Introduction to Regal ABS

Regal antilock braking systems (ABS) are electronic safety systems found in many modern vehicles. The Regal ABS helps prevent the wheels from locking up during sudden or hard braking, allowing the driver to maintain steering control even under emergency braking conditions. By rapidly modulating the brake pressure at individual wheels, ABS optimizes braking performance and minimizes skidding on slippery road surfaces.

The key components of a Regal ABS include:
– Wheel speed sensors
– ABS control module (EHCU)
– Hydraulic valves
– Pump and accumulator

These work together to continuously monitor wheel rotation and selectively apply and release the brakes as needed. Let’s take a closer look at how these components communicate through the Regal ABS serial data circuits.

Regal ABS Serial Data Circuit Overview

The Regal ABS serial data circuits form the communication backbone that allows the wheel speed sensors, EHCU, and other modules to exchange information. These are typically high-speed, fault-tolerant communication buses like CAN (Controller Area Network).

Key serial data circuits in a Regal ABS include:
– High-speed CAN bus (CAN-C)
– Low-speed CAN bus (CAN-B)
– Local Interconnect Network (LIN)
– Sensor-specific buses (e.g. PSI5, DSI, etc.)

The exact architecture and protocols used vary between different Regal ABS generations and vehicle makes/models. However, the general principles remain the same.

CAN Buses

CAN is the most common serial data bus in automotive applications, including Regal ABS. There are typically two main types of CAN used:

CAN Type	Speed	Purpose
High-speed CAN (CAN-C)	500 kbit/s	Real-time communication between ECUs
Low-speed CAN (CAN-B)	100-125 kbit/s	Less critical communication between body/comfort systems

The Regal ABS control module (EHCU) acts as the central hub and is connected to both CAN buses. It receives wheel speed signals and transmits control messages to the hydraulic valves and pump over the high-speed CAN-C bus.

Other modules that typically communicate with the Regal ABS over CAN include:
– Engine control module (ECM)
– Transmission control module (TCM)
– Electronic stability control (ESC)
– Instrument cluster
– Steering angle sensor
– Yaw/lateral acceleration sensor

By sharing information such as throttle position, engine speed, gear selection, yaw rate, etc., the Regal ABS can make more intelligent braking decisions and coordinate with other vehicle dynamic control systems.

Local Interconnect Network (LIN)

While CAN is used for critical communications, LIN provides a cheaper, lower-bandwidth serial bus for interfacing with simple sensors and actuators in the Regal ABS. Running at 20 kbit/s, LIN is a single-wire, master-slave protocol.

Typical LIN applications in Regal ABS include:
– Brake fluid level sensor
– Brake light switch
– Pump motor status feedback
– Brake pad wear sensors

Sensor-Specific Buses

Some Regal ABS wheel speed sensors use their own dedicated serial protocols to transmit rotation data to the EHCU. Common examples are:

Protocol	Description
PSI5	Peripheral Sensor Interface 5, a two-wire current modulation interface
DSI	Distributed Systems Interface, Bosch’s proprietary interface
Hall Effect	Transmits digital wheel speed using Hall effect sensors and a magnetic encoder ring

These interfaces provide high resolution, deterministic timing, and built-in diagnostics. The Regal ABS EHCU has dedicated inputs for each protocol, which are then synchronized and processed by the ABS algorithms.

Regal ABS Serial Data Circuit Diagram

Here is a simplified diagram showing the key components and serial data connections in a typical Regal ABS system:

        +--------------+
        |  Instrument  |
        |   Cluster    |
        +------+-------+
               |CAN-B 
               |
               |          Wheel          Wheel
       +-------+-------+  Speed          Speed
       |    Engine    +--+ Front    +-+  Rear     
       |   Control    |  | Left     | |  Left      
CAN-C  |   Module     +--+          +-+          
<----->+------+-------+  |          | |             
               |         |          | |
               |         |  Regal   | |             
       +-------+-------+ |   ABS    | | 
       | Transmission | |  EHCU    | |
       |   Control    | |          | |             
       |   Module     +--+          +-+          
       +------+-------+  | Front    | |  Rear     
               |         | Right    | |  Right     
               |         +--+       +-+       
        +------+-------+    |   |                 
        | Electronic  |     |   |LIN                
        |  Stability  +-----+   |                
        |  Control    |         |                 
        +-------------+         |
                            Pump Motor
                            Status                           

As shown, the Regal ABS EHCU forms the central node, connected to the wheel speed sensors, hydraulic valves, pump motor, and other modules through various serial data circuits.

Regal ABS Serial Data Table

The following table summarizes the key serial data parameters for a representative Regal ABS system:

Circuit	Protocol	Speed	Physical Layer	Purpose
CAN-C	CAN 2.0	500 kbit/s	Dual wire differential	Real-time communication with engine, transmission, stability control
CAN-B	CAN 2.0	125 kbit/s	Dual wire differential	Communication with instrument cluster, other body systems
LIN	LIN 2.2	20 kbit/s	Single wire	Interfacing with pump motor, brake fluid level sensor
Front Left Wheel	PSI5	N/A	Two wire current loop	Transmit wheel speed data
Front Right Wheel	PSI5	N/A	Two wire current loop	Transmit wheel speed data
Rear Left Wheel	DSI	N/A	Proprietary	Transmit wheel speed data
Rear Right Wheel	Hall Effect	N/A	Dual wire digital	Transmit wheel speed data

The exact data format, message IDs, and signal definitions are dependent on the specific Regal ABS variant and vehicle platform. Detailed specifications can be found in the relevant service manuals and network databases.

FAQ

What is Regal ABS?

Regal ABS is an antilock braking system that helps prevent wheel lockup during sudden or hard braking. By maintaining wheel rotation, it allows the driver to steer and brake simultaneously, improving safety.

How does Regal ABS work?

Regal ABS constantly monitors the speed of each wheel using sensors. If it detects a wheel is about to lock up, it rapidly opens and closes hydraulic valves to modulate the brake pressure at that wheel. This optimizes braking force while preventing skidding. The system makes these adjustments many times per second.

What are the components of Regal ABS?

The main components are:
– Wheel speed sensors mounted at each wheel
– ABS control module (EHCU)
– Hydraulic control unit with solenoid valves for each brake circuit
– Pump and accumulator to provide hydraulic pressure

What serial data networks are used in Regal ABS?

Regal ABS uses several serial data networks, including:
– High and low speed CAN buses for communication with other modules
– LIN bus for interfacing with simple sensors and actuators
– Dedicated interfaces like PSI5 and DSI for wheel speed sensors

How does Regal ABS communicate with other vehicle systems?

The Regal ABS is connected to the high-speed CAN bus, allowing it to share data with the engine, transmission, stability control and other modules. This integration allows the ABS to make more intelligent braking decisions based on factors like vehicle speed, throttle position, etc. It also supports more advanced functions like electronic brake force distribution (EBD).

Conclusion

Regal ABS serial data circuits form the critical communication infrastructure that enables this important safety system to function. By understanding the CAN, LIN and other interfaces used, technicians can more effectively diagnose and service Regal ABS faults. Consulting the relevant circuit diagrams and data tables is essential when working on these complex, interconnected systems.