steering and individual wheel torques to track the desired collision-free reference trajectory. The proposed system is evaluated through simulation, using an eight-degrees-of-freedom vehicle model with a ‘magic formula’ tire model, active front steering, and active wheel torque distribution systems. The simulation results show that it effectively performs collision avoidance maneuvers.

The vector drive rear axle transmission

Goal-directed utilization of active torque distribution to the four drive wheels has become increasingly important in the last few years, especially with a view to improving both driving dynamics and traction. With the Vector Drive rear axle transmission, ZF generates such a torque vectoring system at the rear axle. This paper describes how such a rear axle torque vectoring system can be implemented while fulfilling the requirements of precise torque control and robust functional availability with adherence to safety requirements as well as suitability for volume production. Based on the technical description of the system and its setup, the interaction of the individual components within the overall functionality is demonstrated.