Vehicle Braking Force Control with Integral Signal Holding
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Solution Overview
Problem
Existing automatic deceleration feedback control systems in vehicles, particularly those using PI controllers, experience significant deviations in braking force during skid control, leading to uncomfortable rapid changes in braking force when deceleration feedback control restarts, due to accumulated integral-control signals and prioritization of skid control over deceleration feedback.
Innovation Solution
An automatic braking force control apparatus that incorporates a deceleration detector, a braking force adjustment device, and a brake control unit with a desired deceleration calculation section, a desired braking force calculation section, an anti-skid control section, a desired braking force memorizing section, and a desired braking force initialization section, which calculates and adjusts braking forces using proportional and integral control signals to minimize deviations and maintain a consistent braking experience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If skid control is prioritized over deceleration feedback control during emergency braking, then wheel lock-up prevention is improved, but deceleration feedback control stability deteriorates due to interruption and accumulation of integral-control signals
Solution Approach 1:
The system performs preliminary action by detecting the start of skid control and holding the integral-control signal component at its value computed just before skid control begins. This preliminary holding action prevents the accumulation of erroneous integral signals during the skid control period, ensuring that when deceleration feedback control resumes, the integral component starts from a valid baseline rather than an accumulated error state.
Solution Approach 2:
The system uses feedback by continuously monitoring the operational state of skid control and dynamically adjusting the integral-control signal component accordingly. When skid control is detected, the feedback mechanism triggers the holding of the integral component; when skid control ends, the feedback restores normal integral accumulation. This closed-loop feedback ensures stable transition between control modes.
2Reliability
If integral control is used for deceleration feedback control, then disturbance stability is improved, but rapid change in braking force occurs upon restart due to accumulated integral-control signal
Solution Approach 1:
The system performs preliminary action by detecting the start of skid control and holding the integral-control signal component at its value computed just before skid control begins. This preliminary holding action prevents the accumulation of erroneous integral signals during the skid control period, ensuring that when deceleration feedback control resumes, the integral component starts from a valid baseline rather than an accumulated error state.
Solution Approach 2:
The system applies preliminary anti-action by counteracting the potential harmful effect of integral signal accumulation before it can occur. By holding the integral-control signal component constant from the moment skid control starts, the system preemptively prevents the buildup of excessive integral values that would otherwise cause abrupt braking force changes upon restart.
3Speed
If deceleration feedback control is interrupted during anti-skid cycle execution, then skid control responsiveness is improved, but braking force deviation from desired value increases
Solution Approach 1:
The system uses feedback by continuously monitoring the operational state of skid control and dynamically adjusting the integral-control signal component accordingly. When skid control is detected, the feedback mechanism triggers the holding of the integral component; when skid control ends, the feedback restores normal integral accumulation. This closed-loop feedback ensures stable transition between control modes.
Solution Approach 2:
The system performs preliminary action by detecting the start of skid control and holding the integral-control signal component at its value computed just before skid control begins. This preliminary holding action prevents the accumulation of erroneous integral signals during the skid control period, ensuring that when deceleration feedback control resumes, the integral component starts from a valid baseline rather than an accumulated error state.
Data Source
AI summary
In an automatic braking force control apparatus for a vehicle employing a deceleration feedback control system and an anti-skid control system executing, irrespective of a desired braking force for deceleration feedback control, an anti-skid cycle for preventing a wheel lock-up condition, the feedback control system calculates a desired braking force as a sum of a proportional-control signal component proportional to an error signal corresponding to a deviation from a desired deceleration, and an integral-control signal component corresponding to the integral of the error signal. The feedback control system memorizes the desired braking force, calculated just before an anti-skid cycle start time, as a memorized value, and initializes the desired braking force of an anti-skid cycle termination time to a predetermined value substantially corresponding to the memorized value for preventing a change in the desired deceleration occurring during the anti-skid cycle from being reflected in a feedback control signal.