Cruise Control Brake Coordination for Speed Overshoot Prevention
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Solution Overview
Problem
Existing brake cruise control systems for heavy vehicles with auxiliary brakes often experience speed overshoots when traveling downhill, leading to discomfort for the driver and increased fuel consumption, as the auxiliary brakes may not respond quickly enough to maintain the set brake cruise speed.
Innovation Solution
The system simultaneously activates the service brake when the auxiliary brake is engaged to instantaneously reduce vehicle acceleration and maintain the set brake cruise speed, minimizing wear on the service brake and ensuring the vehicle does not exceed the set speed during the response time of the auxiliary brake.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the auxiliary brake is used to maintain set brake cruise speed downhill, then fuel consumption is reduced and energy is preserved, but the response time delay causes speed overshoot beyond the allowed limit
Solution Approach 1:
The service brake is activated in advance simultaneously with the auxiliary brake when the vehicle reaches the set brake cruise speed. This preliminary action compensates for the auxiliary brake's response time delay, preventing speed overshoot while allowing the vehicle to maintain higher speeds downhill for fuel efficiency.
Solution Approach 2:
The braking function is divided into two separate brake systems: the auxiliary brake (engine brake or retarder) for primary speed maintenance and the service brake for immediate response during transitions. This segmentation allows each brake type to operate in its optimal performance range, with the service brake providing instant response and the auxiliary brake handling sustained braking.
2Reliability
If the set brake cruise speed is reduced to avoid speed overshoot, then speed control accuracy is improved, but fuel consumption increases and average vehicle speed decreases
Solution Approach 1:
Instead of reducing the set brake cruise speed, the system activates the service brake in advance when the vehicle reaches the desired speed. This preliminary braking action ensures accurate speed control while allowing the vehicle to maintain higher speeds for longer periods, improving fuel efficiency and average vehicle speed.
3Force
If the auxiliary brake response time is increased to provide sufficient brake power, then braking capability is improved, but the speed overshoot problem worsens
Solution Approach 1:
The braking system is segmented into two independent brake systems: the auxiliary brake optimized for high brake power with slower response, and the service brake optimized for fast response. The control system coordinates both brakes to work together, allowing the auxiliary brake to provide sufficient braking force while the service brake compensates for the response delay.
Solution Approach 2:
The control system merges the operation of two different brake systems (service brake and auxiliary brake) into a coordinated braking solution. Both brakes are activated simultaneously or in sequence to achieve the desired braking effect, combining the fast response of the service brake with the high brake power of the auxiliary brake.
Data Source
Figure 1
Figure 2
AI summary
A cruise control arrangement (1) for a vehicle (10), where the cruise control arrangement is provided with a cruise control brake function (3), where the cruise control brake function is set to a brake cruise speed, where the cruise control arrangement is adapted to activate at least one auxiliary brake (8, 9) when the vehicle speed reaches the set brake cruise speed, and at the same time to apply a service brake (5) of the vehicle to keep the speed of the vehicle at the set brake cruise speed, and further adapted to decrease the brake power of the service brake at the same time as the brake power of the at least one auxiliary brake increases, such that the speed of the vehicle is kept at the set brake cruise speed. The advantage of the invention is that the speed of the vehicle can be held at the set cruise speed when an auxiliary brake is activated, regardless of the activation time of the auxiliary brake. In this way, an overshoot in speed can be avoided during the activation time of the auxiliary brake.