Vehicle Driveline and Wheel Brake Control for Predictable Deceleration
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Solution Overview
Problem
Existing electric vehicle drivelines face challenges in controlling acceleration and deceleration, particularly when the energy storage system is fully charged, leading to inefficient utilization of regenerative braking systems and unpredictable vehicle behavior.
Innovation Solution
A method that includes receiving acceleration or deceleration control signals, setting threshold limits based on vehicle conditions, comparing actual acceleration/deceleration with these limits, and applying a wheel brake system to adjust vehicle speed to maintain desired acceleration/deceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the energy storage system is charged up to a certain upper limit below 100% to enable regenerative braking, then the regenerative braking system can provide sufficient braking power, but the full potential of the energy storage system cannot be utilized
Solution Approach 1:
The patent dynamically adjusts the upper charge limit of the energy storage system based on driving conditions, vehicle speed, and brake system requirements rather than using a fixed threshold. This allows the system to charge closer to 100% when regenerative braking is not needed while maintaining sufficient braking capability when required.
Solution Approach 2:
The system changes the operating parameters of the energy storage system by adjusting the state of charge threshold dynamically. The control unit modifies the upper charge limit parameter based on real-time conditions, enabling the energy storage system to operate more efficiently and utilize its full potential while maintaining braking performance.
2Reliability
If a hydraulic wheel brake system is activated when the vehicle travels at high speed down a hill and the energy storage system is at or above 95% state of charge, then the vehicle can be braked effectively, but the control of acceleration and deceleration remains unpredictable in other scenarios
Solution Approach 1:
The patent implements a feedback control mechanism where the control unit continuously monitors actual vehicle acceleration and deceleration, compares it with desired values, and adjusts the wheel brake system accordingly. This closed-loop control ensures predictable and reliable acceleration and deceleration across all driving scenarios, not just downhill braking.
Solution Approach 2:
The system performs preliminary calculations of expected acceleration and deceleration based on driveline control signals, and proactively applies wheel brakes when deviations are anticipated. This preventive approach maintains predictable vehicle behavior before problematic situations arise.
3Ease of operation
If the driveline is controlled in response to acceleration or deceleration control signals, then the vehicle can respond to driver input, but the resulting acceleration or deceleration may be higher or lower than desired
Solution Approach 1:
The control unit continuously compares the actual vehicle acceleration and deceleration with the desired values derived from control signals. When deviations are detected, the system adjusts the driveline and/or wheel brake system to correct the discrepancy, ensuring precise control matching driver intent.
Solution Approach 2:
The wheel brake system acts as an intermediary mechanism that fine-tunes the vehicle's acceleration and deceleration. When the driveline alone cannot achieve the desired rate of change, the wheel brakes provide supplementary control to bridge the gap between intended and actual vehicle response.
Data Source
AI summary
The invention relates to a method for operating a vehicle (1), wherein the vehicle (1) comprises: a driveline (2, 4) configured to provide a driving power to at least one wheel (3) of the vehicle (1) for propulsion of the vehicle (1); and a wheel brake system (5) configured to brake the vehicle (1), wherein the method comprises the steps of: receiving (S1) a control signal indicative of a request for acceleration or deceleration of the vehicle (1), wherein the acceleration or deceleration control signal is generated by an accelerator device, such as an accelerator pedal, configured to be acted upon by a driver of the vehicle (1); and controlling (S2) the driveline (2, 4) in response to the acceleration or deceleration control signal. The method comprises the steps of: providing (S3) an acceleration or deceleration threshold limit representing i) the highest vehicle acceleration that can be allowed for the received acceleration control signal in the current circumstances, or ii) the lowest vehicle deceleration that can be allowed for the received deceleration control signal in the current circumstances; determining (S4) a resulting vehicle acceleration or deceleration that is or will be the result from the step of controlling the electric driveline in response to the acceleration or deceleration control signal; comparing (S5) the resulting vehicle acceleration or deceleration with the corresponding acceleration or deceleration threshold limit and determining whether the resulting vehicle acceleration is or will be higher than the acceleration threshold limit or whether the resulting vehicle deceleration is or will be lower than the deceleration threshold limit; and when the resulting vehicle acceleration is or will be higher than the acceleration threshold limit or when the resulting vehicle deceleration is or will be lower than the deceleration threshold limit; applying (S6) the wheel brake system (5) so as to reduce an actual vehicle acceleration or increase an actual vehicle deceleration towards the corresponding acceleration or deceleration threshold limit.