Introduction
The steering system is an essential and safety-critical component of any vehicle, responsible for controlling the direction of wheel movement and guiding the vehicle along the intended path.
In our Hello World with MBDT project, the Steering subsystem delivers this capability by driving a steering motor to a desired angle and direction, transmitting the resulting torque to the road wheels through the steering column and rack-and-pinion assembly.
Figure 1. Hello World with MBDT Demo – Steering system
This article series presents the Electric Power Steering (EPS) system in Electric Vehicle (EV) architecture and covers the hardware, software, code generation, and vehicle network integration needed to implement the system using a Model-Based Design (MBD) workflow with MathWorks tools and NXP hardware.
Overview
2.1. What will this series of articles cover?
The articles in this series will present the Steering System within an EV architecture and cover the following topics:
- Software and Hardware Environment
Overview of the MathWorks and NXP tools used to develop, test, and validate the EPS control system. - Logic Control
Description of the model architecture, signal interfaces, and core control algorithms implemented in the Steering System. - Deployment on Real Hardware
Integration with physical hardware, the stepper motor, and configuration of the NXP MCU peripherals required for motor control. - CAN Integration
Definition of the CAN communication interface, including database design and integration on the target NXP platform. - System Validation
Presentation of the final implementation results and validation of the complete system behavior.
2.2. What is the Electric Power Steering System?
Electric Power Steering (EPS) eliminates the hydraulic pump found in conventional steering systems, instead relying on an electric motor driven by an Electronic Control Unit (ECU). Torque and position sensors mounted on the steering column feed real-time measurements to the ECU, which computes the required assist level and commands the motor accordingly. This on-demand assist approach improves energy efficiency, enables precise tuning of steering feel, and provides a programmable interface for Advanced Driver Assistance Systems (ADAS).
Figure 2. Electric Steering Rack and Pinion
EPS systems are classified based on where the electric motor is mounted on the steering mechanism.
- Column Assist Type (C-EPS) - The electric motor and control unit are mounted directly on the steering column inside the cabin.
- Pinion Assist Type (P-EPS) - The electric motor is attached to the pinion shaft within the steering gear box.
- Dual-Pinion Assist Type (DP-EPS) - This system separates the assist function from the steering mechanism. One pinion gear connects the steering wheel, while the electric motor applies assistance to a second, separate pinion gear directly on the steering rack.
- Rack Assist Type (R-EPS) - The electric motor is mounted directly onto the main steering rack, either via a concentric motor around the rack or a belt drive.
- Steer-by-Wire (SbW) - The mechanical connection (steering column and intermediate shaft) between the steering wheel and the wheels is entirely removed.
Key Characteristics of Steer-by-Wire EPS:
- The wheel's movement is handled completely by electronic sensors, algorithms, and actuators
- It allows for completely customizable steering ratios
- Frees up interior cabin space
- Relies heavily on redundant electronics and fail-safes
2.3. Target Audience
This series is intended for engineers and technical stakeholders involved in the development, integration, and evaluation of electric power steering systems, including the following audiences:
- Mechanical and Embedded Software Engineers
- Motor Control & Power Electronics Engineers
- System Architects & Vehicle Architecture Engineers
- Model-Based Design and Simulink Developers
- Academic and Research Communities
Context
In the example vehicle architecture used throughout this series, the Steering System is located in the front zone of the vehicle. The Steering ECU is built around the NXP S32K312 microcontroller, which provides both CAN and LIN connectivity.
The ECU drives the stepper motor to the commanded position and communicates desired angle and direction requests over CAN to the Zonal Controller, which coordinates these signals with the central vehicle control node.
References
Conclusion
This article introduced the Electric Power Steering system architecture, its core components, and its position within a modern EV platform. It outlined the Model-Based Design approach using MATLAB/Simulink and NXP hardware as the development foundation, from algorithm modeling through automatic code generation and hardware deployment.
The next article will focus on the software and hardware environment required to develop, simulate, and deploy the EPS control system using MathWorks and NXP solutions.