Electromechanical braking systems (EMB), also called brake by-wire, replace conventional hydraulic braking systems with a completely “dry” electrical component systems by replacing conventional actuators with electric motor-driven units. This move to electronic control eliminates many of the manufacturing, maintenance, and environmental concerns associated with hydraulic systems.
Because there is no mechanical or hydraulic back-up system, reliability is critical and the system must be fault-tolerant. Implementing EMB requires features such as a dependable power supply, fault-tolerant communication protocols (i.e., TTCAN and FlexRay™), and some level of hardware redundancy.
As in electrohydraulic braking (EHB), EMB is designed to improve connectivity with other vehicle systems, thus enabling simpler integration of such higher-level functions as traction control and vehicle stability control. This integration may vary from embedding the function within the EMB system, as with ABS, to interfacing to these additional systems using communication links.
Both EHB and EMB systems offer the advantage of eliminating the large vacuum booster found in conventional systems. Along with reducing the dilemma of working with increasingly tighter space in the engine bay, this elimination helps simplify production of right- and left-hand drive vehicle variants. When compared to those of EHB, EMB systems offer decreased flexibility for the placement of components by totally eliminating the hydraulic system.
* Connects with emerging systems, such as adaptive cruise control
* Reduces system weight to provide improved vehicle performance and economy
* Assembles the system into the host vehicle simpler and faster
* Reduces pollutant sources by eliminating corrosive, toxic hydraulic fluids
* Removes the vacuum servo and hydraulic system for flexible placement of components
* Reduces maintenance requirements
* Supports features such as hill hold.
* Removes mechanical components for freedom of design
* Eliminates the need for pneumatic vacuum booster systems
EMB systems represent a complete change in requirements from previous hydraulic and electrohydraulic braking systems. The EMB processing components must be networked using high-reliability bus protocols that ensure comprehensive fault tolerance as a major aspect of system design.
The use of electric brake actuators means additional requirements that include motor control operation within a 42-volt power system and high temperature and high density to the electronic components.
In addition to supporting existing communications standards such as CAN and K-line, EMB systems require the implementation of deterministic, time-triggered communications, such as those available with FlexRay, to assist in providing the required system fault tolerance. The EMB nodes may not need to be individually fault tolerant, but they help to provide fail-safe operation and rely on a high level of fault detection by the electronic components.
These new system requirements must be met using high-end components at very competitive prices to replace established, cost-effective technology while maintaining strict adherence to the automotive qualification.
Delivering the large current requirements to stop a large SUV may cause limited adoption at first. The first implementation will be on small car platforms.
Components of the EMB
* Four wheel brake modules
* Electronic controller
* Electronic pedal module with pedal feel simulator and sensors for monitoring driver settings
Advantages of the EMB
* Shorter stopping distances and optimized stability
* More comfort and safety due to adjustable pedals
* No pedal vibration in ABS mode
* Virtually silent
* Environmentally friendly no brake fluid
* Improved crash worthiness
* Space saving, using less parts
* Simple assembly
* Capable of realizing all required braking and stability functions such as ABS, EBD, TCS, ESC, BA, ACC etc.
* Can be easily networked with future traffic management systems
* Additional functions such as an electric parking brake can be integrated easily.