Engine Torque Traction Control With Drivetrain Linearization
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Solution Overview
Problem
Existing traction control systems fail to effectively account for nonlinearities in vehicle dynamics and oscillatory behavior of the drivetrain, leading to poor control quality, high application effort, and instability, particularly due to neglecting actuator dynamics and uncertain vehicle parameters.
Innovation Solution
A cascaded controller structure is introduced that models drivetrain dynamics, identifies parameters through testing, and employs a nonlinear controller design using input-output linearization, shifting control from slip to engine speed regulation, and incorporating a first-order low-pass model for engine dynamics and a two-mass oscillator model for the powertrain, with numerical filtering to address uncertain tire forces and road conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a classic traction control structure is used where the DCU detects wheel slip and generates a limiting torque that is passed to the ECU, then the system is simple to implement, but the control quality is poor and the response is slow
Solution Approach 1:
The control system is divided into two independent control loops: an outer loop in the DCU that determines the limiting torque based on wheel slip detection, and an inner loop in the ECU that precisely controls engine torque. This segmentation allows each controller to be optimized for its specific function, improving overall control quality while maintaining implementation simplicity.
Solution Approach 2:
The patent introduces a new control structure where the DCU acts as an intermediary that processes wheel slip information and generates a limiting torque setpoint, which is then transmitted to the ECU for precise execution. This intermediary role enables faster and more precise controlling compared to the state of the art where the DCU directly controlled wheel slip without this intermediate processing step.
2Device complexity
If nonlinearities and oscillatory behavior are neglected in the control design, then the control structure is simpler, but the tracking performance and disturbance attenuation are poor
Solution Approach 1:
The patent implements a feedback mechanism where the actual engine torque is continuously measured and compared with the limiting torque setpoint. The difference is used to adjust the control signal, enabling the system to compensate for nonlinearities and oscillatory behavior without requiring a complex control structure. This feedback approach improves tracking precision while keeping the control structure relatively simple.
Solution Approach 2:
The control system dynamically adjusts control parameters based on operating conditions. The ECU modifies the engine torque output in real-time to account for nonlinearities in the drivetrain and oscillatory behavior, achieving good tracking performance without requiring a overly complex control structure that explicitly models all nonlinearities.
3Device complexity
If actuator dynamics are not considered during the design process, then the design is simpler, but stability cannot be proven and control performance deteriorates
Solution Approach 1:
The patent incorporates actuator dynamics considerations into the control design phase. The ECU is programmed with knowledge of engine response characteristics and actuator behavior, allowing it to anticipate and compensate for dynamic effects before they manifest as instability. This preliminary consideration of actuator dynamics enables stability without requiring excessively complex design procedures.
4Ease of manufacture
If uncertain vehicle parameters are used in the control laws, then the controller is easier to implement, but the control quality deteriorates due to estimation errors
Solution Approach 1:
The control system uses readily available sensor data from the vehicle's existing measurement systems (wheel speed sensors, engine sensors) to determine control actions. Rather than requiring precise knowledge of uncertain parameters like friction coefficient or tire characteristics, the system serves itself by using actual measured values to adapt to current operating conditions, maintaining good control quality without complex parameter estimation.
Data Source
AI summary
A system and method for speed/traction/slip control influences a driving engine torque of the vehicle. The method includes: calculating an idealized nominal engine torque from a linear control law applied to the speed/slip error; calculating an idealized setpoint for the speed/slip by applying a reference model to the idealized nominal engine torque; calculating a linearizing feedback with properties of compensating the nonlinearities in the road surface contact, compensating the inertia in the powertrain, and damping the powertrain; using for feedback the engine rotational speed, numerically determined derivation of engine speed, average speed of the driven axis, numerically determined derivative of the rotational speed of the driven axis, actual engine torque, and applying the driving engine torque to the engine vehicle to influence the traction and stability of the vehicle.