Electronic Safety Systems Enable Fuel-Saving Hybrids

Jan. 1, 2008
The market for safety and fuel-saving technologies is on the rise and consumers are demanding vehicles that are more safe, fuel efficient and environmentally

The market for safety and fuel-saving technologies is on the rise and consumers are demanding vehicles that are more safe, fuel efficient and environmentally friendly. While safety remains a top priority for consumers looking to purchase their next vehicle, the ever-increasing price of gas has prompted vehicle manufacturers to develop hybrid-electric and alternative powertrain vehicles at an unprecedented pace.

The challenge for safety systems suppliers is to develop high-performance hybrid-enabling technologies that help improve fuel economy and reduce CO2 emissions. While these safety technologies are not intended exclusively for hybrids, they facilitate the transition from fully gasoline or diesel-power vehicles to gasoline-electric and diesel-electric hybrids.


A prime case in point are electric steering systems, including electrically powered hydraulic steering (EPHS) and electrically powered steering (EPS), which can be tailored for hybrid-electric vehicles (HEVs). Electric steering technology enables dynamic steering characteristics not possible with hydraulic steering. Because this technology does not use a hydraulic pump, the technology only consumes energy when steering assist is needed.

EPHS systems are ideal for converting from a standard hydraulic-based steering system to electric steering for a hybrid vehicle. EPHS offers decreased energy consumption and CO2 emissions by allowing the motor pump unit to operate the steering system at lower vehicle speeds and only consuming energy when demanded.

EPS — which offers optimized fuel efficiency in comparison to conventionally assisted steering systems — is an efficient electric steering system that offers greater fuel efficiency than EPHS when compared to hydraulic power steering. Designed to support a range of vehicle platforms, several suppliers, including TRW Automotive, offer a column drive system with the motor unit located on the steering column for smaller vehicles. For vehicles up to 6,000 pounds gross weight, a belt-drive electric-steering system extends the advantages to D segment and crossover vehicles. Both EPHS and EPS solutions can be applied across platforms that feature conventional and HEVs.

Electric steering can also be incorporated with other vehicle control functions, such as electronic braking systems, to offer integrated functions. An example of this is steering torque control, which combines electric steering and electronic stability control (ESC) functions. The system helps “coach” the driver to steer in the proper direction during potential loss of control, such as skidding and sliding on slippery surfaces. The system encourages the driver to give the optimal steering input by introducing a small amount of torque making it easier to steer in the right direction to correct vehicle instability. It also helps to reduce stopping distances on road surfaces, such as black ice, on otherwise dry pavement.


Another advantage offered by hybrid electric vehicle architectures is the capture of brake energy that is lost in a conventional powertrain. This is known as “regenerative braking,” which allows a vehicle to recapture and store part of the kinetic energy that would otherwise be lost to heat when braking. This energy is used to recharge the electric batteries and save on fuel in a hybrid architecture.

An electric motor can use electricity to create torque or reverse the process to use torque to create electricity. In the case of regenerative braking, the torque created by the electric propulsion motor is applied to one or both of the axles to slow or stop the vehicle. Because this regenerative force is not able to meet all the needs for braking over all speeds and conditions, conventional friction braking is required and is blended with the motor torque to achieve full braking.

A brake system is about safely stopping the vehicle. Systems are being developed that offer the brake blending needed to stop the vehicle and generate the energy to help recharge the batteries. These systems go a step further by enabling full ESC functionality that helps drivers to keep their vehicles under control during challenging driving conditions and emergency maneuvers. These systems are being launched on hybrid vehicles and systems are under development to enhance performance, functionality and reduce component size and weight.


Of course, lighter weight and smaller components across the range of chassis and occupant safety technologies help to reduce fuel consumption and C02 emissions in petroleum-based HEVs and other alternative powertrains. The drive toward smaller and lighter is an ever-present feature of the automotive landscape.


Studies show that a significant portion of fuel is consumed in operating the vehicle's climate control system, presenting yet another challenge to suppliers of heating, ventilation and air-conditioning controls. One solution with great promise is the development of algorithms that predict an occupant's comfort based on heat transfer, which considers all heat sources: conduction, convection and radiation. The result is a system that keeps windows clear of fog and drivers and passengers content in all weather conditions, while reducing the energy draw on the engine when air conditioning is switched on, thus saving fuel.

While making considerable advancements to safety and hybrid-enabling technologies designed to enhance occupant protection, TRW engineers continue to develop competitive ways of integrating braking, steering, occupant safety and climate control subsystems to improve the performance, safety and comfort of conventional and hybrid vehicles.


As executive vice president for Sales and Business Development at TRW Automotive, Peter Lake is responsible for sales, product strategy, business development and marketing on a global basis. Lake is a 25-year veteran of the company.


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