Method for controlling an electromechanical steering system in a semi-autonomous driving mode of the steering system with a position control using a boost control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In semi-autonomous or semi-automatic driving modes, the interaction between the position controller and torque controller in electromechanical steering systems can lead to undesirable oscillations due to interference, affecting the steering feel.
Innovation Solution
A method combining position control and torque control before boost control, utilizing an LQG controller with a Kalman filter and linearized gain curve, to determine the steering column offset torque, and incorporating a damping unit to stabilize the control loop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If torque is applied to the steering wheel in semi-autonomous mode, then the steering wheel rotates, but the steering angle changes unintentionally causing instability
Solution Approach 1:
A torque sensor is introduced as an intermediary device to detect the torque applied to the steering wheel. This sensor acts as a mediator between the driver's input and the steering control system, allowing the ECU to measure the torque and compensate for its effects on the position control, thereby maintaining steering angle stability while permitting wheel rotation.
Solution Approach 2:
The system implements feedback control by continuously monitoring the actual steering angle via a steering angle sensor and comparing it with the target steering angle. When deviations occur due to torque application, the ECU adjusts the motor output accordingly to maintain the desired steering angle, creating a closed-loop control system that stabilizes the steering position.
2Measurement precision
If position control is used in semi-autonomous mode, then steering angle accuracy improves, but system complexity increases due to additional sensors and control mechanisms
Solution Approach 1:
The ECU is designed to perform multiple functions: it controls the motor in both autonomous and semi-autonomous modes, processes data from multiple sensors (position sensor, torque sensor, steering angle sensor), and adapts its control strategy based on the operating mode. This multi-functionality reduces the need for separate dedicated control units for different operating modes.
Solution Approach 2:
The system uses existing sensors (steering angle sensor, motor position sensor) that are already part of the steering system for their primary functions, and leverages their data for the enhanced position control in semi-autonomous mode. This self-service approach avoids adding redundant sensors and utilizes available resources efficiently.
3Speed
If torque is applied during autonomous mode, then steering responsiveness improves, but position control accuracy deteriorates
Solution Approach 1:
The control system dynamically adjusts its behavior based on the operating mode (autonomous vs. semi-autonomous) and real-time conditions. In autonomous mode, the system allows torque-induced rotation for responsiveness while using feedback from position sensors to maintain accuracy. The ECU continuously adapts the motor control parameters to balance responsiveness and precision according to the current operational context.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach prevents stability issues and enhances the control loop stability, ensuring a smoother and more stable steering experience.
Implementation Method 1
an output force generated by an actuator (20) having an output stroke in the extending and retracting directions of an output shaft (20b)
Data Source
Figure 1
Figure 2
AI summary
The invention relates to a method for controlling an electromechanical steering system (1) in a semi-autonomous steering process, having the following step: • - determining a required motor torque (MotReqTrq) for actuating an electric motor (9) of a servo unit (10) of the electromechanical steering system (1), wherein a boost control (14) is carried out which determines the required motor torque (MotReqTrq) on the basis of a manual torque (TsuTrq) applied to the steering wheel, the vehicle speed (VhlSpd), and the steering column offset torque (TsuTrq offset), said steering column offset torque (TsuTrq offset) representing the position control of the electric motor (9), of a steering pinion, or of a steering rack.