Downslope Brake Control Using Transient Foundation Brake Profiling
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Solution Overview
Problem
Existing engine retarder systems in commercial vehicles exhibit a large response time delay, leading to undesirable kinetic energy waste and difficulty in controlling braking torque, while additional brakes like intarders increase fuel costs and vehicle weight.
Innovation Solution
A brake controller activates foundation brakes in a transient period with a specific profile, providing peak brake power followed by a gradual decrease to match engine retarder performance, avoiding the need for additional brakes and optimizing energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If engine retarder is activated, then braking power is generated, but response time delay occurs
Solution Approach 1:
The system performs preliminary actions by pre-positioning the exhaust valves and pre-charging hydraulic actuators before brake activation. The exhaust valves are held in a partially open position during cruising, and hydraulic pressure is maintained in the actuators, so that when the driver activates the engine brake, the system responds immediately without the typical several-second delay for pressure buildup and valve positioning.
Solution Approach 2:
The system dynamically adjusts exhaust valve lift and timing based on operating conditions. During compression braking, the exhaust valves are opened at optimized moments during the compression stroke, and the degree of opening is continuously adjusted to match driver demand and engine conditions, enabling rapid modulation of braking power without fixed mechanical delays.
2Power
If driver fully engages engine retarder to maximum position, then maximum braking torque is achieved, but kinetic energy waste occurs due to overshoot
Solution Approach 1:
The control system continuously monitors vehicle speed, engine parameters, and brake actuator position, using this feedback to adjust exhaust valve operation in real-time. When the vehicle approaches the desired speed or when maximum braking torque is achieved, the system automatically modulates the exhaust valve lift and timing to prevent overshoot, thereby conserving kinetic energy while maintaining precise speed control on downhill routes.
Solution Approach 2:
Instead of immediately applying full maximum braking torque when the driver activates the engine brake, the system initially applies a controlled partial braking action and gradually increases torque buildup based on the delayed compression brake response. This prevents excessive braking force that would cause overshoot and kinetic energy waste, while still achieving the desired speed control.
3Loss of time
If intarder brake is added to quicken response, then response time is reduced, but fuel costs and vehicle weight increase
Solution Approach 1:
The system makes the combustion engine multi-functional by enabling it to operate both as a power-producing engine during normal driving and as a power-absorbing compression brake during downhill braking. The same engine and its existing valve train mechanism serve dual purposes, eliminating the need for separate braking systems like intarders and thereby avoiding additional weight while achieving rapid braking response.
Solution Approach 2:
The engine brake system uses its own internal components (exhaust valves, hydraulic actuators, and compression mechanism) to generate braking power without requiring external braking hardware. The engine's natural compression process is harnessed and controlled through valve manipulation, making the system self-sufficient and avoiding the need for additional weight-bearing braking components.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system improves user comfort and energy efficiency by allowing precise control of braking torque, reducing the need for additional brakes and minimizing kinetic energy waste.
Implementation Method 1
high pressurized air from the exhaust manifold flows back into the cylinder which increases the initial pressure during compression by back gas recirculation
Implementation Method 2
convert, at least temporarily, a power producing internal combustion engine into a power absorbing air compressor
Implementation Method 3
Near the end of the compression stroke the exhaust valves are opened dissipating the energy instead of returning it to the drivetrain as positive power during the power stroke; this process is called compression release
Data Source
Figure 1A~1B
Figure 2A~2C
Figure 3A~3B
AI summary
In one aspect, it is aimed to provide a system of controlling a vehicle on a downslope route, the vehicle including a combustion engine provided with an engine retarder, and further comprising a brake controller programmed to: upon activating, by a driver, the engine retarder, activating, by the brake controller, of the foundation brake in a transient period having a foundation brake profile; wherein the foundation brake profile has a first initial phase with a peak brake power that lowers the speed of the vehicle on the downslope route, and wherein the foundation brake profile has a second phase that with a brake power lower than the peak brake power and that gradually decreases with a time constant about equal to the increase of engine retarder performance due to buildup of back pressure, to a steady state wherein the vehicle velocity is substantially constant with zero foundation brake power.