Torque Vectoring Differential Research Articles

Conceptual Design and Energy Efficiency Evaluation for a Novel Torque Vectoring Differential Applied to Front-Wheel-Drive Electric Vehicles

This paper presents a novel differential with lateral torque vectoring activated by an auxiliary motor, called motor-modulated lateral torque vectoring differential, or briefly, MLTD. Its architecture and kinematic characteristics are described, and the optimal cornering performance due to torque vectoring is evaluated using a steady-state vehicle dynamic model. Then, a conceptual design case of MLTD installed in a front-wheel-drive electric vehicle is conducted to assess its feasibility in terms of cornering, driving performances, and energy efficiency performance. The calculations show that an optimal distribution ratio between left and right torques for maximum lateral acceleration can be obtained for a specific cornering condition, further used for DM sizing in the preliminary stage. The simulations for energy consumption at constant-speed turning reveal that energy efficiencies of MLTD are lower than those of conventional differentials with evenly distributed torques. However, this deficiency may be paid off by moderately cutting down the rolling resistance of tire while the superior cornering performances brought by torque vectoring is still preserved. Accordingly, the newly proposed MLTD possesses greater flexibility to improve energy efficiency and driving range of electric vehicles without trading off against its desirable cornering performance and safe handling, and is thus worthy of further development.

Frequency-Domain Analysis and Joint Torque Vibration Suppression Control on Two-Input-Two-Output Torque Difference Amplification Motor Drive System of Electrified Vehicles

<div>To improve the cornering performance, a torque vectoring differential (TVD) that generates a torque difference between the left and right wheels has been developed. Particularly, the use of multiple electric traction motors can easily achieve this. A TVD with a two-motor-torque difference amplification mechanism (TDA-TVD), which employs a unique alignment of planetary gears, has been studied and it can generate a larger torque difference compared to an individual-wheel-drive (IWD) system in the case of using the equal torque output from the traction motors. However, due to the mechanically complicated driving force transmission system including driveshafts and planetary gears, TDA-TVD is prone to cause torsional vibrations of the driveshaft, and the yaw rate of the vehicle body while differential torque is generated. A previous study derived a dynamic model TDA-TVD and designed a vibration suppression feedforward controller. While the study demonstrated a certain vibration suppression performance, it did not strictly consider the load side characteristics during the yaw motion. In addition, there was no frequency-domain analysis either. On the other hand, this study will analyze TDA-TVD in the frequency domain and propose a novel modeling method to construct vibration suppression controllers that deal with both longitudinal motion and yaw motion simultaneously. First, this article shows a theoretical frequency-domain analysis using matrices and obtains resonance frequencies of TDA-TVD. Second, TDA-TVD is modeled based on a summation-differential mode transformation (SDMT). Third, simulations and experimental evaluations of vibration suppression controls using a real vehicle equipped with the TDA-TVD are demonstrated.</div>

Derivation of Dynamic Model of Two-Input-Two-Output Torque Difference Amplification Motor Drive System and Independent Left-and-Right Wheel Control with Decoupling Compensator

A torque vectoring differential (TVD) enhances the cornering performance by generating a torque difference between the left and right wheels. For electrified vehicles, a TVD with a two-motor-torque difference amplification mechanism (TDA-TVD) is proposed, and it generates a greater torque difference than an Individual-wheel-drive (IWD) system under the same power output from the traction motors. However, owing to the complex gear reduction system including planetary gears and driveshafts, TDA-TVD has problems with the vibration of both the driveshaft torque and the yaw rate while cornering. To deal with these problems, a detailed dynamic model of TDA-TVD is first derived in this study. Secondly, a decoupling compensator is designed to achieve independent drive for the left and right wheels so that any motor drive algorithm designed for IWD systems can be applied. Thirdly, a vibration suppression controller is designed. Then, simulations and experimental evaluations using a real vehicle with the TDA-TVD are performed. The experimental results show the effectiveness of the vibration suppression of driveshafts and yaw rate.

Application of Independent-Left-and-Right-Wheel-Driving Force Controller to Torque Vectoring Differential with Two-Input-Two-Output Motor Drive System for Electrified Vehicles

Application of Independent-Left-and-Right-Wheel-Driving Force Controller to Torque Vectoring Differential with Two-Input-Two-Output Motor Drive System for Electrified Vehicles

Low-cost Electric Bus Stability Enhancement Scheme Based on Fuzzy Torque Vectoring Differentials: Design and Hardware-in-the-loop Test

Abstract In this paper, a fuzzy torque vectoring differential controller is proposed to improve the lateral stability for the two-motor-wheel drive electric buses with low sensor cost and computational cost. In order to know the unmeasured sideslip angle, unscented Kalman filter algorithm is used to accurately estimate the sideslip angle based on a nonlinear electric bus model and the measured yaw rate and lateral acceleration signals. Given the advantages of high computational efficiency and human’s heuristic knowledge, fuzzy rules are newly designed to control the torque vectoring differentials, and thereby to provide an extra yaw moment on the electric bus body to compensate the driver steering aiming at stability enhancement. To validate the effectiveness and efficiency of the proposed fuzzy torque vectoring differential controller, hardware-in-the-loop tests were carried out to evaluate the controller performance in real-time under different driving maneuvers and road conditions. The test results indicate that the fuzzy torque vectoring differential controller can significantly improve the handling and path-following accuracy for the two-motor-wheel drive electric buses.

Mathematical modelling of torque vectoring differentials

Active safety systems which distribute forces between the wheels are an integral part of a modern vehicle. The vast majority of systems are based on the brake systems, and reducing engine power, which certainly reduces the vehicle speed. However, the needs of car owners are constantly changing, there is a need for devices capable of ensuring the distribution of traction between the wheels without having to reduce speed. With this task perfectly cope with the main transmission containing the mechanisms of power distribution (MPD). Power distribution mechanisms have a greater impact on vehicle handling. More often meet term, Torque Vectoring Differential (TVD). They began to be used for the first time since the mid-1990s, and found their application in sports cars, and then in executive cars. The described main gears are an integral part of dynamic stabilization systems. During the vehicle development, these systems are developed and investigated using mathematical modeling methods. Therefore, the paper describes the design, operation principle and kinematic design of the most common. The equations systems describing the dynamics of the links and the mechanism as a whole are also composed. The mathematical modeling of vehicles equipped with TVD is modelled.

Integrated Vehicle Dynamics Control Via Torque Vectoring Differential and Electronic Stability Control to Improve Vehicle Handling and Stability Performance

This paper proposed a full vehicle state estimation and developed an integrated chassis control by coordinating electronic stability control (ESC) and torque vectoring differential (TVD) systems to improve vehicle handling and stability in all conditions without any interference. For this purpose, an integrated TVD/ESC chassis system has been modeled in Matlab/Simulink and applied into the vehicle dynamics model of the 2003 Ford Expedition in carsim software. TVD is used to improve handling in routine and steady-state driving conditions and ESC is mainly used as the stability controller for emergency maneuvers or when the TVD cannot improve vehicle handling. By the β−β˙ phase plane, vehicle stable region is determined. Inside the reference region, the handling performance and outside the region the vehicle stability has been in question. In order to control the integrated chassis system, a unified controller with three control layers based on fuzzy control strategy, β−β˙ phase plane, longitudinal slip, and road friction coefficient of each tire is designed in Matlab/Simulink. To detect the control parameters, a state estimator is developed based on unscented Kalman filter (UKF). Bees algorithm (BA) is employed to optimize the fuzzy controller. The performance and robustness of the integrated chassis system and designed controller were conformed through routine and extensive simulations. The simulation results via a co-simulation of MATLAB/Simulink and CarSim indicated that the designed integrated ESC/TVD chassis control system could effectively improve handling and stability in all conditions without any interference between subsystems.

Design and Analysis of a New Torque Vectoring System with a Ravigneaux Gearset for Vehicle Applications

The purpose of this research is to develop a new torque vectoring differential (TVD) for vehicle applications and investigate its effect on vehicle dynamic control. TVD is a technology that is able to distribute the engine torque to the left and right driving wheels at different ratios so that the yaw motion control can be realized. Attention has been paid to this technology in recent years because of its potential to improve the vehicle performance and driving safety. In this study, a new TVD design with a Ravigneaux gearset was developed. This new design is able to use only one pair of gearsets to generate two different speed ratios, and the weight and volume of the system can be reduced. To execute the research, current TVD designs were analyzed and their design principles were clarified. Next, a new TVD design with Ravigneaux gearset was proposed. Then the connecting manner and the gear ratio of the Ravigneaux gearset were discussed. The dynamic equation of the system was then derived and the operation of the system was simulated in a MATLAB program. Further simulation was performed with a vehicle dynamic model in SimulationX to demonstrate the effect of the new system. The results of this study show the potential of building a new TVD with a Ravigneaux gearset and can be helpful for further system development.

Design and Modeling of a Novel Torque Vectoring Differential System

In this paper, a new concept torque vectoring differential (TVD) system is presented. It is shown that the structure and the mechanism of the system, the operating methods, and the parameters design by a simulation program, i.e. SimulationX. First of all, the structure of the new TVD system is introduced, as well as the relevant mechanic equations. Second, we attempt to verify the feasibility and accuracy of SimulationX through establishing a simple mechanical model by MATLAB, so that the further modeling and simulation results of the new TVD system will be credible. Then, the simulation results at the setting conditions are presented. Finally, the sensitivity of the design parameters is analyzed, including adjusting the braking torque and the dimensions of the gear sets in the differential. According to these results, the characteristics of the new TVD system can be derived in order to develop the whole system with vehicle dynamic model in the next stage.

Classification and analysis of electric-powered lateral torque-vectoring differentials

An electric-powered lateral torque-vectoring differential utilizes the output torque of an electric motor for generating the torque difference between the right and the left wheels. Compared with conventional torque-vectoring differentials which utilize the slipping clutch or brake for torque vectoring, electric-powered lateral torque-vectoring differentials have advantages, namely the response and the control accuracy of the torque difference. However, an electric-powered lateral torque-vectoring differential is complex as it is composed of a single electric motor and some planetary gear units; therefore it is difficult to understand its mechanism and characteristics. This paper describes the classification and analysis of electric-powered lateral torque-vectoring differentials. Electric-powered lateral torque-vectoring differentials are studied using the velocity diagram which is utilized for analysis of the conventional torque-vectoring differentials. The analysis shows that the simplest electric-powered lateral torque-vectoring differential is a mechanism of five elements with two degrees of freedom; the mechanism is composed of a single electric motor, one differential gear unit and two planetary gear units; the gear ratios of the planetary gear units are equal to each other. The simplest mechanisms are classified into nine kinds and these have two differences in their characteristics, namely the torque amplification factor between the electric motor and the vectoring torque, and the revolution speeds of one rotational element. Finally, the best mechanism is evaluated from the differences of the characteristics.

Maximum acceptable differential speed ratio of lateral torque-vectoring differentials for vehicles

A lateral torque-vectoring differential consists of a slip clutch for torque vectoring from right to left, another slip clutch for torque vectoring from left to right, differential gears, and some planetary gears which generate the differential speeds of the slip clutches. The present authors introduced a design parameter, namely the maximum acceptable differential speed ratio, and showed that the design parameter is very useful to analyse the lateral torque-vectoring differentials. The minimum of the design parameter is determined by the vehicle driving condition in which the torque-vectoring differential should be activated. In order to find the most appropriate value of the design parameter, this paper studies possible influences — namely the vehicle track, vehicle cornering radius, dynamic tyre radius difference between right and left wheels, lateral torque vectoring, and tyre—road friction characteristic — on the maximum acceptable differential speed ratio. As a result, the lateral torque vectoring and tyre—road friction characteristic should be considered as much as the vehicle track or cornering radius; meanwhile the dynamic tyre radius variation is negligible. Finally, a determination method for the maximum acceptable differential speed ratio is proposed.

Classification and analysis of lateral torque-vectoring differentials using velocity diagrams

This paper describes the classification and analysis of lateral torque-vectoring differentials using velocity diagrams, which are frequently used for the gear-shifting analysis of an automatic transmission. A lateral torque-vectoring differential is composed of the mechanism of torque vectoring from the right wheel to the left wheel, and the similar mechanism of torque vectoring from the left to the right. The analysis shows that, when only the mechanism part of one-way torque vectoring is considered, then the smallest number of the rotational elements composing the one-way torque-vectoring mechanism is four. This is the simplest mechanism. The mechanism is classified into seven kinds of mechanism, namely six clutch-type mechanisms and one brake-type mechanism. The expressions for the clutch torque for torque vectoring, the clutch slip speed, and the energy loss generated by clutch are presented for these mechanisms. As a result, the theoretical value of energy loss is completely the same in these seven kinds of mechanism in the ideal state, in which the transmission efficiency of gears, agitation loss, etc., are assumed to be neglected. Finally, from an actual mechanism design point of view, the best mechanism is evaluated.