Electromechanical Braking Systems: Architecture, Redundancy, and Advanced Solutions
Introduction
Electromechanical braking (EMB) systems are increasingly being implemented in drive-by-wire cars as a more advanced and reliable alternative to traditional hydraulic braking systems. An EMB system is characterized by its complex architecture, consisting of a variety of sensors, actuators, processors, memory, and communication networks. The safety-critical nature of EMB systems demands high levels of fault tolerance and reliability, making redundancy a key design consideration. This article delves into the general architecture of an EMB system, the challenges it poses, and advanced solutions developed to address these challenges.
General Architecture of an EMB System
The primary components of an EMB system include:
Processors: An electronic control unit (ECU) and other local processors that govern the system’s functionality.
Memory: Mainly integrated into the ECU for storing critical data and processing instructions.
Sensors: Utilized for monitoring various aspects of the system, such as actuator position, speed, and brake pedal displacement.
Actuators: Responsible for converting electrical signals into mechanical action to apply braking force.
Communication networks: Facilitating communication between the different components of the system.
Redundancy in EMB Systems
Due to the safety-critical nature of EMB systems, redundancy is a vital design consideration. Three main types of redundancy typically exist in a brake-by-wire system:
Redundant sensors in safety-critical components, such as the brake pedal.
Redundant copies of specific safety-important signals, like displacement and force measurements of the brake pedal, copied by multiple processors in the pedal interface unit.
Redundant hardware to perform essential processing tasks, such as multiple processors for the ECU.
Voting Techniques for Redundancy Resolution
To utilize existing redundancy, voting algorithms need to be developed, modified, and adopted to meet the stringent requirements of an EMB system. Reliability, fault tolerance, and accuracy are the main targeted outcomes of the voting techniques.
Advanced Solution: A fuzzy voter developed to fuse information provided by three sensors devised in a brake pedal design.
Missing Data Compensation in EMB Systems
Missing data from safety-critical sensors such as brake pedal sensors and wheel speed sensors pose serious risks to the functionality and safety of a drive-by-wire car. Solutions include redundant sensors, fail-safe mechanisms, and predictive filters.
Advanced Solution: Missing data compensation by a predictive filter.
Accurate Estimation of Position and Speed of Brake Actuators
Efficient design of a measurement mechanism for actuator position and speed is essential. Resolvers are often used for this purpose, but nonlinear and robust observers are required to extract accurate estimates from their sinusoidal signals.
Advanced Solution: A hybrid resolver-to-digital conversion scheme with guaranteed robust stability and automatic calibration of resolvers used in an EMB system.
Measurement and Estimation of Clamp Force in Electromechanical Calipers
Including a clamp force sensor in an EMB system poses cost and engineering challenges. However, accurate estimation of clamp force based on alternative EMB system sensory measurements can potentially eliminate the need for this component.
Advanced Solution: Clamp force estimation from actuator position and current measurements using sensor data fusion.
Improving Communication Networks in EMB Systems
Robust and reliable communication networks are essential in EMB systems to ensure the seamless flow of information between different components. As EMB systems rely on a myriad of sensors and actuators, any communication fault can lead to critical safety issues. Improvements to communication networks can be achieved through redundant communication channels, error detection and correction techniques, and prioritizing safety-critical data transmission.
Advanced Solution: Implementation of a fault-tolerant communication protocol that prioritizes safety-critical data and employs error detection and correction techniques.
Self-Diagnostics and Prognostics in EMB Systems
As vehicles become increasingly dependent on complex electronics, the importance of self-diagnostics and prognostics becomes more significant. Early detection of faults and their potential consequences allows for timely maintenance and prevents catastrophic failures. Advanced self-diagnostics and prognostic techniques can be integrated into EMB systems to ensure the continuous monitoring of system health and predict possible failures.
Advanced Solution: Integration of machine learning algorithms to process sensor data, detect anomalies, and predict potential failures in the EMB system components.
Cybersecurity in EMB Systems
With the rise of connected and autonomous vehicles, the need for robust cybersecurity measures is paramount. Ensuring the security of EMB systems against cyber threats is crucial, as a security breach could lead to fatal consequences. Cybersecurity measures include secure communication protocols, intrusion detection systems, and regular security audits.
Advanced Solution: Implementation of a multi-layered security approach, incorporating secure communication protocols, intrusion detection systems, and continuous security monitoring and updates.
Energy Efficiency and Regenerative Braking in EMB Systems
Optimizing the energy efficiency of EMB systems is an essential aspect of modern vehicle design. Regenerative braking, which converts kinetic energy into electrical energy during braking, is one technique that can improve energy efficiency. Incorporating regenerative braking technology into EMB systems allows for more efficient energy management, ultimately leading to better fuel economy and reduced environmental impact.
Advanced Solution: A novel regenerative braking control algorithm that optimizes energy recovery while maintaining braking performance and stability.
Conclusion
Electromechanical braking systems play a vital role in the safety and performance of drive-by-wire vehicles. By understanding the architecture of EMB systems and addressing the challenges they pose, engineers and researchers can develop advanced solutions to improve fault tolerance, reliability, and overall system performance. Implementing these advanced solutions not only ensures the safety and efficiency of the braking system but also contributes to the continuous evolution of automotive technology.
