Lock-up Clutch Slip Control via Linear Torque Approximation
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Solution Overview
Problem
Conventional slip control devices for lock-up clutches in vehicles face challenges in optimally controlling the slip amount over the entire operating range due to the non-linear characteristics of fluid type power transmitting devices, requiring complex high-order models and controllers that are difficult to tune and comprehend intuitively.
Innovation Solution
A slip control device that calculates the torque capacity of the lock-up clutch by approximating non-linear characteristics with straight lines in minute sections, allowing for intuitive control of the slip amount using a simple configuration, thereby optimizing slip control over the entire operating range without the need for extensive tuning or high-order models.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high-order model and high-order controller are used to account for the non-linear characteristic of the fluid type power transmitting device, then the torque capacity calculation becomes accurate, but the operation to identify the model and design the controller becomes complicated and time-consuming
Solution Approach 1:
The patent divides the non-linear operating range of the fluid type power transmitting device into multiple small linear sections. By segmenting the non-linear characteristic curve into several linear segments, the system achieves accurate torque capacity calculation without requiring complex high-order models. Each segment can be controlled with simple linear control logic, reducing controller design complexity while maintaining precision.
Solution Approach 2:
The patent changes the control parameter from using a fixed high-order model to using variable linear approximation parameters. By adjusting which linear segment is active based on current operating conditions (engine speed, turbine speed, slip speed), the system adapts to non-linear characteristics without the complexity of high-order controllers. This parameter-based switching approach simplifies identification and design operations.
2Measurement precision
If a high-order controller is used to account for non-linear characteristics, then control accuracy is improved, but the coefficient tuning becomes difficult and intuitive comprehension becomes challenging
Solution Approach 1:
By segmenting the non-linear characteristic into linear sections, each with its own simple linear parameters, the patent makes controller tuning intuitive. Each segment's parameters can be independently adjusted based on actual machine behavior in that specific operating range, making tuning straightforward and comprehensible rather than requiring complex high-order coefficient adjustment.
Solution Approach 2:
The patent uses simple linear approximation models that can be easily replaced or adjusted for different operating segments rather than relying on a single complex high-order model. These simple linear parameters are easier to comprehend, tune, and replace if needed, sacrificing the theoretical elegance of high-order models for practical ease of operation.
3Adaptability or versatility
If open loop control is used in non-linear operating ranges and feedback control is used in linear operating ranges, then control adaptability is improved, but the comprehensive tuning of multiple operating ranges becomes enormously complex
Solution Approach 1:
The patent segments the operating range and applies appropriate control strategies to each segment. In non-linear segments, open-loop control based on pre-calculated linear approximations is used, while in linear segments, simple feedback control is applied. This segmentation approach makes comprehensive tuning manageable by breaking it into smaller, independent segment tunings rather than tuning a single complex multi-range controller.
Solution Approach 2:
The patent changes control parameters (control mode, gain values) based on the current operating segment. By switching between different control parameter sets corresponding to different linear segments, the system achieves adaptability across the entire operating range while keeping each segment's tuning simple and independent.
Data Source
AI summary
A slip control device includes a control unit configured to: calculate a difference value between a target value and a current value or an estimated value of a difference in a rotational speed between an input shaft and an output shaft of a fluid type power transmitting device, or a difference value being a difference between a target value and a current value or an estimated value of a speed of an engine; calculate an inclination of torque capacity of the fluid type power transmitting device with respect to an input parameter at a current value of the input parameter having correlative relationship with the torque capacity of the fluid type power transmitting device; calculate torque capacity of a lock-up clutch by multiplying the inclination by the difference value; and control a slip amount of the lock-up clutch by using the calculated torque capacity.