SDE promises new safety strategies

Advanced safety systems have resulted in huge growth of electronic systems on cars – a trend that will only expand in the coming years as on-vehicle systems increasingly have to communicate not only with each other, but also with other vehicles and the highway infrastructure. These developments are having a significiant impact on weight, cost and system complexity. More and more functionality and system integration in cars means a greater burden on electronic arhictecture – a higher number of interfaces, with each system having its own controller which can be very inefficient.

In line with this trend and to meet the technical aspirations of vehicle manufacturers, TRW has developed a new type of electronic control unit (ECU) which can integrate multiple functions within a single domain controller: the Safety Domain ECU, or SDE. Using the open AUTOSAR (AUTomotive Open System ARchitecture) architecture, the SDE integrates a number of chassis, suspension and DAS control functions and has the processing capacity and flexibility to include software from vehicle manufacturers and third party suppliers.

Why SDE?

TRW started the development work several years ago, combining sensor functions into clusters to reduce the numbers of individual sensors. Several products have resulted from this work including an airbag control unit (ACU) designed to allow the integration of a range of pre-crash occupant safety functions as well as inertial sensors (IMUs) for stability control.

The approach offered several advantages. First, it placed the sensors close to the vehicle’s center of gravity – a prime location for both vehicle impact sensors and inertial sensors. Second, combining inertial sensors and crash sensors into one module allowed alternative methods for diagnostics coverage; inertial sensors could be used to enhance both side impact and rollover detection; with the potential to integrate individual sensors into multiple sensor integrated circuits. Finally, many components required for a standalone inertial sensor module could be eliminated without affecting the electronic stability control (ESC) controller design or performance.

TRW has also integrated the functionality of other systems including its electronic park brake ECU with integrated ESC gyro and two-axis accelerometer and a braking ECU with integrated inertial sensors (IIS).

As a result, safety domain controllers such as TRW’s SDE are driven by the need for enhanced safety functionalities, cost reduction and – on the chassis side – arbitration between systems like braking, steering and suspension to optimize driving behavior while still enabling vehicle manufacturers (VMs) to imprint their own driving characteristics, or DNA, on the vehicle.

Three generations

While high performance electronics are needed to support this trend, standard systems such as airbag and slip control where the fitment rate is now – or soon will be – 100 percent are coming under tremendous cost pressure. At the same time, additional calculation performance for high end functions cannot be afforded while these have fitment rates that could be as low as 20 percent. Instead, these functions are going to be integrated in separate electronic ‘options boxes’. Against this background, it is possible to identify the emergence of three generations of chassis controllers.

The first generation chassis controller has already been launched in some premium segment cars to deliver vehicle dynamics arbitration and to make some enhanced passive and active safety functions possible. DAS sensors such as cameras (CMOS and IR) and radar provide additional warning functions while data is exchanged between new sensors and traditional safety and chassis systems. The additional software required can be implemented in existing sensor or actuator systems. However, systems are designed to be fitted to all cars – whether or not the functionality is needed – which led to a high cost burden for mid and low end vehicles.

TRW took a different approach, preferring to leave airbag and slip control systems (including ABS) with their dedicated and refined hardware and software packages while delegating additional functionality and DAS features to option boxes. Such systems could be described as second generation chassis controllers or, in TRW’s language, a first generation Safety Domain ECU (SDE) that is scheduled to make its appearance in 2013 for a 2014 model year application. This type of controller can focus on collision mitigation or improving passive safety systems based on additional environmental sensing and a high interaction between actuators. It will have more sensors, with higher levels of data fusion between them, arbitration between chassis systems (calling for much more processing power) and a requirement for electronic architecture flexibility to cope with different combinations of systems and functions with different fitment rates.  Data fusion and actuator control cannot be achieved in existing safety or chassis systems without significantly increasing their cost.

A third generation chassis controller could be described as one that has even higher degrees of sensor fusion, leading towards the management of a 360 degree sensing environment and highly advanced features including collision mitigation, semi-autonomous and even autonomous driving. Such capability is expected to be in demand beyond 2015/2016 with the launch of new luxury vehicles. A higher degree of actuator control is anticipated along with electronic integration of active and passive safety.

SDE architecture

TRW’s SDE is a product of this thinking, but also recognizes that VMs want to develop dynamic, safety and control functions of their own which provide unique selling points for their cars that can be recognized in the HMI (human machine interface) or what is known these days as a vehicle’s DNA. To this end, VMs have started to generate their own software and want the suppliers to integrate these packages as so-called ‘black box’ software (with the code invisible to the supplier). While software has, in the past, been strongly linked to the hardware, TRW now sees the software and hardware becoming more independent. This gave rise to a new system design with an open software architecture in which AUTOSAR plays an important role.

A high level of data integration and data fusion means that transferring information in and out of the controller needs to be quick. TRW’s SDE runs FLEXRAY – simply because high speed CANbus networks are limited in such applications. Although FLEXRAY is the preserve of premium vehicles right now, TRW believes that more and more VMs will adopt this standard. TRW is also exploring Ethernet – an interesting solution when considering a much higher number of sensors in the car and the respective data fusion.

New opportunities

The capability provided by SDE’s open architecture structure to integrate control algorithms from VMs and third party suppliers – even direct competitors – will open up new business opportunities for TRW and promote closer technical relationships with customers.