Torque-Vectoring, Performance Key to Honda ESC Development
Toyota Focuses on Safety With Advanced ESC Technology
Responsiveness Key to Mitsubishi AWD Development
Nissan Seeks Value in Advanced ESC Systems
Small Size Dictates Technology Development at Subaru
Japan’s six major auto makers are divided into two camps on future strategies for stability-enhancing driveline technologies: safety benefits vs. performance improvements. Part 2 of this 6-part series examines Toyota’s Vehicle Dynamics Integrated Management ESC system.
UTSUNOMIYA, Japan – Toyota Motor Corp.’s main focus for new driveline systems centers on technologies aimed at enhancing safety, such as antilock brakes, brake-assist, active steering and Toyota’s Vehicle Dynamics Integrated Management (VDIM) electronic stability control (ESC) system.
Introduced in 2003 for the Japan-market Crown Majesta, VDIM is an advanced version of the auto maker’s ESC technology that integrates braking and active steering functions into a single package.
If a loss of traction occurs, the system takes over control of steering and integrates with selective wheel braking to help prevent a spin.
In the coming years, the auto maker will focus on actively distributing torque – known as torque-vectoring – to all four wheels, rather than merely braking individual wheels, as most of today’s ESC systems do.
Hideo Inoue, general manager in both Toyota’s Integrated System Engineering and Vehicle Safety and Vehicle Engineering divisions, says VDIM is the only system that integrates all major chassis/powertrain functions: ESC, brake-assist, engine torque control and steering.
However, BMW AG currently offers much of the same functionality for vehicles fitted with its optional Active Steering system. Germany’s Robert Bosch GmbH is believed to be close to supplying a similar system for production vehicles, as well.
Toyota’s basic policy is to first introduce the most advanced systems and technologies into its Lexus luxury lineup and then gradually move downmarket into mainstream vehicles, such as the Camry, RAV4 and Corolla.
Takahiro Goshima, senior chassis engineer at Advics Co. Ltd., Toyota’s braking-system supplier, says because of its current high cost, VDIM will be limited to premium vehicles for the time being.
“ESC is enough for most customers,” he says.
Coming after VDIM, Goshima says a “total drive control” system – integrating steering, braking, engine and transmission controls – will be available for Lexus vehicles by 2010. After that, he expects VDIM to integrate pre-crash braking, laser radar and other new active safety systems.
Timing for widespread introduction of these systems will be linked to reducing costs of controllers and sensors, which Goshima says will be cut in half by 2010.
Meanwhile, he does not foresee a major shift from conventional braking-based traction controls to torque-vectoring or electronically actuated limited-slip differentials until after 2010.
“Traction control is still cheaper,” Goshima says, “thus, the switch (to active torque-management systems), when it comes about, will be cost-driven.”
Made possible by its vast financial and technical resources, Toyota has positioned itself to be the Japanese-market leader in safety technologies, with an ultimate goal of reducing traffic fatalities to zero.
The auto maker has approached the practical limit for passive safety systems and must focus on preventive safety technologies in the future, such as advanced antilock brakes, ESC and active steering.
According to Inoue, torque-vectoring systems still are being evaluated at Toyota on the basis of cost, performance and need.
“Our focus is on improving driving safety (specifically cornering and braking performance) and fuel economy,” he says.
The new Corolla Axio, which went on sale in Japan last fall, is equipped with ESC, a millimeter-wave radar pre-crash avoidance system and a new radar cruise-control system, which monitors both the preceding vehicle and lane position and sets the car’s speed accordingly.
“Actually, we can’t say with certainty that all (Toyota-produced) cars will adopt the system, but we’re moving in that general direction.”
Toyota’s ESC technology, called Vehicle Stability Control (VSC), already is standard on the RAV4 and new Corolla.
Concerning the auto maker’s decision to integrate VSC, traction control, ABS and brake-assist systems into a single control unit, Inoue says that such “batching” is intended to reduce costs.
“By improving pump function and quality we can reduce the size and cost of actuators,” he says.
Advics’ Goshima also says VSC will become standard in all Toyota vehicles by 2015. At present, he estimates 40% of European vehicles are equipped with VSC, with penetration in the U.S. and Japan reaching 15% and 10%, respectively, in 2006.
By 2010, U.S. and European shares will reach 80%, with penetration into the Japanese market rising to nearly 50%.