Electronic Brake Pedal Transition Control for Hybrid Vehicles
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Solution Overview
Problem
Conventional electronic braking systems in hybrid and electric vehicles face errors and variances in braking torque requests due to low resolution of force sensors and hysteresis issues, particularly during low force applications, leading to a less than optimal braking performance and feel.
Innovation Solution
A controller with brake pedal transition logic that interpolates between force-based and travel-based braking torque requests using lookup tables, switching smoothly between them when the detected apply force drops below a threshold, and employing a linearized curve to calculate a transition braking torque request, ensuring seamless transition and preventing abrupt changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a force sensor is used to detect brake pedal pressure in an electronic braking system, then the braking torque request can be determined, but the sensor resolution is insufficient under low force conditions leading to errors and variances in braking torque request
Solution Approach 1:
The patent introduces a travel sensor as an intermediary measurement device that indirectly provides braking torque request information through pedal travel position. This mediator bypasses the low-resolution force sensor problem by using a different physical quantity (position) that can be measured with higher precision, and the controller correlates this position data with force-based torque requests to achieve accurate low-force detection.
Solution Approach 2:
The patent changes the measurement parameter from force (pressure) to travel position. By measuring the pedal's displacement rather than the applied force directly, the system achieves higher resolution measurements. The controller then uses this position parameter to determine or interpolate the corresponding braking torque request, effectively converting a low-precision force measurement problem into a high-precision position measurement solution.
2Measurement precision
If a travel position sensor is used to measure brake pedal position, then better resolution is achieved at low pressure ranges, but hysteresis in the braking system leads to errors and variances in applied braking torque request
Solution Approach 1:
The patent merges the advantages of both force-based and travel-based measurement approaches by combining data from both sensors. The controller integrates force sensor readings with travel position sensor readings, using the high-resolution position data to supplement or correct the low-force force measurements. This combination allows the system to leverage the high resolution of the travel sensor while compensating for hysteresis effects through the complementary force sensor data.
Solution Approach 2:
The patent implements feedback control where the controller continuously monitors both force and travel position measurements, compares them against expected values, and adjusts the braking torque request accordingly. When hysteresis causes discrepancies between position-based and force-based torque requests, the feedback mechanism detects these variations and makes real-time corrections to maintain accurate braking control.
3Reliability
If the braking system switches directly between force-based and travel-based torque requests, then sensor limitations are addressed, but abrupt changes cause non-smooth braking transitions and poor pedal feel
Solution Approach 1:
The patent applies dynamic transition logic where the controller continuously evaluates both force-based and travel-based torque requests and smoothly blends between them based on current operating conditions. Rather than abruptly switching between sensors or measurement methods, the system dynamically adjusts the weighting or selection of torque request sources, creating a continuous and smooth transition that maintains consistent braking feel throughout the pedal range of motion.
Data Source
AI summary
A vehicle is provided having a brake pedal with a detectable travel position and apply force, an electronic braking system component, and a controller having a stored threshold braking force and an algorithm. The algorithm determines a first braking torque request corresponding to the apply force, and a second braking torque request corresponding to the travel position. The first request applies when the apply force is greater than the threshold, and the second request applies when it is not. A calculated third request transitions linearly to the second request when apply pressure drops below the threshold upon pedal release. A method is also provided that includes recording the apply force, travel position, and force and travel-based tables, comparing the apply force to the threshold, applying the braking system component using the force-based table when the apply force exceeds the threshold, and otherwise using a calculated braking torque and travel-based table.