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

Abstract

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.

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

“…(5) The energy efficiencies of MLTD at left turn are very close to those at straight driving in the mid/high speed range, while those at right turn are still about 95% lower mainly due to unavoidable loss of power recirculation. (6) The energy deficiencies at right turn may be paid off by moderately cutting down the rolling resistance of tire by 11.1%, e.g., reducing vehicle mass of 1600 kg by about 200 kg, with the superior cornering performances still held using lateral torque vectoring. (7) Conclusively, the newly proposed MLTD possesses greater potential to enhance 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.…”

“…Thereby, the optimal longitudinal forces of wheels applied through the TVD of each drivetrain are attained by analyzing the dynamic limits of the vehicle so that the cornering ability in terms of the maximum lateral acceleration can be found. Kato et al [6] carried out a kinematics analysis on an electric-powered lateral torque vectoring differential (E-TVD) with two degrees of freedom and five elements, consisting of a single electric motor, the first planetary gear, and the second planetary gear. The differential can be classified and characterized by analyzing the relationship between torque and speed of each component using speed diagram.…”

Developing an active variable-wheelbase system for enhancing the vehicle dynamics

“…Direct yaw moment control systems are categorized as differential braking and differential traction systems. [3][4][5] Differential braking systems are widely used in today's cars and have a positive impact on vehicle safety. However, differential braking systems have some weaknesses; for instance, their actuation can disturb the driver and, more importantly, can lead to longer stopping distances during severe braking-in-aturn manoeuvres.…”

Limited-slip and torque-vectoring effect of a dual continuously variable transmission

“…Mitsubishi S-AWC, Honda SH-AWD and ZF Torque Vectoring). Studies of the dynamics and control logic of TVDs have been previously reported, [3][4][5][6][7][8][9][10][11][12][13][14] and the principles of operation have already been explained in detail.…”