Hybrid Work Machine Braking Controller Strategy
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Solution Overview
Problem
Hybrid work machines face challenges in managing braking priority effectively, particularly when multiple braking systems are engaged, leading to insufficient braking force in downhill conditions or when electrical energy exceeds storage capacity, potentially damaging components.
Innovation Solution
A system that includes an engine assembly, electric drive system, and a controller that selectively engages the engine, electric drive, and electro-hydraulic brake system to manage braking forces based on speed reduction commands, comparing required brake force to thresholds, and prioritizing engine and electric braking before engaging the drive mechanism, with the option to apply supplemental braking through an electro-hydraulic system when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the generator or motor-generator converts mechanical energy into electrical energy during braking, then electrical energy is stored in batteries, but if too much electrical energy is created, electronic brake resistors must be used to manage the excess energy
Solution Approach 1:
The controller continuously monitors the electrical energy generated during braking and adjusts the braking strategy accordingly. When battery charge capacity is sufficient, the system maximizes regenerative braking to store electrical energy. When the battery approaches full charge, the controller reduces regenerative braking and transitions to friction braking to prevent excess energy dissipation through brake resistors, optimizing energy management based on real-time battery status.
Solution Approach 2:
The braking system dynamically switches between regenerative braking and friction braking modes based on battery charge capacity. The controller adjusts the proportion of braking force from each system in real-time, transitioning smoothly between modes to maximize energy recovery when battery capacity allows and prevent energy waste when the battery is full, adapting the energy management strategy to current operating conditions.
2Force
If the brake system is engaged while the engine is defueled to facilitate slowing the work machine, then braking force is provided, but the braking force may be insufficient in downhill conditions
Solution Approach 1:
The system combines multiple braking mechanisms - engine braking (when the engine is defueled), regenerative braking (generator converting mechanical to electrical energy), and friction braking (electro-hydraulic brake system) - into a unified braking strategy. The controller coordinates these different braking sources to provide sufficient total braking force in all conditions, including downhill scenarios where enhanced braking is needed.
Solution Approach 2:
The braking system uses a composite approach combining different braking technologies with distinct characteristics. Engine braking provides baseline deceleration, regenerative braking adds controllable braking force while recovering energy, and friction braking provides supplemental force when needed. This composite braking system ensures reliable and sufficient braking performance across varying operating conditions.
3Speed
If the ground engaging mechanism causes the engine to rotate at higher speeds than designed to handle, then velocity reduction is achieved, but component damage may occur
Solution Approach 1:
The controller proactively engages the brake system before the engine speed reaches dangerous levels. By monitoring engine speed and vehicle velocity continuously, the system applies braking force in advance to prevent the engine from being forced to rotate at speeds exceeding its design limits, avoiding potential component damage while achieving the required velocity reduction.
Solution Approach 2:
The braking system applies counteracting force to prevent the harmful effect of excessive engine speed. When downhill conditions or other factors tend to accelerate the vehicle and force the engine beyond its safe operating range, the brake system engages to create opposing force that limits engine speed to safe levels, preventing damage before it can occur.
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
This solution ensures safe and efficient braking by optimizing the use of multiple braking systems, preventing component damage and maintaining control during varying conditions, such as downhill slopes or excessive electrical energy generation.
Implementation Method 1
the generator, or motor-generator, converting the mechanical energy generated by the work machine into electrical energy that can be stored or released by the work machine
Implementation Method 2
an electro-hydraulic brake system coupled to the drive mechanism, wherein the electro-hydraulic brake system is selectively applied by the controller to execute the braking function
Data Source
AI summary
A system for controlling the speed of a hybrid work machine that has an engine assembly, an electric drive system mechanically coupled to the engine assembly, a drive mechanism configured to be driven by the electric drive system, and a controller in communication with the engine assembly, the electric drive system, and the drive mechanism. Wherein, the controller selectively engages the engine assembly, the electric drive system, and the drive mechanism to execute a braking function.